Large motor units are selectively affected following a stroke.

PubMed

Lukács, M; Vécsei, L; Beniczky, S

2008-11-01

Previous studies have revealed a loss of functioning motor units in stroke patients. However, it remained unclear whether the motor units are affected randomly or in some specific pattern. We assessed whether there is a selective loss of the large (high recruitment threshold) or the small (low recruitment threshold) motor units following a stroke. Forty-five stroke patients and 40 healthy controls participated in the study. Macro-EMG was recorded from the abductor digiti minimi muscle at two levels of force output (low and high). The median macro motor unit potential (macro-MUP) amplitude on the paretic side was compared with those on the unaffected side and in the controls. In the control group and on the unaffected side, the macro-MUPs were significantly larger at the high force output than at the low one. However, on the paretic side the macro-MUPs at the high force output had the same amplitude as those recorded at the low force output. These changes correlated with the severity of the paresis. Following a stroke, there is a selective functional loss of the large, high-threshold motor units. These changes are related to the severity of the symptoms. Our findings furnish further insight into the pathophysiology of the motor deficit following a stroke.

Neuromotor control in chronic obstructive pulmonary disease.

PubMed

Mantilla, Carlos B; Sieck, Gary C

2013-05-01

Neuromotor control of skeletal muscles, including respiratory muscles, is ultimately dependent on the structure and function of the motor units (motoneurons and the muscle fibers they innervate) comprising the muscle. In most muscles, considerable diversity of contractile and fatigue properties exists across motor units, allowing a range of motor behaviors. In diseases such as chronic obstructive pulmonary disease (COPD), there may be disproportional primary (disease related) or secondary effects (related to treatment or other concomitant factors) on the size and contractility of specific muscle fiber types that would influence the relative contribution of different motor units. For example, with COPD there is a disproportionate atrophy of type IIx and/or IIb fibers that comprise more fatigable motor units. Thus fatigue resistance may appear to improve, while overall motor performance (e.g., 6-min walk test) and endurance (e.g., reduced aerobic exercise capacity) are diminished. There are many coexisting factors that might also influence motor performance. For example, in COPD patients, there may be concomitant hypoxia and/or hypercapnia, physical inactivity and unloading of muscles, and corticosteroid treatment, all of which may disproportionately affect specific muscle fiber types, thereby influencing neuromotor control. Future studies should address how plasticity in motor units can be harnessed to mitigate the functional impact of COPD-induced changes.

Independence of motor unit recruitment and rate modulation during precision force control.

PubMed

Kamen, G; Du, D C

1999-01-01

The vertebrate motor system chiefly employs motor unit recruitment and rate coding to modulate muscle force output. In this paper, we studied how the recruitment of new motor units altered the firing rate of already-active motor units during precision force production in the first dorsal interosseous muscle. Six healthy adults performed linearly increasing isometric voluntary contractions while motor unit activity and force output were recorded. After motor unit discharges were identified, motor unit firing rates were calculated before and after the instances of new motor unit recruitment. Three procedures were applied to compute motor unit firing rate, including the mean of a fixed number of inter-spike intervals and the constant width weighted Hanning window filter method, as well as a modified boxcar technique. In contrast to previous reports, the analysis of the firing rates of over 200 motor units revealed that reduction of the active firing rates was not a common mechanism used to accommodate the twitch force produced by the recruitment of a new motor unit. Similarly, during de-recruitment there was no tendency for motor unit firing rates to increase immediately following the cessation of activity in other motor units. Considerable consistency in recruitment behavior was observed during repeated contractions. However, firing rates during repeated contractions demonstrated considerably more fluctuation. It is concluded that the neuromuscular system does not use short-term preferential motor unit disfacilitation to effect precise regulation of muscular force output.

Effect of pain on the modulation in discharge rate of sternocleidomastoid motor units with force direction.

PubMed

Falla, Deborah; Lindstrøm, Rene; Rechter, Lotte; Farina, Dario

2010-05-01

To compare the behavior of sternocleidomastoid motor units of patients with chronic neck pain and healthy controls. Nine women (age, 40.4+/-3.5 yr) with chronic neck pain and nine age- and gender-matched healthy controls participated. Surface and intramuscular EMG were recorded from the sternocleidomastoid muscle bilaterally as subjects performed isometric contractions of 10-s duration in the horizontal plane at a force of 15 N in eight directions (0-360 degrees ; 45 degrees intervals) and isometric contractions at 15 and 30 N force with continuous change in force direction in the range 0-360 degrees . Motor unit behavior was monitored during the 10-s contractions and the subsequent resting periods. The mean motor unit discharge rate depended on the direction of force in the control subjects (P<0.05) but not in the patients. Moreover, in three of the nine patients, but in none of the controls, single motor unit activity continued for 8.1+/-6.1s upon completion of the contraction. The surface EMG amplitude during the circular contraction at 15N was greater for the patients (43.5+/-54.2 microV) compared to controls (16.9+/-14.9 microV; P<0.05). The modulation in discharge rate of individual motor units with force direction is reduced in the sternocleidomastoid muscle in patients with neck pain, with some patients showing prolonged motor unit activity when they were instructed to rest. These observations suggest that chronic neck pain affects the change in neural drive to muscles with force direction. Copyright 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Role of motor unit structure in defining function

NASA Technical Reports Server (NTRS)

Monti, R. J.; Roy, R. R.; Edgerton, V. R.

2001-01-01

Motor units, defined as a motoneuron and all of its associated muscle fibers, are the basic functional units of skeletal muscle. Their activity represents the final output of the central nervous system, and their role in motor control has been widely studied. However, there has been relatively little work focused on the mechanical significance of recruiting variable numbers of motor units during different motor tasks. This review focuses on factors ranging from molecular to macroanatomical components that influence the mechanical output of a motor unit in the context of the whole muscle. These factors range from the mechanical properties of different muscle fiber types to the unique morphology of the muscle fibers constituting a motor unit of a given type and to the arrangement of those motor unit fibers in three dimensions within the muscle. We suggest that as a result of the integration of multiple levels of structural and physiological levels of organization, unique mechanical properties of motor units are likely to emerge. Copyright 2001 John Wiley & Sons, Inc.

Motor control for a brushless DC motor

NASA Technical Reports Server (NTRS)

Peterson, William J. (Inventor); Faulkner, Dennis T. (Inventor)

1985-01-01

This invention relates to a motor control system for a brushless DC motor having an inverter responsively coupled to the motor control system and in power transmitting relationship to the motor. The motor control system includes a motor rotor speed detecting unit that provides a pulsed waveform signal proportional to rotor speed. This pulsed waveform signal is delivered to the inverter to thereby cause an inverter fundamental current waveform output to the motor to be switched at a rate proportional to said rotor speed. In addition, the fundamental current waveform is also pulse width modulated at a rate proportional to the rotor speed. A fundamental current waveform phase advance circuit is controllingly coupled to the inverter. The phase advance circuit is coupled to receive the pulsed waveform signal from the motor rotor speed detecting unit and phase advance the pulsed waveform signal as a predetermined function of motor speed to thereby cause the fundamental current waveform to be advanced and thereby compensate for fundamental current waveform lag due to motor winding reactance which allows the motor to operate at higher speeds than the motor is rated while providing optimal torque and therefore increased efficiency.

Neural control of muscle force: indications from a simulation model

PubMed Central

Luca, Carlo J. De

2013-01-01

We developed a model to investigate the influence of the muscle force twitch on the simulated firing behavior of motoneurons and muscle force production during voluntary isometric contractions. The input consists of an excitatory signal common to all the motor units in the pool of a muscle, consistent with the “common drive” property. Motor units respond with a hierarchically structured firing behavior wherein at any time and force, firing rates are inversely proportional to recruitment threshold, as described by the “onion skin” property. Time- and force-dependent changes in muscle force production are introduced by varying the motor unit force twitches as a function of time or by varying the number of active motor units. A force feedback adjusts the input excitation, maintaining the simulated force at a target level. The simulations replicate motor unit behavior characteristics similar to those reported in previous empirical studies of sustained contractions: 1) the initial decrease and subsequent increase of firing rates, 2) the derecruitment and recruitment of motor units throughout sustained contractions, and 3) the continual increase in the force fluctuation caused by the progressive recruitment of larger motor units. The model cautions the use of motor unit behavior at recruitment and derecruitment without consideration of changes in the muscle force generation capacity. It describes an alternative mechanism for the reserve capacity of motor units to generate extraordinary force. It supports the hypothesis that the control of motoneurons remains invariant during force-varying and sustained isometric contractions. PMID:23236008

Single motor unit firing rate after stroke is higher on the less-affected side during stable low-level voluntary contractions

PubMed Central

McNulty, Penelope A.; Lin, Gaven; Doust, Catherine G.

2014-01-01

Muscle weakness is the most common outcome after stroke and a leading cause of adult-acquired motor disability. Single motor unit properties provide insight into the mechanisms of post-stroke motor impairment. Motor units on the more-affected side are reported to have lower peak firing rates, reduced discharge variability and a more compressed dynamic range than healthy subjects. The activity of 169 motor units was discriminated from surface electromyography in 28 stroke patients during sustained voluntary contractions 10% of maximal and compared to 110 units recorded in 16 healthy subjects. Motor units were recorded in three series: ankle dorsiflexion, wrist flexion and elbow flexion. Mean firing rates after stroke were significantly lower on the more-affected than the less-affected side (p < 0.001) with no differences between dominant and non-dominant sides for healthy subjects. When data were combined, firing rates on the less-affected side were significantly higher than those either on the more-affected side or healthy subjects (p < 0.001). Motor unit mean firing rate was higher in the upper-limb than the lower-limb (p < 0.05). The coefficient of variation of motor unit discharge rate was lower for motor units after stroke compared to controls for wrist flexion (p < 0.05) but not ankle dorsiflexion. However the dynamic range of motor units was compressed only for motor units on the more-affected side during wrist flexion. Our results show that the pathological change in motor unit firing rate occurs on the less-affected side after stroke and not the more-affected side as previously reported, and suggest that motor unit behavior recorded in a single muscle after stroke cannot be generalized to muscles acting on other joints even within the same limb. These data emphasize that the less-affected side does not provide a valid control for physiological studies on the more-affected side after stroke and that both sides should be compared to data from age- and sex-matched healthy subjects. PMID:25100969

Influence of prolonged static stretching on motor unit firing properties.

PubMed

Ye, Xin; Beck, Travis W; Wages, Nathan P

2016-05-01

The purpose of this study was to examine the influence of a stretching intervention on motor control strategy of the biceps brachii muscle. Ten men performed twelve 100-s passive static stretches of the biceps brachii. Before and after the intervention, isometric strength was tested during maximal voluntary contractions (MVCs) of the elbow flexors. Subjects also performed trapezoid isometric contractions at 30% and 70% of MVC. Surface electromyographic signals from the submaximal contractions were decomposed into individual motor unit action potential trains. Linear regression analysis was used to examine the relationship between motor unit mean firing rate and recruitment threshold. The stretching intervention caused significant decreases in y-intercepts of the linear regression lines. In addition, linear slopes at both intensities remained unchanged. Despite reduced motor unit firing rates following the stretches, the motor control scheme remained unchanged. © 2016 Wiley Periodicals, Inc.

Gestalt Principles in the Control of Motor Action

ERIC Educational Resources Information Center

Klapp, Stuart T.; Jagacinski, Richard J.

2011-01-01

We argue that 4 fundamental gestalt phenomena in perception apply to the control of motor action. First, a motor gestalt, like a perceptual gestalt, is holistic in the sense that it is processed as a single unit. This notion is consistent with reaction time results indicating that all gestures for a brief unit of action must be programmed prior to…

Speech motor development: Integrating muscles, movements, and linguistic units.

PubMed

Smith, Anne

2006-01-01

A fundamental problem for those interested in human communication is to determine how ideas and the various units of language structure are communicated through speaking. The physiological concepts involved in the control of muscle contraction and movement are theoretically distant from the processing levels and units postulated to exist in language production models. A review of the literature on adult speakers suggests that they engage complex, parallel processes involving many units, including sentence, phrase, syllable, and phoneme levels. Infants must develop multilayered interactions among language and motor systems. This discussion describes recent studies of speech motor performance relative to varying linguistic goals during the childhood, teenage, and young adult years. Studies of the developing interactions between speech motor and language systems reveal both qualitative and quantitative differences between the developing and the mature systems. These studies provide an experimental basis for a more comprehensive theoretical account of how mappings between units of language and units of action are formed and how they function. Readers will be able to: (1) understand the theoretical differences between models of speech motor control and models of language processing, as well as the nature of the concepts used in the two different kinds of models, (2) explain the concept of coarticulation and state why this phenomenon has confounded attempts to determine the role of linguistic units, such as syllables and phonemes, in speech production, (3) describe the development of speech motor performance skills and specify quantitative and qualitative differences between speech motor performance in children and adults, and (4) describe experimental methods that allow scientists to study speech and limb motor control, as well as compare units of action used to study non-speech and speech movements.

Phrenic Motor Unit Recruitment during Ventilatory and Non-Ventilatory Behaviors

PubMed Central

Mantilla, Carlos B.; Sieck, Gary C.

2011-01-01

Phrenic motoneurons are located in the cervical spinal cord and innervate the diaphragm muscle, the main inspiratory muscle in mammals. Similar to other skeletal muscles, phrenic motoneurons and diaphragm muscle fibers form motor units which are the final element of neuromotor control. In addition to their role in sustaining ventilation, phrenic motor units are active in other non-ventilatory behaviors important for airway clearance such as coughing or sneezing. Diaphragm muscle fibers comprise all fiber types and are commonly classified based on expression of contractile proteins including myosin heavy chain isoforms. Although there are differences in contractile and fatigue properties across motor units, there is a matching of properties for the motor neuron and muscle fibers within a motor unit. Motor units are generally recruited in order such that fatigue-resistant motor units are recruited earlier and more often than more fatigable motor units. Thus, in sustaining ventilation, fatigue-resistant motor units are likely required. Based on a series of studies in cats, hamsters and rats, an orderly model of motor unit recruitment was proposed that takes into consideration the maximum forces generated by single type-identified diaphragm muscle fibers as well as the proportion of the different motor unit types. Using this model, eupnea can be accomplished by activation of only slow-twitch diaphragm motor units and only a subset of fast-twitch, fatigue-resistant units. Activation of fast-twitch fatigable motor units only becomes necessary when accomplishing tasks that require greater force generation by the diaphragm muscle, e.g., sneezing and coughing. PMID:21763470

Phrenic motor unit recruitment during ventilatory and non-ventilatory behaviors.

PubMed

Mantilla, Carlos B; Sieck, Gary C

2011-10-15

Phrenic motoneurons are located in the cervical spinal cord and innervate the diaphragm muscle, the main inspiratory muscle in mammals. Similar to other skeletal muscles, phrenic motoneurons and diaphragm muscle fibers form motor units which are the final element of neuromotor control. In addition to their role in sustaining ventilation, phrenic motor units are active in other non-ventilatory behaviors important for airway clearance such as coughing or sneezing. Diaphragm muscle fibers comprise all fiber types and are commonly classified based on expression of contractile proteins including myosin heavy chain isoforms. Although there are differences in contractile and fatigue properties across motor units, there is a matching of properties for the motor neuron and muscle fibers within a motor unit. Motor units are generally recruited in order such that fatigue-resistant motor units are recruited earlier and more often than more fatigable motor units. Thus, in sustaining ventilation, fatigue-resistant motor units are likely required. Based on a series of studies in cats, hamsters and rats, an orderly model of motor unit recruitment was proposed that takes into consideration the maximum forces generated by single type-identified diaphragm muscle fibers as well as the proportion of the different motor unit types. Using this model, eupnea can be accomplished by activation of only slow-twitch diaphragm motor units and only a subset of fast-twitch, fatigue-resistant units. Activation of fast-twitch fatigable motor units only becomes necessary when accomplishing tasks that require greater force generation by the diaphragm muscle, e.g., sneezing and coughing. Copyright © 2011 Elsevier B.V. All rights reserved.

Task-Dependent Intermuscular Motor Unit Synchronization between Medial and Lateral Vastii Muscles during Dynamic and Isometric Squats.

PubMed

Mohr, Maurice; Nann, Marius; von Tscharner, Vinzenz; Eskofier, Bjoern; Nigg, Benno Maurus

2015-01-01

Motor unit activity is coordinated between many synergistic muscle pairs but the functional role of this coordination for the motor output is unclear. The purpose of this study was to investigate the short-term modality of coordinated motor unit activity-the synchronized discharge of individual motor units across muscles within time intervals of 5ms-for the Vastus Medialis (VM) and Lateralis (VL). Furthermore, we studied the task-dependency of intermuscular motor unit synchronization between VM and VL during static and dynamic squatting tasks to provide insight into its functional role. Sixteen healthy male and female participants completed four tasks: Bipedal squats, single-leg squats, an isometric squat, and single-leg balance. Monopolar surface electromyography (EMG) was used to record motor unit activity of VM and VL. For each task, intermuscular motor unit synchronization was determined using a coherence analysis between the raw EMG signals of VM and VL and compared to a reference coherence calculated from two desynchronized EMG signals. The time shift between VM and VL EMG signals was estimated according to the slope of the coherence phase angle spectrum. For all tasks, except for singe-leg balance, coherence between 15-80Hz significantly exceeded the reference. The corresponding time shift between VM and VL was estimated as 4ms. Coherence between 30-60Hz was highest for the bipedal squat, followed by the single-leg squat and the isometric squat. There is substantial short-term motor unit synchronization between VM and VL. Intermuscular motor unit synchronization is enhanced for contractions during dynamic activities, possibly to facilitate a more accurate control of the joint torque, and reduced during single-leg tasks that require balance control and thus, a more independent muscle function. It is proposed that the central nervous system scales the degree of intermuscular motor unit synchronization according to the requirements of the movement task at hand.

Task-Dependent Intermuscular Motor Unit Synchronization between Medial and Lateral Vastii Muscles during Dynamic and Isometric Squats

PubMed Central

Mohr, Maurice; Nann, Marius; von Tscharner, Vinzenz; Eskofier, Bjoern; Nigg, Benno Maurus

2015-01-01

Purpose Motor unit activity is coordinated between many synergistic muscle pairs but the functional role of this coordination for the motor output is unclear. The purpose of this study was to investigate the short-term modality of coordinated motor unit activity–the synchronized discharge of individual motor units across muscles within time intervals of 5ms–for the Vastus Medialis (VM) and Lateralis (VL). Furthermore, we studied the task-dependency of intermuscular motor unit synchronization between VM and VL during static and dynamic squatting tasks to provide insight into its functional role. Methods Sixteen healthy male and female participants completed four tasks: Bipedal squats, single-leg squats, an isometric squat, and single-leg balance. Monopolar surface electromyography (EMG) was used to record motor unit activity of VM and VL. For each task, intermuscular motor unit synchronization was determined using a coherence analysis between the raw EMG signals of VM and VL and compared to a reference coherence calculated from two desynchronized EMG signals. The time shift between VM and VL EMG signals was estimated according to the slope of the coherence phase angle spectrum. Results For all tasks, except for singe-leg balance, coherence between 15–80Hz significantly exceeded the reference. The corresponding time shift between VM and VL was estimated as 4ms. Coherence between 30–60Hz was highest for the bipedal squat, followed by the single-leg squat and the isometric squat. Conclusion There is substantial short-term motor unit synchronization between VM and VL. Intermuscular motor unit synchronization is enhanced for contractions during dynamic activities, possibly to facilitate a more accurate control of the joint torque, and reduced during single-leg tasks that require balance control and thus, a more independent muscle function. It is proposed that the central nervous system scales the degree of intermuscular motor unit synchronization according to the requirements of the movement task at hand. PMID:26529604

A modular robust control framework for control of movement elicited by multi-electrode intraspinal microstimulation

NASA Astrophysics Data System (ADS)

Roshani, Amir; Erfanian, Abbas

2016-08-01

Objective. An important issue in restoring motor function through intraspinal microstimulation (ISMS) is the motor control. To provide a physiologically plausible motor control using ISMS, it should be able to control the individual motor unit which is the lowest functional unit of motor control. By focal stimulation only a small group of motor neurons (MNs) within a motor pool can be activated. Different groups of MNs within a motor pool can potentially be activated without involving adjacent motor pools by local stimulation of different parts of a motor pool via microelectrode array implanted into a motor pool. However, since the system has multiple inputs with single output during multi-electrode ISMS, it poses a challenge to movement control. In this paper, we proposed a modular robust control strategy for movement control, whereas multi-electrode array is implanted into each motor activation pool of a muscle. Approach. The controller was based on the combination of proportional-integral-derivative and adaptive fuzzy sliding mode control. The global stability of the controller was guaranteed. Main results. The results of the experiments on rat models showed that the multi-electrode control can provide a more robust control and accurate tracking performance than a single-electrode control. The control output can be pulse amplitude (pulse amplitude modulation, PAM) or pulse width (pulse width modulation, PWM) of the stimulation signal. The results demonstrated that the controller with PAM provided faster convergence rate and better tracking performance than the controller with PWM. Significance. This work represents a promising control approach to the restoring motor functions using ISMS. The proposed controller requires no prior knowledge about the dynamics of the system to be controlled and no offline learning phase. The proposed control design is modular in the sense that each motor pool has an independent controller and each controller is able to control ISMS through an array of microelectrodes.

Effects of barbell deadlift training on submaximal motor unit firing rates for the vastus lateralis and rectus femoris.

PubMed

Stock, Matt S; Thompson, Brennan J

2014-01-01

Previous investigations that have studied motor unit firing rates following strength training have been limited to small muscles, isometric training, or interventions involving exercise machines. We examined the effects of ten weeks of supervised barbell deadlift training on motor unit firing rates for the vastus lateralis and rectus femoris during a 50% maximum voluntary contraction (MVC) assessment. Twenty-four previously untrained men (mean age  = 24 years) were randomly assigned to training (n = 15) or control (n = 9) groups. Before and following the intervention, the subjects performed isometric testing of the right knee extensors while bipolar surface electromyographic signals were detected from the two muscles. The signals were decomposed into their constituent motor unit action potential trains, and motor units that demonstrated accuracy levels less than 92.0% were not considered for analysis. One thousand eight hundred ninety-two and 2,013 motor units were examined for the vastus lateralis and rectus femoris, respectively. Regression analyses were used to determine the linear slope coefficients (pulses per second [pps]/% MVC) and y-intercepts (pps) of the mean firing rate and firing rate at recruitment versus recruitment threshold relationships. Deadlift training significantly improved knee extensor MVC force (Cohen's d = .70), but did not influence force steadiness. Training had no influence on the slopes and y-intercepts for the mean firing rate and firing rate at recruitment versus recruitment threshold relationships. In agreement with previous cross-sectional comparisons and randomized control trials, our findings do not support the notion that strength training affects the submaximal control of motor units.

Repeater F-waves are signs of motor unit pathology in polio survivors.

PubMed

Hachisuka, Akiko; Komori, Tetsuo; Abe, Tatsuya; Hachisuka, Kenji

2015-05-01

The purpose of this study was to determine whether F-waves reveal electrophysiological features of anterior horn cells in polio survivors. Forty-three polio survivors and 20 healthy controls underwent motor nerve conduction studies of the median and tibial nerves bilaterally, including sampling of F-waves elicited by 100 stimuli and the determination of motor unit number estimation (MUNE). A significant increase in abnormally stereotyped ("repeater") F-waves and a reduction of F-wave persistence were observed in both nerves in the polio group as compared with the control group. Repeater F-waves had a negative correlation with MUNE. These trends in F-wave persistence and repeater F-waves after motor unit loss are characteristic findings in polio survivors. Repeater F-waves are a sign of motor unit pathology. © 2014 The Authors. Muscle & Nerve Published by Wiley Periodicals, Inc.

Vibration influence on control of single motor unit activity.

PubMed

Malouin, F; Simard, T

1978-03-01

Effects of vibratory stimulation and maximal isometric contraction on a fine motor control task were evaluated in 17 human subjects. Electromyographic audiovisual feedback cues derived from two fine-wire bipolar electrodes, inserted to a depth of 12 and 6 mm respectively, were used to train the subjects to isolate a motor unit in the extensor carpi radialis brevis muscle. A specially designed compressed air driven vibrator providing vibratory stimulation with an amplitude of 2 mm and a frequency range of 120-160 cycles per second was applied to the muscle tendon. A significant decrease was found in the subjects; ability to isolate the pretest motor unit during and after continuous and interrupted periods of vibration and following a maximal isometric contraction of the extensor carpi radials brevis muscle. Individual variations in the subjects' responses to the forms of application of the vibratory stimulus, electrode preference and feedback specificity were observed. Results suggest that marked spatial recruitment of motor units, brought into action by the vibration stimulus or by the maximal isometric contraction, interfered with inhibitory mechanisms necessary to achieve isolation and control of a single motor unit. A therapeutic application of vibration, based on the marked spatial recruitment observed during and after vibration, is proposed for muscle reeducation.

Control system for several rotating mirror camera synchronization operation

NASA Astrophysics Data System (ADS)

Liu, Ningwen; Wu, Yunfeng; Tan, Xianxiang; Lai, Guoji

1997-05-01

This paper introduces a single chip microcomputer control system for synchronization operation of several rotating mirror high-speed cameras. The system consists of four parts: the microcomputer control unit (including the synchronization part and precise measurement part and the time delay part), the shutter control unit, the motor driving unit and the high voltage pulse generator unit. The control system has been used to control the synchronization working process of the GSI cameras (driven by a motor) and FJZ-250 rotating mirror cameras (driven by a gas driven turbine). We have obtained the films of the same objective from different directions in different speed or in same speed.

Similar alteration of motor unit recruitment strategies during the anticipation and experience of pain.

PubMed

Tucker, Kylie; Larsson, Anna-Karin; Oknelid, Stina; Hodges, Paul

2012-03-01

A motor unit consists of a motoneurone and the multiple muscle fibres that it innervates, and forms the final neural pathway that influences movement. Discharge of motor units is altered (decreased discharge rate and/or cessation of firing; and increased discharge rate and/or recruitment of new units) during matched-force contractions with pain. This is thought to be mediated by nociceptive (pain) input on motoneurones, as demonstrated in animal studies. It is also possible that motoneurone excitability is altered by pain related descending inputs, that these changes persist after noxious stimuli cease, and that direct nociceptive input is not necessary to induce pain related changes in movement. We aimed to determine whether anticipation of pain (descending pain related inputs without nociceptor discharge) alters motor unit discharge, and to observe motor unit discharge recovery after pain has ceased. Motor unit discharge was recorded with fine-wire electrodes in the quadriceps of 9 volunteers. Subjects matched isometric knee-extension force during anticipation of pain (anticipation: electrical shocks randomly applied over the infrapatellar fat-pad); pain (hypertonic saline injected into the fat-pad); and 3 intervening control conditions. Discharge rate of motor units decreased during pain (P<.001) and anticipation (P<.01) compared with control contractions. De-recruitment of 1 population of units and new recruitment of another population were observed during both anticipation and pain; some changes in motor unit recruitment persisted after pain ceased. This challenges the fundamental theory that pain-related changes in muscle activity result from direct nociceptor discharge, and provides a mechanism that may underlie long-term changes in movement/chronicity in some musculoskeletal conditions. Copyright © 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

A Simulation Based Analysis of Motor Unit Number Index (MUNIX) Technique Using Motoneuron Pool and Surface Electromyogram Models

PubMed Central

Li, Xiaoyan; Rymer, William Zev; Zhou, Ping

2013-01-01

Motor unit number index (MUNIX) measurement has recently achieved increasing attention as a tool to evaluate the progression of motoneuron diseases. In our current study, the sensitivity of the MUNIX technique to changes in motoneuron and muscle properties was explored by a simulation approach utilizing variations on published motoneuron pool and surface electromyogram (EMG) models. Our simulation results indicate that, when keeping motoneuron pool and muscle parameters unchanged and varying the input motor unit numbers to the model, then MUNIX estimates can appropriately characterize changes in motor unit numbers. Such MUNIX estimates are not sensitive to different motor unit recruitment and rate coding strategies used in the model. Furthermore, alterations in motor unit control properties do not have a significant effect on the MUNIX estimates. Neither adjustment of the motor unit recruitment range nor reduction of the motor unit firing rates jeopardizes the MUNIX estimates. The MUNIX estimates closely correlate with the maximum M wave amplitude. However, if we reduce the amplitude of each motor unit action potential rather than simply reduce motor unit number, then MUNIX estimates substantially underestimate the motor unit numbers in the muscle. These findings suggest that the current MUNIX definition is most suitable for motoneuron diseases that demonstrate secondary evidence of muscle fiber reinnervation. In this regard, when MUNIX is applied, it is of much importance to examine a parallel measurement of motor unit size index (MUSIX), defined as the ratio of the maximum M wave amplitude to the MUNIX. However, there are potential limitations in the application of the MUNIX methods in atrophied muscle, where it is unclear whether the atrophy is accompanied by loss of motor units or loss of muscle fiber size. PMID:22514208

Axonal loss in patients with inflammatory demyelinating polyneuropathy as determined by motor unit number estimation and MUNIX.

PubMed

Paramanathan, Sansuthan; Tankisi, Hatice; Andersen, Henning; Fuglsang-Frederiksen, Anders

2016-01-01

This study quantifies functioning axons and reinnervation by applying two methods multiple point stimulation (MPS) MUNE, and motor unit number index (MUNIX), in patients with acute- and chronic inflammatory demyelinating polyneuropathy (AIDP, CIDP). Nineteen patients with inflammatory demyelinating polyneuropathy (eleven AIDP and eight CIDP) were prospectively included. MPS MUNE and MUNIX examinations on the thenar muscle group by stimulating the median nerve were applied on all patients. Motor unit size was calculated as single motor unit potential (sMUP) and motor unit size index (MUSIX). The results were compared with twenty healthy subjects. In AIDP patients mean MPS MUNE (106) and MUNIX (80) were lower than control MPS MUNE (329) and MUNIX (215) (p<0.001). In CIDP patients both MPS MUNE (88) and MUNIX (67) were lower than controls (p<0.001). In CIDP patients sMUP (63) and MUSIX (90) were higher than control sMUP (35) and MUSIX (58) (p<0.05 and p<0.01). When AIDP and CIDP groups were combined the sensitivity for MPS MUNE and MUNIX were 89.5% and 68.4%, respectively. Decreased MPS MUNE and MUNIX suggest presence of axonal loss or loss of functioning axons in AIDP and CIDP. Increased motor unit size in CIDP patients indicates compensatory reinnervation. Moreover, both MPS MUNE and MUNIX can discriminate between disease versus non-disease. Estimation of the number and the average size of motor units may have clinical value for the assessment of axonal loss or loss of functioning axons in patients with AIDP and CIDP. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Effects of Barbell Deadlift Training on Submaximal Motor Unit Firing Rates for the Vastus Lateralis and Rectus Femoris

PubMed Central

Stock, Matt S.; Thompson, Brennan J.

2014-01-01

Previous investigations that have studied motor unit firing rates following strength training have been limited to small muscles, isometric training, or interventions involving exercise machines. We examined the effects of ten weeks of supervised barbell deadlift training on motor unit firing rates for the vastus lateralis and rectus femoris during a 50% maximum voluntary contraction (MVC) assessment. Twenty-four previously untrained men (mean age  = 24 years) were randomly assigned to training (n = 15) or control (n = 9) groups. Before and following the intervention, the subjects performed isometric testing of the right knee extensors while bipolar surface electromyographic signals were detected from the two muscles. The signals were decomposed into their constituent motor unit action potential trains, and motor units that demonstrated accuracy levels less than 92.0% were not considered for analysis. One thousand eight hundred ninety-two and 2,013 motor units were examined for the vastus lateralis and rectus femoris, respectively. Regression analyses were used to determine the linear slope coefficients (pulses per second [pps]/% MVC) and y-intercepts (pps) of the mean firing rate and firing rate at recruitment versus recruitment threshold relationships. Deadlift training significantly improved knee extensor MVC force (Cohen's d = .70), but did not influence force steadiness. Training had no influence on the slopes and y-intercepts for the mean firing rate and firing rate at recruitment versus recruitment threshold relationships. In agreement with previous cross-sectional comparisons and randomized control trials, our findings do not support the notion that strength training affects the submaximal control of motor units. PMID:25531294

Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals.

PubMed

Yang, Chia-Chi; Su, Fong-Chin; Yang, Po-Ching; Lin, Hwai-Ting; Guo, Lan-Yuen

2016-01-01

Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks.

Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals

PubMed Central

Yang, Chia-Chi; Su, Fong-Chin; Yang, Po-Ching; Lin, Hwai-Ting

2016-01-01

Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks. PMID:27941995

Brake blending strategy for a hybrid vehicle

DOEpatents

Boberg, Evan S.

2000-12-05

A hybrid electric powertrain system is provided including a transmission for driving a pair of wheels of a vehicle and a heat engine and an electric motor/generator coupled to the transmission. A friction brake system is provided for applying a braking torque to said vehicle. A controller unit generates control signals to the electric motor/generator and the friction brake system for controllably braking the vehicle in response to a drivers brake command. The controller unit determines and amount of regenerative torque available and compares this value to a determined amount of brake torque requested for determining the control signals to the electric motor/generator and the friction brake system.

78 FR 78294 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-26

... Control Unit--Constant Speed Motor/Generator (GCU-CSM/G) failed the operational test. Investigations... airplanes. This proposed AD was prompted by the failure of the generator control unit-constant speed motor... costing up to $17,314, for a cost of up to $17,399 per product. We have no way of determining the number...

Speed of the bacterial flagellar motor near zero load depends on the number of stator units.

PubMed

Nord, Ashley L; Sowa, Yoshiyuki; Steel, Bradley C; Lo, Chien-Jung; Berry, Richard M

2017-10-31

The bacterial flagellar motor (BFM) rotates hundreds of times per second to propel bacteria driven by an electrochemical ion gradient. The motor consists of a rotor 50 nm in diameter surrounded by up to 11 ion-conducting stator units, which exchange between motors and a membrane-bound pool. Measurements of the torque-speed relationship guide the development of models of the motor mechanism. In contrast to previous reports that speed near zero torque is independent of the number of stator units, we observe multiple speeds that we attribute to different numbers of units near zero torque in both Na + - and H + -driven motors. We measure the full torque-speed relationship of one and two H + units in Escherichia coli by selecting the number of H + units and controlling the number of Na + units in hybrid motors. These experiments confirm that speed near zero torque in H + -driven motors increases with the stator number. We also measured 75 torque-speed curves for Na + -driven chimeric motors at different ion-motive force and stator number. Torque and speed were proportional to ion-motive force and number of stator units at all loads, allowing all 77 measured torque-speed curves to be collapsed onto a single curve by simple rescaling. Published under the PNAS license.

Speed of the bacterial flagellar motor near zero load depends on the number of stator units

PubMed Central

Nord, Ashley L.; Sowa, Yoshiyuki; Steel, Bradley C.; Lo, Chien-Jung; Berry, Richard M.

2017-01-01

The bacterial flagellar motor (BFM) rotates hundreds of times per second to propel bacteria driven by an electrochemical ion gradient. The motor consists of a rotor 50 nm in diameter surrounded by up to 11 ion-conducting stator units, which exchange between motors and a membrane-bound pool. Measurements of the torque–speed relationship guide the development of models of the motor mechanism. In contrast to previous reports that speed near zero torque is independent of the number of stator units, we observe multiple speeds that we attribute to different numbers of units near zero torque in both Na+- and H+-driven motors. We measure the full torque–speed relationship of one and two H+ units in Escherichia coli by selecting the number of H+ units and controlling the number of Na+ units in hybrid motors. These experiments confirm that speed near zero torque in H+-driven motors increases with the stator number. We also measured 75 torque–speed curves for Na+-driven chimeric motors at different ion-motive force and stator number. Torque and speed were proportional to ion-motive force and number of stator units at all loads, allowing all 77 measured torque–speed curves to be collapsed onto a single curve by simple rescaling. PMID:29078322

A nerve stimulation method to selectively recruit smaller motor-units in rat skeletal muscle.

PubMed

van Bolhuis, A I; Holsheimer, J; Savelberg, H H

2001-05-30

Electrical stimulation of peripheral nerve results in a motor-unit recruitment order opposite to that attained by natural neural control, i.e. from large, fast-fatiguing to progressively smaller, fatigue-resistant motor-units. Yet animal studies involving physiological exercise protocols of low intensity and long duration require minimal fatigue. The present study sought to apply a nerve stimulation method to selectively recruit smaller motor-units in rat skeletal muscle. Two pulse generators were used, independently supplying short supramaximal cathodal stimulating pulses (0.5 ms) and long subthreshold cathodal inactivating pulses (1.5 s) to the sciatic nerve. Propagation of action potentials was selectively blocked in nerve fibres of different diameter by adjusting the strength of the inactivating current. A tensile-testing machine was used to gauge isometric muscle force of the plantaris and both heads of the gastrocnemius muscle. The order of motor-unit recruitment was estimated from twitch characteristics, i.e. peak force and relaxation time. The results showed prolonged relaxation at lower twitch peak forces as the intensity of the inactivating current increased, indicating a reduction of the number of large motor-units to force production. It is shown that the nerve stimulation method described is effective in mimicking physiological muscle control.

Microgravity induced changes in the control of motor units

NASA Astrophysics Data System (ADS)

de Luca, C.; Roy, S.

The goal of this project is to understand the effects of microgravity on the control of muscles. It is motivated by the notion that in order to adequately address microgravity-induced deterioration in the force generating capacity of muscles, one needs to understand the changes in the control aspects in addition to histochemical and morphological changes. The investigations into muscle control need to include the regulation of the firing activity of motor units that make up a muscle and the coordination of different muscles responsible for the control of a joint. In order to understand the effects of microgravity on these two aspects of muscle control, we will test astronauts before and after spaceflight. The investigations of the control of motor units will involve intramuscular EMG techniques developed in our laboratory. We will use a quadrifilar electrode to detect simultaneously three differential channels of EMG activity. These data will be decomposed accurately using a sophisticated set of algorithms constructed with artificial intelligence knowledge- based techniques. Particular attention will be paid to the firing rate and recruitment behavior of motor units and we will study the degree of cross-correlation of the firing rates. This approach will enable us to study the firing behavior of several (approx. 10) concurrently active motor units. This analysis will enable us to detect modifications in the control of motor units. We will perform these investigations in a hand muscle, which continues being used in prehensile tasks in space, and a leg muscle whose antigravity role is not needed in space. The comparison of the effects of weightlessness on these muscles will determine if continued use of muscles in space deters the possible deleterious effects of microgravity on the control of motor units, in addition to slowing down atrophy. We are particularly interested in comparing the results of this study to similar data already obtained from elderly subjects, because the deleterious effects of migrogravity on muscles is in many ways similar to that of aging. Additionally, we will employ surface EMG techniques to evaluate the effects of microgravity on the coordination of muscles controlling a joint. We will study if the relative contributions from the muscles around the knee joint are redistributed after exposure to microgravity. The insight to be gained from this study will be important in developing countermeasures for maintaining the force generating capacity of muscles in microgravity and rehabilitation programs for aiding in recovery upon return to earth.

Hybrid-fuel bacterial flagellar motors in Escherichia coli

PubMed Central

Sowa, Yoshiyuki; Homma, Michio; Ishijima, Akihiko; Berry, Richard M.

2014-01-01

The bacterial flagellar motor rotates driven by an electrochemical ion gradient across the cytoplasmic membrane, either H+ or Na+ ions. The motor consists of a rotor ∼50 nm in diameter surrounded by multiple torque-generating ion-conducting stator units. Stator units exchange spontaneously between the motor and a pool in the cytoplasmic membrane on a timescale of minutes, and their stability in the motor is dependent upon the ion gradient. We report a genetically engineered hybrid-fuel flagellar motor in Escherichia coli that contains both H+- and Na+-driven stator components and runs on both types of ion gradient. We controlled the number of each type of stator unit in the motor by protein expression levels and Na+ concentration ([Na+]), using speed changes of single motors driving 1-μm polystyrene beads to determine stator unit numbers. De-energized motors changed from locked to freely rotating on a timescale similar to that of spontaneous stator unit exchange. Hybrid motor speed is simply the sum of speeds attributable to individual stator units of each type. With Na+ and H+ stator components expressed at high and medium levels, respectively, Na+ stator units dominate at high [Na+] and are replaced by H+ units when Na+ is removed. Thus, competition between stator units for spaces in a motor and sensitivity of each type to its own ion gradient combine to allow hybrid motors to adapt to the prevailing ion gradient. We speculate that a similar process may occur in species that naturally express both H+ and Na+ stator components sharing a common rotor. PMID:24550452

Precision electronic speed controller for an alternating-current

DOEpatents

Bolie, Victor W.

1988-01-01

A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for and is particularly suitable for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. In the preferred embodiment, the motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of readonly memories, and a pair of digital-to-analog converters.

Self contained, independent, in-vacuum spinner motor

DOEpatents

Ayers, Marion J.

2002-01-01

An independent, self contained apparatus for operation within a vacuum chamber. A sealed enclosure is located in the chamber. The enclosure contains its own atmosphere independent of the vacuum in the chamber. A motor, power unit, and controls are located entirely within the enclosure. They do not have a direct structural connection outside of the enclosure in any way that would effect the atmosphere within the enclosure. The motor, power unit, and controls drive a spinner plate located outside the enclosure but within the vacuum chamber.

Mountain Plains Learning Experience Guide: Electric Motor Repair.

ERIC Educational Resources Information Center

Ziller, T.

This Electric Motor Repair Course is designed to provide the student with practical information for winding, repairing, and troubleshooting alternating current and direct current motors, and controllers. The course is comprised of eight units: (1) Electric Motor Fundamentals, (2) Rewinding, (3) Split-phase Induction Motors, (4) Capacitor Motors,…

In Vivo Imaging of Human Sarcomere Twitch Dynamics in Individual Motor Units.

PubMed

Sanchez, Gabriel N; Sinha, Supriyo; Liske, Holly; Chen, Xuefeng; Nguyen, Viet; Delp, Scott L; Schnitzer, Mark J

2015-12-16

Motor units comprise a pre-synaptic motor neuron and multiple post-synaptic muscle fibers. Many movement disorders disrupt motor unit contractile dynamics and the structure of sarcomeres, skeletal muscle's contractile units. Despite the motor unit's centrality to neuromuscular physiology, no extant technology can image sarcomere twitch dynamics in live humans. We created a wearable microscope equipped with a microendoscope for minimally invasive observation of sarcomere lengths and contractile dynamics in any major skeletal muscle. By electrically stimulating twitches via the microendoscope and visualizing the sarcomere displacements, we monitored single motor unit contractions in soleus and vastus lateralis muscles of healthy individuals. Control experiments verified that these evoked twitches involved neuromuscular transmission and faithfully reported muscle force generation. In post-stroke patients with spasticity of the biceps brachii, we found involuntary microscopic contractions and sarcomere length abnormalities. The wearable microscope facilitates exploration of many basic and disease-related neuromuscular phenomena never visualized before in live humans. Copyright © 2015 Elsevier Inc. All rights reserved.

Universal computer control system (UCCS) for space telerobots

NASA Technical Reports Server (NTRS)

Bejczy, Antal K.; Szakaly, Zoltan

1987-01-01

A universal computer control system (UCCS) is under development for all motor elements of a space telerobot. The basic hardware architecture and software design of UCCS are described, together with the rich motor sensing, control, and self-test capabilities of this all-computerized motor control system. UCCS is integrated into a multibus computer environment with direct interface to higher level control processors, uses pulsewidth multiplier power amplifiers, and one unit can control up to sixteen different motors simultaneously at a high I/O rate. UCCS performance capabilities are illustrated by a few data.

Motor unit recruitment and derecruitment induced by brief increase in contraction amplitude of the human trapezius muscle

PubMed Central

Westad, C; Westgaard, R H; De Luca, C J

2003-01-01

The activity pattern of low-threshold human trapezius motor units was examined in response to brief, voluntary increases in contraction amplitude (‘EMG pulse’) superimposed on a constant contraction at 4–7% of the surface electromyographic (EMG) response at maximal voluntary contraction (4–7% EMGmax). EMG pulses at 15–20% EMGmax were superimposed every minute on contractions of 5, 10, or 30 min duration. A quadrifilar fine-wire electrode recorded single motor unit activity and a surface electrode recorded simultaneously the surface EMG signal. Low-threshold motor units recruited at the start of the contraction were observed to stop firing while motor units of higher recruitment threshold stayed active. Derecruitment of a motor unit coincided with the end of an EMG pulse. The lowest-threshold motor units showed only brief silent periods. Some motor units with recruitment threshold up to 5% EMGmax higher than the constant contraction level were recruited during an EMG pulse and kept firing throughout the contraction. Following an EMG pulse, there was a marked reduction in motor unit firing rates upon return of the surface EMG signal to the constant contraction level, outlasting the EMG pulse by 4 s on average. The reduction in firing rates may serve as a trigger to induce derecruitment. We speculate that the silent periods following derecruitment may be due to deactivation of non-inactivating inward current (‘plateau potentials’). The firing behaviour of trapezius motor units in these experiments may thus illustrate a mechanism and a control strategy to reduce fatigue of motor units with sustained activity patterns. PMID:14561844

Disturbances of motor unit rate modulation are prevalent in muscles of spastic-paretic stroke survivors

PubMed Central

Heckman, C. J.; Powers, R. K.; Rymer, W. Z.; Suresh, N. L.

2014-01-01

Stroke survivors often exhibit abnormally low motor unit firing rates during voluntary muscle activation. Our purpose was to assess the prevalence of saturation in motor unit firing rates in the spastic-paretic biceps brachii muscle of stroke survivors. To achieve this objective, we recorded the incidence and duration of impaired lower- and higher-threshold motor unit firing rate modulation in spastic-paretic, contralateral, and healthy control muscle during increases in isometric force generated by the elbow flexor muscles. Impaired firing was considered to have occurred when firing rate became constant (i.e., saturated), despite increasing force. The duration of impaired firing rate modulation in the lower-threshold unit was longer for spastic-paretic (3.9 ± 2.2 s) than for contralateral (1.4 ± 0.9 s; P < 0.001) and control (1.1 ± 1.0 s; P = 0.005) muscles. The duration of impaired firing rate modulation in the higher-threshold unit was also longer for the spastic-paretic (1.7 ± 1.6 s) than contralateral (0.3 ± 0.3 s; P = 0.007) and control (0.1 ± 0.2 s; P = 0.009) muscles. This impaired firing rate of the lower-threshold unit arose, despite an increase in the overall descending command, as shown by the recruitment of the higher-threshold unit during the time that the lower-threshold unit was saturating, and by the continuous increase in averages of the rectified EMG of the biceps brachii muscle throughout the rising phase of the contraction. These results suggest that impairments in firing rate modulation are prevalent in motor units of spastic-paretic muscle, even when the overall descending command to the muscle is increasing. PMID:24572092

Precision electronic speed controller for an alternating-current motor

DOEpatents

Bolie, V.W.

A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. The motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The speed error signal is generated by a novel vernier-logic circuit which is drift-free and highly sensitive to small speed changes. The phase error is also computed by digital logic, with adjustable sensitivity around a 0 mid-scale value. The drift error signal, generated by long-term counting of the phase error, is used to compensate for any slow changes in the average friction drag on the motor. An auxillary drift-byte status sensor prevents any disruptive overflow or underflow of the drift-error counter. An adjustable clocked-delay unit is inserted between the controller and the source of the reference pulse train to permit phase alignment of the rotor to any desired offset angle. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of read-only memories, and a pair of digital-to-analog converters.

Preferential distribution of nociceptive input to motoneurons with muscle units in the cranial portion of the upper trapezius muscle.

PubMed

Dideriksen, Jakob L; Holobar, Ales; Falla, Deborah

2016-08-01

Pain is associated with changes in the neural drive to muscles. For the upper trapezius muscle, surface electromyography (EMG) recordings have indicated that acute noxious stimulation in either the cranial or the caudal region of the muscle leads to a relative decrease in muscle activity in the cranial region. It is, however, not known if this adaption reflects different recruitment thresholds of the upper trapezius motor units in the cranial and caudal region or a nonuniform nociceptive input to the motor units of both regions. This study investigated these potential mechanisms by direct motor unit identification. Motor unit activity was investigated with high-density surface EMG signals recorded from the upper trapezius muscle of 12 healthy volunteers during baseline, control (intramuscular injection of isotonic saline), and painful (hypertonic saline) conditions. The EMG was decomposed into individual motor unit spike trains. Motor unit discharge rates decreased significantly from control to pain conditions by 4.0 ± 3.6 pulses/s (pps) in the cranial region but not in the caudal region (1.4 ± 2.8 pps; not significant). These changes were compatible with variations in the synaptic input to the motoneurons of the two regions. These adjustments were observed, irrespective of the location of noxious stimulation. These results strongly indicate that the nociceptive synaptic input is distributed in a nonuniform way across regions of the upper trapezius muscle. Copyright © 2016 the American Physiological Society.

Preferential distribution of nociceptive input to motoneurons with muscle units in the cranial portion of the upper trapezius muscle

PubMed Central

Dideriksen, Jakob L.; Holobar, Ales

2016-01-01

Pain is associated with changes in the neural drive to muscles. For the upper trapezius muscle, surface electromyography (EMG) recordings have indicated that acute noxious stimulation in either the cranial or the caudal region of the muscle leads to a relative decrease in muscle activity in the cranial region. It is, however, not known if this adaption reflects different recruitment thresholds of the upper trapezius motor units in the cranial and caudal region or a nonuniform nociceptive input to the motor units of both regions. This study investigated these potential mechanisms by direct motor unit identification. Motor unit activity was investigated with high-density surface EMG signals recorded from the upper trapezius muscle of 12 healthy volunteers during baseline, control (intramuscular injection of isotonic saline), and painful (hypertonic saline) conditions. The EMG was decomposed into individual motor unit spike trains. Motor unit discharge rates decreased significantly from control to pain conditions by 4.0 ± 3.6 pulses/s (pps) in the cranial region but not in the caudal region (1.4 ± 2.8 pps; not significant). These changes were compatible with variations in the synaptic input to the motoneurons of the two regions. These adjustments were observed, irrespective of the location of noxious stimulation. These results strongly indicate that the nociceptive synaptic input is distributed in a nonuniform way across regions of the upper trapezius muscle. PMID:27226455

Motor unit behaviour and contractile changes during fatigue in the human first dorsal interosseus

PubMed Central

Carpentier, Alain; Duchateau, Jacques; Hainaut, Karl

2001-01-01

In 67 single motor units, the mechanical properties, the recruitment and derecruitment thresholds, and the discharge rates were recorded concurrently in the first dorsal interosseus (FDI) of human subjects during intermittent fatiguing contractions. The task consisted of isometric ramp-and-hold contractions performed at 50% of the maximal voluntary contraction (MVC). The purpose of this study was to examine the influence of fatigue on the behaviour of motor units with a wide range of activation thresholds. For low-threshold (< 25% MVC) motor units, the mean twitch force increased with fatigue and the recruitment threshold either did not change or increased. In contrast, the twitch force and the activation threshold decreased for the high-threshold (> 25% MVC) units. The observation that in low-threshold motor units a quick stretch of the muscle at the end of the test reset the unit force and recruitment threshold to the prefatigue value suggests a significant role for fatigue-related changes in muscle stiffness but not twitch potentiation or motor unit synchronization. Although the central drive intensified during the fatigue test, as indicated by an increase in surface electromyogram (EMG), the discharge rate of the motor units during the hold phase of each contraction decreased progressively over the course of the task for motor units that were recruited at the beginning of the test, especially the low-threshold units. In contrast, the discharge rates of newly activated units first increased and then decreased. Such divergent behaviour of low- and high-threshold motor units could not be individually controlled by the central drive to the motoneurone pool. Rather, the different behaviours must be the consequence of variable contributions from motoneurone adaptation and afferent feedback from the muscle during the fatiguing contraction. PMID:11483719

In Vivo Imaging of Human Sarcomere Twitch Dynamics in Individual Motor Units

PubMed Central

Sanchez, Gabriel N.; Sinha, Supriyo; Liske, Holly; Chen, Xuefeng; Nguyen, Viet; Delp, Scott L.; Schnitzer, Mark J.

2017-01-01

SUMMARY Motor units comprise a pre-synaptic motor neuron and multiple post-synaptic muscle fibers. Many movement disorders disrupt motor unit contractile dynamics and the structure of sarcomeres, skeletal muscle’s contractile units. Despite the motor unit’s centrality to neuromuscular physiology, no extant technology can image sarcomere twitch dynamics in live humans. We created a wearable microscope equipped with a microendoscope for minimally invasive observation of sarcomere lengths and contractile dynamics in any major skeletal muscle. By electrically stimulating twitches via the microendoscope and visualizing the sarcomere displacements, we monitored single motor unit contractions in soleus and vastus lateralis muscles of healthy individuals. Control experiments verified that these evoked twitches involved neuromuscular transmission and faithfully reported muscle force generation. In post-stroke patients with spasticity of the biceps brachii, we found involuntary microscopic contractions and sarcomere length abnormalities. The wearable microscope facilitates exploration of many basic and disease-related neuromuscular phenomena never visualized before in live humans. PMID:26687220

Detail of field breakers in the motor control cabinet for ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of field breakers in the motor control cabinet for unit 3. Control cabinet and breaker panel built by Cutler-Hammer - Wellton-Mohawk Irrigation System, Pumping Plant No. 1, Bounded by Gila River & Union Pacific Railroad, Wellton, Yuma County, AZ

Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly.

PubMed

Chen, Yi-Ching; Lin, Linda L; Lin, Yen-Ting; Hu, Chia-Ling; Hwang, Ing-Shiou

2017-01-01

Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations [Formula: see text], short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13-35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization.

Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly

PubMed Central

Chen, Yi-Ching; Lin, Linda L.; Lin, Yen-Ting; Hu, Chia-Ling; Hwang, Ing-Shiou

2017-01-01

Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations <ΔFc2>, short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13–35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization. PMID:29167637

Hip position and sex differences in motor unit firing patterns of the vastus medialis and vastus medialis oblique in healthy individuals.

PubMed

Peng, Yi-Ling; Tenan, Matthew S; Griffin, Lisa

2018-06-01

Weakness of the vastus medialis oblique (VMO) has been proposed to explain the high prevalence of knee pain in female subjects. Clinicians commonly use exercises in an attempt to preferentially activate the VMO. Recently, our group found evidence to support clinical theory that the VMO is neurologically distinct from the vastus medialis (VM). However, the ability to voluntarily activate these muscle subsections is still disputed. The aim of this study was to determine if VM and VMO activation varies between sexes and if control of the two muscles is different between rehabilitation exercises. Thirteen men and 13 women performed isometric straight leg raises in two hip positions, neutral hip rotation and 30 degrees lateral hip rotation. Bipolar intramuscular fine-wire electrodes were inserted into the VM and VMO to obtain motor unit recruitment thresholds and initial firing rates at recruitment. Linear mixed models and Tukey post hoc tests were used to assess significant differences in 654 motor units. Women demonstrated faster motor unit firing rate at recruitment, 1.18 ± 0.56 Hz higher than men. Motor units fired 0.47 ± 0.19 Hz faster during neutral hip rotation compared with lateral hip rotation. The VMO motor units were recruited 2.92 ± 1.28% earlier than the VM. All motor units were recruited 3.74 ± 1.27% earlier during neutral hip rotation than lateral hip rotation. Thus the VM and the VMO can be activated differentially, and their motor unit recruitment properties are affected by sex and hip position. NEW & NOTEWORTHY This is the first study to reveal differential activation of the vastus medialis oblique from the vastus medialis in clinical exercise protocols. Our research group used fine-wire electrodes to examine EMG signals of the vastus medialis oblique and vastus medialis to avoid possible cross talk. We also consider the effect of sex on motor unit firing patterns because of higher prevalence of knee pain in women, and yet few studies evaluating the sex differences in neuromuscular control.

Strength training, but not endurance training, reduces motor unit discharge rate variability.

PubMed

Vila-Chã, Carolina; Falla, Deborah

2016-02-01

This study evaluates and compares the effects of strength and endurance training on motor unit discharge rate variability and force steadiness of knee extensor muscles. Thirty sedentary healthy men (age, 26.0±3.8yrs) were randomly assigned to strength training, endurance training or a control group. Conventional endurance and strength training was performed 3days per week, over a period of 6weeks. Maximum voluntary contraction (MVC), time to task failure (at 30% MVC), coefficient of variation (CoV) of force and of the discharges rates of motor units from the vastus medialis obliquus and vastus lateralis were determined as subjects performed 20% and 30% MVC knee extension contractions before and after training. CoV of motor unit discharges rates was significantly reduced for both muscles following strength training (P<0.001), but did not change in the endurance (P=0.875) or control group (P=0.995). CoV of force was reduced after the strength training intervention only (P<0.01). Strength training, but not endurance training, reduces motor unit discharge rate variability and enhances force steadiness of the knee extensors. These results provide new insights into the neuromuscular adaptations that occur with different training methods. Copyright © 2015 Elsevier Ltd. All rights reserved.

Firing rate modulation of human motor units in different muscles during isometric contraction with various forces.

PubMed

Seki, K; Narusawa, M

1996-05-06

To examine the factors affecting the control of human motor units, rate coding strategies of the motor units were investigated in upper limb and intrinsic hand muscles during voluntary isometric contraction of steady force levels up to 80% of maximal voluntary contraction. Numerous spike trains from single motor units were recorded from the m. first dorsal interosseous (FDI) and the m. biceps brachii (BB) of eight human subjects by means of tungsten micro-electrodes, and the mean firing rate (MFR) was calculated for each subject and inter-individual comparisons made. The MFRs of the FDI were larger than that of the BB at the higher force level, and substantial differences were not found between these muscles at the lower force level. The slope of the linear regression line of MFRs vs. exerted forces for the FDI was more than twice that for the BB. Therefore, isometric force control of the FDI depends more on the rate coding strategy. The difference in rate coding between the FDI and BB motor units may be determined by factors other than muscle fiber composition, because both muscles are known to possess a similar composition of fiber types. Possible mechanisms underlying these characteristics of rate coding strategy are considered in this report.

Design of a robotic vehicle with self-contained intelligent wheels

NASA Astrophysics Data System (ADS)

Poulson, Eric A.; Jacob, John S.; Gunderson, Robert W.; Abbott, Ben A.

1998-08-01

The Center for Intelligent Systems has developed a small robotic vehicle named the Advanced Rover Chassis 3 (ARC 3) with six identical intelligent wheel units attached to a payload via a passive linkage suspension system. All wheels are steerable, so the ARC 3 can move in any direction while rotating at any rate allowed by the terrain and motors. Each intelligent wheel unit contains a drive motor, steering motor, batteries, and computer. All wheel units are identical, so manufacturing, programing, and spare replacement are greatly simplified. The intelligent wheel concept would allow the number and placement of wheels on the vehicle to be changed with no changes to the control system, except to list the position of all the wheels relative to the vehicle center. The task of controlling the ARC 3 is distributed between one master computer and the wheel computers. Tasks such as controlling the steering motors and calculating the speed of each wheel relative to the vehicle speed in a corner are dependent on the location of a wheel relative to the vehicle center and ar processed by the wheel computers. Conflicts between the wheels are eliminated by computing the vehicle velocity control in the master computer. Various approaches to this distributed control problem, and various low level control methods, have been explored.

Examination of Poststroke Alteration in Motor Unit Firing Behavior Using High-Density Surface EMG Decomposition.

PubMed

Li, Xiaoyan; Holobar, Ales; Gazzoni, Marco; Merletti, Roberto; Rymer, William Zev; Zhou, Ping

2015-05-01

Recent advances in high-density surface electromyogram (EMG) decomposition have made it a feasible task to discriminate single motor unit activity from surface EMG interference patterns, thus providing a noninvasive approach for examination of motor unit control properties. In the current study, we applied high-density surface EMG recording and decomposition techniques to assess motor unit firing behavior alterations poststroke. Surface EMG signals were collected using a 64-channel 2-D electrode array from the paretic and contralateral first dorsal interosseous (FDI) muscles of nine hemiparetic stroke subjects at different isometric discrete contraction levels between 2 to 10 N with a 2 N increment step. Motor unit firing rates were extracted through decomposition of the high-density surface EMG signals and compared between paretic and contralateral muscles. Across the nine tested subjects, paretic FDI muscles showed decreased motor unit firing rates compared with contralateral muscles at different contraction levels. Regression analysis indicated a linear relation between the mean motor unit firing rate and the muscle contraction level for both paretic and contralateral muscles (p < 0.001), with the former demonstrating a lower increment rate (0.32 pulses per second (pps)/N) compared with the latter (0.67 pps/N). The coefficient of variation (averaged over the contraction levels) of the motor unit firing rates for the paretic muscles (0.21 ± 0.012) was significantly higher than for the contralateral muscles (0.17 ± 0.014) (p < 0.05). This study provides direct evidence of motor unit firing behavior alterations poststroke using surface EMG, which can be an important factor contributing to hemiparetic muscle weakness.

Examination of Post-stroke Alteration in Motor Unit Firing Behavior Using High Density Surface EMG Decomposition

PubMed Central

Li, Xiaoyan; Holobar, Aleš; Gazzoni, Marco; Merletti, Roberto; Rymer, William Z.; Zhou, Ping

2014-01-01

Recent advances in high density surface electromyogram (EMG) decomposition have made it a feasible task to discriminate single motor unit activity from surface EMG interference patterns, thus providing a noninvasive approach for examination of motor unit control properties. In the current study we applied high density surface EMG recording and decomposition techniques to assess motor unit firing behavior alterations post-stroke. Surface EMG signals were collected using a 64-channel 2-dimensional electrode array from the paretic and contralateral first dorsal interosseous (FDI) muscles of nine hemiparetic stroke subjects at different isometric discrete contraction levels between 2 N to 10 N with a 2 N increment step. Motor unit firing rates were extracted through decomposition of the high density surface EMG signals, and compared between paretic and contralateral muscles. Across the nine tested subjects, paretic FDI muscles showed decreased motor unit firing rates compared with contralateral muscles at different contraction levels. Regression analysis indicated a linear relation between the mean motor unit firing rate and the muscle contraction level for both paretic and contralateral muscles (p < 0.001), with the former demonstrating a lower increment rate (0.32 pulses per second (pps)/N) compared with the latter (0.67 pps/N). The coefficient of variation (CoV, averaged over the contraction levels) of the motor unit firing rates for the paretic muscles (0.21 ± 0.012) was significantly higher than for the contralateral muscles (0.17 ± 0.014) (p < 0.05). This study provides direct evidence of motor unit firing behavior alterations post-stroke using surface EMG, which can be an important factor contributing to hemiparetic muscle weakness. PMID:25389239

Recruitment order of motor units in human vastus lateralis muscle is maintained during fatiguing contractions.

PubMed

Adam, Alexander; De Luca, Carlo J

2003-11-01

Motor-unit firing patterns were studied in the vastus lateralis muscle of five healthy young men [21.4 +/- 0.9 (SD) yr] during a series of isometric knee extensions performed to exhaustion. Each contraction was held at a constant torque level, set to 20% of the maximal voluntary contraction at the beginning of the experiment. Electromyographic signals, recorded via a quadrifilar fine wire electrode, were processed with the precision decomposition technique to identify the firing times of individual motor units. In repeat experiments, whole-muscle mechanical properties were measured during the fatigue protocol using electrical stimulation. The main findings were a monotonic decrease in the recruitment threshold of all motor units and the progressive recruitment of new units, all without a change of the recruitment order. Motor units from the same subject showed a similar time course of threshold decline, but this decline varied among subjects (mean threshold decrease ranged from 23 to 73%). The mean threshold decline was linearly correlated (R2 >or= 0.96) with a decline in the elicited peak tetanic torque. In summary, the maintenance of recruitment order during fatigue strongly supports the notion that the observed common recruitment adaptations were a direct consequence of an increased excitatory drive to the motor unit pool. It is suggested that the increased central drive was necessary to compensate for the loss in force output from motor units whose muscle fibers were actively contracting. We therefore conclude that the control scheme of motor-unit recruitment remains invariant during fatigue at least in relatively large muscles performing submaximal isometric contractions.

The (un)coupling between action execution and observation. Comment on "Grasping synergies: A motor-control approach to the mirror neuron mechanism" by D'Ausilio, Bartoli and Maffongelli

NASA Astrophysics Data System (ADS)

Cavallo, Andrea; Ansuini, Caterina; Becchio, Cristina

2015-03-01

When we observe actions performed by others, our motor system resonates along with that of the observed agent [1]. The exact features of this resonant motor response, however, are unclear. Do we mirror the goal of others' actions or rather the low-kinematic features of their movements? D'Ausilio et al. suggest that this is an ill-defined problem: the mirror system plausibly replicates the same computational mechanisms implicated by motor control. Accordingly, motor synergies may not only constitute a pervasive element of motor control, but also form the fundamental unit of action observation.

Cost Performance Estimating Relationships for Hybrid Electric Vehicle Components

DTIC Science & Technology

2003-07-31

Permanent magnet motors are more likely to be used as generators, while AC induction motors are more efficiently used as motors. Inverters/controllers can...than permanent magnet motors . Switched Reluctance motors are also used on hybrid electric vehicles, but are not used as widely as either AC...induction or permanent magnet motors , and are not analyzed here. Methodology The motor estimates are based on power, with kilowatts being the unit of

Reciprocal inhibition between motor neurons of the tibialis anterior and triceps surae in humans.

PubMed

Yavuz, Utku Ş; Negro, Francesco; Diedrichs, Robin; Farina, Dario

2018-05-01

Motor neurons innervating antagonist muscles receive reciprocal inhibitory afferent inputs to facilitate the joint movement in the two directions. The present study investigates the mutual transmission of reciprocal inhibitory afferent inputs between the tibialis anterior (TA) and triceps surae (soleus and medial gastrocnemius) motor units. We assessed this mutual mechanism in large populations of motor units for building a statistical distribution of the inhibition amplitudes during standardized input to the motor neuron pools to minimize the effect of modulatory pathways. Single motor unit activities were identified using high-density surface electromyography (HDsEMG) recorded from the TA, soleus (Sol), and medial gastrocnemius (GM) muscles during isometric dorsi- and plantarflexion. Reciprocal inhibition on the antagonist muscle was elicited by electrical stimulation of the tibial (TN) or common peroneal nerves (CPN). The probability density distributions of reflex strength for each muscle were estimated to examine the strength of mutual transmission of reciprocal inhibitory input. The results showed that the strength of reciprocal inhibition in the TA motor units was fourfold greater than for the GM and the Sol motor units. This suggests an asymmetric transmission of reciprocal inhibition between ankle extensor and flexor muscles. This asymmetry cannot be explained by differences in motor unit type composition between the investigated muscles since we sampled low-threshold motor units in all cases. Therefore, the differences observed for the strength of inhibition are presumably due to a differential reciprocal spindle afferent input and the relative contribution of nonreciprocal inhibitory pathways. NEW & NOTEWORTHY We investigated the mutual transmission of reciprocal inhibition in large samples of motor units using a standardized input (electrical stimulation) to the motor neurons. The results demonstrated that the disynaptic reciprocal inhibition exerted between ankle flexor and extensor muscles is asymmetric. The functional implication of asymmetric transmission may be associated with the neural strategies of postural control.

ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. D-C MAGNETIC MOTOR CONTROL, UNIT 7, ASSIGNMENTS.

ERIC Educational Resources Information Center

SUTTON, MACK C.

THIS GUIDE IS FOR INDIVIDUAL STUDENT USE IN STUDYING DIRECT CURRENT MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 15 ASSIGNMENT SHEETS PROVIDES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, STUDY REFERENCES, AND PROBLEMS. SOME OF THE LESSONS…

ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. A-C CONVENTIONAL MAGNETIC MOTOR CONTROL, PART I, UNIT 5, ASSIGNMENTS.

ERIC Educational Resources Information Center

SUTTON, MACK C.

THIS GUIDE IS FOR INDIVIDUAL STUDENT USE IN STUDYING ALTERNATING CURRENT CONVENTIONAL MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 10 ASSIGNMENT SHEETS PROVIDES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, STUDY REFERENCES, SUPPLEMENTARY…

An Efficient Fuzzy Controller Design for Parallel Connected Induction Motor Drives

NASA Astrophysics Data System (ADS)

Usha, S.; Subramani, C.

2018-04-01

Generally, an induction motors are highly non-linear and has a complex time varying dynamics. This makes the speed control of an induction motor a challenging issue in the industries. But, due to the recent trends in the power electronic devices and intelligent controllers, the speed control of the induction motor is achieved by including non-linear characteristics also. Conventionally a single inverter is used to run one induction motor in industries. In the traction applications, two or more inductions motors are operated in parallel to reduce the size and cost of induction motors. In this application, the parallel connected induction motors can be driven by a single inverter unit. The stability problems may introduce in the parallel operation under low speed operating conditions. Hence, the speed deviations should be reduce with help of suitable controllers. The speed control of the parallel connected system is performed by PID controller and fuzzy logic controller. In this paper the speed response of the induction motor for the rating of IHP, 1440 rpm, and 50Hz with these controller are compared in time domain specifications. The stability analysis of the system also performed under low speed using matlab platform. The hardware model is developed for speed control using fuzzy logic controller which exhibited superior performances over the other controller.

PyMUS: Python-Based Simulation Software for Virtual Experiments on Motor Unit System

PubMed Central

Kim, Hojeong; Kim, Minjung

2018-01-01

We constructed a physiologically plausible computationally efficient model of a motor unit and developed simulation software that allows for integrative investigations of the input–output processing in the motor unit system. The model motor unit was first built by coupling the motoneuron model and muscle unit model to a simplified axon model. To build the motoneuron model, we used a recently reported two-compartment modeling approach that accurately captures the key cell-type-related electrical properties under both passive conditions (somatic input resistance, membrane time constant, and signal attenuation properties between the soma and the dendrites) and active conditions (rheobase current and afterhyperpolarization duration at the soma and plateau behavior at the dendrites). To construct the muscle unit, we used a recently developed muscle modeling approach that reflects the experimentally identified dependencies of muscle activation dynamics on isometric, isokinetic and dynamic variation in muscle length over a full range of stimulation frequencies. Then, we designed the simulation software based on the object-oriented programing paradigm and developed the software using open-source Python language to be fully operational using graphical user interfaces. Using the developed software, separate simulations could be performed for a single motoneuron, muscle unit and motor unit under a wide range of experimental input protocols, and a hierarchical analysis could be performed from a single channel to the entire system behavior. Our model motor unit and simulation software may represent efficient tools not only for researchers studying the neural control of force production from a cellular perspective but also for instructors and students in motor physiology classroom settings. PMID:29695959

PyMUS: Python-Based Simulation Software for Virtual Experiments on Motor Unit System.

PubMed

Kim, Hojeong; Kim, Minjung

2018-01-01

We constructed a physiologically plausible computationally efficient model of a motor unit and developed simulation software that allows for integrative investigations of the input-output processing in the motor unit system. The model motor unit was first built by coupling the motoneuron model and muscle unit model to a simplified axon model. To build the motoneuron model, we used a recently reported two-compartment modeling approach that accurately captures the key cell-type-related electrical properties under both passive conditions (somatic input resistance, membrane time constant, and signal attenuation properties between the soma and the dendrites) and active conditions (rheobase current and afterhyperpolarization duration at the soma and plateau behavior at the dendrites). To construct the muscle unit, we used a recently developed muscle modeling approach that reflects the experimentally identified dependencies of muscle activation dynamics on isometric, isokinetic and dynamic variation in muscle length over a full range of stimulation frequencies. Then, we designed the simulation software based on the object-oriented programing paradigm and developed the software using open-source Python language to be fully operational using graphical user interfaces. Using the developed software, separate simulations could be performed for a single motoneuron, muscle unit and motor unit under a wide range of experimental input protocols, and a hierarchical analysis could be performed from a single channel to the entire system behavior. Our model motor unit and simulation software may represent efficient tools not only for researchers studying the neural control of force production from a cellular perspective but also for instructors and students in motor physiology classroom settings.

Response inhibition rapidly increases single-neuron responses in the subthalamic nucleus of patients with Parkinson's disease.

PubMed

Benis, Damien; David, Olivier; Piallat, Brigitte; Kibleur, Astrid; Goetz, Laurent; Bhattacharjee, Manik; Fraix, Valérie; Seigneuret, Eric; Krack, Paul; Chabardès, Stéphan; Bastin, Julien

2016-11-01

The subthalamic nucleus (STN) plays a critical role during action inhibition, perhaps by acting like a fast brake on the motor system when inappropriate responses have to be rapidly suppressed. However, the mechanisms involving the STN during motor inhibition are still unclear, particularly because of a relative lack of single-cell responses reported in this structure in humans. In this study, we used extracellular microelectrode recordings during deep brain stimulation surgery in patients with Parkinson's disease (PD) to study STN neurophysiological correlates of inhibitory control during a stop signal task. We found two neuronal subpopulations responding either during motor execution (GO units) or during motor inhibition (STOP units). GO units fired selectively before patients' motor responses whereas STOP units fired selectively when patients successfully withheld their move at a latency preceding the duration of the inhibition process. These results provide electrophysiological evidence for the hypothesized role of the STN in current models of response inhibition. Copyright © 2016. Published by Elsevier Ltd.

High-threshold motor unit firing reflects force recovery following a bout of damaging eccentric exercise.

PubMed

Macgregor, Lewis J; Hunter, Angus M

2018-01-01

Exercise-induced muscle damage (EIMD) is associated with impaired muscle function and reduced neuromuscular recruitment. However, motor unit firing behaviour throughout the recovery period is unclear. EIMD impairment of maximal voluntary force (MVC) will, in part, be caused by reduced high-threshold motor unit firing, which will subsequently increase to recover MVC. Fourteen healthy active males completed a bout of eccentric exercise on the knee extensors, with measurements of MVC, rate of torque development and surface electromyography performed pre-exercise and 2, 3, 7 and 14 days post-exercise, on both damaged and control limb. EIMD was associated with decreased MVC (235.2 ± 49.3 Nm vs. 161.3 ± 52.5 Nm; p <0.001) and rate of torque development (495.7 ± 136.9 Nm.s-1 vs. 163.4 ± 163.7 Nm.s-1; p <0.001) 48h post-exercise. Mean motor unit firing rate was reduced (16.4 ± 2.2 Hz vs. 12.6 ± 1.7 Hz; p <0.01) in high-threshold motor units only, 48h post-exercise, and common drive was elevated (0.36 ± 0.027 vs. 0.56 ± 0.032; p< 0.001) 48h post-exercise. The firing rate of high-threshold motor units was reduced in parallel with impaired muscle function, whilst early recruited motor units remained unaltered. Common drive of motor units increased in offset to the firing rate impairment. These alterations correlated with the recovery of force decrement, but not of pain elevation. This study provides fresh insight into the central mechanisms associated with EIMD recovery, relative to muscle function. These findings may in turn lead to development of novel management and preventative procedures.

High-threshold motor unit firing reflects force recovery following a bout of damaging eccentric exercise

PubMed Central

Macgregor, Lewis J.

2018-01-01

Exercise-induced muscle damage (EIMD) is associated with impaired muscle function and reduced neuromuscular recruitment. However, motor unit firing behaviour throughout the recovery period is unclear. EIMD impairment of maximal voluntary force (MVC) will, in part, be caused by reduced high-threshold motor unit firing, which will subsequently increase to recover MVC. Fourteen healthy active males completed a bout of eccentric exercise on the knee extensors, with measurements of MVC, rate of torque development and surface electromyography performed pre-exercise and 2, 3, 7 and 14 days post-exercise, on both damaged and control limb. EIMD was associated with decreased MVC (235.2 ± 49.3 Nm vs. 161.3 ± 52.5 Nm; p <0.001) and rate of torque development (495.7 ± 136.9 Nm.s-1 vs. 163.4 ± 163.7 Nm.s-1; p <0.001) 48h post-exercise. Mean motor unit firing rate was reduced (16.4 ± 2.2 Hz vs. 12.6 ± 1.7 Hz; p <0.01) in high-threshold motor units only, 48h post-exercise, and common drive was elevated (0.36 ± 0.027 vs. 0.56 ± 0.032; p< 0.001) 48h post-exercise. The firing rate of high-threshold motor units was reduced in parallel with impaired muscle function, whilst early recruited motor units remained unaltered. Common drive of motor units increased in offset to the firing rate impairment. These alterations correlated with the recovery of force decrement, but not of pain elevation. This study provides fresh insight into the central mechanisms associated with EIMD recovery, relative to muscle function. These findings may in turn lead to development of novel management and preventative procedures. PMID:29630622

Dealing with time-varying recruitment and length in Hill-type muscle models.

PubMed

Hamouda, Ahmed; Kenney, Laurence; Howard, David

2016-10-03

Hill-type muscle models are often used in muscle simulation studies and also in the design and virtual prototyping of functional electrical stimulation systems. These models have to behave in a sufficiently realistic manner when recruitment level and contractile element (CE) length change continuously. For this reason, most previous models have used instantaneous CE length in the muscle׳s force vs. length (F-L) relationship, but thereby neglect the instability problem on the descending limb (i.e. region of negative slope) of the F-L relationship. Ideally CE length at initial recruitment should be used but this requires a multiple-motor-unit muscle model to properly account for different motor-units having different initial lengths when recruited. None of the multiple-motor-unit models reported in the literature have used initial CE length in the muscle׳s F-L relationship, thereby also neglecting the descending limb instability problem. To address the problem of muscle modelling for continuously varying recruitment and length, and hence different values of initial CE length for different motor-units, a new multiple-motor-unit muscle model is presented which considers the muscle to comprise 1000 individual Hill-type virtual motor-units, which determine the total isometric force. Other parts of the model (F-V relationship and passive elements) are not dependent on the initial CE length and, therefore, they are implemented for the muscle as a whole rather than for the individual motor-units. The results demonstrate the potential errors introduced by using a single-motor-unit model and also the instantaneous CE length in the F-L relationship, both of which are common in FES control studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Gestalt principles in the control of motor action.

PubMed

Klapp, Stuart T; Jagacinski, Richard J

2011-05-01

We argue that 4 fundamental gestalt phenomena in perception apply to the control of motor action. First, a motor gestalt, like a perceptual gestalt, is holistic in the sense that it is processed as a single unit. This notion is consistent with reaction time results indicating that all gestures for a brief unit of action must be programmed prior to initiation of any part of the movement. Additional reaction time results related to initiation of longer responses are consistent with processing in terms of a sequence of indivisible motor gestalts. Some actions (e.g., many involving coordination of the hands) can be carried out effectively only if represented as a unitary gestalt. Second, a perceptual gestalt is independent of specific sensory receptors, as evidenced by perceptual constancy. In a similar manner a motor gestalt can be represented independently of specific muscular effectors, thereby allowing motor constancy. Third, just as a perceptual pattern (e.g., a Necker cube) is exclusively structured into only 1 of its possible configurations at any moment in time, processing prior to action is limited to 1 motor gestalt. Fourth, grouping in apparent motion leads to stream segregation in visual and auditory perception; this segregation is present in motor action and is dependent on the temporal rate. We discuss congruence of gestalt phenomena across perception and motor action (a) in relation to a unitary perceptual-motor code, (b) with respect to differences in the role of awareness, and (c) in conjunction with separate neural pathways for conscious perception and motor control. © 2011 American Psychological Association

Advanced Motor Control Test Facility for NASA GRC Flywheel Energy Storage System Technology Development Unit

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Kascak, Peter E.; Hofmann, Heath; Mackin, Michael; Santiago, Walter; Jansen, Ralph

2001-01-01

This paper describes the flywheel test facility developed at the NASA Glenn Research Center with particular emphasis on the motor drive components and control. A four-pole permanent magnet synchronous machine, suspended on magnetic bearings, is controlled with a field orientation algorithm. A discussion of the estimation of the rotor position and speed from a "once around signal" is given. The elimination of small dc currents by using a concurrent stationary frame current regulator is discussed and demonstrated. Initial experimental results are presented showing the successful operation and control of the unit at speeds up to 20,000 rpm.

Filtering and Control of High Speed Motor Current in a Flywheel Energy Storage System

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Santiago, Walter

2004-01-01

The NASA Glenn Research Center has been developing technology to enable the use of high speed flywheel energy storage units in future spacecraft for the last several years. An integral part of the flywheel unit is the three phase motor/generator that is used to accelerate and decelerate the flywheel. The motor/generator voltage is supplied from a pulse width modulated (PWM) inverter operating from a fixed DC voltage supply. The motor current is regulated through a closed loop current control that commands the necessary voltage from the inverter to achieve the desired current. The current regulation loop is the innermost control loop of the overall flywheel system and, as a result, must be fast and accurate over the entire operating speed range (20,000 to 60,000 rpm) of the flywheel. The voltage applied to the motor is a high frequency PWM version of the DC bus voltage that results in the commanded fundamental value plus higher order harmonics. Most of the harmonic content is at the switching frequency and above. The higher order harmonics cause a rapid change in voltage to be applied to the motor that can result in large voltage stresses across the motor windings. In addition, the high frequency content in the motor causes sensor noise in the magnetic bearings that leads to disturbances for the bearing control. To alleviate these problems, a filter is used to present a more sinusoidal voltage to the motor/generator. However, the filter adds additional dynamics and phase lag to the motor system that can interfere with the performance of the current regulator. This paper will discuss the tuning methodology and results for the motor/generator current regulator and the impact of the filter on the control. Results at speeds up to 50,000 rpm are presented.

Effect of motor unit recruitment on functional vasodilatation in hamster retractor muscle

PubMed Central

Van Teeffelen, Jurgen W G E; Segal, Steven S

2000-01-01

The effect of motor unit recruitment on functional vasodilatation was investigated in hamster retractor muscle. Recruitment (i.e. peak tension) was controlled with voltage applied to the spinal accessory nerve (high = maximum tension; intermediate = ∼50% maximum; low = ∼25% maximum). Vasodilatory responses (diameter × time integral, DTI) to rhythmic contractions (1 per 2 s for 65 s) were evaluated in first, second and third orderarterioles and in feed arteries. Reciprocal changes in duty cycle (range, 2·5–25 %) effectively maintained the total active tension (tension × time integral, TTI) constant across recruitment levels. With constant TTI and stimulation frequency (40 Hz), DTI in all vessels increased with motor unit recruitment. DTI increased from distal arterioles up through proximal feed arteries. To determine whether the effect of recruitment on DTI was due to increased peak tension, the latter was controlled with stimulation frequency (15, 20 and 40 Hz) during maximum (high) recruitment. With constant TTI, DTI then decreased as peak tension increased. To explore the interaction between recruitment and duty cycle on DTI, each recruitment level was applied at 2.5, 10 and 20 % duty cycle (at 40 Hz). For a given increase in TTI, recruitment had a greater effect on DTI than did duty cycle. Functional vasodilatation in response to rhythmic contractions is facilitated by motor unit recruitment. Thus, vasodilatory responses are determined not only by the total tension produced, but also by the number of active motor units. PMID:10747197

28. Credit JTL. Overview of unit 5 (installed 1908) showing ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

28. Credit JTL. Overview of unit 5 (installed 1908) showing exciter, generator, deflector motor, needle valve control, impulse wheel housing, and gate valve controls. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

Human spinal cord injury: motor unit properties and behaviour.

PubMed

Thomas, C K; Bakels, R; Klein, C S; Zijdewind, I

2014-01-01

Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralysed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fibre-type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI. © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Rotatable non-circular forebody flow controller

NASA Technical Reports Server (NTRS)

Moskovitz, Cary A. (Inventor)

1991-01-01

The invention is a rotatable, non-circular forebody flow controller. The apparatus comprises a small geometric device located at a nose of a forebody of an aircraft and a non-circular cross-sectional area that extends toward the apex of the aircraft. The device is symmetrical about a reference plane and preferably attaches to an axle which in turn attaches to a rotating motor. The motor rotates the device about an axis of rotation. Preferably, a control unit connected to an aircraft flight control computer signals to the rotating motor the proper rotational positioning of the geometric device.

Lower layers in the motor cortex are more effective targets for penetrating microelectrodes in cortical prostheses

NASA Astrophysics Data System (ADS)

Parikh, Hirak; Marzullo, Timothy C.; Kipke, Daryl R.

2009-04-01

Improving cortical prostheses requires the development of recording neural interfaces that are efficient in terms of providing maximal control information with minimal interface complexity. While the typical approaches have targeted neurons in the motor cortex with multiple penetrating shanks, an alternative approach is to determine an efficient distribution of electrode sites within the layers of the cortex with fewer penetrating shanks. The objective of this study was to compare unit activity in the upper and lower layers of the cortex with respect to movement and direction in order to inform the design of penetrating microelectrodes. Four rats were implanted bilaterally with multi-site single-shank silicon microelectrode arrays in the neck/shoulder region of the motor cortex. We simultaneously recorded unit activity across all layers of the motor cortex while the animal was engaged in a movement direction task. Localization of the electrode array within the different layers of the cortex was determined by histology. We denoted units from layers 2 and 3 and units as upper layer units, and units from layers 5 and 6 as lower layer units. Analysis of unit spiking activity demonstrated that both the upper and lower layers encode movement and direction information. Unit responses in either cortical layer of the cortex were not preferentially associated with contralateral or ipsilateral movement. Aggregate analysis (633 neurons) and best session analysis (75 neurons) indicated that units in the lower layers (layers 5, 6) are more likely to encode direction information when compared to units in the upper layers (layers 2, 3) (p< 0.05). These results suggest that electrode sites clustered in the lower layers provide access to more salient control information for cortical neuroprostheses.

Linear Motor With Air Slide

NASA Technical Reports Server (NTRS)

Johnson, Bruce G.; Gerver, Michael J.; Hawkey, Timothy J.; Fenn, Ralph C.

1993-01-01

Improved linear actuator comprises air slide and linear electric motor. Unit exhibits low friction, low backlash, and more nearly even acceleration. Used in machinery in which positions, velocities, and accelerations must be carefully controlled and/or vibrations must be suppressed.

The human motor neuron pools receive a dominant slow‐varying common synaptic input

PubMed Central

Negro, Francesco; Yavuz, Utku Şükrü

2016-01-01

Key points Motor neurons in a pool receive both common and independent synaptic inputs, although the proportion and role of their common synaptic input is debated.Classic correlation techniques between motor unit spike trains do not measure the absolute proportion of common input and have limitations as a result of the non‐linearity of motor neurons.We propose a method that for the first time allows an accurate quantification of the absolute proportion of low frequency common synaptic input (<5 Hz) to motor neurons in humans.We applied the proposed method to three human muscles and determined experimentally that they receive a similar large amount (>60%) of common input, irrespective of their different functional and control properties.These results increase our knowledge about the role of common and independent input to motor neurons in force control. Abstract Motor neurons receive both common and independent synaptic inputs. This observation is classically based on the presence of a significant correlation between pairs of motor unit spike trains. The functional significance of different relative proportions of common input across muscles, individuals and conditions is still debated. One of the limitations in our understanding of correlated input to motor neurons is that it has not been possible so far to quantify the absolute proportion of common input with respect to the total synaptic input received by the motor neurons. Indeed, correlation measures of pairs of output spike trains only allow for relative comparisons. In the present study, we report for the first time an approach for measuring the proportion of common input in the low frequency bandwidth (<5 Hz) to a motor neuron pool in humans. This estimate is based on a phenomenological model and the theoretical fitting of the experimental values of coherence between the permutations of groups of motor unit spike trains. We demonstrate the validity of this theoretical estimate with several simulations. Moreover, we applied this method to three human muscles: the abductor digiti minimi, tibialis anterior and vastus medialis. Despite these muscles having different functional roles and control properties, as confirmed by the results of the present study, we estimate that their motor pools receive a similar and large (>60%) proportion of common low frequency oscillations with respect to their total synaptic input. These results suggest that the central nervous system provides a large amount of common input to motor neuron pools, in a similar way to that for muscles with different functional and control properties. PMID:27151459

Controlled release of free-falling test models

NASA Technical Reports Server (NTRS)

Fife, W. J.; Holway, H. P.

1970-01-01

Releasing device, powered by a drill motor through an adjustable speed reducer, has a spinning release head with three retractable spring-loaded fingers. The fingers are retracted by manual triggering of a cable at the motor end of the unit.

Robust tactile sensory responses in finger area of primate motor cortex relevant to prosthetic control

NASA Astrophysics Data System (ADS)

Schroeder, Karen E.; Irwin, Zachary T.; Bullard, Autumn J.; Thompson, David E.; Bentley, J. Nicole; Stacey, William C.; Patil, Parag G.; Chestek, Cynthia A.

2017-08-01

Objective. Challenges in improving the performance of dexterous upper-limb brain-machine interfaces (BMIs) have prompted renewed interest in quantifying the amount and type of sensory information naturally encoded in the primary motor cortex (M1). Previous single unit studies in monkeys showed M1 is responsive to tactile stimulation, as well as passive and active movement of the limbs. However, recent work in this area has focused primarily on proprioception. Here we examined instead how tactile somatosensation of the hand and fingers is represented in M1. Approach. We recorded multi- and single units and thresholded neural activity from macaque M1 while gently brushing individual finger pads at 2 Hz. We also recorded broadband neural activity from electrocorticogram (ECoG) grids placed on human motor cortex, while applying the same tactile stimulus. Main results. Units displaying significant differences in firing rates between individual fingers (p  <  0.05) represented up to 76.7% of sorted multiunits across four monkeys. After normalizing by the number of channels with significant motor finger responses, the percentage of electrodes with significant tactile responses was 74.9%  ±  24.7%. No somatotopic organization of finger preference was obvious across cortex, but many units exhibited cosine-like tuning across multiple digits. Sufficient sensory information was present in M1 to correctly decode stimulus position from multiunit activity above chance levels in all monkeys, and also from ECoG gamma power in two human subjects. Significance. These results provide some explanation for difficulties experienced by motor decoders in clinical trials of cortically controlled prosthetic hands, as well as the general problem of disentangling motor and sensory signals in primate motor cortex during dextrous tasks. Additionally, examination of unit tuning during tactile and proprioceptive inputs indicates cells are often tuned differently in different contexts, reinforcing the need for continued refinement of BMI training and decoding approaches to closed-loop BMI systems for dexterous grasping.

Common input to motor units of intrinsic and extrinsic hand muscles during two-digit object hold.

PubMed

Winges, Sara A; Kornatz, Kurt W; Santello, Marco

2008-03-01

Anatomical and physiological evidence suggests that common input to motor neurons of hand muscles is an important neural mechanism for hand control. To gain insight into the synaptic input underlying the coordination of hand muscles, significant effort has been devoted to describing the distribution of common input across motor units of extrinsic muscles. Much less is known, however, about the distribution of common input to motor units belonging to different intrinsic muscles and to intrinsic-extrinsic muscle pairs. To address this void in the literature, we quantified the incidence and strength of near-simultaneous discharges of motor units residing in either the same or different intrinsic hand muscles (m. first dorsal, FDI, and m. first palmar interosseus, FPI) during two-digit object hold. To extend the characterization of common input to pairs of extrinsic muscles (previous work) and pairs of intrinsic muscles (present work), we also recorded electromyographic (EMG) activity from an extrinsic thumb muscle (m. flexor pollicis longus, FPL). Motor-unit synchrony across FDI and FPI was weak (common input strength, CIS, mean +/- SE: 0.17 +/- 0.02). Similarly, motor units from extrinsic-intrinsic muscle pairs were characterized by weak synchrony (FPL-FDI: 0.25 +/- 0.02; FPL-FPI: 0.29 +/- 0.03) although stronger than FDI-FPI. Last, CIS from within FDI and FPI was more than three times stronger (0.70 +/- 0.06 and 0.66 +/- 0.06, respectively) than across these muscles. We discuss present and previous findings within the framework of muscle-pair specific distribution of common input to hand muscles based on their functional role in grasping.

Activation properties of trigeminal motoneurons in participants with and without bruxism

PubMed Central

D'Amico, Jessica M.; Yavuz, Ş. Utku; Saraçoğlu, Ahmet; Atiş, Elif Sibel; Türker, Kemal S.

2013-01-01

In animals, sodium- and calcium-mediated persistent inward currents (PICs), which produce long-lasting periods of depolarization under conditions of low synaptic drive, can be activated in trigeminal motoneurons following the application of the monoamine serotonin. Here we examined if PICs are activated in human trigeminal motoneurons during voluntary contractions and under physiological levels of monoaminergic drive (e.g., serotonin and norepinephrine) using a paired motor unit analysis technique. We also examined if PICs activated during voluntary contractions are larger in participants who demonstrate involuntary chewing during sleep (bruxism), which is accompanied by periods of high monoaminergic drive. In control participants, during a slowly increasing and then decreasing isometric contraction, the firing rate of an earlier-recruited masseter motor unit, which served as a measure of synaptic input to a later-recruited test unit, was consistently lower during derecruitment of the test unit compared with at recruitment (ΔF = 4.6 ± 1.5 imp/s). The ΔF, therefore, is a measure of the reduction in synaptic input needed to counteract the depolarization from the PIC to provide an indirect estimate of PIC amplitude. The range of ΔF values measured in the bruxer participants during similar voluntary contractions was the same as in controls, suggesting that abnormally high levels of monoaminergic drive are not continually present in the absence of involuntary motor activity. We also observed a consistent “onion skin effect” during the moderately sized contractions (<20% of maximal), whereby the firing rate of higher threshold motor units discharged at slower rates (by 4–7 imp/s) compared with motor units with relatively lower thresholds. The presence of lower firing rates in the more fatigue-prone, higher threshold trigeminal motoneurons, in addition to the activation of PICs, likely facilitates the activation of the masseter muscle during motor activities such as eating, nonnutritive chewing, clenching, and yawning. PMID:24068753

A programmable positioning stepper-motor controller with a multibus/IEEE 796 compatible interface.

PubMed

Papoff, P; Ricci, D

1984-02-01

A programmable positioning stepper-motor controller, based on the Multibus/IEEE 796 standard interface, has been assembled by use of some intelligent and programmable integrated circuits. This controller, organized as a bus-slave unit, has been planned for local management of up to four stepper motors working simultaneously. The number of steps, the direction of rotation and the step-rate for the positioning of each motor are issued by the bus master microcomputer to the controller which handles all the required operations. Once each positioning has been performed, the controller informs the master by generating a proper bus-vectored interrupt. Displacements in up to 64,000 steps may be programmed with step-rates ranging from 0.1 to 6550 steps/sec. This device, for which only low-cost, high-performance components are required, can be successfully used in a wide range of applications and can be easily extended to control more than four stepper motors.

Acute effects of dynamic exercises on the relationship between the motor unit firing rate and the recruitment threshold.

PubMed

Ye, Xin; Beck, Travis W; DeFreitas, Jason M; Wages, Nathan P

2015-04-01

The aim of this study was to compare the acute effects of concentric versus eccentric exercise on motor control strategies. Fifteen men performed six sets of 10 repetitions of maximal concentric exercises or eccentric isokinetic exercises with their dominant elbow flexors on separate experimental visits. Before and after the exercise, maximal strength testing and submaximal trapezoid isometric contractions (40% of the maximal force) were performed. Both exercise conditions caused significant strength loss in the elbow flexors, but the loss was greater following the eccentric exercise (t=2.401, P=.031). The surface electromyographic signals obtained from the submaximal trapezoid isometric contractions were decomposed into individual motor unit action potential trains. For each submaximal trapezoid isometric contraction, the relationship between the average motor unit firing rate and the recruitment threshold was examined using linear regression analysis. In contrast to the concentric exercise, which did not cause significant changes in the mean linear slope coefficient and y-intercept of the linear regression line, the eccentric exercise resulted in a lower mean linear slope and an increased mean y-intercept, thereby indicating that increasing the firing rates of low-threshold motor units may be more important than recruiting high-threshold motor units to compensate for eccentric exercise-induced strength loss. Copyright © 2014 Elsevier B.V. All rights reserved.

Adjustments in motor unit properties during fatiguing contractions after training.

PubMed

Vila-Chã, Carolina; Falla, Deborah; Correia, Miguel Velhote; Farina, Dario

2012-04-01

The objective of the study was to investigate the effect of strength and endurance training on muscle fiber membrane properties and discharge rates of low-threshold motor units of the vasti muscles during fatiguing contractions. Twenty-five sedentary healthy men (age (mean ± SD) = 26.3 ± 3.9 yr) were randomly assigned to one of three groups: strength training, endurance training, or a control group. Conventional endurance and strength training was performed 3 d·wk⁻¹, during a period of 6 wk. Motor unit conduction velocity and EMG amplitude of the vastus medialis obliquus and lateralis muscles and biceps femoris were measured during sustained isometric knee extensions at 10% and 30% of the maximum voluntary contraction before and immediately after training. After 6 wk of training, the reduction in motor unit conduction velocity during the sustained contractions at 30% of the maximum voluntary force occurred at slower rates compared with baseline (P < 0.05). However, the rate of decrease was lower after endurance training compared with strength training (P < 0.01). For all groups, motor unit discharge rates declined during the sustained contraction (P < 0.001), and their trend was not altered by training. In addition, the biceps femoris-vasti coactivation ratio declined after the endurance training. Short-term strength and endurance training induces alterations of the electrophysiological membrane properties of the muscle fiber. In particular, endurance training lowers the rate of decline of motor unit conduction velocity during sustained contractions more than strength training.

Respiration-related discharge of hyoglossus muscle motor units in the rat.

PubMed

Powell, Gregory L; Rice, Amber; Bennett-Cross, Seres J; Fregosi, Ralph F

2014-01-01

Although respiratory muscle motor units have been studied during natural breathing, simultaneous measures of muscle force have never been obtained. Tongue retractor muscles, such as the hyoglossus (HG), play an important role in swallowing, licking, chewing, breathing, and, in humans, speech. The HG is phasically recruited during the inspiratory phase of the respiratory cycle. Moreover, in urethane anesthetized rats the drive to the HG waxes and wanes spontaneously, providing a unique opportunity to study motor unit firing patterns as the muscle is driven naturally by the central pattern generator for breathing. We recorded tongue retraction force, the whole HG muscle EMG and the activity of 38 HG motor units in spontaneously breathing anesthetized rats under low-force and high-force conditions. Activity in all cases was confined to the inspiratory phase of the respiratory cycle. Changes in the EMG were correlated significantly with corresponding changes in force, with the change in EMG able to predict 53-68% of the force variation. Mean and peak motor unit firing rates were greater under high-force conditions, although the magnitude of discharge rate modulation varied widely across the population. Changes in mean and peak firing rates were significantly correlated with the corresponding changes in force, but the correlations were weak (r(2) = 0.27 and 0.25, respectively). These data indicate that, during spontaneous breathing, recruitment of HG motor units plays a critical role in the control of muscle force, with firing rate modulation playing an important but lesser role.

REACH. Electricity Units, Post-Secondary.

ERIC Educational Resources Information Center

Smith, Gene; And Others

As a part of the REACH (Refrigeration, Electro-Mechanical, Air-Conditioning, Heating) electromechanical cluster, this postsecondary student manual contains individualized instructional units in the area of electricity. The instructional units focus on electricity fundamentals, electric motors, electrical components, and controls and installation.…

Relation between muscle mass, motor units and type of training in master athletes.

PubMed

Drey, Michael; Sieber, Cornel C; Degens, Hans; McPhee, Jamie; Korhonen, Marko T; Müller, Klaus; Ganse, Bergita; Rittweger, Jörn

2016-01-01

The aim of this study was to measure the number of motor units and muscle mass in power-trained and endurance-trained master athletes compared with community-dwelling older adults. Seventy-five master athletes (52 power- and 23 endurance-trained athletes) were recruited at the 2012 European Veteran Athletics Championships in Zittau (Germany). One hundred and forty-nine community-dwelling older adults served as controls. In all participants, the motor unit number index (MUNIX) in the hypothenar muscle and whole body muscle mass was determined by bioelectrical impedance analysis (BIA). In both male and female master athletes, there were significant negative correlations between age and muscle mass (female: r = -0·510, P = 0·002; male: r = -0·714, P<0·001). Master athletes showed a weak correlation (r = -0·295, P = 0·010) between MUNIX and age. Master athletes exhibited significantly higher values than the control group with regard to both muscle mass (P = 0·002) and motor units (P = 0·004). Subanalysis showed that only power trained master athletes had both a larger muscle mass (P<0·001) and a higher MUNIX (P = 0·014) than the control group. Among the master athletes, power-trained athletes had a larger (P<0·001) muscle mass than endurance-trained athletes. The present data of master athletes are compatible with the hypothesis of an age-related decline in whole body muscle mass and motor units. Nevertheless, the data suggest that the master athletes' high level of physical activity may protect motoneurons. In addition, power training seems to have a positive effect on muscle mass and could therefore be an effective method of training to prevent sarcopenia. © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

A theory of cerebellar cortex and adaptive motor control based on two types of universal function approximation capability.

PubMed

Fujita, Masahiko

2016-03-01

Lesions of the cerebellum result in large errors in movements. The cerebellum adaptively controls the strength and timing of motor command signals depending on the internal and external environments of movements. The present theory describes how the cerebellar cortex can control signals for accurate and timed movements. A model network of the cerebellar Golgi and granule cells is shown to be equivalent to a multiple-input (from mossy fibers) hierarchical neural network with a single hidden layer of threshold units (granule cells) that receive a common recurrent inhibition (from a Golgi cell). The weighted sum of the hidden unit signals (Purkinje cell output) is theoretically analyzed regarding the capability of the network to perform two types of universal function approximation. The hidden units begin firing as the excitatory inputs exceed the recurrent inhibition. This simple threshold feature leads to the first approximation theory, and the network final output can be any continuous function of the multiple inputs. When the input is constant, this output becomes stationary. However, when the recurrent unit activity is triggered to decrease or the recurrent inhibition is triggered to increase through a certain mechanism (metabotropic modulation or extrasynaptic spillover), the network can generate any continuous signals for a prolonged period of change in the activity of recurrent signals, as the second approximation theory shows. By incorporating the cerebellar capability of two such types of approximations to a motor system, in which learning proceeds through repeated movement trials with accompanying corrections, accurate and timed responses for reaching the target can be adaptively acquired. Simple models of motor control can solve the motor error vs. sensory error problem, as well as the structural aspects of credit (or error) assignment problem. Two physiological experiments are proposed for examining the delay and trace conditioning of eyelid responses, as well as saccade adaptation, to investigate this novel idea of cerebellar processing. Copyright © 2015 Elsevier Ltd. All rights reserved.

A motor unit-based model of muscle fatigue

PubMed Central

2017-01-01

Muscle fatigue is a temporary decline in the force and power capacity of skeletal muscle resulting from muscle activity. Because control of muscle is realized at the level of the motor unit (MU), it seems important to consider the physiological properties of motor units when attempting to understand and predict muscle fatigue. Therefore, we developed a phenomenological model of motor unit fatigue as a tractable means to predict muscle fatigue for a variety of tasks and to illustrate the individual contractile responses of MUs whose collective action determines the trajectory of changes in muscle force capacity during prolonged activity. An existing MU population model was used to simulate MU firing rates and isometric muscle forces and, to that model, we added fatigue-related changes in MU force, contraction time, and firing rate associated with sustained voluntary contractions. The model accurately estimated endurance times for sustained isometric contractions across a wide range of target levels. In addition, simulations were run for situations that have little experimental precedent to demonstrate the potential utility of the model to predict motor unit fatigue for more complicated, real-world applications. Moreover, the model provided insight into the complex orchestration of MU force contributions during fatigue, that would be unattainable with current experimental approaches. PMID:28574981

50. VIEW LOOKING SOUTHEAST AT A MOTORGENERATOR SET LOCATED UNDER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

50. VIEW LOOKING SOUTHEAST AT A MOTOR-GENERATOR SET LOCATED UNDER CONTROL ROOM. THREE 450 kva., 2500 VOLT, 60 CYCLE MOTOR-GENERATOR UNITS PROVIDED POWER FOR THE RAILROAD SIGNAL SYSTEM. 25 CYCLE POWER WAS PROVIDED TO THE MOTOR (LEFT BACKGROUND). THE MOTOR TURNED THE GENERATOR (CENTER FOREGROUND) WHICH PRODUCED 60 CYCLE POWER TO OPERATE LIGHTS AND SIGNALING DEVICES. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

Note: computer controlled rotation mount for large diameter optics.

PubMed

Rakonjac, Ana; Roberts, Kris O; Deb, Amita B; Kjærgaard, Niels

2013-02-01

We describe the construction of a motorized optical rotation mount with a 40 mm clear aperture. The device is used to remotely control the power of large diameter laser beams for a magneto-optical trap. A piezo-electric ultrasonic motor on a printed circuit board provides rotation with a precision better than 0.03° and allows for a very compact design. The rotation unit is controlled from a computer via serial communication, making integration into most software control platforms straightforward.

Unstructured Facility Navigation by Applying the NIST 4D/RCS Architecture

DTIC Science & Technology

2006-07-01

control, and the planner); wire- less data and emergency stop radios; GPS receiver; inertial navigation unit; dual stereo cameras; infrared sensors...current Actuators Wheel motors, camera controls Scale & filter signals status commands commands commands GPS Antenna Dual stereo cameras...used in the sensory processing module include the two pairs of stereo color cameras, the physical bumper and infrared bumper sensors, the motor

Force-frequency and fatigue properties of motor units in muscles that control digits of the human hand.

PubMed

Fuglevand, A J; Macefield, V G; Bigland-Ritchie, B

1999-04-01

Modulation of motor unit activation rate is a fundamental process by which the mammalian nervous system encodes muscle force. To identify how rate coding of force may change as a consequence of fatigue, intraneural microstimulation of motor axons was used to elicit twitch and force-frequency responses before and after 2 min of intermittent stimulation (40-Hz train for 330 ms, 1 train/s) in single motor units of human long finger flexor muscles and intrinsic hand muscles. Before fatigue, two groups of units could be distinguished based on the stimulus frequency needed to elicit half-maximal force; group 1 (n = 8) required 9.1 +/- 0.5 Hz (means +/- SD), and group 2 (n = 5) required 15.5 +/- 1.1 Hz. Twitch contraction times were significantly different between these two groups (group 1 = 66. 5 ms; group 2 = 45.9 ms). Overall 18% of the units were fatigue resistant [fatigue index (FI) > 0.75], 64% had intermediate fatigue sensitivity (0.25

Reflex control of discharge in motor fibres to the larynx

PubMed Central

Głogowska, Maria; Stransky, A.; Widdicombe, J. G.

1974-01-01

1. Action potentials have been recorded from single laryngeal motor fibres, with expiratory or inspiratory phases, in cats anaesthetized with pentobarbitone and breathing through a tracheal cannula. 2. Pneumothorax increased the discharge of both inspiratory and expiratory units, the inspiratory response being greatly reduced by bilateral vagotomy below the origin of the recurrent laryngeal nerves. 3. Addition of a `viscous' resistance to breathing, or asphyxial rebreathing through an added dead space, increased the activity of inspiratory units and decreased that of expiratory units. 4. Induction of pulmonary oedema decreased the discharge of inspiratory units and increased that of expiratory units. After vagotomy the response of inspiratory units was reversed. 5. Intravenous injections of potassium cyanide increased the activity of both types of unit. 6. Chemical irritation of the laryngeal mucosa decreased the discharge of inspiratory units and increased that of expiratory units, whether the vagi were intact or cut. 7. It is concluded that expiratory unit discharge can be correlated with expiratory laryngeal resistance, but that inspiratory unit discharge does not correlate so well with inspiratory laryngeal resistance. 8. The relationship between laryngeal motor-fibre activity and the contractions of the inspiratory and expiratory muscles of breathing is discussed. PMID:4415512

Motor unit recruitment in human biceps brachii during sustained voluntary contractions.

PubMed

Riley, Zachary A; Maerz, Adam H; Litsey, Jane C; Enoka, Roger M

2008-04-15

The purpose of the study was to examine the influence of the difference between the recruitment threshold of a motor unit and the target force of the sustained contraction on the discharge of the motor unit at recruitment. The discharge characteristics of 53 motor units in biceps brachii were recorded after being recruited during a sustained contraction. Some motor units (n = 22) discharged action potentials tonically after being recruited, whereas others (n = 31) discharged intermittent trains of action potentials. The two groups of motor units were distinguished by the difference between the recruitment threshold of the motor unit and the target force for the sustained contraction: tonic, 5.9 +/- 2.5%; intermittent, 10.7 +/- 2.9%. Discharge rate for the tonic units decreased progressively (13.9 +/- 2.7 to 11.7 +/- 2.6 pulses s(-1); P = 0.04) during the 99 +/- 111 s contraction. Train rate, train duration and average discharge rate for the intermittent motor units did not change across 211 +/- 153 s of intermittent discharge. The initial discharge rate at recruitment during the sustained contraction was lower for the intermittent motor units (11.0 +/- 3.3 pulses s(-1)) than the tonic motor units (13.7 +/- 3.3 pulses s(-1); P = 0.005), and the coefficient of variation for interspike interval was higher for the intermittent motor units (34.6 +/- 12.3%) than the tonic motor units (21.2 +/- 9.4%) at recruitment (P = 0.001) and remained elevated for discharge duration (34.6 +/- 9.2% versus 19.1 +/- 11.7%, P < 0.001). In an additional experiment, 12 motor units were recorded at two different target forces below recruitment threshold (5.7 +/- 1.9% and 10.5 +/- 2.4%). Each motor unit exhibited the two discharge patterns (tonic and intermittent) as observed for the 53 motor units. The results suggest that newly recruited motor units with recruitment thresholds closer to the target force experienced less synaptic noise at the time of recruitment that resulted in them discharging action potentials at more regular and greater rates than motor units with recruitment thresholds further from the target force.

Strength training for a child with suspected developmental coordination disorder.

PubMed

Menz, Stacy M; Hatten, Kristin; Grant-Beuttler, Marybeth

2013-01-01

Children with developmental coordination disorder (DCD) demonstrate difficulty with feedforward motor control and use varied compensatory strategies. To examine gross motor function changes following strength training in a child with motor control difficulties. A girl aged 6 years 11 months, with apraxia and hypotonia, and demonstrating motor delays consistent with DCD. Twenty-four strength training sessions were completed using a universal exercise unit. Postintervention scores significantly improved on the Bruininks-Oseretsky test of motor proficiency, second edition, and the Canadian occupational performance measure scores and raised the developmental coordination disorder questionnaire, revised 2007, scores above the range where DCD is suspected. Nonsignificant changes in strength were observed. Improved function and significant gains in manual coordination were observed following blocked practice of isolated, simple joint movements during strength training. Improved motor skills may be because of effective use of feedforward control and improved stabilization. Strength training does not rehearse skills using momentum, explaining nonsignificant changes in locomotor or locomotion areas.

Associations between motor unit action potential parameters and surface EMG features.

PubMed

Del Vecchio, Alessandro; Negro, Francesco; Felici, Francesco; Farina, Dario

2017-10-01

The surface interference EMG signal provides some information on the neural drive to muscles. However, the association between neural drive to muscle and muscle activation has long been debated with controversial indications due to the unavailability of motor unit population data. In this study, we clarify the potential and limitations of interference EMG analysis to infer motor unit recruitment strategies with an experimental investigation of several concurrently active motor units and of the associated features of the surface EMG. For this purpose, we recorded high-density surface EMG signals during linearly increasing force contractions of the tibialis anterior muscle, up to 70% of maximal force. The recruitment threshold (RT), conduction velocity (MUCV), median frequency (MDF MU ), and amplitude (RMS MU ) of action potentials of 587 motor units from 13 individuals were assessed and associated with features of the interference EMG. MUCV was positively associated with RT ( R 2 = 0.64 ± 0.14), whereas MDF MU and RMS MU showed a weaker relation with RT ( R 2 = 0.11 ± 0.11 and 0.39 ± 0.24, respectively). Moreover, the changes in average conduction velocity estimated from the interference EMG predicted well the changes in MUCV ( R 2 = 0.71), with a strong association to ankle dorsiflexion force ( R 2 = 0.81 ± 0.12). Conversely, both the average EMG MDF and RMS were poorly associated with motor unit recruitment. These results clarify the limitations of EMG spectral and amplitude analysis in inferring the neural strategies of muscle control and indicate that, conversely, the average conduction velocity could provide relevant information on these strategies. NEW & NOTEWORTHY The surface EMG provides information on the neural drive to muscles. However, the associations between EMG features and neural drive have been long debated due to unavailability of motor unit population data. Here, by using novel highly accurate decomposition of the EMG, we related motor unit population behavior to a wide range of voluntary forces. The results fully clarify the potential and limitation of the surface EMG to provide estimates of the neural drive to muscles. Copyright © 2017 the American Physiological Society.

Neuronal codes for the inhibitory control of impulsive actions in the rat infralimbic cortex.

PubMed

Tsutsui-Kimura, Iku; Ohmura, Yu; Izumi, Takeshi; Matsushima, Toshiya; Amita, Hidetoshi; Yamaguchi, Taku; Yoshida, Takayuki; Yoshioka, Mitsuhiro

2016-01-01

Poor impulse control is a debilitating condition observed in various psychiatric disorders and could be a risk factor for drug addiction, criminal involvement, and suicide. The rat infralimbic cortex (IL), located in the ventral portion of the medial prefrontal cortex, has been implicated in impulse control. To elucidate the neurophysiological basis of impulse control, we recorded single unit activity in the IL of a rat performing a 3-choiceserial reaction time task (3-CSRTT) and 2-choice task (2-CT), which are animal models for impulsivity. The inactivation of IL neuronal activity with an injection of muscimol (0.1 μg /side) disrupted impulse control in the 3-CSRTT. More than 60% (38/56) of isolated IL units were linked to impulse control, while approximately 30% of all units were linked to attentional function in the 3-CSRTT. To avoid confounding motor-related units with the impulse control-related units, we further conducted the 2-CT in which the animals' motor activities were restricted during recording window. More than 30% (14/44) of recorded IL units were linked to impulse control in the 2-CT. Several types of impulse control-related units were identified. Only 16% of all units were compatible with the results of the muscimol experiment, which showed a transient decline in the firing rate immediately before the release of behavioral inhibition. This is the first study to elucidate the neurophysiological basis of impulse control in the IL and to propose that IL neurons control impulsive actions in a more complex manner than previously considered. Copyright © 2015 Elsevier B.V. All rights reserved.

Improving actuation efficiency through variable recruitment hydraulic McKibben muscles: modeling, orderly recruitment control, and experiments.

PubMed

Meller, Michael; Chipka, Jordan; Volkov, Alexander; Bryant, Matthew; Garcia, Ephrahim

2016-11-03

Hydraulic control systems have become increasingly popular as the means of actuation for human-scale legged robots and assistive devices. One of the biggest limitations to these systems is their run time untethered from a power source. One way to increase endurance is by improving actuation efficiency. We investigate reducing servovalve throttling losses by using a selective recruitment artificial muscle bundle comprised of three motor units. Each motor unit is made up of a pair of hydraulic McKibben muscles connected to one servovalve. The pressure and recruitment state of the artificial muscle bundle can be adjusted to match the load in an efficient manner, much like the firing rate and total number of recruited motor units is adjusted in skeletal muscle. A volume-based effective initial braid angle is used in the model of each recruitment level. This semi-empirical model is utilized to predict the efficiency gains of the proposed variable recruitment actuation scheme versus a throttling-only approach. A real-time orderly recruitment controller with pressure-based thresholds is developed. This controller is used to experimentally validate the model-predicted efficiency gains of recruitment on a robot arm. The results show that utilizing variable recruitment allows for much higher efficiencies over a broader operating envelope.

Segmentation of the mouse fourth deep lumbrical muscle connectome reveals concentric organisation of motor units

PubMed Central

Hirst, Theodore C; Ribchester, Richard R

2013-01-01

Connectomic analysis of the nervous system aims to discover and establish principles that underpin normal and abnormal neural connectivity and function. Here we performed image analysis of motor unit connectivity in the fourth deep lumbrical muscle (4DL) of mice, using transgenic expression of fluorescent protein in motor neurones as a morphological reporter. We developed a method that accelerated segmentation of confocal image projections of 4DL motor units, by applying high resolution (63×, 1.4 NA objective) imaging or deconvolution only where either proved necessary, in order to resolve axon crossings that produced ambiguities in the correct assignment of axon terminals to identified motor units imaged at lower optical resolution (40×, 1.3 NA). The 4DL muscles contained between 4 and 9 motor units and motor unit sizes ranged in distribution from 3 to 111 motor nerve terminals per unit. Several structural properties of the motor units were consistent with those reported in other muscles, including suboptimal wiring length and distribution of motor unit size. Surprisingly, however, small motor units were confined to a region of the muscle near the nerve entry point, whereas their larger counterparts were progressively more widely dispersed, suggesting a previously unrecognised form of segregated motor innervation in this muscle. We also found small but significant differences in variance of motor endplate length in motor units, which correlated weakly with their motor unit size. Thus, our connectomic analysis has revealed a pattern of concentric innervation that may perhaps also exist in other, cylindrical muscles that have not previously been thought to show segregated motor unit organisation. This organisation may be the outcome of competition during postnatal development based on intrinsic neuronal differences in synaptic size or synaptic strength that generates a territorial hierarchy in motor unit size and disposition. PMID:23940381

The Impact of Policy, Environmental, and Educational Interventions: A Synthesis of the Evidence from Two Public Health Success Stories

ERIC Educational Resources Information Center

Gielen, Andrea C.; Green, Lawrence W.

2015-01-01

Motor vehicle safety and tobacco control are among the greatest public health achievements of the 20th century, according to the Centers for Disease Control and Prevention. As the number of miles traveled in the United States multiplied 10 times from the 1920s to the 1990s, the annual motor vehicle crash death rate per vehicle mile traveled…

International Space Station Alpha's bearing, motor, and roll ring module developmental testing and results

NASA Technical Reports Server (NTRS)

Obrien, David L.

1994-01-01

This paper presents the design and developmental testing associated with the bearing, motor, and roll ring module (BMRRM) used for the beta rotation axis on International Space Station Alpha (ISSA). The BMRRM with its controllers located in the electronic control unit (ECU), provides for the solar array pointing and tracking functions as well as power and signal transfer across a rotating interface.

Nondestructive Evaluation of Metallized Tape Bonds Formed by Tape Automated Bonding (TAB)

DTIC Science & Technology

1989-04-01

powered by micro-positioning linear actuators. 3) Interchangeable sample-holding fixtures mounted upon top of slide assembly. 4) Coverslip gantry mounted...Controller Unit 1) Motor power supplies 2) Motor output servo driver amplifiers 3) "Macro-language" command Interpreter 4) Two-way cormunications with...adjustments are manual knobs giving approximately one degree of tilt adjustment per turn. The servo controller has self-contained power supplies for

Training adaptations in the behavior of human motor units.

PubMed

Duchateau, Jacques; Semmler, John G; Enoka, Roger M

2006-12-01

The purpose of this brief review is to examine the neural adaptations associated with training, by focusing on the behavior of single motor units. The review synthesizes current understanding on motor unit recruitment and rate coding during voluntary contractions, briefly describes the techniques used to record motor unit activity, and then evaluates the adaptations that have been observed in motor unit activity during maximal and submaximal contractions. Relatively few studies have directly compared motor unit behavior before and after training. Although some studies suggest that the voluntary activation of muscle can increase slightly with strength training, it is not known how the discharge of motor units changes to produce this increase in activation. The evidence indicates that the increase is not attributable to changes in motor unit synchronization. It has been demonstrated, however, that training can increase both the rate of torque development and the discharge rate of motor units. Furthermore, both strength training and practice of a force-matching task can evoke adaptations in the discharge characteristics of motor units. Because the variability in discharge rate has a significant influence on the fluctuations in force during submaximal contractions, the changes produced with training can influence motor performance during activities of daily living. Little is known, however, about the relative contributions of the descending drive, afferent feedback, spinal circuitry, and motor neuron properties to the observed adaptations in motor unit activity.

Reduced motor neuron excitability is an important contributor to weakness in a rat model of sepsis.

PubMed

Nardelli, Paul; Vincent, Jacob A; Powers, Randall; Cope, Tim C; Rich, Mark M

2016-08-01

The mechanisms by which sepsis triggers intensive care unit acquired weakness (ICUAW) remain unclear. We previously identified difficulty with motor unit recruitment in patients as a novel contributor to ICUAW. To study the mechanism underlying poor recruitment of motor units we used the rat cecal ligation and puncture model of sepsis. We identified striking dysfunction of alpha motor neurons during repetitive firing. Firing was more erratic, and often intermittent. Our data raised the possibility that reduced excitability of motor neurons was a significant contributor to weakness induced by sepsis. In this study we quantified the contribution of reduced motor neuron excitability and compared its magnitude to the contributions of myopathy, neuropathy and failure of neuromuscular transmission. We injected constant depolarizing current pulses (5s) into the soma of alpha motor neurons in the lumbosacral spinal cord of anesthetized rats to trigger repetitive firing. In response to constant depolarization, motor neurons in untreated control rats fired at steady and continuous firing rates and generated smooth and sustained tetanic motor unit force as expected. In contrast, following induction of sepsis, motor neurons were often unable to sustain firing throughout the 5s current injection such that force production was reduced. Even when firing, motor neurons from septic rats fired erratically and discontinuously, leading to irregular production of motor unit force. Both fast and slow type motor neurons had similar disruption of excitability. We followed rats after recovery from sepsis to determine the time course of resolution of the defect in motor neuron excitability. By one week, rats appeared to have recovered from sepsis as they had no piloerection and appeared to be in no distress. The defects in motor neuron repetitive firing were still striking at 2weeks and, although improved, were present at one month. We infer that rats suffered from weakness due to reduced motor neuron excitability for weeks after resolution of sepsis. To assess whether additional contributions from myopathy, neuropathy and defects in neuromuscular transmission contributed to the reduction in force generation, we measured whole-muscle force production in response to electrical stimulation of the muscle nerve. We found no abnormality in force generation that would suggest the presence of myopathy, neuropathy or defective neuromuscular transmission. These data suggest disruption of repetitive firing of motor neurons is an important contributor to weakness induced by sepsis in rats and raise the possibility that reduced motor neuron excitability contributes to disability that persists after resolution of sepsis. Copyright © 2016 Elsevier Inc. All rights reserved.

Vastus lateralis single motor unit EMG at the same absolute torque production at different knee angles.

PubMed

Altenburg, T M; de Haan, A; Verdijk, P W L; van Mechelen, W; de Ruiter, C J

2009-07-01

Single motor unit electromyographic (EMG) activity of the knee extensors was investigated at different knee angles with subjects (n = 10) exerting the same absolute submaximal isometric torque at each angle. Measurements were made over a 20 degrees range around the optimum angle for torque production (AngleTmax) and, where feasible, over a wider range (50 degrees ). Forty-six vastus lateralis (VL) motor units were recorded at 20.7 +/- 17.9 %maximum voluntary contraction (%MVC) together with the rectified surface EMG (rsEMG) of the superficial VL muscle. Due to the lower maximal torque capacity at positions more flexed and extended than AngleTmax, single motor unit recruitment thresholds were expected to decrease and discharge rates were expected to increase at angles above and below AngleTmax. Unexpectedly, the recruitment threshold was higher (P < 0.05) at knee angles 10 degrees more extended (43.7 +/- 22.2 N.m) and not different (P > 0.05) at knee angles 10 degrees more flexed (35.2 +/- 17.9 N.m) compared with recruitment threshold at AngleTmax (41.8 +/- 21.4 N.m). Also, unexpectedly the discharge rates were similar (P > 0.05) at the three angles: 11.6 +/- 2.2, 11.6 +/- 2.1, and 12.3 +/- 2.1 Hz. Similar angle independent discharge rates were also found for 12 units (n = 5; 7.4 +/- 5.4 %MVC) studied over the wider (50 degrees ) range, while recruitment threshold only decreased at more flexed angles. In conclusion, the similar recruitment threshold and discharge behavior of VL motor units during submaximal isometric torque production suggests that net motor unit activation did not change very much along the ascending limb of the knee-angle torque relationship. Several factors such as length-dependent twitch potentiation, which may contribute to this unexpected aspect of motor control, are discussed.

Motor unit number estimation based on high-density surface electromyography decomposition.

PubMed

Peng, Yun; He, Jinbao; Yao, Bo; Li, Sheng; Zhou, Ping; Zhang, Yingchun

2016-09-01

To advance the motor unit number estimation (MUNE) technique using high density surface electromyography (EMG) decomposition. The K-means clustering convolution kernel compensation algorithm was employed to detect the single motor unit potentials (SMUPs) from high-density surface EMG recordings of the biceps brachii muscles in eight healthy subjects. Contraction forces were controlled at 10%, 20% and 30% of the maximal voluntary contraction (MVC). Achieved MUNE results and the representativeness of the SMUP pools were evaluated using a high-density weighted-average method. Mean numbers of motor units were estimated as 288±132, 155±87, 107±99 and 132±61 by using the developed new MUNE at 10%, 20%, 30% and 10-30% MVCs, respectively. Over 20 SMUPs were obtained at each contraction level, and the mean residual variances were lower than 10%. The new MUNE method allows a convenient and non-invasive collection of a large size of SMUP pool with great representativeness. It provides a useful tool for estimating the motor unit number of proximal muscles. The present new MUNE method successfully avoids the use of intramuscular electrodes or multiple electrical stimuli which is required in currently available MUNE techniques; as such the new MUNE method can minimize patient discomfort for MUNE tests. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Recruitment of rat diaphragm motor units across motor behaviors with different levels of diaphragm activation.

PubMed

Seven, Yasin B; Mantilla, Carlos B; Sieck, Gary C

2014-12-01

Phrenic motor neurons are recruited across a range of motor behaviors to generate varying levels of diaphragm muscle (DIAm) force. We hypothesized that DIAm motor units are recruited in a fixed order across a range of motor behaviors of varying force levels, consistent with the Henneman Size Principle. Single motor unit action potentials and compound DIAm EMG activities were recorded in anesthetized, neurally intact rats across different motor behaviors, i.e., eupnea, hypoxia-hypercapnia (10% O2 and 5% CO2), deep breaths, sustained airway occlusion, and sneezing. Central drive [estimated by root-mean-squared (RMS) EMG value 75 ms after the onset of EMG activity (RMS75)], recruitment delay, and onset discharge frequencies were similar during eupnea and hypoxia-hypercapnia. Compared with eupnea, central drive increased (∼25%) during deep breaths, and motor units were recruited ∼12 ms earlier (P < 0.01). During airway occlusion, central drive was ∼3 times greater, motor units were recruited ∼30 ms earlier (P < 0.01), and motor unit onset discharge frequencies were significantly higher (P < 0.01). Recruitment order of motor unit pairs observed during eupnea was maintained for 98%, 87%, and 84% of the same pairs recorded during hypoxia-hypercapnia, deep breaths, and airway occlusion, respectively. Reversals in motor unit recruitment order were observed primarily if motor unit pairs were recruited <20 ms apart. These results are consistent with DIAm motor unit recruitment order being determined primarily by the intrinsic size-dependent electrophysiological properties of phrenic motor neurons. Copyright © 2014 the American Physiological Society.

Recruitment of rat diaphragm motor units across motor behaviors with different levels of diaphragm activation

PubMed Central

Seven, Yasin B.; Mantilla, Carlos B.

2014-01-01

Phrenic motor neurons are recruited across a range of motor behaviors to generate varying levels of diaphragm muscle (DIAm) force. We hypothesized that DIAm motor units are recruited in a fixed order across a range of motor behaviors of varying force levels, consistent with the Henneman Size Principle. Single motor unit action potentials and compound DIAm EMG activities were recorded in anesthetized, neurally intact rats across different motor behaviors, i.e., eupnea, hypoxia-hypercapnia (10% O2 and 5% CO2), deep breaths, sustained airway occlusion, and sneezing. Central drive [estimated by root-mean-squared (RMS) EMG value 75 ms after the onset of EMG activity (RMS75)], recruitment delay, and onset discharge frequencies were similar during eupnea and hypoxia-hypercapnia. Compared with eupnea, central drive increased (∼25%) during deep breaths, and motor units were recruited ∼12 ms earlier (P < 0.01). During airway occlusion, central drive was ∼3 times greater, motor units were recruited ∼30 ms earlier (P < 0.01), and motor unit onset discharge frequencies were significantly higher (P < 0.01). Recruitment order of motor unit pairs observed during eupnea was maintained for 98%, 87%, and 84% of the same pairs recorded during hypoxia-hypercapnia, deep breaths, and airway occlusion, respectively. Reversals in motor unit recruitment order were observed primarily if motor unit pairs were recruited <20 ms apart. These results are consistent with DIAm motor unit recruitment order being determined primarily by the intrinsic size-dependent electrophysiological properties of phrenic motor neurons. PMID:25257864

Speech Motor Development: Integrating Muscles, Movements, and Linguistic Units

ERIC Educational Resources Information Center

Smith, Anne

2006-01-01

A fundamental problem for those interested in human communication is to determine how ideas and the various units of language structure are communicated through speaking. The physiological concepts involved in the control of muscle contraction and movement are theoretically distant from the processing levels and units postulated to exist in…

Failure to expand the motor unit size to compensate for declining motor unit numbers distinguishes sarcopenic from non-sarcopenic older men.

PubMed

Piasecki, M; Ireland, A; Piasecki, J; Stashuk, D W; Swiecicka, A; Rutter, M K; Jones, D A; McPhee, J S

2018-05-01

The age-related loss of muscle mass is related to the loss of innervating motor neurons and denervation of muscle fibres. Not all denervated muscle fibres are degraded; some may be reinnervated by an adjacent surviving neuron, which expands the innervating motor unit proportional to the numbers of fibres rescued. Enlarged motor units have larger motor unit potentials when measured using electrophysiological techniques. We recorded much larger motor unit potentials in relatively healthy older men compared to young men, but the older men with the smallest muscles (sarcopenia) had smaller motor unit potentials than healthy older men. These findings suggest that healthy older men reinnervate large numbers of muscle fibres to compensate for declining motor neuron numbers, but a failure to do so contributes to muscle loss in sarcopenic men. Sarcopenia results from the progressive loss of skeletal muscle mass and reduced function in older age. It is likely to be associated with the well-documented reduction of motor unit numbers innervating limb muscles and the increase in size of surviving motor units via reinnervation of denervated fibres. However, no evidence exists to confirm the extent of motor unit remodelling in sarcopenic individuals. The aim of the present study was to compare motor unit size and number between young (n = 48), non-sarcopenic old (n = 13), pre-sarcopenic (n = 53) and sarcopenic (n = 29) men. Motor unit potentials (MUPs) were isolated from intramuscular and surface EMG recordings. The motor unit numbers were reduced in all groups of old compared with young men (all P < 0.001). MUPs were higher in non-sarcopenic and pre-sarcopenic men compared with young men (P = 0.039 and 0.001 respectively), but not in the vastus lateralis of sarcopenic old (P = 0.485). The results suggest that extensive motor unit remodelling occurs relatively early during ageing, exceeds the loss of muscle mass and precedes sarcopenia. Reinnervation of denervated muscle fibres probably expands the motor unit size in the non-sarcopenic and pre-sarcopenic old, but not in the sarcopenic old. These findings suggest that a failure to expand the motor unit size distinguishes sarcopenic from pre-sarcopenic muscles. © 2018 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Motor unit recruitment by size does not provide functional advantages for motor performance

PubMed Central

Dideriksen, Jakob L; Farina, Dario

2013-01-01

It is commonly assumed that the orderly recruitment of motor units by size provides a functional advantage for the performance of movements compared with a random recruitment order. On the other hand, the excitability of a motor neuron depends on its size and this is intrinsically linked to its innervation number. A range of innervation numbers among motor neurons corresponds to a range of sizes and thus to a range of excitabilities ordered by size. Therefore, if the excitation drive is similar among motor neurons, the recruitment by size is inevitably due to the intrinsic properties of motor neurons and may not have arisen to meet functional demands. In this view, we tested the assumption that orderly recruitment is necessarily beneficial by determining if this type of recruitment produces optimal motor output. Using evolutionary algorithms and without any a priori assumptions, the parameters of neuromuscular models were optimized with respect to several criteria for motor performance. Interestingly, the optimized model parameters matched well known neuromuscular properties, but none of the optimization criteria determined a consistent recruitment order by size unless this was imposed by an association between motor neuron size and excitability. Further, when the association between size and excitability was imposed, the resultant model of recruitment did not improve the motor performance with respect to the absence of orderly recruitment. A consistent observation was that optimal solutions for a variety of criteria of motor performance always required a broad range of innervation numbers in the population of motor neurons, skewed towards the small values. These results indicate that orderly recruitment of motor units in itself does not provide substantial functional advantages for motor control. Rather, the reason for its near-universal presence in human movements is that motor functions are optimized by a broad range of innervation numbers. PMID:24144879

Motor unit recruitment by size does not provide functional advantages for motor performance.

PubMed

Dideriksen, Jakob L; Farina, Dario

2013-12-15

It is commonly assumed that the orderly recruitment of motor units by size provides a functional advantage for the performance of movements compared with a random recruitment order. On the other hand, the excitability of a motor neuron depends on its size and this is intrinsically linked to its innervation number. A range of innervation numbers among motor neurons corresponds to a range of sizes and thus to a range of excitabilities ordered by size. Therefore, if the excitation drive is similar among motor neurons, the recruitment by size is inevitably due to the intrinsic properties of motor neurons and may not have arisen to meet functional demands. In this view, we tested the assumption that orderly recruitment is necessarily beneficial by determining if this type of recruitment produces optimal motor output. Using evolutionary algorithms and without any a priori assumptions, the parameters of neuromuscular models were optimized with respect to several criteria for motor performance. Interestingly, the optimized model parameters matched well known neuromuscular properties, but none of the optimization criteria determined a consistent recruitment order by size unless this was imposed by an association between motor neuron size and excitability. Further, when the association between size and excitability was imposed, the resultant model of recruitment did not improve the motor performance with respect to the absence of orderly recruitment. A consistent observation was that optimal solutions for a variety of criteria of motor performance always required a broad range of innervation numbers in the population of motor neurons, skewed towards the small values. These results indicate that orderly recruitment of motor units in itself does not provide substantial functional advantages for motor control. Rather, the reason for its near-universal presence in human movements is that motor functions are optimized by a broad range of innervation numbers.

High efficiency novel window air conditioner

DOE PAGES

Bansal, Pradeep

2015-07-24

This paper presents the technical development of a high efficiency window air conditioner. In order to achieve higher energy efficiency ratio (EER), the original capacity of the R410A unit was downgraded by replacing the original compressor with a lower capacity but higher EER compressor, while all heat exchangers and the chassis from the original unit were retained. The other subsequent major modifications included – the AC fan motor being replaced with a brushless high efficiency electronically commuted motor (ECM) motor, the capillary tube being replaced with a needle valve to better control the refrigerant flow and refrigerant set points, andmore » R410A being replaced with drop-in environmentally friendly binary mixture of R32 (85% molar concentration)/R125 (15% molar concentration). All these modifications resulted in significant EER enhancement of the modified unit.« less

High efficiency novel window air conditioner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansal, Pradeep

This paper presents the technical development of a high efficiency window air conditioner. In order to achieve higher energy efficiency ratio (EER), the original capacity of the R410A unit was downgraded by replacing the original compressor with a lower capacity but higher EER compressor, while all heat exchangers and the chassis from the original unit were retained. The other subsequent major modifications included – the AC fan motor being replaced with a brushless high efficiency electronically commuted motor (ECM) motor, the capillary tube being replaced with a needle valve to better control the refrigerant flow and refrigerant set points, andmore » R410A being replaced with drop-in environmentally friendly binary mixture of R32 (85% molar concentration)/R125 (15% molar concentration). All these modifications resulted in significant EER enhancement of the modified unit.« less

Distribution of muscle fibre conduction velocity for representative samples of motor units in the full recruitment range of the tibialis anterior muscle.

PubMed

Del Vecchio, A; Negro, F; Felici, F; Farina, D

2018-02-01

Motor units are recruited in an orderly manner according to the size of motor neurones. Moreover, because larger motor neurones innervate fibres with larger diameters than smaller motor neurones, motor units should be recruited orderly according to their conduction velocity (MUCV). Because of technical limitations, these relations have been previously tested either indirectly or in small motor unit samples that revealed weak associations between motor unit recruitment threshold (RT) and MUCV. Here, we analyse the relation between MUCV and RT for large samples of motor units. Ten healthy volunteers completed a series of isometric ankle dorsiflexions at forces up to 70% of the maximum. Multi-channel surface electromyographic signals recorded from the tibialis anterior muscle were decomposed into single motor unit action potentials, from which the corresponding motor unit RT, MUCV and action potential amplitude were estimated. Established relations between muscle fibre diameter and CV were used to estimate the fibre size. Within individual subjects, the distributions of MUCV and fibre diameters were unimodal and did not show distinct populations. MUCV was strongly correlated with RT (mean (SD) R 2  = 0.7 (0.09), P < 0.001; 406 motor units), which supported the hypothesis that fibre diameter is associated with RT. The results provide further evidence for the relations between motor neurone and muscle fibre properties for large samples of motor units. The proposed methodology for motor unit analysis has also the potential to open new perspectives in the study of chronic and acute neuromuscular adaptations to ageing, training and pathology. © 2017 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Autonomous caregiver following robotic wheelchair

NASA Astrophysics Data System (ADS)

Ratnam, E. Venkata; Sivaramalingam, Sethurajan; Vignesh, A. Sri; Vasanth, Elanthendral; Joans, S. Mary

2011-12-01

In the last decade, a variety of robotic/intelligent wheelchairs have been proposed to meet the need in aging society. Their main research topics are autonomous functions such as moving toward some goals while avoiding obstacles, or user-friendly interfaces. Although it is desirable for wheelchair users to go out alone, caregivers often accompany them. Therefore we have to consider not only autonomous functions and user interfaces but also how to reduce caregivers' load and support their activities in a communication aspect. From this point of view, we have proposed a robotic wheelchair moving with a caregiver side by side based on the MATLAB process. In this project we discussing about robotic wheel chair to follow a caregiver by using a microcontroller, Ultrasonic sensor, keypad, Motor drivers to operate robot. Using camera interfaced with the DM6437 (Davinci Code Processor) image is captured. The captured image are then processed by using image processing technique, the processed image are then converted into voltage levels through MAX 232 level converter and given it to the microcontroller unit serially and ultrasonic sensor to detect the obstacle in front of robot. In this robot we have mode selection switch Automatic and Manual control of robot, we use ultrasonic sensor in automatic mode to find obstacle, in Manual mode to use the keypad to operate wheel chair. In the microcontroller unit, c language coding is predefined, according to this coding the robot which connected to it was controlled. Robot which has several motors is activated by using the motor drivers. Motor drivers are nothing but a switch which ON/OFF the motor according to the control given by the microcontroller unit.

Paradigm Shifts in Voluntary Force Control and Motor Unit Behaviors with the Manipulated Size of Visual Error Perception

PubMed Central

Chen, Yi-Ching; Lin, Yen-Ting; Chang, Gwo-Ching; Hwang, Ing-Shiou

2017-01-01

The detection of error information is an essential prerequisite of a feedback-based movement. This study investigated the differential behavior and neurophysiological mechanisms of a cyclic force-tracking task using error-reducing and error-enhancing feedback. The discharge patterns of a relatively large number of motor units (MUs) were assessed with custom-designed multi-channel surface electromyography following mathematical decomposition of the experimentally-measured signals. Force characteristics, force-discharge relation, and phase-locking cortical activities in the contralateral motor cortex to individual MUs were contrasted among the low (LSF), normal (NSF), and high scaling factor (HSF) conditions, in which the sizes of online execution errors were displayed with various amplification ratios. Along with a spectral shift of the force output toward a lower band, force output with a more phase-lead became less irregular, and tracking accuracy was worse in the LSF condition than in the HSF condition. The coherent discharge of high phasic (HP) MUs with the target signal was greater, and inter-spike intervals were larger, in the LSF condition than in the HSF condition. Force-tracking in the LSF condition manifested with stronger phase-locked EEG activity in the contralateral motor cortex to discharge of the (HP) MUs (LSF > NSF, HSF). The coherent discharge of the (HP) MUs during the cyclic force-tracking predominated the force-discharge relation, which increased inversely to the error scaling factor. In conclusion, the size of visualized error gates motor unit discharge, force-discharge relation, and the relative influences of the feedback and feedforward processes on force control. A smaller visualized error size favors voluntary force control using a feedforward process, in relation to a selective central modulation that enhance the coherent discharge of (HP) MUs. PMID:28348530

Paradigm Shifts in Voluntary Force Control and Motor Unit Behaviors with the Manipulated Size of Visual Error Perception.

PubMed

Chen, Yi-Ching; Lin, Yen-Ting; Chang, Gwo-Ching; Hwang, Ing-Shiou

2017-01-01

The detection of error information is an essential prerequisite of a feedback-based movement. This study investigated the differential behavior and neurophysiological mechanisms of a cyclic force-tracking task using error-reducing and error-enhancing feedback. The discharge patterns of a relatively large number of motor units (MUs) were assessed with custom-designed multi-channel surface electromyography following mathematical decomposition of the experimentally-measured signals. Force characteristics, force-discharge relation, and phase-locking cortical activities in the contralateral motor cortex to individual MUs were contrasted among the low (LSF), normal (NSF), and high scaling factor (HSF) conditions, in which the sizes of online execution errors were displayed with various amplification ratios. Along with a spectral shift of the force output toward a lower band, force output with a more phase-lead became less irregular, and tracking accuracy was worse in the LSF condition than in the HSF condition. The coherent discharge of high phasic (HP) MUs with the target signal was greater, and inter-spike intervals were larger, in the LSF condition than in the HSF condition. Force-tracking in the LSF condition manifested with stronger phase-locked EEG activity in the contralateral motor cortex to discharge of the (HP) MUs (LSF > NSF, HSF). The coherent discharge of the (HP) MUs during the cyclic force-tracking predominated the force-discharge relation, which increased inversely to the error scaling factor. In conclusion, the size of visualized error gates motor unit discharge, force-discharge relation, and the relative influences of the feedback and feedforward processes on force control. A smaller visualized error size favors voluntary force control using a feedforward process, in relation to a selective central modulation that enhance the coherent discharge of (HP) MUs.

Properties of single motor units in medial gastrocnemius muscles of adult and old rats.

PubMed Central

Kadhiresan, V A; Hassett, C A; Faulkner, J A

1996-01-01

1. The purpose of this study was to determine the role of motor unit remodelling in the deficit that develops in the maximum isometric tetanic force (Fo) of whole medial gastrocnemius (MGN) muscles in old compared with adult rats. The Fo values and morphological data were determined for MGN muscles and eighty-two single motor units in muscles of adult (10-12 months) and sixty-two units in those of old (24-26 months) F344 rats. During an unfused tetanus, fast and slow (S) motor units were identified by the presence and absence of sag, respectively. Fast-fatigable (FF) and fast-fatigue-resistant (FR) units were classified by fatigue indices less than or greater than 0.50, respectively. 2. For old rats, whole MGN muscle Fo was 29% less than the value of 11.2 N measured for adult rats. The deficit in whole muscle Fo of old rats resulted from equivalent decreases in the number of motor units, 16% smaller than the adult value of ninety-seven, and in the mean motor unit Fo value, 14% less than the adult value of 117 mN. 3. With ageing, little motor unit remodelling occurred in FR units, whereas the S and FF motor units demonstrated dramatic, but opposing, changes. For S units, the number of units remained constant, but the number of fibres per motor unit increased 3-fold from 57 to 165. In contrast, the number of FF units decreased by 34% and the number of fibres per motor unit of the remaining units decreased to 86% of the adult value of 333. The age-related remodelling of motor units appeared to involve denervation of fast muscle fibres with reinnervation of denervated fibres by axonal sprouting from slow fibres. PMID:8782115

Ultra-Compact Motor Controller

NASA Technical Reports Server (NTRS)

Townsend, William T.; Cromwell, Adam; Hauptman, Traveler; Pratt, Gill Andrews

2012-01-01

This invention is an electronically commutated brushless motor contro ller that incorporates Hall-array sensing in a small, 42-gram packag e that provides 4096 absolute counts per motor revolution position s ensing. The unit is the size of a miniature hockey puck, and is a 44 -pin male connector that provides many I/O channels, including CANbus , RS-232 communications, general-purpose analog and digital I/O (GPI O), analog and digital Hall inputs, DC power input (18-90 VDC, 0-l0 A), three-phase motor outputs, and a strain gauge amplifier.

Similarities between GCS and human motor cortex: complex movement coordination

NASA Astrophysics Data System (ADS)

Rodríguez, Jose A.; Macias, Rosa; Molgo, Jordi; Guerra, Dailos

2014-07-01

The "Gran Telescopio de Canarias" (GTC1) is an optical-infrared 10-meter segmented mirror telescope at the ORM observatory in Canary Islands (Spain). The GTC control system (GCS), the brain of the telescope, is is a distributed object & component oriented system based on RT-CORBA and it is responsible for the management and operation of the telescope, including its instrumentation. On the other hand, the Human motor cortex (HMC) is a region of the cerebrum responsible for the coordination of planning, control, and executing voluntary movements. If we analyze both systems, as far as the movement control of their mechanisms and body parts is concerned, we can find extraordinary similarities in their architectures. Both are structured in layers, and their functionalities are comparable from the movement conception until the movement action itself: In the GCS we can enumerate the Sequencer high level components, the Coordination libraries, the Control Kit library and the Device Driver library as the subsystems involved in the telescope movement control. If we look at the motor cortex, we can also enumerate the primary motor cortex, the secondary motor cortices, which include the posterior parietal cortex, the premotor cortex, and the supplementary motor area (SMA), the motor units, the sensory organs and the basal ganglia. From all these components/areas we will analyze in depth the several subcortical regions, of the the motor cortex, that are involved in organizing motor programs for complex movements and the GCS coordination framework, which is composed by a set of classes that allow to the high level components to transparently control a group of mechanisms simultaneously.

Adjustments differ among low-threshold motor units during intermittent, isometric contractions.

PubMed

Farina, Dario; Holobar, Ales; Gazzoni, Marco; Zazula, Damjan; Merletti, Roberto; Enoka, Roger M

2009-01-01

We investigated the changes in muscle fiber conduction velocity, recruitment and derecruitment thresholds, and discharge rate of low-threshold motor units during a series of ramp contractions. The aim was to compare the adjustments in motor unit activity relative to the duration that each motor unit was active during the task. Multichannel surface electromyographic (EMG) signals were recorded from the abductor pollicis brevis muscle of eight healthy men during 12-s contractions (n = 25) in which the force increased and decreased linearly from 0 to 10% of the maximum. The maximal force exhibited a modest decline (8.5 +/- 9.3%; P < 0.05) at the end of the task. The discharge times of 73 motor units that were active for 16-98% of the time during the first five contractions were identified throughout the task by decomposition of the EMG signals. Action potential conduction velocity decreased during the task by a greater amount for motor units that were initially active for >70% of the time compared with that of less active motor units. Moreover, recruitment and derecruitment thresholds increased for these most active motor units, whereas the thresholds decreased for the less active motor units. Another 18 motor units were recruited at an average of 171 +/- 32 s after the beginning of the task. The recruitment and derecruitment thresholds of these units decreased during the task, but muscle fiber conduction velocity did not change. These results indicate that low-threshold motor units exhibit individual adjustments in muscle fiber conduction velocity and motor neuron activation that depended on the relative duration of activity during intermittent contractions.

Motor unit firing rates and synchronisation affect the fractal dimension of simulated surface electromyogram during isometric/isotonic contraction of vastus lateralis muscle.

PubMed

Mesin, Luca; Dardanello, Davide; Rainoldi, Alberto; Boccia, Gennaro

2016-12-01

During fatiguing contractions, many adjustments in motor units behaviour occur: decrease in muscle fibre conduction velocity; increase in motor units synchronisation; modulation of motor units firing rate; increase in variability of motor units inter-spike interval. We simulated the influence of all these adjustments on synthetic EMG signals in isometric/isotonic conditions. The fractal dimension of the EMG signal was found mainly influenced by motor units firing behaviour, being affected by both firing rate and synchronisation level, and least affected by muscle fibre conduction velocity. None of the calculated EMG indices was able to discriminate between firing rate and motor units synchronisation. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Isometric contractions of motor units in a fast twitch muscle of the cat

PubMed Central

Bagust, J.; Knott, Sarah; Lewis, D. M.; Luck, J. C.; Westerman, R. A.

1973-01-01

1. Isosmetric contractions of cat flexor digitorum longus whole muscles and of functionally isolated motor units have been measured under conditions similar to those used by Buller & Lewis (1965a). 2. Motor unit twitch time to peak was inversely related to axonal conduction velocity. The logarithm of tetanic tension was directly related to conduction velocity. These relationships suggest that each motoneurone has an influence on the muscle fibres which it innervates. 3. The ratio of twitch to tetanic tension was directly related to the time to peak of the motor unit. This fact might be explained by variation between motor units of the duration of `active state'. 4. The muscle length at which tension was maximal varied between motor units and the optima were found over the range of muscle lengths which could occur in the body. Slow motor units had longer optimal lengths. 5. The sample of motor units was considered to be unbiased because the distribution of axon conduction velocities was compatible with reported motor fibre diameter spectra of the muscle nerve. The mean motor unit tetanic tension gave a reasonable estimate of the number of α-motor axons in the muscle nerve. Twitch tensions gave a value that was 40% higher. 6. Motor unit and whole muscle data were in good agreement for length-tetanus tension curves, for times to peak and for twitch-tetanus ratios at long muscle lengths. PMID:4715372

Recruitment and derecruitment characteristics of motor units in a hand muscle of young and old adults.

PubMed

Jesunathadas, Mark; Marmon, Adam R; Gibb, James M; Enoka, Roger M

2010-06-01

The significant decline in motor neuron number after approximately 60 yr of age is accompanied by a remodeling of the neuromuscular system so that average motor unit force increases and the ability of old adults to produce an intended force declines. One possible explanation for the loss of movement precision is that the remodeling increases the difference in recruitment forces between successively recruited motor units in old adults and this augments force variability at motor unit recruitment. The purpose of the study was to compare the forces and discharge characteristics of motor units in a hand muscle of young and old adults at motor unit recruitment and derecruitment. The difference in recruitment force between pairs of motor units did not differ between young (n=54) and old adults (n=56; P=0.702). However, old adults had a greater proportion of contractions in which motor units discharged action potentials transiently before discharging continuously during the ramp increase in force (young: 0.32; old: 0.41; P=0.045). Force variability at motor unit recruitment was greater for old adults compared with young adults (Por=0.729). These results suggest that the difference in force between the recruitment of successive motor units does not differ between age groups, but that motor unit recruitment may be more transient and could contribute to the greater variability in force observed in old adults during graded ramp contractions.

The design of RFID convey or belt gate systems using an antenna control unit.

PubMed

Park, Chong Ryol; Lee, Seung Joon; Eom, Ki Hwan

2011-01-01

This paper proposes an efficient management system utilizing a Radio Frequency Identification (RFID) antenna control unit which is moving along with the path of boxes of materials on the conveyor belt by manipulating a motor. The proposed antenna control unit, which is driven by a motor and is located on top of the gate, has an array structure of two antennas with parallel connection. The array structure helps improve the directivity of antenna beam pattern and the readable RFID distance due to its configuration. In the experiments, as the control unit follows moving materials, the reading time has been improved by almost three-fold compared to an RFID system employing conventional fixed antennas. The proposed system also has a recognition rate of over 99% without additional antennas for detecting the sides of a box of materials. The recognition rate meets the conditions recommended by the Electronic Product Code glbal network (EPC)global for commercializing the system, with three antennas at a 20 dBm power of reader and a conveyor belt speed of 3.17 m/s. This will enable a host of new RFID conveyor belt gate systems with increased performance.

The Design of RFID Convey or Belt Gate Systems Using an Antenna Control Unit

PubMed Central

Park, Chong Ryol; Lee, Seung Joon; Eom, Ki Hwan

2011-01-01

This paper proposes an efficient management system utilizing a Radio Frequency Identification (RFID) antenna control unit which is moving along with the path of boxes of materials on the conveyor belt by manipulating a motor. The proposed antenna control unit, which is driven by a motor and is located on top of the gate, has an array structure of two antennas with parallel connection. The array structure helps improve the directivity of antenna beam pattern and the readable RFID distance due to its configuration. In the experiments, as the control unit follows moving materials, the reading time has been improved by almost three-fold compared to an RFID system employing conventional fixed antennas. The proposed system also has a recognition rate of over 99% without additional antennas for detecting the sides of a box of materials. The recognition rate meets the conditions recommended by the Electronic Product Code glbal network (EPC)global for commercializing the system, with three antennas at a 20 dBm power of reader and a conveyor belt speed of 3.17 m/s. This will enable a host of new RFID conveyor belt gate systems with increased performance. PMID:22164119

The perceptual shaping of anticipatory actions.

PubMed

Maffei, Giovanni; Herreros, Ivan; Sanchez-Fibla, Marti; Friston, Karl J; Verschure, Paul F M J

2017-12-20

Humans display anticipatory motor responses to minimize the adverse effects of predictable perturbations. A widely accepted explanation for this behaviour relies on the notion of an inverse model that, learning from motor errors, anticipates corrective responses. Here, we propose and validate the alternative hypothesis that anticipatory control can be realized through a cascade of purely sensory predictions that drive the motor system, reflecting the causal sequence of the perceptual events preceding the error. We compare both hypotheses in a simulated anticipatory postural adjustment task. We observe that adaptation in the sensory domain, but not in the motor one, supports the robust and generalizable anticipatory control characteristic of biological systems. Our proposal unites the neurobiology of the cerebellum with the theory of active inference and provides a concrete implementation of its core tenets with great relevance both to our understanding of biological control systems and, possibly, to their emulation in complex artefacts. © 2017 The Author(s).

Dependence of the paired motor unit analysis on motor unit discharge characteristics in the human tibialis anterior muscle

PubMed Central

Stephenson, Jennifer L.; Maluf, Katrina S.

2011-01-01

The paired motor unit analysis provides in vivo estimates of the magnitude of persistent inward currents (PIC) in human motoneurons by quantifying changes in the firing rate (ΔF) of an earlier recruited (reference) motor unit at the time of recruitment and derecruitment of a later recruited (test) motor unit. This study assessed the variability of ΔF estimates, and quantified the dependence of ΔF on the discharge characteristics of the motor units selected for analysis. ΔF was calculated for 158 pairs of motor units recorded from nine healthy individuals during repeated submaximal contractions of the tibialis anterior muscle. The mean (SD) ΔF was 3.7 (2.5) pps (range −4.2 to 8.9 pps). The median absolute difference in ΔF for the same motor unit pair across trials was 1.8 pps, and the minimal detectable change in ΔF required to exceed measurement error was 4.8 pps. ΔF was positively related to the amount of discharge rate modulation in the reference motor unit (r2=0.335; P<0.001), and inversely related to the rate of increase in discharge rate (r2=0.125; P<0.001). A quadratic function provided the best fit for relations between ΔF and the time between recruitment of the reference and test motor units (r2=0.229, P<0.001), the duration of test motor unit activity (r2=0.110, P<0.001), and the recruitment threshold of the test motor unit (r2=0.237, P<0.001). Physiological and methodological contributions to the variability in ΔF estimates of PIC magnitude are discussed, and selection criteria to reduce these sources of variability are suggested for the paired motor unit analysis. PMID:21459110

Motor unit activity after eccentric exercise and muscle damage in humans.

PubMed

Semmler, J G

2014-04-01

It is well known that unaccustomed eccentric exercise leads to muscle damage and soreness, which can produce long-lasting effects on muscle function. How this muscle damage influences muscle activation is poorly understood. The purpose of this brief review is to highlight the effect of eccentric exercise on the activation of muscle by the nervous system, by examining the change in motor unit activity obtained from surface electromyography (EMG) and intramuscular recordings. Previous research shows that eccentric exercise produces unusual changes in the EMG–force relation that influences motor performance during isometric, shortening and lengthening muscle contractions and during fatiguing tasks. When examining the effect of eccentric exercise at the single motor unit level, there are substantial changes in recruitment thresholds, discharge rates, motor unit conduction velocities and synchronization, which can last for up to 1 week after eccentric exercise. Examining the time course of these changes suggests that the increased submaximal EMG after eccentric exercise most likely occurs through a decrease in motor unit conduction velocity and an increase in motor unit activity related to antagonist muscle coactivation and low-frequency fatigue. Furthermore, there is a commonly held view that eccentric exercise produces preferential damage to high-threshold motor units, but the evidence for this in humans is limited. Further research is needed to establish whether there is preferential damage to high-threshold motor units after eccentric exercise in humans, preferably by linking changes in motor unit activity with estimates of motor unit size using selective intramuscular recording techniques.

Spinal inhibition and motor function in adults with spastic cerebral palsy

PubMed Central

Condliffe, E. G.; Jeffery, D. T.; Emery, D. J.

2016-01-01

Key points Abnormal activation of motoneurons in the spinal cord by sensory pathways is thought to contribute to impaired movement control and spasticity in individuals with cerebral palsy.Here we use single motor unit recordings to show how individual motoneurons in the spinal cord respond to sensory inputs in a group of participants with cerebral palsy having different degrees of motor dysfunction.In participants who had problems walking independently and required assistive devices such as wheelchairs, sensory pathways only excited motoneurons in the spinal cord.In contrast, in participants with cerebral palsy who walked independently for long distances, sensory inputs both inhibited and excited motoneurons in the spinal cord, similar to what we found in uninjured control participants.These findings demonstrate that in individuals with severe cerebral palsy, inhibitory control of motoneurons from sensory pathways is reduced and may contribute to motor dysfunction and spasticity. Abstract Reduced inhibition of spinal motoneurons by sensory pathways may contribute to heightened reflex activity, spasticity and impaired motor function in individuals with cerebral palsy (CP). To measure if the activation of inhibitory post‐synaptic potentials (IPSPs) by sensory inputs is reduced in CP, the tonic discharge rate of single motor units from the soleus muscle was plotted time‐locked to the occurrence of a sensory stimulation to produce peri‐stimulus frequencygrams (PSFs). Stimulation to the medial arch of the foot was used to activate cutaneomuscular afferents in 17 adults with bilateral spastic CP and 15 neurologically intact (NI) peers. Evidence of IPSP activation from the PSF profiles, namely a marked pause or reduction in motor unit firing rates at the onset of the cutaneomuscular reflex, was found in all NI participants but in only half of participants with CP. In the other half of the participants with CP, stimulation of cutaneomuscular afferents produced a PSF profile indicative of a pure excitatory post‐synaptic potential, with firing rates increasing above the mean pre‐stimulus rate for 300 ms or more. The amplitude of motoneuron inhibition during the period of IPSP activation, as measured from the surface EMG, was less in participants with poor motor function as evaluated with the Gross Motor Functional Classification System (r = 0.72, P < 0.001) and the Functional Mobility Scale (r = −0.82, P < 0.001). These findings demonstrate that in individuals with CP, reduced activation of motoneuron IPSPs by sensory inputs is associated with reduced motor function and may contribute to enhanced reflexes and spasticity in CP. PMID:26842905

The effect of fast and slow motor unit activation on whole-muscle mechanical performance: the size principle may not pose a mechanical paradox

PubMed Central

Holt, N. C.; Wakeling, J. M.; Biewener, A. A.

2014-01-01

The output of skeletal muscle can be varied by selectively recruiting different motor units. However, our knowledge of muscle function is largely derived from muscle in which all motor units are activated. This discrepancy may limit our understanding of in vivo muscle function. Hence, this study aimed to characterize the mechanical properties of muscle with different motor unit activation. We determined the isometric properties and isotonic force–velocity relationship of rat plantaris muscles in situ with all of the muscle active, 30% of the muscle containing predominately slower motor units active or 20% of the muscle containing predominately faster motor units active. There was a significant effect of active motor unit type on isometric force rise time (p < 0.001) and the force–velocity relationship (p < 0.001). Surprisingly, force rise time was longer and maximum shortening velocity higher when all motor units were active than when either fast or slow motor units were selectively activated. We propose this is due to the greater relative effects of factors such as series compliance and muscle resistance to shortening during sub-maximal contractions. The findings presented here suggest that recruitment according to the size principle, where slow motor units are activated first and faster ones recruited as demand increases, may not pose a mechanical paradox, as has been previously suggested. PMID:24695429

The effect of fast and slow motor unit activation on whole-muscle mechanical performance: the size principle may not pose a mechanical paradox.

PubMed

Holt, N C; Wakeling, J M; Biewener, A A

2014-05-22

The output of skeletal muscle can be varied by selectively recruiting different motor units. However, our knowledge of muscle function is largely derived from muscle in which all motor units are activated. This discrepancy may limit our understanding of in vivo muscle function. Hence, this study aimed to characterize the mechanical properties of muscle with different motor unit activation. We determined the isometric properties and isotonic force-velocity relationship of rat plantaris muscles in situ with all of the muscle active, 30% of the muscle containing predominately slower motor units active or 20% of the muscle containing predominately faster motor units active. There was a significant effect of active motor unit type on isometric force rise time (p < 0.001) and the force-velocity relationship (p < 0.001). Surprisingly, force rise time was longer and maximum shortening velocity higher when all motor units were active than when either fast or slow motor units were selectively activated. We propose this is due to the greater relative effects of factors such as series compliance and muscle resistance to shortening during sub-maximal contractions. The findings presented here suggest that recruitment according to the size principle, where slow motor units are activated first and faster ones recruited as demand increases, may not pose a mechanical paradox, as has been previously suggested.

Safety Aspects of Postanesthesia Care Unit Discharge without Motor Function Assessment after Spinal Anesthesia: A Randomized, Multicenter, Semiblinded, Noninferiority, Controlled Trial.

PubMed

Aasvang, Eske Kvanner; Jørgensen, Christoffer Calov; Laursen, Mogens Berg; Madsen, Jacob; Solgaard, Søren; Krøigaard, Mogens; Kjærsgaard-Andersen, Per; Mandøe, Hans; Hansen, Torben Bæk; Nielsen, Jørgen Ulrich; Krarup, Niels; Skøtt, Annette Elisabeth; Kehlet, Henrik

2017-06-01

Postanesthesia care unit (PACU) discharge without observation of lower limb motor function after spinal anesthesia has been suggested to significantly reduce PACU stay and enhance resource optimization and early rehabilitation but without enough data to allow clinical recommendations. A multicenter, semiblinded, noninferiority randomized controlled trial of discharge from the PACU with or without assessment of lower limb motor function after elective total hip or knee arthroplasty under spinal anesthesia was undertaken. The primary outcome was frequency of a successful fast-track course (length of stay 4 days or less and no 30-day readmission). Noninferiority would be declared if the odds ratio (OR) for a successful fast-track course was no worse for those patients receiving no motor function assessment versus those patients receiving motor function assessment by OR = 0.68. A total of 1,359 patients (98.8% follow-up) were available for analysis (93% American Society of Anesthesiologists class 1 to 2). The primary outcome occurred in 92.2% and 92.0%, corresponding to no motor function assessment being noninferior to motor function assessment with OR 0.97 (95% CI, 0.70 to 1.35). Adverse events in the ward during the first 24 h occurred in 5.8% versus 7.4% with or without motor function assessment, respectively (OR, 0.77; 95% CI, 0.5 to 1.19, P = 0.24). PACU discharge without assessment of lower limb motor function after spinal anesthesia for total hip or knee arthroplasty was noninferior to motor function assessment in achieving length of stay 4 days or less or 30-day readmissions. Because a nonsignificant tendency toward increased adverse events during the first 24 h in the ward was discovered, further safety data are needed in patients without assessment of lower limb motor function before PACU discharge.

Female pheromones modulate flight muscle activation patterns during preflight warm-up.

PubMed

Crespo, José G; Vickers, Neil J; Goller, Franz

2013-08-01

At low ambient temperature Helicoverpa zea male moths engage in warm-up behavior prior to taking flight in response to an attractive female pheromone blend. Male H. zea warm up at a faster rate when sensing the attractive pheromone blend compared with unattractive blends or blank controls (Crespo et al. 2012), but the mechanisms involved in this olfactory modulation of the heating rate during preflight warm-up are unknown. Here, we test three possible mechanisms for increasing heat production: 1) increased rate of muscle contraction; 2) reduction in mechanical movement by increased overlap in activation of the antagonistic flight muscles; and 3) increased activation of motor units. To test which mechanisms play a role, we simultaneously recorded electrical activation patterns of the main flight muscles (dorsolongitudinal and dorsoventral muscles), wing movement, and thoracic temperature in moths exposed to both the attractive pheromone blend and a blank control. Results indicate that the main mechanism responsible for the observed increase in thoracic heating rate with pheromone stimulation is the differential activation of motor units during each muscle contraction cycle in both antagonistic flight muscles. This additional activation lengthens the contracted state within each cycle and thus accounts for the greater heat production. Interestingly, the rate of activation (frequency of contraction cycles) of motor units, which is temperature dependent, did not vary between treatments. This result suggests that the activation rate is determined by a temperature-dependent oscillator, which is not affected by the olfactory stimulus, but activation of motor units is modulated during each cycle.

Female pheromones modulate flight muscle activation patterns during preflight warm-up

PubMed Central

Vickers, Neil J.; Goller, Franz

2013-01-01

At low ambient temperature Helicoverpa zea male moths engage in warm-up behavior prior to taking flight in response to an attractive female pheromone blend. Male H. zea warm up at a faster rate when sensing the attractive pheromone blend compared with unattractive blends or blank controls (Crespo et al. 2012), but the mechanisms involved in this olfactory modulation of the heating rate during preflight warm-up are unknown. Here, we test three possible mechanisms for increasing heat production: 1) increased rate of muscle contraction; 2) reduction in mechanical movement by increased overlap in activation of the antagonistic flight muscles; and 3) increased activation of motor units. To test which mechanisms play a role, we simultaneously recorded electrical activation patterns of the main flight muscles (dorsolongitudinal and dorsoventral muscles), wing movement, and thoracic temperature in moths exposed to both the attractive pheromone blend and a blank control. Results indicate that the main mechanism responsible for the observed increase in thoracic heating rate with pheromone stimulation is the differential activation of motor units during each muscle contraction cycle in both antagonistic flight muscles. This additional activation lengthens the contracted state within each cycle and thus accounts for the greater heat production. Interestingly, the rate of activation (frequency of contraction cycles) of motor units, which is temperature dependent, did not vary between treatments. This result suggests that the activation rate is determined by a temperature-dependent oscillator, which is not affected by the olfactory stimulus, but activation of motor units is modulated during each cycle. PMID:23699056

Universal Controller for Spacecraft Mechanisms

NASA Technical Reports Server (NTRS)

Levanas, Greg; McCarthy, Thomas; Hunter, Don; Buchanan, Christine; Johnson, Michael; Cozy, Raymond; Morgan, Albert; Tran, Hung

2006-01-01

An electronic control unit has been fabricated and tested that can be replicated as a universal interface between the electronic infrastructure of a spacecraft and a brushless-motor (or other electromechanical actuator) driven mechanism that performs a specific mechanical function within the overall spacecraft system. The unit includes interfaces to a variety of spacecraft sensors, power outputs, and has selectable actuator control parameters making the assembly a mechanism controller. Several control topologies are selectable and reconfigurable at any time. This allows the same actuator to perform different functions during the mission life of the spacecraft. The unit includes complementary metal oxide/semiconductor electronic components on a circuit board of a type called rigid flex (signifying flexible printed wiring along with a rigid substrate). The rigid flex board is folded to make the unit fit into a housing on the back of a motor. The assembly has redundant critical interfaces, allowing the controller to perform time-critical operations when no human interface with the hardware is possible. The controller is designed to function over a wide temperature range without the need for thermal control, including withstanding significant thermal cycling, making it usable in nearly all environments that spacecraft or landers will endure. A prototype has withstood 1,500 thermal cycles between 120 and +85 C without significant deterioration of its packaging or electronic function. Because there is no need for thermal control and the unit is addressed through a serial bus interface, the cabling and other system hardware are substantially reduced in quantity and complexity, with corresponding reductions in overall spacecraft mass and cost.

Outboard Repair.

ERIC Educational Resources Information Center

Hardway, Jack

This consortium-developed instructor's manual for small engine repair (with focus on outboard motors) consists of the following nine instructional units: electrical remote control assembly, mechanical remote control assembly, tilt assemblies, exhaust housing, propeller and trim tabs, cooling system, mechanical gearcase, electrical gearcase, and…

Non-Stationarity and Power Spectral Shifts in EMG Activity Reflect Motor Unit Recruitment in Rat Diaphragm Muscle

PubMed Central

Seven, Yasin B.; Mantilla, Carlos B.; Zhan, Wen-Zhi; Sieck, Gary C.

2012-01-01

We hypothesized that diaphragm muscle (DIAm) by a shift in the EMG power spectral density (PSD) to higher frequencies reflects recruitment of more fatigable fast-twitch motor units and motor unit recruitment is reflected by EMG non-stationarity. DIAm EMG was recorded in anesthetized rats during eupnea, hypoxia-hypercapnia (10% O2-5% CO2), airway occlusion, and sneezing (maximal DIAm force). Although power in all frequency bands increased progressively across motor behaviors, PSD centroid frequency increased only during sneezing (p<0.05). The non-stationary period at the onset of EMG activity ranged from ~70 ms during airway occlusion to ~150 ms during eupnea. Within the initial non-stationary period of EMG activity 80–95% of motor units were recruited during different motor behaviors. Motor units augmented their discharge frequencies progressively beyond the non-stationary period; yet, EMG signal became stationary. In conclusion, non-stationarity of DIAm EMG reflects the period of motor unit recruitment, while a shift in the PSD towards higher frequencies reflects recruitment of more fatigable fast-twitch motor units. PMID:22986086

Gamma loop contributing to maximal voluntary contractions in man.

PubMed Central

Hagbarth, K E; Kunesch, E J; Nordin, M; Schmidt, R; Wallin, E U

1986-01-01

A local anaesthetic drug was injected around the peroneal nerve in healthy subjects in order to investigate whether the resulting loss in foot dorsiflexion power in part depended on a gamma-fibre block preventing 'internal' activation of spindle end-organs and thereby depriving the alpha-motoneurones of an excitatory spindle inflow during contraction. The motor outcome of maximal dorsiflexion efforts was assessed by measuring firing rates of individual motor units in the anterior tibial (t.a.) muscle, mean voltage e.m.g. from the pretibial muscles, dorsiflexion force and range of voluntary foot dorsiflexion movements. The tests were performed with and without peripheral conditioning stimuli, such as agonist or antagonist muscle vibration or imposed stretch of the contracting muscles. As compared to control values of t.a. motor unit firing rates in maximal isometric voluntary contractions, the firing rates were lower and more irregular during maximal dorsiflexion efforts performed during subtotal peroneal nerve blocks. During the development of paresis a gradual reduction of motor unit firing rates was observed before the units ceased responding to the voluntary commands. This change in motor unit behaviour was accompanied by a reduction of the mean voltage e.m.g. activity in the pretibial muscles. At a given stage of anaesthesia the e.m.g. responses to maximal voluntary efforts were more affected than the responses evoked by electric nerve stimuli delivered proximal to the block, indicating that impaired impulse transmission in alpha motor fibres was not the sole cause of the paresis. The inability to generate high and regular motor unit firing rates during peroneal nerve blocks was accentuated by vibration applied over the antagonistic calf muscles. By contrast, in eight out of ten experiments agonist stretch or vibration caused an enhancement of motor unit firing during the maximal force tasks. The reverse effects of agonist and antagonist vibration on the ability to activate the paretic muscles were evidenced also by alterations induced in mean voltage e.m.g. activity, dorsiflexion force and range of dorsiflexion movements. The autogenetic excitatory and the reciprocal inhibitory effects of muscle vibration rose in strength as the vibration frequency was raised from 90 to 165 Hz. Reflex effects on maximal voluntary contraction strength similar to those observed during partial nerve blocks were not seen under normal conditions when the nerve supply was intact.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3612576

Motor Unit Changes Seen With Skeletal Muscle Sarcopenia in Oldest Old Rats

PubMed Central

Kung, Theodore A.; van der Meulen, Jack H.; Urbanchek, Melanie G.; Kuzon, William M.; Faulkner, John A.

2014-01-01

Sarcopenia leads to many changes in skeletal muscle that contribute to atrophy, force deficits, and subsequent frailty. The purpose of this study was to characterize motor unit remodeling related to sarcopenia seen in extreme old age. Whole extensor digitorum longus muscle and motor unit contractile properties were measured in 19 adult (11–13 months) and 12 oldest old (36–37 months) Brown-Norway rats. Compared with adults, oldest old rats had significantly fewer motor units per muscle, smaller muscle cross-sectional area, and lower muscle specific force. However, mean motor unit force generation was similar between the two groups due to an increase in innervation ratio by the oldest old rats. These findings suggest that even in extreme old age both fast- and slow-twitch motor units maintain the ability to undergo motor unit remodeling that offsets some effects of sarcopenia. PMID:24077596

A Tactile Stimulator for Studying Passive Shape Perception

PubMed Central

Lane, John W.; Fitzgerald, Paul J.; Yau, Jeffrey M.; Pembeci, Izzet; Hsiao, Steven S.

2009-01-01

We describe a computer-controlled tactile stimulator for use in human psychophysical and monkey neurophysiological studies of 3-D shape perception. The stimulator is constructed primarily of commercially available parts, as well as a few custom-built pieces for which we will supply diagrams upon request. There are two components to the stimulator: a tactile component and a hand positioner component. The tactile component consists of multiple stimulating units that move about in a Cartesian plane above the restrained hand. Each stimulating unit contains a servo-controlled linear motor with an attached small rotary stepper motor, allowing arbitrary stimulus shapes to contact the skin through vibration, static indentation, or scanning. The hand positioner component modifies the conformation of the restrained hand through a set of mechanical linkages under motorized control. The present design controls the amount of spread between digits two and three, the spread between digits four and three, and the degree to which digit three is flexed or extended, thereby simulating different conformations of the hand in contact with objects. This design is easily modified to suit the needs of the experimenter. Because the two components of the stimulator are independently controlled, the stimulator allows for parametric study of the mechanoreceptive and proprioceptive contributions to 3-D tactile shape perception. PMID:19800916

RELATIONSHIP BETWEEN LINGUISTIC UNITS AND MOTOR COMMANDS.

ERIC Educational Resources Information Center

FROMKIN, VICTORIA A.

ASSUMING THAT SPEECH IS THE RESULT OF A NUMBER OF DISCRETE NEUROMUSCULAR EVENTS AND THAT THE BRAIN CAN STORE ONLY A LIMITED NUMBER OF MOTOR COMMANDS WITH WHICH TO CONTROL THESE EVENTS, THE RESEARCH REPORTED IN THIS PAPER WAS DIRECTED TO A DETERMINATION OF THE SIZE AND NATURE OF THE STORED ITEMS AND AN EXPLANATION OF HOW SPEAKERS ENCODE A SEQUENCE…

Adult mouse motor units develop almost all of their force in the subprimary range: a new all-or-none strategy for force recruitment?

PubMed

Manuel, Marin; Heckman, C J

2011-10-19

Classical studies of the mammalian neuromuscular system have shown an impressive adaptation match between the intrinsic properties of motoneurons and the contractile properties of their motor units. In these studies, the rate at which motoneurons start to fire repetitively corresponds to the rate at which individual twitches start to sum, and the firing rate increases linearly with the amount of excitation ("primary range") up to the point where the motor unit develops its maximal force. This allows for the gradation of the force produced by a motor unit by rate modulation. In adult mouse motoneurons, however, we recently described a regime of firing ("subprimary range") that appears at lower excitation than what is required for the primary range, a finding that might challenge the classical conception. To investigate the force production of mouse motor units, we simultaneously recorded, for the first time, the motoneuron discharge elicited by intracellular ramps of current and the force developed by its motor unit. We showed that the motor unit developed nearly its maximal force during the subprimary range. This was found to be the case regardless of the input resistance of the motoneuron, the contraction speed, or the tetanic force of the motor unit. Our work suggests that force modulation in small mammals mainly relies on the number of motor units that are recruited rather than on rate modulation of individual motor units.

Duration of motor block with intrathecal ropivacaine versus bupivacaine for caesarean section: a meta-analysis.

PubMed

Malhotra, R; Johnstone, C; Halpern, S; Hunter, J; Banerjee, A

2016-08-01

Bupivacaine is a commonly used local anaesthetic for spinal anaesthesia for caesarean section, but may produce prolonged motor block, delaying discharge from the post-anaesthesia care unit. Ropivacaine may have a shorter time to recovery of motor function compared with bupivacaine. We performed a meta-analysis to assess the time difference in duration of motor block with intrathecal ropivacaine compared with bupivacaine for caesarean section. We searched MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials databases for randomised controlled trials comparing ropivacaine with bupivacaine in parturients undergoing elective caesarean section under spinal anaesthesia. The primary outcome was the duration of motor block. Secondary outcomes included the time to onset of sensory block, need for conversion to general anaesthesia and the incidence of hypotension. Thirteen trials comprising 743 spinal anaesthetics were included. Intrathecal ropivacaine resulted in a reduced duration of motor block, regressing 35.7min earlier compared with intrathecal bupivacaine (P<0.00001). There was no difference in the time to onset of sensory block (P=0.25) or the incidence of hypotension (P=0.10). Limited data suggested no difference in the rate of conversion to general anaesthesia, but an earlier request for postoperative analgesia with ropivacaine. Compared with bupivacaine, intrathecal ropivacaine is associated with more rapid recovery of motor block despite similar sensory properties and no increased rate of conversion to general anaesthesia. This may be useful in centres in which recovery of motor block is a criterion for discharge from the post-anaesthesia care unit. However, small numbers of trials and significant heterogeneity limit the interpretation of our results. Copyright © 2016 Elsevier Ltd. All rights reserved.

Periodic modulation of motor-unit activity in extrinsic hand muscles during multidigit grasping.

PubMed

Johnston, Jamie A; Winges, Sara A; Santello, Marco

2005-07-01

We recently examined the extent to which motor units of digit flexor muscles receive common input during multidigit grasping. This task elicited moderate to strong motor-unit synchrony (common input strength, CIS) across muscles (flexor digitorum profundus, FDP, and flexor pollicis longus, FPL) and across FDP muscle compartments, although the strength of this common input was not uniform across digit pairs. To further characterize the neural mechanisms underlying the control of multidigit grasping, we analyzed the relationship between firing of single motor units from these hand muscles in the frequency domain by computing coherence. We report three primary findings. First, in contrast to what has been reported in intrinsic hand muscles, motor units belonging to different muscles and muscle compartments of extrinsic digit flexors exhibited significant coherence in the 0- to 5- and 5- to 10-Hz frequency ranges and much weaker coherence in the higher 10-20 Hz range (maximum 0.0025 and 0.0008, respectively, pooled across all FDP compartment pairs). Second, the strength and incidence of coherence differed considerably across digit pairs. Third, contrary to what has been reported in the literature, across-muscle coherence can be stronger and more prevalent than within-muscle coherence, as FPL-FDP2 (thumb-index digit pair) exhibited the strongest and most prevalent coherence in our data (0.010 and 43% at 3 Hz, respectively). The heterogeneous organization of common input to these muscles and muscle compartments is discussed in relation to the functional role of individual digit pairs in the coordination of multiple digit forces in grasping.

Low speed phaselock speed control system. [for brushless dc motor

NASA Technical Reports Server (NTRS)

Fulcher, R. W.; Sudey, J. (Inventor)

1975-01-01

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

Development of Permanent Magnet Synchronous Motor Control System for the Traction Purpose of the Gauge Changing Train

NASA Astrophysics Data System (ADS)

Kondo, Keiichiro; Hata, Hiroshi; Yuki, Kazuaki; Naganuma, Katsunori; Matsuoka, Koichi; Hasebe, Toshio

This paper is aimed at providing the designing method of a permanent magnet synchronous motor (PMSM) control system for the high-speed and the single-phase AC powered Gauge Changing Train (GCT). The state-of-the-art electrical motive unit is equipped with downsized direct drive type PMSMs for the simplified gauge changeable truck. Due to the feeding the AC single phase power, we propose a beat-less control for PMSMs. We verify the development results of designing procedures by the experimental results of operation on a high-speed test line in Colorado, USA.

Recruitment and rate coding organisation for soleus motor units across entire range of voluntary isometric plantar flexions.

PubMed

Oya, Tomomichi; Riek, Stephan; Cresswell, Andrew G

2009-10-01

Unlike upper limb muscles, it remains undocumented as to how motor units in the soleus muscle are organised in terms of recruitment range and discharge rates with respect to their recruitment and de-recruitment thresholds. The possible influence of neuromodulation, such as persistent inward currents (PICs) on lower limb motor unit recruitment and discharge rates has also yet to be reported. To address these issues, electromyographic (EMG) activities from the soleus muscle were recorded using selective branched-wire intramuscular electrodes during ramp-and-hold contractions with intensities up to maximal voluntary contraction (MVC). The multiple single motor unit activities were then derived using a decomposition technique. The onset-offset hysteresis of motor unit discharge, i.e. a difference between recruitment and de-recruitment thresholds, as well as PIC magnitude calculated by a paired motor unit analysis were used to examine the neuromodulatory effects on discharge behaviours, such as minimum firing rate, peak firing rate and degree of increase in firing rate. Forty-two clearly identified motor units from five subjects revealed that soleus motor units are recruited progressively from rest to contraction strengths close to 95% of MVC, with low-threshold motor units discharging action potentials slower at their recruitment and with a lower peak rate than later recruited high-threshold units. This observation is in contrast to the 'onion skin phenomenon' often reported for the upper limb muscles. Based on positive correlations of the peak discharge rates, initial rates and recruitment order of the units with the magnitude of the onset-offset hysteresis and not PIC contribution, we conclude that discharge behaviours among motor units appear to be related to a variation in an intrinsic property other than PICs.

Brief post-surgical electrical stimulation accelerates axon regeneration and muscle reinnervation without affecting the functional measures in carpal tunnel syndrome patients.

PubMed

Gordon, Tessa; Amirjani, Nasim; Edwards, David C; Chan, K Ming

2010-05-01

Electrical stimulation (ES) of injured peripheral nerves accelerates axonal regeneration in laboratory animals. However, clinical applicability of this intervention has never been investigated in human subjects. The aim of this pilot study was to determine the effect of ES on axonal regeneration after surgery in patients with median nerve compression in the carpal tunnel causing marked motor axonal loss. A randomized control trial was conducted to provide proof of principle for ES-induced acceleration of axon regeneration in human patients. Carpel tunnel release surgery (CTRS) was performed and in the stimulation group of patients, stainless steel electrode wires placed alongside the median nerve proximal to the surgical decompression site for immediate 1 h 20 Hz bipolar ES. Subjects were followed for a year at regular intervals. Axonal regeneration was quantified using motor unit number estimation (MUNE) and sensory and motor nerve conduction studies. Purdue Pegboard Test, Semmes Weinstein Monofilaments, and Levine's Self-Assessment Questionnaire were used to assess functional recovery. The stimulation group had significant axonal regeneration 6-8 months after the CTRS when the MUNE increased to 290+/-140 (mean+/-SD) motor units (MU) from 150+/-62 MU at baseline (p<0.05). In comparison, MUNE did not significantly improve in the control group (p>0.2). Terminal motor latency significantly accelerated in the stimulation group but not the control group (p>0.1). Sensory nerve conduction values significantly improved in the stimulation group earlier than the controls. Other outcome measures showed a significant improvement in both patient groups. We conclude that brief low frequency ES accelerates axonal regeneration and target reinnervation in humans. Copyright 2009 Elsevier Inc. All rights reserved.

Reinnervation of the lateral gastrocnemius and soleus muscles in the rat by their common nerve.

PubMed Central

Gillespie, M J; Gordon, T; Murphy, P R

1986-01-01

To determine whether there is any specificity of regenerating nerves for their original muscles, the common lateral gastrocnemius soleus nerve (l.g.s.) innervating the fast-twitch lateral gastrocnemius (l.g.) and slow-twitch soleus muscles was sectioned in the hind limb of twenty adult rats. The proximal nerve stump was sutured to the dorsal surface of the l.g. muscle and 4-14 months later, the contractile properties of the reinnervated l.g. and soleus muscles and their single motor units were studied by dissection and stimulation of the ventral root filaments. Contractile properties of normal contralateral muscles were examined for comparison and motor units were isolated in l.g. and soleus muscles for study in a group of untreated animals. Measurement of time and rate parameters of maximal twitch and tetanic contractions showed that the rate of development of force increased significantly in reinnervated soleus muscles and approached the speed of l.g. muscles but rate of relaxation did not change appreciably. In reinnervated l.g. muscles, contraction speed was similar to normal l.g. muscles but relaxation rate declined toward the rates of relaxation in control soleus muscles. After reinnervation by the common l.g.s. nerve, the proportion of slow motor units in l.g. increased from 10 to 31% and decreased in soleus from 80 to 31%. The relative proportions of fast and slow motor units in each muscle were the same as the proportions of fast and slow units in the normal l.g. and soleus muscles combined. It was concluded that fast and slow muscles do not show any preference for their former nerves and that the change in the force profile of the reinnervated muscles is indicative of the relative proportions of fast and slow motor units: fast units dominate the contraction phase and slow units the relaxation phase of twitch and tetanic contractions of the muscle. PMID:3723414

Motor vehicle driver injury severity study under various traffic control at highway-rail grade crossings in the United States.

PubMed

Hao, Wei; Daniel, Janice

2014-12-01

Based on the Federal Railway Administration (FRA) database, approximately 62% of the collisions at highway-rail crossings occurred at locations with active controls (gate and flashing lights), followed by passive controls (cross bucks and stop signs) with approximately 28% of accidents. The study applied an ordered probit model to explore the determinants of driver injury severity under various control measures at highway-rail grade crossing in the United States. The analysis found that schedule factor (peak hour), visibility, motor vehicle speed, train speed, driver's age, area type, traffic volume and highway pavement impact driver injury severity at both active and passive highway-rail crossings. For both active and passive control highway-rail grade crossings, speed control for both trains and vehicles will significantly reduce driver injury severity. However, the level of influence by vehicle speed and train speed at passive control is higher compared with active control. Paving highways at highway-rail grade crossings will also help to reduce driver injury severity at highway-rail crossing accidents. Published by Elsevier Ltd.

Non-stationarity and power spectral shifts in EMG activity reflect motor unit recruitment in rat diaphragm muscle.

PubMed

Seven, Yasin B; Mantilla, Carlos B; Zhan, Wen-Zhi; Sieck, Gary C

2013-01-15

We hypothesized that a shift in diaphragm muscle (DIAm) EMG power spectral density (PSD) to higher frequencies reflects recruitment of more fatigable fast-twitch motor units and motor unit recruitment is reflected by EMG non-stationarity. DIAm EMG was recorded in anesthetized rats during eupnea, hypoxia-hypercapnia (10% O(2)-5% CO(2)), airway occlusion, and sneezing (maximal DIAm force). Although power in all frequency bands increased progressively across motor behaviors, PSD centroid frequency increased only during sneezing (p<0.05). The non-stationary period at the onset of EMG activity ranged from ∼80 ms during airway occlusion to ∼150 ms during eupnea. Within the initial non-stationary period of EMG activity 80-95% of motor units were recruited during different motor behaviors. Motor units augmented their discharge frequencies progressively beyond the non-stationary period; yet, EMG signal became stationary. In conclusion, non-stationarity of DIAm EMG reflects the period of motor unit recruitment, while a shift in the PSD towards higher frequencies reflects recruitment of more fatigable fast-twitch motor units. Copyright © 2012 Elsevier B.V. All rights reserved.

Isometric contractions of motor units and immunohistochemistry of mouse soleus muscle.

PubMed Central

Lewis, D M; Parry, D J; Rowlerson, A

1982-01-01

1. Isometric contractions of motor units, isolated functionally by ventral root splitting in vivo, were recorded from mouse soleus muscle. 2. Motor unit tensions varied over a narrow symmetrical range and averaged 4.7% of whole muscle tension, corresponding to twenty-one motor units per muscle. 3. There was considerable variation between muscles in isometric twitch times-to-peak and even greater variation for the motor units. The distribution of motor unit times-to-peak was apparently unimodal and could be fitted by a single normal population. A slightly better fit was, however, obtained with two normal populations, as suggested by the histochemistry. 4. Twitch time-to-peak decreased in proportion to axonal conduction velocity in individual animals. The whole population of motor units could be fitted by a linear relation between time-to-peak and the reciprocal of conduction time in the motor axon. Motor unit tension was also linearly related to the reciprocal of conduction time. 5. Histochemistry showed clear division between Type I and Type IIa fibres. Type I fibres reacted strongly with antibody against slow myosin of cat soleus muscle; Type IIa gave a reaction no stronger than the background. The division was as clear as in the cat or rat. Images Fig. 2 Plate 1 PMID:7050345

The effects of earmuff on physiologic and motor responses in premature infants admitted in neonatal intensive care unit.

PubMed

Abdeyazdan, Zahra; Ghassemi, Sara; Marofi, Maryam

2014-03-01

Continuous high-intensity noise in the Neonatal Intensive Care Unit (NICU) is stressful for premature infants and its reduction is considered as a nursing care. This study aimed to evaluate the effects of earmuffs' use on the physiologic and motor responses of premature infants. This is a clinical trial conducted on 64 premature infants admitted to the NICU, who met the inclusion criteria, and were randomly assigned to study and control groups. Earmuffs were used for premature infants for 2 h in the morning and 2 h in the afternoon for two consecutive days to reduce the noise intensity in the busiest time of the NICU. The group with earmuff (study group) was compared with the control group receiving only routine care. Infants' physiologic and motor responses were observed before, during, immediately, and 1 h after the intervention. Analysis of covariance and repeated measure analysis of variance (ANOVA) were used to analyze the data. When infants wore the earmuffs, they had significantly higher mean arterial oxygen saturation, the less frequent motor response, and a decrease in their pulse and respiratory rate. Paying attention to environmental noise can help the patients, especially the neonates in the NICU, and can be considered as a nursing care. Wearing earmuffs can protect premature infants against noise in the NICU and improve their physiological and motor state.

75 FR 26794 - New United Motor Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-12

... Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation and Toyota Motor Corporation... United Motor Manufacturing, Inc., formerly a joint venture of General Motors Corporation and Toyota Motor... reviewed the certification for workers of the subject firm. The workers assemble the Toyota Corolla and the...

Electrical engineering unit for the reactive power control of the load bus at the voltage instability

NASA Astrophysics Data System (ADS)

Kotenev, A. V.; Kotenev, V. I.; Kochetkov, V. V.; Elkin, D. A.

2018-01-01

For the purpose of reactive power control error reduction and decrease of the voltage sags in the electric power system caused by the asynchronous motors started the mathematical model of the load bus was developed. The model was built up of the sub-models of the following elements: a transformer, a transmission line, a synchronous and an asynchronous loads and a capacitor bank load, and represents the automatic reactive power control system taking into account electromagnetic processes of the asynchronous motors started and reactive power changing of the electric power system elements caused by the voltage fluctuation. The active power/time and reactive power/time characteristics based on the recommended procedure of the equivalent electric circuit parameters calculation were obtained. The derived automatic reactive power control system was shown to eliminate the voltage sags in the electric power system caused by the asynchronous motors started.

Vibration condition measure instrument of motor using MEMS accelerometer

NASA Astrophysics Data System (ADS)

Chen, Jun

2018-04-01

In this work, a novel vibration condition measure instrument of motor using a digital micro accelerometer is proposed. In order to reduce the random noise found in the data, the sensor modeling is established and also the Kalman filter (KMF) is developed. According to these data from KMF, the maximum vibration displacement is calculated by the integration algorithm with the DC bias removed. The high performance micro controller unit (MCU) is used in the implementation of controller. By the IIC digital interface port, the data are transmitted from sensor to controller. The hardware circuits of the sensor and micro controller are designed and tested. With the computational formula of maximum displacement and FFT, the high precession results of displacement and frequency are gotten. Finally, the paper presents various experimental results to prove that this instrument is suitable for application in electrical motor vibration measurement.

Estimating contraction level using root mean square amplitude in control subjects and patients with neuromuscular disorders.

PubMed

Boe, Shaun G; Rice, Charles L; Doherty, Timothy J

2008-04-01

To assess the utility of the surface electromyographic signal as a means of estimating the level of muscle force during quantitative electromyography studies by examining the relationship between muscle force and the amplitude of the surface electromyographic activity signal; and to determine the impact of a reduction in the number of motor units on this relationship, through inclusion of a sample of patients with neuromuscular disease. Cross-sectional, cohort study design. Tertiary care, ambulatory, electromyography laboratory. A volunteer, convenience sample of healthy control subjects (n=10), patients with amyotrophic lateral sclerosis (n=9), and patients with Charcot-Marie-Tooth disease type X (n=5). Not applicable. The first dorsal interosseous (FDI) and biceps brachii muscles were examined. Force values (at 10% increments) were calculated from two 4-second maximal voluntary contractions (MVCs). Surface electromyographic activity was recorded during separate 4-second voluntary contractions at 9 force increments (10% -90% of MVC). Additionally, a motor unit number estimate was derived for each subject to quantify the degree of motor unit loss in patients relative to control subjects. The relationships between force and surface electromyographic activity for both muscles (controls and patients) were best fit by a linear function. The variability about the grouped regression lines was quantified by 95% confidence intervals and found to be +/-6.7% (controls) and +/-8.5% (patients) for the FDI and +/-5% (controls) and +/-6.1% (patients) for the biceps brachii. These results suggest that the amplitude of the surface electromyographic activity signal may be used as a means of estimating the level of muscle force during quantitative electromyography studies. Future studies should be directed at examining if the variability associated with these force and surface electromyographic activity relationships is acceptable in replacing previous methods of measuring muscle force.

Motor Synergies and the Equilibrium-Point Hypothesis

PubMed Central

Latash, Mark L.

2010-01-01

The article offers a way to unite three recent developments in the field of motor control and coordination: (1) The notion of synergies is introduced based on the principle of motor abundance; (2) The uncontrolled manifold hypothesis is described as offering a computational framework to identify and quantify synergies; and (3) The equilibrium-point hypothesis is described for a single muscle, single joint, and multi-joint systems. Merging these concepts into a single coherent scheme requires focusing on control variables rather than performance variables. The principle of minimal final action is formulated as the guiding principle within the referent configuration hypothesis. Motor actions are associated with setting two types of variables by a controller, those that ultimately define average performance patterns and those that define associated synergies. Predictions of the suggested scheme are reviewed, such as the phenomenon of anticipatory synergy adjustments, quick actions without changes in synergies, atypical synergies, and changes in synergies with practice. A few models are briefly reviewed. PMID:20702893

Motor synergies and the equilibrium-point hypothesis.

PubMed

Latash, Mark L

2010-07-01

The article offers a way to unite three recent developments in the field of motor control and coordination: (1) The notion of synergies is introduced based on the principle of motor abundance; (2) The uncontrolled manifold hypothesis is described as offering a computational framework to identify and quantify synergies; and (3) The equilibrium-point hypothesis is described for a single muscle, single joint, and multijoint systems. Merging these concepts into a single coherent scheme requires focusing on control variables rather than performance variables. The principle of minimal final action is formulated as the guiding principle within the referent configuration hypothesis. Motor actions are associated with setting two types of variables by a controller, those that ultimately define average performance patterns and those that define associated synergies. Predictions of the suggested scheme are reviewed, such as the phenomenon of anticipatory synergy adjustments, quick actions without changes in synergies, atypical synergies, and changes in synergies with practice. A few models are briefly reviewed.

Effect of age and gender on the number of motor units in healthy subjects estimated by the multipoint incremental MUNE method.

PubMed

Gawel, Malgorzata; Kostera-Pruszczyk, Anna

2014-06-01

Motor unit number estimation (MUNE) is a tool for estimating the number of motor units. The aim was to evaluate the multipoint incremental MUNE method in a healthy population, to analyze whether aging, gender, and the dominant hand side influence the motor unit number, and to assess reproducibility of MUNE with the Shefner modification. We studied 60 volunteers (mean age, 47 ± 17.7 years) in four groups aged 18 to 30, 31 to 45, 46 to 60, and above 60 years. Motor unit number estimation was calculated in the abductor pollicis brevis (APB) and the abductor digiti minimi (ADM) by dividing the single motor unit action potential amplitude into the maximal compound motor action potential amplitude. Test-retest variability was 7%. The mean value of MUNE for APB was 133.2 ± 43 and for ADM was 157.1 ± 39.4. Significant differences in MUNE results were found between groups aged 18 to 30 and 60 years or older and between groups aged 31 to 45 and 60 years or older. Motor unit number estimation results correlated negatively with the age of subjects for both APB and ADM. Single motor unit action potential, reflecting the size of motor unit, increased with the age of subjects only in APB. Compound motor action potential amplitude correlated negatively with the age of subjects in APB and ADM. Significant correlations were seen between MUNE in APB or ADM and compound motor action potential amplitude in these muscles and the age of female subjects. A similar relationship was not found in males. Multipoint incremental MUNE method with the Shefner modification is a noninvasive, easy to perform method with high reproducibility. The loss of motor neurons because of aging could be confirmed by our MUNE study and seems to be more pronounced in females.

Muscle vibration sustains motor unit firing rate during submaximal isometric fatigue in humans

PubMed Central

Griffin, L; Garland, S J; Ivanova, T; Gossen, E R

2001-01-01

In keeping with the ‘muscular wisdom hypothesis’, many studies have documented that the firing rate of the majority of motor units decreased during fatiguing isometric contractions. The present study investigated whether the application of periodic muscle vibration, which strongly activates muscle spindles, would alter the modulation of motor unit firing rate during submaximal fatiguing isometric contractions. Thirty-three motor units from the lateral head of the triceps brachii muscle were recorded from 10 subjects during a sustained isometric 20 % maximal voluntary contraction (MVC) of the elbow extensors. Vibration was interposed on the contraction for 2 s every 10 s. Twenty-two motor units were recorded from the beginning of the fatigue task. The discharge rate of the majority of motor units remained constant (12/22) or increased (4/22) with fatigue. Six motor units demonstrated a reduction in discharge rate that later returned toward initial values; these motor units had higher initial discharge rates than the other 16 motor units. In a second series of experiments, four subjects held a sustained isometric 20 % MVC for 2 min and then vibration was applied as above for the remainder of the contraction. In this case, motor units initially demonstrated a decrease in firing rate that increased after the vibration was applied. Thus muscle spindle disfacilitation of the motoneurone pool may be associated with the decline of motor unit discharge rate observed during the first 2 min of the contraction. In a third set of experiments, seven subjects performed the main experiment on one occasion and repeated the fatigue task without vibration on a second occasion. Neither the endurance time of the fatiguing contraction nor the MVC torque following fatigue was affected by the application of vibration. This finding calls into question the applicability of the muscular wisdom hypothesis to submaximal contractions. PMID:11559785

Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion

PubMed Central

Lee, Sabrina S. M.; de Boef Miara, Maria; Arnold, Allison S.; Biewener, Andrew A.; Wakeling, James M.

2013-01-01

SUMMARY Animals modulate the power output needed for different locomotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate motor units must be recruited. Faster motor units have faster activation–deactivation rates than slower motor units, and they contract at higher strain rates; therefore, recruitment of faster motor units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified motor unit recruitment patterns in the gastrocnemii muscles of goats and examined whether faster motor units are recruited when locomotor speed is increased. The study also examined whether locomotor tasks that elicit faster (or slower) motor units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster motor units were recruited as goats increased their locomotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that recruitment of the different motor unit types depended, in part, on characteristics of the task. For the locomotor tasks and muscles analyzed here, recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks. PMID:22972893

Muscle vibration sustains motor unit firing rate during submaximal isometric fatigue in humans.

PubMed

Griffin, L; Garland, S J; Ivanova, T; Gossen, E R

2001-09-15

1. In keeping with the 'muscular wisdom hypothesis', many studies have documented that the firing rate of the majority of motor units decreased during fatiguing isometric contractions. The present study investigated whether the application of periodic muscle vibration, which strongly activates muscle spindles, would alter the modulation of motor unit firing rate during submaximal fatiguing isometric contractions. 2. Thirty-three motor units from the lateral head of the triceps brachii muscle were recorded from 10 subjects during a sustained isometric 20 % maximal voluntary contraction (MVC) of the elbow extensors. Vibration was interposed on the contraction for 2 s every 10 s. Twenty-two motor units were recorded from the beginning of the fatigue task. The discharge rate of the majority of motor units remained constant (12/22) or increased (4/22) with fatigue. Six motor units demonstrated a reduction in discharge rate that later returned toward initial values; these motor units had higher initial discharge rates than the other 16 motor units. 3. In a second series of experiments, four subjects held a sustained isometric 20 % MVC for 2 min and then vibration was applied as above for the remainder of the contraction. In this case, motor units initially demonstrated a decrease in firing rate that increased after the vibration was applied. Thus muscle spindle disfacilitation of the motoneurone pool may be associated with the decline of motor unit discharge rate observed during the first 2 min of the contraction. 4. In a third set of experiments, seven subjects performed the main experiment on one occasion and repeated the fatigue task without vibration on a second occasion. Neither the endurance time of the fatiguing contraction nor the MVC torque following fatigue was affected by the application of vibration. This finding calls into question the applicability of the muscular wisdom hypothesis to submaximal contractions.

Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion.

PubMed

Lee, Sabrina S M; de Boef Miara, Maria; Arnold, Allison S; Biewener, Andrew A; Wakeling, James M

2013-01-15

Animals modulate the power output needed for different locomotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate motor units must be recruited. Faster motor units have faster activation-deactivation rates than slower motor units, and they contract at higher strain rates; therefore, recruitment of faster motor units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified motor unit recruitment patterns in the gastrocnemii muscles of goats and examined whether faster motor units are recruited when locomotor speed is increased. The study also examined whether locomotor tasks that elicit faster (or slower) motor units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster motor units were recruited as goats increased their locomotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that recruitment of the different motor unit types depended, in part, on characteristics of the task. For the locomotor tasks and muscles analyzed here, recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks.

49 CFR 218.93 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... button or radio control when such switch is protected by distant switch indicators, switch point... units are connected so that they may be operated from a single control stand. Locomotive means, for... one or more propelling motors designed for moving other equipment; (2) With one or more propelling...

40 CFR 85.1512 - Admission of catalyst and O2 sensor-equipped vehicles.

Code of Federal Regulations, 2012 CFR

2012-07-01

... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF AIR POLLUTION FROM MOBILE SOURCES Importation of Motor..., where applicable, § 85.1510(c); and (iv) Has been driven outside the United States, Canada and Mexico or... purpose of this section, “driven outside the United States, Canada and Mexico” does not include mileage...

40 CFR 85.1512 - Admission of catalyst and O2 sensor-equipped vehicles.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF AIR POLLUTION FROM MOBILE SOURCES Importation of Motor..., where applicable, § 85.1510(c); and (iv) Has been driven outside the United States, Canada and Mexico or... purpose of this section, “driven outside the United States, Canada and Mexico” does not include mileage...

40 CFR 85.1512 - Admission of catalyst and O2 sensor-equipped vehicles.

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF AIR POLLUTION FROM MOBILE SOURCES Importation of Motor..., where applicable, § 85.1510(c); and (iv) Has been driven outside the United States, Canada and Mexico or... purpose of this section, “driven outside the United States, Canada and Mexico” does not include mileage...

40 CFR 85.1512 - Admission of catalyst and O2 sensor-equipped vehicles.

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF AIR POLLUTION FROM MOBILE SOURCES Importation of Motor..., where applicable, § 85.1510(c); and (iv) Has been driven outside the United States, Canada and Mexico or... purpose of this section, “driven outside the United States, Canada and Mexico” does not include mileage...

The Neural Mechanism Exploration of Adaptive Motor Control: Dynamical Economic Cell Allocation in the Primary Motor Cortex.

PubMed

Li, Wei; Guo, Yangyang; Fan, Jing; Ma, Chaolin; Ma, Xuan; Chen, Xi; He, Jiping

2017-05-01

Adaptive flexibility is of significance for the smooth and efficient movements in goal attainment. However, the underlying work mechanism of the cerebral cortex in adaptive motor control still remains unclear. How does the cerebral cortex organize and coordinate the activity of a large population of cells in the implementation of various motor strategies? To explore this issue, single-unit activities from the M1 region and kinematic data were recorded simultaneously in monkeys performing 3D reach-to-grasp tasks with different perturbations. Varying motor control strategies were employed and achieved in different perturbed tasks, via the dynamic allocation of cells to modulate specific movement parameters. An economic principle was proposed for the first time to describe a basic rule for cell allocation in the primary motor cortex. This principle, defined as the Dynamic Economic Cell Allocation Mechanism (DECAM), guarantees benefit maximization in cell allocation under limited neuronal resources, and avoids committing resources to uneconomic investments for unreliable factors with no or little revenue. That is to say, the cells recruited are always preferentially allocated to those factors with reliable return; otherwise, the cells are dispatched to respond to other factors about task. The findings of this study might partially reveal the working mechanisms underlying the role of the cerebral cortex in adaptive motor control, wherein is also of significance for the design of future intelligent brain-machine interfaces and rehabilitation device.

Motor unit recruitment and bursts of activity in the surface electromyogram during a sustained contraction.

PubMed

Riley, Zachary A; Terry, Mary E; Mendez-Villanueva, Alberto; Litsey, Jane C; Enoka, Roger M

2008-06-01

Bursts of activity in the surface electromyogram (EMG) during a sustained contraction have been interpreted as corresponding to the transient recruitment of motor units, but this association has never been confirmed. The current study compared the timing of trains of action potentials discharged by single motor units during a sustained contraction with the bursts of activity detected in the surface EMG signal. The 20 motor units from 6 subjects [recruitment threshold, 35.3 +/- 11.3% maximal voluntary contraction (MVC) force] that were detected with fine wire electrodes discharged 2-9 trains of action potentials (7.2 +/- 5.6 s in duration) when recruited during a contraction that was sustained at a force below its recruitment threshold (target force, 25.4 +/- 10.6% MVC force). High-pass filtering the bipolar surface EMG signal improved its correlation with the single motor unit signal. An algorithm applied to the surface EMG was able to detect 75% of the trains of motor unit action potentials. The results indicate that bursts of activity in the surface EMG during a constant-force contraction correspond to the transient recruitment of higher-threshold motor units in healthy individuals, and these results could assist in the diagnosis and design of treatment in individuals who demonstrate deficits in motor unit activation.

Shifts in the relationship between motor unit recruitment thresholds versus derecruitment thresholds during fatigue.

PubMed

Stock, Matt S; Mota, Jacob A

2017-12-01

Muscle fatigue is associated with diminished twitch force amplitude. We examined changes in the motor unit recruitment versus derecruitment threshold relationship during fatigue. Nine men (mean age = 26 years) performed repeated isometric contractions at 50% maximal voluntary contraction (MVC) knee extensor force until exhaustion. Surface electromyographic signals were detected from the vastus lateralis, and were decomposed into their constituent motor unit action potential trains. Motor unit recruitment and derecruitment thresholds and firing rates at recruitment and derecruitment were evaluated at the beginning, middle, and end of the protocol. On average, 15 motor units were studied per contraction. For the initial contraction, three subjects showed greater recruitment thresholds than derecruitment thresholds for all motor units. Five subjects showed greater recruitment thresholds than derecruitment thresholds for only low-threshold motor units at the beginning, with a mean cross-over of 31.6% MVC. As the muscle fatigued, many motor units were derecruited at progressively higher forces. In turn, decreased slopes and increased y-intercepts were observed. These shifts were complemented by increased firing rates at derecruitment relative to recruitment. As the vastus lateralis fatigued, the central nervous system's compensatory adjustments resulted in a shift of the regression line of the recruitment versus derecruitment threshold relationship. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Sources of signal-dependent noise during isometric force production.

PubMed

Jones, Kelvin E; Hamilton, Antonia F; Wolpert, Daniel M

2002-09-01

It has been proposed that the invariant kinematics observed during goal-directed movements result from reducing the consequences of signal-dependent noise (SDN) on motor output. The purpose of this study was to investigate the presence of SDN during isometric force production and determine how central and peripheral components contribute to this feature of motor control. Peripheral and central components were distinguished experimentally by comparing voluntary contractions to those elicited by electrical stimulation of the extensor pollicis longus muscle. To determine other factors of motor-unit physiology that may contribute to SDN, a model was constructed and its output compared with the empirical data. SDN was evident in voluntary isometric contractions as a linear scaling of force variability (SD) with respect to the mean force level. However, during electrically stimulated contractions to the same force levels, the variability remained constant over the same range of mean forces. When the subjects were asked to combine voluntary with stimulation-induced contractions, the linear scaling relationship between the SD and mean force returned. The modeling results highlight that much of the basic physiological organization of the motor-unit pool, such as range of twitch amplitudes and range of recruitment thresholds, biases force output to exhibit linearly scaled SDN. This is in contrast to the square root scaling of variability with mean force present in any individual motor-unit of the pool. Orderly recruitment by twitch amplitude was a necessary condition for producing linearly scaled SDN. Surprisingly, the scaling of SDN was independent of the variability of motoneuron firing and therefore by inference, independent of presynaptic noise in the motor command. We conclude that the linear scaling of SDN during voluntary isometric contractions is a natural by-product of the organization of the motor-unit pool that does not depend on signal-dependent noise in the motor command. Synaptic noise in the motor command and common drive, which give rise to the variability and synchronization of motoneuron spiking, determine the magnitude of the force variability at a given level of mean force output.

Loss of motor unit size and quadriceps strength over 10 years in post-polio syndrome.

PubMed

Bickerstaffe, A; van Dijk, J P; Beelen, A; Zwarts, M J; Nollet, F

2014-06-01

To investigate whether strength decline in post-polio syndrome (PPS) results from excessive distal axonal degeneration of enlarged motor units. We assessed changes over 10 years in isometric quadriceps strength, mean motor unit action potential (MUAP) size, root mean squared (RMS) amplitude, and level of interference (LOI) in 47 patients with PPS and 12 healthy controls, using high density surface EMG. At baseline, all patients had symptomatic quadriceps dysfunction, evidenced by transmission defects on single-fibre EMG. MU size and strength declined significantly by 20% and 15%, respectively in patients with PPS. Those with the largest initial MU sizes exhibited the greatest losses of mean MU size (27%) and proportional decreases in quadriceps strength (23%). Initial strength, change in LOI and change in RMS amplitude together explained 35% of the variability in strength changes in patients. MU size of controls did not change, although they lost 29% strength. MU size and strength declined concomitantly in a homogeneous cohort of patients with PPS and quadriceps dysfunction. This long term follow-up study provides evidence that size diminution of enlarged MUs combined with a reduced number of active MUs contributes to the gradual strength decline in PPS. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Once more on the equilibrium-point hypothesis (lambda model) for motor control.

PubMed

Feldman, A G

1986-03-01

The equilibrium control hypothesis (lambda model) is considered with special reference to the following concepts: (a) the length-force invariant characteristic (IC) of the muscle together with central and reflex systems subserving its activity; (b) the tonic stretch reflex threshold (lambda) as an independent measure of central commands descending to alpha and gamma motoneurons; (c) the equilibrium point, defined in terms of lambda, IC and static load characteristics, which is associated with the notion that posture and movement are controlled by a single mechanism; and (d) the muscle activation area (a reformulation of the "size principle")--the area of kinematic and command variables in which a rank-ordered recruitment of motor units takes place. The model is used for the interpretation of various motor phenomena, particularly electromyographic patterns. The stretch reflex in the lambda model has no mechanism to follow-up a certain muscle length prescribed by central commands. Rather, its task is to bring the system to an equilibrium, load-dependent position. Another currently popular version defines the equilibrium point concept in terms of alpha motoneuron activity alone (the alpha model). Although the model imitates (as does the lambda model) spring-like properties of motor performance, it nevertheless is inconsistent with a substantial data base on intact motor control. An analysis of alpha models, including their treatment of motor performance in deafferented animals, reveals that they suffer from grave shortcomings. It is concluded that parameterization of the stretch reflex is a basis for intact motor control. Muscle deafferentation impairs this graceful mechanism though it does not remove the possibility of movement.

Development and use of the incremental twitch subtraction MUNE method in mice.

PubMed

Hegedus, Janka; Jones, Kelvin E; Gordon, Tessa

2009-01-01

We have used a technique to estimate the number of functioning motor units (MUNE) innervating a muscle in mice based on twitch tension. The MUNE technique was verified by modeling twitch tensions from isolated ventral root stimulation. Analysis by twitch tensions allowed us to identify motor unit fiber types. The MUNE technique was used to compare normal mice with transgenic superoxide dismutase-1 mutation (G94A) mice to assess the time course of motor unit loss with respect to fiber type. Motor unit loss was found to occur well in advance of behavioral changes and the degree of reinnervation is dependent upon motor unit fiber types.

Encoding of speed and direction of movement in the human supplementary motor area

PubMed Central

Tankus, Ariel; Yeshurun, Yehezkel; Flash, Tamar; Fried, Itzhak

2010-01-01

Object The supplementary motor area (SMA) plays an important role in planning, initiation, and execution of motor acts. Patients with SMA lesions are impaired in various kinematic parameters, such as velocity and duration of movement. However, the relationships between neuronal activity and these parameters in the human brain have not been fully characterized. This is a study of single-neuron activity during a continuous volitional motor task, with the goal of clarifying these relationships for SMA neurons and other frontal lobe regions in humans. Methods The participants were 7 patients undergoing evaluation for epilepsy surgery requiring implantation of intracranial depth electrodes. Single-unit recordings were conducted while the patients played a computer game involving movement of a cursor in a simple maze. Results In the SMA proper, most of the recorded units exhibited a monotonic relationship between the unit firing rate and hand motion speed. The vast majority of SMA proper units with this property showed an inverse relation, that is, firing rate decrease with speed increase. In addition, most of the SMA proper units were selective to the direction of hand motion. These relationships were far less frequent in the pre-SMA, anterior cingulate gyrus, and orbitofrontal cortex. Conclusions The findings suggest that the SMA proper takes part in the control of kinematic parameters of end-effector motion, and thus lend support to the idea of connecting neuroprosthetic devices to the human SMA. PMID:19231930

Comparison of segmental spinal movement control in adolescents with and without idiopathic scoliosis using modified pressure biofeedback unit.

PubMed

Luo, Hong-Ji; Lin, Shi-Xiang; Wu, Shyi-Kuen; Tsai, Mei-Wun; Lee, Shwn-Jen

2017-01-01

Postural rehabilitation emphasizing on motor control training of segmental spinal movements has been proposed to effectively reduce the scoliotic spinal deformities in adolescent idiopathic scoliosis (AIS). However, information regarding the impairments of segmental spinal movement control involving segmental spinal stabilizers in adolescent idiopathic scoliosis remains limited. Examination of segmental spinal movement control may provide a window for investigating the features of impaired movement control specific to spinal segments that may assist in the development of physiotherapeutic management of AIS. To compare segmental spinal movement control in adolescents with and without idiopathic scoliosis using modified pressure biofeedback unit. Segmental spinal movement control was assessed in twenty adolescents with idiopathic scoliosis (AISG) and twenty healthy adolescents (CG) using a modified pressure biofeedback unit. Participants performed segmental spinal movements that primarily involved segmental spinal stabilizing muscles with graded and sustained muscle contraction against/off a pressure cuff from baseline to target pressures and then maintained for 1 min. Pressure data during the 1-minute maintenance phase were collected for further analysis. Pressure deviation were calculated and compared between groups. The AISG had significantly greater pressure deviations for all segmental spinal movements of cervical, thoracic, and lumbar spine than the CG. Pressure biofeedback unit was feasible for assessing segmental spinal movement control in AIS. AISG exhibited poorer ability to grade and sustain muscle activities for local movements of cervical, thoracic, and lumbar spine, suggesting motor control training of segmental spinal movements involving segmental spinal stabilizing muscles on frontal, sagittal, and transverse planes were required.

Crosswalk markings and the risk of pedestrian-motor vehicle collisions in older pedestrians.

PubMed

Koepsell, Thomas; McCloskey, Lon; Wolf, Marsha; Moudon, Anne Vernez; Buchner, David; Kraus, Jess; Patterson, Matthew

2002-11-06

Motor vehicles struck and killed 4739 pedestrians in the United States in the year 2000. Older pedestrians are at especially high risk. To determine whether crosswalk markings at urban intersections influence the risk of injury to older pedestrians. Case-control study in which the units of study were crossing locations. Six cities in Washington and California, with case accrual from February 1995 through January 1999. A total of 282 case sites were street-crossing locations at an intersection where a pedestrian aged 65 years or older had been struck by a motor vehicle while crossing the street; 564 control sites were other nearby crossings that were matched to case sites based on street classification. Trained observers recorded environmental characteristics, vehicular traffic flow and speed, and pedestrian use at each site on the same day of the week and time of day as when the case event had occurred. Risk of pedestrian-motor vehicle collision involving an older pedestrian. After adjusting for pedestrian flow, vehicle flow, crossing length, and signalization, risk of a pedestrian-motor vehicle collision was 2.1-fold greater (95% confidence interval, 1.1-4.0) at sites with a marked crosswalk. Almost all of the excess risk was due to 3.6-fold (95% confidence interval, 1.7-7.9) higher risk associated with marked crosswalks at sites with no traffic signal or stop sign. Crosswalk markings appear associated with increased risk of pedestrian-motor vehicle collision to older pedestrians at sites where no signal or stop sign is present to halt traffic.

Motor unit recruitment strategies are altered during deep-tissue pain.

PubMed

Tucker, Kylie; Butler, Jane; Graven-Nielsen, Thomas; Riek, Stephan; Hodges, Paul

2009-09-02

Muscle pain is associated with decreased motor unit discharge rate during constant force contractions. As discharge rate is a determinant of force, other adaptations in strategy must explain force maintenance during pain. Our aim was to determine whether motor unit recruitment strategies are altered during pain to maintain force despite reduced discharge rate. Motor unit discharge behavior was recorded in two muscles, one with (quadriceps) and one without [flexor pollicis longus (FPL)] synergists. Motor units were recruited during matched low-force contractions with and without experimentally induced pain, and at higher force without pain. A total of 52 and 34 units were recorded in quadriceps and FPL, respectively, during low-force contractions with and without pain. Of these, 20 quadriceps and 9 FPL units were identified during both trials. The discharge rate of these units reduced during pain in both muscles [quadriceps: 8.7 (1.5) to 7.5 (1.3) Hz, p < 0.001; FPL: 11.9 (1.5) to 10.0 (1.7) Hz, p < 0.001]. All remaining units discharged only with or without pain, but not in both conditions. Only one-third of the additional units recruited during pain (quadriceps n = 7/19, FPL n = 3/15) were those expected given orderly recruitment of the motor unit pool as determined during higher-force contractions. We conclude that reduced motor unit discharge rate with pain is accompanied by changes in the population of units used to maintain force. The recruitment of new units is partly inconsistent with generalized inhibition of the motoneuron pool predicted by the "pain adaptation" theory, and provides the basis for a new mechanism of motor adaptation with pain.

Relationships between motor unit size and recruitment threshold in older adults: implications for size principle.

PubMed

Fling, Brett W; Knight, Christopher A; Kamen, Gary

2009-08-01

As a part of the aging process, motor unit reorganization occurs in which small motoneurons reinnervate predominantly fast-twitch muscle fibers that have lost their innervation. We examined the relationship between motor unit size and the threshold force for recruitment in two muscles to determine whether older individuals might develop an alternative pattern of motor unit activation. Young and older adults performed isometric contractions ranging from 0 to 50% of maximal voluntary contraction in both the first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. Muscle fiber action potentials were recorded with an intramuscular needle electrode and motor unit size was computed using spike-triggered averaging of the global EMG signal (macro EMG), which was also obtained from the intramuscular needle electrode. As expected, older individuals exhibited larger motor units than young subjects in both the FDI and the TA. However, moderately strong correlations were obtained for the macro EMG amplitude versus recruitment threshold relationship in both the young and older adults within both muscles, suggesting that the size principle of motor unit recruitment seems to be preserved in older adults.

The effect of a physical activity intervention on preschoolers' fundamental motor skills - A cluster RCT.

PubMed

Wasenius, Niko S; Grattan, Kimberly P; Harvey, Alysha L J; Naylor, Patti-Jean; Goldfield, Gary S; Adamo, Kristi B

2018-07-01

To assess the effect of a physical activity intervention delivered in the childcare centres (CC), with or without a parent-driven home physical activity component, on children's fundamental motor skills (FMS). Six-month 3-arm cluster randomized controlled trial. Preschoolers were recruited from 18 licensed CC. CC were randomly assigned to a typical curriculum comparison group (COM), childcare intervention alone (CC), or childcare intervention with parental component (CC+HOME). FMS was measured with the Test of Gross Motor Development-2. Linear mixed models were performed at the level of the individual while accounting for clustering. Raw locomotor skills score increased significantly in the CC group (mean difference=2.5 units, 95% Confidence Intervals, CI, 1.0-4.1, p<0.001) and the CC+HOME group (mean difference=2.4 units, 95% CI, 0.8-4.0, p<0.001) compared to the COM group. No significant (p>0.05) between group differences were observed in the raw object control skills, sum of raw scores, or gross motor quotient. No significant sex differences were found in any of the measured outcomes. A physical activity intervention delivered in childcare with or without parents' involvement was effective in increasing locomotor skills in preschoolers. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Behavior of motor units in human biceps brachii during a submaximal fatiguing contraction.

PubMed

Garland, S J; Enoka, R M; Serrano, L P; Robinson, G A

1994-06-01

The activity of 50 single motor units was recorded in the biceps brachii muscle of human subjects while they performed submaximal isometric elbow flexion contractions that were sustained to induce fatigue. The purposes of this study were to examine the influence of fatigue on motor unit threshold force and to determine the relationship between the threshold force of recruitment and the initial interimpulse interval on the discharge rates of single motor units during a fatiguing contraction. The discharge rate of most motor units that were active from the beginning of the contraction declined during the fatiguing contraction, whereas the discharge rates of most newly recruited units were either constant or increased slightly. The absolute threshold forces of recruitment and derecruitment decreased, and the variability of interimpulse intervals increased after the fatigue task. The change in motor unit discharge rate during the fatigue task was related to the initial rate, but the direction of the change in discharge rate could not be predicted from the threshold force of recruitment or the variability in the interimpulse intervals. The discharge rate of most motor units declined despite an increase in the excitatory drive to the motoneuron pool during the fatigue task.

Motor units in vastus lateralis and in different vastus medialis regions show different firing properties during low-level, isometric knee extension contraction.

PubMed

de Souza, Leonardo Mendes Leal; Cabral, Hélio Veiga; de Oliveira, Liliam Fernandes; Vieira, Taian Martins

2018-04-01

Architectural differences along vastus medialis (VM) and between VM and vastus lateralis (VL) are considered functionally important for the patellar tracking, knee joint stability and knee joint extension. Whether these functional differences are associated with a differential activity of motor units between VM and VL is however unknown. In the present study, we, therefore, investigate neuroanatomical differences in the activity of motor units detected proximo-distally from VM and from the VL muscle. Nine healthy volunteers performed low-level isometric knee extension contractions (20% of their maximum voluntary contraction) following a trapezoidal trajectory. Surface electromyograms (EMGs) were recorded from VM proximal and distal regions and from VL using three linear adhesive arrays of eight electrodes. The firing rate and recruitment threshold of motor units decomposed from EMGs were then compared among muscle regions. Results show that VL motor units reached lower mean firing rates in comparison with VM motor units, regardless of their position within VM (P < .040). No significant differences in firing rate were found between proximal and distal, VM motor units (P = .997). Furthermore, no significant differences in the recruitment threshold were observed for all motor units analysed (P = .108). Our findings possibly suggest the greater potential of VL to generate force, due to its fibres arrangement, may account for the lower discharge rate observed for VL then either proximally or distally detected motor units in VM. Additionally, the present study opens new perspectives on the importance of considering muscle architecture in investigations of the neural aspects of motor behaviour. Copyright © 2017 Elsevier B.V. All rights reserved.

29. SOUTH SWING SPAN, SHOWING REPRESENTATIVE REDUCTION GEAR/MOTOR DRIVE UNIT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

29. SOUTH SWING SPAN, SHOWING REPRESENTATIVE REDUCTION GEAR/MOTOR DRIVE UNIT (CENTER) AND WEDGE MOTOR UNIT (RIGHT). - George P. Coleman Memorial Bridge, Spanning York River at U.S. Route 17, Yorktown, York County, VA

Motor Unit Interpulse Intervals During High Force Contractions.

PubMed

Stock, Matt S; Thompson, Brennan J

2016-01-01

We examined the means, medians, and variability for motor-unit interpulse intervals (IPIs) during voluntary, high force contractions. Eight men (mean age = 22 years) attempted to perform isometric contractions at 90% of their maximal voluntary contraction force while bipolar surface electromyographic (EMG) signals were detected from the vastus lateralis and vastus medialis muscles. Surface EMG signal decomposition was used to determine the recruitment thresholds and IPIs of motor units that demonstrated accuracy levels ≥ 96.0%. Motor units with high recruitment thresholds demonstrated longer mean IPIs, but the coefficients of variation were similar across all recruitment thresholds. Polynomial regression analyses indicated that for both muscles, the relationship between the means and standard deviations of the IPIs was linear. The majority of IPI histograms were positively skewed. Although low-threshold motor units were associated with shorter IPIs, the variability among motor units with differing recruitment thresholds was comparable.

Assessing fundamental motor skills in Belgian children aged 3-8 years highlights differences to US reference sample.

PubMed

Bardid, Farid; Huyben, Floris; Lenoir, Matthieu; Seghers, Jan; De Martelaer, Kristine; Goodway, Jacqueline D; Deconinck, Frederik J A

2016-06-01

This study aimed to understand the fundamental motor skills (FMS) of Belgian children using the process-oriented Test of Gross Motor Development, Second Edition (TGMD-2) and to investigate the suitability of using the United States (USA) test norms in Belgium. FMS were assessed using the TGMD-2. Gender, age and motor performance were examined in 1614 Belgian children aged 3-8 years (52.1% boys) and compared with the US reference sample. More proficient FMS performance was found with increasing age, from 3 to 6 years for locomotor skills and 3 to 7 years for object control skills. Gender differences were observed in object control skills, with boys performing better than girls. In general, Belgian children had lower levels of motor competence than the US reference sample, specifically for object control skills. The score distribution of the Belgian sample was skewed, with 37.4% scoring below average and only 6.9% scoring above average. This study supported the usefulness of the TGMD-2 as a process-oriented instrument to measure gross motor development in early childhood in Belgium. However, it also demonstrated that caution is warranted when using the US reference norms. ©2016 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

The aging neuromuscular system and motor performance

PubMed Central

Keenan, Kevin G.

2016-01-01

Age-related changes in the basic functional unit of the neuromuscular system, the motor unit, and its neural inputs have a profound effect on motor function, especially among the expanding number of old (older than ∼60 yr) and very old (older than ∼80 yr) adults. This review presents evidence that age-related changes in motor unit morphology and properties lead to impaired motor performance that includes 1) reduced maximal strength and power, slower contractile velocity, and increased fatigability; and 2) increased variability during and between motor tasks, including decreased force steadiness and increased variability of contraction velocity and torque over repeat contractions. The age-related increase in variability of motor performance with aging appears to involve reduced and more variable synaptic inputs that drive motor neuron activation, fewer and larger motor units, less stable neuromuscular junctions, lower and more variable motor unit action potential discharge rates, and smaller and slower skeletal muscle fibers that coexpress different myosin heavy chain isoforms in the muscle of older adults. Physical activity may modify motor unit properties and function in old men and women, although the effects on variability of motor performance are largely unknown. Many studies are of cross-sectional design, so there is a tremendous opportunity to perform high-impact and longitudinal studies along the continuum of aging that determine 1) the influence and cause of the increased variability with aging on functional performance tasks, and 2) whether lifestyle factors such as physical exercise can minimize this age-related variability in motor performance in the rapidly expanding numbers of very old adults. PMID:27516536

Motor impulsivity differentiates between psychiatric inpatients with multiple versus single lifetime suicide attempts.

PubMed

Colborn, Victoria A; LaCroix, Jessica M; Neely, Laura L; Tucker, Jennifer; Perera, Kanchana; Daruwala, Samantha E; Grammer, Geoffrey; Weaver, Jennifer; Ghahramanlou-Holloway, Marjan

2017-07-01

A history of multiple suicide attempts conveys greater risk for suicide than a single attempt. Impulsivity may partially explain the association between multiple attempts and increased risk. We examined trait impulsivity, ability to engage in goal-directed behaviors, and impulse control among psychiatrically hospitalized United States military personnel and their dependents. Individuals with a history of multiple versus single attempts had significantly higher motor impulsivity, indicating spur of the moment action. Providers are encouraged to directly assess and treat motor impulsivity among suicidal individuals. Further research should explore whether motor impulsivity is a mechanism of change in psychosocial suicide prevention interventions. Copyright © 2017. Published by Elsevier B.V.

Second-chance signal transduction explains cooperative flagellar switching.

PubMed

Zot, Henry G; Hasbun, Javier E; Minh, Nguyen Van

2012-01-01

The reversal of flagellar motion (switching) results from the interaction between a switch complex of the flagellar rotor and a torque-generating stationary unit, or stator (motor unit). To explain the steeply cooperative ligand-induced switching, present models propose allosteric interactions between subunits of the rotor, but do not address the possibility of a reaction that stimulates a bidirectional motor unit to reverse direction of torque. During flagellar motion, the binding of a ligand-bound switch complex at the dwell site could excite a motor unit. The probability that another switch complex of the rotor, moving according to steady-state rotation, will reach the same dwell site before that motor unit returns to ground state will be determined by the independent decay rate of the excited-state motor unit. Here, we derive an analytical expression for the energy coupling between a switch complex and a motor unit of the stator complex of a flagellum, and demonstrate that this model accounts for the cooperative switching response without the need for allosteric interactions. The analytical result can be reproduced by simulation when (1) the motion of the rotor delivers a subsequent ligand-bound switch to the excited motor unit, thereby providing the excited motor unit with a second chance to remain excited, and (2) the outputs from multiple independent motor units are constrained to a single all-or-none event. In this proposed model, a motor unit and switch complex represent the components of a mathematically defined signal transduction mechanism in which energy coupling is driven by steady-state and is regulated by stochastic ligand binding. Mathematical derivation of the model shows the analytical function to be a general form of the Hill equation (Hill AV (1910) The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves. J Physiol 40: iv-vii).

Motor unit recruitment patterns 2: the influence of myoelectric intensity and muscle fascicle strain rate.

PubMed

Hodson-Tole, Emma F; Wakeling, James M

2008-06-01

To effectively meet the force requirements of a given movement an appropriate number and combination of motor units must be recruited between and within muscles. Orderly recruitment of motor units has been shown to occur in a wide range of skeletal muscles, however, alternative strategies do occur. Faster motor units are better suited to developing force rapidly, and produce higher mechanical power with greater efficiency at faster shortening strain rates than slower motor units. As the frequency content of the myoelectric signal is related to the fibre type of the active motor units, we hypothesised that, in addition to an association between myoelectric frequency and intensity, there would be a significant association between muscle fascicle shortening strain rate and myoelectric frequency content. Myoelectric and sonomicrometric data were collected from the three ankle extensor muscles of the rat hind limb during walking and running. Myoelectric signals were analysed using wavelet transformation and principal component analysis to give a measure of the signal frequency content. Sonomicrometric signals were analysed to give measures of muscle fascicle strain and strain rate. The relationship between myoelectric frequency and both intensity and muscle fascicle strain rate was found to change across the time course of a stride, with differences also occurring in the strength of the associations between and within muscles. In addition to the orderly recruitment of motor units, a mechanical strategy of motor unit recruitment was therefore identified. Motor unit recruitment is therefore a multifactorial phenomenon, which is more complex than typically thought.

Recruitment of motor units in two fascicles of the semispinalis cervicis muscle.

PubMed

Schomacher, Jochen; Dideriksen, Jakob Lund; Farina, Dario; Falla, Deborah

2012-06-01

This study investigated the behavior of motor units in the semispinalis cervicis muscle. Intramuscular EMG recordings were obtained unilaterally at levels C2 and C5 in 15 healthy volunteers (8 men, 7 women) who performed isometric neck extensions at 5%, 10%, and 20% of the maximal force [maximum voluntary contraction (MVC)] for 2 min each and linearly increasing force contractions from 0 to 30% MVC over 3 s. Individual motor unit action potentials were identified. The discharge rate and interspike interval variability of the motor units in the two locations did not differ. However, the recruitment threshold of motor units detected at C2 (n = 16, mean ± SD: 10.3 ± 6.0% MVC) was greater than that of motor units detected at C5 (n = 92, 6.9 ± 4.3% MVC) (P < 0.01). A significant level of short-term synchronization was identified in 246 of 307 motor unit pairs when computed within one spinal level but only in 28 of 110 pairs of motor units between the two levels. The common input strength, which quantifies motor unit synchronization, was greater for pairs within one level (0.47 ± 0.32) compared with pairs between levels (0.09 ± 0.07) (P < 0.05). In a second experiment on eight healthy subjects, interference EMG was recorded from the same locations during a linearly increasing force contraction from 0 to 40% MVC and showed significantly greater EMG amplitude at C5 than at C2. In conclusion, synaptic input is distributed partly independently and nonuniformly to different fascicles of the semispinalis cervicis muscle.

Inhibition linearizes firing rate responses in human motor units: implications for the role of persistent inward currents.

PubMed

Revill, Ann L; Fuglevand, Andrew J

2017-01-01

Motor neurons are the output neurons of the central nervous system and are responsible for controlling muscle contraction. When initially activated during voluntary contraction, firing rates of motor neurons increase steeply but then level out at modest rates. Activation of an intrinsic source of excitatory current at recruitment onset may underlie the initial steep increase in firing rate in motor neurons. We attempted to disable this intrinsic excitatory current by artificially activating an inhibitory reflex. When motor neuron activity was recorded while the inhibitory reflex was engaged, firing rates no longer increased steeply, suggesting that the intrinsic excitatory current was probably responsible for the initial sharp rise in motor neuron firing rate. During graded isometric contractions, motor unit (MU) firing rates increase steeply upon recruitment but then level off at modest rates even though muscle force continues to increase. The mechanisms underlying such firing behaviour are not known although activation of persistent inward currents (PICs) might be involved. PICs are intrinsic, voltage-dependent currents that activate strongly when motor neurons (MNs) are first recruited. Such activation might cause a sharp escalation in depolarizing current and underlie the steep initial rise in MU firing rate. Because PICs can be disabled with synaptic inhibition, we hypothesized that artificial activation of an inhibitory pathway might curb this initial steep rise in firing rate. To test this, human subjects performed slow triangular ramp contractions of the ankle dorsiflexors in the absence and presence of tonic synaptic inhibition delivered to tibialis anterior (TA) MNs by sural nerve stimulation. Firing rate profiles (expressed as a function of contraction force) of TA MUs recorded during these tasks were compared for control and stimulation conditions. Under control conditions, during the ascending phase of the triangular contractions, 93% of the firing rate profiles were best fitted by rising exponential functions. With stimulation, however, firing rate profiles were best fitted with linear functions or with less steeply rising exponentials. Firing rate profiles for the descending phases of the contractions were best fitted with linear functions for both control and stimulation conditions. These results seem consistent with the idea that PICs contribute to non-linear firing rate profiles during ascending but not descending phases of contractions. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

System and method for motor speed estimation of an electric motor

DOEpatents

Lu, Bin [Kenosha, WI; Yan, Ting [Brookfield, WI; Luebke, Charles John [Sussex, WI; Sharma, Santosh Kumar [Viman Nagar, IN

2012-06-19

A system and method for a motor management system includes a computer readable storage medium and a processing unit. The processing unit configured to determine a voltage value of a voltage input to an alternating current (AC) motor, determine a frequency value of at least one of a voltage input and a current input to the AC motor, determine a load value from the AC motor, and access a set of motor nameplate data, where the set of motor nameplate data includes a rated power, a rated speed, a rated frequency, and a rated voltage of the AC motor. The processing unit is also configured to estimate a motor speed based on the voltage value, the frequency value, the load value, and the set of nameplate data and also store the motor speed on the computer readable storage medium.

Ia Afferent input alters the recruitment thresholds and firing rates of single human motor units.

PubMed

Grande, G; Cafarelli, E

2003-06-01

Vibration of the patellar tendon recruits motor units in the knee extensors via excitation of muscle spindles and subsequent Ia afferent input to the alpha-motoneuron pool. Our first purpose was to determine if the recruitment threshold and firing rate of the same motor unit differed when recruited involuntarily via reflex or voluntarily via descending spinal pathways. Although Ia input is excitatory to the alpha-motoneuron pool, it has also been shown paradoxically to inhibit itself. Our second purpose was to determine if vibration of the patellar tendon during a voluntary knee extension causes a change in the firing rate of already recruited motor units. In the first protocol, 10 subjects voluntarily reproduced the same isometric force profile of the knee extensors that was elicited by vibration of the patellar tendon. Single motor unit recordings from the vastus lateralis (VL) were obtained with tungsten microelectrodes and unitary behaviour was examined during both reflex and voluntary knee extensions. Recordings from 135 single motor units showed that both recruitment thresholds and firing rates were lower during reflex contractions. In the second protocol, 7 subjects maintained a voluntary knee extension at 30 N for approximately 40-45 s. Three bursts of patellar tendon vibration were superimposed at regular intervals throughout the contraction and changes in the firing rate of already recruited motor units were examined. A total of 35 motor units were recorded and each burst of superimposed vibration caused a momentary reduction in the firing rates and recruitment of additional units. Our data provide evidence that Ia input modulates the recruitment thresholds and firing rates of motor units providing more flexibility within the neuromuscular system to grade force at low levels of force production.

Motor control theories and their applications.

PubMed

Latash, Mark L; Levin, Mindy F; Scholz, John P; Schöner, Gregor

2010-01-01

We describe several influential hypotheses in the field of motor control including the equilibrium-point (referent configuration) hypothesis, the uncontrolled manifold hypothesis, and the idea of synergies based on the principle of motor abundance. The equilibrium-point hypothesis is based on the idea of control with thresholds for activation of neuronal pools; it provides a framework for analysis of both voluntary and involuntary movements. In particular, control of a single muscle can be adequately described with changes in the threshold of motor unit recruitment during slow muscle stretch (threshold of the tonic stretch reflex). Unlike the ideas of internal models, the equilibrium-point hypothesis does not assume neural computations of mechanical variables. The uncontrolled manifold hypothesis is based on the dynamic system approach to movements; it offers a toolbox to analyze synergic changes within redundant sets of elements related to stabilization of potentially important performance variables. The referent configuration hypothesis and the principle of abundance can be naturally combined into a single coherent scheme of control of multi-element systems. A body of experimental data on healthy persons and patients with movement disorders are reviewed in support of the mentioned hypotheses. In particular, movement disorders associated with spasticity are considered as consequences of an impaired ability to shift threshold of the tonic stretch reflex within the whole normal range. Technical details and applications of the mentioned hypo-theses to studies of motor learning are described. We view the mentioned hypotheses as the most promising ones in the field of motor control, based on a solid physical and neurophysiological foundation.

Discharge patterns of human genioglossus motor units during arousal from sleep.

PubMed

Wilkinson, Vanessa; Malhotra, Atul; Nicholas, Christian L; Worsnop, Christopher; Jordan, Amy S; Butler, Jane E; Saboisky, Julian P; Gandevia, Simon C; White, David P; Trinder, John

2010-03-01

Single motor unit recordings of the human genioglossus muscle reveal motor units with a variety of discharge patterns. Integrated multiunit electromyographic recordings of genioglossus have demonstrated an abrupt increase in the muscle's activity at arousal from sleep. The aim of the present study was to determine the effect of arousal from sleep on the activity of individual motor units as a function of their particular discharge pattern. Genioglossus activity was measured using intramuscular fine-wire electrodes inserted via a percutaneous approach. Arousals from sleep were identified using the ASDA criterion and the genioglossus electromyogram recordings analyzed for single motor unit activity. Sleep research laboratory. Sleep and respiratory data were collected in 8 healthy subjects (6 men). 138 motor units were identified during prearousalarousal sleep: 25% inspiratory phasic, 33% inspiratory tonic, 4% expiratory phasic, 3% expiratory tonic, and 35% tonic. At arousal from sleep inspiratory phasic units significantly increased the proportion of a breath over which they were active, but did not appreciably increase their rate of firing. 80 new units were identified at arousals, 75% were inspiratory, many of which were active for only 1 or 2 breaths. 22% of units active before arousal, particularly expiratory and tonic units, stopped at the arousal. Increased genioglossus muscle activity at arousal from sleep is primarily due to recruitment of inspiratory phasic motor units. Further, activity within the genioglossus motoneuron pool is reorganized at arousal as, in addition to recruitment, approximately 20% of units active before arousals stopped firing.

Characterizing the complexity of spontaneous motor unit patterns of amyotrophic lateral sclerosis using approximate entropy

NASA Astrophysics Data System (ADS)

Zhou, Ping; Barkhaus, Paul E.; Zhang, Xu; Zev Rymer, William

2011-10-01

This paper presents a novel application of the approximate entropy (ApEn) measurement for characterizing spontaneous motor unit activity of amyotrophic lateral sclerosis (ALS) patients. High-density surface electromyography (EMG) was used to record spontaneous motor unit activity bilaterally from the thenar muscles of nine ALS subjects. Three distinct patterns of spontaneous motor unit activity (sporadic spikes, tonic spikes and high-frequency repetitive spikes) were observed. For each pattern, complexity was characterized by calculating the ApEn values of the representative signal segments. A sliding window over each segment was also introduced to quantify the dynamic changes in complexity for the different spontaneous motor unit patterns. We found that the ApEn values for the sporadic spikes were the highest, while those of the high-frequency repetitive spikes were the lowest. There is a significant difference in mean ApEn values between two arbitrary groups of the three spontaneous motor unit patterns (P < 0.001). The dynamic ApEn curve from the sliding window analysis is capable of tracking variations in EMG activity, thus providing a vivid, distinctive description for different patterns of spontaneous motor unit action potentials in terms of their complexity. These findings expand the existing knowledge of spontaneous motor unit activity in ALS beyond what was previously obtained using conventional linear methods such as firing rate or inter-spike interval statistics.

Motor vehicle fatalities in the United States construction industry.

PubMed

Ore, T; Fosbroke, D E

1997-09-01

A death certificate-based surveillance system was used to identify 2144 work-related motor vehicle fatalities among civilian workers in the United States construction industry over the years 1980-92. Construction workers were twice as likely to be killed by a motor vehicle as the average worker, with an annual crude mortality rate of 2.3/100,000 workers. Injury prevention efforts in construction have had limited effect on motor vehicle-related deaths, with death rates falling by only 11% during the 13-year period, compared with 43% for falls, 54% for electrocutions and 48% for machinery. In all industries combined, motor vehicle fatality rates dropped by 47%. The largest proportion of motor vehicle deaths (40%) occurred among pedestrians, with construction accounting for more than one-fourth of all pedestrian deaths. A minimum of 54 (6%) of these pedestrian fatalities were flaggers or surveyors. Flaggers accounted for half the 34 pedestrian fatalities among women, compared with only 3% among men. Along with previous studies and recent trends in the amount and type of road construction, these results underscore the need for better traffic control management in construction work areas to reduce pedestrian fatalities. As the second leading cause of traumatic death in construction, with an annual average share of 15% of the total deaths, exceeded only by falls, prevention of work-related motor vehicle research should become a greater priority in the construction industry.

Effects of space flight on locomotor control

NASA Technical Reports Server (NTRS)

Bloomberg, Jacob J.; Layne, Charles S.; McDonald, P. Vernon; Peters, Brian T.; Huebner, William P.; Reschke, Millard F.; Berthoz, Alain; Glasauer, Stefan; Newman, Dava; Jackson, D. Keoki

1999-01-01

In the microgravity environment of spaceflight, the relationship between sensory input and motor output is altered. During prolonged missions, neural adaptive processes come into play to recalibrate central nervous system function, thereby permitting new motor control strategies to emerge in the novel sensory environment of microgravity. However, the adaptive state achieved during spaceflight is inappropriate for a unit gravity environment and leads to motor control alterations upon return to Earth that include disturbances in locomotion. Indeed, gait and postural instabilities following the return to Earth have been reported in both U.S. astronauts and Russian cosmonauts even after short duration (5- to 10-day) flights. After spaceflight, astronauts may: (1) experience the sensation of turning while attempting to walk a straight path, (2) encounter sudden loss of postural stability, especially when rounding corners, (3) perceive exaggerated pitch and rolling head movements during walking, (4) experience sudden loss of orientation in unstructured visual environments, or (5) experience significant oscillopsia during locomotion.

Assessment of power step performances of variable speed pump-turbine unit by means of hydro-electrical system simulation

NASA Astrophysics Data System (ADS)

Béguin, A.; Nicolet, C.; Hell, J.; Moreira, C.

2017-04-01

The paper explores the improvement in ancillary services that variable speed technologies can provide for the case of an existing pumped storage power plant of 2x210 MVA which conversion from fixed speed to variable speed is investigated with a focus on the power step performances of the units. First two motor-generator variable speed technologies are introduced, namely the Doubly Fed Induction Machine (DFIM) and the Full Scale Frequency Converter (FSFC). Then a detailed numerical simulation model of the investigated power plant used to simulate power steps response and comprising the waterways, the pump-turbine unit, the motor-generator, the grid connection and the control systems is presented. Hydroelectric system time domain simulations are performed in order to determine the shortest response time achievable, taking into account the constraints from the maximum penstock pressure and from the rotational speed limits. It is shown that the maximum instantaneous power step response up and down depends on the hydro-mechanical characteristics of the pump-turbine unit and of the motor-generator speed limits. As a results, for the investigated test case, the FSFC solution offer the best power step response performances.

Japan Report.

DTIC Science & Technology

1985-05-24

United States, MITI has restrained growth rates of three big makers— Toyota Motor Corp, Nissan Motor Co and Honda Motor Co—in the fiscal year that started...617,000 units and 544,000 units, respectively, the sources said. Toyota shipped 551,790 units and Nissan 487,040 units in fiscal 1984. Honda is...35,010 units and Isuzu 29,500 units by their own outlets. 60 Toyota and Nissan are each being allotted an identical raise of" 11.9 percent, to some

Remodeling of motor units after nerve regeneration studied by quantitative electromyography.

PubMed

Krarup, Christian; Boeckstyns, Michel; Ibsen, Allan; Moldovan, Mihai; Archibald, Simon

2016-02-01

Peripheral nerve has the capacity to regenerate after nerve lesions; during reinnervation of muscle motor units are gradually reestablished. The aim of this study was to follow the time course of reestablishing and remodeling of motor units in relation to recovery of force after different types of nerve repair. Reinnervation of muscle was compared clinically and electrophysiologically in complete median or ulnar nerve lesions with short gap lengths in the distal forearm repaired with a collagen nerve conduit (11 nerves) or nerve suture (10 nerves). Reestablishment of motor units was studied by quantitative EMG and recording of evoked compound muscle action potential (CMAP) during a 24-month observation period after nerve repair. Force recovered partially to about 80% of normal. Denervation activity gradually decreased during reinnervation though it was still increased at 24 months. Nascent motor unit potentials (MUPs) at early reinnervation were prolonged and polyphasic. During longitudinal studies, MUPs remained prolonged and their amplitudes gradually increased markedly. Firing of MUPs was unstable throughout the study. CMAPs gradually increased and the number of motor units recovered to approximately 20% of normal. There was weak evidence of CMAP amplitude recovery after suture ahead of conduit repair but without treatment related differences at 2 years. Surgical repair of nerve lesions with a nerve conduit or suture supported recovery of force and of motor unit reinnervation to the same extent. Changes occurred at a higher rate during early regeneration and slower after 12 months but should be followed for at least 2 years to assess outcome. EMG changes reflected extensive remodeling of motor units from early nascent units to a mature state with greatly enlarged units due to axonal regeneration and collateral sprouting and maturation of regenerated nerve and reinnervated muscle fibers after both types of repair. Remodeling of motor units after peripheral nerve lesions provides the basis for better recovery of force than the number of motor axons and units. There were no differences after repair with a collagen nerve conduit and nerve suture at short nerve gap lengths. The reduced number of motor units indicates that further improvement of repair procedures and nerve environment is needed. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Motor unit number estimates and neuromuscular transmission in the tibialis anterior of master athletes: evidence that athletic older people are not spared from age-related motor unit remodeling.

PubMed

Piasecki, Mathew; Ireland, Alex; Coulson, Jessica; Stashuk, Dan W; Hamilton-Wright, Andrew; Swiecicka, Agnieszka; Rutter, Martin K; McPhee, Jamie S; Jones, David A

2016-10-01

Muscle motor unit numbers decrease markedly in old age, while remaining motor units are enlarged and can have reduced neuromuscular junction transmission stability. However, it is possible that regular intense physical activity throughout life can attenuate this remodeling. The aim of this study was to compare the number, size, and neuromuscular junction transmission stability of tibialis anterior (TA) motor units in healthy young and older men with those of exceptionally active master runners. The distribution of motor unit potential (MUP) size was determined from intramuscular electromyographic signals recorded in healthy male Young (mean ± SD, 26 ± 5 years), Old (71 ± 4 years) and Master Athletes (69 ± 3 years). Relative differences between groups in numbers of motor units was assessed using two methods, one comparing MUP size and muscle cross-sectional area (CSA) determined with MRI, the other comparing surface recorded MUPs with maximal compound muscle action potentials and commonly known as a "motor unit number estimate (MUNE)". Near fiber (NF) jiggle was measured to assess neuromuscular junction transmission stability. TA CSA did not differ between groups. MUNE values for the Old and Master Athletes were 45% and 40%, respectively, of the Young. Intramuscular MUPs of Old and Master Athletes were 43% and 56% larger than Young. NF jiggle was slightly higher in the Master Athletes, with no difference between Young and Old. These results show substantial and similar motor unit loss and remodeling in Master Athletes and Old individuals compared with Young, which suggests that lifelong training does not attenuate the age-related loss of motor units. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

The effects of local forearm muscle cooling on motor unit properties.

PubMed

Mallette, Matthew M; Green, Lara A; Gabriel, David A; Cheung, Stephen S

2018-02-01

Muscle cooling impairs maximal force. Using needle electromyography (EMG) to assess motor unit properties during muscle cooling, is limited and equivocal. Therefore, we aimed to determine the impact of local muscle cooling on motor unit firing properties using surface EMG decomposition. Twenty participants (12 M, 8 F) completed maximal, evoked, and trapezoidal contractions during thermoneutral and cold muscle conditions. Forearm muscle temperature was manipulated using 10-min neutral (~ 32 °C) or 20-min cold (~ 3 °C) water baths. Twitches and maximal voluntary contractions were performed prior to, and after, forearm immersion in neutral or cold water. Motor unit properties were assessed during trapezoidal contractions to 50% baseline force using surface EMG decomposition. Impaired contractile properties from muscle cooling were evident in the twitch amplitude, duration, and rate of force development indicating that the muscle was successfully cooled from the cold water bath (all d ≥ 0.5, P < 0.05). Surface EMG decomposition showed muscle cooling increased the number of motor units (d = 0.7, P = 0.01) and motor unit action potential (MUAP) duration (d = 0.6, P < 0.001), but decreased MUAP amplitude (d = 0.2, P = 0.012). Individually, neither motor unit firing rates (d = 0.1, P = 0.843) nor recruitment threshold (d = 0.1, P = 0.746) changed; however, the relationship between the recruitment threshold and motor unit firing rate was steeper (d = 1.0, P < 0.001) and had an increased y-intercept (d = 0.9, P = 0.007) with muscle cooling. Since muscle contractility is impaired with muscle cooling, these findings suggest a compensatory increase in the number of active motor units, and small but coupled changes in motor unit firing rates and recruitment threshold to produce the same force.

Developmental profile of slow hand movement oscillation coupling in humans.

PubMed

Deutsch, Katherine M; Stephens, John A; Farmer, Simon F

2011-05-01

In adults, slow hand and finger movements are characterized by 6- to 12-Hz discontinuities visible in the raw records and spectra of motion signals such as acceleration. This pulsitile behavior is correlated with motor unit synchronization at 6-12 Hz as shown by significant coherence at these frequencies between pairs of motor units and between the motor units and the acceleration recorded from the limb part controlled by the muscle, suggesting that it has a central origin. In this study, we examined the correlation between this 6- to 12-Hz pulsatile behavior and muscle activity as a function of childhood development. Sixty-eight participants (ages 4-25 yr) performed static wrist extensions against gravity or slow wrist extension and flexion movements while extensor carpi radialis muscle electromyographic (EMG) and wrist acceleration signals were simultaneously recorded. Coherence between EMG and acceleration within the 6- to 12-Hz frequency band was used as an index of the strength of the relation between central drive and the motor output. The main findings of the study are 1) EMG-acceleration coherence increased with increases in age, with the age differences being greater under movement conditions and the difference between conditions increasing with age; 2) the EMG signal showed increases in normalized power with increases in age under both conditions; and 3) coherence under movement conditions was moderately positively correlated with manual dexterity. These findings indicate that the strength of the 6- to 12-Hz central oscillatory drive to the motor output increases through childhood development and may contribute to age-related improvements in motor skills.

Alternative Fuels Data Center: How Do All-Electric Cars Work?

Science.gov Websites

charge while charging the pack. Power electronics controller: This unit manages the flow of electrical of the engine, electric motor, power electronics, and other components. Traction battery pack: Stores

Motor unit recruitment in human genioglossus muscle in response to hypercapnia.

PubMed

Nicholas, Christian L; Bei, Bei; Worsnop, Christopher; Malhotra, Atul; Jordan, Amy S; Saboisky, Julian P; Chan, Julia K M; Duckworth, Ella; White, David P; Trinder, John

2010-11-01

single motor unit recordings of the genioglossus (GG) muscle indicate that GG motor units have a variety of discharge patterns, including units that have higher discharge rates during inspiration (inspiratory phasic and inspiratory tonic), or expiration (expiratory phasic and expiratory tonic), or do not modify their rate with respiration (tonic). Previous studies have shown that an increase in GG muscle activity is a consequence of increased activity in inspiratory units. However, there are differences between studies as to whether this increase is primarily due to recruitment of new motor units (motor unit recruitment) or to increased discharge rate of already active units (rate coding). Sleep-wake state studies in humans have suggested the former, while hypercapnia experiments in rats have suggested the latter. In this study, we investigated the effect of hypercapnia on GG motor unit activity in humans during wakefulness. sleep research laboratory. sixteen healthy men. each participant was administered at least 6 trials with P(et)CO(2) being elevated 8.4 (SD = 1.96) mm Hg over 2 min following a 30-s baseline. Subjects were instrumented for GG EMG and respiratory measurements with 4 fine wire electrodes inserted subcutaneously into the muscle. One hundred forty-one motor units were identified during the baseline: 47% were inspiratory modulated, 29% expiratory modulated, and 24% showed no respiratory related modulation. Sixty-two new units were recruited during hypercapnia. The distribution of recruited units was significantly different from the baseline distribution, with 84% being inspiratory modulated (P < 0.001). Neither units active during baseline, nor new units recruited during hypercapnia, increased their discharge rate as P(et)CO(2) increased (P > 0.05 for all comparisons). increased GG muscle activity in humans occurs because of recruitment of previously inactive inspiratory modulated units.

Human motor unit recordings: origins and insight into the integrated motor system.

PubMed

Duchateau, Jacques; Enoka, Roger M

2011-08-29

Soon after Edward Liddell [1895-1981] and Charles Sherrington [1857-1952] introduced the concept of a motor unit in 1925 and the necessary technology was developed, the recording of single motor unit activity became feasible in humans. It was quickly discovered by Edgar Adrian [1889-1977] and Detlev Bronk [1897-1975] that the force exerted by muscle during voluntary contractions was the result of the concurrent recruitment of motor units and modulation of the rate at which they discharged action potentials. Subsequent studies found that the relation between discharge frequency and motor unit force was characterized by a sigmoidal function. Based on observations on experimental animals, Elwood Henneman [1915-1996] proposed a "size principle" in 1957 and most studies in humans focussed on validating this concept during various types of muscle contractions. By the end of the 20th C, the experimental evidence indicated that the recruitment order of human motor units was determined primarily by motoneuron size and that the occasional changes in recruitment order were not an intended strategy of the central nervous system. Fundamental knowledge on the function of Sherrington's "common final pathway" was expanded with observations on motor unit rotation, minimal and maximal discharge rates, discharge variability, and self-sustained firing. Despite the great amount of work on characterizing motor unit activity during the first century of inquiry, however, many basic questions remain unanswered and these limit the extent to which findings on humans and experimental animals can be integrated and generalized to all movements. 2011 Elsevier B.V. All rights reserved.

Motor unit recruitment strategies and muscle properties determine the influence of synaptic noise on force steadiness

PubMed Central

Dideriksen, Jakob L.; Negro, Francesco; Enoka, Roger M.

2012-01-01

Motoneurons receive synaptic inputs from tens of thousands of connections that cause membrane potential to fluctuate continuously (synaptic noise), which introduces variability in discharge times of action potentials. We hypothesized that the influence of synaptic noise on force steadiness during voluntary contractions is limited to low muscle forces. The hypothesis was examined with an analytical description of transduction of motor unit spike trains into muscle force, a computational model of motor unit recruitment and rate coding, and experimental analysis of interspike interval variability during steady contractions with the abductor digiti minimi muscle. Simulations varied contraction force, level of synaptic noise, size of motor unit population, recruitment range, twitch contraction times, and level of motor unit short-term synchronization. Consistent with the analytical derivations, simulations and experimental data showed that force variability at target forces above a threshold was primarily due to low-frequency oscillations in neural drive, whereas the influence of synaptic noise was almost completely attenuated by two low-pass filters, one related to convolution of motoneuron spike trains with motor unit twitches (temporal summation) and the other attributable to summation of single motor unit forces (spatial summation). The threshold force above which synaptic noise ceased to influence force steadiness depended on recruitment range, size of motor unit population, and muscle contractile properties. This threshold was low (<10% of maximal force) for typical values of these parameters. Results indicate that motor unit recruitment and muscle properties of a typical muscle are tuned to limit the influence of synaptic noise on force steadiness to low forces and that the inability to produce a constant force during stronger contractions is mainly attributable to the common low-frequency oscillations in motoneuron discharge rates. PMID:22423000

Recruitment of motor units in two fascicles of the semispinalis cervicis muscle

PubMed Central

Schomacher, Jochen; Dideriksen, Jakob Lund; Farina, Dario

2012-01-01

This study investigated the behavior of motor units in the semispinalis cervicis muscle. Intramuscular EMG recordings were obtained unilaterally at levels C2 and C5 in 15 healthy volunteers (8 men, 7 women) who performed isometric neck extensions at 5%, 10%, and 20% of the maximal force [maximum voluntary contraction (MVC)] for 2 min each and linearly increasing force contractions from 0 to 30% MVC over 3 s. Individual motor unit action potentials were identified. The discharge rate and interspike interval variability of the motor units in the two locations did not differ. However, the recruitment threshold of motor units detected at C2 (n = 16, mean ± SD: 10.3 ± 6.0% MVC) was greater than that of motor units detected at C5 (n = 92, 6.9 ± 4.3% MVC) (P < 0.01). A significant level of short-term synchronization was identified in 246 of 307 motor unit pairs when computed within one spinal level but only in 28 of 110 pairs of motor units between the two levels. The common input strength, which quantifies motor unit synchronization, was greater for pairs within one level (0.47 ± 0.32) compared with pairs between levels (0.09 ± 0.07) (P < 0.05). In a second experiment on eight healthy subjects, interference EMG was recorded from the same locations during a linearly increasing force contraction from 0 to 40% MVC and showed significantly greater EMG amplitude at C5 than at C2. In conclusion, synaptic input is distributed partly independently and nonuniformly to different fascicles of the semispinalis cervicis muscle. PMID:22402657

High-Temperature Switched-Reluctance Electric Motor

NASA Technical Reports Server (NTRS)

Montague, Gerald; Brown, Gerald; Morrison, Carlos; Provenza, Andy; Kascak, Albert; Palazzolo, Alan

2003-01-01

An eight-pole radial magnetic bearing has been modified into a switched-reluctance electric motor capable of operating at a speed as high as 8,000 rpm at a temperature as high as 1,000 F (=540 C). The motor (see figure) is an experimental prototype of starter-motor/generator units that have been proposed to be incorporated into advanced gas turbine engines and that could operate without need for lubrication or active cooling. The unique features of this motor are its electromagnet coils and, to some extent, its control software. Heretofore, there has been no commercial-off-the-shelf wire capable of satisfying all of the requirements for fabrication of electromagnet coils capable of operation at temperatures up to 1,000 F (=540 C). The issues addressed in the development of these electromagnet coils included thermal expansion, oxidation, pliability to small bend radii, micro-fretting, dielectric breakdown, tensile strength, potting compound, thermal conduction, and packing factor. For a test, the motor was supported, along with a rotor of 18 lb (.8-kg) mass, 3-in. (.7.6-cm) diameter, 21-in. (.53-cm) length, on bearings packed with high-temperature grease. The motor was located at the mid span of the rotor and wrapped with heaters. The motor stator was instrumented with thermocouples. At the time of reporting the information for this article, the motor had undergone 14 thermal cycles between room temperature and 1,000 F (.540 C) and had accumulated operating time >27.5 hours at 1,000 F (=540 C). The motor-controller hardware includes a personal computer equipped with analog-to-digital input and digital-to-analog output cards. The controller software is a C-language code that implements a switched-reluctance motor-control principle: that is, it causes the coils to be energized in a sequence timed to generate a rotating magnetic flux that creates a torque on a scalloped rotor. The controller can operate in an open- or closed-loop mode. In addition, the software has been modified to enable the simultaneous operation of the prototype motor or another, similar apparatus as both a motor and a magnetic bearing. Combined bearing/motor operation has been demonstrated at room temperature but had not yet been demonstrated at high temperature at the time of reporting the information for this article.

Associations Between Hormonal Biomarkers and Cognitive, Motor, and Language Developmental Status in Very Low Birth Weight Infants.

PubMed

Cho, June; Holditch-Davis, Diane; Su, Xiaogang; Phillips, Vivien; Biasini, Fred; Carlo, Waldemar A

Male infants are more prone to health problems and developmental delays than female infants. On the basis of theories of gender differences in brain development and social relationships, we explored associations between testosterone and cortisol levels with infant cognitive, motor, and language development ("infant development") in very low birth weight (VLBW) infants, controlling for mother-infant interactions, characteristics of mothers and infants, and days of saliva collection after birth. A total of 62 mother-VLBW infant pairs were recruited from the newborn intensive care unit of a tertiary medical center in the Southeast United States. Data were collected through infant medical record review, biochemical measurement, observation of mother-infant interactions, and standard questionnaires. Infant development was assessed at 6 months corrected age (CA), and mother-infant interactions were observed at 3 and 6 months CA. General linear regression with separate analyses for each infant gender showed that high testosterone levels were positively associated with language development of male infants after controlling for mother-infant interactions and other covariates, whereas high cortisol levels were negatively associated with motor development of female infants after controlling for mother-infant interactions. Steroid hormonal levels may well be more fundamental factors for assessing infant development than infant gender or mother-infant interactions at 6 months CA.

Broca’s Area as a Pre-articulatory Phonetic Encoder: Gating the Motor Program

PubMed Central

Ferpozzi, Valentina; Fornia, Luca; Montagna, Marcella; Siodambro, Chiara; Castellano, Antonella; Borroni, Paola; Riva, Marco; Rossi, Marco; Pessina, Federico; Bello, Lorenzo; Cerri, Gabriella

2018-01-01

The exact nature of the role of Broca’s area in control of speech and whether it is exerted at the cognitive or at the motor level is still debated. Intraoperative evidence of a lack of motor responses to direct electrical stimulation (DES) of Broca’s area and the observation that its stimulation induces a “speech arrest” without an apparent effect on the ongoing activity of phono-articulatory muscles, raises the argument. Essentially, attribution of direct involvement of Broca’s area in motor control of speech, requires evidence of a functional connection of this area with the phono-articulatory muscles’ motoneurons. With a quantitative approach we investigated, in 20 patients undergoing surgery for brain tumors, whether DES delivered on Broca’s area affects the recruitment of the phono-articulatory muscles’ motor units. The electromyography (EMG) of the muscles active during two speech tasks (object picture naming and counting) was recorded during and in absence of DES on Broca’s area. Offline, the EMG of each muscle was analyzed in frequency (power spectrum, PS) and time domain (root mean square, RMS) and the two conditions compared. Results show that DES on Broca’s area induces an intensity-dependent “speech arrest.” The intensity of DES needed to induce “speech arrest” when applied on Broca’s area was higher when compared to the intensity effective on the neighboring pre-motor/motor cortices. Notably, PS and RMS measured on the EMG recorded during “speech arrest” were superimposable to those recorded at baseline. Partial interruptions of speech were not observed. Speech arrest was an “all-or-none” effect: muscle activation started only by removing DES, as if DES prevented speech onset. The same effect was observed when stimulating directly the subcortical fibers running below Broca’s area. Intraoperative data point to Broca’s area as a functional gate authorizing the phonetic translation to be executed by the motor areas. Given the absence of a direct effect on motor units recruitment, a direct control of Broca’s area on the phono-articulatory apparatus seems unlikely. Moreover, the strict correlation between DES-intensity and speech prevention, might attribute this effect to the inactivation of the subcortical fibers rather than to Broca’s cortical neurons. PMID:29520225

Changes in muscle fiber conduction velocity indicate recruitment of distinct motor unit populations.

PubMed

Houtman, C J; Stegeman, D F; Van Dijk, J P; Zwarts, M J

2003-09-01

To obtain more insight into the changes in mean muscle fiber conduction velocity (MFCV) during sustained isometric exercise at relatively low contraction levels, we performed an in-depth study of the human tibialis anterior muscle by using multichannel surface electromyogram. The results show an increase in MFCV after an initial decrease of MFCV at 30 or 40% maximum voluntary contraction in all of the five subjects studied. With a peak velocity analysis, we calculated the distribution of conduction velocities of action potentials in the bipolar electromyogram signal. It shows two populations of peak velocities occurring simultaneously halfway through the exercise. The MFCV pattern implies the recruitment of two different populations of motor units. Because of the lowering of MFCV of the first activated population of motor units, the newly recruited second population of motor units becomes visible. It is most likely that the MFCV pattern can be ascribed to the fatiguing of already recruited predominantly type I motor units, followed by the recruitment of fresh, predominantly type II, motor units.

Discharge patterns of human tensor palatini motor units during sleep onset.

PubMed

Nicholas, Christian L; Jordan, Amy S; Heckel, Leila; Worsnop, Christopher; Bei, Bei; Saboisky, Julian P; Eckert, Danny J; White, David P; Malhotra, Atul; Trinder, John

2012-05-01

Upper airway muscles such as genioglossus (GG) and tensor palatini (TP) reduce activity at sleep onset. In GG reduced muscle activity is primarily due to inspiratory modulated motor units becoming silent, suggesting reduced respiratory pattern generator (RPG) output. However, unlike GG, TP shows minimal respiratory modulation and presumably has few inspiratory modulated motor units and minimal input from the RPG. Thus, we investigated the mechanism by which TP reduces activity at sleep onset. The activity of TP motor units were studied during relaxed wakefulness and over the transition from wakefulness to sleep. Sleep laboratory. Nine young (21.4 ± 3.4 years) males were studied on a total of 11 nights. Sleep onset. Two TP EMGs (thin, hooked wire electrodes), and sleep and respiratory measures were recorded. One hundred twenty-one sleep onsets were identified (13.4 ± 7.2/subject), resulting in 128 motor units (14.3 ± 13.0/subject); 29% of units were tonic, 43% inspiratory modulated (inspiratory phasic 18%, inspiratory tonic 25%), and 28% expiratory modulated (expiratory phasic 21%, expiratory tonic 7%). There was a reduction in both expiratory and inspiratory modulated units, but not tonic units, at sleep onset. Reduced TP activity was almost entirely due to de-recruitment. TP showed a similar distribution of motor units as other airway muscles. However, a greater proportion of expiratory modulated motor units were active in TP and these expiratory units, along with inspiratory units, tended to become silent over sleep onset. The data suggest that both expiratory and inspiratory drive components from the RPG are reduced at sleep onset in TP.

Solar heating system final design package

NASA Technical Reports Server (NTRS)

1979-01-01

The system is composed of a warm air collector, a logic control unit and a universal switching and transport unit. The collector was originally conceived and designed as an integrated roof/wall system and therefore provides a dual function in the structure. The collector serves both as a solar energy conversion system and as a structural weather resistant skin. The control unit provides totally automatic control over the operation of the system. It receives input data from sensor probes in collectors, storage and living space. The logic was designed so as to make maximum use of solar energy and minimize use of conventional energy. The transport and switching unit is a high-efficiency air-handling system equipped with gear motor valves that respond to outputs from the control system. The fan unit was designed for maximum durability and efficiency in operation, and has permanently lubricated ball bearings and excellent air-handling efficiency.

Differential activation of motor units in the wrist extensor muscles during the tonic vibration reflex in man.

PubMed Central

Romaiguère, P; Vedel, J P; Azulay, J P; Pagni, S

1991-01-01

1. Single motor unit activity was recorded in the extensor carpi radialis longus and extensor carpi radialis brevis muscles of five healthy human subjects, using metal microelectrodes. 2. Motor units were characterized on the basis of their twitch contraction times and their force recruitment thresholds during voluntary imposed-ramp contractions. 3. The discharge patterns of forty-three motor units were studied during tonic vibration reflex elicited by prolonged (150 s) trains of vibration (30 Hz) applied to the distal tendons of the muscles. The temporal relationships between the individual small tendon taps of the vibratory stimulus and the motor unit impulses were analysed on dot raster displays and post-stimulus time histograms. 4. After tendon taps, the impulses of motor units with long twitch contraction times (mean +/- S.D., 47.2 +/- 10.7 ms) and low recruitment thresholds (0.88 +/- 0.6 N) formed a single narrow peak (P1) with a latency (22.7 +/- 1.4 ms) which was comparable to that of the tendon jerk in the extensor carpi radialis muscles. These motor units were named 'P1 units'. On the other hand, the response of motor units with shorter twitch contraction times (31.1 +/- 3.3 ms) and higher recruitment thresholds (3.21 +/- 1.3 N) showed two peaks: a short latency (23.4 +/- 1.3 ms) P1 peak similar to the previous one and a P2 peak occurring 9.4 +/- 1.2 ms later. These motor units were named 'P1-P2 units'. 5. When the reflex contraction increased slowly, the P1 peaks of 'P1-P2 units' were clearly predominant at the beginning of the contraction, during the rising phase of the motor unit discharge frequency, while the P2 peaks became predominant when the units had reached their maximal discharge frequency. 6. Increasing the tendon vibration frequency (35, 55, 75, 95 Hz) did not modify the 'P1 unit' discharge pattern. Due to interference between vibration period and peak latencies, increasing the vibration frequency caused the P1 and P2 peaks of 'P1-P2 units' to overlap. 7. Superficial cutaneous stimulation of the dorsal side of the forearm during tendon vibration noticeably decreased the P1 peaks in both types of motor units. In the P2 peaks it could result in either a decrease or an increase but the average effect was a slight increase. 8. When applied 10 s before tendon vibration, cutaneous stimulation considerably suppressed the tonic vibration reflex.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1822565

Motor control by precisely timed spike patterns

PubMed Central

Srivastava, Kyle H.; Holmes, Caroline M.; Vellema, Michiel; Pack, Andrea R.; Elemans, Coen P. H.; Nemenman, Ilya; Sober, Samuel J.

2017-01-01

A fundamental problem in neuroscience is understanding how sequences of action potentials (“spikes”) encode information about sensory signals and motor outputs. Although traditional theories assume that this information is conveyed by the total number of spikes fired within a specified time interval (spike rate), recent studies have shown that additional information is carried by the millisecond-scale timing patterns of action potentials (spike timing). However, it is unknown whether or how subtle differences in spike timing drive differences in perception or behavior, leaving it unclear whether the information in spike timing actually plays a role in brain function. By examining the activity of individual motor units (the muscle fibers innervated by a single motor neuron) and manipulating patterns of activation of these neurons, we provide both correlative and causal evidence that the nervous system uses millisecond-scale variations in the timing of spikes within multispike patterns to control a vertebrate behavior—namely, respiration in the Bengalese finch, a songbird. These findings suggest that a fundamental assumption of current theories of motor coding requires revision. PMID:28100491

Alternative Fuels Data Center: How Do Plug-In Hybrid Electric Cars Work?

Science.gov Websites

the pack. Power electronics controller: This unit manages the flow of electrical energy delivered by , electric motor, power electronics, and other components. Traction battery pack: Stores electricity for use

Discharge Patterns of Human Tensor Palatini Motor Units During Sleep Onset

PubMed Central

Nicholas, Christian L.; Jordan, Amy S.; Heckel, Leila; Worsnop, Christopher; Bei, Bei; Saboisky, Julian P.; Eckert, Danny J.; White, David P.; Malhotra, Atul; Trinder, John

2012-01-01

Study Objectives: Upper airway muscles such as genioglossus (GG) and tensor palatini (TP) reduce activity at sleep onset. In GG reduced muscle activity is primarily due to inspiratory modulated motor units becoming silent, suggesting reduced respiratory pattern generator (RPG) output. However, unlike GG, TP shows minimal respiratory modulation and presumably has few inspiratory modulated motor units and minimal input from the RPG. Thus, we investigated the mechanism by which TP reduces activity at sleep onset. Design: The activity of TP motor units were studied during relaxed wakefulness and over the transition from wakefulness to sleep. Setting: Sleep laboratory. Participants: Nine young (21.4 ± 3.4 years) males were studied on a total of 11 nights. Intervention: Sleep onset. Measurements and Results: Two TP EMGs (thin, hooked wire electrodes), and sleep and respiratory measures were recorded. One hundred twenty-one sleep onsets were identified (13.4 ± 7.2/subject), resulting in 128 motor units (14.3 ± 13.0/subject); 29% of units were tonic, 43% inspiratory modulated (inspiratory phasic 18%, inspiratory tonic 25%), and 28% expiratory modulated (expiratory phasic 21%, expiratory tonic 7%). There was a reduction in both expiratory and inspiratory modulated units, but not tonic units, at sleep onset. Reduced TP activity was almost entirely due to de-recruitment. Conclusions: TP showed a similar distribution of motor units as other airway muscles. However, a greater proportion of expiratory modulated motor units were active in TP and these expiratory units, along with inspiratory units, tended to become silent over sleep onset. The data suggest that both expiratory and inspiratory drive components from the RPG are reduced at sleep onset in TP. Citation: Nicholas CL; Jordan AS; Heckel L; Worsnop C; Bei B: Saboisky JP; Eckert DJ; White DP; Malhotra A; Trinder J. Discharge patterns of human tensor palatini motor units during sleep onset. SLEEP 2012;35(5):699-707. PMID:22547896

The Impact of Accountability on Student Performance in a Secondary Physical Education Badminton Unit

ERIC Educational Resources Information Center

Lund, Jacalyn; Shanklin, Jennifer

2011-01-01

The purpose of this study was to examine the effect of accountability on the quality of student motor responses during a 10-day badminton unit with female high school students enrolled in a required physical education class. Students in the control class participated in the same learning activities taught by the same teacher as the treatment…

Electric propulsion system for wheeled vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramos, J.A.

1981-11-03

An electric propulsion system for a wheeled vehicle has a generator and motor connected to a drive shaft and an electrical system for charging a battery during all conditions of power transfer from the wheels of the vehicle to the generator to minimize energy required for propulsion. A variable speed power coupling unit connecting the motor to the drive shaft has sprockets revolving about a belt connected sun sprocket with speed control effected by varying the rate of satellite sprocket rotation.

Software Package on Integrated Nonlinear Dynamic Modeling and Field Oriented Control (FOC) of Permanent Magnet (PM) Motor for High Performance Electromechanical Actuators (EMAs)

DTIC Science & Technology

2011-01-01

Louis Chow, David Woodburn, Lei Zhou, Jared Bindl, Yang Hu, and Wendell Brokaw University of Central Florida JANUARY 2011 Interim Report...Magnet (PM) Motor % % Written in SI or MKS Unit System. % % Authors: % David Woodburn % Dr. Lei Zhou % Dr. Thomas X. Wu clear all...Initial phase winding resistance [ ohm ] id = 0; % Phase d current [A] iq = 0; % Phase q current [A] did_dt = 0

A Qualitative Study of the European Trucking Industry and Logistics Strategies Using the United States Motor Carrier Industry as a Guide

DTIC Science & Technology

1992-09-01

UNITED STATES MOTOR CARRIER INDUSTRY AS A GUIDE THESIS David W. Butler Andrew P. Wilhelm Captain, USAF Captain, USAF AFIT/GLM/LSM/92S-7 Approved for...UNITED STATES MOTOR CARRIER INDUSTRY AS A GUIDE THESIS Presented to the Faculty of the School of Systems and Logistics of the Air Force Institute of...THE EUROPEAN TRUCKING INDUSTRY AND LOGISTICS STRATEGIES USING THE UNITED STATES MOTOR CARRIER INDUSTRY AS A GUIDE I. Introduction General Issue The

Testing of motor unit synchronization model for localized muscle fatigue.

PubMed

Naik, Ganesh R; Kumar, Dinesh K; Yadav, Vivek; Wheeler, Katherine; Arjunan, Sridhar

2009-01-01

Spectral compression of surface electromyogram (sEMG) is associated with onset of localized muscle fatigue. The spectral compression has been explained based on motor unit synchronization theory. According to this theory, motor units are pseudo randomly excited during muscle contraction, and with the onset of muscle fatigue the recruitment pattern changes such that motor unit firings become more synchronized. While this is widely accepted, there is little experimental proof of this phenomenon. This paper has used source dependence measures developed in research related to independent component analysis (ICA) to test this theory.

Quantification of the proportion of motor neurons recruited by transcranial electrical stimulation during intraoperative motor evoked potential monitoring.

PubMed

Tsutsui, Shunji; Yamada, Hiroshi; Hashizume, Hiroshi; Minamide, Akihito; Nakagawa, Yukihiro; Iwasaki, Hiroshi; Yoshida, Munehito

2013-12-01

Transcranial motor evoked potentials (TcMEPs) are widely used to monitor motor function during spinal surgery. However, they are much smaller and more variable in amplitude than responses evoked by maximal peripheral nerve stimulation, suggesting that a limited number of spinal motor neurons to the target muscle are excited by transcranial stimulation. The aim of this study was to quantify the proportion of motor neurons recruited during TcMEP monitoring under general anesthesia. In twenty patients who underwent thoracic and/or lumbar spinal surgery with TcMEP monitoring, the triple stimulation technique (TST) was applied to the unilateral upper arm intraoperatively. Total intravenous anesthesia was employed. Trains of four stimuli were delivered with maximal intensity and an inter-pulse interval of 1.5 ms. TST responses were recorded from the abductor digiti minimi muscle, and the negative peak amplitude and area were measured and compared between the TST test (two collisions between transcranial and proximal and distal peripheral stimulation) and control response (two collisions between two proximal and one distal peripheral stimulation). The highest degree of superimposition of the TST test and control responses was chosen from several trials per patient. The average ratios (test:control) were 17.1 % (range 1.8-38 %) for the amplitudes and 21.6 % (range 2.9-40 %) for the areas. The activity of approximately 80 % of the motor units to the target muscle cannot be detected by TcMEP monitoring. Therefore, changes in evoked potentials must be interpreted cautiously when assessing segmental motor function with TcMEP monitoring.

Synchronization of low- and high-threshold motor units.

PubMed

Defreitas, Jason M; Beck, Travis W; Ye, Xin; Stock, Matt S

2014-04-01

We examined the degree of synchronization for both low- and high-threshold motor unit (MU) pairs at high force levels. MU spike trains were recorded from the quadriceps during high-force isometric leg extensions. Short-term synchronization (between -6 and 6 ms) was calculated for every unique MU pair for each contraction. At high force levels, earlier recruited motor unit pairs (low-threshold) demonstrated relatively low levels of short-term synchronization (approximately 7.3% extra firings than would have been expected by chance). However, the magnitude of synchronization increased significantly and linearly with mean recruitment threshold (reaching 22.1% extra firings for motor unit pairs recruited above 70% MVC). Three potential mechanisms that could explain the observed differences in synchronization across motor unit types are proposed and discussed. Copyright © 2013 Wiley Periodicals, Inc.

Can fast-twitch muscle fibres be selectively recruited during lengthening contractions? Review and applications to sport movements.

PubMed

Chalmers, Gordon R

2008-01-01

Literature examining the recruitment order of motor units during lengthening (eccentric) contractions was reviewed to determine if fast-twitch motor units can be active while lower threshold slow-twitch motor units are not active. Studies utilizing surface electromyogram (EMG) amplitude, single motor unit activity, spike amplitude-frequency analyses, EMG power spectrum, mechanomyographic, and phosphocreatine-to-creatine ratio (PCr/Cr) techniques were reviewed. Only single motor unit and PCr/Cr data were found to be suitable to address the goals of this review. Nine of ten single motor unit studies, examining joint movement velocities up to 225 degrees/s and forces up to 53% of a maximum voluntary contraction, found that the size principle of motor unit recruitment applied during lengthening contractions. Deviation from the size principle was demonstrated by one study examining movements within a small range of low velocities and modest forces, although other studies examining similar low forces and lengthening velocities reported size-ordered recruitment. The PCr/Cr data demonstrated the activation of all fibre types in lengthening maximal contractions. Most evidence indicates that for lengthening contractions of a wide range of efforts and speeds, fast-twitch muscle fibres cannot be selectively recruited without activity of the slow-twitch fibres of the same muscle.

The relationship of motor unit size, firing rate and force.

PubMed

Conwit, R A; Stashuk, D; Tracy, B; McHugh, M; Brown, W F; Metter, E J

1999-07-01

Using a clinical electromyographic (EMG) protocol, motor units were sampled from the quadriceps femoris during isometric contractions at fixed force levels to examine how average motor unit size and firing rate relate to force generation. Mean firing rates (mFRs) and sizes (mean surface-detected motor unit action potential (mS-MUAP) area) of samples of active motor units were assessed at various force levels in 79 subjects. MS-MUAP size increased linearly with increased force generation, while mFR remained relatively constant up to 30% of a maximal force and increased appreciably only at higher force levels. A relationship was found between muscle force and mS-MUAP area (r2 = 0.67), mFR (r2 = 0.38), and the product of mS-MUAP area and mFR (mS-MUAP x mFR) (r2 = 0.70). The results support the hypothesis that motor units are recruited in an orderly manner during forceful contractions, and that in large muscles only at higher levels of contraction ( > 30% MVC) do mFRs increase appreciably. MS-MUAP and mFR can be assessed using clinical EMG techniques and they may provide a physiological basis for analyzing the role of motor units during muscle force generation.

Effect of ageing on the force development in tetanic contractions of motor units in rat medial gastrocnemius muscle.

PubMed

Łochyński, Dawid; Kaczmarek, Dominik; Krutki, Piotr; Celichowski, Jan

2010-09-01

The purpose of this study was to determine the effect of ageing on the rate of force generation of motor units, and the mechanical efficiency of contraction produced by a doublet discharge. The study was carried out on isolated motor units of rat medial gastrocnemius muscle of young (5-10 mo) and two groups of old (24-25 and 28-30 mo) Wistar rats. Motor units were classified into the fast fatigable (FF), fast resistant (FR) and slow (S) ones. The force output and rate of force development were determined for non-doublet unfused tetanic contractions evoked by a series of a constant-rate trains of pulses and corresponding doublet contractions starting with an initial brief interpulse interval of 5 ms, and for maximal tetanic contraction. In FF motor units the rate of force development and the force produced by the doublet discharge increased transiently at the age of 24-25 mo, while in S and FR motor units this increase was observed at the age of 28-30 mo. Age-related decrease in the rate of force development of skeletal muscle cannot be attributed to a decline in efficiency of force production by functioning motor units. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Time-related changes in firing rates are influenced by recruitment threshold and twitch force potentiation in the first dorsal interosseous.

PubMed

Miller, Jonathan D; Herda, Trent J; Trevino, Michael A; Sterczala, Adam J; Ciccone, Anthony B

2017-08-01

What is the central question of this study? The influences of motor unit recruitment threshold and twitch force potentiation on the changes in firing rates during steady-force muscular contractions are not well understood. What is the main finding and its importance? The behaviour of motor units during steady force was influenced by recruitment threshold, such that firing rates decreased for lower-threshold motor units but increased for higher-threshold motor units. In addition, individuals with greater changes in firing rates possessed greater twitch force potentiation. There are contradictory reports regarding changes in motor unit firing rates during steady-force contractions. Inconsistencies are likely to be the result of previous studies disregarding motor unit recruitment thresholds and not examining firing rates on a subject-by-subject basis. It is hypothesized that firing rates are manipulated by twitch force potentiation during contractions. Therefore, in this study we examined time-related changes in firing rates at steady force in relationship to motor unit recruitment threshold in the first dorsal interosseous and the influence of twitch force potentiation on such changes in young versus aged individuals. Subjects performed a 12 s steady-force contraction at 50% maximal voluntary contraction, with evoked twitches before and after the contraction to quantify potentiation. Firing rates, in relationship to recruitment thresholds, were determined at the beginning, middle and end of the steady force. There were no firing rate changes for aged individuals. For the young, firing rates decreased slightly for lower-threshold motor units but increased for higher-threshold motor units. Twitch force potentiation was greater for young than aged subjects, and changes in firing rates were correlated with twitch force potentiation. Thus, individuals with greater increases in firing rates of higher-threshold motor units and decreases in lower-threshold motor units possessed greater twitch force potentiation. Overall, changes in firing rates during brief steady-force contractions are dependent on recruitment threshold and explained in part by twitch force potentiation. Given that firing rate changes were measured in relationship to recruitment threshold, this study illustrates a more complete view of firing rate changes during steady-force contractions. © 2017 The Authors. Experimental Physiology © 2017 The Physiological Society.

Synchronization of presynaptic input to motor units of tongue, inspiratory intercostal, and diaphragm muscles.

PubMed

Rice, Amber; Fuglevand, Andrew J; Laine, Christopher M; Fregosi, Ralph F

2011-05-01

The respiratory central pattern generator distributes rhythmic excitatory input to phrenic, intercostal, and hypoglossal premotor neurons. The degree to which this input shapes motor neuron activity can vary across respiratory muscles and motor neuron pools. We evaluated the extent to which respiratory drive synchronizes the activation of motor unit pairs in tongue (genioglossus, hyoglossus) and chest-wall (diaphragm, external intercostals) muscles using coherence analysis. This is a frequency domain technique, which characterizes the frequency and relative strength of neural inputs that are common to each of the recorded motor units. We also examined coherence across the two tongue muscles, as our previous work shows that, despite being antagonists, they are strongly coactivated during the inspiratory phase, suggesting that excitatory input from the premotor neurons is distributed broadly throughout the hypoglossal motoneuron pool. All motor unit pairs showed highly correlated activity in the low-frequency range (1-8 Hz), reflecting the fundamental respiratory frequency and its harmonics. Coherence of motor unit pairs recorded either within or across the tongue muscles was similar, consistent with broadly distributed premotor input to the hypoglossal motoneuron pool. Interestingly, motor units from diaphragm and external intercostal muscles showed significantly higher coherence across the 10-20-Hz bandwidth than tongue-muscle units. We propose that the lower coherence in tongue-muscle motor units over this range reflects a larger constellation of presynaptic inputs, which collectively lead to a reduction in the coherence between hypoglossal motoneurons in this frequency band. This, in turn, may reflect the relative simplicity of the respiratory drive to the diaphragm and intercostal muscles, compared with the greater diversity of functions fulfilled by muscles of the tongue.

Task and fatigue effects on low-threshold motor units in human hand muscle.

PubMed

Enoka, R M; Robinson, G A; Kossev, A R

1989-12-01

1. The activity of single motor units was recorded in the first dorsal interosseus muscle of human subjects while they performed an isometric ramp-and-hold maneuver. Motor-unit activity was characterized before and after fatigue by the use of a branched bipolar electrode that was positioned subcutaneously over the test muscle. Activity was characterized in terms of the forces of recruitment and derecruitment and the discharge pattern. The purpose was to determine, before and after fatigue, whether motor-unit activity was affected by the direction in which the force was exerted. 2. Regardless of the task during prefatigue trials, interimpulse intervals were 1) more variable during increases or decreases in force than when force was held constant at the target value (4-6% above the recruitment force), and 2) more clustered around an arbitrary central value than would be expected with a normal (Gaussian) distribution. Both effects were seen during the flexion and abduction tasks. The behavior of low-threshold motor units in first dorsal interosseus is thus largely unaffected by the direction of the force exerted by the index finger. The absence of a task (i.e., a direction of force) effect suggests that the resultant force vector about the metacarpophalangeal joint of the index finger is not coded in terms of discrete populations of motor units, but, rather, it is based on the net muscle activity about the joint. 3. Motor-unit behavior during and after fatigue showed that the relatively homogeneous behavior seen before fatigue could be severely disrupted. The fatiguing protocol involved the continuous repetition, to the endurance limit, of a 15-s ramp-and-hold maneuver in which the abduction target force was 50% of maximum and was held for 10-s epochs (ramps up and down were approximately 2 s each). Motor-unit threshold was assessed by the forces of recruitment and derecruitment associated with each cycle of the fatigue test. Changes in recruitment force during the protocol were either minimal or, when present, not systematic. In contrast, the derecruitment force of all units exhibited a marked and progressive increase over the course of the test. 4. After the fatigue test, when the initial threshold tasks were repeated, the behavior of most motor units changed. These changes included the derecruitment of previously active motor units, the recruitment of additional motor units, and an increased discharge variability of units that remained recruited. The variation in recruitment order seemed to be much greater than that reported previously for nonfatiguing conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Ultra-Compact Motor Controller

NASA Technical Reports Server (NTRS)

Townsend, William T.; Crowell, Adam; Hauptman, Traveler; Pratt, Gill Andrews

2012-01-01

This invention is an electronically commutated brushless motor controller that incorporates Hall-array sensing in a small, 42-gram package that provides 4096 absolute counts per motor revolution position sensing. The unit is the size of a miniature hockey puck, and is a 44-pin male connector that provides many I/O channels, including CANbus, RS-232 communications, general-purpose analog and digital I/O (GPIO), analog and digital Hall inputs, DC power input (18-90 VDC, 0-l0 A), three-phase motor outputs, and a strain gauge amplifier. This controller replaces air cooling with conduction cooling via a high-thermal-conductivity epoxy casting. A secondary advantage of the relatively good heat conductivity that comes with ultra-small size is that temperature differences within the controller become smaller, so that it is easier to measure the hottest temperature in the controller with fewer temperature sensors, or even one temperature sensor. Another size-sensitive design feature is in the approach to electrical noise immunity. At a very small size, where conduction paths are much shorter than in conventional designs, the ground becomes essentially isopotential, and so certain (space-consuming) electrical noise control components become unnecessary, which helps make small size possible. One winding-current sensor, applied to all of the windings in fast sequence, is smaller and wastes less power than the two or more sensors conventionally used to sense and control winding currents. An unexpected benefit of using only one current sensor is that it actually improves the precision of current control by using the "same" sensors to read each of the three phases. Folding the encoder directly into the controller electronics eliminates a great deal of redundant electronics, packaging, connectors, and hook-up wiring. The reduction of wires and connectors subtracts substantial bulk and eliminates their role in behaving as EMI (electro-magnetic interference) antennas. A shared knowledge by each motor controller of the state of all the motors in the system at 500 Hz also allows parallel processing of higher-level kinematic matrix calculations.

Position versus force control: using the 2-DOF robotic ankle trainer to assess ankle's motor control.

PubMed

Farjadian, Amir B; Nabian, Mohsen; Hartman, Amber; Corsino, Johnathan; Mavroidis, Constantinos; Holden, Maureen K

2014-01-01

An estimated of 2,000,000 acute ankle sprains occur annually in the United States. Furthermore, ankle disabilities are caused by neurological impairments such as traumatic brain injury, cerebral palsy and stroke. The virtually interfaced robotic ankle and balance trainer (vi-RABT) was introduced as a cost-effective platform-based rehabilitation robot to improve overall ankle/balance strength, mobility and control. The system is equipped with 2 degrees of freedom (2-DOF) controlled actuation along with complete means of angle and torque measurement mechanisms. Vi-RABT was used to assess ankle strength, flexibility and motor control in healthy human subjects, while playing interactive virtual reality games on the screen. The results suggest that in the task with 2-DOF, subjects have better control over ankle's position vs. force.

Interaction of attentional and motor control processes in handwriting.

PubMed

Brown, T L; Donnenwirth, E E

1990-01-01

The interaction between attentional capacity, motor control processes, and strategic adaptations to changing task demands was investigated in handwriting, a continuous (rather than discrete) skilled performance. Twenty-four subjects completed 12 two-minute handwriting samples under instructions stressing speeded handwriting, normal handwriting, or highly legible handwriting. For half of the writing samples, a concurrent auditory monitoring task was imposed. Subjects copied either familiar (English) or unfamiliar (Latin) passages. Writing speed, legibility ratings, errors in writing and in the secondary auditory task, and a derived measure of the average number of characters held in short-term memory during each sample ("planning unit size") were the dependent variables. The results indicated that the ability to adapt to instructions stressing speed or legibility was substantially constrained by the concurrent listening task and by text familiarity. Interactions between instructions, task concurrence, and text familiarity in the legibility ratings, combined with further analyses of planning unit size, indicated that information throughput from temporary storage mechanisms to motor processes mediated the loss of flexibility effect. Overall, the results suggest that strategic adaptations of a skilled performance to changing task circumstances are sensitive to concurrent attentional demands and that departures from "normal" or "modal" performance require attention.

Maximization of Learning Speed in the Motor Cortex Due to Neuronal Redundancy

PubMed Central

Takiyama, Ken; Okada, Masato

2012-01-01

Many redundancies play functional roles in motor control and motor learning. For example, kinematic and muscle redundancies contribute to stabilizing posture and impedance control, respectively. Another redundancy is the number of neurons themselves; there are overwhelmingly more neurons than muscles, and many combinations of neural activation can generate identical muscle activity. The functional roles of this neuronal redundancy remains unknown. Analysis of a redundant neural network model makes it possible to investigate these functional roles while varying the number of model neurons and holding constant the number of output units. Our analysis reveals that learning speed reaches its maximum value if and only if the model includes sufficient neuronal redundancy. This analytical result does not depend on whether the distribution of the preferred direction is uniform or a skewed bimodal, both of which have been reported in neurophysiological studies. Neuronal redundancy maximizes learning speed, even if the neural network model includes recurrent connections, a nonlinear activation function, or nonlinear muscle units. Furthermore, our results do not rely on the shape of the generalization function. The results of this study suggest that one of the functional roles of neuronal redundancy is to maximize learning speed. PMID:22253586

A new two-phase homopolar switched reluctance motor for electric vehicle applications

NASA Astrophysics Data System (ADS)

Tsai, Mi-Ching; Huang, Chien-Chin; Huang, Zheng-Yi

2003-12-01

This paper presents a novel 2-phase homopolar switched reluctance motor (SRM), whose design successfully avoids dead-zone problems that afflict low cost 1- and/or 2-phase SRMs. Unlike conventional radial-winding-radial-gap motors, the proposed SRM has an interior stator that is of the pancake type with axial winding. Such a design allows for a high slot-fill factor and is suitable for implementation as a flat pancake-shaped stator. An efficient, compact prototype was produced with TMS320F240 DSP driving control unit. Experimental results indicate that the present SRM design has the potential to be used for electric bicycles and scooters.

The human cerebellum: a review of physiologic neuroanatomy.

PubMed

Roostaei, Tina; Nazeri, Arash; Sahraian, Mohammad Ali; Minagar, Alireza

2014-11-01

The cerebellum resides in the posterior cranial fossa dorsal to the brainstem and has diverse connections to the cerebrum, brain stem, and spinal cord. It is anatomically and physiologically divided into distinct functional compartments and is composed of highly regular arrays of neuronal units, each sharing the same basic cerebellar microcircuitry. Its circuitry is critically involved in motor control and motor learning, and its role in nonmotor cognitive and affective functions is becoming increasingly recognized. This article describes the cerebellar gross and histologic neuroanatomy in relation to its function, and the relevance of cerebellar circuitry and firing patterns to motor learning. Copyright © 2014 Elsevier Inc. All rights reserved.

Feedback Signal from Motoneurons Influences a Rhythmic Pattern Generator.

PubMed

Rotstein, Horacio G; Schneider, Elisa; Szczupak, Lidia

2017-09-20

Motoneurons are not mere output units of neuronal circuits that control motor behavior but participate in pattern generation. Research on the circuit that controls the crawling motor behavior in leeches indicated that motoneurons participate as modulators of this rhythmic motor pattern. Crawling results from successive bouts of elongation and contraction of the whole leech body. In the isolated segmental ganglia, dopamine can induce a rhythmic antiphasic activity of the motoneurons that control contraction (DE-3 motoneurons) and elongation (CV motoneurons). The study was performed in isolated ganglia where manipulation of the activity of specific motoneurons was performed in the course of fictive crawling ( crawling ). In this study, the membrane potential of CV was manipulated while crawling was monitored through the rhythmic activity of DE-3. Matching behavioral observations that show that elongation dominates the rhythmic pattern, the electrophysiological activity of CV motoneurons dominates the cycle. Brief excitation of CV motoneurons during crawling episodes resets the rhythmic activity of DE-3, indicating that CV feeds back to the rhythmic pattern generator. CV hyperpolarization accelerated the rhythm to an extent that depended on the magnitude of the cycle period, suggesting that CV exerted a positive feedback on the unit(s) of the pattern generator that controls the elongation phase. A simple computational model was implemented to test the consequences of such feedback. The simulations indicate that the duty cycle of CV depended on the strength of the positive feedback between CV and the pattern generator circuit. SIGNIFICANCE STATEMENT Rhythmic movements of animals are controlled by neuronal networks that have been conceived as hierarchical structures. At the basis of this hierarchy, we find the motoneurons, few neurons at the top control global aspects of the behavior (e.g., onset, duration); and within these two ends, specific neuronal circuits control the actual rhythmic pattern of movements. We have investigated whether motoneurons are limited to function as output units. Analysis of the network that controls crawling behavior in the leech has clearly indicated that motoneurons, in addition to controlling muscle activity, send signals to the pattern generator. Physiological and modeling studies on the role of specific motoneurons suggest that these feedback signals modulate the phase relationship of the rhythmic activity. Copyright © 2017 the authors 0270-6474/17/379149-11$15.00/0.

Variations in motor unit recruitment patterns occur within and between muscles in the running rat (Rattus norvegicus).

PubMed

Hodson-Tole, E F; Wakeling, J M

2007-07-01

Motor units are generally considered to follow a set, orderly pattern of recruitment within each muscle with activation occurring in the slowest through to the fastest units. A growing body of evidence, however, suggests that recruitment patterns may not always follow such an orderly sequence. Here we investigate whether motor unit recruitment patterns vary within and between the ankle extensor muscles of the rat running at 40 cm s(-1) on a level treadmill. In the past it has been difficult to quantify motor unit recruitment patterns during locomotion; however, recent application of wavelet analysis techniques has made such detailed analysis of motor unit recruitment possible. Here we present methods for quantifying the interplay of fast and slow motor unit recruitment based on their myoelectric signals. Myoelectric data were collected from soleus, plantaris and medial gastrocnemius muscles representing populations of slow, mixed and fast fibres, respectively, and providing a good opportunity to relate myoelectric frequency content to motor unit recruitment patterns. Following wavelet transformation, principal component analysis quantified signal intensity and relative frequency content. Significant differences in signal frequency content occurred between different time points within a stride (P<0.001). We optimised high- and low-frequency wavelets to the major signals from the fast and slow motor units. The goodness-of-fit of the optimised wavelets to the signal intensity was high for all three muscles (r2>0.98). The low-frequency band had a significantly better fit to signals from the soleus muscle (P<0.001), while the high-frequency band had a significantly better fit to the medial gastrocnemius (P<0.001).

Audio-vocal interaction in single neurons of the monkey ventrolateral prefrontal cortex.

PubMed

Hage, Steffen R; Nieder, Andreas

2015-05-06

Complex audio-vocal integration systems depend on a strong interconnection between the auditory and the vocal motor system. To gain cognitive control over audio-vocal interaction during vocal motor control, the PFC needs to be involved. Neurons in the ventrolateral PFC (VLPFC) have been shown to separately encode the sensory perceptions and motor production of vocalizations. It is unknown, however, whether single neurons in the PFC reflect audio-vocal interactions. We therefore recorded single-unit activity in the VLPFC of rhesus monkeys (Macaca mulatta) while they produced vocalizations on command or passively listened to monkey calls. We found that 12% of randomly selected neurons in VLPFC modulated their discharge rate in response to acoustic stimulation with species-specific calls. Almost three-fourths of these auditory neurons showed an additional modulation of their discharge rates either before and/or during the monkeys' motor production of vocalization. Based on these audio-vocal interactions, the VLPFC might be well positioned to combine higher order auditory processing with cognitive control of the vocal motor output. Such audio-vocal integration processes in the VLPFC might constitute a precursor for the evolution of complex learned audio-vocal integration systems, ultimately giving rise to human speech. Copyright © 2015 the authors 0270-6474/15/357030-11$15.00/0.

Motor responses and weight gaining in neonates through use of two methods of earmuff and receiving silence in NICU.

PubMed

Abdeyazdan, Z; Ghasemi, S; Marofi, M; Berjis, N

2014-01-01

With technological advances in NICUs the survival rate of preterm infants has been increased. Because NICU environment is a potent source of stress for infants, its modification is an essential measure to decrease infants' morbidity. The purposes of this study were to compare the effects of wearing earmuff and provision silence for infants on their motor responses and gaining weight. In a randomized clinical trial 96 preterm infants were enrolled. Their motor responses were evaluated for two consecutive days in the morning and afternoon shifts, in the groups of earmuff and silence, and at similar time points in the control group. Also their weight was measured at days 1 and 10. In the two intervention groups, means of motor responses in infants were significantly less than in the control group, and weight gain of infants was more than the control group. However weight gain was more pronounced in the earmuff group. Both interventions led to decreasing number of motor responses and improvement of weight gain pattern, but these effects were more pronounced in earmuff group; thus because implementation of silence in NICUs has many barriers, it is suggested to use earmuff for preterm infants in these units. This trial obtained IRCT registration number IRCT2012092010812N2.

Gesture Based Control and EMG Decomposition

NASA Technical Reports Server (NTRS)

Wheeler, Kevin R.; Chang, Mindy H.; Knuth, Kevin H.

2005-01-01

This paper presents two probabilistic developments for use with Electromyograms (EMG). First described is a new-electric interface for virtual device control based on gesture recognition. The second development is a Bayesian method for decomposing EMG into individual motor unit action potentials. This more complex technique will then allow for higher resolution in separating muscle groups for gesture recognition. All examples presented rely upon sampling EMG data from a subject's forearm. The gesture based recognition uses pattern recognition software that has been trained to identify gestures from among a given set of gestures. The pattern recognition software consists of hidden Markov models which are used to recognize the gestures as they are being performed in real-time from moving averages of EMG. Two experiments were conducted to examine the feasibility of this interface technology. The first replicated a virtual joystick interface, and the second replicated a keyboard. Moving averages of EMG do not provide easy distinction between fine muscle groups. To better distinguish between different fine motor skill muscle groups we present a Bayesian algorithm to separate surface EMG into representative motor unit action potentials. The algorithm is based upon differential Variable Component Analysis (dVCA) [l], [2] which was originally developed for Electroencephalograms. The algorithm uses a simple forward model representing a mixture of motor unit action potentials as seen across multiple channels. The parameters of this model are iteratively optimized for each component. Results are presented on both synthetic and experimental EMG data. The synthetic case has additive white noise and is compared with known components. The experimental EMG data was obtained using a custom linear electrode array designed for this study.

Morphological Characteristics of Motor Neurons Do Not Determine Their Relative Susceptibility to Degeneration in a Mouse Model of Severe Spinal Muscular Atrophy

PubMed Central

Mutsaers, Chantal A.; Thomson, Derek; Hamilton, Gillian; Parson, Simon H.; Gillingwater, Thomas H.

2012-01-01

Spinal muscular atrophy (SMA) is a leading genetic cause of infant mortality, resulting primarily from the degeneration and loss of lower motor neurons. Studies using mouse models of SMA have revealed widespread heterogeneity in the susceptibility of individual motor neurons to neurodegeneration, but the underlying reasons remain unclear. Data from related motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), suggest that morphological properties of motor neurons may regulate susceptibility: in ALS larger motor units innervating fast-twitch muscles degenerate first. We therefore set out to determine whether intrinsic morphological characteristics of motor neurons influenced their relative vulnerability to SMA. Motor neuron vulnerability was mapped across 10 muscle groups in SMA mice. Neither the position of the muscle in the body, nor the fibre type of the muscle innervated, influenced susceptibility. Morphological properties of vulnerable and disease-resistant motor neurons were then determined from single motor units reconstructed in Thy.1-YFP-H mice. None of the parameters we investigated in healthy young adult mice – including motor unit size, motor unit arbor length, branching patterns, motor endplate size, developmental pruning and numbers of terminal Schwann cells at neuromuscular junctions - correlated with vulnerability. We conclude that morphological characteristics of motor neurons are not a major determinant of disease-susceptibility in SMA, in stark contrast to related forms of motor neuron disease such as ALS. This suggests that subtle molecular differences between motor neurons, or extrinsic factors arising from other cell types, are more likely to determine relative susceptibility in SMA. PMID:23285108

Low-frequency oscillations of the neural drive to the muscle are increased with experimental muscle pain

PubMed Central

Negro, Francesco; Gizzi, Leonardo; Falla, Deborah

2012-01-01

We investigated the influence of nociceptive stimulation on the accuracy of task execution and motor unit spike trains during low-force isometric contractions. Muscle pain was induced by infusion of hypertonic saline into the abductor digiti minimi muscle of 11 healthy men. Intramuscular EMG signals were recorded from the same muscle during four isometric contractions of 60-s duration at 10% of the maximal force [maximal voluntary contraction (MVC)] performed before injection (baseline), after injection of isotonic (control) or hypertonic saline (pain), and 15 min after pain was no longer reported. Each contraction was preceded by three 3-s ramp contractions from 0% to 10% MVC. The low-frequency oscillations of motor unit spike trains were analyzed by the first principal component of the low-pass filtered spike trains [first common component (FCC)], which represents the effective neural drive to the muscle. Pain decreased the accuracy of task performance [coefficient of variation (CoV) for force: baseline, 2.8 ± 1.8%, pain, 3.9 ± 1.8%; P < 0.05] and reduced motor unit discharge rates [11.6 ± 2.3 pulses per second (pps) vs. 10.7 ± 1.7 pps; P < 0.05]. Motor unit recruitment thresholds (2.2 ± 1.2% MVC vs. 2.4 ± 1.6% MVC), interspike interval variability (18.4 ± 4.9% vs. 19.1 ± 5.4%), strength of motor unit short-term synchronization [common input strength (CIS) 1.02 ± 0.44 vs. 0.83 ± 0.22], and strength of common drive (0.47 ± 0.08 vs. 0.47 ± 0.06) did not change across conditions. The FCC signal was correlated with force (R = 0.45 ± 0.06), and the CoV for FCC increased in the painful condition (5.69 ± 1.29% vs. 7.83 ± 2.61%; P < 0.05). These results indicate that nociceptive stimulation increased the low-frequency variability in synaptic input to motoneurons. PMID:22049336

Autonomous berthing/unberthing of a Work Attachment Mechanism/Work Attachment Fixture (WAM/WAF)

NASA Technical Reports Server (NTRS)

Nguyen, Charles C.; Antrazi, Sami S.

1992-01-01

Discussed here is the autonomous berthing of a Work Attachment Mechanism/Work Attachment Fixture (WAM/WAF) developed by NASA for berthing and docking applications in space. The WAM/WAF system enables fast and reliable berthing (unberthing) of space hardware. A successful operation of the WAM/WAF requires that the WAM motor velocity be precisely controlled. The operating principle and the design of the WAM/WAF is described as well as the development of a control system used to regulate the WAM motor velocity. The results of an experiment in which the WAM/WAF is used to handle an orbital replacement unit are given.

Eccentric muscle damage has variable effects on motor unit recruitment thresholds and discharge patterns in elbow flexor muscles.

PubMed

Dartnall, Tamara J; Rogasch, Nigel C; Nordstrom, Michael A; Semmler, John G

2009-07-01

The purpose of this study was to determine the effect of eccentric muscle damage on recruitment threshold force and repetitive discharge properties of low-threshold motor units. Ten subjects performed four tasks involving isometric contraction of elbow flexors while electromyographic (EMG) data were recorded from human biceps brachii and brachialis muscles. Tasks were 1) maximum voluntary contraction (MVC); 2) constant-force contraction at various submaximal targets; 3) motor unit recruitment threshold task; and 4) minimum motor unit discharge rate task. These tasks were performed on three separate days before, immediately after, and 24 h after eccentric exercise of elbow flexor muscles. MVC force declined (42%) immediately after exercise and remained depressed (29%) 24 h later, indicative of muscle damage. Mean motor unit recruitment threshold for biceps brachii was 8.4+/-4.2% MVC, (n=34) before eccentric exercise, and was reduced by 41% (5.0+/-3.0% MVC, n=34) immediately after and by 39% (5.2+/-2.5% MVC, n=34) 24 h after exercise. No significant changes in motor unit recruitment threshold were observed in the brachialis muscle. However, for the minimum tonic discharge rate task, motor units in both muscles discharged 11% faster (10.8+/-2.0 vs. 9.7+/-1.7 Hz) immediately after (n=29) exercise compared with that before (n=32). The minimum discharge rate variability was greater in brachialis muscle immediately after exercise (13.8+/-3.1%) compared with that before (11.9+/-3.1%) and 24 h after exercise (11.7+/-2.4%). No significant changes in minimum discharge rate variability were observed in the biceps brachii motor units after exercise. These results indicate that muscle damage from eccentric exercise alters motor unit recruitment thresholds for >or=24 h, but the effect is not the same in the different elbow flexor muscles.

The impact of football training on motor development in male children.

PubMed

Erceg, Marko; Zagorac, Nebojsa; Katić, Ratko

2008-03-01

The aim of the study was to determine the effect of football school program and physical education curriculum on changes in the motor abilities of 7- and 8-year-old boys. The study included a sample of 180 boys divided into group 1 (7-year-old boys), subdivided to experimental (n = 40) and control (n = 50) groups, and group 2 (8-year-old boys), subdivided to experimental (n = 40) and control (n = 50) groups. Experimental groups included children attending three training units of football training over a 9-month period, in addition to the conventional physical education curriculum. Control groups included children attending only conventional physical education curriculum. All study subjects underwent testing with a battery of 12 motor tests at the beginning and at the end of the study. Results obtained by discriminative canonic analysis showed no statistically significant between-group difference in motor abilities at the beginning of the study. However, significant differences in favor of experimental groups were recorded at the end of the study. Favorable changes in all motor variables were observed in both experimental and control groups of children from the initial through the final state. These changes were more pronounced in experimental groups. Analysis of variance for difference variables (final to initial measurement) indicated programmed education in the form of football training in addition to regular physical education curriculum to predominantly influence the development of aerobic endurance, agility, speed and flexibility in 7-year-old boys, and of explosive strength, aerobic endurance, flexibility and speed in 8-year-old boys. In the latter, football training led to the formation of a motor complex integrating explosiveness, speed, coordination, endurance and flexibility as a general motor factor determining future quality development in football.

A Novel Framework Based on FastICA for High Density Surface EMG Decomposition

PubMed Central

Chen, Maoqi; Zhou, Ping

2015-01-01

This study presents a progressive FastICA peel-off (PFP) framework for high density surface electromyogram (EMG) decomposition. The novel framework is based on a shift-invariant model for describing surface EMG. The decomposition process can be viewed as progressively expanding the set of motor unit spike trains, which is primarily based on FastICA. To overcome the local convergence of FastICA, a “peel off” strategy (i.e. removal of the estimated motor unit action potential (MUAP) trains from the previous step) is used to mitigate the effects of the already identified motor units, so more motor units can be extracted. Moreover, a constrained FastICA is applied to assess the extracted spike trains and correct possible erroneous or missed spikes. These procedures work together to improve the decomposition performance. The proposed framework was validated using simulated surface EMG signals with different motor unit numbers (30, 70, 91) and signal to noise ratios (SNRs) (20, 10, 0 dB). The results demonstrated relatively large numbers of extracted motor units and high accuracies (high F1-scores). The framework was also tested with 111 trials of 64-channel electrode array experimental surface EMG signals during the first dorsal interosseous (FDI) muscle contraction at different intensities. On average 14.1 ± 5.0 motor units were identified from each trial of experimental surface EMG signals. PMID:25775496

Selection and parameterization of cortical neurons for neuroprosthetic control.

PubMed

Wahnoun, Remy; He, Jiping; Helms Tillery, Stephen I

2006-06-01

When designing neuroprosthetic interfaces for motor function, it is crucial to have a system that can extract reliable information from available neural signals and produce an output suitable for real life applications. Systems designed to date have relied on establishing a relationship between neural discharge patterns in motor cortical areas and limb movement, an approach not suitable for patients who require such implants but who are unable to provide proper motor behavior to initially tune the system. We describe here a method that allows rapid tuning of a population vector-based system for neural control without arm movements. We trained highly motivated primates to observe a 3D center-out task as the computer played it very slowly. Based on only 10-12 s of neuronal activity observed in M1 and PMd, we generated an initial mapping between neural activity and device motion that the animal could successfully use for neuroprosthetic control. Subsequent tunings of the parameters led to improvements in control, but the initial selection of neurons and estimated preferred direction for those cells remained stable throughout the remainder of the day. Using this system, we have observed that the contribution of individual neurons to the overall control of the system is very heterogeneous. We thus derived a novel measure of unit quality and an indexing scheme that allowed us to rate each neuron's contribution to the overall control. In offline tests, we found that fewer than half of the units made positive contributions to the performance. We tested this experimentally by having the animals control the neuroprosthetic system using only the 20 best neurons. We found that performance in this case was better than when the entire set of available neurons was used. Based on these results, we believe that, with careful task design, it is feasible to parameterize control systems without any overt behaviors and that subsequent control system design will be enhanced with cautious unit selection. These improvements can lead to systems demanding lower bandwidth and computational power, and will pave the way for more feasible clinical systems.

Motor unit number estimation and quantitative needle electromyography in stroke patients.

PubMed

Kouzi, Ioanna; Trachani, Eftichia; Anagnostou, Evangelos; Rapidi, Christina-Anastasia; Ellul, John; Sakellaropoulos, George C; Chroni, Elisabeth

2014-12-01

To evaluate the effect of upper motor neuron damage upon motor units' function by means of two separate and supplementary electrophysiological methods. The abductor digiti minimi muscle of the non-paretic and the paretic side was studied in forty-six stroke patients with (a) motor unit number estimation (MUNE) - adapted multiple point stimulation method and (b) computerized quantitative needle electromyography (EMG) assessing the configuration of voluntary recruited motor unit potentials. Main outcome comparisons were focused on differences between non-paretic and paretic side. On the affected hands mean MUNE value was significantly lower and mean area of the surface recorded single motor unit potentials was significantly larger than the corresponding ones on the non-paretic hands. EMG findings did not reveal remarkable differences between the two sides. Neither severity nor chronicity of stroke was related to MUNE or EMG parameters. MUNE results, which suggested reduced motor unit numbers in stroke patients, in conjunction with the normal EMG features in these same muscles has given rise to different interpretations. In a clinical setting, reinnervation type changes in the EMG similar to that occurring in neuronopathies or axonal neuropathies should not be expected in muscles with central neurogenic lesion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interplay of upper and lower motor neuron degeneration in amyotrophic lateral sclerosis.

PubMed

de Carvalho, Mamede; Poliakov, Artiom; Tavares, Cristiano; Swash, Michael

2017-11-01

We studied motor unit recruitment to test a new method to identify motor unit firing rate (FR) variability. We studied 68 ALS patients, with and without upper neuron signs (UMN) in lower limbs, 24 patients with primary lateral sclerosis (PLS), 13 patients with spinal cord lesion and 39 normal subjects. All recordings were made from tibialis anterior muscles of normal strength. Subjects performed a very slight contraction in order to activate 2 motor units in each recording. 5-7 motor unit pairs were recorded in each subject. Mean consecutive differences (MCD) were calculated for each pair of potentials. The mean MCD for each muscle was estimated as the mean from the total number of pairs recorded. Ap value<0.01 was accepted as significant. MCD of FR frequency was less in the subjects with spinal cord lesion and PLS. In addition, the FR frequency of the 1st motor unit in a pair of units was markedly reduced in PLS, and in subjects with spinal cord lesions. These results support a lower threshold and reduced FR fluctuation in spinal motor neurons of spastic patients. This method can be developed for detection of UMN lesions. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

49 CFR 1572.201 - Transportation of hazardous materials via commercial motor vehicle from Canada or Mexico to and...

Code of Federal Regulations, 2010 CFR

2010-10-01

... commercial motor vehicle from Canada or Mexico to and within the United States. 1572.201 Section 1572.201... ASSESSMENTS Transportation of Hazardous Materials From Canada or Mexico To and Within the United States by... Mexico to and within the United States. (a) Applicability. This section applies to commercial motor...

33 CFR 183.33 - Maximum weight capacity: Inboard and inboard-outdrive boats.

Code of Federal Regulations, 2010 CFR

2010-07-01

... (iv) Weight of full permanent fuel tanks. (3) “Machinery weight” is the combined weight of installed engines or motors, control equipment, drive units, and batteries. [CGD 72-61R, 37 FR 15782, Aug. 4, 1972...

Motor unit recruitment and firing rate in medial gastrocnemius muscles during external perturbations in standing in humans.

PubMed

Pollock, C L; Ivanova, T D; Hunt, M A; Garland, S J

2014-10-01

There is limited investigation of the interaction between motor unit recruitment and rate coding for modulating force during standing or responding to external perturbations. Fifty-seven motor units were recorded from the medial gastrocnemius muscle with intramuscular electrodes in response to external perturbations in standing. Anteriorly directed perturbations were generated by applying loads in 0.45-kg increments at the pelvis every 25-40 s until 2.25 kg was maintained. Motor unit firing rate was calculated for the initial recruitment load and all subsequent loads during two epochs: 1) dynamic response to perturbation directly following each load drop and 2) maintenance of steady state between perturbations. Joint kinematics and surface electromyography (EMG) from lower extremities and force platform measurements were assessed. Application of the external loads resulted in a significant forward progression of the anterior-posterior center of pressure (AP COP) that was accompanied by modest changes in joint angles (<3°). Surface EMG increased more in medial gastrocnemius than in the other recorded muscles. At initial recruitment, motor unit firing rate immediately after the load drop was significantly lower than during subsequent load drops or during the steady state at the same load. There was a modest increase in motor unit firing rate immediately after the load drop on subsequent load drops associated with regaining balance. There was no effect of maintaining balance with increased load and forward progression of the AP COP on steady-state motor unit firing rate. The medial gastrocnemius utilized primarily motor unit recruitment to achieve the increased levels of activation necessary to maintain standing in the presence of external loads. Copyright © 2014 the American Physiological Society.

Asynchronous recruitment of low-threshold motor units during repetitive, low-current stimulation of the human tibial nerve

PubMed Central

Dean, Jesse C.; Clair-Auger, Joanna M.; Lagerquist, Olle; Collins, David F.

2014-01-01

Motoneurons receive a barrage of inputs from descending and reflex pathways. Much of our understanding about how these inputs are transformed into motor output in humans has come from recordings of single motor units during voluntary contractions. This approach, however, is limited because the input is ill-defined. Herein, we quantify the discharge of soleus motor units in response to well-defined trains of afferent input delivered at physiologically-relevant frequencies. Constant frequency stimulation of the tibial nerve (10–100 Hz for 30 s), below threshold for eliciting M-waves or H-reflexes with a single pulse, recruited motor units in 7/9 subjects. All 25 motor units recruited during stimulation were also recruited during weak (<10% MVC) voluntary contractions. Higher frequencies recruited more units (n = 3/25 at 10 Hz; n = 25/25 at 100 Hz) at shorter latencies (19.4 ± 9.4 s at 10 Hz; 4.1 ± 4.0 s at 100 Hz) than lower frequencies. When a second unit was recruited, the discharge of the already active unit did not change, suggesting that recruitment was not due to increased synaptic drive. After recruitment, mean discharge rate during stimulation at 20 Hz (7.8 Hz) was lower than during 30 Hz (8.6 Hz) and 40 Hz (8.4 Hz) stimulation. Discharge was largely asynchronous from the stimulus pulses with “time-locked” discharge occurring at an H-reflex latency with only a 24% probability. Motor units continued to discharge after cessation of the stimulation in 89% of trials, although at a lower rate (5.8 Hz) than during the stimulation (7.9 Hz). This work supports the idea that the afferent volley evoked by repetitive stimulation recruits motor units through the integration of synaptic drive and intrinsic properties of motoneurons, resulting in “physiological” recruitment which adheres to Henneman’s size principle and results in relatively low discharge rates and asynchronous firing. PMID:25566025

Asynchronous recruitment of low-threshold motor units during repetitive, low-current stimulation of the human tibial nerve.

PubMed

Dean, Jesse C; Clair-Auger, Joanna M; Lagerquist, Olle; Collins, David F

2014-01-01

Motoneurons receive a barrage of inputs from descending and reflex pathways. Much of our understanding about how these inputs are transformed into motor output in humans has come from recordings of single motor units during voluntary contractions. This approach, however, is limited because the input is ill-defined. Herein, we quantify the discharge of soleus motor units in response to well-defined trains of afferent input delivered at physiologically-relevant frequencies. Constant frequency stimulation of the tibial nerve (10-100 Hz for 30 s), below threshold for eliciting M-waves or H-reflexes with a single pulse, recruited motor units in 7/9 subjects. All 25 motor units recruited during stimulation were also recruited during weak (<10% MVC) voluntary contractions. Higher frequencies recruited more units (n = 3/25 at 10 Hz; n = 25/25 at 100 Hz) at shorter latencies (19.4 ± 9.4 s at 10 Hz; 4.1 ± 4.0 s at 100 Hz) than lower frequencies. When a second unit was recruited, the discharge of the already active unit did not change, suggesting that recruitment was not due to increased synaptic drive. After recruitment, mean discharge rate during stimulation at 20 Hz (7.8 Hz) was lower than during 30 Hz (8.6 Hz) and 40 Hz (8.4 Hz) stimulation. Discharge was largely asynchronous from the stimulus pulses with "time-locked" discharge occurring at an H-reflex latency with only a 24% probability. Motor units continued to discharge after cessation of the stimulation in 89% of trials, although at a lower rate (5.8 Hz) than during the stimulation (7.9 Hz). This work supports the idea that the afferent volley evoked by repetitive stimulation recruits motor units through the integration of synaptic drive and intrinsic properties of motoneurons, resulting in "physiological" recruitment which adheres to Henneman's size principle and results in relatively low discharge rates and asynchronous firing.

Final Report: MaRSPlus Sensor System Electrical Cable Management and Distributed Motor Control Computer Interface

NASA Technical Reports Server (NTRS)

Reil, Robin

2011-01-01

The success of JPL's Next Generation Imaging Spectrometer (NGIS) in Earth remote sensing has inspired a follow-on instrument project, the MaRSPlus Sensor System (MSS). One of JPL's responsibilities in the MSS project involves updating the documentation from the previous JPL airborne imagers to provide all the information necessary for an outside customer to operate the instrument independently. As part of this documentation update, I created detailed electrical cabling diagrams to provide JPL technicians with clear and concise build instructions and a database to track the status of cables from order to build to delivery. Simultaneously, a distributed motor control system is being developed for potential use on the proposed 2018 Mars rover mission. This system would significantly reduce the mass necessary for rover motor control, making more mass space available to other important spacecraft systems. The current stage of the project consists of a desktop computer talking to a single "cold box" unit containing the electronics to drive a motor. In order to test the electronics, I developed a graphical user interface (GUI) using MATLAB to allow a user to send simple commands to the cold box and display the responses received in a user-friendly format.

Light-induced propulsion of a giant liposome driven by peptide nanofibre growth.

PubMed

Inaba, Hiroshi; Uemura, Akihito; Morishita, Kazushi; Kohiki, Taiki; Shigenaga, Akira; Otaka, Akira; Matsuura, Kazunori

2018-04-19

Light-driven nano/micromotors are attracting much attention, not only as molecular devices but also as components of bioinspired robots. In nature, several pathogens such as Listeria use actin polymerisation machinery for their propulsion. Despite the development of various motors, it remains challenging to mimic natural systems to create artificial motors propelled by fibre formation. Herein, we report the propulsion of giant liposomes driven by light-induced peptide nanofibre growth on their surface. Peptide-DNA conjugates connected by a photocleavage unit were asymmetrically introduced onto phase-separated giant liposomes. Ultraviolet (UV) light irradiation cleaved the conjugates and released peptide units, which self-assembled into nanofibres, driving the translational movement of the liposomes. The velocity of the liposomes reflected the rates of the photocleavage reaction and subsequent fibre formation of the peptide-DNA conjugates. These results showed that chemical design of the light-induced peptide nanofibre formation is a useful approach to fabricating bioinspired motors with controllable motility.

The effect of inertial loading on wrist postural tremor in essential tremor.

PubMed

Héroux, M E; Pari, G; Norman, K E

2009-05-01

Determine the effect of inertial loading on the strength of motor unit entrainment and the synergistic/competitive interaction between central and mechanical reflex tremor components in subjects with essential tremor (ET). Twenty-three subjects with ET and 22 controls held their hand in an outstretched position while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Hand postural tremor and wrist extensor neuromuscular activity were recorded. Inertial loading resulted in a reduction in postural tremor in all ET subjects. The largest reduction in tremor amplitude occurred between 5% and 15% loads, which was associated with spectral separation of the mechanical reflex and central tremor components in a large number of ET subjects. Despite an increase in overall neuromuscular activity with inertial loading, EMG tremor spectral power did not increase with loading. The effect of inertial loading on postural tremor amplitude appears to be mediated in large part by its effect on the interaction between mechanical reflex and central tremor components. Also, ET is associated with a constant absolute level of motor unit entrainment. The amplitude of postural tremor is dependent on both central and peripheral factors, with proportionally greater motor unit entrainment occurring at low contraction intensities.

Rotor dynamic behaviour of a high-speed oil-free motor compressor with a rigid coupling supported on four radial magnetic bearings

NASA Technical Reports Server (NTRS)

Schmied, J.; Pradetto, J. C.

1994-01-01

The combination of a high-speed motor, dry gas seals, and magnetic bearings realized in this unit facilitates the elimination of oil. The motor is coupled with a quill shaft to the compressor. This yields higher natural frequencies of the rotor than with the use of a diaphragm coupling and helps to maintain a sufficient margin of the maximum speed to the frequency of the second compressor bending mode. However, the controller of each bearing then has to take the combined modes of both machines into account. The requirements for the controller to ensure stability and sufficient damping of all critical speeds are designed and compared with the implemented controller. The calculated closed loop behavior was confirmed experimentally, except the stability of some higher modes due to slight frequency deviations of the rotor model to the actual rotor. The influence of a mechanical damper as a device to provide additional damping to high models is demonstrated theoretically. After all, it was not necessary to install the damper, since all modes cold be stabilized by the controller.

A cognitive movement scientist's view on the link between thought and action: insights from the "Badische Zimmer" metaphor.

PubMed

Hossner, Ernst-Joachim

2009-01-01

The problem of a bidirectional link between thought and action is approached from the perspective of cognitive movement science. The metaphor of the "Badische Zimmer" - an adaptation of Searle's Chinese room metaphor - is used to illustrate shortcomings in the classical conception of linear information processing and to introduce some features which current theories of movement control and learning should embrace. On this basis, the case is made for a return to an ideomotor view of motor control and learning based on effect prediction (E') as a function of the situational context (S') and one's own motor responses (R'). The relevance of the derived concept of sensorimotor chains linking elementary S'R'E' units in the course of motor learning is finally discussed with respect to potential implications for an integrative theory of perception, action, and decision making.

Design and control of one precise tracking simulation bed for Chinese 20/30 meter optic/infrared telescope

NASA Astrophysics Data System (ADS)

Ren, Changzhi; Li, Xiaoyan; Song, Xiaoli; Niu, Yong; Li, Aihua; Zhang, Zhenchao

2012-09-01

Direct drive technology is the key to solute future 30-m and larger telescope motion system to guarantee a very high tracking accuracy, in spite of unbalanced and sudden loads such as wind gusts and in spite of a structure that, because of its size, can not be infinitely stiff. However, this requires the design and realization of unusually large torque motor that the torque slew rate must be extremely steep too. A conventional torque motor design appears inadequate. This paper explores one redundant unit permanent magnet synchronous motor and its simulation bed for 30-m class telescope. Because its drive system is one high integrated electromechanical system, one complexly electromechanical design method is adopted to improve the efficiency, reliability and quality of the system during the design and manufacture circle. This paper discusses the design and control of the precise tracking simulation bed in detail.

The propulsive design aspects on the world's first direct drive hybrid airplane

NASA Astrophysics Data System (ADS)

Nanda, Ankit

The purpose of this thesis is to design a safe technology demonstrator by implementing a direct drive propulsion system for a gas-electric hybrid aircraft. This system was integrated on the Embry-Riddle Eco-Eagle for the Green Flight Challenge 2011. The aim of the system is to allow the pilot to use the electric motor as an independent power source to fly the aircraft once at cruise altitude, while having a gas engine to allow for higher power capability. The system was designed to incorporate the motor and the motor control unit provided by Flight Design and Drivetek AG alongside a Rotax 912ULS engine. The hardware is integrated such that the pilot would be able to fly the aircraft with controls similar to conventional general aviation aircraft. This thesis discusses the method of integration of the hybrid powerplant system into a Stemme S-10 and describes the various components of that system.

Design and Evaluation of a Fully Implantable Control Unit for Blood Pumps

PubMed Central

Unthan, Kristin; Gräf, Felix; Laumen, Marco; Finocchiaro, Thomas; Sommer, Christoph; Lanmüller, Hermann; Steinseifer, Ulrich

2015-01-01

As the number of donor hearts is limited while more and more patients suffer from end stage biventricular heart failure, Total Artificial Hearts become a promising alternative to conventional treatment. While pneumatic devices sufficiently supply the patients with blood flow, the patient's quality of life is limited by the percutaneous pressure lines and the size of the external control unit. This paper describes the development of the control unit of the ReinHeart, a fully implantable Total Artificial Heart. General requirements for any implantable control unit are defined from a technical and medical point of view: necessity of a Transcutaneous Energy Transmission, autonomous operation, safety, geometry, and efficiency. Based on the requirements, a prototype is designed; it incorporates a LiFePo4 battery pack with charger, a rectifier for transcutaneous energy transmission, the motor's driver electronics, and a microcontroller which monitors and controls all functions. In validation tests, the control unit demonstrated a stable operation on TET and battery supply and a safe switching from one supply to the other. The overall mean efficiency is 14% on TET and 22% on battery supply. The control unit is suitable for chronic animal trials of the ReinHeart. PMID:26583095

Randomized controlled trial of strength training in post-polio patients.

PubMed

Chan, K Ming; Amirjani, Nasim; Sumrain, Mae; Clarke, Anita; Strohschein, Fay J

2003-03-01

Many post-polio patients develop new muscle weakness decades after the initial illness. However, its mechanism and treatment are controversial. The purpose of this study was to test the hypotheses that: (1) after strength training, post-polio patients show strength improvement comparable to that seen in the healthy elderly; (2) such training does not have a deleterious effect on motor unit (MU) survival; and (3) part of the strength improvement is due to an increase in voluntary motor drive. After baseline measures including maximum voluntary contraction force, voluntary activation index, motor unit number estimate, and the tetanic tension of the thumb muscles had been determined, 10 post-polio patients with hand involvement were randomized to either the training or control group. The progressive resistance training program consisted of three sets of eight isometric contractions, three times weekly for 12 weeks. Seven healthy elderly were also randomized and trained in a similar manner. Changes in the baseline parameters were monitored once every 4 weeks throughout the training period. The trained post-polio patients showed a significant improvement in their strength (P < 0.05). The magnitude of gain was greater than that seen in the healthy elderly (mean +/- SE, 41 +/- 16% vs. 29 +/- 8%). The training did not adversely affect MU survival and the improvement was largely attributable to an increase in voluntary motor drive. We therefore conclude that moderate intensity strength training is safe and effective in post-polio patients.

Totally implantable total artificial heart and ventricular assist device with multipurpose miniature electromechanical energy system.

PubMed

Takatani, S; Orime, Y; Tasai, K; Ohara, Y; Naito, K; Mizuguchi, K; Makinouchi, K; Damm, G; Glueck, J; Ling, J

1994-01-01

A multipurpose miniature electromechanical energy system has been developed to yield a compact, efficient, durable, and biocompatible total artificial heart (TAH) and ventricular assist device (VAD). Associated controller-driver electronics were recently miniaturized and converted into hybrid circuits. The hybrid controller consists of a microprocessor and controller, motor driver, Hall sensor, and commutation circuit hybrids. The sizing study demonstrated that all these components can be incorporated in the pumping unit of the TAH and VAD, particularly in the centerpiece of the TAH and the motor housing of the VAD. Both TAH and VAD pumping units will start when their power line is connected to either the internal power pack or the external battery unit. As a redundant driving and diagnostic port, an emergency port was newly added and will be placed in subcutaneous location. In case of system failure, the skin will be cut down, and an external motor drive or a pneumatic driver will be connected to this port to run the TAH. This will minimize the circulatory arrest time. Overall efficiency of the TAH without the transcutaneous energy transmission system was 14-18% to deliver pump outputs of 4-9 L/min against the right and left afterload pressures of 25 and 100 mm Hg. The internal power requirement ranged from 6 to 13 W. The rechargeable batteries such as NiCd or NiMH with 1 AH capacity can run the TAH for 30-45 min. The external power requirement, when TETS efficiency of 75% was assumed, ranged from 8 to 18 W. The accelerated endurance test in the 42 degrees C saline bath demonstrated stable performance over 4 months. Long-term endurance and chronic animal studies will continue toward a system with 5 years durability by the year 2000.

Experimental muscle pain increases variability of neural drive to muscle and decreases motor unit coherence in tremor frequency band.

PubMed

Yavuz, Utku Ş; Negro, Francesco; Falla, Deborah; Farina, Dario

2015-08-01

It has been observed that muscle pain influences force variability and low-frequency (<3 Hz) oscillations in the neural drive to muscle. In this study, we aimed to investigate the effect of experimental muscle pain on the neural control of muscle force at higher frequency bands, associated with afferent feedback (alpha band, 5-13 Hz) and with descending cortical input (beta band, 15-30 Hz). Single-motor unit activity was recorded, in two separate experimental sessions, from the abductor digiti minimi (ADM) and tibialis anterior (TA) muscles with intramuscular wire electrodes, during isometric abductions of the fifth finger at 10% of maximal force [maximum voluntary contraction (MVC)] and ankle dorsiflexions at 25% MVC. The contractions were repeated under three conditions: no pain (baseline) and after intramuscular injection of isotonic (0.9%, control) and hypertonic (5.8%, painful) saline. The results showed an increase of the relative power of both the force signal and the neural drive at the tremor frequency band (alpha, 5-13 Hz) between the baseline and hypertonic (painful) conditions for both muscles (P < 0.05) but no effect on the beta band. Additionally, the strength of motor unit coherence was lower (P < 0.05) in the hypertonic condition in the alpha band for both muscles and in the beta band for the ADM. These results indicate that experimental muscle pain increases the amplitude of the tremor oscillations because of an increased variability of the neural control (common synaptic input) in the tremor band. Moreover, the concomitant decrease in coherence suggests an increase in independent input in the tremor band due to pain. Copyright © 2015 the American Physiological Society.

Common drive to the upper airway muscle genioglossus during inspiratory loading

PubMed Central

Woods, Michael J.; Nicholas, Christian L.; Semmler, John G.; Chan, Julia K. M.; Jordan, Amy S.

2015-01-01

Common drive is thought to constitute a central mechanism by which the efficiency of a motor neuron pool is increased. This study tested the hypothesis that common drive to the upper airway muscle genioglossus (GG) would increase with increased respiratory drive in response to an inspiratory load. Respiration, GG electromyographic (EMG) activity, single-motor unit activity, and coherence in the 0–5 Hz range between pairs of GG motor units were assessed for the 30 s before an inspiratory load, the first and second 30 s of the load, and the 30 s after the load. Twelve of twenty young, healthy male subjects provided usable data, yielding 77 pairs of motor units: 2 Inspiratory Phasic, 39 Inspiratory Tonic, 15 Expiratory Tonic, and 21 Tonic. Respiratory and GG inspiratory activity significantly increased during the loads and returned to preload levels during the postload periods (all showed significant quadratic functions over load trials, P < 0.05). As hypothesized, common drive increased during the load in inspiratory modulated motor units to a greater extent than in expiratory/tonic motor units (significant load × discharge pattern interaction, P < 0.05). Furthermore, this effect persisted during the postload period. In conclusion, common drive to inspiratory modulated motor units was elevated in response to increased respiratory drive. The postload elevation in common drive was suggestive of a poststimulus activation effect. PMID:26378207

Gross Motor Development in Children Aged 3-5 Years, United States 2012.

PubMed

Kit, Brian K; Akinbami, Lara J; Isfahani, Neda Sarafrazi; Ulrich, Dale A

2017-07-01

Objective Gross motor development in early childhood is important in fostering greater interaction with the environment. The purpose of this study is to describe gross motor skills among US children aged 3-5 years using the Test of Gross Motor Development (TGMD-2). Methods We used 2012 NHANES National Youth Fitness Survey (NNYFS) data, which included TGMD-2 scores obtained according to an established protocol. Outcome measures included locomotor and object control raw and age-standardized scores. Means and standard errors were calculated for demographic and weight status with SUDAAN using sample weights to calculate nationally representative estimates, and survey design variables to account for the complex sampling methods. Results The sample included 339 children aged 3-5 years. As expected, locomotor and object control raw scores increased with age. Overall mean standardized scores for locomotor and object control were similar to the mean value previously determined using a normative sample. Girls had a higher mean locomotor, but not mean object control, standardized score than boys (p < 0.05). However, the mean locomotor standardized scores for both boys and girls fell into the range categorized as "average." There were no other differences by age, race/Hispanic origin, weight status, or income in either of the subtest standardized scores (p > 0.05). Conclusions In a nationally representative sample of US children aged 3-5 years, TGMD-2 mean locomotor and object control standardized scores were similar to the established mean. These results suggest that standardized gross motor development among young children generally did not differ by demographic or weight status.

Estimates of Commercial Motor Vehicles Using the Southwest Border Crossings

DOT National Transportation Integrated Search

2000-09-20

The United States has experienced almost a five-fold increase in commercial motor vehicle traffic to and from Mexico during the past sixteen years. There were more than 4< million commercial motor vehicle (CMV) crossings from Mexico into the United S...

Effects of aging and Parkinson's disease on motor unit remodeling: influence of resistance exercise training.

PubMed

Kelly, Neil A; Hammond, Kelley G; Bickel, C Scott; Windham, Samuel T; Tuggle, S Craig; Bamman, Marcas M

2018-04-01

Aging muscle atrophy is in part a neurodegenerative process revealed by denervation/reinnervation events leading to motor unit remodeling (i.e., myofiber type grouping). However, this process and its physiological relevance are poorly understood, as is the wide-ranging heterogeneity among aging humans. Here, we attempted to address 1) the relation between myofiber type grouping and molecular regulators of neuromuscular junction (NMJ) stability; 2) the impact of motor unit remodeling on recruitment during submaximal contractions; 3) the prevalence and impact of motor unit remodeling in Parkinson's disease (PD), an age-related neurodegenerative disease; and 4) the influence of resistance exercise training (RT) on regulators of motor unit remodeling. We compared type I myofiber grouping, molecular regulators of NMJ stability, and the relative motor unit activation (MUA) requirement during a submaximal sit-to-stand task among untrained but otherwise healthy young (YA; 26 yr, n = 27) and older (OA; 66 yr, n = 91) adults and OA with PD (PD; 67 yr, n = 19). We tested the effects of RT on these outcomes in OA and PD. PD displayed more motor unit remodeling, alterations in NMJ stability regulation, and a higher relative MUA requirement than OA, suggesting PD-specific effects. The molecular and physiological outcomes tracked with the severity of type I myofiber grouping. Together these findings suggest that age-related motor unit remodeling, manifested by type I myofiber grouping, 1) reduces MUA efficiency to meet submaximal contraction demand, 2) is associated with disruptions in NMJ stability, 3) is further impacted by PD, and 4) may be improved by RT in severe cases. NEW & NOTEWORTHY Because the physiological consequences of varying amounts of myofiber type grouping are unknown, the current study aims to characterize the molecular and physiological correlates of motor unit remodeling. Furthermore, because exercise training has demonstrated neuromuscular benefits in aged humans and improved innervation status and neuromuscular junction integrity in animals, we provide an exploratory analysis of the effects of high-intensity resistance training on markers of neuromuscular degeneration in both Parkinson's disease (PD) and age-matched older adults.

Impacts of P-f & Q-V Droop Control on MicroGrids Transient Stability

NASA Astrophysics Data System (ADS)

Zhao-xia, Xiao; Hong-wei, Fang

Impacts of P-f & Q-V droop control on MicroGrid transient stability was investigated with a wind unit of asynchronous generator in the MicroGrid. The system frequency stability was explored when the motor load starts and its load power changes, and faults of different types and different locations occurs. The simulations were done by PSCAD/EMTDC.

Adaptive Control Responses to Behavioral Perturbation Based Upon the Insect

DTIC Science & Technology

2006-11-01

the legs. Visual Sensors Antennal Mechanosensors Antennal Chemosensors Descending Interneurons Controlling Yaw...animals, the antenna were moved back and forth several times with servo motors to identify units that respond to antennal movement in either direction or...role of antennal postures and movements in plume tracking behavior. To date, results have shown that male moths tracking plumes in different wind

A Randomized Controlled Trial for Children with Childhood Apraxia of Speech Comparing Rapid Syllable Transition Treatment and the Nuffield Dyspraxia Programme-Third Edition

ERIC Educational Resources Information Center

Murray, Elizabeth; McCabe, Patricia; Ballard, Kirrie J.

2015-01-01

Purpose: This randomized controlled trial compared the experimental Rapid Syllable Transition (ReST) treatment to the Nuffield Dyspraxia Programme-Third Edition (NDP3; Williams & Stephens, 2004), used widely in clinical practice in Australia and the United Kingdom. Both programs aim to improve speech motor planning/programming for children…

Detail, unit 4, 3,000 hp synchronous pump motor. Manufactured by ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail, unit 4, 3,000 hp synchronous pump motor. Manufactured by The Electric Products Company, Cleveland, Ohio. Unit 5 is identical to this unit - Wellton-Mohawk Irrigation System, Pumping Plant No. 2, Bounded by Interstate 8 to south, Wellton, Yuma County, AZ

Organization of the motor-unit pool for different directions of isometric contraction of the first dorsal interosseous muscle.

PubMed

Lei, Yuming; Suresh, Nina L; Rymer, William Z; Hu, Xiaogang

2018-01-01

Muscle force generation involves recruitment and firing rate modulation of motor units (MUs). The control of MUs in producing multidirectional forces remains unclear. We studied MU recruitment and firing properties, recorded from the first dorsal interosseous muscle, for 3 different directions of contraction: abduction; abduction/flexion combination; and flexion. MUs were recruited systematically at higher threshold force during flexion. Larger MUs were recruited and firing rates of MUs were lower during abduction. There was an orderly recruitment of MUs according to MU size regardless of contraction direction, obeying the "size principle." Firing rates of earlier-recruited MUs were consistently higher than later-recruited MUs, affirming the "onion-skin" property. Our findings suggest that the size principle and onion-skin organization together provide a general description of MU recruitment patterns and firing properties. The directional alternations of MU control properties likely reflect changes in neural drive to the muscle. Muscle Nerve 57: E85-E93, 2018. © 2017 Wiley Periodicals, Inc.

A software package for interactive motor unit potential classification using fuzzy k-NN classifier.

PubMed

Rasheed, Sarbast; Stashuk, Daniel; Kamel, Mohamed

2008-01-01

We present an interactive software package for implementing the supervised classification task during electromyographic (EMG) signal decomposition process using a fuzzy k-NN classifier and utilizing the MATLAB high-level programming language and its interactive environment. The method employs an assertion-based classification that takes into account a combination of motor unit potential (MUP) shapes and two modes of use of motor unit firing pattern information: the passive and the active modes. The developed package consists of several graphical user interfaces used to detect individual MUP waveforms from a raw EMG signal, extract relevant features, and classify the MUPs into motor unit potential trains (MUPTs) using assertion-based classifiers.

Association between Late-Life Social Activity and Motor Decline in Older Adults

PubMed Central

Buchman, Aron S.; Boyle, Patricia A.; Wilson, Robert S.; Fleischman, Debra A.; Leurgans, Sue; Bennett, David A.

2009-01-01

Background Loss of motor function is a common consequence of aging, but little is known about factors that predict idiopathic motor decline. Methods We studied 906 persons without dementia, history of stroke or Parkinson's disease participating in the Rush Memory and Aging Project. At baseline, they rated their frequency of participation in common social activities. Outcome was annual change in global motor function, based on nine measures of muscle strength and nine motor performances. Results Mean social activity score at baseline was 2.6 (SD=0.58), with higher scores indicating more frequent participation in social activities. In a generalized estimating equation model, controlling for age, sex and education, motor function declined by about 0.05 unit/year [Estimate, 0.016; 95%CI (-0.057, -0.041); p=0.017]. Each 1-point decrease in social activity was associated with about a 33% more rapid rate of decline in motor function [Estimate, 0.016; 95%CI (0.003, 0.029); p=0.017)]. This amount of annual motor decline was associated with a more than 40% increased risk of death (Hazard Ratio: 1.44; 95%CI: 1.30, 1.60) and 65% increased risk of incident Katz disability (Hazard Ratio: 1.65; 95%CI: 1.48, 1.83). The association of social activity with change in motor function did not vary along demographic lines and was unchanged after controlling for potential confounders including late-life physical and cognitive activity, disability, global cognition, depressive symptoms, body composition and chronic medical conditions [Estimate, 0.025; 95%CI (0.005, 0.045); p=0.010]. Conclusion Less frequent participation in social activities is associated with a more rapid rate of motor decline in old age. PMID:19546415

Enhanced Motor Imagery-Based BCI Performance via Tactile Stimulation on Unilateral Hand.

PubMed

Shu, Xiaokang; Yao, Lin; Sheng, Xinjun; Zhang, Dingguo; Zhu, Xiangyang

2017-01-01

Brain-computer interface (BCI) has attracted great interests for its effectiveness in assisting disabled people. However, due to the poor BCI performance, this technique is still far from daily-life applications. One of critical issues confronting BCI research is how to enhance BCI performance. This study aimed at improving the motor imagery (MI) based BCI accuracy by integrating MI tasks with unilateral tactile stimulation (Uni-TS). The effects were tested on both healthy subjects and stroke patients in a controlled study. Twenty-two healthy subjects and four stroke patients were recruited and randomly divided into a control-group and an enhanced-group. In the control-group, subjects performed two blocks of conventional MI tasks (left hand vs. right hand), with 80 trials in each block. In the enhanced-group, subjects also performed two blocks of MI tasks, but constant tactile stimulation was applied on the non-dominant/paretic hand during MI tasks in the second block. We found the Uni-TS significantly enhanced the contralateral cortical activations during MI of the stimulated hand, whereas it had no influence on activation patterns during MI of the non-stimulated hand. The two-class BCI decoding accuracy was significantly increased from 72.5% (MI without Uni-TS) to 84.7% (MI with Uni-TS) in the enhanced-group ( p < 0.001, paired t -test). Moreover, stroke patients in the enhanced-group achieved an accuracy >80% during MI with Uni-TS. This novel approach complements the conventional methods for BCI enhancement without increasing source information or complexity of signal processing. This enhancement via Uni-TS may facilitate clinical applications of MI-BCI.

Determinants of gross motor skill performance in children with visual impairments.

PubMed

Haibach, Pamela S; Wagner, Matthias O; Lieberman, Lauren J

2014-10-01

Children with visual impairments (CWVI) generally perform poorer in gross motor skills when compared with their sighted peers. This study examined the influence of age, sex, and severity of visual impairment upon locomotor and object control skills in CWVI. Participants included 100 CWVI from across the United States who completed the Test of Gross Motor Development II (TGMD-II). The TGMD-II consists of 12 gross motor skills including 6 object control skills (catching, kicking, striking, dribbling, throwing, and rolling) and 6 locomotor skills (running, sliding, galloping, leaping, jumping, and hopping). The full range of visual impairments according to United States Association for Blind Athletes (USABA; B3=20/200-20/599, legally blind; B2=20/600 and up, travel vision; B1=totally blind) were assessed. The B1 group performed significantly worse than the B2 (0.000 ≤ p ≤ 0.049) or B3 groups (0.000 ≤ p ≤ 0.005); however, there were no significant differences between B2 and B3 except for the run (p=0.006), catch (p=0.000), and throw (p=0.012). Age and sex did not play an important role in most of the skills, with the exception of boys outperforming girls striking (p=0.009), dribbling (p=0.013), and throwing (p=0.000), and older children outperforming younger children in dribbling (p=0.002). The significant impact of the severity of visual impairment is likely due to decreased experiences and opportunities for children with more severe visual impairments. In addition, it is likely that these reduced experiences explain the lack of age-related differences in the CWVI. The large disparities in performance between children who are blind and their partially sighted peers give direction for instruction and future research. In addition, there is a critical need for intentional and specific instruction on motor skills at a younger age to enable CWVI to develop their gross motor skills. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of manual therapy on treatment duration and motor development in infants with severe nonsynostotic plagiocephaly: a randomised controlled pilot study.

PubMed

Cabrera-Martos, I; Valenza, M C; Valenza-Demet, G; Benítez-Feliponi, A; Robles-Vizcaíno, C; Ruiz-Extremera, A

2016-11-01

Despite growing evidence regarding nonsynostotic plagiocephaly and their repercussions on motor development, there is little evidence to support the use of manual therapy as an adjuvant option. The aim of this study was to evaluate the effects of a therapeutic approach based on manual therapy as an adjuvant option on treatment duration and motor development in infants with severe nonsynostotic plagiocephaly. This is a randomised controlled pilot study. The study was conducted at a university hospital. Forty-six infants with severe nonsynostotic plagiocephaly (types 4-5 of the Argenta scale) referred to the Early Care and Monitoring Unit were randomly allocated to a control group receiving standard treatment (repositioning and an orthotic helmet) or to an experimental group treated with manual therapy added to standard treatment. Infants were discharged when the correction of the asymmetry was optimal taken into account the previous clinical characteristics. The outcome measures were treatment duration and motor development assessed with the Alberta Infant Motor Scale (AIMS) at baseline and at discharge. Asymmetry after the treatment was minimal (type 0 or 1 according to the Argenta scale) in both groups. A comparative analysis showed that treatment duration was significantly shorter (p < 0.001) in the experimental group (109.84 ± 14.45 days) compared to the control group (148.65 ± 11.53 days). The motor behaviour was normal (scores above the 16th percentile of the AIMS) in all the infants after the treatment. Manual therapy added to standard treatment reduces the treatment duration in infants with severe nonsynostotic plagiocephaly.

Mirror therapy in chronic stroke survivors with severely impaired upper limb function: a randomized controlled trial.

PubMed

Colomer, Carolina; NOé, Enrique; Llorens, Roberto

2016-06-01

Mirror therapy (MT) has been proposed to improve the motor function of chronic individuals with stroke with mild to moderate impairment. With regards to severe upper limb paresis, MT has shown to provide limited motor improvement in the acute or sub-acute phase. However, no previous research has described the effects of MT in chronic individuals with stroke with severely impaired upper limb function. The aim of this study was to determine the effectiveness of MT on chronic stroke survivors with severe upper-limb impairment in comparison with passive mobilization. A randomized controlled trial. Rehabilitative outpatient unit. A total of 31 chronic subjects poststroke with severely impaired upper limb function were randomly assigned to either an experimental group (N.=15), or a control group (N.=16). Twenty-four intervention sessions were performed for both groups. Each session included 45-minute period of MT (experimental group) or passive mobilization (control group), administered three days a week. Participants were assessed before and after the intervention with the Wolf Motor Function Test, the Fugl-Meyer Assessment, and the Nottingham Sensory Assessment. Improvement in motor function was observed in both groups on the time (P=0.002) and ability (P=0.001) subscales of the Wolf Motor Function Test. No differences were detected in kinesthesis or stereognosis. However, the experimental group showed a significant improvement in tactile sensation that was mainly observed as an increased sensitivity to light touches. In comparison with passive mobilization, MT in chronic stroke survivors with severely impaired upper-limb function may provide a limited but positive effect on light touch sensitivity while providing similar motor improvement. MT is a therapeutic approach that can be used in the rehabilitation of severely impaired upper limb in chronic stroke survivors, specifically to address light touch sensitivity deficits.

Firing patterns of spontaneously active motor units in spinal cord-injured subjects.

PubMed

Zijdewind, Inge; Thomas, Christine K

2012-04-01

Involuntary motor unit activity at low rates is common in hand muscles paralysed by spinal cord injury. Our aim was to describe these patterns of motor unit behaviour in relation to motoneurone and motor unit properties. Intramuscular electromyographic activity (EMG), surface EMG and force were recorded for 30 min from thenar muscles of nine men with chronic cervical SCI. Motor units fired for sustained periods (>10 min) at regular (coefficient of variation ≤ 0.15, CV, n =19 units) or irregular intervals (CV>0.15, n =14). Regularly firing units started and stopped firing independently suggesting that intrinsic motoneurone properties were important for recruitment and derecruitment. Recruitment (3.6 Hz, SD 1.2), maximal (10.2 Hz, SD 2.3, range: 7.5-15.4 Hz) and derecruitment frequencies were low (3.3 Hz, SD 1.6), as were firing rate increases after recruitment (~20 intervals in 3 s). Once active, firing often covaried, promoting the idea that units received common inputs.Half of the regularly firing units showed a very slow decline (>40 s) in discharge before derecruitment and had interspike intervals longer than their estimated after hyperpolarisation potential (AHP) duration (estimated by death rate and breakpoint analyses). The other units were derecruited more abruptly and had shorter estimated AHP durations. Overall, regularly firing units had longer estimated AHP durations and were weaker than irregularly firing units, suggesting they were lower threshold units. Sustained firing of units at regular rates may reflect activation of persistent inward currents, visible here in the absence of voluntary drive, whereas irregularly firing units may only respond to synaptic noise.

49 CFR 565.24 - Motor vehicles imported into the United States.

Code of Federal Regulations, 2013 CFR

2013-10-01

... HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION VEHICLE IDENTIFICATION NUMBER (VIN) REQUIREMENTS Alternative VIN Requirements In Effect for Limited Period § 565.24 Motor vehicles imported into... 49 Transportation 6 2013-10-01 2013-10-01 false Motor vehicles imported into the United States...

49 CFR 565.24 - Motor vehicles imported into the United States.

Code of Federal Regulations, 2011 CFR

2011-10-01

... HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION VEHICLE IDENTIFICATION NUMBER (VIN) REQUIREMENTS Alternative VIN Requirements In Effect for Limited Period § 565.24 Motor vehicles imported into... 49 Transportation 6 2011-10-01 2011-10-01 false Motor vehicles imported into the United States...

49 CFR 565.24 - Motor vehicles imported into the United States.

Code of Federal Regulations, 2014 CFR

2014-10-01

... HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION VEHICLE IDENTIFICATION NUMBER (VIN) REQUIREMENTS Alternative VIN Requirements In Effect for Limited Period § 565.24 Motor vehicles imported into... 49 Transportation 6 2014-10-01 2014-10-01 false Motor vehicles imported into the United States...

49 CFR 565.24 - Motor vehicles imported into the United States.

Code of Federal Regulations, 2012 CFR

2012-10-01

... HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION VEHICLE IDENTIFICATION NUMBER (VIN) REQUIREMENTS Alternative VIN Requirements In Effect for Limited Period § 565.24 Motor vehicles imported into... 49 Transportation 6 2012-10-01 2012-10-01 false Motor vehicles imported into the United States...

49 CFR 565.24 - Motor vehicles imported into the United States.

Code of Federal Regulations, 2010 CFR

2010-10-01

... HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION VEHICLE IDENTIFICATION NUMBER (VIN) REQUIREMENTS Alternative VIN Requirements In Effect for Limited Period § 565.24 Motor vehicles imported into... 49 Transportation 6 2010-10-01 2010-10-01 false Motor vehicles imported into the United States...

Motor unit recruitment patterns 1: responses to changes in locomotor velocity and incline.

PubMed

Hodson-Tole, Emma F; Wakeling, James M

2008-06-01

Mammalian skeletal muscles are composed of a mixture of motor unit types, which contribute a range of mechanical and physiological properties to the muscle. For a muscle to effectively contribute to smooth, co-ordinated movement it must activate an appropriate number and combination of motor units to generate the required force over a suitable time period. Much evidence exists indicating that motor units are activated in an orderly fashion, from the slowest through to the fastest. A growing body of evidence, however, indicates that such a recruitment strategy does not always hold true. Here we investigate how motor unit recruitment patterns were influenced by changes in locomotor velocity and incline. Kinematics data and myoelectric signals were collected from three rat ankle extensor muscles during running on a treadmill at nine velocity and incline combinations. Wavelet and principal component analysis were used to simultaneously decompose the signals into time and frequency space. The relative frequency components of the signals were quantified during 20 time windows of a stride from each locomotor condition. Differences in signal frequency components existed between muscles and locomotor conditions. Faster locomotor velocities led to a relative increase in high frequency components, whereas greater inclines led to a relative increase in the low frequency components. These data were interpreted as representing changes in motor unit recruitment patterns in response to changes in the locomotor demand. Motor units were not always recruited in an orderly manner, indicating that recruitment is a multi-factorial phenomenon that is not yet fully understood.

Load type influences motor unit recruitment in biceps brachii during a sustained contraction.

PubMed

Baudry, Stéphane; Rudroff, Thorsten; Pierpoint, Lauren A; Enoka, Roger M

2009-09-01

Twenty subjects participated in four experiments designed to compare time to task failure and motor-unit recruitment threshold during contractions sustained at 15% of maximum as the elbow flexor muscles either supported an inertial load (position task) or exerted an equivalent constant torque against a rigid restraint (force task). Subcutaneous branched bipolar electrodes were used to record single motor unit activity from the biceps brachii muscle during ramp contractions performed before and at 50 and 90% of the time to failure for the position task during both fatiguing contractions. The time to task failure was briefer for the position task than for the force task (P=0.0002). Thirty and 29 motor units were isolated during the force and position tasks, respectively. The recruitment threshold declined by 48 and 30% (P=0.0001) during the position task for motor units with an initial recruitment threshold below and above the target force, respectively, whereas no significant change in recruitment threshold was observed during the force task. Changes in recruitment threshold were associated with a decrease in the mean discharge rate (-16%), an increase in discharge rate variability (+40%), and a prolongation of the first two interspike intervals (+29 and +13%). These data indicate that there were faster changes in motor unit recruitment and rate coding during the position task than the force task despite a similar net muscle torque during both tasks. Moreover, the results suggest that the differential synaptic input observed during the position task influences most of the motor unit pool.

Cycling injury risk in London: A case-control study exploring the impact of cycle volumes, motor vehicle volumes, and road characteristics including speed limits.

PubMed

Aldred, Rachel; Goodman, Anna; Gulliver, John; Woodcock, James

2018-08-01

Cycling injury risk is an important topic, but few studies explore cycling risk in relation to exposure. This is largely because of a lack of exposure data, in other words how much cycling is done at different locations. This paper helps to fill this gap. It reports a case-control study of cycling injuries in London in 2013-2014, using modelled cyclist flow data alongside datasets covering some characteristics of the London route network. A multilevel binary logistic regression model is used to investigate factors associated with injury risk, comparing injury sites with control sites selected using the modelled flow data. Findings provide support for 'safety in numbers': for each increase of a natural logarithmic unit (2.71828) in cycling flows, an 18% decrease in injury odds was found. Conversely, increased motor traffic volume is associated with higher odds of cycling injury, with one logarithmic unit increase associated with a 31% increase in injury odds. Twenty-mile per hour compared with 30mph speed limits were associated with 21% lower injury odds. Residential streets were associated with reduced injury odds, and junctions with substantially higher injury odds. Bus lanes do not affect injury odds once other factors are controlled for. These data suggest that speed limits of 20 mph may reduce cycling injury risk, as may motor traffic reduction. Further, building cycle routes that generate new cycle trips should generate 'safety in numbers' benefits. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

A randomized trial evaluation of the Oswestry Standing Frame for patients after stroke.

PubMed

Bagley, Pam; Hudson, Mary; Forster, Anne; Smith, Jane; Young, John

2005-06-01

Standing is believed to have benefits in addressing motor and sensory impairments after stroke. One device to facilitate standing for severely disabled patients is the Oswestry Standing Frame. To evaluate the effectiveness of the Oswestry Standing Frame for severely disabled stroke patients. A single centre, randomized controlled trial. An inpatient stroke rehabilitation unit. Patients were recruited if they had a clinical diagnosis of stroke, were medically stable and unable to achieve any score on the Trunk Control Test or unable to stand in mid-line without the assistance of two therapists. The intervention (n = 71) and control (n = 69) groups both received usual stroke unit care but the intervention group also received a minimum of 14 consecutive days' treatment using the standing frame. The primary outcome measure was the Rivermead Mobility Index (RMI). Secondary measures included the Barthel Index; the Rivermead Motor Assessment; the balanced sitting and sitting to standing components of the Motor Assessment Scale; the Trunk Control Test and the Hospital Anxiety and Depression Scale. Blind assessment was undertaken at baseline, six weeks, 12 weeks and six months post stroke. Information on resource use was also collected. There was no statistically significant difference between groups in any of the outcome measures or for resource use. Mann-Whitney U-tests for the RMI change from baseline scores to six weeks, 12 weeks and six months post stroke were p = 0.310; p = 0.970 and p = 0.282, respectively. Use of the Oswestry Standing Frame did not improve clinical outcome or provide resource savings for this severely disabled patient group.

Detail, unit 3, 1,100 horsepower (hp) pump motor. Manufactured by ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail, unit 3, 1,100 horsepower (hp) pump motor. Manufactured by the Electric Products Company, Cleveland, Ohio, USA. Units 1,2, and 4 are identical to this unit - Wellton-Mohawk Irrigation System, Pumping Plant No. 1, Bounded by Gila River & Union Pacific Railroad, Wellton, Yuma County, AZ

The vastus lateralis neuromuscular activity during all-out cycling exercise.

PubMed

Bercier, Stephane; Halin, Renaud; Ravier, Philippe; Kahn, Jean-Francois; Jouanin, Jean-Claude; Lecoq, Anne-Marie; Buttelli, Olivier

2009-10-01

The objective of this work was to study modifications in motor control through surface electromyographic (sEMG) activity during a very short all-out cycling exercise. Twelve male cyclists (age 23+/-4 years) participated in this study. After a warm-up period, each subject performed three all-out cycling exercises of 6s separated by 2 min of complete rest. This protocol was repeated three times with a minimum of 2 days between each session. The braking torque imposed on cycling motion was 19 Nm. The sEMG of the vastus lateralis was recorded during the first seven contractions of the sprint. Time-frequency analysis of sEMG was performed using continuous wavelet transform. The mean power frequency (MPF, qualitative modifications in the recruitment of motor units) and signal energy (a quantitative indicator of modifications in the motor units recruitment) were computed for the frequency range 10-500 Hz. sEMG energy increased (P0.05) between contraction number 1 and 2, decreased (P < or =0.05) between contraction number 2 and 3 then stabilized between contraction number 3 and 7 during the all-out test. MPF increased (P < or =0.05) during the all-out test. This increase was more marked during the first two contractions. The decrease in energy and the increase in the sEMG MPF suggest a large spatial recruitment of motor units (MUs) at the beginning of the sprint followed by a preferential recruitment of faster MUs at the end of the sprint, respectively.

Flight and Walking in Locusts–Cholinergic Co-Activation, Temporal Coupling and Its Modulation by Biogenic Amines

PubMed Central

Rillich, Jan; Stevenson, Paul A.; Pflueger, Hans-Joachim

2013-01-01

Walking and flying in locusts are exemplary rhythmical behaviors generated by central pattern generators (CPG) that are tuned in intact animals by phasic sensory inputs. Although these two behaviors are mutually exclusive and controlled by independent CPGs, leg movements during flight can be coupled to the flight rhythm. To investigate potential central coupling between the underlying CPGs, we used the muscarinic agonist pilocarpine and the amines octopamine and tyramine to initiate fictive flight and walking in deafferented locust preparations. Our data illustrate that fictive walking is readily evoked by comparatively lower concentrations of pilocarpine, whereas higher concentrations are required to elicit fictive flight. Interestingly, fictive flight did not suppress fictive walking so that the two patterns were produced simultaneously. Frequently, leg motor units were temporally coupled to the flight rhythm, so that each spike in a step cycle volley occurred synchronously with wing motor units firing at flight rhythm frequency. Similarly, tyramine also induced fictive walking and flight, but mostly without any coupling between the two rhythms. Octopamine in contrast readily evoked fictive flight but generally failed to elicit fictive walking. Despite this, numerous leg motor units were recruited, whereby each was temporarily coupled to the flight rhythm. Our results support the notion that the CPGs for walking and flight are largely independent, but that coupling can be entrained by aminergic modulation. We speculate that octopamine biases the whole motor machinery of a locust to flight whereas tyramine primarily promotes walking. PMID:23671643

Near Field Antenna Measurement System.

DTIC Science & Technology

1982-03-01

is 2" in diameter, the others are 1". The shafts are mounted to the structure with specially- designed adjusters which provide two axes of control for...program when a supplier was found who provided an entire motor and controller system designed for direct computer interfacing. These units, Control ...distribution unlimited. "The findings in this report are not to be construed as an official Department of the Army position unless so designated by other

Fluctuations in isometric muscle force can be described by one linear projection of low-frequency components of motor unit discharge rates

PubMed Central

Negro, Francesco; Holobar, Aleš; Farina, Dario

2009-01-01

The aim of the study was to investigate the relation between linear transformations of motor unit discharge rates and muscle force. Intramuscular (wire electrodes) and high-density surface EMG (13 × 5 electrode grid) were recorded from the abductor digiti minimi muscle of eight healthy men during 60 s contractions at 5%, 7.5% and 10% of the maximal force. Spike trains of a total of 222 motor units were identified from the EMG recordings with decomposition algorithms. Principal component analysis of the smoothed motor unit discharge rates indicated that one component (first common component, FCC) described 44.2 ± 7.5% of the total variability of the smoothed discharge rates when computed over the entire contraction interval and 64.3 ± 10.2% of the variability when computed over 5 s intervals. When the FCC was computed from four or more motor units per contraction, it correlated with the force produced by the muscle (62.7 ± 10.1%) by a greater degree (P < 0.001) than the smoothed discharge rates of individual motor units (41.4 ± 7.8%). The correlation between FCC and the force signal increased up to 71.8 ± 13.1% when the duration and the shape of the smoothing window for discharge rates were similar to the average motor unit twitch force. Moreover, the coefficients of variation (CoV) for the force and for the FCC signal were correlated in all subjects (R2 range = 0.14–0.56; P < 0.05) whereas the CoV for force was correlated to the interspike interval variability in only one subject (R2= 0.12; P < 0.05). Similar results were further obtained from measures on the tibialis anterior muscle of an additional eight subjects during contractions at forces up to 20% of the maximal force (e.g. FCC explained 59.8 ± 11.0% of variability of the smoothed discharge rates). In conclusion, one signal captures most of the underlying variability of the low-frequency components of motor unit discharge rates and explains large part of the fluctuations in the motor output during isometric contractions. PMID:19840996

Fluctuations in isometric muscle force can be described by one linear projection of low-frequency components of motor unit discharge rates.

PubMed

Negro, Francesco; Holobar, Ales; Farina, Dario

2009-12-15

The aim of the study was to investigate the relation between linear transformations of motor unit discharge rates and muscle force. Intramuscular (wire electrodes) and high-density surface EMG (13 x 5 electrode grid) were recorded from the abductor digiti minimi muscle of eight healthy men during 60 s contractions at 5%, 7.5% and 10% of the maximal force. Spike trains of a total of 222 motor units were identified from the EMG recordings with decomposition algorithms. Principal component analysis of the smoothed motor unit discharge rates indicated that one component (first common component, FCC) described 44.2 +/- 7.5% of the total variability of the smoothed discharge rates when computed over the entire contraction interval and 64.3 +/- 10.2% of the variability when computed over 5 s intervals. When the FCC was computed from four or more motor units per contraction, it correlated with the force produced by the muscle (62.7 +/- 10.1%) by a greater degree (P < 0.001) than the smoothed discharge rates of individual motor units (41.4 +/- 7.8%). The correlation between FCC and the force signal increased up to 71.8 +/- 13.1% when the duration and the shape of the smoothing window for discharge rates were similar to the average motor unit twitch force. Moreover, the coefficients of variation (CoV) for the force and for the FCC signal were correlated in all subjects (R(2) range = 0.14-0.56; P < 0.05) whereas the CoV for force was correlated to the interspike interval variability in only one subject (R(2) = 0.12; P < 0.05). Similar results were further obtained from measures on the tibialis anterior muscle of an additional eight subjects during contractions at forces up to 20% of the maximal force (e.g. FCC explained 59.8 +/- 11.0% of variability of the smoothed discharge rates). In conclusion, one signal captures most of the underlying variability of the low-frequency components of motor unit discharge rates and explains large part of the fluctuations in the motor output during isometric contractions.

Intra-day signal instabilities affect decoding performance in an intracortical neural interface system.

PubMed

Perge, János A; Homer, Mark L; Malik, Wasim Q; Cash, Sydney; Eskandar, Emad; Friehs, Gerhard; Donoghue, John P; Hochberg, Leigh R

2013-06-01

Motor neural interface systems (NIS) aim to convert neural signals into motor prosthetic or assistive device control, allowing people with paralysis to regain movement or control over their immediate environment. Effector or prosthetic control can degrade if the relationship between recorded neural signals and intended motor behavior changes. Therefore, characterizing both biological and technological sources of signal variability is important for a reliable NIS. To address the frequency and causes of neural signal variability in a spike-based NIS, we analyzed within-day fluctuations in spiking activity and action potential amplitude recorded with silicon microelectrode arrays implanted in the motor cortex of three people with tetraplegia (BrainGate pilot clinical trial, IDE). 84% of the recorded units showed a statistically significant change in apparent firing rate (3.8 ± 8.71 Hz or 49% of the mean rate) across several-minute epochs of tasks performed on a single session, and 74% of the units showed a significant change in spike amplitude (3.7 ± 6.5 µV or 5.5% of mean spike amplitude). 40% of the recording sessions showed a significant correlation in the occurrence of amplitude changes across electrodes, suggesting array micro-movement. Despite the relatively frequent amplitude changes, only 15% of the observed within-day rate changes originated from recording artifacts such as spike amplitude change or electrical noise, while 85% of the rate changes most likely emerged from physiological mechanisms. Computer simulations confirmed that systematic rate changes of individual neurons could produce a directional 'bias' in the decoded neural cursor movements. Instability in apparent neuronal spike rates indeed yielded a directional bias in 56% of all performance assessments in participant cursor control (n = 2 participants, 108 and 20 assessments over two years), resulting in suboptimal performance in these sessions. We anticipate that signal acquisition and decoding methods that can adapt to the reported instabilities will further improve the performance of intracortically-based NISs.

Electrohydraulic linear actuator with two stepping motors controlled by overshoot-free algorithm

NASA Astrophysics Data System (ADS)

Milecki, Andrzej; Ortmann, Jarosław

2017-11-01

The paper describes electrohydraulic spool valves with stepping motors used as electromechanical transducers. A new concept of a proportional valve in which two stepping motors are working differentially is introduced. Such valve changes the fluid flow proportionally to the sum or difference of the motors' steps numbers. The valve design and principle of its operation is described. Theoretical equations and simulation models are proposed for all elements of the drive, i.e., the stepping motor units, hydraulic valve and cylinder. The main features of the valve and drive operation are described; some specific problem areas covering the nature of stepping motors and their differential work in the valve are also considered. The whole servo drive non-linear model is proposed and used further for simulation investigations. The initial simulation investigations of the drive with a new valve have shown that there is a significant overshoot in the drive step response, which is not allowed in positioning process. Therefore additional effort is spent to reduce the overshoot and in consequence reduce the settling time. A special predictive algorithm is proposed to this end. Then the proposed control method is tested and further improved in simulations. Further on, the model is implemented in reality and the whole servo drive system is tested. The investigation results presented in this paper, are showing an overshoot-free positioning process which enables high positioning accuracy.

Innervation zones of fasciculating motor units: observations by a linear electrode array.

PubMed

Jahanmiri-Nezhad, Faezeh; Barkhaus, Paul E; Rymer, William Z; Zhou, Ping

2015-01-01

This study examines the innervation zone (IZ) in the biceps brachii muscle in healthy subjects and those with amyotrophic lateral sclerosis (ALS) using a 20-channel linear electromyogram (EMG) electrode array. Raster plots of individual waveform potentials were studied to estimate the motor unit IZ. While this work mainly focused on fasciculation potentials (FPs), a limited number of motor unit potentials (MUPs) from voluntary activity of 12 healthy and seven ALS subjects were also examined. Abnormal propagation of MUPs and scattered IZs were observed in fasciculating units, compared with voluntarily activated MUPs in healthy and ALS subjects. These findings can be related to muscle fiber reinnervation following motor neuron degeneration in ALS and the different origin sites of FPs compared with voluntary MUPs.

Clustering of motor and nonmotor traits in leucine-rich repeat kinase 2 G2019S Parkinson's disease nonparkinsonian relatives: A multicenter family study.

PubMed

Mestre, Tiago A; Pont-Sunyer, Claustre; Kausar, Farah; Visanji, Naomi P; Ghate, Taneera; Connolly, Barbara S; Gasca-Salas, Carmen; Kern, Drew S; Jain, Jennifer; Slow, Elizabeth J; Faust-Socher, Achinoam; Kasten, Meike; Wadia, Pettarusp M; Zadikoff, Cindy; Kumar, Prakash; de Bie, Ronald M; Thomsen, Teri; Lang, Anthony E; Schüle, Birgitt; Klein, Christine; Tolosa, Eduardo; Marras, Connie

2018-04-17

The objective of this study was to determine phenotypic features that differentiate nonparkinsonian first-degree relatives of PD leucine-rich repeat kinase 2 (LRRK2) G2019S multiplex families, regardless of carrier status, from healthy controls because nonparkinsonian individuals in multiplex families seem to share a propensity to present neurological features. We included nonparkinsonian first-degree relatives of LRRK2 G2019S familial PD cases and unrelated healthy controls participating in established multiplex family LRRK2 cohorts. Study participants underwent neurologic assessment including cognitive screening, olfaction testing, and questionnaires for daytime sleepiness, depression, and anxiety. We used a multiple logistic regression model with backward variable selection, validated with bootstrap resampling, to establish the best combination of motor and nonmotor features that differentiates nonparkinsonian first-degree relatives of LRRK2 G2019S familial PD cases from unrelated healthy controls. We included 142 nonparkinsonian family members and 172 unrelated healthy controls. The combination of past or current symptoms of anxiety (adjusted odds ratio, 4.16; 95% confidence interval, 2.01-8.63), less daytime sleepiness (adjusted odds ratio [1 unit], 0.90; 95% confidence interval, 0.83-0.97], and worse motor UPDRS score (adjusted odds ratio [1 unit], 1.4; 95% confidence interval, 1.20-1.67) distinguished nonparkinsonian family members, regardless of LRRK2 G2019S mutation status, from unrelated healthy controls. The model accuracy was good (area under the curve = 79.3%). A set of motor and nonmotor features distinguishes first-degree relatives of LRRK2 G2019S probands, regardless of mutation status, from unrelated healthy controls. Environmental or non-LRRK2 genetic factors in LRRK2-associated PD may influence penetrance of the LRRK2 G2019S mutation. The relationship of these features to actual PD risk requires longitudinal observation of LRRK2 familial PD cohorts. © 2018 International Parkinson and Movement Disorder Society. © 2018 International Parkinson and Movement Disorder Society.

Characterization of a Robotic Manipulator for Dynamic Wind Tunnel Applications

DTIC Science & Technology

2015-03-26

further enhancements would need to be performed individually for each joint. This research effort focused on the improvement of the MTA wrist roll ...Measurement Unit ( IMU ), was used to validate the Euler angle output calculated by the MTA Computer using forward kinematics. Additionally, fast-response...61 3.7 Modeling the Wrist Roll Motor and Controller . . . . . . . . . . . . . . . . . . . . . 64 3.8 Proportional Control for Improved Performance

Fluidic emergency roll control system. [for emergency aircraft control following failure of primary roll control system

NASA Technical Reports Server (NTRS)

Haefner, K. B.; Honda, T. S.

1973-01-01

A fluidic emergency roll control system for aircraft stabilization in the event of primary flight control failure was evaluated. The fluidic roll control units were designed to provide roll torque proportional to an electrical command as operated by two diametrically opposed thrust nozzles located in the wing tips. The control package consists of a solid propellant gas generator, two diametrically opposed vortex valve modulated thrust nozzles, and an electromagnetic torque motor. The procedures for the design, development, and performance testing of the system are described.

Development of closed-loop neural interface technology in a rat model: combining motor cortex operant conditioning with visual cortex microstimulation.

PubMed

Marzullo, Timothy Charles; Lehmkuhle, Mark J; Gage, Gregory J; Kipke, Daryl R

2010-04-01

Closed-loop neural interface technology that combines neural ensemble decoding with simultaneous electrical microstimulation feedback is hypothesized to improve deep brain stimulation techniques, neuromotor prosthetic applications, and epilepsy treatment. Here we describe our iterative results in a rat model of a sensory and motor neurophysiological feedback control system. Three rats were chronically implanted with microelectrode arrays in both the motor and visual cortices. The rats were subsequently trained over a period of weeks to modulate their motor cortex ensemble unit activity upon delivery of intra-cortical microstimulation (ICMS) of the visual cortex in order to receive a food reward. Rats were given continuous feedback via visual cortex ICMS during the response periods that was representative of the motor cortex ensemble dynamics. Analysis revealed that the feedback provided the animals with indicators of the behavioral trials. At the hardware level, this preparation provides a tractable test model for improving the technology of closed-loop neural devices.

Effectiveness of mirror therapy on lower extremity motor recovery, balance and mobility in patients with acute stroke: A randomized sham-controlled pilot trial.

PubMed

Mohan, Uthra; Babu, S Karthik; Kumar, K Vijay; Suresh, B V; Misri, Z K; Chakrapani, M

2013-10-01

To evaluate the effectiveness of mirror therapy on lower extremity motor recovery, balance and mobility in patients with acute stroke. A randomized, sham-controlled, assessor blinded, pilot trial. Inpatient stroke rehabilitation unit. First time onset of stroke with mean post-stroke duration of 6.41 days, able to respond to verbal instructions, and Brunnstrom recovery stage 2 and above were enrolled. Mirror therapy group performed 30 minutes of functional synergy movements of non-paretic lower extremity, whereas control group underwent sham therapy with similar duration. In addition, both groups were administered with conventional stroke rehabilitation regime. Altogether 90 minutes therapy session per day, six days a week, for two weeks duration was administered to both groups. Lower extremity motor subscale of Fugl Meyer Assessment (FMA), Brunnel Balance Assessment (BBA) and Functional Ambulation Categories (FAC). Amongst the 22 patients included, equal number of patients participated in mirror group (N = 11) and control group (N = 11). Baseline variables were similar in both groups, except for Brunnstrom recovery stage. There was no statistical difference between groups, except for FAC. (FMA: P = 0.894; BBA: P = 0.358; FAC: P = 0.02). Significance was set at P < 0.05. Administration of mirror therapy early after stroke is not superior to conventional treatment in improving lower limb motor recovery and balance, except for improvement in mobility.

7. UNIT 4, VIEW TO SOUTHEAST, SHOWING GATE MOTOR ASSEMBLY ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. UNIT 4, VIEW TO SOUTHEAST, SHOWING GATE MOTOR ASSEMBLY (CENTER), TURBINE (LEFT FOREGROUND), AND GENERATOR (BACKGROUND) - Washington Water Power Company Monroe Street Plant, Units 4 & 5, South Bank Spokane River, below Monroe Street Bridge, Spokane, Spokane County, WA

6. UNIT 5, VIEW TO SOUTHWEST, SHOWING GATE MOTOR ASSEMBLY ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. UNIT 5, VIEW TO SOUTHWEST, SHOWING GATE MOTOR ASSEMBLY (CENTER), TURBINE (RIGHT FOREGROUND), AND GENERATOR (BACKGROUND) - Washington Water Power Company Monroe Street Plant, Units 4 & 5, South Bank Spokane River, below Monroe Street Bridge, Spokane, Spokane County, WA

Three speech sounds, one motor action: evidence for speech-motor disparity from English flap production.

PubMed

Derrick, Donald; Stavness, Ian; Gick, Bryan

2015-03-01

The assumption that units of speech production bear a one-to-one relationship to speech motor actions pervades otherwise widely varying theories of speech motor behavior. This speech production and simulation study demonstrates that commonly occurring flap sequences may violate this assumption. In the word "Saturday," a sequence of three sounds may be produced using a single, cyclic motor action. Under this view, the initial upward tongue tip motion, starting with the first vowel and moving to contact the hard palate on the way to a retroflex position, is under active muscular control, while the downward movement of the tongue tip, including the second contact with the hard palate, results from gravity and elasticity during tongue muscle relaxation. This sequence is reproduced using a three-dimensional computer simulation of human vocal tract biomechanics and differs greatly from other observed sequences for the same word, which employ multiple targeted speech motor actions. This outcome suggests that a goal of a speaker is to produce an entire sequence in a biomechanically efficient way at the expense of maintaining parity within the individual parts of the sequence.

Motor facilitation during real-time movement imitation in Parkinson's disease: a virtual reality study.

PubMed

Robles-García, Verónica; Arias, Pablo; Sanmartín, Gabriel; Espinosa, Nelson; Flores, Julian; Grieve, Kenneth L; Cudeiro, Javier

2013-12-01

Impaired temporal stability and poor motor unit recruitment are key impairments in Parkinsonian motor control during a whole spectrum of rhythmic movements, from simple finger tapping to gait. Therapies based on imitation can be designed for patients with motor impairments and virtual-reality (VR) offers a new perspective. Motor actions are known to depend upon the dopaminergic system, whose involvement in imitation is unknown. We sought to understand this role and the underlying possibilities for motor rehabilitation, by observing the execution of different motor-patterns during imitation in a VR environment in subjects with and without dopaminergic deficits. 10 OFF-dose idiopathic Parkinson's Disease patients (PD), 9 age-matched and 9 young-subjects participated. Subjects performed finger-tapping at their "comfort" and "slow-comfort" rates, while immersed in VR presenting their "avatar" in 1st person perspective. Imitation was evaluated by asking subjects to replicate finger-tapping patterns different to their natural one. The finger-pattern presented matched their comfort and comfort-slow rates, but without a pause on the table (continuously moving). Patients were able to adapt their finger-tapping correctly, showing that in comparison with the control groups, the dopaminergic deficiency of PD did not impair imitation. During imitation the magnitude of EMG increased and the temporal variability of movement decreased. PD-patients have unaltered ability to imitate instructed motor-patterns, suggesting that a fully-functional dopaminergic system is not essential for such imitation. It should be further investigated if imitation training over a period of time induces positive off-line motor adaptations with transfer to non-imitation tasks. Copyright © 2013 Elsevier Ltd. All rights reserved.

Firing patterns of spontaneously active motor units in spinal cord-injured subjects

PubMed Central

Zijdewind, Inge; Thomas, Christine K

2012-01-01

Involuntary motor unit activity at low rates is common in hand muscles paralysed by spinal cord injury. Our aim was to describe these patterns of motor unit behaviour in relation to motoneurone and motor unit properties. Intramuscular electromyographic activity (EMG), surface EMG and force were recorded for 30 min from thenar muscles of nine men with chronic cervical SCI. Motor units fired for sustained periods (>10 min) at regular (coefficient of variation ≤ 0.15, CV, n = 19 units) or irregular intervals (CV > 0.15, n = 14). Regularly firing units started and stopped firing independently suggesting that intrinsic motoneurone properties were important for recruitment and derecruitment. Recruitment (3.6 Hz, SD 1.2), maximal (10.2 Hz, SD 2.3, range: 7.5–15.4 Hz) and derecruitment frequencies were low (3.3 Hz, SD 1.6), as were firing rate increases after recruitment (∼20 intervals in 3 s). Once active, firing often covaried, promoting the idea that units received common inputs. Half of the regularly firing units showed a very slow decline (>40 s) in discharge before derecruitment and had interspike intervals longer than their estimated afterhyperpolarisation potential (AHP) duration (estimated by death rate and breakpoint analyses). The other units were derecruited more abruptly and had shorter estimated AHP durations. Overall, regularly firing units had longer estimated AHP durations and were weaker than irregularly firing units, suggesting they were lower threshold units. Sustained firing of units at regular rates may reflect activation of persistent inward currents, visible here in the absence of voluntary drive, whereas irregularly firing units may only respond to synaptic noise. PMID:22310313

Dynamic parameter identification of robot arms with servo-controlled electrical motors

NASA Astrophysics Data System (ADS)

Jiang, Zhao-Hui; Senda, Hiroshi

2005-12-01

This paper addresses the issue of dynamic parameter identification of the robot manipulator with servo-controlled electrical motors. An assumption is made that all kinematical parameters, such as link lengths, are known, and only dynamic parameters containing mass, moment of inertia, and their functions need to be identified. First, we derive dynamics of the robot arm with a linear form of the unknown dynamic parameters by taking dynamic characteristics of the motor and servo unit into consideration. Then, we implement the parameter identification approach to identify the unknown parameters with respect to individual link separately. A pseudo-inverse matrix is used for formulation of the parameter identification. The optimal solution is guaranteed in a sense of least-squares of the mean errors. A Direct Drive (DD) SCARA type industrial robot arm AdeptOne is used as an application example of the parameter identification. Simulations and experiments for both open loop and close loop controls are carried out. Comparison of the results confirms the correctness and usefulness of the parameter identification and the derived dynamic model.

Detail, unit 4, 1,850 horsepower (hp) synchronous pump motor manufactured ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail, unit 4, 1,850 horsepower (hp) synchronous pump motor manufactured by The Electric Products Company, Cleveland , Ohio. Pump units 1, 2, and 3 are identical to this unit. View to the west - Wellton-Mohawk Irrigation System, Pumping Plant No. 3, South of Interstate 8, Wellton, Yuma County, AZ

Modeling Molecular Machinery

ERIC Educational Resources Information Center

Hunter, Christine

2015-01-01

Imagine a microscopic world filled with tiny motors, ratchets, switches, and pumps controlled by complex signaling and feedback systems. Now imagine that these parts can assemble themselves. This is the world presented to students in the protein structure unit of a genetic engineering course. Students learn how protein folding gives rise to the…

Syllabus in Trade Electricity-Electronics. Section II. Trade Electricity.

ERIC Educational Resources Information Center

New York State Education Dept., Albany. Bureau of Occupational Education Curriculum Development.

This second section of a three-part syllabus for a flexible curriculum in trade electricity-electronics contains four semi-independent units: (1) Advanced Electricity, (2) Residential and Commercial Wiring, (3) Industrial Electricity, and (4) Motor Controls. Introductory sections describe development of the curriculum, outline the total trade…

Anatomic and physiological characteristics of the ferret lateral rectus muscle and abducens nucleus.

PubMed

Bishop, Keith N; McClung, J Ross; Goldberg, Stephen J; Shall, Mary S

2007-11-01

The ferret has become a popular model for physiological and neurodevelopmental research in the visual system. We believed it important, therefore, to study extraocular whole muscle as well as single motor unit physiology in the ferret. Using extracellular stimulation, 62 individual motor units in the ferret abducens nucleus were evaluated for their contractile characteristics. Of these motor units, 56 innervated the lateral rectus (LR) muscle alone, while 6 were split between the LR and retractor bulbi (RB) muscle slips. In addition to individual motor units, the whole LR muscle was evaluated for twitch, tetanic peak force, and fatigue. The abducens nucleus motor units showed a twitch contraction time of 15.4 ms, a mean twitch tension of 30.2 mg, and an average fusion frequency of 154 Hz. Single-unit fatigue index averaged 0.634. Whole muscle twitch contraction time was 16.7 ms with a mean twitch tension of 3.32 g. The average fatigue index of whole muscle was 0.408. The abducens nucleus was examined with horseradish peroxidase conjugated with the subunit B of cholera toxin histochemistry and found to contain an average of 183 motoneurons. Samples of LR were found to contain an average of 4,687 fibers, indicating an LR innervation ratio of 25.6:1. Compared with cat and squirrel monkeys, the ferret LR motor units contract more slowly yet more powerfully. The functional visual requirements of the ferret may explain these fundamental differences.

76 FR 10396 - New United Motor Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-24

... Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation and Toyota Motor Corporation, Including On- Site Leased Workers From Corestaff, ABM Janitorial, Toyota Engineering and Manufacturing North... Motor Manufacturing, Inc., formerly a joint venture of General Motors Corporation and Toyota Motor...

Discharge properties of abductor hallucis before, during, and after an isometric fatigue task.

PubMed

Kelly, Luke A; Racinais, Sebastien; Cresswell, Andrew G

2013-08-01

Abductor hallucis is the largest muscle in the arch of the human foot and comprises few motor units relative to its physiological cross-sectional area. It has been described as a postural muscle, aiding in the stabilization of the longitudinal arch during stance and gait. The purpose of this study was to describe the discharge properties of abductor hallucis motor units during ramp and hold isometric contractions, as well as its discharge characteristics during fatigue. Intramuscular electromyographic recordings from abductor hallucis were made in 5 subjects; from those recordings, 42 single motor units were decomposed. Data were recorded during isometric ramp contractions at 60% maximum voluntary contraction (MVC), performed before and after a submaximal isometric contraction to failure (mean force 41.3 ± 15.3% MVC, mean duration 233 ± 116 s). Motor unit recruitment thresholds ranged from 10.3 to 54.2% MVC. No significant difference was observed between recruitment and derecruitment thresholds or their respective discharge rates for both the initial and postfatigue ramp contractions (all P > 0.25). Recruitment threshold was positively correlated with recruitment discharge rate (r = 0.47, P < 0.03). All motor units attained similar peak discharge rates (14.0 ± 0.25 pulses/s) and were not correlated with recruitment threshold. Thirteen motor units could be followed during the isometric fatigue task, with a decline in discharge rate and increase in discharge rate variability occurring in the final 25% of the task (both P < 0.05). We have shown that abductor hallucis motor units discharge relatively slowly and are considerably resistant to fatigue. These characteristics may be effective for generating and sustaining the substantial level of force that is required to stabilize the longitudinal arch during weight bearing.

Discharge characteristics of biceps brachii motor units at recruitment when older adults sustained an isometric contraction.

PubMed

Pascoe, Michael A; Holmes, Matthew R; Enoka, Roger M

2011-02-01

The purpose of this study was to compare the discharge characteristics of motor units recruited during an isometric contraction that was sustained with the elbow flexor muscles by older adults at target forces that were less than the recruitment threshold force of each isolated motor unit. The discharge times of 27 single motor units were recorded from the biceps brachii in 11 old adults (78.8 ± 5.9 yr). The target force was set at either a relatively small (6.6 ± 3.7% maximum) or large (11.4 ± 4.5% maximum) difference below the recruitment threshold force and the contraction was sustained until the motor unit was recruited and discharged action potentials for about 60 s. The time to recruitment was longer for the large target-force difference (P = 0.001). At recruitment, the motor units discharged repetitively for both target-force differences, which contrasts with data from young adults when motor units discharged intermittently at recruitment for the large difference between recruitment threshold force and target force. The coefficient of variation (CV) for the first five interspike intervals (ISIs) increased from the small (18.7 ± 7.9) to large difference (35.0 ± 10.2%, P = 0.008) for the young adults, but did not differ for the two target force differences for the old adults (26.3 ± 14.7 to 24.0 ± 13.1%, P = 0.610). When analyzed across the discharge duration, the average CV for the ISI decreased similarly for the two target-force differences (P = 0.618) in old adults. These findings contrast with those of young adults and indicate that the integration of synaptic input during sustained contractions differs between young and old adults.

Recruitment of single human low-threshold motor units with increasing loads at different muscle lengths.

PubMed

McNulty, P A; Cresswell, A G

2004-06-01

We investigated the recruitment behaviour of low threshold motor units in flexor digitorum superficialis by altering two biomechanical constraints: the load against which the muscle worked and the initial muscle length. The load was increased using isotonic (low load), loaded dynamic (intermediate load) and isometric (high load) contractions in two studies. The initial muscle position reflected resting muscle length in series A, and a longer length with digit III fully extended in series B. Intramuscular EMG was recorded from 48 single motor units in 10 experiments on five healthy subjects, 21 units in series A and 27 in series B, while subjects performed ramp up, hold and ramp down contractions. Increasing the load on the muscle decreased the force, displacement and firing rate of single motor units at recruitment at shorter muscle lengths (P<0.001, dependent t-test). At longer muscle lengths this recruitment pattern was observed between loaded dynamic and isotonic contractions, but not between isometric and loaded dynamic contractions. Thus, the recruitment properties of single motor units in human flexor digitorum superficialis are sensitive to changes in both imposed external loads and the initial length of the muscle.

Preceding muscle activity influences motor unit discharge and rate of torque development during ballistic contractions in humans

PubMed Central

Van Cutsem, Michaël; Duchateau, Jacques

2005-01-01

To investigate the effect of initial conditions on the modulation of motor unit discharge during fast voluntary contractions, we compared ballistic isometric contractions of the ankle dorsiflexor muscles that were produced from either a resting state or superimposed on a sustained contraction. The torque of the dorsiflexors and the surface and intramuscular EMGs from the tibialis anterior were recorded. The results showed that the performance of a ballistic contraction from a sustained contraction (∼25% maximal voluntary contraction (MVC)) had a negative effect on the maximal rate of torque development. Although the electromechanical delay was shortened, the EMG activity during the ballistic contraction was less synchronized. These observations were associated with a significant decline in the average discharge rate of single motor units (89.8 ± 3.8 versus 115 ± 5.8 Hz) and in the percentage of units (6.2 versus 15.5% of the whole sample) that exhibited double discharges at brief intervals (= 5 ms). High-threshold units that were not recruited during the sustained contraction displayed the same activation pattern, which indicates that the mechanisms responsible for the decline in discharge rate were not restricted to previously activated units, but appear to influence the entire motor unit pool. When a premotor silent period (SP) was observed at the transition from the sustained muscular activity to the ballistic contraction (19% of the trials), these adjustments in motor unit activity were not present, and the ballistic contractions were similar to those performed from a resting state. Together, these results indicate that initial conditions can influence the capacity for motor unit discharge rate and hence the performance of a fast voluntary contraction. PMID:15539402

Motor unit firing and its relation to tremor in the tonic vibration reflex of the decerebrate cat.

PubMed

Clark, F J; Matthews, P B; Muir, R B

1981-01-01

1. The discharge of single motor units has been recorded from the soleus muscle of the decerebrate cat during the tonic vibration reflex elicited isometrically, to further understanding of the tremor that is seen in the reflex contraction. The reflex was elicited by pulses of vibration of 50 micrometers amplitude at 150 Hz, and up to four units were studied concurrently. 2. Individual units fired rather regularly and at a low frequency (range 4-14 Hz). The rate of firing of any unit normally fell within the frequency band of the tremor recorded at the same time. On comparing different preparations a higher frequency of tremor was associated with a higher frequency of motor firing. 3. The responses of pairs of motor units recorded concurrently during repeated production of the reflex were compared by cross-correlation analysis; over 1000 spikes from each train were normally used for this. The major of the cross-correlograms were flat with no overt sign of any synchronization between the units other than that due to the vibration. 4. Clear indications of correlated motor unit firing could be produced deliberately by modulating the amplitude of vibration at a frequency comparable to that of the normal tremor and thereby introducing a rhythmic component into the tonic vibration reflex. 5. About 20% of the cross-correlograms obtained during normal tremor showed varying amounts of an irregular 'waviness' suggesting a possible correlation between the times of firing of a pair of units. But such waves never developed steadily throughout the period of analysis, in contrast to the comparable waves produced on modulating the vibration. Similar waves were seen on cross-correlating a motor unit with an electronic oscillator, confirming that their occurrence does not necessarily demonstrate the existence of active neural interactions. 6. It is concluded that there is no strong and widespread neural synchronizing mechanism active during the tonic vibration reflex, although the possibility of some weak neural interactions has not been excluded. The findings favour the idea that the tremor in this preparation is simply the inevitable result of motor units discharging asynchronously, but at closely similar subtetanic frequencies.

Determination of the motor unit behavior of lumbar erector spinae muscles through surface EMG decomposition technology in healthy female subjects.

PubMed

Silva, Mariana Felipe; Dias, Josilainne Marcelino; Pereira, Ligia Maxwell; Mazuquin, Bruno Fles; Lindley, Steven; Richards, Jim; Cardoso, Jefferson Rosa

2017-01-01

The aims of this study were to determine the motor unit behavior of the erector spinae muscles and to assess whether differences exist between the dominant/nondominant sides of the back muscles. Nine healthy women, aged 21.7 years (SD = 0.7), performed a back extension test. Surface electromyographic decomposition data were collected from both sides of the erector spinae and decomposed into individual motor unit action potential trains. The mean firing rate for each motor unit was calculated, and a regression analysis was performed against the corresponding recruitment thresholds. The mean firing rate ranged from 15.9 to 23.9 pps and 15.8 to 20.6 pps on the dominant and nondominant sides, respectively. However, the early motor unit potentials of the nondominant lumbar erector spinae muscles were recruited at a lower firing rate. This technique may further our understanding of individuals with back pain and other underlying neuromuscular diseases. Muscle Nerve 55: 28-34, 2017. © 2016 Wiley Periodicals, Inc.

Deciphering the contribution of intrinsic and synaptic currents to the effects of transient synaptic inputs on human motor unit discharge

PubMed Central

Powers, Randall K.; Türker, Kemal S.

2010-01-01

The amplitude and time course of synaptic potentials in human motoneurons can be estimated in tonically discharging motor units by measuring stimulus-evoked changes in the rate and probability of motor unit action potentials. However, in spite of the fact that some of these techniques have been used for over thirty years, there is still no consensus on the best way to estimate the characteristics of synaptic potentials or on the accuracy of these estimates. In this review, we compare different techniques for estimating synaptic potentials from human motor unit discharge and also discuss relevant animal models in which estimated synaptic potentials can be compared to those directly measured from intracellular recordings. We also review the experimental evidence on how synaptic noise and intrinsic motoneuron properties influence their responses to synaptic inputs. Finally, we consider to what extent recordings of single motor unit discharge in humans can be used to distinguish the contribution of changes in synaptic inputs versus changes in intrinsic motoneuron properties to altered motoneuron responses following CNS injury. PMID:20427230

Size principle and information theory.

PubMed

Senn, W; Wyler, K; Clamann, H P; Kleinle, J; Lüscher, H R; Müller, L

1997-01-01

The motor units of a skeletal muscle may be recruited according to different strategies. From all possible recruitment strategies nature selected the simplest one: in most actions of vertebrate skeletal muscles the recruitment of its motor units is by increasing size. This so-called size principle permits a high precision in muscle force generation since small muscle forces are produced exclusively by small motor units. Larger motor units are activated only if the total muscle force has already reached certain critical levels. We show that this recruitment by size is not only optimal in precision but also optimal in an information theoretical sense. We consider the motoneuron pool as an encoder generating a parallel binary code from a common input to that pool. The generated motoneuron code is sent down through the motoneuron axons to the muscle. We establish that an optimization of this motoneuron code with respect to its information content is equivalent to the recruitment of motor units by size. Moreover, maximal information content of the motoneuron code is equivalent to a minimal expected error in muscle force generation.

Effect of age on changes in motor units functional connectivity.

PubMed

Arjunan, Sridhar P; Kumar, Dinesh

2015-08-01

With age, there is a change in functional connectivity of motor units in muscle. This leads to reduced muscle strength. This study has investigated the effect of age on the changes in the motor unit recruitment by measuring the mutual information between multiple channels of surface electromyogram (sEMG) of biceps brachii muscle. It is hypothesised that with ageing, there is a reduction in number of motor units, which can lead to an increase in the dependency of remaining motor units. This increase can be observed in the mutual information between the multiple channels of the muscle activity. Two channels of sEMG were recorded during the maximum level of isometric contraction. 28 healthy subjects (Young: age range 20-35years and Old: age range - 60-70years) participated in the experiments. The normalized mutual information (NMI), a measure of dependency factor, was computed for the sEMG recordings. Statistical analysis was performed to test the effect of age on NMI. The results show that the NMI among the older cohort was significantly higher when compared with the young adults.

Operational Loopwheel Suspension System for Mars Rover Demonstration Model

NASA Technical Reports Server (NTRS)

Trautwein, W.; Robinson, G. D.

1978-01-01

The loopwheel (or elastic loop) mobility concept, appears to be uniquely qualified to provide a high degree of mobility at low weight and stowage requirements for the next Mars mission now in the early planning stage. Traction elements compatible with sterilization and Mars surface environmental constraints were designed and are compatible with the rover mass, range and stowage requirements of JPL's point design Mars rover. In order to save cost, the loopwheel suspensions for the demonstration model were made of S-glass/epoxy instead of titanium, alloy specified for flight units. The load carrying fiberglass loop core is covered by a rubber tread on the outside. Reinforced rubber gear belts bonded along the inside edges provide positive engagement and transmission drive torques. A 12 Vdc drive motor with a 167:1 gear head is installed in the payload section of the hull. A chain drive transmits the motor power to the rear sprocket in the demonstration model, whereas future flight units would be directly driven by brushless hub motors within each sprocket and independent four-leg height control.

IUSThrust Vector Control (TVC) servo system

NASA Technical Reports Server (NTRS)

Conner, G. E.

1979-01-01

The IUS TVC SERVO SYSTEM which consists of four electrically redundant electromechanical actuators, four potentiometer assemblies, and two controllers to provide movable nozzle control on both IUS solid rocket motors is developed. An overview of the more severe IUS TVC servo system design requirements, the system and component designs, and test data acquired on a preliminary development unit is presented. Attention is focused on the unique methods of sensing movable nozzle position and providing for redundant position locks.

Innervation zones of fasciculating motor units: observations by a linear electrode array

PubMed Central

Jahanmiri-Nezhad, Faezeh; Barkhaus, Paul E.; Rymer, William Z.; Zhou, Ping

2015-01-01

This study examines the innervation zone (IZ) in the biceps brachii muscle in healthy subjects and those with amyotrophic lateral sclerosis (ALS) using a 20-channel linear electromyogram (EMG) electrode array. Raster plots of individual waveform potentials were studied to estimate the motor unit IZ. While this work mainly focused on fasciculation potentials (FPs), a limited number of motor unit potentials (MUPs) from voluntary activity of 12 healthy and seven ALS subjects were also examined. Abnormal propagation of MUPs and scattered IZs were observed in fasciculating units, compared with voluntarily activated MUPs in healthy and ALS subjects. These findings can be related to muscle fiber reinnervation following motor neuron degeneration in ALS and the different origin sites of FPs compared with voluntary MUPs. PMID:26029076

Load-dependent assembly of the bacterial flagellar motor.

PubMed

Tipping, Murray J; Delalez, Nicolas J; Lim, Ren; Berry, Richard M; Armitage, Judith P

2013-08-20

It is becoming clear that the bacterial flagellar motor output is important not only for bacterial locomotion but also for mediating the transition from liquid to surface living. The output of the flagellar motor changes with the mechanical load placed on it by the external environment: at a higher load, the motor runs more slowly and produces higher torque. Here we show that the number of torque-generating units bound to the flagellar motor also depends on the external mechanical load, with fewer stators at lower loads. Stalled motors contained at least as many stators as rotating motors at high load, indicating that rotation is unnecessary for stator binding. Mutant stators incapable of generating torque could not be detected around the motor. We speculate that a component of the bacterial flagellar motor senses external load and mediates the strength of stator binding to the rest of the motor. The transition between liquid living and surface living is important in the life cycles of many bacteria. In this paper, we describe how the flagellar motor, used by bacteria for locomotion through liquid media and across solid surfaces, is capable of adjusting the number of bound stator units to better suit the external load conditions. By stalling motors using external magnetic fields, we also show that rotation is not required for maintenance of stators around the motor; instead, torque production is the essential factor for motor stability. These new results, in addition to previous data, lead us to hypothesize that the motor stators function as mechanosensors as well as functioning as torque-generating units.

Research of subdivision driving technology for brushless DC motors in optical fiber positioning

NASA Astrophysics Data System (ADS)

Kan, Yi; Gu, Yonggang; Zhu, Ye; Zhai, Chao

2016-07-01

In fiber spectroscopic telescopes, optical fiber positioning units are used to position thousands of fibers on the focal plane quickly and precisely. Stepper motors are used in existing units, however, it has some inherent deficiencies, such as serious heating and low efficiency. In this work, the universally adopted subdivision driving technology for stepper motors is transplanted to brushless DC motors. It keeps the advantages of stepper motors such as high positioning accuracy and resolution, while overcomes the disadvantages mentioned above. Thus, this research mainly focuses on develop a novel subdivision driving technology for brushless DC motor. By the proving of experiments of online debug and subdivision speed and position, the proposed brushless DC motor subdivision technology can achieve the expected functions.

Development of a miniature motor-driven pulsatile LVAD driven by a fuzzy controller.

PubMed

Okamoto, Eiji; Makino, Tsutomu; Tanaka, Shuji; Yasuda, Takahiko; Akasaka, Yuta; Tani, Makiko; Inoue, Yusuke; Mitoh, Ayumu; Mitamura, Yoshinori

2007-01-01

We have been developing a small, lightweight motor-driven pulsatile left ventricular assist device (LVAD) with a ball screw. The motor-driven LVAD consists of a brushless DC motor and a ball screw. The attractive magnetic force between Nd-Fe-B magnets (with a diameter of 5 mm and a thickness of 1.5 mm) mounted in holes in a silicone rubber sheet (thickness 2 mm) and an iron plate adhered onto the a diaphragm of the blood pump can provide optimum active blood filling during the pump filling phase. The LVAD has a stroke volume of 55 ml and an overall volume of 285 ml; it weighs 360 g. The controller mainly consists of a fuzzy logic position and velocity controller to apply doctors' and engineers' knowledge to control the LVAD. Each unit of the controller consists of a functionally independent program module for easy improvement of the controller's performance. The LVAD was evaluated in in vitro experiments using a mock circulation. A maximum pump outflow of 5.1 l/min was obtained at a drive rate of 95 bpm against an afterload of 95 mmHg, and active filling using the attractive magnetic force provided a pump output of 3.6 l/min at a drive rate of 75 bpm under a preload of 0 mmHg. The operating efficiency of the LVAD was measured at between 8% and 10.5%. While the LVAD can provide adequate pump outflow for cardiac assistance, further upgrading of the software and improvement of the blood pump are required to improve pump performance and efficiency.

Changes in force, surface and motor unit EMG during post-exercise development of low frequency fatigue in vastus lateralis muscle.

PubMed

de Ruiter, C J; Elzinga, M J H; Verdijk, P W L; van Mechelen, W; de Haan, A

2005-08-01

We investigated the effects of low frequency fatigue (LFF) on post-exercise changes in rectified surface EMG (rsEMG) and single motor unit EMG (smuEMG) in vastus lateralis muscle (n = 9). On two experimental days the knee extensors were fatigued with a 60-s-isometric contraction (exercise) at 50% maximal force capacity (MFC). On the first day post-exercise (15 s, 3, 9, 15, 21 and 27 min) rsEMG and electrically-induced (surface stimulation) forces were investigated. SmuEMG was obtained on day two. During short ramp and hold (5 s) contractions at 50% MFC, motor unit discharges of the same units were followed over time. Post-exercise MFC and tetanic force (100 Hz stimulation) recovered to about 90% of the pre-exercise values, but recovery with 20 Hz stimulation was less complete: the 20-100 Hz force ratio (mean +/- SD) decreased from 0.65+/-0.06 (pre-exercise) to 0.56+/-0.04 at 27 min post-exercise (P<0.05), indicative of LFF. At 50% MFC, pre-exercise rsEMG (% pre-exercise maximum) and motor unit discharge rate were 51.1 +/- 12.7% and 14.1 +/- 3.7 (pulses per second; pps) respectively, 15 s post-exercise the respective values were 61.4 +/- 15.4% (P<0.05) and 13.2 +/- 5.6 pps (P>0.05). Thereafter, rsEMG (at 50% MFC) remained stable but motor unit discharge rate significantly increased to 17.7 +/- 3.9 pps 27 min post-exercise. The recruitment threshold decreased (P<0.05) from 27.7 +/- 6.6% MFC before exercise to 25.2 +/- 6.7% 27 min post-exercise. The increase in discharge rate was significantly greater than could be expected from the decrease in recruitment threshold. Thus, post-exercise LFF was compensated by increased motor unit discharge rates which could only partly be accounted for by the small decrease in motor unit recruitment threshold.

A Spaceflight Magnetic Bearing Equipped Optical Chopper with Six-Axis Active Control

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A.; Lee, Kenneth Y.; Schepis, Joseph P.

1998-01-01

This paper describes the development of an ETU (Engineering Test Unit) rotary optical chopper with magnetic bearings. An ETU is required to be both flight-like, nearly identical to a flight unit without the need for material certifications, and demonstrate structural and performance integrity. A prototype breadboard design previously demonstrated the feasibility of meeting flight performance requirements using magnetic bearings. The chopper mechanism is a critical component of the High Resolution Dynamics Limb Sounder (HIRDLS) which will be flown on EOS-CHEM (Earth Observing System-Chemistry). Particularly noteworthy are the science requirements which demand high precision positioning and minimal power consumption along with full redundancy of coils and sensors in a miniature, lightweight package. The magnetic bearings are unique in their pole design to minimize parasitic losses and utilize collocated optical sensing. The motor is of an unusual disk-type ironless stator design. The ETU design has evolved from the breadboard design. A number of improvements have been incorporated into the ETU design. Active thrust control has been added along with changes to improve sensor stability, motor efficiency, and touchdown and launch survivability. It was necessary to do all this while simultaneously reducing the mechanism volume. Flight-like electronics utilize a DSP (Digital Signal Processor) and contain all sensor electronics and drivers on a single five inch by nine inch circuit board. Performance test results are reported including magnetic bearing and motor rotational losses.

Instrumentation for motor-current signature analysis using synchronous sampling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castleberry, K.N.

1996-07-01

Personnel in the Instrumentation and Controls Division at Oak Ridge National Laboratory, in association with the United States Enrichment Corporation, the U.S. Navy, and various Department of Energy sponsors, have been involved in the development and application of motor-current signature analysis for several years. In that time, innovation in the field has resulted in major improvements in signal processing, analysis, and system performance and capabilities. Recent work has concentrated on industrial implementation of one of the most promising new techniques. This report describes the developed method and the instrumentation package that is being used to investigate and develop potential applications.

75 FR 28656 - New United Motor Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-21

... Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation, and Toyota Motor Corporation, Including On- Site Leased Workers From Corestaff, ABM Janitorial, and Toyota Engineering and Manufacturing... joint venture of General Motors Corporation and Toyota Motor Corporation, including on-site leased...

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Characterization of motor units in behaving adult mice shows a wide primary range

PubMed Central

Ritter, Laura K.; Tresch, Matthew C.; Heckman, C. J.; Manuel, Marin

2014-01-01

The mouse is essential for genetic studies of motor function in both normal and pathological states. Thus it is important to consider whether the structure of motor output from the mouse is in fact analogous to that recorded in other animals. There is a striking difference in the basic electrical properties of mouse motoneurons compared with those in rats, cats, and humans. The firing evoked by injected currents produces a unique frequency-current (F-I) function that emphasizes recruitment of motor units at their maximum force. These F-I functions, however, were measured in anesthetized preparations that lacked two key components of normal synaptic input: high levels of synaptic noise and neuromodulatory inputs. Recent studies suggest that the alterations in the F-I function due to these two components are essential for recreating firing behavior of motor units in human subjects. In this study we provide the first data on firing patterns of motor units in the awake mouse, focusing on steady output in quiet stance. The resulting firing patterns did not match the predictions from the mouse F-I behaviors but instead revealed rate modulation across a remarkably wide range (10–60 Hz). The low end of the firing range may be due to changes in the F-I relation induced by synaptic noise and neuromodulatory inputs. The high end of the range may indicate that, unlike other species, quiet standing in the mouse involves recruitment of relatively fast-twitch motor units. PMID:24805075

Characterization of motor units in behaving adult mice shows a wide primary range.

PubMed

Ritter, Laura K; Tresch, Matthew C; Heckman, C J; Manuel, Marin; Tysseling, Vicki M

2014-08-01

The mouse is essential for genetic studies of motor function in both normal and pathological states. Thus it is important to consider whether the structure of motor output from the mouse is in fact analogous to that recorded in other animals. There is a striking difference in the basic electrical properties of mouse motoneurons compared with those in rats, cats, and humans. The firing evoked by injected currents produces a unique frequency-current (F-I) function that emphasizes recruitment of motor units at their maximum force. These F-I functions, however, were measured in anesthetized preparations that lacked two key components of normal synaptic input: high levels of synaptic noise and neuromodulatory inputs. Recent studies suggest that the alterations in the F-I function due to these two components are essential for recreating firing behavior of motor units in human subjects. In this study we provide the first data on firing patterns of motor units in the awake mouse, focusing on steady output in quiet stance. The resulting firing patterns did not match the predictions from the mouse F-I behaviors but instead revealed rate modulation across a remarkably wide range (10-60 Hz). The low end of the firing range may be due to changes in the F-I relation induced by synaptic noise and neuromodulatory inputs. The high end of the range may indicate that, unlike other species, quiet standing in the mouse involves recruitment of relatively fast-twitch motor units. Copyright © 2014 the American Physiological Society.

Characteristic changes of motor unit activity in hip joint flexor muscles during voluntary isometric contraction during water immersion.

PubMed

Sugajima, Y; Mitarai, G; Koeda, M; Moritani, T

1996-06-01

The effect of whole body water immersion on the recruitment order of hip flexor motor units was investigated in 11 male subjects. Intramuscular spike potentials were recorded, with fine bipolar wire electrodes, from the iliopsoas, the sartorius, the rectus femoris and the tensor fasciae latae during voluntary isometric contraction while the subjects were standing erect with the hip on the test side flexed to 60 degrees and the knee flexed to 120 degrees . Data were analysed by measuring the recruitment threshold in slow ramp contraction and by a computer-aided amplitude-frequency histogram of the spike potentials during short sustained contraction. The motor units were classified as low-amplitude units if they delivered spike potentials of less than 0.5 mV and high-amplitude units if the spike potentials exceeded 0.5 mV. In the ramp experiments, exposure to water immersion gave rise to a sudden increase in the recruitment thresholds of the low-amplitude units in all muscles, while in the recruitment thresholds of the high-amplitude units, the alterations differed among the muscles. The thresholds in the rectus femoris and tensor fasciae latae increased in the same direction as those of the low-amplitude units, while those in the iliopsoas and sartorius decreased in the opposite direction. The amplitude-frequency histograms clearly indicated that these different alterations occurred in all subjects, without exception. We concluded that unloading induced by water immersion changed the recruitment order of motor units during isometric contraction in the iliopsoas and sartorius, facilitating the recruitment of their larger motor units.

Feedback control of a Darrieus wind turbine and optimization of the produced energy

NASA Astrophysics Data System (ADS)

Maurin, T.; Henry, B.; Devos, F.; de Saint Louvent, B.; Gosselin, J.

1984-03-01

A microprocessor-driven control system, applied to the feedback control of a Darrieus wind turbine is presented. The use of a dc machine as a generator to recover the energy and as a motor to start the engine, allows simplified power electronics. The architecture of the control unit is built to ensure four different functions: starting, optimization of the recoverable energy, regulation of the speed, and braking. An experimental study of the system in a wind tunnel allowed optimization of the coefficients of the proportional and integral (pi) control algorithm. The electrical energy recovery was found to be much more efficient using the feedback system than without the control unit. This system allows a better characterization of the wind turbine and a regulation adapted to the wind statistics observed in one given geographical location.

AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XIX, LEARNING ABOUT CRANKING MOTORS.

ERIC Educational Resources Information Center

Human Engineering Inst., Cleveland, OH.

THIS MODULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES OF CRANKING MOTORS USED ON DIESEL POWERED EQUIPMENT, TOPICS ARE (1) CRANKING MOTORS. (2) MOTOR PINCIPLES, (3) CRANKING MOTOR CIRCUITS, (4) TYPES OF CRANKING MOTOR DRIVES, AND (5) CRANKING MOTOR SOLENOID CIRCUITS. THE MODULE CONSISTS OF A…

Reduced firing rates of high threshold motor units in response to eccentric overload.

PubMed

Balshaw, Tom G; Pahar, Madhu; Chesham, Ross; Macgregor, Lewis J; Hunter, Angus M

2017-01-01

Acute responses of motor units were investigated during submaximal voluntary isometric tasks following eccentric overload (EO) and constant load (CL) knee extension resistance exercise. Ten healthy resistance-trained participants performed four experimental test sessions separated by 5 days over a 20 day period. Two sessions involved constant load and the other two used eccentric overload. EO and CL used both sessions for different target knee eccentric extension phases; one at 2 sec and the other at 4 sec. Maximal voluntary contractions (MVC) and isometric trapezoid efforts for 10 sec at 70% MVC were completed before and after each intervention and decomposed electromyography was used to measure motor unit firing rate. The firing rate of later recruited, high-threshold motor units declined following the 2-sec EO but was maintained following 2sec CL (P < 0.05), whereas MUFR for all motor units were maintained for both loading types following 4-sec extension phases. MVC and rate of force development where maintained following both EO and CL and 2 and 4 sec phases. This study demonstrates a slower firing rate of high-threshold motor units following fast eccentric overload while MVC was maintained. This suggests that there was a neuromuscular stimulus without cost to the force-generating capacity of the knee extensors. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Robust and accurate decoding of motoneuron behavior and prediction of the resulting force output.

PubMed

Thompson, Christopher K; Negro, Francesco; Johnson, Michael D; Holmes, Matthew R; McPherson, Laura Miller; Powers, Randall K; Farina, Dario; Heckman, Charles J

2018-05-03

The spinal alpha motoneuron is the only cell in the human CNS whose discharge can be routinely recorded in humans. We have reengineered motor unit collection and decomposition approaches, originally developed in humans, to measure the neural drive to muscle and estimate muscle force generation in the decerebrate cat model. Experimental, computational, and predictive approaches are used to demonstrate the validity of this approach across a wide range of modes to activate the motor pool. The utility of this approach is shown through the ability to track individual motor units across trials, allowing for better predictions of muscle force than the electromyography signal, and providing insights in to the stereotypical discharge characteristics in response to synaptic activation of the motor pool. This approach now allows for a direct link between the intracellular data of single motoneurons, the discharge properties of motoneuron populations, and muscle force generation in the same preparation. The discharge of a spinal alpha motoneuron and the resulting contraction of its muscle fibers represents the functional quantum of the motor system. Recent advances in the recording and decomposition of the electromyographic signal allows for the identification of several tens of concurrently active motor units. These detailed population data provide the potential to achieve deep insights into the synaptic organization of motor commands. Yet most of our understanding of the synaptic input to motoneurons is derived from intracellular recordings in animal preparations. Thus, it is necessary to extend the new electrode and decomposition methods to recording of motor unit populations in these same preparations. To achieve this goal, we use high-density electrode arrays and decomposition techniques, analogous to those developed for humans, to record and decompose the activity of tens of concurrently active motor units in a hindlimb muscle in the decerebrate cat. Our results showed that the decomposition method in this animal preparation was highly accurate, with conventional two-source validation providing rates of agreement equal to or superior to those found in humans. Multidimensional reconstruction of the motor unit action potential provides the ability to accurately track the same motor unit across multiple contractions. Additionally, correlational analyses demonstrate that the composite spike train provides better estimates of whole muscle force than conventional estimates obtained from the electromyographic signal. Lastly, stark differences are observed between the modes of activation, in particular tendon vibration produced quantal interspike intervals at integer multiples of the vibration period. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Neural Issues in the Control of Muscular Strength

ERIC Educational Resources Information Center

Kamen, Gary

2004-01-01

During the earliest stages of resistance exercise training, initial muscular strength gains occur too rapidly to be explained solely by muscle-based mechanisms. However, increases in surface-based EMG amplitude as well as motor unit discharge rate provide some insight to the existence of neural mechanisms in the earliest phases of resistance…

MONITORING AND MODELING METHODS FOR DEVELOPING AIR POLLUTION CONTROL STRATEGIES: A CASE STUDY IN THE NORTHWEST CZECH REPUBLIC

EPA Science Inventory

Scientists from the United States and the Czech Republic recently completed a study to investigate the ambient air quality impact of industrial and motor vehicle sources in Teplice. ir pollution measurements made from 1992 through 1993 provide data on ambient concentrations of su...

49 CFR Appendix B to Part 564 - Information To Be Submitted for Long Life Replaceable Light Sources of Limited Definition

Code of Federal Regulations, 2010 CFR

2010-10-01

... light sources used in motor vehicle headlighting systems. This part also serves as a repository for... standardized sealed beam units used in motor vehicle headlighting systems. § 564.2 Purposes. The purposes of... manufacturing specifications of standardized sealed beam headlamp units used on motor vehicles so that all...

Common drive unit

NASA Technical Reports Server (NTRS)

Ellis, R. C.; Fink, R. A.; Moore, E. A.

1987-01-01

The Common Drive Unit (CDU) is a high reliability rotary actuator with many versatile applications in mechanism designs. The CDU incorporates a set of redundant motor-brake assemblies driving a single output shaft through differential. Tachometers provide speed information in the AC version. Operation of both motors, as compared to the operation of one motor, will yield the same output torque with twice the output speed.

Proteostasis and Diseases of the Motor Unit.

PubMed

Rinaldi, Carlo; Mäger, Imre; Wood, Matthew J

2016-01-01

The accumulation in neurons of aberrant protein species, the pathological hallmark of many neurodegenerative diseases, results from a global impairment of key cellular processes governing protein synthesis/degradation and repair mechanisms, also known as the proteostasis network (PN). The growing number of connections between dysfunction of this intricate network of pathways and diseases of the motor unit, where both motor neurons and muscle are primarily affected, has provided momentum to investigate the muscle- and motor neuron-specific response to physiological and pathological stressors and to explore the therapeutic opportunities that manipulation of this process may offer. Furthermore, these diseases offer an unparalleled opportunity to deepen our understanding of the molecular mechanisms behind the intertissue communication and transfer of signals of proteostasis. The most compelling aspect of these investigations is their immediate potential for therapeutic impact: targeting muscle to stem degeneration of the motor unit would represent a dramatic paradigm therapeutic shift for treating these devastating diseases. Here we will review the current state of the art of the research on the alterations of the PN in diseases of the motor unit and its potential to result in effective treatments for these devastating neuromuscular disorders.

Unilateral versus bilateral robot-assisted rehabilitation on arm-trunk control and functions post stroke: a randomized controlled trial.

PubMed

Wu, Ching-Yi; Yang, Chieh-Ling; Chen, Ming-de; Lin, Keh-Chung; Wu, Li-Ling

2013-04-12

Although the effects of robot-assisted arm training after stroke are promising, the relative effects of unilateral (URT) vs. bilateral (BRT) robot-assisted arm training remain uncertain. This study compared the effects of URT vs. BRT on upper extremity (UE) control, trunk compensation, and function in patients with chronic stroke. This was a single-blinded, randomized controlled trial. The intervention was implemented at 4 hospitals. Fifty-three patients with stroke were randomly assigned to URT, BRT, or control treatment (CT). Each group received UE training for 90 to 105 min/day, 5 days/week, for 4 weeks. The kinematic variables for arm motor control and trunk compensation included normalized movement time, normalized movement units, and the arm-trunk contribution slope in unilateral and bilateral tasks. Motor function and daily function were measured by the Wolf Motor Function Test (WMFT), Motor Activity Log (MAL), and ABILHAND Questionnaire. The BRT and CT groups elicited significantly larger slope values (i.e., less trunk compensation) at the start of bilateral reaching than the URT group. URT led to significantly better effects on WMFT-Time than BRT. Differences in arm control kinematics and performance on the MAL and ABILHAND among the 3 groups were not significant. BRT and URT resulted in differential improvements in specific UE/trunk performance in patients with stroke. BRT elicited larger benefits than URT on reducing compensatory trunk movements at the beginning of reaching. In contrast, URT produced better improvements in UE temporal efficiency. These relative effects on movement kinematics, however, did not translate into differential benefits in daily functions. ClinicalTrials.gov: NCT00917605.

Randomized controlled trial of ethyl-eicosapentaenoic acid in Huntington disease: the TREND-HD study.

PubMed

2008-12-01

To determine whether ethyl-eicosapentaenoic acid (ethyl-EPA), an omega-3 fatty acid, improves the motor features of Huntington disease. Six-month multicenter, randomized, double-blind, placebo-controlled trial followed by a 6-month open-label phase without disclosing initial treatment assignments. Forty-one research sites in the United States and Canada. Three hundred sixteen adults with Huntington disease, enriched for a population with shorter trinucleotide (cytosine-adenine-guanine) repeat length expansions. Random assignment to placebo or ethyl-EPA, 1 g twice a day, followed by open-label treatment with ethyl-EPA. Six-month change in the Total Motor Score 4 component of the Unified Huntington's Disease Rating Scale analyzed for all research participants and those with shorter cytosine-adenine-guanine repeat length expansions (<45). At 6 months, the Total Motor Score 4 point change for patients receiving ethyl-EPA did not differ from that for those receiving placebo. No differences were found in measures of function, cognition, or global impression. Before public disclosure of the 6-month placebo-controlled results, 192 individuals completed the open-label phase. The Total Motor Score 4 change did not worsen for those who received active treatment for 12 continuous months compared with those who received active treatment for only 6 months (2.0-point worsening; P=.02). Ethyl-EPA was not beneficial in patients with Huntington disease during 6 months of placebo-controlled evaluation. Clinical Trial Registry clinicaltrials.gov Identifier: NCT00146211.

Core stability exercise is as effective as task-oriented motor training in improving motor proficiency in children with developmental coordination disorder: a randomized controlled pilot study.

PubMed

Au, Mei K; Chan, Wai M; Lee, Lin; Chen, Tracy Mk; Chau, Rosanna Mw; Pang, Marco Yc

2014-10-01

To compare the effectiveness of a core stability program with a task-oriented motor training program in improving motor proficiency in children with developmental coordination disorder (DCD). Randomized controlled pilot trial. Outpatient unit in a hospital. Twenty-two children diagnosed with DCD aged 6-9 years were randomly allocated to the core stability program or the task-oriented motor program. Both groups underwent their respective face-to-face training session once per week for eight consecutive weeks. They were also instructed to carry out home exercises on a daily basis during the intervention period. Short Form of the Bruininks-Oseretsky Test of Motor Proficiency (Second Edition) and Sensory Organization Test at pre- and post-intervention. Intention-to-treat analysis revealed no significant between-group difference in the change of motor proficiency standard score (P=0.717), and composite equilibrium score derived from the Sensory Organization Test (P=0.100). Further analysis showed significant improvement in motor proficiency in both the core stability (mean change (SD)=6.3(5.4); p=0.008) and task-oriented training groups (mean change(SD)=5.1(4.0); P=0.007). The composite equilibrium score was significantly increased in the task-oriented training group (mean change (SD)=6.0(5.5); P=0.009), but not in the core stability group (mean change(SD) =0.0(9.6); P=0.812). In the task-oriented training group, compliance with the home program was positively correlated with change in motor proficiency (ρ=0.680, P=0.030) and composite equilibrium score (ρ=0.638, P=0.047). The core stability exercise program is as effective as task-oriented training in improving motor proficiency among children with DCD. © The Author(s) 2014.

Motor Unit Number Estimate and Isometric Hand Grip Strength in Military Veterans with or Without Muscular Complaints: Reference Values for Longitudinal Follow-up.

PubMed

Li, Mian; Yao, Wenguo; Sundahl, Cynthia

2018-03-26

It remains unclear if Gulf War (GW) veterans have a higher risk of developing motor neuron disorder. We intended to establish baseline neurophysiological values, including thenar motor unit number estimate (MUNE) and isometric hand grip (IHG) strength, to compare future follow-ups of deployed GW veterans with or without muscular complaints. We evaluated 19 GW veterans with self-reported weakness, cramps, or excessive muscle fatigue (Ill-19) and compared them with 18 controls without such muscular complaints (C-18). We performed MUNE on hand thenar muscles using adapted multipoint stimulation method for Ill-19 and 15 controls (C-15). We measured IHG strength (maximum force, endurance, and fatigue level) on Ill-19 and C-18 with a hand dynamometer. We performed nerve conduction studies on all study participants to determine which subjects had mild carpal tunnel syndrome (CTS). We compared the MUNE and IHG strength measures between Ill group and controls and between those with CTS and those without CTS. We obtained thenar MUNE of Ill-19 (95% CI of mean: 143-215; mean age: 46 yr) and compared it with that of C-15 (95% CI of mean: 161-230; mean age: 45 yr), and 95% of CI of mean among IHG strength variables (maximum force: 324-381 Newton; endurance: 32-42 s; fatigue level: 24%-33%) compared with C-18 (maximum force: 349-408 Newton; endurance: 35-46 s; fatigue level: 21%-27%). There was no significant difference in either MUNE or IHG strength between Ill-19 group and controls. The MUNE and IHG maximum forces were significantly lower in those with CTS compared with those without CTS. As a surrogate of mild CTS, the median versus ulnar distal sensory latency on nerve conduction study was only weakly associated with MUNE, maximum force, and fatigue level, respectively. To our knowledge, no published study on MUNE reference values of military veteran population has been available. The quantifiable values of both thenar MUNE and IHG strength of military veterans serve as baselines for our longitudinal follow-up of motor neuron function of deployed troops. These reference values are also useful for other laboratories to study veterans' motor system with or without mild CTS.

Preferential motor unit loss in the SOD1G93A transgenic mouse model of amyotrophic lateral sclerosis

PubMed Central

Hegedus, J; Putman, C T; Tyreman, N; Gordon, T

2008-01-01

The present study investigated motor unit (MU) loss in a murine model of familial amyotrophic lateral sclerosis (ALS). The fast-twitch tibialis anterior (TA) and medial gastrocnemius (MG) muscles of transgenic SOD1G93A and SOD1WT mice were studied during the presymptomatic phase of disease progression at 60 days of age. Whole muscle maximum isometric twitch and tetanic forces were 80% lower (P < 0.01) in the TA muscles of SOD1G93A compared to SOD1WT mice. Enumeration of total MU numbers within TA muscles showed a 60% reduction (P < 0.01) within SOD1G93A mice (38 ± 7) compared with SOD1WT controls (95 ± 12); this was attributed to a lower proportion of the most forceful fast-fatigable (FF) MU in SOD1G93A mice, as seen by a significant (P < 0.01) leftward shift in the cumulative frequency histogram of single MU forces. Similar patterns of MU loss and corresponding decreases in isometric twitch force were observed in the MG. Immunocytochemical analyses of the entire cross-sectional area (CSA) of serial sections of TA muscles stained with anti-neural cell adhesion molecule (NCAM) and various monoclonal antibodies for myosin heavy chain (MHC) isoforms showed respective 65% (P < 0.01) and 28% (P < 0.05) decreases in the number of innervated IIB and IID/X muscle fibres in SOD1G93A, which paralleled the 60% decrease (P < 0.01) in the force generating capacity of individual fibres. The loss of fast MUs was partially compensated by activity-dependent fast-to-slower fibre type transitions, as determined by increases (P < 0.04) in the CSA and proportion of IIA fibres (from 4% to 14%) and IID/X fibres (from 31% to 39%), and decreases (P < 0.001) in the CSA and proportion of type IIB fibres (from 65% to 44%). We conclude that preferential loss of IIB fibres is incomplete at 60 days of age, and is consistent with a selective albeit gradual loss of FF MUs that is not fully compensated by sprouting of the remaining motoneurons that innervate type IIA or IID/X muscle fibres. Our findings indicate that disease progression in fast-twitch muscles of SOD1G93A mice involves parallel processes: (1) gradual selective motor axon die-back of the FF motor units that contain large type IIB muscle fibres, and of fatigue-intermediate motor units that innervate type IID/X muscle fibres, and (2) activity-dependent conversion of motor units to those innervated by smaller motor axons innervating type IIA fatigue-resistant muscle fibres. PMID:18467368

Two-motor direct drive control for elevation axis of telescope

NASA Astrophysics Data System (ADS)

Tang, T.; Tan, Y.; Ren, G.

2014-07-01

Two-motor application has become a very attractive filed in important field which high performance is permitted to achieve of position, speed, and acceleration. In the elevation axis of telescope control system, two-motor direct drive is proposed to enhance the high performance of tracking control system. Although there are several dominant strengths such as low size of motors and high torsional structural dynamics, the synchronization control of two motors is a very difficult and important. In this paper, a multi-loop control technique base master-slave current control is used to synchronize two motors, including current control loop, speed control loop and position control loop. First, the direct drive function of two motors is modeled. Compared of single motor direct control system, the resonance frequency of two motor control systems is same; while the anti-resonance frequency of two motors control system is 1.414 times than those of sing motor system. Because of rigid coupling for direct drive, the speed of two motor of the system is same, and the synchronization of torque for motors is critical. The current master-slave control technique is effective to synchronize the torque, which the current loop of the master motors is tracked the other slave motor. The speed feedback into the input of current loop of the master motors. The experiments test the performance of the two motors drive system. The random tracking error is 0.0119" for the line trajectory of 0.01°/s.

Solar Heating System installed at Belz Investment Company, Memphis, Tennessee

NASA Technical Reports Server (NTRS)

1981-01-01

A hot air solar system which utilizes flat plate air collectors is discussed. Collector areas for each of four buildings cover 780 sq ft, with storage capacity of 390 cu ft per building. The air system has a special air handling unit to move air through the collectors and into and out of the rock storage, with connection to the air duct distribution system. The heat of the motor is added to the heat delivered to the system. The solar system also includes four motorized special low leakage dampers and two gravity fabric dampers. The system is automatically controlled by a solid state controller with three thermistors: one located in the collectors, one in the rock box to plenum, one in the return air duct from the heated space. A three stage heating thermostat, located in the conditioned space, controls the operation.

Sleepiness/fatigue and distraction/inattention as factors for fatal versus nonfatal commercial motor vehicle driver injuries.

PubMed

Bunn, T L; Slavova, S; Struttmann, T W; Browning, S R

2005-09-01

A retrospective population-based case-control study was conducted to determine whether driver sleepiness/fatigue and inattention/distraction increase the likelihood that a commercial motor vehicle collision (CVC) will be fatal. Cases were identified as CVC drivers who died (fatal) and controls were drivers who survived (nonfatal) an injury collision using the Kentucky Collision Report Analysis for Safer Highways (CRASH) electronic database from 1998-2002. Cases and controls were matched on unit type and roadway type. Conditional logistic regression was performed. Driver sleepiness/fatigue, distraction/inattention, age of 51 years of age and older, and nonuse of safety belts increase the odds that a CVC will be fatal. Primary safety belt law enactment and enforcement for all states, commercial vehicle driver education addressing fatigue and distraction and other approaches including decreased hours-of-service, rest breaks and policy changes, etc. may decrease the probability that a CVC will be fatal.

History of the Army Ground Forces. Study Number 15. The Desert Training Center and C-AMA, (California - Arizona Area)

DTIC Science & Technology

1946-01-01

armored division* and one motorized division. General McNair spoke of armored and motorized units, but did not specify how many units or how long a...anything. They had to learn how to fight. He told officials of the Water Distgict that they would be given a week’s notice before water would be needed.. On...cover of darkness; desert navigation for all personnel; laying and removal of mine fields by all units; maintenance and evacuation of motor vehicles

Electromyographic cross-talk within a compartmentalized muscle of the cat.

PubMed Central

English, A W; Weeks, O I

1989-01-01

1. Experiments were conducted to test the extent to which the electromyographic (EMG) activity generated by the activation of single motor units is conducted from one neuromuscular compartment of the cat lateral gastrocnemius (LG) muscle into adjacent compartments. 2. Potentials produced by stimulation of forty-five single motor units were monitored from bipolar fine-wire EMG electrodes which had been implanted either into the centres of each of the four neuromuscular compartments of LG or into regions of the muscle known to lie on the border of contiguous compartments. 3. In all cases single unit potentials could be recorded from the electrodes in the centre of the compartments which clearly identified the compartment of residence of the muscle unit. Regardless of unit type, the amplitude of the potential recorded from electrodes in one compartment was always greater than that recorded from any other compartment. 4. Smaller potentials could be recorded from electrodes in the centre of compartments adjacent to the compartment of residence of the muscle unit. For those motor units where the amplitude of the EMG potentials recorded from the compartment of residence was large, the amplitude of such 'cross-talk' could be greater than the amplitude of potentials recorded from the compartment of residence of smaller motor units. 5. In the case of electrodes placed at compartment boundaries, no clear compartment selectivity of recording of motor unit potentials was evident. 6. These results indicate that great care must be taken in choosing sites of EMG electrode placement when performing kinesiological studies, especially when the amplitude of the EMG activity recorded is of consideration. PMID:2558175

Torque blending and wheel slip control in EVs with in-wheel motors

NASA Astrophysics Data System (ADS)

de Castro, Ricardo; Araújo, Rui E.; Tanelli, Mara; Savaresi, Sergio M.; Freitas, Diamantino

2012-01-01

Among the many opportunities offered by electric vehicles (EVs), the design of power trains based on in-wheel electric motors represents, from the vehicle dynamics point of view, a very attractive prospect, mainly due to the torque-vectoring capabilities. However, this distributed propulsion also poses some practical challenges, owing to the constraints arising from motor installation in a confined space, to the increased unsprung mass weight and to the integration of the electric motor with the friction brakes. This last issue is the main theme of this work, which, in particular, focuses on the design of the anti-lock braking system (ABS). The proposed structure for the ABS is composed of a tyre slip controller, a wheel torque allocator and a braking supervisor. To address the slip regulation problem, an adaptive controller is devised, offering robustness to uncertainties in the tyre-road friction and featuring a gain-scheduling mechanism based on the vehicle velocity. Further, an optimisation framework is employed in the torque allocator to determine the optimal split between electric and friction brake torque based on energy performance metrics, actuator constraints and different actuators bandwidth. Finally, based on the EV working condition, the priorities of this allocation scheme are adapted by the braking supervisor unit. Simulation results obtained with the CarSim vehicle model, demonstrate the effectiveness of the overall approach.

Therapeutic effects of dl-3-n-butylphthalide in a transgenic mouse model of amyotrophic lateral sclerosis.

PubMed

Feng, Xin-Hong; Yuan, Wei; Peng, Ying; Liu, Ming-Sheng; Cui, Li-Ying

2012-05-01

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive death of the upper and lower motor neurons. Transgenic mice over-expressing a mutant form of the human SOD1 gene develop an ALS-like phenotype. Currently, there is no effective treatment or drug for the fatal disease. Previous studies reported potent efficacy of dl-3-n-butylphthalide (DL-NBP) for several neurodegenerative disorders and cerebral ischemia. SOD1-G93A mice are a mouse model of ALS. In this study, we investigated the efficacy of DL-NBP on this ALS mouse model. Sixty SOD1-G93A female mice were divided into four groups. The vehicle control group received 0 mg×kg(-1)×d(-1) DL-NBP. The experimental groups received DL-NBP with doses of 30, 60 or 120 mg×kg(-1)×d(-1), respectively. For measurement of motor activity, the hanging wire test and rotarod test were performed. Survival statistics were analyzed by Kaplan-Meier survival curves. The body weight of each mouse was recorded twice per week. The statistical motor unit number estimation (MUNE) technique was used to estimate the number of functioning motor units in gastrocnemius muscle. Muscle morphology was evaluated by hematoxylin and eosin staining. Motor neuron quantitation was performed by Nissl staining and microglia activation was observed by immunohistochemistry. Oral administration of 60 mg×kg(-1)×d(-1)1 DL-NBP significantly prolonged survival ((164.78 ± 16.67) days) of SOD1-G93A mice compared with vehicle control ((140.00 ± 16.89) days). Treating mice with DL-NBP (60 mg×kg(-1)×d(-1)) significantly decreased the progression rate of motor deficits and suppressed body weight reduction. Furthermore, we found that treating SOD1-G93A mice with DL-NBP (60 mg×kg(-1)×d(-1)) slowed the rate of MUNE reduction (P < 0.01). Motor neurons were remarkably preserved in the anterior horns in mice treated with DL-NBP (60 mg×kg(-1)×d(-1)) at the stage of 19 weeks (P < 0.01). Treating mice with DL-NBP (60 mg×kg(-1)×d(-1)) significantly reduced CD11b immunoreactivity compared with vehicle control mice (P < 0.05). No significant effect was observed in mice treated with DL-NBP of 30 or 120 mg×kg(-1)×d(-1). The post-disease-onset administration of DL-NBP significantly prolonged survival and improved motor performance in SOD1-G93A mice. DL-NBP may be a potential therapeutic agent for ALS.

Body-Machine Interfaces after Spinal Cord Injury: Rehabilitation and Brain Plasticity.

PubMed

Seáñez-González, Ismael; Pierella, Camilla; Farshchiansadegh, Ali; Thorp, Elias B; Wang, Xue; Parrish, Todd; Mussa-Ivaldi, Ferdinando A

2016-12-19

The purpose of this study was to identify rehabilitative effects and changes in white matter microstructure in people with high-level spinal cord injury following bilateral upper-extremity motor skill training. Five subjects with high-level (C5-C6) spinal cord injury (SCI) performed five visuo-spatial motor training tasks over 12 sessions (2-3 sessions per week). Subjects controlled a two-dimensional cursor with bilateral simultaneous movements of the shoulders using a non-invasive inertial measurement unit-based body-machine interface. Subjects' upper-body ability was evaluated before the start, in the middle and a day after the completion of training. MR imaging data were acquired before the start and within two days of the completion of training. Subjects learned to use upper-body movements that survived the injury to control the body-machine interface and improved their performance with practice. Motor training increased Manual Muscle Test scores and the isometric force of subjects' shoulders and upper arms. Moreover, motor training increased fractional anisotropy (FA) values in the cingulum of the left hemisphere by 6.02% on average, indicating localized white matter microstructure changes induced by activity-dependent modulation of axon diameter, myelin thickness or axon number. This body-machine interface may serve as a platform to develop a new generation of assistive-rehabilitative devices that promote the use of, and that re-strengthen, the motor and sensory functions that survived the injury.

Coupling dynamics in speech gestures: amplitude and rate influences.

PubMed

van Lieshout, Pascal H H M

2017-08-01

Speech is a complex oral motor function that involves multiple articulators that need to be coordinated in space and time at relatively high movement speeds. How this is accomplished remains an important and largely unresolved empirical question. From a coordination dynamics perspective, coordination involves the assembly of coordinative units that are characterized by inherently stable coupling patterns that act as attractor states for task-specific actions. In the motor control literature, one particular model formulated by Haken et al. (Biol Cybern 51(5):347-356, 1985) or HKB has received considerable attention in the way it can account for changes in the nature and stability of specific coordination patterns between limbs or between limbs and external stimuli. In this model (and related versions), movement amplitude is considered a critical factor in the formation of these patterns. Several studies have demonstrated its role for bimanual coordination and similar types of tasks, but for speech motor control such studies are lacking. The current study describes a systematic approach to evaluate the impact of movement amplitude and movement duration on coordination stability in the production of bilabial and tongue body gestures for specific vowel-consonant-vowel strings. The vowel combinations that were used induced a natural contrast in movement amplitude at three speaking rate conditions (slow, habitual, fast). Data were collected on ten young adults using electromagnetic articulography, recording movement data from lips and tongue with high temporal and spatial precision. The results showed that with small movement amplitudes there is a decrease in coordination stability, independent from movement duration. These findings were found to be robust across all individuals and are interpreted as further evidence that principles of coupling dynamics operate in the oral motor control system similar to other motor systems and can be explained in terms of coupling mechanisms between neural oscillators (organized in networks) and effector systems. The relevance of these findings for understanding motor control issues in people with speech disorders is discussed as well.

Afferent control mechanisms involved in the development of soleus fiber alterations in simulated hypogravity

NASA Astrophysics Data System (ADS)

Shenkman, B. S.; Nemirovskaya, T. L.; Shapovalova, K. B.; Podlubnaya, Z. A.; Vikhliantsev, I. M.; Moukhina, A. M.; Kozlovskaya, I. B.

2007-02-01

It was recently established that support withdrawal (withdrawal of support reaction force) in microgravity provokes a sequence of functional shifts in the activity of motor units (inactivation of slow ones) and peripheral muscle apparatus which lead to the decline of postural muscle contractility and alterations in fiber characteristics. However, mechanisms involved in inactivation of the slow motor units and appropriate slow-twitch muscle fiber disuse under the supportless conditions remained unknown. We show here that artificial inactivation of muscles-antagonists (which are known to be hyperactive during unloading) counteracts some of the unloading-induced events in the rat soleus (fiber size reduction, slow-to-fast fiber-type transition and decline of titin and nebulin content). It was also demonstrated that direct activation of the muscarinic receptors of the neostriatum neurons prevented slow-to-fast fiber-type transformation in soleus of hindlimb suspended rats.

Development status of the PDC-1 Parabolic Dish Concentrator

NASA Technical Reports Server (NTRS)

Thostesen, T.; Soczak, I. F.; Pons, R. L.

1982-01-01

The status of development of the 12 m diameter parabolic dish concentrator which is planned for use with the Small Community Solar Thermal Power System. The PDC-1 unit features the use of plastic reflector film bonded to structural plastic gores supported by front-bracing steel ribs. An elevation-over-azimuth mount arrangement is employed, with a conventional wheel-and-track arrangement; outboard trunnions permit the dish to be stored in the face down position, with the added advantage of easy access to the power conversion assembly. The control system is comprised of a central computer (LSI 1123), a manual control panel, a concentrator control unit, two motor controllers, a Sun sensor, and two angular position resolvers. The system is designed for the simultaneous control of several concentrators. The optical testing of reflective panels is described.

New concepts of the reinnervated motor unit revealed by vaccine-associated poliomyelitis.

PubMed

Wiechers, D O

1988-04-01

A late onset of slowly progressive muscle weakness 30-40 years after acute polio is well known. Previous studies by the author and others have demonstrated transmission abnormalities within the reinnervated motor unit. These transmission abnormalities shown by motor unit action potential (MUAP) instability in size and shape with repetitive discharges occurs in postpolio patients who are and who are not complaining of progressive muscle weakness. Although some reinnervated MUAPs do seem to stabilize their neuromuscular transmission with time in mildly affected muscles, the question arises as to whether or not some MUAPs ever stabilize after polio. Two cases of acute polio personally followed by the author, one over a 9 1/2 year period, are presented. In both cases, in muscles where there are more deinnervated muscle fibers than could possibly be reinnervated, the MUAPs have remained unstable. New concepts of function in the reinnervated motor unit following polio are presented.

Effects of fatigue on motor unit firing rate versus recruitment threshold relationships.

PubMed

Stock, Matt S; Beck, Travis W; Defreitas, Jason M

2012-01-01

The purpose of this study was to examine the influence of fatigue on the average firing rate versus recruitment threshold relationships for the vastus lateralis (VL) and vastus medialis. Nineteen subjects performed ten maximum voluntary contractions of the dominant leg extensors. Before and after this fatiguing protocol, the subjects performed a trapezoid isometric muscle action of the leg extensors, and bipolar surface electromyographic signals were detected from both muscles. These signals were then decomposed into individual motor unit action potential trains. For each subject and muscle, the relationship between average firing rate and recruitment threshold was examined using linear regression analyses. For the VL, the linear slope coefficients and y-intercepts for these relationships increased and decreased, respectively, after fatigue. For both muscles, many of the motor units decreased their firing rates. With fatigue, recruitment of higher threshold motor units resulted in an increase in slope for the VL. Copyright © 2011 Wiley Periodicals, Inc.

Vastus lateralis surface and single motor unit EMG following submaximal shortening and lengthening contractions.

PubMed

Altenburg, Teatske M; de Ruiter, Cornelis J; Verdijk, Peter W L; van Mechelen, Willem; de Haan, Arnold

2008-12-01

A single shortening contraction reduces the force capacity of muscle fibers, whereas force capacity is enhanced following lengthening. However, how motor unit recruitment and discharge rate (muscle activation) are adapted to such changes in force capacity during submaximal contractions remains unknown. Additionally, there is limited evidence for force enhancement in larger muscles. We therefore investigated lengthening- and shortening-induced changes in activation of the knee extensors. We hypothesized that when the same submaximal torque had to be generated following shortening, muscle activation had to be increased, whereas a lower activation would suffice to produce the same torque following lengthening. Muscle activation following shortening and lengthening (20 degrees at 10 degrees /s) was determined using rectified surface electromyography (rsEMG) in a 1st session (at 10% and 50% maximal voluntary contraction (MVC)) and additionally with EMG of 42 vastus lateralis motor units recorded in a 2nd session (at 4%-47%MVC). rsEMG and motor unit discharge rates following shortening and lengthening were normalized to isometric reference contractions. As expected, normalized rsEMG (1.15 +/- 0.19) and discharge rate (1.11 +/- 0.09) were higher following shortening (p < 0.05). Following lengthening, normalized rsEMG (0.91 +/- 0.10) was, as expected, lower than 1.0 (p < 0.05), but normalized discharge rate (0.99 +/- 0.08) was not (p > 0.05). Thus, muscle activation was increased to compensate for a reduced force capacity following shortening by increasing the discharge rate of the active motor units (rate coding). In contrast, following lengthening, rsEMG decreased while the discharge rates of active motor units remained similar, suggesting that derecruitment of units might have occurred.

Meaningful task-specific training (MTST) for stroke rehabilitation: a randomized controlled trial.

PubMed

Arya, Kamal Narayan; Verma, Rajesh; Garg, R K; Sharma, V P; Agarwal, Monika; Aggarwal, G G

2012-01-01

The upper extremity motor deficit is one of the functional challenges in post stroke patients. The objective of the present study was to evaluate the effectiveness of the meaningful task-specific training (MTST) on the upper extremity motor recovery during the subacute phase after a stroke. This was a randomized, controlled, double-blinded trial in the neurology department of a university hospital and occupational therapy unit of a rehabilitation institute. A convenience sample of 103 people, 4 to 24 weeks (mean, 12.15 weeks) after the stroke, was randomized into 2 groups (MTST, 51; standard training group, 52). Subjects in the Brunnstrom stage of arm recovery of 2 to 5 were included in the study. Ninety-five participants completed the 8-week follow-up. Participants were assigned to receive either the MTST or dose-matched standard training program based on the Brunnstrom stage and Bobath neurodevelopmental technique, 4 to 5 days a week for 4 weeks. Fugl-Meyer assessment (FMA), Action Research Arm Test (ARAT), Graded Wolf Motor Function Test (GWMFT), and Motor Activity Log (MAL) were outcome measures The MTST group showed a positive improvement in the mean scores on the outcome measures at post and follow-up assessments in comparison to the control group. Further, statistically significant differences were observed in changes between the groups at post and follow-up assessment for FMA, ARAT, GWMFT, and MAL. The MTST produced statistically significant and clinically relevant improvements in the upper extremity motor recovery of the patients who had a subacute stroke.

Control Demonstration of Multiple Doubly-Fed Induction Motors for Hybrid Electric Propulsion

NASA Technical Reports Server (NTRS)

Sadey, David J.; Bodson, Marc; Csank, Jeffrey T.; Hunker, Keith R.; Theman, Casey J.; Taylor, Linda M.

2017-01-01

The Convergent Aeronautics Solutions (CAS) High Voltage-Hybrid Electric Propulsion (HVHEP) task was formulated to support the move into future hybrid-electric aircraft. The goal of this project is to develop a new AC power architecture to support the needs of higher efficiency and lower emissions. This proposed architecture will adopt the use of the doubly-fed induction machine (DFIM) for propulsor drive motor application.The Convergent Aeronautics Solutions (CAS) High Voltage-Hybrid Electric Propulsion (HVHEP) task was formulated to support the move into future hybrid-electric aircraft. The goal of this project is to develop a new AC power architecture to support the needs of higher efficiency and lower emissions. This proposed architecture will adopt the use of the doubly-fed induction machine (DFIM) for propulsor drive motor application. DFIMs are attractive for several reasons, including but not limited to the ability to self-start, ability to operate sub- and super-synchronously, and requiring only fractionally rated power converters on a per-unit basis depending on the required range of operation. The focus of this paper is based specifically on the presentation and analysis of a novel strategy which allows for independent operation of each of the aforementioned doubly-fed induction motors. This strategy includes synchronization, soft-start, and closed loop speed control of each motor as a means of controlling output thrust; be it concurrently or differentially. The demonstration of this strategy has recently been proven out on a low power test bed using fractional horsepower machines. Simulation and hardware test results are presented in the paper.

Feed-forward motor control of ultrafast, ballistic movements.

PubMed

Kagaya, K; Patek, S N

2016-02-01

To circumvent the limits of muscle, ultrafast movements achieve high power through the use of springs and latches. The time scale of these movements is too short for control through typical neuromuscular mechanisms, thus ultrafast movements are either invariant or controlled prior to movement. We tested whether mantis shrimp (Stomatopoda: Neogonodactylus bredini) vary their ultrafast smashing strikes and, if so, how this control is achieved prior to movement. We collected high-speed images of strike mechanics and electromyograms of the extensor and flexor muscles that control spring compression and latch release. During spring compression, lateral extensor and flexor units were co-activated. The strike initiated several milliseconds after the flexor units ceased, suggesting that flexor activity prevents spring release and determines the timing of strike initiation. We used linear mixed models and Akaike's information criterion to serially evaluate multiple hypotheses for control mechanisms. We found that variation in spring compression and strike angular velocity were statistically explained by spike activity of the extensor muscle. The results show that mantis shrimp can generate kinematically variable strikes and that their kinematics can be changed through adjustments to motor activity prior to the movement, thus supporting an upstream, central-nervous-system-based control of ultrafast movement. Based on these and other findings, we present a shishiodoshi model that illustrates alternative models of control in biological ballistic systems. The discovery of feed-forward control in mantis shrimp sets the stage for the assessment of targets, strategic variation in kinematics and the role of learning in ultrafast animals. © 2016. Published by The Company of Biologists Ltd.

Statistically rigorous calculations do not support common input and long-term synchronization of motor-unit firings

PubMed Central

Kline, Joshua C.

2014-01-01

Over the past four decades, various methods have been implemented to measure synchronization of motor-unit firings. In this work, we provide evidence that prior reports of the existence of universal common inputs to all motoneurons and the presence of long-term synchronization are misleading, because they did not use sufficiently rigorous statistical tests to detect synchronization. We developed a statistically based method (SigMax) for computing synchronization and tested it with data from 17,736 motor-unit pairs containing 1,035,225 firing instances from the first dorsal interosseous and vastus lateralis muscles—a data set one order of magnitude greater than that reported in previous studies. Only firing data, obtained from surface electromyographic signal decomposition with >95% accuracy, were used in the study. The data were not subjectively selected in any manner. Because of the size of our data set and the statistical rigor inherent to SigMax, we have confidence that the synchronization values that we calculated provide an improved estimate of physiologically driven synchronization. Compared with three other commonly used techniques, ours revealed three types of discrepancies that result from failing to use sufficient statistical tests necessary to detect synchronization. 1) On average, the z-score method falsely detected synchronization at 16 separate latencies in each motor-unit pair. 2) The cumulative sum method missed one out of every four synchronization identifications found by SigMax. 3) The common input assumption method identified synchronization from 100% of motor-unit pairs studied. SigMax revealed that only 50% of motor-unit pairs actually manifested synchronization. PMID:25210152

Spatial distribution of surface action potentials generated by individual motor units in the human biceps brachii muscle.

PubMed

Rodriguez-Falces, Javier; Negro, Francesco; Gonzalez-Izal, Miriam; Farina, Dario

2013-08-01

This study analyses the spatial distribution of individual motor unit potentials (MUPs) over the skin surface and the influence of motor unit depth and recording configuration on this distribution. Multichannel surface (13×5 electrode grid) and intramuscular (wire electrodes inserted with needles of lengths 15 and 25mm) electromyographic (EMG) signals were concurrently recorded with monopolar derivations from the biceps brachii muscle of 10 healthy subjects during 60-s isometric contractions at 20% of the maximum torque. Multichannel monopolar MUPs of the target motor unit were obtained by spike-triggered averaging of the surface EMG. Amplitude and frequency characteristics of monopolar and bipolar MUPs were calculated for locations along the fibers' direction (longitudinal), and along the direction perpendicular (transverse) to the fibers. In the longitudinal direction, monopolar and bipolar MUPs exhibited marked amplitude changes that extended for 16-32mm and 16-24mm over the innervation and tendon zones, respectively. The variation of monopolar and bipolar MUP characteristics was not symmetrical about the innervation zone. Motor unit depth had a considerable influence on the relative longitudinal variation of amplitude for monopolar MUPs, but not for bipolar MUPs. The transverse extension of bipolar MUPs ranged between 24 and 32mm, whereas that of monopolar MUPs ranged between 72 and 96mm. The mean power spectral frequency of surface MUPs was highly dependent on the transverse electrode location but not on depth. This study provides a basis for the interpretation of the contribution of individual motor units to the interference surface EMG signal. Copyright © 2013 Elsevier Ltd. All rights reserved.

Motor unit activity when young and old adults perform steady contractions while supporting an inertial load

PubMed Central

Gould, Jeffrey R.; Enoka, Roger M.

2013-01-01

The purpose of the study was to compare the discharge characteristics of biceps brachii motor units of young and old adults when they performed steady, submaximal contractions while the arm supported different inertial loads. Young (28 ± 4 yr; n = 16) and old (75 ± 4 yr; n = 14) adults performed steady contractions with the elbow flexors at target forces set at either small (11.7 ± 4.4% maximum) or large (17.8 ± 6.5% maximum) differences below the recruitment threshold force of the motor unit (n = 40). The task was to maintain an elbow angle at 1.57 rad until the motor unit was recruited and discharged action potentials for ∼120 s. Time to recruitment was longer for the larger target force difference (187 ± 227 s vs. 23 ± 46 s, P < 0.001). Once recruited, motor units discharged action potentials either repetitively or intermittently, with a greater proportion of motor units exhibiting the repetitive pattern for old adults. Discharge rate at recruitment and during the steady contraction was similar for the two target force differences for old adults but was greater for the small target force difference for young adults. Discharge variability was similar at recruitment for the two age groups but less for the old adults during the steady contraction. The greatest difference between the present results and those reported previously when the arm pulled against a rigid restraint was that old adults modulated discharge rate less than young adults across the two contraction intensities for both load types. PMID:23221403

A bipedal DNA motor that travels back and forth between two DNA origami tiles.

PubMed

Liber, Miran; Tomov, Toma E; Tsukanov, Roman; Berger, Yaron; Nir, Eyal

2015-02-04

In this work, the successful operation of a dynamic DNA device constructed from two DNA origami building blocks is reported. The device includes a bipedal walker that strides back and forth between the two origami tiles. Two different DNA origami tiles are first prepared separately; they are then joined together in a controlled manner by a set of DNA strands to form a stable track in high yield as confirmed by single-molecule fluorescence (SMF). Second, a bipedal DNA motor, initially attached to one of the two origami units and operated by sequential interaction with "fuel" and "antifuel" DNA strands, moves from one origami tile to another and then back again. The operational yield, measured by SMF, was similar to that of a motor operating on a similar track embedded in a single origami tile, confirming that the transfer across the junction from one tile to the other does not result in dissociation that is any more than that of steps on a single tile. These results demonstrate that moving parts can reliably travel from one origami unit to another, and it demonstrates the feasibility of dynamic DNA molecular machines that are made of more than a single origami building block. This study is a step toward the development of motors that can stride over micrometer distances. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Risk assessment analysis of the future technical unit dedicated to the evaluation and treatment of motor disabilities.

PubMed

Grelier, S; Thetio, M; Quentin, V; Achache, V; Sanchez, N; Leroux, V; Durand, E; Pequignot, R

2011-03-01

The National Hospital of Saint Maurice (HNSM) for Physical Medicine and Rehabilitation aims at strengthening its position as a pivot rehabilitation and physical therapy center. The opening in 2011 of a new unit for the evaluation and treatment of motor disabilities meets this objective. This project includes several parts: clinical, financial, architectural, organizational, applied clinical research as well as dealing with medical equipments and information system. This study focuses on the risk assessment of this future technical unit. This study was conducted by a group of professionals working for the hospital. It started with the design of a functional model to better comprehend the system to be analyzed. Risk assessment consists in confronting this functional model to a list of dangers in order to determine the vulnerable areas of the system. Then the team designed some scenarios to identify the causes, securities barriers and consequences in order to rank the risks. The analysis targeted various dangers, e.g. political, strategic, financial, economical, marketing, clinical and operational. The team identified more than 70 risky scenarios. For 75% of them the criticality level was deemed initially tolerable and under control or unacceptable. The implementation of an action plan for reducing the level of risks before opening this technical unit brought the system down to an acceptable level at 66%. A year prior to opening this technical unit for the evaluation and treatment of motor disabilities, conducting this preliminary risk assessment, with its exhaustive and rigorous methodology, enabled the concerned professionals to work together around an action plan for reducing the risks. 2011 Elsevier Masson SAS. All rights reserved.

Ultracapacitors for fuel saving in small size hybrid vehicles

NASA Astrophysics Data System (ADS)

Solero, L.; Lidozzi, A.; Serrao, V.; Martellucci, L.; Rossi, E.

The main purpose of the paper is to describe a small size hybrid vehicle having ultracapacitors as on-board storage unit. The vehicle on-board main power supply is achieved by a genset being formed of a 250 cm 3 internal combustion engine and a permanent magnet synchronous electric generator, whereas 4 16V-500F ultracapacitors modules are connected in series in order to supply as well as to store the power peaks during respectively acceleration and braking vehicle modes of operation. The traction power is provided by a permanent magnet synchronous electric motor, whereas a distributed power electronic interface is in charge of all the required electronic conversions as well of controlling the operating conditions for each power unit. The paper discusses the implemented control strategy and shows experimental results on the modes of operation of both generation unit and storage unit.

76 FR 34192 - Commercial and Industrial Pumps

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-13

... 1999. The ADL analysis, ``Energy Consumption Characteristics of Commercial Building HVAC Systems... report for the United Nations (``Motor System Efficiency Supply Curves UNIDO,'' Dec. 2010),\\3\\ also used..., A. and A. Hasanbeigi, ``Motor Systems Efficiency Supply Curves,'' United Nations Industrial...

Correlation between discharge timings of pairs of motor units reveals the presence but not the proportion of common synaptic input to motor neurons

PubMed Central

Negro, Francesco; Farina, Dario

2017-01-01

We investigated whether correlation measures derived from pairs of motor unit (MU) spike trains are reliable indicators of the degree of common synaptic input to motor neurons. Several 50-s isometric contractions of the biceps brachii muscle were performed at different target forces ranging from 10 to 30% of the maximal voluntary contraction relying on force feedback. Forty-eight pairs of MUs were examined at various force levels. Motor unit synchrony was assessed by cross-correlation analysis using three indexes: the output correlation as the peak of the cross-histogram (ρ) and the number of synchronous spikes per second (CIS) and per trigger (E). Individual analysis of MU pairs revealed that ρ, CIS, and E were most often positively associated with discharge rate (87, 85, and 76% of the MU pairs, respectively) and negatively with interspike interval variability (69, 65, and 62% of the MU pairs, respectively). Moreover, the behavior of synchronization indexes with discharge rate (and interspike interval variability) varied greatly among the MU pairs. These results were consistent with theoretical predictions, which showed that the output correlation between pairs of spike trains depends on the statistics of the input current and motor neuron intrinsic properties that differ for different motor neuron pairs. In conclusion, the synchronization between MU firing trains is necessarily caused by the (functional) common input to motor neurons, but it is not possible to infer the degree of shared common input to a pair of motor neurons on the basis of correlation measures of their output spike trains. NEW & NOTEWORTHY The strength of correlation between output spike trains is only poorly associated with the degree of common input to the population of motor neurons. The synchronization between motor unit firing trains is necessarily caused by the (functional) common input to motor neurons, but it is not possible to infer the degree of shared common input to a pair of motor neurons on the basis of correlation measures of their output spike trains. PMID:28100652

The electrophysiological response to immunoglobulin therapy in chronic inflammatory demyelinating polyneuropathy.

PubMed

Otto, M; Markvardsen, L; Tankisi, H; Jakobsen, J; Fuglsang-Frederiksen, A

2017-06-01

To characterize changes in motor nerve conduction studies (MNCS) and motor unit number index (MUNIX) following treatment with subcutaneous immunoglobulin and to assess whether these changes are related to muscle strength. Data from 23 patients participating in a randomized, controlled trial were analyzed. MNCS and MUNIX were performed before and after 12 weeks of treatment. Isokinetic strength (IMS) was measured in various muscles together with grip strength (GS). Proximally evoked compound muscle action potential (CMAP) amplitudes and MUNIX tended to be better preserved in treated patients (P=.049 and .045). Changes in other parameters did not differ between groups. There was no correlation between changes in electrophysiological parameters and IMS. Changes in GS were related to median nerve motor conduction velocity, distal motor latency, CMAP amplitudes, and distally evoked CMAP duration (P=.013-.035). Proximally evoked CMAP amplitudes appear to be the best MNCS parameter to assess treatment outcome in chronic inflammatory demyelinating polyneuropathy. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Intra-day signal instabilities affect decoding performance in an intracortical neural interface system

PubMed Central

Perge, János A.; Homer, Mark L.; Malik, Wasim Q.; Cash, Sydney; Eskandar, Emad; Friehs, Gerhard; Donoghue, John P.; Hochberg, Leigh R.

2013-01-01

Objective Motor Neural Interface Systems (NIS) aim to convert neural signals into motor prosthetic or assistive device control, allowing people with paralysis to regain movement or control over their immediate environment. Effector or prosthetic control can degrade if the relationship between recorded neural signals and intended motor behavior changes. Therefore, characterizing both biological and technological sources of signal variability is important for a reliable NIS. Approach To address the frequency and causes of neural signal variability in a spike-based NIS, we analyzed within-day fluctuations in spiking activity and action potential amplitude recorded with silicon microelectrode arrays implanted in the motor cortex of three people with tetraplegia (BrainGate pilot clinical trial, IDE). Main results Eighty-four percent of the recorded units showed a statistically significant change in apparent firing rate (3.8±8.71Hz or 49% of the mean rate) across several-minute epochs of tasks performed on a single session, and seventy-four percent of the units showed a significant change in spike amplitude (3.7±6.5μV or 5.5% of mean spike amplitude). Forty percent of the recording sessions showed a significant correlation in the occurrence of amplitude changes across electrodes, suggesting array micro-movement. Despite the relatively frequent amplitude changes, only 15% of the observed within-day rate changes originated from recording artifacts such as spike amplitude change or electrical noise, while 85% of the rate changes most likely emerged from physiological mechanisms. Computer simulations confirmed that systematic rate changes of individual neurons could produce a directional “bias” in the decoded neural cursor movements. Instability in apparent neuronal spike rates indeed yielded a directional bias in fifty-six percent of all performance assessments in participant cursor control (n=2 participants, 108 and 20 assessments over two years), resulting in suboptimal performance in these sessions. Significance We anticipate that signal acquisition and decoding methods that can adapt to the reported instabilities will further improve the performance of intracortically-based NISs. PMID:23574741

Striatal dysfunction increases basal ganglia output during motor cortex activation in parkinsonian rats.

PubMed

Belluscio, Mariano A; Riquelme, Luis A; Murer, M Gustavo

2007-05-01

During movement, inhibitory neurons in the basal ganglia output nuclei show complex modulations of firing, which are presumptively driven by corticostriatal and corticosubthalamic input. Reductions in discharge should facilitate movement by disinhibiting thalamic and brain stem nuclei while increases would do the opposite. A proposal that nigrostriatal dopamine pathway degeneration disrupts trans-striatal pathways' balance resulting in sustained overactivity of basal ganglia output nuclei neurons and Parkinson's disease clinical signs is not fully supported by experimental evidence, which instead shows abnormal synchronous oscillatory activity in animal models and patients. Yet, the possibility that variation in motor cortex activity drives transient overactivity in output nuclei neurons in parkinsonism has not been explored. In Sprague-Dawley rats with 6-hydroxydopamine (6-OHDA)-induced nigrostriatal lesions, approximately 50% substantia nigra pars reticulata (SNpr) units show abnormal cortically driven slow oscillations of discharge. Moreover, these units selectively show abnormal responses to motor cortex stimulation consisting in augmented excitations of an odd latency, which overlapped that of inhibitory responses presumptively mediated by the trans-striatal direct pathway in control rats. Delivering D1 or D2 dopamine agonists into the striatum of parkinsonian rats by reverse microdialysis reduced these abnormal excitations but had no effect on pathological oscillations. The present study establishes that dopamine-deficiency related changes of striatal function contribute to producing abnormally augmented excitatory responses to motor cortex stimulation in the SNpr. If a similar transient overactivity of basal ganglia output were driven by motor cortex input during movement, it could contribute to impeding movement initiation or execution in Parkinson's disease.

F-wave of single firing motor units: correct or misleading criterion of motoneuron excitability in humans?

PubMed

Kudina, Lydia P; Andreeva, Regina E

2017-03-01

Motoneuron excitability is a critical property for information processing during motor control. F-wave (a motoneuronal recurrent discharge evoked by a motor antidromic volley) is often used as a criterion of motoneuron pool excitability in normal and neuromuscular diseases. However, such using of F-wave calls in question. The present study was designed to explore excitability of single low-threshold motoneurons during their natural firing in healthy humans and to ascertain whether F-wave is a correct measure of motoneuronal excitability. Single motor units (MUs) were activated by gentle voluntary muscle contractions. MU peri-stimulus time histograms and motoneuron excitability changes within a target interspike interval were analysed during testing by motor antidromic and Ia-afferent volleys. It was found that F-waves could be occasionally recorded in some low-threshold MUs. However, during evoking F-wave, in contrast with the H-reflex, peri-stimulus time histograms revealed no statistically significant increase in MU discharge probability. Moreover, surprisingly, motoneurons appeared commonly incapable to fire a recurrent discharge within the most excitable part of a target interval. Thus, the F-wave, unlike the H-reflex, is the incorrect criterion of motoneuron excitability resulting in misleading conclusions. However, it does not exclude the validity of the F-wave as a clinical tool for other aims. It was concluded that the F-wave was first explored in low-threshold MUs during their natural firing. The findings may be useful at interpretations of changes in the motoneuron pool excitability in neuromuscular diseases.

Antigravity posture for analysis of motor unit recruitment: the "45 degree test".

PubMed

Petajan, J H

1990-04-01

The maximum number of different motor unit action potentials (MUAPs), their firing rates, and total MUAP spikes/second recorded by monopolar needle electrode were determined for the biceps brachii muscle during 45-degree elbow flexion. There were 4.2 +/- 1.6 different MUAPs exceeding 100 microV. Mean firing rate was 10.0 +/- 1.7 Hz, and total MUAP spikes/second were 40.3 +/- 18. Recordings from 16 patients with neurogenic atrophy (NA) and just detectable weakness revealed corresponding values of 3.1 +/- 1.7 different MUAPs, a mean rate of 10.2 +/- 1.5 Hz and 30.6 +/- 19 total MUAP spikes/second, not different from normal. In these patients, increased force of muscle contraction was required to activate high threshold motor units firing at high rates. In each of 4 patients just able to hold the arm against gravity, 1 or 2 "overdriven" motor units firing at a mean rate greater than 20 Hz were recorded. In 8 patients with myopathy and just detectable weakness, greater than 100 total MUAP spikes/second were recorded. Antigravity posture as a reference level of innervation has the advantage that motor unit firing rate is set about that of physiologic tremor (10-13 Hz). Its application was helpful in quantifying recruitment.

Inter-rater reliability of motor unit number estimates and quantitative motor unit analysis in the tibialis anterior muscle.

PubMed

Boe, S G; Dalton, B H; Harwood, B; Doherty, T J; Rice, C L

2009-05-01

To establish the inter-rater reliability of decomposition-based quantitative electromyography (DQEMG) derived motor unit number estimates (MUNEs) and quantitative motor unit (MU) analysis. Using DQEMG, two examiners independently obtained a sample of needle and surface-detected motor unit potentials (MUPs) from the tibialis anterior muscle from 10 subjects. Coupled with a maximal M wave, surface-detected MUPs were used to derive a MUNE for each subject and each examiner. Additionally, size-related parameters of the individual MUs were obtained following quantitative MUP analysis. Test-retest MUNE values were similar with high reliability observed between examiners (ICC=0.87). Additionally, MUNE variability from test-retest as quantified by a 95% confidence interval was relatively low (+/-28 MUs). Lastly, quantitative data pertaining to MU size, complexity and firing rate were similar between examiners. MUNEs and quantitative MU data can be obtained with high reliability by two independent examiners using DQEMG. Establishing the inter-rater reliability of MUNEs and quantitative MU analysis using DQEMG is central to the clinical applicability of the technique. In addition to assessing response to treatments over time, multiple clinicians may be involved in the longitudinal assessment of the MU pool of individuals with disorders of the central or peripheral nervous system.

A Muscle’s Force Depends on the Recruitment Patterns of Its Fibers

PubMed Central

Wakeling, James M.; Lee, Sabrina S. M.; Arnold, Allison S.; de Boef Miara, Maria; Biewener, Andrew A.

2012-01-01

Biomechanical models of whole muscles commonly used in simulations of musculoskeletal function and movement typically assume that the muscle generates force as a scaled-up muscle fiber. However, muscles are comprised of motor units that have different intrinsic properties and that can be activated at different times. This study tested whether a muscle model comprised of motor units that could be independently activated resulted in more accurate predictions of force than traditional Hill-type models. Forces predicted by the models were evaluated by direct comparison with the muscle forces measured in situ from the gastrocnemii in goats. The muscle was stimulated tetanically at a range of frequencies, muscle fiber strains were measured using sonomicrometry, and the activation patterns of the different types of motor unit were calculated from electromyographic recordings. Activation patterns were input into five different muscle models. Four models were traditional Hill-type models with different intrinsic speeds and fiber-type properties. The fifth model incorporated differential groups of fast and slow motor units. For all goats, muscles and stimulation frequencies the differential model resulted in the best predictions of muscle force. The in situ muscle output was shown to depend on the recruitment of different motor units within the muscle. PMID:22350666

Age-related motor unit remodeling in the Tibialis Anterior.

PubMed

Siddiqi, Ariba; Kumar, Dinesh; Arjunan, Sridhar

2015-01-01

Limited studies exist on the use of surface electromyogram (EMG) signal features to detect age-related motor unit remodeling in the Tibialis Anterior. Motor unit remodeling leads to declined muscle strength and force steadiness during submaximal contractions which are factors for risk of falls in the elderly. This study investigated the remodeling phenomena in the Tibialis Anterior using sample entropy and higher order statistics. Eighteen young (26.1 ± 2.9 years) and twelve elderly (68.7 ± 9.0 years) participants performed isometric dorsiflexion of the ankle at 20% maximal voluntary contraction (MVC) and their Tibialis Anterior (TA) EMG was recorded. Sample entropy, Gaussianity and Linearity Test statistics were calculated from the recorded EMG for each MVC. Shapiro-Wilk test was used to determine normality, and either a two-tail student t-test or Wilcoxon rank sum test was performed to determine significant difference in the EMG features between the young and old cohorts. Results show age-related motor unit remodeling to be depicted by decreased sample entropy (p <; 0.1), increased non-Gaussianity (p <; 0.05) and lesser degree of linearity in the elderly. This is due to the increased sparsity of the MUAPs as a result of the denervation-reinnervation process, and the decrease in total number of motor units.

75 FR 39045 - New United Motor Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-07

... Manufacturing, Inc., Formerly a Joint Venture of General Motors Corporation and Toyota Motor Corporation, Including On- Site Leased Workers From Corestaff, ABM Janitorial, Toyota Engineering and Manufacturing North... Corporation and Toyota Motor Corporation, including on-site leased workers from Corestaff, ABM Janitorial, and...

Distributed and Modular CAN-Based Architecture for Hardware Control and Sensor Data Integration

PubMed Central

Losada, Diego P.; Fernández, Joaquín L.; Paz, Enrique; Sanz, Rafael

2017-01-01

In this article, we present a CAN-based (Controller Area Network) distributed system to integrate sensors, actuators and hardware controllers in a mobile robot platform. With this work, we provide a robust, simple, flexible and open system to make hardware elements or subsystems communicate, that can be applied to different robots or mobile platforms. Hardware modules can be connected to or disconnected from the CAN bus while the system is working. It has been tested in our mobile robot Rato, based on a RWI (Real World Interface) mobile platform, to replace the old sensor and motor controllers. It has also been used in the design of two new robots: BellBot and WatchBot. Currently, our hardware integration architecture supports different sensors, actuators and control subsystems, such as motor controllers and inertial measurement units. The integration architecture was tested and compared with other solutions through a performance analysis of relevant parameters such as transmission efficiency and bandwidth usage. The results conclude that the proposed solution implements a lightweight communication protocol for mobile robot applications that avoids transmission delays and overhead. PMID:28467381

Steering disturbance rejection using a physics-based neuromusculoskeletal driver model

NASA Astrophysics Data System (ADS)

Mehrabi, Naser; Sharif Razavian, Reza; McPhee, John

2015-10-01

The aim of this work is to develop a comprehensive yet practical driver model to be used in studying driver-vehicle interactions. Drivers interact with their vehicle and the road through the steering wheel. This interaction forms a closed-loop coupled human-machine system, which influences the driver's steering feel and control performance. A hierarchical approach is proposed here to capture the complexity of the driver's neuromuscular dynamics and the central nervous system in the coordination of the driver's upper extremity activities, especially in the presence of external disturbance. The proposed motor control framework has three layers: the first (or the path planning) plans a desired vehicle trajectory and the required steering angles to perform the desired trajectory; the second (or the musculoskeletal controller) actuates the musculoskeletal arm to rotate the steering wheel accordingly; and the final layer ensures the precision control and disturbance rejection of the motor control units. The physics-based driver model presented here can also provide insights into vehicle control in relaxed and tensed driving conditions, which are simulated by adjusting the driver model parameters such as cognition delay and muscle co-contraction dynamics.

Distributed and Modular CAN-Based Architecture for Hardware Control and Sensor Data Integration.

PubMed

Losada, Diego P; Fernández, Joaquín L; Paz, Enrique; Sanz, Rafael

2017-05-03

In this article, we present a CAN-based (Controller Area Network) distributed system to integrate sensors, actuators and hardware controllers in a mobile robot platform. With this work, we provide a robust, simple, flexible and open system to make hardware elements or subsystems communicate, that can be applied to different robots or mobile platforms. Hardware modules can be connected to or disconnected from the CAN bus while the system is working. It has been tested in our mobile robot Rato, based on a RWI (Real World Interface) mobile platform, to replace the old sensor and motor controllers. It has also been used in the design of two new robots: BellBot and WatchBot. Currently, our hardware integration architecture supports different sensors, actuators and control subsystems, such as motor controllers and inertial measurement units. The integration architecture was tested and compared with other solutions through a performance analysis of relevant parameters such as transmission efficiency and bandwidth usage. The results conclude that the proposed solution implements a lightweight communication protocol for mobile robot applications that avoids transmission delays and overhead.

International Space Station Bus Regulation With NASA Glenn Research Center Flywheel Energy Storage System Development Unit

NASA Technical Reports Server (NTRS)

Kascak, Peter E.; Kenny, Barbara H.; Dever, Timothy P.; Santiago, Walter; Jansen, Ralph H.

2001-01-01

An experimental flywheel energy storage system is described. This system is being used to develop a flywheel based replacement for the batteries on the International Space Station (ISS). Motor control algorithms which allow the flywheel to interface with a simplified model of the ISS power bus, and function similarly to the existing ISS battery system, are described. Results of controller experimental verification on a 300 W-hr flywheel are presented.

United States Air Force Graduate Student Summer Support Program (1987). Program Management Report.

DTIC Science & Technology

1987-12-01

were briefed on the benefits and research opportunities of the SFRP. The targeted groups within the University community were faculty of the...Effects on Fine Mary C. Robinson Motor Skill and Decoding Tasks 78 Design of a Mechanism to Control Wind Filiberto Santiago Tunnel Turbulence 79 Low...Systems 81 The Integration of Decision Support Jon A. Shupe Problems into Feature Modeling Based Design 89 r 0 82 Optimal Control of the Wing

75 FR 29723 - Foreign-Trade Zone 29-Louisville, KY; Application for Expansion and Expansion of Manufacturing...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-27

..., plates, filters, bearings, air pumps/compressors, valves, switches, electric motors, tubes/pipes/profiles... electric motors, pinions, magnets, ignition parts, diodes, transistors, resistors, semiconductors, liquid..., starter motors, motor/generator units, alternators, distributors, other static converters, inverter...

76 FR 9000 - Foreign-Trade Zone 29-Louisville, KY, Application for Expansion of Manufacturing Authority...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-16

..., springs, brackets, plates, filters, bearings, air pumps/compressors, valves, switches, electric motors..., clutches, parts of electric motors, pinions, magnets, ignition parts, diodes, transistors, resistors... and chambers, starter motors, motor/generator units, alternators, distributors, other static...

Photoswitching of DNA Hybridization Using a Molecular Motor.

PubMed

Lubbe, Anouk S; Liu, Qing; Smith, Sanne J; de Vries, Jan Willem; Kistemaker, Jos C M; de Vries, Alex H; Faustino, Ignacio; Meng, Zhuojun; Szymanski, Wiktor; Herrmann, Andreas; Feringa, Ben L

2018-04-18

Reversible control over the functionality of biological systems via external triggers may be used in future medicine to reduce the need for invasive procedures. Additionally, externally regulated biomacromolecules are now considered as particularly attractive tools in nanoscience and the design of smart materials, due to their highly programmable nature and complex functionality. Incorporation of photoswitches into biomolecules, such as peptides, antibiotics, and nucleic acids, has generated exciting results in the past few years. Molecular motors offer the potential for new and more precise methods of photoregulation, due to their multistate switching cycle, unidirectionality of rotation, and helicity inversion during the rotational steps. Aided by computational studies, we designed and synthesized a photoswitchable DNA hairpin, in which a molecular motor serves as the bridgehead unit. After it was determined that motor function was not affected by the rigid arms of the linker, solid-phase synthesis was employed to incorporate the motor into an 8-base-pair self-complementary DNA strand. With the photoswitchable bridgehead in place, hairpin formation was unimpaired, while the motor part of this advanced biohybrid system retains excellent photochemical properties. Rotation of the motor generates large changes in structure, and as a consequence the duplex stability of the oligonucleotide could be regulated by UV light irradiation. Additionally, Molecular Dynamics computations were employed to rationalize the observed behavior of the motor-DNA hybrid. The results presented herein establish molecular motors as powerful multistate switches for application in biological environments.

Increases in human motoneuron excitability after cervical spinal cord injury depend on the level of injury.

PubMed

Thomas, Christine K; Häger, Charlotte K; Klein, Cliff S

2017-02-01

After human spinal cord injury (SCI), motoneuron recruitment and firing rate during voluntary and involuntary contractions may be altered by changes in motoneuron excitability. Our aim was to compare F waves in single thenar motor units paralyzed by cervical SCI to those in uninjured controls because at the single-unit level F waves primarily reflect the intrinsic properties of the motoneuron and its initial segment. With intraneural motor axon stimulation, F waves were evident in all 4 participants with C 4 -level SCI, absent in 8 with C 5 or C 6 injury, and present in 6 of 12 Uninjured participants (P < 0.001). The percentage of units that generated F waves differed across groups (C 4 : 30%, C 5 or C 6 : 0%, Uninjured: 16%; P < 0.001). Mean (±SD) proximal axon conduction velocity was slower after C 4 SCI [64 ± 4 m/s (n = 6 units), Uninjured: 73 ± 8 m/s (n = 7 units); P = 0.037]. Mean distal axon conduction velocity differed by group [C 4 : 40 ± 8 m/s (n = 20 units), C 5 or C 6 : 49 ± 9 m/s (n = 28), Uninjured: 60 ± 7 m/s (n = 45); P < 0.001]. Motor unit properties (EMG amplitude, twitch force) only differed after SCI (P ≤ 0.004), not by injury level. Motor units with F waves had distal conduction velocities, M-wave amplitudes, and twitch forces that spanned the respective group range, indicating that units with heterogeneous properties produced F waves. Recording unitary F waves has shown that thenar motoneurons closer to the SCI (C 5 or C 6 ) have reduced excitability whereas those further away (C 4 ) have increased excitability, which may exacerbate muscle spasms. This difference in motoneuron excitability may be related to the extent of membrane depolarization following SCI. Unitary F waves were common in paralyzed thenar muscles of people who had a chronic spinal cord injury (SCI) at the C 4 level compared with uninjured people, but F waves did not occur in people that had SCI at the C 5 or C 6 level. These results highlight that intrinsic motoneuron excitability depends, in part, on how close the motoneurons are to the site of the spinal injury, which could alter the generation and strength of voluntary and involuntary muscle contractions. Copyright © 2017 the American Physiological Society.

Emergence of gamma motor activity in an artificial neural network model of the corticospinal system.

PubMed

Grandjean, Bernard; Maier, Marc A

2017-02-01

Muscle spindle discharge during active movement is a function of mechanical and neural parameters. Muscle length changes (and their derivatives) represent its primary mechanical, fusimotor drive its neural component. However, neither the action nor the function of fusimotor and in particular of γ-drive, have been clearly established, since γ-motor activity during voluntary, non-locomotor movements remains largely unknown. Here, using a computational approach, we explored whether γ-drive emerges in an artificial neural network model of the corticospinal system linked to a biomechanical antagonist wrist simulator. The wrist simulator included length-sensitive and γ-drive-dependent type Ia and type II muscle spindle activity. Network activity and connectivity were derived by a gradient descent algorithm to generate reciprocal, known target α-motor unit activity during wrist flexion-extension (F/E) movements. Two tasks were simulated: an alternating F/E task and a slow F/E tracking task. Emergence of γ-motor activity in the alternating F/E network was a function of α-motor unit drive: if muscle afferent (together with supraspinal) input was required for driving α-motor units, then γ-drive emerged in the form of α-γ coactivation, as predicted by empirical studies. In the slow F/E tracking network, γ-drive emerged in the form of α-γ dissociation and provided critical, bidirectional muscle afferent activity to the cortical network, containing known bidirectional target units. The model thus demonstrates the complementary aspects of spindle output and hence γ-drive: i) muscle spindle activity as a driving force of α-motor unit activity, and ii) afferent activity providing continuous sensory information, both of which crucially depend on γ-drive.

Contributions to muscle force and EMG by combined neural excitation and electrical stimulation

NASA Astrophysics Data System (ADS)

Crago, Patrick E.; Makowski, Nathaniel S.; Cole, Natalie M.

2014-10-01

Objective. Stimulation of muscle for research or clinical interventions is often superimposed on ongoing physiological activity without a quantitative understanding of the impact of the stimulation on the net muscle activity and the physiological response. Experimental studies show that total force during stimulation is less than the sum of the isolated voluntary and stimulated forces, but the occlusion mechanism is not understood. Approach. We develop a model of efferent motor activity elicited by superimposing stimulation during a physiologically activated contraction. The model combines action potential interactions due to collision block, source resetting, and refractory periods with previously published models of physiological motor unit recruitment, rate modulation, force production, and EMG generation in human first dorsal interosseous muscle to investigate the mechanisms and effectiveness of stimulation on the net muscle force and EMG. Main results. Stimulation during a physiological contraction demonstrates partial occlusion of force and the neural component of the EMG, due to action potential interactions in motor units activated by both sources. Depending on neural and stimulation firing rates as well as on force-frequency properties, individual motor unit forces can be greater, smaller, or unchanged by the stimulation. In contrast, voluntary motor unit EMG potentials in simultaneously stimulated motor units show progressive occlusion with increasing stimulus rate. The simulations predict that occlusion would be decreased by a reverse stimulation recruitment order. Significance. The results are consistent with and provide a mechanistic interpretation of previously published experimental evidence of force occlusion. The models also predict two effects that have not been reported previously—voluntary EMG occlusion and the advantages of a proximal stimulation site. This study provides a basis for the rational design of both future experiments and clinical neuroprosthetic interventions involving either motor or sensory stimulation.

Contributions to muscle force and EMG by combined neural excitation and electrical stimulation

PubMed Central

Crago, Patrick E; Makowski, Nathaniel S; Cole, Natalie M

2014-01-01

Objective Stimulation of muscle for research or clinical interventions is often superimposed on ongoing physiological activity, without a quantitative understanding of the impact of the stimulation on the net muscle activity and the physiological response. Experimental studies show that total force during stimulation is less than the sum of the isolated voluntary and stimulated forces, but the occlusion mechanism is not understood. Approach We develop a model of efferent motor activity elicited by superimposing stimulation during a physiologically activated contraction. The model combines action potential interactions due to collision block, source resetting, and refractory periods with previously published models of physiological motor unit recruitment, rate modulation, force production, and EMG generation in human first dorsal interosseous muscle to investigate the mechanisms and effectiveness of stimulation on the net muscle force and EMG. Main Results Stimulation during a physiological contraction demonstrates partial occlusion of force and the neural component of the EMG, due to action potential interactions in motor units activated by both sources. Depending on neural and stimulation firing rates as well as on force-frequency properties, individual motor unit forces can be greater, smaller, or unchanged by the stimulation. In contrast, voluntary motor unit EMG potentials in simultaneously stimulated motor units show progressive occlusion with increasing stimulus rate. The simulations predict that occlusion would be decreased by a reverse stimulation recruitment order. Significance The results are consistent with and provide a mechanistic interpretation of previously published experimental evidence of force occlusion. The models also predict two effects that have not been reported previously - voluntary EMG occlusion and the advantages of a proximal stimulation site. This study provides a basis for the rational design of both future experiments and clinical neuroprosthetic interventions involving either motor or sensory stimulation. PMID:25242203

Twenty-four-hour motor activity in human infants with and without iron deficiency anemia.

PubMed

Angulo-Kinzler, R M; Peirano, P; Lin, E; Algarin, C; Garrido, M; Lozoff, B

2002-12-01

Iron deficiency anemia (IDA) is a very common nutritional problem that alters motor activity. The aim of this study was to compare 24-h motor activity in the home in healthy 6-month-old infants with and without IDA. Activity was assessed via actigraphs on the leg during 24 continuous hours in 17 Chilean infants with IDA and 18 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. The frequency of movement units per minute was determined for each waking/sleep state during the day and night, and the duration of each state was computed. At 6 months of age, there were no differences between anemic and nonanemic infants in time per state. However, infants with IDA showed an overall increase in motor activity compared to controls. These differences were no longer observed at 12 and 18 months of age. Increased activity during the period of IDA raises the issue of a shared underlying mechanism with restless legs syndrome, a sensorimotor dysfunction where iron deficiency increases the severity of the symptoms and iron supplementation ameliorates them. Due to previous findings of decreased motor activity in the laboratory at 12 months during the waking time surrounding an afternoon nap, we also compared those data to a nap in the home. Infants with IDA were less active in the laboratory than in the home. The home versus laboratory results suggest that contextual factors affect the motor activity of IDA infants to a larger extent than controls.

Advanced electric propulsion system concept for electric vehicles. Addendum 1: Voltage considerations

NASA Technical Reports Server (NTRS)

Raynard, A. E.; Forbes, F. E.

1980-01-01

The two electric vehicle propulsion systems that best met cost and performance goals were examined to assess the effect of battery pack voltage on system performance and cost. A voltage range of 54 to 540 V was considered for a typical battery pack capacity of 24 k W-hr. The highest battery specific energy (W-hr/kg) and the lowest cost ($/kW-hr) were obtained at the minimum voltage level. The flywheel system traction motor is a dc, mechanically commutated with shunt field control, and due to the flywheel the traction motor and the battery are not subject to extreme peaks of power demand. The basic system uses a permanent-magnet motor with electronic commutation supplied by an ac power control unit. In both systems battery cost were the major factor in system voltage selection, and a battery pack with the minimum voltage of 54 V produced the lowest life-cycle cost. The minimum life-cycle cost for the basic system with lead-acid batteries was $0.057/km and for the flywheel system was $0.037/km.

An outer arm dynein light chain acts in a conformational switch for flagellar motility

PubMed Central

Patel-King, Ramila S.

2009-01-01

A system distinct from the central pair–radial spoke complex was proposed to control outer arm dynein function in response to alterations in the mechanical state of the flagellum. In this study, we examine the role of a Chlamydomonas reinhardtii outer arm dynein light chain that associates with the motor domain of the γ heavy chain (HC). We demonstrate that expression of mutant forms of LC1 yield dominant-negative effects on swimming velocity, as the flagella continually beat out of phase and stall near or at the power/recovery stroke switchpoint. Furthermore, we observed that LC1 interacts directly with tubulin in a nucleotide-independent manner and tethers this motor unit to the A-tubule of the outer doublet microtubules within the axoneme. Therefore, this dynein HC is attached to the same microtubule by two sites: via both the N-terminal region and the motor domain. We propose that this γ HC–LC1–microtubule ternary complex functions as a conformational switch to control outer arm activity. PMID:19620633

Closed loop performance of a brushless dc motor powered electromechanical actuator for flight control applications. [computerized simulation for Shuttle Orbiter applications

NASA Technical Reports Server (NTRS)

Demerdash, N. A.; Nehl, T. W.

1980-01-01

A comprehensive digital model for the analysis and possible optimization of the closed loop dynamic (instantaneous) performance of a power conditioner fed, brushless dc motor powered, electromechanical actuator system (EMA) is presented. This model was developed for the simulation of the dynamic performance of an actual prototype EMA built for NASA-JSC as a possible alternative to hydraulic actuators for consideration in Space Shuttle Orbiter applications. Excellent correlation was achieved between numerical model simulation and experimental test results obtained from the actual hardware. These results include: various current and voltage waveforms in the machine-power conditioner (MPC) unit, flap position as well as other control loop variables in response to step commands of change of flap position. These results with consequent conclusions are detailed in the paper.

FUZZY LOGIC CONTROL OF ELECTRIC MOTORS AND MOTOR DRIVES: FEASIBILITY STUDY

EPA Science Inventory

The report gives results of a study (part 1) of fuzzy logic motor control (FLMC). The study included: 1) reviews of existing applications of fuzzy logic, of motor operation, and of motor control; 2) a description of motor control schemes that can utilize FLMC; 3) selection of a m...

Statistically rigorous calculations do not support common input and long-term synchronization of motor-unit firings.

PubMed

De Luca, Carlo J; Kline, Joshua C

2014-12-01

Over the past four decades, various methods have been implemented to measure synchronization of motor-unit firings. In this work, we provide evidence that prior reports of the existence of universal common inputs to all motoneurons and the presence of long-term synchronization are misleading, because they did not use sufficiently rigorous statistical tests to detect synchronization. We developed a statistically based method (SigMax) for computing synchronization and tested it with data from 17,736 motor-unit pairs containing 1,035,225 firing instances from the first dorsal interosseous and vastus lateralis muscles--a data set one order of magnitude greater than that reported in previous studies. Only firing data, obtained from surface electromyographic signal decomposition with >95% accuracy, were used in the study. The data were not subjectively selected in any manner. Because of the size of our data set and the statistical rigor inherent to SigMax, we have confidence that the synchronization values that we calculated provide an improved estimate of physiologically driven synchronization. Compared with three other commonly used techniques, ours revealed three types of discrepancies that result from failing to use sufficient statistical tests necessary to detect synchronization. 1) On average, the z-score method falsely detected synchronization at 16 separate latencies in each motor-unit pair. 2) The cumulative sum method missed one out of every four synchronization identifications found by SigMax. 3) The common input assumption method identified synchronization from 100% of motor-unit pairs studied. SigMax revealed that only 50% of motor-unit pairs actually manifested synchronization. Copyright © 2014 the American Physiological Society.

Muscle length-dependent contribution of motoneuron Cav1.3 channels to force production in model slow motor unit.

PubMed

Kim, Hojeong

2017-07-01

Persistent inward current (PIC)-generating Ca v 1.3 channels in spinal motoneuron dendrites are thought to be actively recruited during normal behaviors. However, whether and how the activation of PIC channels influences force output of motor unit remains elusive. Here, building a physiologically realistic model of slow motor unit I demonstrated that force production induced by the PIC activation is much smaller for short than lengthened muscles during the regular firing of the motoneuron that transitions from the quiescent state by either a brief current pulse at the soma or a brief synaptic excitation at the dendrites. By contrast, the PIC-induced force potentiation was maximal for short muscles when the motoneuron switched from a stable low-frequency firing state to a stable high-frequency firing state by the current pulse at the soma. Under the synaptic excitation at the dendrites, however, the force could not be potentiated by the transitioning of the motoneuron from a low- to a high-frequency firing state due to the simultaneous onset of PIC at the dendrites and firing at the soma. The strong dependency of the input-output relationship of the motor unit on the neuromodulation and Ia afferent inputs for the PIC channels was further shown under static variations in muscle length. Taken together, these findings suggest that the PIC activation in the motoneuron dendrites may differentially affect the force production of the motor unit, depending not only on the firing state history of the motoneuron and the variation in muscle length but also on the mode of motor activity. NEW & NOTEWORTHY Ca v 1.3 channels in motoneuron dendrites are actively involved during normal motor activities. To investigate the effects of the activation of motoneuron Ca v 1.3 channels on force production, a model motor unit was built based on best-available data. The simulation results suggest that force potentiation induced by Ca v 1.3 channel activation is strongly modulated not only by firing history of the motoneuron but also by length variation of the muscle as well as neuromodulation inputs from the brainstem. Copyright © 2017 the American Physiological Society.

Mechanism controller system for the optical spectroscopic and infrared remote imaging system instrument on board the Rosetta space mission

NASA Astrophysics Data System (ADS)

Castro Marín, J. M.; Brown, V. J. G.; López Jiménez, A. C.; Rodríguez Gómez, J.; Rodrigo, R.

2001-05-01

The optical, spectroscopic infrared remote imaging system (OSIRIS) is an instrument carried on board the European Space Agency spacecraft Rosetta that will be launched in January 2003 to study in situ the comet Wirtanen. The electronic design of the mechanism controller board (MCB) system of the two OSIRIS optical cameras, the narrow angle camera, and the wide angle camera, is described here. The system is comprised of two boards mounted on an aluminum frame as part of an electronics box that contains the power supply and the digital processor unit of the instrument. The mechanisms controlled by the MCB for each camera are the front door assembly and a filter wheel assembly. The front door assembly for each camera is driven by a four phase, permanent magnet stepper motor. Each filter wheel assembly consists of two, eight filter wheels. Each wheel is driven by a four phase, variable reluctance stepper motor. Each motor, for all the assemblies, also contains a redundant set of four stator phase windings that can be energized separately or in parallel with the main windings. All stepper motors are driven in both directions using the full step unipolar mode of operation. The MCB also performs general housekeeping data acquisition of the OSIRIS instrument, i.e., mechanism position encoders and temperature measurements. The electronic design application used is quite new due to use of a field programmable gate array electronic devices that avoid the use of the now traditional system controlled by microcontrollers and software. Electrical tests of the engineering model have been performed successfully and the system is ready for space qualification after environmental testing. This system may be of interest to institutions involved in future space experiments with similar needs for mechanisms control.

Dynamic neural network models of the premotoneuronal circuitry controlling wrist movements in primates.

PubMed

Maier, M A; Shupe, L E; Fetz, E E

2005-10-01

Dynamic recurrent neural networks were derived to simulate neuronal populations generating bidirectional wrist movements in the monkey. The models incorporate anatomical connections of cortical and rubral neurons, muscle afferents, segmental interneurons and motoneurons; they also incorporate the response profiles of four populations of neurons observed in behaving monkeys. The networks were derived by gradient descent algorithms to generate the eight characteristic patterns of motor unit activations observed during alternating flexion-extension wrist movements. The resulting model generated the appropriate input-output transforms and developed connection strengths resembling those in physiological pathways. We found that this network could be further trained to simulate additional tasks, such as experimentally observed reflex responses to limb perturbations that stretched or shortened the active muscles, and scaling of response amplitudes in proportion to inputs. In the final comprehensive network, motor units are driven by the combined activity of cortical, rubral, spinal and afferent units during step tracking and perturbations. The model displayed many emergent properties corresponding to physiological characteristics. The resulting neural network provides a working model of premotoneuronal circuitry and elucidates the neural mechanisms controlling motoneuron activity. It also predicts several features to be experimentally tested, for example the consequences of eliminating inhibitory connections in cortex and red nucleus. It also reveals that co-contraction can be achieved by simultaneous activation of the flexor and extensor circuits without invoking features specific to co-contraction.

The effect of age and gender on motor vehicle driver injury severity at highway-rail grade crossings in the United States.

PubMed

Hao, Wei; Kamga, Camille; Daniel, Janice

2015-12-01

Based on the Federal Railway Administration (FRA) database, there were 25,945 highway-rail crossing accidents in the United States between 2002 and 2011. With an extensive database of highway-rail grade crossing accidents in the United States from 2002 to 2011, estimation results showed that there were substantial differences across age/gender groups for driver's injury severity. The study applied an ordered probit model to explore the determinants of driver injury severity for motor vehicle drivers at highway-rail grade crossings. The analysis found that there are important behavioral and physical differences between male and female drivers given a highway-rail grade crossing accident happened. Older drivers have higher fatality probabilities when driving in open space under passive control especially during bad weather condition. Younger male drivers are found to be more likely to have severe injuries at rush hour with high vehicle speed passing unpaved highway-rail grade crossings under passive control. Synthesizing these results led to the conclusion that the primary problem with young is risk-taking and lack of vehicle handling skills. The strength of older drivers lies in their aversion to risk, but physical degradation issues which result in longer reaction/perception times and degradation in vision and hearing often counterbalance this attribute. Copyright © 2015 Elsevier Ltd and National Safety Council. All rights reserved.

Physiological recruitment of motor units by high-frequency electrical stimulation of afferent pathways.

PubMed

Dideriksen, Jakob L; Muceli, Silvia; Dosen, Strahinja; Laine, Christopher M; Farina, Dario

2015-02-01

Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation, but electrically evoked muscle activation is in several ways different from voluntary muscle contractions. These differences lead to challenges in the use of NMES for restoring muscle function. We investigated the use of low-current, high-frequency nerve stimulation to activate the muscle via the spinal motoneuron (MN) pool to achieve more natural activation patterns. Using a novel stimulation protocol, the H-reflex responses to individual stimuli in a train of stimulation pulses at 100 Hz were reliably estimated with surface EMG during low-level contractions. Furthermore, single motor unit recruitment by afferent stimulation was analyzed with intramuscular EMG. The results showed that substantially elevated H-reflex responses were obtained during 100-Hz stimulation with respect to a lower stimulation frequency. Furthermore, motor unit recruitment using 100-Hz stimulation was not fully synchronized, as it occurs in classic NMES, and the discharge rates differed among motor units because each unit was activated only after a specific number of stimuli. The most likely mechanism behind these observations is the temporal summation of subthreshold excitatory postsynaptic potentials from Ia fibers to the MNs. These findings and their interpretation were also verified by a realistic simulation model of afferent stimulation of a MN population. These results suggest that the proposed stimulation strategy may allow generation of considerable levels of muscle activation by motor unit recruitment that resembles the physiological conditions. Copyright © 2015 the American Physiological Society.

The effects of poliomyelitis on motor unit behavior during repetitive muscle actions: a case report.

PubMed

Trevino, Michael A; Herda, Trent J; Cooper, Michael A

2014-09-06

Acute paralytic poliomyelitis is caused by the poliovirus and usually results in muscle atrophy and weakness occurring in the lower limbs. Indwelling electromyography has been used frequently to investigate the denervation and innervation characteristics of the affected muscle. Recently developed technology allows the decomposition of the raw surface electromyography signals into the firing instances of single motor units. There is limited information regarding this electromyographic decomposition in clinical populations. In addition, regardless of electromyographic methods, no study has examined muscle activation parameters during repetitive muscle actions in polio patients. Therefore, the purpose of this study was to examine the motor unit firing rates and electromyographic amplitude and center frequency of the vastus lateralis during 20 repetitive isometric muscle actions at 50% maximal voluntary contraction in healthy subjects and one patient that acquired acute paralytic poliomyelitis. One participant that acquired acute type III spinal poliomyelitis (Caucasian male, age = 29 yrs) at 3 months of age and three healthy participants (Caucasian females, age = 19.7 ± 2.1 yrs) participated in this study. The polio participant reported neuromuscular deficiencies as a result of disease in the hips, knees, buttocks, thighs, and lower legs. None of the healthy participants reported any current or ongoing neuromuscular diseases or musculoskeletal injuries. An acute bout of poliomyelitis altered motor unit behavior, such as, healthy participants displayed greater firing rates than the polio patient. The reduction in motor unit firing rates was likely a fatigue protecting mechanism since denervation via poliomyelitis results in a reduction of motorneurons. In addition, the concurrent changes in motor unit firing rates, electromyography amplitude and frequency for the polio participant would suggest that the entire motorneuron pool was utilized in each contraction unlike for the healthy participants. Finally, healthy participants exhibited changes in all electromyographic parameters during the repetitive muscle actions despite successfully completing all contractions with only a slight reduction in force. Thus, caution is warranted when quantifying muscular fatigue via motor unit firing rates and other electromyographic parameters since the parameters changed despite successful completing of all contractions with only a moderate reduction in strength in healthy subjects.

Variable current speed controller for eddy current motors

DOEpatents

Gerth, H.L.; Bailey, J.M.; Casstevens, J.M.; Dixon, J.H.; Griffith, B.O.; Igou, R.E.

1982-03-12

A speed control system for eddy current motors is provided in which the current to the motor from a constant frequency power source is varied by comparing the actual motor speed signal with a setpoint speed signal to control the motor speed according to the selected setpoint speed. A three-phase variable voltage autotransformer is provided for controlling the voltage from a three-phase power supply. A corresponding plurality of current control resistors is provided in series with each phase of the autotransformer output connected to inputs of a three-phase motor. Each resistor is connected in parallel with a set of normally closed contacts of plurality of relays which are operated by control logic. A logic circuit compares the selected speed with the actual motor speed obtained from a digital tachometer monitoring the motor spindle speed and operated the relays to add or substract resistance equally in each phase of the motor input to vary the motor current to control the motor at the selected speed.

Motor Control Abnormalities in Parkinson’s Disease

PubMed Central

Mazzoni, Pietro; Shabbott, Britne; Cortés, Juan Camilo

2012-01-01

The primary manifestations of Parkinson’s disease are abnormalities of movement, including movement slowness, difficulties with gait and balance, and tremor. We know a considerable amount about the abnormalities of neuronal and muscle activity that correlate with these symptoms. Motor symptoms can also be described in terms of motor control, a level of description that explains how movement variables, such as a limb’s position and speed, are controlled and coordinated. Understanding motor symptoms as motor control abnormalities means to identify how the disease disrupts normal control processes. In the case of Parkinson’s disease, movement slowness, for example, would be explained by a disruption of the control processes that determine normal movement speed. Two long-term benefits of understanding the motor control basis of motor symptoms include the future design of neural prostheses to replace the function of damaged basal ganglia circuits, and the rational design of rehabilitation strategies. This type of understanding, however, remains limited, partly because of limitations in our knowledge of normal motor control. In this article, we review the concept of motor control and describe a few motor symptoms that illustrate the challenges in understanding such symptoms as motor control abnormalities. PMID:22675667

Electric vehicle motors and controllers

NASA Technical Reports Server (NTRS)

Secunde, R. R.

1981-01-01

Improved and advanced components being developed include electronically commutated permanent magnet motors of both drum and disk configuration, an unconventional brush commutated motor, and ac induction motors and various controllers. Test results on developmental motors, controllers, and combinations thereof indicate that efficiencies of 90% and higher for individual components, and 80% to 90% for motor/controller combinations can be obtained at rated power. The simplicity of the developmental motors and the potential for ultimately low cost electronics indicate that one or more of these approaches to electric vehicle propulsion may eventually displace presently used controllers and brush commutated dc motors.

Electric vehicle motors and controllers

NASA Astrophysics Data System (ADS)

Secunde, R. R.

Improved and advanced components being developed include electronically commutated permanent magnet motors of both drum and disk configuration, an unconventional brush commutated motor, and ac induction motors and various controllers. Test results on developmental motors, controllers, and combinations thereof indicate that efficiencies of 90% and higher for individual components, and 80% to 90% for motor/controller combinations can be obtained at rated power. The simplicity of the developmental motors and the potential for ultimately low cost electronics indicate that one or more of these approaches to electric vehicle propulsion may eventually displace presently used controllers and brush commutated dc motors.

Extracting motor synergies from random movements for low-dimensional task-space control of musculoskeletal robots.

PubMed

Fu, Kin Chung Denny; Dalla Libera, Fabio; Ishiguro, Hiroshi

2015-10-08

In the field of human motor control, the motor synergy hypothesis explains how humans simplify body control dimensionality by coordinating groups of muscles, called motor synergies, instead of controlling muscles independently. In most applications of motor synergies to low-dimensional control in robotics, motor synergies are extracted from given optimal control signals. In this paper, we address the problems of how to extract motor synergies without optimal data given, and how to apply motor synergies to achieve low-dimensional task-space tracking control of a human-like robotic arm actuated by redundant muscles, without prior knowledge of the robot. We propose to extract motor synergies from a subset of randomly generated reaching-like movement data. The essence is to first approximate the corresponding optimal control signals, using estimations of the robot's forward dynamics, and to extract the motor synergies subsequently. In order to avoid modeling difficulties, a learning-based control approach is adopted such that control is accomplished via estimations of the robot's inverse dynamics. We present a kernel-based regression formulation to estimate the forward and the inverse dynamics, and a sliding controller in order to cope with estimation error. Numerical evaluations show that the proposed method enables extraction of motor synergies for low-dimensional task-space control.

Post-Coma Persons Emerged from a Minimally Conscious State and Showing Multiple Disabilities Learn to Manage a Radio-Listening Activity

ERIC Educational Resources Information Center

Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Colonna, Fabio; Buonocunto, Francesca; Sacco, Valentina; Megna, Marisa; Oliva, Doretta

2012-01-01

This study assessed microswitch-based technology to enable three post-coma adults, who had emerged from a minimally conscious state but presented motor and communication disabilities, to operate a radio device. The material involved a modified radio device, a microprocessor-based electronic control unit, a personal microswitch, and an amplified…

DC motor speed control using fuzzy logic controller

NASA Astrophysics Data System (ADS)

Ismail, N. L.; Zakaria, K. A.; Nazar, N. S. Moh; Syaripuddin, M.; Mokhtar, A. S. N.; Thanakodi, S.

2018-02-01

The automatic control has played a vital role in the advance of engineering and science. Nowadays in industries, the control of direct current (DC) motor is a common practice thus the implementation of DC motor controller speed is important. The main purpose of motor speed control is to keep the rotation of the motor at the present speed and to drive a system at the demand speed. The main purpose of this project is to control speed of DC Series Wound Motor using Fuzzy Logic Controller (FLC). The expectation of this project is the Fuzzy Logic Controller will get the best performance compared to dc motor without controller in terms of settling time (Ts), rise time (Tr), peak time (Tp) and percent overshoot (%OS).

Localised task-dependent motor-unit recruitment in the masseter.

PubMed

Schindler, H J; Hellmann, D; Giannakopoulos, N N; Eiglsperger, U; van Dijk, J P; Lapatki, B G

2014-07-01

Localised motor-unit (MU) recruitment in the masseter was analysed in this study. We investigated whether differential activation behaviour, which has already been reported for distant masseter regions, can also be detected in small muscle subvolumes at the level of single MUs. Two bipolar fine-wire electrodes and an intra-oral 3D bite-force transmitter were used to record intra-muscular electromyograms (EMG) resulting from controlled bite-forces of 10 healthy human subjects (mean age 24.1 ± 1.2 years). Two-hundred and seventeen decomposed MUs were organised into localised MU task groups with different (P < 0.001) force-direction-specific behaviour. Proportions of MUs involved in one, two, three or four examined tasks were 46%, 31%, 18% and 5%, respectively. This study provides evidence of the ability of the neuromuscular system to modify the mechanical output of small masseter subvolumes by differential control of adjacent MUs belonging to distinct task groups. Localised differential activation behaviour of the masseter may be the crucial factor enabling highly flexible and efficient adjustment of the muscle activity in response to complex local biomechanical needs, for example, continually varying bite-forces during the demanding masticatory process. © 2014 John Wiley & Sons Ltd.

Reinforcement learning of targeted movement in a spiking neuronal model of motor cortex.

PubMed

Chadderdon, George L; Neymotin, Samuel A; Kerr, Cliff C; Lytton, William W

2012-01-01

Sensorimotor control has traditionally been considered from a control theory perspective, without relation to neurobiology. In contrast, here we utilized a spiking-neuron model of motor cortex and trained it to perform a simple movement task, which consisted of rotating a single-joint "forearm" to a target. Learning was based on a reinforcement mechanism analogous to that of the dopamine system. This provided a global reward or punishment signal in response to decreasing or increasing distance from hand to target, respectively. Output was partially driven by Poisson motor babbling, creating stochastic movements that could then be shaped by learning. The virtual forearm consisted of a single segment rotated around an elbow joint, controlled by flexor and extensor muscles. The model consisted of 144 excitatory and 64 inhibitory event-based neurons, each with AMPA, NMDA, and GABA synapses. Proprioceptive cell input to this model encoded the 2 muscle lengths. Plasticity was only enabled in feedforward connections between input and output excitatory units, using spike-timing-dependent eligibility traces for synaptic credit or blame assignment. Learning resulted from a global 3-valued signal: reward (+1), no learning (0), or punishment (-1), corresponding to phasic increases, lack of change, or phasic decreases of dopaminergic cell firing, respectively. Successful learning only occurred when both reward and punishment were enabled. In this case, 5 target angles were learned successfully within 180 s of simulation time, with a median error of 8 degrees. Motor babbling allowed exploratory learning, but decreased the stability of the learned behavior, since the hand continued moving after reaching the target. Our model demonstrated that a global reinforcement signal, coupled with eligibility traces for synaptic plasticity, can train a spiking sensorimotor network to perform goal-directed motor behavior.

Another face of placebo: The lessebo effect in Parkinson disease

PubMed Central

Mestre, Tiago A.; Shah, Prakesh; Marras, Connie; Tomlinson, George

2014-01-01

Objective: To study the impact of negative expectation related to receiving a placebo (the “lessebo effect”) on efficacy outcome measures of symptomatic treatments in Parkinson disease (PD). Methods: We conducted meta-analyses of double-blind randomized controlled trials (RCTs) of dopamine agonists in PD and compared the pooled mean score change of the motor section of the Unified Parkinson's Disease Rating Scale (mUPDRS) across active treatment arms according to the presence of a placebo arm or the probability of placebo assignment (0%, <50%, and 50%) of the original RCT. A mixed-effects model was used. Heterogeneity was assessed by subgroup analyses and meta-regression modeling. Results: A total of 28 study arms were extracted from active-controlled trials (3,277 patients) and 42 from placebo-controlled trials (4,554 patients). The overall difference between groups in the pooled mean score change in the mUPDRS was 1.6 units (95% confidence interval [CI] 0.2, 3.0; p = 0.023), in favor of the active-controlled group. In subgroup analyses, this difference was of higher magnitude in the early PD group without motor fluctuations (3.3 mUPDRS units, 95% CI 1.1, 5.4; p = 0.003) and for study duration ≤12 weeks (4.1 mUPDRS units, 95% CI 1.0, 7.2; p = 0.009). There was no between-group difference using probability of placebo assignment as criterion. Conclusions: This study shows that the use of a placebo can be associated with a clinically significant reduction in the magnitude of change of the mUPDRS after an active treatment in RCTs for PD. These new findings have potential implications in the development of new treatments and appraisal of current treatment options for PD and possibly for other neurologic disorders. PMID:24658930

Discharge properties of motor units during steady isometric contractions performed with the dorsiflexor muscles

PubMed Central

Klass, Malgorzata; Duchateau, Jacques; Enoka, Roger M.

2012-01-01

The purpose of this study was to record the discharge characteristics of tibialis anterior motor units over a range of target forces and to import these data, along with previously reported observations, into a computational model to compare experimental and simulated measures of torque variability during isometric contractions with the dorsiflexor muscles. The discharge characteristics of 44 motor units were quantified during brief isometric contractions at torques that ranged from recruitment threshold to an average of 22 ± 14.4% maximal voluntary contraction (MVC) torque above recruitment threshold. The minimal [range: 5.8–19.8 pulses per second (pps)] and peak (range: 8.6–37.5 pps) discharge rates of motor units were positively related to the recruitment threshold torque (R2 ≥ 0.266; P < 0.001). The coefficient of variation for interspike interval at recruitment was positively associated with recruitment threshold torque (R2 = 0.443; P < 0.001) and either decreased exponentially or remained constant as target torque increased above recruitment threshold torque. The variability in the simulated torque did not differ from the experimental values once the recruitment range was set to ∼85% MVC torque, and the association between motor twitch contraction times and peak twitch torque was defined as a weak linear association (R2 = 0.096; P < 0.001). These results indicate that the steadiness of isometric contractions performed with the dorsiflexor muscle depended more on the distributions of mechanical properties than discharge properties across the population of motor units in the tibialis anterior. PMID:22442023

Discharge properties of motor units during steady isometric contractions performed with the dorsiflexor muscles.

PubMed

Jesunathadas, Mark; Klass, Malgorzata; Duchateau, Jacques; Enoka, Roger M

2012-06-01

The purpose of this study was to record the discharge characteristics of tibialis anterior motor units over a range of target forces and to import these data, along with previously reported observations, into a computational model to compare experimental and simulated measures of torque variability during isometric contractions with the dorsiflexor muscles. The discharge characteristics of 44 motor units were quantified during brief isometric contractions at torques that ranged from recruitment threshold to an average of 22 ± 14.4% maximal voluntary contraction (MVC) torque above recruitment threshold. The minimal [range: 5.8-19.8 pulses per second (pps)] and peak (range: 8.6-37.5 pps) discharge rates of motor units were positively related to the recruitment threshold torque (R(2) ≥ 0.266; P < 0.001). The coefficient of variation for interspike interval at recruitment was positively associated with recruitment threshold torque (R(2) = 0.443; P < 0.001) and either decreased exponentially or remained constant as target torque increased above recruitment threshold torque. The variability in the simulated torque did not differ from the experimental values once the recruitment range was set to ∼85% MVC torque, and the association between motor twitch contraction times and peak twitch torque was defined as a weak linear association (R(2) = 0.096; P < 0.001). These results indicate that the steadiness of isometric contractions performed with the dorsiflexor muscle depended more on the distributions of mechanical properties than discharge properties across the population of motor units in the tibialis anterior.

Prenatal micronutrient supplementation and intellectual and motor function in early school-aged children in Nepal.

PubMed

Christian, Parul; Murray-Kolb, Laura E; Khatry, Subarna K; Katz, Joanne; Schaefer, Barbara A; Cole, Pamela M; Leclerq, Steven C; Tielsch, James M

2010-12-22

Iron and zinc are important for the development of both intellectual and motor skills. Few studies have examined whether iron and zinc supplementation during gestation, a critical period of central nervous system development, affects children's later functioning. To examine intellectual and motor functioning of children whose mothers received micronutrient supplementation during pregnancy. Cohort follow-up of 676 children aged 7 to 9 years in June 2007-April 2009 who had been born to women in 4 of 5 groups of a community-based, double-blind, randomized controlled trial of prenatal micronutrient supplementation between 1999 and 2001 in rural Nepal. Study children were also in the placebo group of a subsequent preschool iron and zinc supplementation trial. Women whose children were followed up had been randomly assigned to receive daily iron/folic acid, iron/folic acid/zinc, or multiple micronutrients containing these plus 11 other micronutrients, all with vitamin A, vs a control group of vitamin A alone from early pregnancy through 3 months postpartum. These children did not receive additional micronutrient supplementation other than biannual vitamin A supplementation. Children's intellectual functioning, assessed using the Universal Nonverbal Intelligence Test (UNIT); tests of executive function, including go/no-go, the Stroop test, and backward digit span; and motor function, assessed using the Movement Assessment Battery for Children (MABC) and finger-tapping test. The difference across outcomes was significant (Bonferroni-adjusted P < .001) for iron/folic acid vs control but not for other supplement groups. The mean UNIT T score in the iron/folic acid group was 51.7 (SD, 8.5) and in the control group was 48.2 (SD, 10.2), with an adjusted mean difference of 2.38 (95% confidence interval [CI], 0.06-4.70; P = .04). Differences were not significant between the control group and either the iron/folic acid/zinc (0.73; 95% CI, -0.95 to 2.42) or multiple micronutrient (1.00; 95% CI, -0.55 to 2.56) groups. In tests of executive function, scores were better in the iron/folic acid group relative to the control group for the Stroop test (adjusted mean difference in proportion who failed, -0.14; 95% CI, -0.23 to -0.04) and backward digit span (adjusted mean difference, 0.36; 95% CI, 0.01-0.71) but not for the go/no-go test. The MABC score was lower (better) in the iron/folic acid group compared with the control group but not after adjustment for confounders (mean difference, -1.47; 95% CI, -3.06 to 0.12; P = .07). Finger-tapping test scores were higher (mean difference, 2.05; 95% CI, 0.87-3.24; P = .001) in the iron/folic acid group. Aspects of intellectual functioning including working memory, inhibitory control, and fine motor functioning among offspring were positively associated with prenatal iron/folic acid supplementation in an area where iron deficiency is prevalent. clinicaltrials.gov Identifier: NCT00115271.

40 CFR 85.1502 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Procedure at part 86. (7) Independent commercial importer (ICI). An importer who is not an original... by an OEM or ICI in the course of motor vehicle or motor vehicle engine production. (14) United... time of resale (for a motor vehicle or motor vehicle engine owned by the ICI at the time of importation...

40 CFR 85.1502 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Procedure at part 86. (7) Independent commercial importer (ICI). An importer who is not an original... by an OEM or ICI in the course of motor vehicle or motor vehicle engine production. (14) United... time of resale (for a motor vehicle or motor vehicle engine owned by the ICI at the time of importation...

40 CFR 85.1502 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Procedure at part 86. (7) Independent commercial importer (ICI). An importer who is not an original... by an OEM or ICI in the course of motor vehicle or motor vehicle engine production. (14) United... time of resale (for a motor vehicle or motor vehicle engine owned by the ICI at the time of importation...

40 CFR 85.1502 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Procedure at part 86. (7) Independent commercial importer (ICI). An importer who is not an original... by an OEM or ICI in the course of motor vehicle or motor vehicle engine production. (14) United... time of resale (for a motor vehicle or motor vehicle engine owned by the ICI at the time of importation...

77 FR 8898 - Certain Starter Motors and Alternators; Determination Not To Review an Initial Determination...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-15

... joint motion to terminate the investigation as to respondent Electric Motor Service, Inc. (EMS) of Logan... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-755] Certain Starter Motors and... for importation, and the sale within the United States after importation of certain starter motors and...

49 CFR 178.320 - General requirements applicable to all DOT specification cargo tank motor vehicles.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., intermediate bulk containers, multi-unit tank car tanks, portable tanks, or tank cars. Cargo tank motor vehicle... specification cargo tank motor vehicles. 178.320 Section 178.320 Transportation Other Regulations Relating to... MATERIALS REGULATIONS SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle...

49 CFR 178.320 - General requirements applicable to all DOT specification cargo tank motor vehicles.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., intermediate bulk containers, multi-unit tank car tanks, portable tanks, or tank cars. Cargo tank motor vehicle... specification cargo tank motor vehicles. 178.320 Section 178.320 Transportation Other Regulations Relating to... (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation...

49 CFR 178.320 - General requirements applicable to all DOT specification cargo tank motor vehicles.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., intermediate bulk containers, multi-unit tank car tanks, portable tanks, or tank cars. Cargo tank motor vehicle... specification cargo tank motor vehicles. 178.320 Section 178.320 Transportation Other Regulations Relating to... (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation...

49 CFR 178.320 - General requirements applicable to all DOT specification cargo tank motor vehicles.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., intermediate bulk containers, multi-unit tank car tanks, portable tanks, or tank cars. Cargo tank motor vehicle... specification cargo tank motor vehicles. 178.320 Section 178.320 Transportation Other Regulations Relating to... (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation...

49 CFR 178.320 - General requirements applicable to all DOT specification cargo tank motor vehicles.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., intermediate bulk containers, multi-unit tank car tanks, portable tanks, or tank cars. Cargo tank motor vehicle... specification cargo tank motor vehicles. 178.320 Section 178.320 Transportation Other Regulations Relating to... (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation...

78 FR 74225 - Decision That Certain Nonconforming Motor Vehicles Are Eligible for Importation

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-10

...-0136] Decision That Certain Nonconforming Motor Vehicles Are Eligible for Importation AGENCY: National... decisions by NHTSA that certain motor vehicles not originally manufactured to comply with all applicable Federal Motor Vehicle Safety Standards (FMVSS) are eligible for importation into the United States because...

Flywheel energy storage for electromechanical actuation systems

NASA Technical Reports Server (NTRS)

Hockney, Richard L.; Goldie, James H.; Kirtley, James L.

1991-01-01

The authors describe a flywheel energy storage system designed specifically to provide load-leveling for a thrust vector control (TVC) system using electromechanical actuators (EMAs). One of the major advantages of an EMA system over a hydraulic system is the significant reduction in total energy consumed during the launch profile. Realization of this energy reduction will, however, require localized energy storage capable of delivering the peak power required by the EMAs. A combined flywheel-motor/generator unit which interfaces directly to the 20-kHz power bus represents an ideal candidate for this load leveling. The overall objective is the definition of a flywheel energy storage system for this application. The authors discuss progress on four technical objectives: (1) definition of the specifications for the flywheel-motor/generator system, including system-level trade-off analysis; (2) design of the flywheel rotor; (3) design of the motor/generator; and (4) determination of the configuration for the power management system.

Regenerative flywheel energy storage system. Volume 3: Life cycle and cost-benefit analysis of a battery-flywheel electric car

NASA Astrophysics Data System (ADS)

1980-06-01

Fabrication of the inductor motor, the flywheel, the power conditioner, and the system control is described. Test results of the system operating over the SAE j227a Schedule D driving cycle are given and are compared to the calculated value. The flywheel energy storage system consists of a solid rotor, synchronous, inductor-type, flywheel drive machine electrically coupled to a dc battery electric propulsion system through a load-commutated inverter. The motor/alernator unit is coupled mechanically to a small steel flywheel which provides a portion of the vehicle's accelerating energy and regenerates the vehicle's braking energy. Laboratory simulation of the electric vehicle propulsion system included a 108 volt, lead-acid battery bank and a separately excited dc propulsion motor coupled to a flywheel and generator which simulate the vehicle's inertia and losses.

Flywheel energy storage for electromechanical actuation systems

NASA Astrophysics Data System (ADS)

Hockney, Richard L.; Goldie, James H.; Kirtley, James L.

The authors describe a flywheel energy storage system designed specifically to provide load-leveling for a thrust vector control (TVC) system using electromechanical actuators (EMAs). One of the major advantages of an EMA system over a hydraulic system is the significant reduction in total energy consumed during the launch profile. Realization of this energy reduction will, however, require localized energy storage capable of delivering the peak power required by the EMAs. A combined flywheel-motor/generator unit which interfaces directly to the 20-kHz power bus represents an ideal candidate for this load leveling. The overall objective is the definition of a flywheel energy storage system for this application. The authors discuss progress on four technical objectives: (1) definition of the specifications for the flywheel-motor/generator system, including system-level trade-off analysis; (2) design of the flywheel rotor; (3) design of the motor/generator; and (4) determination of the configuration for the power management system.

En route to surface-bound electric field-driven molecular motors.

PubMed

Jian, Huahua; Tour, James M

2003-06-27

Four caltrop-shaped molecules that might be useful as surface-bound electric field-driven molecular motors have been synthesized. The caltrops are comprised of a pair of electron donor-acceptor arms and a tripod base. The molecular arms are based on a carbazole or oligo(phenylene ethynylene) core with a strong net dipole. The tripod base uses a silicon atom as its core. The legs of the tripod bear sulfur-tipped bonding units, as acetyl-protected benzylic thiols, for bonding to a gold surface. The geometry of the tripod base allows the caltrop to project upward from a metallic surface after self-assembly. Ellipsometric studies show that self-assembled monolayers of the caltrops are formed on Au surfaces with molecular thicknesses consistent with the desired upright-shaft arrangement. As a result, the zwitterionic molecular arms might be controllable when electric fields are applied around the caltrops, thereby constituting field-driven motors.

Motor unit activation patterns during concentric wrist flexion in humans with different muscle fibre composition.

PubMed

Søgaard, K; Christensen, H; Fallentin, N; Mizuno, M; Quistorff, B; Sjøgaard, G

1998-10-01

Muscle activity was recorded from the flexor carpi radialis muscle during static and dynamic-concentric wrist flexion in six subjects, who had exhibited large differences in histochemically identified muscle fibre composition. Motor unit recruitment patterns were identified by sampling 310 motor units and counting firing rates in pulses per second (pps). During concentric wrist flexion at 30% of maximal exercise intensity the mean firing rate was 27 (SD 13) pps. This was around twice the value of 12 (SD 5) pps recorded during sustained static contraction at 30% of maximal voluntary contraction, despite a larger absolute force level during the static contraction. A similar pattern of higher firing rates during dynamic exercise was seen when concentric wrist flexion at 60% of maximal exercise intensity [30 (SD 14) pps] was compared with sustained static contraction at 60% of maximal voluntary contraction [19 (SD 8) pps]. The increase in dynamic exercise intensity was accomplished by recruitment of additional motor units rather than by increasing the firing rate as during static contractions. No difference in mean firing rates was found among subjects with different muscle fibre composition, who had previously exhibited marked differences in metabolic response during corresponding dynamic contractions. It was concluded that during submaximal dynamic contractions motor unit firing rate cannot be deduced from observations during static contractions and that muscle fibre composition may play a minor role.

Computationally efficient models of neuromuscular recruitment and mechanics.

PubMed

Song, D; Raphael, G; Lan, N; Loeb, G E

2008-06-01

We have improved the stability and computational efficiency of a physiologically realistic, virtual muscle (VM 3.*) model (Cheng et al 2000 J. Neurosci. Methods 101 117-30) by a simpler structure of lumped fiber types and a novel recruitment algorithm. In the new version (VM 4.0), the mathematical equations are reformulated into state-space representation and structured into a CMEX S-function in SIMULINK. A continuous recruitment scheme approximates the discrete recruitment of slow and fast motor units under physiological conditions. This makes it possible to predict force output during smooth recruitment and derecruitment without having to simulate explicitly a large number of independently recruited units. We removed the intermediate state variable, effective length (Leff), which had been introduced to model the delayed length dependency of the activation-frequency relationship, but which had little effect and could introduce instability under physiological conditions of use. Both of these changes greatly reduce the number of state variables with little loss of accuracy compared to the original VM. The performance of VM 4.0 was validated by comparison with VM 3.1.5 for both single-muscle force production and a multi-joint task. The improved VM 4.0 model is more suitable for the analysis of neural control of movements and for design of prosthetic systems to restore lost or impaired motor functions. VM 4.0 is available via the internet and includes options to use the original VM model, which remains useful for detailed simulations of single motor unit behavior.

Computationally efficient models of neuromuscular recruitment and mechanics

NASA Astrophysics Data System (ADS)

Song, D.; Raphael, G.; Lan, N.; Loeb, G. E.

2008-06-01

We have improved the stability and computational efficiency of a physiologically realistic, virtual muscle (VM 3.*) model (Cheng et al 2000 J. Neurosci. Methods 101 117-30) by a simpler structure of lumped fiber types and a novel recruitment algorithm. In the new version (VM 4.0), the mathematical equations are reformulated into state-space representation and structured into a CMEX S-function in SIMULINK. A continuous recruitment scheme approximates the discrete recruitment of slow and fast motor units under physiological conditions. This makes it possible to predict force output during smooth recruitment and derecruitment without having to simulate explicitly a large number of independently recruited units. We removed the intermediate state variable, effective length (Leff), which had been introduced to model the delayed length dependency of the activation-frequency relationship, but which had little effect and could introduce instability under physiological conditions of use. Both of these changes greatly reduce the number of state variables with little loss of accuracy compared to the original VM. The performance of VM 4.0 was validated by comparison with VM 3.1.5 for both single-muscle force production and a multi-joint task. The improved VM 4.0 model is more suitable for the analysis of neural control of movements and for design of prosthetic systems to restore lost or impaired motor functions. VM 4.0 is available via the internet and includes options to use the original VM model, which remains useful for detailed simulations of single motor unit behavior.

Signal-independent timescale analysis (SITA) and its application for neural coding during reaching and walking.

PubMed

Zacksenhouse, Miriam; Lebedev, Mikhail A; Nicolelis, Miguel A L

2014-01-01

What are the relevant timescales of neural encoding in the brain? This question is commonly investigated with respect to well-defined stimuli or actions. However, neurons often encode multiple signals, including hidden or internal, which are not experimentally controlled, and thus excluded from such analysis. Here we consider all rate modulations as the signal, and define the rate-modulations signal-to-noise ratio (RM-SNR) as the ratio between the variance of the rate and the variance of the neuronal noise. As the bin-width increases, RM-SNR increases while the update rate decreases. This tradeoff is captured by the ratio of RM-SNR to bin-width, and its variations with the bin-width reveal the timescales of neural activity. Theoretical analysis and simulations elucidate how the interactions between the recovery properties of the unit and the spectral content of the encoded signals shape this ratio and determine the timescales of neural coding. The resulting signal-independent timescale analysis (SITA) is applied to investigate timescales of neural activity recorded from the motor cortex of monkeys during: (i) reaching experiments with Brain-Machine Interface (BMI), and (ii) locomotion experiments at different speeds. Interestingly, the timescales during BMI experiments did not change significantly with the control mode or training. During locomotion, the analysis identified units whose timescale varied consistently with the experimentally controlled speed of walking, though the specific timescale reflected also the recovery properties of the unit. Thus, the proposed method, SITA, characterizes the timescales of neural encoding and how they are affected by the motor task, while accounting for all rate modulations.

Motor development and sensory processing: A comparative study between preterm and term infants.

PubMed

Cabral, Thais Invenção; Pereira da Silva, Louise Gracelli; Tudella, Eloisa; Simões Martinez, Cláudia Maria

2014-10-16

Infants born preterm and/or with low birth weight may present a clinical condition of organic instability and usually face a long period of hospitalization in the Neonatal Intensive Care Units, being exposed to biopsychosocial risk factors to their development due to decreased spontaneous movement and excessive sensory stimuli. This study assumes that there are relationships between the integration of sensory information of preterm infants, motor development and their subsequent effects. To evaluate the sensory processing and motor development in preterm infants aged 4-6 months and compare performance data with their peers born at term. This was a cross-sectional and comparative study consisting of a group of preterm infants (n=15) and a group of term infants (n=15), assessed using the Test of Sensory Functions in Infants (TSFI) and the Alberta Infant Motor Scale (AIMS). The results showed no significant association between motor performance on the AIMS scale (total score) and sensory processing in the TSFI (total score). However, all infants who scored abnormal in the total TSFI score, subdomain 1, and subdomain 5 presented motor performance at or below the 5th percentile on the AIMS scale. Since all infants who presented definite alteration in tolerating tactile deep pressure and poor postural control are at risk of delayed gross motor development, there may be peculiarities not detected by the tests used that seem to establish some relationship between sensory processing and motor development. Copyright © 2014 Elsevier Ltd. All rights reserved.

Smart motor technology

NASA Technical Reports Server (NTRS)

Packard, D.; Schmitt, D.

1984-01-01

Current spacecraft design relies upon microprocessor control; however, motors usually require extensive additional electronic circuitry to interface with these microprocessor controls. An improved control technique that allows a smart brushless motor to connect directly to a microprocessor control system is described. An actuator with smart motors receives a spacecraft command directly and responds in a closed loop control mode. In fact, two or more smart motors can be controlled for synchronous operation.

46 CFR 111.70-3 - Motor controllers and motor-control centers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... pump, elevator, steering gear, or auxiliary that is vital to the vessel's propulsion system, except a... ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Motor Circuits, Controllers, and Protection § 111.70-3 Motor... operation is not hazardous. If automatic restart is hazardous, the motor controller must have low-voltage...

46 CFR 111.70-3 - Motor controllers and motor-control centers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... pump, elevator, steering gear, or auxiliary that is vital to the vessel's propulsion system, except a... ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Motor Circuits, Controllers, and Protection § 111.70-3 Motor... operation is not hazardous. If automatic restart is hazardous, the motor controller must have low-voltage...

46 CFR 111.70-3 - Motor controllers and motor-control centers.

Code of Federal Regulations, 2012 CFR

2012-10-01

... pump, elevator, steering gear, or auxiliary that is vital to the vessel's propulsion system, except a... ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Motor Circuits, Controllers, and Protection § 111.70-3 Motor... operation is not hazardous. If automatic restart is hazardous, the motor controller must have low-voltage...

46 CFR 111.70-3 - Motor controllers and motor-control centers.

Code of Federal Regulations, 2014 CFR

2014-10-01

... pump, elevator, steering gear, or auxiliary that is vital to the vessel's propulsion system, except a... ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Motor Circuits, Controllers, and Protection § 111.70-3 Motor... operation is not hazardous. If automatic restart is hazardous, the motor controller must have low-voltage...

46 CFR 111.70-3 - Motor controllers and motor-control centers.

Code of Federal Regulations, 2013 CFR

2013-10-01

... pump, elevator, steering gear, or auxiliary that is vital to the vessel's propulsion system, except a... ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Motor Circuits, Controllers, and Protection § 111.70-3 Motor... operation is not hazardous. If automatic restart is hazardous, the motor controller must have low-voltage...

Development of Ulta-Efficient Electric Motors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shoykhet, B.; Schiferl, R.; Duckworth, R.

2008-05-01

Electric motors utilize a large amount of electrical energy in utility and industrial applications. Electric motors constructed with high temperature superconducting (HTS) materials have the potential to dramatically reduce electric motor size and losses. HTS motors are best suited for large motor applications at ratings above 1000 horsepower (hp), where the energy savings from the efficiency improvement can overcome the additional power required to keep the superconductors on the rotor cooled. Large HTS based motors are expected to be half the volume and have half the losses of conventional induction motors of the same rating. For a 5000 hp industrialmore » motor, this energy savings can result in $50,000 in operating cost savings over the course of a single year of operation. Since large horsepower motors utilize (or convert) about 30% of the electrical power generated in the United States and about 70% of large motors are candidates for replacement by HTS motors, the annual energy savings potential through the utilization of HTS motors can be up to $1 Billion in the United States alone. Research in the application of HTS materials to electric motors has lead to a number of HTS motor prototypes yet no industrial HTS motor product has yet been introduced. These motor demonstrations have been synchronous motors with HTS field windings, on the rotor. Figure 1-1 shows a solid model rendering of this type of motor. The rotor winding is made with HTS coils that are held at cryogenic temperature by introducing cooling fluid from the cryocooler to the rotor through a transfer coupling. The stator winding is made of copper wire. The HTS winding is thermally isolated from the warm armature and motor shafts by a vacuum insulation space and through the use of composite torque tubes. The stator in Figure 1-1 is an air core stator in that the stator teeth and a small part of the yoke is made up of nonmagnetic material so the magnetic fields distribute themselves as if in air. Between the HTS field winding and the physical air gap is a series of concentric cylinders that act as vacuum insulation space walls as well as conducting paths for induced currents to flow in order to shield the HTS winding and the rotor cold space from time dependent fields. These time dependent fields may be caused by rotor hunting, during a change in motor load, or by non-fundamental component voltages and currents applied by the inverter. These motors are variable speed controlled by the inverter. Common large motor utility and industrial applications are pump and fan drives that are best suited by a variable speed motor. Inverter control of the HTS motor eliminates the need to design the rotor for line starting, which would dump a large amount of heat into the rotor that would then heavily tax the cryogenic cooling system. The field winding is fed by a brushless exciter that provides DC current to the HTS rotor winding. The stator winding is air or water cooled. Technical and commercial hurdles to industrial HTS motor product introduction and customer acceptance include (1) the high cost of HTS wire and the cryogenic cooling system components, (2) customer concerns about reliability of HTS motors, and (3) the ability to attain the loss reduction potential of large HTS motors. Reliance Electric has demonstrated a number of HTS based electric motors up to a 1000 hp, variable speed synchronous motor with an HTS field winding in the year 2000. In 2001 this motor was tested to 1600 hp with a sinusoidal (constant frequency) supply. Figure 1-2 shows the HTS motor on the dynamometer test stand in the Reliance Electric test lab. The extensive test program of the 1000 hp motor successfully demonstrated the technical feasibility of large HTS motors and the basic technologies involved, however the test results did indicate the need for design refinements. In addition, test results served to identify other more fundamental critical technology issues, and revealed the need to continue research efforts in order to improve future HTS motor first cost, reliability, and performance. The lessons learned from the development and testing of the 1000 hp motor were the basis for the tasks proposed for the project that is being described in this final report. These eight tasks and the technology and commercial issues they address are listed in Table 1-1.« less

Dynamic action units slip in speech production errors ☆

PubMed Central

Goldstein, Louis; Pouplier, Marianne; Chen, Larissa; Saltzman, Elliot; Byrd, Dani

2008-01-01

In the past, the nature of the compositional units proposed for spoken language has largely diverged from the types of control units pursued in the domains of other skilled motor tasks. A classic source of evidence as to the units structuring speech has been patterns observed in speech errors – “slips of the tongue”. The present study reports, for the first time, on kinematic data from tongue and lip movements during speech errors elicited in the laboratory using a repetition task. Our data are consistent with the hypothesis that speech production results from the assembly of dynamically defined action units – gestures – in a linguistically structured environment. The experimental results support both the presence of gestural units and the dynamical properties of these units and their coordination. This study of speech articulation shows that it is possible to develop a principled account of spoken language within a more general theory of action. PMID:16822494

Design and Qualification of a SmallSat Stepper Motor Driver, Flight Results On-Board the Yes2 Satellite

NASA Astrophysics Data System (ADS)

Graczyk, R.; Kruijff, M.; Spiliotopoulos, I.

2008-08-01

Drivers for stepper motors are a commonly required critical technology for small satellites. This paper highlights the stepper driver design, test, and mission performance for the second Young Engineers' Satellite (YES2). The unit integrates the required digital and power parts and was developed with generic low-cost satellite applications in mind. One of the key mechanisms in YES2 is a friction brake containing a stepper motor which is in turn controlled by a stepper driver. The friction brake was used to control the deployment speed such that the tether deployed according to a pre-described two-stage trajectory. The stepper driver was itself commanded by an on-board computer that used tether deployment data as input and provided the new required position of the brake as output. The stepper driver design was driven by the requirements of a low cost yet reliable redundant design, use of a micro-controller and software commonly known to students, very small dimension, good thermal behavior and capable of delivering high torque at high efficiency. The work followed as much as possible ESA's design standards and was qualified by electromagnetic compatibility, thermal vacuum and shaker tests. It was functionally tested in real-time ground tether deployments. Mission data shows the stepper driver performed well in flight.

The guidance methodology of a new automatic guided laser theodolite system

NASA Astrophysics Data System (ADS)

Zhang, Zili; Zhu, Jigui; Zhou, Hu; Ye, Shenghua

2008-12-01

Spatial coordinate measurement systems such as theodolites, laser trackers and total stations have wide application in manufacturing and certification processes. The traditional operation of theodolites is manual and time-consuming which does not meet the need of online industrial measurement, also laser trackers and total stations need reflective targets which can not realize noncontact and automatic measurement. A new automatic guided laser theodolite system is presented to achieve automatic and noncontact measurement with high precision and efficiency which is comprised of two sub-systems: the basic measurement system and the control and guidance system. The former system is formed by two laser motorized theodolites to accomplish the fundamental measurement tasks while the latter one consists of a camera and vision system unit mounted on a mechanical displacement unit to provide azimuth information of the measured points. The mechanical displacement unit can rotate horizontally and vertically to direct the camera to the desired orientation so that the camera can scan every measured point in the measuring field, then the azimuth of the corresponding point is calculated for the laser motorized theodolites to move accordingly to aim at it. In this paper the whole system composition and measuring principle are analyzed, and then the emphasis is laid on the guidance methodology for the laser points from the theodolites to move towards the measured points. The guidance process is implemented based on the coordinate transformation between the basic measurement system and the control and guidance system. With the view field angle of the vision system unit and the world coordinate of the control and guidance system through coordinate transformation, the azimuth information of the measurement area that the camera points at can be attained. The momentary horizontal and vertical changes of the mechanical displacement movement are also considered and calculated to provide real time azimuth information of the pointed measurement area by which the motorized theodolite will move accordingly. This methodology realizes the predetermined location of the laser points which is within the camera-pointed scope so that it accelerates the measuring process and implements the approximate guidance instead of manual operations. The simulation results show that the proposed method of automatic guidance is effective and feasible which provides good tracking performance of the predetermined location of laser points.

Permanent magnet DC motor control by using arduino and motor drive module BTS7960

NASA Astrophysics Data System (ADS)

Syukriyadin, S.; Syahrizal, S.; Mansur, G.; Ramadhan, H. P.

2018-05-01

This study proposes a control system for permanent magnet DC (PMDC) motor. PMDC drive control system has two critical parameters: control and monitoring. Control system includes rotation speed control and direction of rotation of motor using motor drive module BTS7960. The PWM signal has a fixed frequency of waves with varying duty cycles (between 0% and 100%), so the motor rotation can be regulated gradually using a potentiometer already programmed on the Arduino Uno board. The motor rotation direction setting uses the H-bridge circuit method using a 3-way switch to set the direction of forward-reverse rotation of the motor. The monitoring system includes measurements of rotational speed, current, and voltage. Motor rotation speed can be adjusted from the armature voltage settings through the duty cycle PWM setting so that the motor speed can be increased or decreased by the desired duty cycle. From the unload PMDC motor test results it has also been shown that the torque of the motor is relatively constant when there is a change in speed from low rpm to high rpm or vice versa.

Study protocol: an early intervention program to improve motor outcome in preterm infants: a randomized controlled trial and a qualitative study of physiotherapy performance and parental experiences

PubMed Central

2012-01-01

Abstract Background Knowledge about early physiotherapy to preterm infants is sparse, given the risk of delayed motor development and cerebral palsy. Methods/Design A pragmatic randomized controlled study has been designed to assess the effect of a preventative physiotherapy program carried out in the neonatal intensive care unit. Moreover, a qualitative study is carried out to assess the physiotherapy performance and parents' experiences with the intervention. The aim of the physiotherapy program is to improve motor development i.e. postural control and selective movements in these infants. 150 infants will be included and randomized to either intervention or standard follow-up. The infants in the intervention group will be given specific stimulation to facilitate movements based on the individual infant's development, behavior and needs. The physiotherapist teaches the parents how to do the intervention and the parents receive a booklet with photos and descriptions of the intervention. Intervention is carried out twice a day for three weeks (week 34, 35, 36 postmenstrual age). Standardized tests are carried out at baseline, term age and at three, six, 12 and 24 months corrected age. In addition eight triads (infant, parent and physiotherapist) are observed and videotaped in four clinical encounters each to assess the process of physiotherapy performance. The parents are also interviewed on their experiences with the intervention and how it influences on the parent-child relationship. Eight parents from the follow up group are interviewed about their experience. The interviews are performed according to the same schedule as the standardized measurements. Primary outcome is at two years corrected age. Discussion The paper presents the protocol for a randomized controlled trial designed to study the effect of physiotherapy to preterm infants at neonatal intensive care units. It also studies physiotherapy performance and the parent's experiences with the intervention. Trial registration ClinicalTrials.gov NCT01089296 PMID:22336194

Assessment of Psychophysiological Response and Specific Fine Motor Skills in Combat Units.

PubMed

Sánchez-Molina, Joaquín; Robles-Pérez, José J; Clemente-Suárez, Vicente J

2018-03-02

Soldiers´ training and experience can influence the outcome of the missions, as well as their own physical integrity. The objective of this research was to analyze the psycho-physiological response and specific motor skills in an urban combat simulation with two units of infantry with different training and experience. psychophysiological parameters -Heart Rate, blood oxygen saturation, glucose and blood lactate, cortical activation, anxiety and heart rate variability-, as well as fine motor skills were analyzed in 31 male soldiers of the Spanish Army, 19 belonging to the Light Infantry Brigade, and 12 to the Heavy Forces Infantry Brigade, before and after an urban combat simulation. A combat simulation provokes an alteration of the psycho-physiological basal state in soldiers and a great unbalance in the sympathetic-vagal interaction. The specific training of Light Infantry unit involves lower metabolic, cardiovascular, and anxiogenic response not only previous, but mainly after a combat maneuver, than Heavy Infantry unit's. No differences were found in relation with fine motor skills, improving in both cases after the maneuver. This fact should be taken into account for betterment units´ deployment preparation in current theaters of operations.

Age at spinal cord injury determines muscle strength

PubMed Central

Thomas, Christine K.; Grumbles, Robert M.

2014-01-01

As individuals with spinal cord injury (SCI) age they report noticeable deficits in muscle strength, endurance and functional capacity when performing everyday tasks. These changes begin at ~45 years. Here we present a cross-sectional analysis of paralyzed thenar muscle and motor unit contractile properties in two datasets obtained from different subjects who sustained a cervical SCI at different ages (≤46 years) in relation to data from uninjured age-matched individuals. First, completely paralyzed thenar muscles were weaker when C6 SCI occurred at an older age. Muscles were also significantly weaker if the injury was closer to the thenar motor pools (C6 vs. C4). More muscles were strong (>50% uninjured) in those injured at a younger (≤25 years) vs. young age (>25 years), irrespective of SCI level. There was a reduction in motor unit numbers in all muscles tested. In each C6 SCI, only ~30 units survived vs. 144 units in uninjured subjects. Since intact axons only sprout 4–6 fold, the limits for muscle reinnervation have largely been met in these young individuals. Thus, any further reduction in motor unit numbers with time after these injuries will likely result in chronic denervation, and may explain the late-onset muscle weakness routinely described by people with SCI. In a second dataset, paralyzed thenar motor units were more fatigable than uninjured units. This gap widened with age and will reduce functional reserve. Force declines were not due to electromyographic decrements in either group so the site of failure was beyond excitation of the muscle membrane. Together, these results suggest that age at SCI is an important determinant of long-term muscle strength, and fatigability, both of which influence functional capacity. PMID:24478643

Menstrual cycle mediates vastus medialis and vastus medialis oblique muscle activity.

PubMed

Tenan, Matthew S; Peng, Yi-Ling; Hackney, Anthony C; Griffin, Lisa

2013-11-01

Sports medicine professionals commonly describe two functionally different units of the vastus medialis (VM), the VM, and the vastus medialis oblique (VMO), but the anatomical support is equivocal. The functional difference of the VMO is principle to rehabilitation programs designed to alleviate anterior knee pain, a pathology that is known to have a greater occurrence in women. The purpose of this study was to determine whether the motor units of the VM and VMO are differentially recruited and if this recruitment pattern has an effect of sex or menstrual cycle phase. Single motor unit recordings from the VM and VMO were obtained for men and women during an isometric ramp knee extension. Eleven men were tested once. Seven women were tested during five different phases of the menstrual cycle, determined by basal body temperature mapping. The recruitment threshold and the initial firing rate at recruitment were determined from 510 motor unit recordings. The initial firing rate was lower in the VMO than that in the VM in women (P < 0.001) but not in men. There was no difference in recruitment thresholds for the VM and VMO in either sex or across the menstrual cycle. There was a main effect of menstrual phase on initial firing rate, showing increases from the early follicular to late luteal phase (P = 0.003). The initial firing rate in the VMO was lower than that in the VM during ovulatory (P = 0.009) and midluteal (P = 0.009) phases. The relative control of the VM and VMO changes across the menstrual cycle. This could influence patellar pathologies that have a higher incidence in women.

10 CFR 431.404 - Imported electric motors.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Imported electric motors. 431.404 Section 431.404 Energy... EQUIPMENT General Provisions § 431.404 Imported electric motors. (a) Under sections 331 and 345 of the Act, any person importing an electric motor into the United States must comply with the provisions of the...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jankowski, Todd Andrew; Gamboa, Jose A

Cooling devices for use with electric submersible pump motors include a refrigerator attached to the end of the electric submersible pump motor with the evaporator heat exchanger accepting all or a portion of the heat load from the motor. The cooling device can be a self-contained bolt-on unit, so that minimal design changes to existing motors are required.

50 CFR 35.5 - Commercial enterprises, roads, motor vehicles, motorized equipment, motorboats, aircraft...

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 9 2012-10-01 2012-10-01 false Commercial enterprises, roads, motor vehicles, motorized equipment, motorboats, aircraft, mechanical transport, structures, and installations. 35.5 Section 35.5 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE NATIONAL WILDLIFE REFUG...

Hermatically sealed motor blower unit with stator inside hollow armature

DOEpatents

Donelian, Khatchik O.

1976-01-20

13. A hermetically sealed motor blower unit comprising, in combination, a sealed housing having a thrust plate mounted therein and having a re-entrant wall forming a central cavity in said housing, a rotor within said housing, said rotor comprising an impeller, a hollow shaft embracing said cavity and a thrust collar adapted to cooperate with said thrust plate to support the axial thrust of said shaft, one or more journal bearings within said housing for supporting the radial load of said shaft and electric motor means for rotating said rotor, said motor means comprising a motor-stator located within said cavity and adapted to cooperate through a portion of said re-entrant wall with a motor-rotor mounted within said hollow shaft, the portion of said re-entrant wall located between said motor-stator and said motor-rotor being made relatively thin to reduce electrical losses, the bearing surfaces of said thrust plate, thrust collar and journal bearings being in communication with the discharge of said impeller, whereby fluid pumped by said impeller can flow directly to said bearing surfaces to lubricate them.

Bobath Concept versus constraint-induced movement therapy to improve arm functional recovery in stroke patients: a randomized controlled trial.

PubMed

Huseyinsinoglu, Burcu Ersoz; Ozdincler, Arzu Razak; Krespi, Yakup

2012-08-01

To compare the effects of the Bobath Concept and constraint-induced movement therapy on arm functional recovery among stroke patients with a high level of function on the affected side. A single-blinded, randomized controlled trial. Outpatient physiotherapy department of a stroke unit. A total of 24 patients were randomized to constraint-induced movement therapy or Bobath Concept group. The Bobath Concept group was treated for 1 hour whereas the constraint-induced movement therapy group received training for 3 hours per day during 10 consecutive weekdays. Main measures were the Motor Activity Log-28, the Wolf Motor Function Test, the Motor Evaluation Scale for Arm in Stroke Patients and the Functional Independence Measure. The two groups were found to be homogeneous based on demographic variables and baseline measurements. Significant improvements were seen after treatment only in the 'Amount of use' and 'Quality of movement' subscales of the Motor Activity Log-28 in the constraint-induced movement therapy group over the the Bobath Concept group (P = 0.003; P = 0.01 respectively). There were no significant differences in Wolf Motor Function Test 'Functional ability' (P = 0.137) and 'Performance time' (P = 0.922), Motor Evaluation Scale for Arm in Stroke Patients (P = 0.947) and Functional Independence Measure scores (P = 0.259) between the two intervention groups. Constraint-induced movement therapy and the Bobath Concept have similar efficiencies in improving functional ability, speed and quality of movement in the paretic arm among stroke patients with a high level of function. Constraint-induced movement therapy seems to be slightly more efficient than the Bobath Concept in improving the amount and quality of affected arm use.

Controller for computer control of brushless dc motors. [automobile engines

NASA Technical Reports Server (NTRS)

Hieda, L. S. (Inventor)

1981-01-01

A motor speed and torque controller for brushless d.c. motors provides an unusually smooth torque control arrangement. The controller provides a means for controlling a current waveform in each winding of a brushless dc motor by synchronization of an excitation pulse train from a programmable oscillator. Sensing of torque for synchronization is provided by a light beam chopper mounted on the motor rotor shaft. Speed and duty cycle are independently controlled by controlling the frequency and pulse width output of the programmable oscillator. A means is also provided so that current transitions from one motor winding to another is effected without abrupt changes in output torque.

KSC-08pd1859

NASA Image and Video Library

2008-07-01

CAPE CANAVERAL, Fla. – In the Assembly and Refurbishment Facility at NASA's Kennedy Space Center, a crane is lowered over the aft skirt for the Ares 1-X rocket. The segment is being lifted into a machine shop work stand for drilling modifications. The modifications will prepare it for the installation of the auxiliary power unit controller, the reduced-rate gyro unit, the booster decelerator motors and the booster tumble motors. Ares I is an in-line, two-stage rocket that will transport the Orion crew exploration vehicle to low-Earth orbit. Ares I-X is a test rocket. The Ares I first stage will be a five-segment solid rocket booster based on the four-segment design used for the shuttle. Ares I’s fifth booster segment allows the launch vehicle to lift more weight and reach a higher altitude before the first stage separates from the upper stage, which ignites in midflight to propel the Orion spacecraft to Earth orbit. Photo credit: NASA/Jim Grossmann

A New Type of Motor: Pneumatic Step Motor

PubMed Central

Stoianovici, Dan; Patriciu, Alexandru; Petrisor, Doru; Mazilu, Dumitru; Kavoussi, Louis

2011-01-01

This paper presents a new type of pneumatic motor, a pneumatic step motor (PneuStep). Directional rotary motion of discrete displacement is achieved by sequentially pressurizing the three ports of the motor. Pulsed pressure waves are generated by a remote pneumatic distributor. The motor assembly includes a motor, gearhead, and incremental position encoder in a compact, central bore construction. A special electronic driver is used to control the new motor with electric stepper indexers and standard motion control cards. The motor accepts open-loop step operation as well as closed-loop control with position feedback from the enclosed sensor. A special control feature is implemented to adapt classic control algorithms to the new motor, and is experimentally validated. The speed performance of the motor degrades with the length of the pneumatic hoses between the distributor and motor. Experimental results are presented to reveal this behavior and set the expectation level. Nevertheless, the stepper achieves easily controllable precise motion unlike other pneumatic motors. The motor was designed to be compatible with magnetic resonance medical imaging equipment, for actuating an image-guided intervention robot, for medical applications. For this reason, the motors were entirely made of nonmagnetic and dielectric materials such as plastics, ceramics, and rubbers. Encoding was performed with fiber optics, so that the motors are electricity free, exclusively using pressure and light. PneuStep is readily applicable to other pneumatic or hydraulic precision-motion applications. PMID:21528106

Estimating the number of motor units using random sums with independently thinned terms.

PubMed

Müller, Samuel; Conforto, Adriana Bastos; Z'graggen, Werner J; Kaelin-Lang, Alain

2006-07-01

The problem of estimating the numbers of motor units N in a muscle is embedded in a general stochastic model using the notion of thinning from point process theory. In the paper a new moment type estimator for the numbers of motor units in a muscle is denned, which is derived using random sums with independently thinned terms. Asymptotic normality of the estimator is shown and its practical value is demonstrated with bootstrap and approximative confidence intervals for a data set from a 31-year-old healthy right-handed, female volunteer. Moreover simulation results are presented and Monte-Carlo based quantiles, means, and variances are calculated for N in{300,600,1000}.

[Clinico-electromyographic evaluation of the state of motor units of the hand muscles replanted after traumatic amputation].

PubMed

Rezkov, G I

1991-01-01

Needle electromyography was used to study motor units of the muscles leading away the thumb and little finger, replanted after traumatic amputation of the large segment of the upper limb in 34 patients. A direct relationship was discovered between the time of the appearance of action potentials of motor units (PMU), recovery of the movements, and trauma level. The appearance of clear PMU associated with movement recovery was recorded not earlier than 6-7 months after trauma. Analysis of PMU is a reliable criterion for the recovery of the own movements of the muscles and function of the neuromotor apparatus in patients with the replanted upper limb segment.

Diabetes and driving safety: science, ethics, legality and practice.

PubMed

Cox, Daniel J; Singh, Harsimran; Lorber, Daniel

2013-04-01

Diabetes affects over 25 million people in the United States, most of whom are over the age of 16 and many of whom are licensed to drive a motor vehicle. Safe operation of a motor vehicle requires complex interactions of cognitive and motor functions and medical conditions that affect these functions often will increase the risk of motor vehicle accidents (MVA). In the case of diabetes, hypoglycemia is the most common factor that has been shown to increase MVA rates. When people with diabetes are compared with nondiabetic controls, systematic analyses show that the relative risk of MVA is increased by between 12% and 19% (Relative Risk Ratio 1.12-1.19). In comparison, the RRR for attention deficit hyperactivity disorder is 4.4 and for sleep apnea is 2.4. Epidemiologic research suggests that patients at risk for hypoglycemia-related MVAs may have some characteristics in common, including a history of severe hypoglycemia or of hypoglycemia-related driving mishaps. Experimental studies also have shown that people with a history of hypoglycemia-related driving mishaps have abnormal counter-regulatory responses to hypoglycemia and greater cognitive impairments during moderate hypoglycemia.

Control Circuit For Two Stepping Motors

NASA Technical Reports Server (NTRS)

Ratliff, Roger; Rehmann, Kenneth; Backus, Charles

1990-01-01

Control circuit operates two independent stepping motors, one at a time. Provides following operating features: After selected motor stepped to chosen position, power turned off to reduce dissipation; Includes two up/down counters that remember at which one of eight steps each motor set. For selected motor, step indicated by illumination of one of eight light-emitting diodes (LED's) in ring; Selected motor advanced one step at time or repeatedly at rate controlled; Motor current - 30 mA at 90 degree positions, 60 mA at 45 degree positions - indicated by high or low intensity of LED that serves as motor-current monitor; Power-on reset feature provides trouble-free starts; To maintain synchronism between control circuit and motors, stepping of counters inhibited when motor power turned off.

Effects of robot-assisted upper limb rehabilitation on daily function and real-world arm activity in patients with chronic stroke: a randomized controlled trial.

PubMed

Liao, Wan-Wen; Wu, Ching-Yi; Hsieh, Yu-Wei; Lin, Keh-Chung; Chang, Wan-Ying

2012-02-01

To compare the outcome of robot-assisted therapy with dose-matched active control therapy by using accelerometers to study functional recovery in chronic stroke patients. Prospective, randomized, controlled trial. Stroke units in three medical centres. Twenty patients post stroke for a mean of 22 months. Robot-assisted therapy (n = 10) or dose-matched active control therapy (n = 10). All patients received either of these two therapies for 90-105 minutes each day, 5 days per week, for four weeks. Outcome measures included arm activity ratio (the ratio of mean activity between the impaired and unimpaired arm) and scores on the Fugl-Meyer Assessment Scale, Functional Independence Measure, Motor Activity Log and ABILHAND questionnaire. The robot-assisted therapy group significantly increased motor function, hemiplegic arm activity and bilateral arm coordination (Fugl-Meyer Assessment Scale: 51.20 ± 8.82, P = 0.002; mean arm activity ratio: 0.76 ± 0.10, P = 0.026; ABILHAND questionnaire: 1.24 ± 0.28, P = 0.043) compared with the dose-matched active control group (Fugl-Meyer Assessment Scale: 40.90 ± 13.14; mean arm movement ratio: 0.69 ± 0.11; ABILHAND questionnaire: 0.95 ± 0.43). Symmetrical and bilateral robotic practice, combined with functional task training, can significantly improve motor function, arm activity, and self-perceived bilateral arm ability in patients late after stroke.