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Sample records for muscle reflex thresholds

  1. Relationship between stretch reflex thresholds and voluntary arm muscle activation in patients with spasticity.

    PubMed

    Musampa, Nadine K; Mathieu, Pierre A; Levin, Mindy F

    2007-08-01

    Previous studies have shown that deficits in agonist-antagonist muscle activation in the single-joint elbow system in patients with spastic hemiparesis are directly related to limitations in the range of regulation of the thresholds of muscle activation. We extended these findings to the double-joint, shoulder-elbow system in these patients. Ten non-disabled individuals and 11 stroke survivors with spasticity in upper limb muscles participated. Stroke survivors had sustained a single unilateral stroke 6-36 months previously, had full pain-free passive range of motion of the affected shoulder and elbow and had some voluntary control of the arm. EMG activity from four elbow and two shoulder muscles was recorded during quasi-static (<5 degrees /s) stretching of elbow flexors/extensors and during slow voluntary elbow flexion/extension movement through full range. Stretches and active movements were initiated from full elbow flexion or extension with the shoulder in three different initial positions (60 degrees , 90 degrees , 145 degrees horizontal abduction). SRTs were defined as the elbow angle at which EMG signals began to exceed 2SD of background noise. SRT angles obtained by passive muscle stretch were compared with the angles at which the respective muscles became activated during voluntary elbow movements. SRTs in elbow flexors were correlated with clinical spasticity scores. SRTs of elbow flexors and extensors were within the biomechanical range of the joint and varied with changes in the shoulder angle in all subjects with hemiparesis but could not be reached in this range in all healthy subjects when muscles were initially relaxed. In patients, limitations in the regulation of SRTs resulted in a subdivision of all-possible shoulder-elbow arm configurations into two areas, one in which spasticity was present ("spatial spasticity zone") and another in which it was absent. Spatial spasticity zones were different for different muscles in different patients but

  2. Mentalis muscle related reflexes.

    PubMed

    Gündüz, Ayşegül; Uyanık, Özlem; Ertürk, Özdem; Sohtaoğlu, Melis; Kızıltan, Meral Erdemir

    2016-05-01

    The mentalis muscle (MM) arises from the incisive fossa of the mandible, raises and protrudes the lower lip. Here, we aim to characterize responses obtained from MM by supraorbital and median electrical as well as auditory stimuli in a group of 16 healthy volunteers who did not have clinical palmomental reflex. Reflex activities were recorded from the MM and orbicularis oculi (O.oc) after supraorbital and median electrical as well as auditory stimuli. Response rates over MM were consistent after each stimulus, however, mean latencies of MM response were longer than O.oc responses by all stimulation modalities. Shapes and amplitudes of responses from O.oc and MM were similar. Based on our findings, we may say that MM motoneurons have connections with trigeminal, vestibulocochlear and lemniscal pathways similar to other facial muscles and electrophysiological recording of MM responses after electrical and auditory stimulation is possible in healthy subjects. PMID:26721248

  3. Sweet taste and menthol increase cough reflex thresholds.

    PubMed

    Wise, Paul M; Breslin, Paul A S; Dalton, Pamela

    2012-06-01

    Cough is a vital protective reflex that is triggered by both mechanical and chemical stimuli. The current experiments explored how chemosensory stimuli modulate this important reflex. Cough thresholds were measured using a single-inhalation capsaicin challenge. Experiment 1 examined the impact of sweet taste: Cough thresholds were measured after rinsing the mouth with a sucrose solution (sweet) or with water (control). Experiment 2 examined the impact of menthol: Cough thresholds were measured after inhaling headspace above a menthol solution (menthol vapor) or headspace above the mineral oil solvent (control). Experiment 3 examined the impact of rinsing the mouth with a (bitter) sucrose octaacetate solution. Rinsing with sucrose and inhaling menthol vapor significantly increased measured cough thresholds. Rinsing with sucrose octaacete caused a non-significant decrease in cough thresholds, an important demonstration of specificity. Decreases in cough reflex sensitivity from sucrose or menthol could help explain why cough syrups without pharmacologically active ingredients are often almost as effective as formulations with an added drug. Further, the results support the idea that adding menthol to cigarettes might make tobacco smoke more tolerable for beginning smokers, at least in part, by reducing the sensitivity of an important airway defense mechanism. PMID:22465565

  4. Sweet Taste and Menthol Increase Cough Reflex Thresholds

    PubMed Central

    Wise, Paul M.; Breslin, Paul A.S.; Dalton, Pamela

    2015-01-01

    Cough is a vital protective reflex that is triggered by both mechanical and chemical stimuli. The current experiments explored how chemosensory stimuli modulate this important reflex. Cough thresholds were measured using a single-inhalation capsaicin challenge. Experiment 1 examined the impact of sweet taste: Cough thresholds were measured after rinsing the mouth with a sucrose solution (sweet) or with water (control). Experiment 2 examined the impact of menthol: Cough thresholds were measured after inhaling headspace above a menthol solution (menthol vapor) or headspace above the mineral oil solvent (control). Experiment 3 examined the impact of rinsing the mouth with a (bitter) sucrose octaacetate solution. Rinsing with sucrose and inhaling menthol vapor significantly increased measured cough thresholds. Rinsing with sucrose octaacete caused a non-significant decrease in cough thresholds, an important demonstration of specificity. Decreases in cough reflex sensitivity from sucrose or menthol could help explain why cough syrups without pharmacologically active ingredients are often almost as effective as formulations with an added drug. Further, the results support the idea that adding menthol to cigarettes might make tobacco smoke more tolerable for beginning smokers, at least in part, by reducing the sensitivity of an important airway defense mechanism. PMID:22465565

  5. Can Treadmill Perturbations Evoke Stretch Reflexes in the Calf Muscles?

    PubMed Central

    Sloot, Lizeth H.; van den Noort, Josien C.; van der Krogt, Marjolein M.; Bruijn, Sjoerd M.; Harlaar, Jaap

    2015-01-01

    Disinhibition of reflexes is a problem amongst spastic patients, for it limits a smooth and efficient execution of motor functions during gait. Treadmill belt accelerations may potentially be used to measure reflexes during walking, i.e. by dorsal flexing the ankle and stretching the calf muscles, while decelerations show the modulation of reflexes during a reduction of sensory feedback. The aim of the current study was to examine if belt accelerations and decelerations of different intensities applied during the stance phase of treadmill walking can evoke reflexes in the gastrocnemius, soleus and tibialis anterior in healthy subjects. Muscle electromyography and joint kinematics were measured in 10 subjects. To determine whether stretch reflexes occurred, we assessed modelled musculo-tendon length and stretch velocity, the amount of muscle activity, as well as the incidence of bursts or depressions in muscle activity with their time delays, and co-contraction between agonist and antagonist muscle. Although the effect on the ankle angle was small with 2.8±1.0°, the perturbations caused clear changes in muscle length and stretch velocity relative to unperturbed walking. Stretched muscles showed an increasing incidence of bursts in muscle activity, which occurred after a reasonable electrophysiological time delay (163–191 ms). Their amplitude was related to the muscle stretch velocity and not related to co-contraction of the antagonist muscle. These effects increased with perturbation intensity. Shortened muscles showed opposite effects, with a depression in muscle activity of the calf muscles. The perturbations only slightly affected the spatio-temporal parameters, indicating that normal walking was retained. Thus, our findings showed that treadmill perturbations can evoke reflexes in the calf muscles and tibialis anterior. This comprehensive study could form the basis for clinical implementation of treadmill perturbations to functionally measure reflexes during

  6. The role of stretch reflex threshold regulation in normal and impaired motor control.

    PubMed

    Levin, M F; Feldman, A G

    1994-09-19

    Some hypotheses suggest that stretch reflex threshold regulation may be an essential element of motor control. Disturbances in this mechanism may lead to motor dysfunction. We investigated this possibility by comparing stretch reflex threshold regulation in 11 spastic hemiparetic and 6 normal subjects. Subjects sat with their arms fully supported in a forearm and hand mold attached to a manipulandum mounted on and controlled by a torque motor. They remained completely passive while their elbow was extended from 30 degrees flexion through an arc of 100 degrees. Displacement and velocity of the forearm were measured as well as EMG signals from 2 elbow flexors and 2 elbow extensors, when the elbow flexors were stretched at each of 7 velocities. Velocities ranged from 8 to 160 degrees/s for hemiparetic subjects and from 32 to 300 degrees/s for normal subjects. Phase diagrams (velocity versus angle) were plotted and the threshold angles (lambda) for muscle activation at each velocity of stretch were used to determine the static stretch reflex threshold (lambda) and the slope (mu) of the relationship between the lambda s and velocity. Our main findings were that static and dynamic stretch reflex thresholds were decreased in spastic hemiparetic compared to normal subjects and that the thresholds depended on velocity. The static threshold value correlated with the severity of clinically measured spasticity. In addition, the range of regulation of lambda was decreased in the patients compared to normal. This may explain some of the problems of force and position regulation as well as hypertonus (and weakness) common to these patients. PMID:7820623

  7. The Effect of the 226-Hz Probe Level on Contralateral Acoustic Stapedius Reflex Thresholds

    ERIC Educational Resources Information Center

    Day, Jessica E.; Feeney, M. Patrick

    2008-01-01

    Purpose: The purpose of this study was to examine the effect of the 226-Hz probe level on the acoustic stapedius reflex threshold. Method: Contralateral reflex thresholds for a 1000-Hz pure-tone stimulus were obtained from 40 young adults with normal hearing using an experimental system at four 226-Hz probe levels (70, 75, 80, and 85 dB SPL) with…

  8. Auditory Brainstem Circuits That Mediate the Middle Ear Muscle Reflex

    PubMed Central

    Mukerji, Sudeep; Windsor, Alanna Marie; Lee, Daniel J.

    2010-01-01

    The middle ear muscle (MEM) reflex is one of two major descending systems to the auditory periphery. There are two middle ear muscles (MEMs): the stapedius and the tensor tympani. In man, the stapedius contracts in response to intense low frequency acoustic stimuli, exerting forces perpendicular to the stapes superstructure, increasing middle ear impedance and attenuating the intensity of sound energy reaching the inner ear (cochlea). The tensor tympani is believed to contract in response to self-generated noise (chewing, swallowing) and nonauditory stimuli. The MEM reflex pathways begin with sound presented to the ear. Transduction of sound occurs in the cochlea, resulting in an action potential that is transmitted along the auditory nerve to the cochlear nucleus in the brainstem (the first relay station for all ascending sound information originating in the ear). Unknown interneurons in the ventral cochlear nucleus project either directly or indirectly to MEM motoneurons located elsewhere in the brainstem. Motoneurons provide efferent innervation to the MEMs. Although the ascending and descending limbs of these reflex pathways have been well characterized, the identity of the reflex interneurons is not known, as are the source of modulatory inputs to these pathways. The aim of this article is to (a) provide an overview of MEM reflex anatomy and physiology, (b) present new data on MEM reflex anatomy and physiology from our laboratory and others, and (c) describe the clinical implications of our research. PMID:20870664

  9. Rhythmic arm cycling differentially modulates stretch and H-reflex amplitudes in soleus muscle.

    PubMed

    Palomino, Andres F; Hundza, Sandra R; Zehr, E Paul

    2011-10-01

    During rhythmic arm cycling, soleus H-reflex amplitudes are reduced by modulation of group Ia presynaptic inhibition. This suppression of reflex amplitude is graded to the frequency of arm cycling with a threshold of 0.8 Hz. Despite the data on modulation of the soleus H-reflex amplitude induced by rhythmic arm cycling, comparatively little is known about the modulation of stretch reflexes due to remote limb movement. Therefore, the present study was intended to explore the effect of arm cycling on stretch and H-reflex amplitudes in the soleus muscle. In so doing, additional information on the mechanism of action during rhythmic arm cycling would be revealed. Although both reflexes share the same afferent pathway, we hypothesized that stretch reflex amplitudes would be less suppressed by arm cycling because they are less inhibited by presynaptic inhibition. Failure to reject this hypothesis would add additional strength to the argument that Ia presynaptic inhibition is the mechanism modulating soleus H-reflex amplitude during rhythmic arm cycling. Participants were seated in a customized chair with feet strapped to footplates. Three motor tasks were performed: static control trials and arm cycling at 1 and 2 Hz. Soleus H-reflexes were evoked using single 1 ms pulses of electrical stimulation delivered to the tibial nerve at the popliteal fossa. A constant M-wave and ~6% MVC activation of soleus were maintained across conditions. Stretch reflexes were evoked using a single sinusoidal pulse at 100 Hz given by a vibratory shaker placed over the triceps surae tendon and controlled by a custom-written LabView program. Results demonstrated that rhythmic arm cycling that was effective for conditioning soleus H-reflexes did not show a suppressive effect on the amplitude of the soleus stretch reflex. We suggest this indicates that stretch reflexes are less sensitive to conditioning by rhythmic arm movement, as compared to H-reflexes, due to the relative insensitivity to

  10. The muscle engram: the reflex that limits conventional occlusal treatment.

    PubMed

    Lerman, Martin D

    2011-10-01

    The engram (the masticatory "muscle memory") is shown to be a conditionable reflex whose muscle conditioning lasts less than two minutes, far shorter than previously thought. This reflex, reinforced and stored in the masticatory muscles at every swallow, adjusts masticatory muscle activity to guide the lower arch unerringly into its ICP. These muscle adjustments compensate for the continually changing intemal and external factors that affect the mandible's entry into the ICP. A simple quick experiment described in this article isolates the engram, enabling the reader to see its action clearly for the first time. It is urged that every reader perform this experiment. This experiment shows how the engram, by hiding the masticatory muscles' reaction (the hit-and-slide), limits the success of the therapist in achieving occlusion-muscle compatibility. This finding has major clinical implications. It means that, as regards the muscle aspect of treating occlusion, the dentist treating occlusion conventionally is working blind, a situation the neuromuscular school of occlusal thought seeks to correct. The controversy over occlusion continues. PMID:22128670

  11. The middle ear muscle reflex in the diagnosis of cochlear neuropathy.

    PubMed

    Valero, Michelle D; Hancock, Kenneth E; Liberman, M Charles

    2016-02-01

    Cochlear neuropathy, i.e. the loss of auditory nerve fibers (ANFs) without loss of hair cells, may cause hearing deficits without affecting threshold sensitivity, particularly if the subset of ANFs with high thresholds and low spontaneous rates (SRs) is preferentially lost, as appears to be the case in both aging and noise-damaged cochleas. Because low-SR fibers may also be important drivers of the medial olivocochlear reflex (MOCR) and middle-ear muscle reflex (MEMR), these reflexes might be sensitive metrics of cochlear neuropathy. To test this hypothesis, we measured reflex strength and reflex threshold in mice with noise-induced neuropathy, as documented by confocal analysis of immunostained cochlear whole-mounts. To assay the MOCR, we measured contra-noise modulation of ipsilateral distortion-product otoacoustic emissions (DPOAEs) before and after the administration of curare to block the MEMR or curare + strychnine to also block the MOCR. The modulation of DPOAEs was 1) dominated by the MEMR in anesthetized mice, with a smaller contribution from the MOCR, and 2) significantly attenuated in neuropathic mice, but only when the MEMR was intact. We then measured MEMR growth functions by monitoring contra-noise induced changes in the wideband reflectance of chirps presented to the ipsilateral ear. We found 1) that the changes in wideband reflectance were mediated by the MEMR alone, and 2) that MEMR threshold was elevated and its maximum amplitude was attenuated in neuropathic mice. These data suggest that the MEMR may be valuable in the early detection of cochlear neuropathy. PMID:26657094

  12. Direct and reflex responses in perineal muscles on electrical stimulation.

    PubMed Central

    Vodusek, D B; Janko, M; Lokar, J

    1983-01-01

    Responses in the external anal and urethral sphincters as well as in the bulbocavernosus muscle have been evoked by supramaximal electrical stimulation of the penis (or clitoris), perineum and the peri-anal region and recorded electromyographically in 82 male subjects 5 to 73 years old and in nine female subjects 18 to 55 years old, who had no systemic diseases or demonstrable sacral nervous system lesion. On perineal stimulation (including the penis or clitoris) reflex responses with a typical latency of 33 ms and which exhibit no habituation were obtained in all muscles examined. Stimulation of the peri-anal region gave habituating reflex responses with a typical latency of 55 ms in all muscles examined. On perineal, and sometimes also peri-anal stimulation, stable short latency responses with typical latencies of 5 and 13 ms were recorded; both were considered to be direct responses. The different evoked muscle responses obtained by stimulation in the perineal and peri-anal region have to be distinguished when the bulbocavernosus and anal reflexes are recorded for evaluation of sacral nervous system lesions. PMID:6842203

  13. Muscle reflex in heart failure: the role of exercise training

    PubMed Central

    Wang, Han-Jun; Zucker, Irving H.; Wang, Wei

    2012-01-01

    Exercise evokes sympathetic activation and increases blood pressure and heart rate (HR). Two neural mechanisms that cause the exercise-induced increase in sympathetic discharge are central command and the exercise pressor reflex (EPR). The former suggests that a volitional signal emanating from central motor areas leads to increased sympathetic activation during exercise. The latter is a reflex originating in skeletal muscle which contributes significantly to the regulation of the cardiovascular and respiratory systems during exercise. The afferent arm of this reflex is composed of metabolically sensitive (predominantly group IV, C-fibers) and mechanically sensitive (predominately group III, A-delta fibers) afferent fibers. Activation of these receptors and their associated afferent fibers reflexively adjusts sympathetic and parasympathetic nerve activity during exercise. In heart failure, the sympathetic activation during exercise is exaggerated, which potentially increases cardiovascular risk and contributes to exercise intolerance during physical activity in chronic heart failure (CHF) patients. A therapeutic strategy for preventing or slowing the progression of the exaggerated EPR may be of benefit in CHF patients. Long-term exercise training (ExT), as a non-pharmacological treatment for CHF increases exercise capacity, reduces sympatho-excitation and improves cardiovascular function in CHF animals and patients. In this review, we will discuss the effects of ExT and the mechanisms that contribute to the exaggerated EPR in the CHF state. PMID:23060821

  14. Co-contraction modifies the stretch reflex elicited in muscles shortened by a joint perturbation

    PubMed Central

    Lewis, Gwyn N.; MacKinnon, Colum D.; Trumbower, Randy; Perreault, Eric J.

    2011-01-01

    Simultaneous contraction of agonist and antagonist muscles acting about a joint influences joint stiffness and stability. Although several studies have shown that reflexes in the muscle lengthened by a joint perturbation are modulated during co-contraction, little attention has been given to reflex regulation in the antagonist (shortened) muscle. The goal of the present study was to determine whether co-contraction gives rise to altered reflex regulation across the joint by examining reflexes in the muscle shortened by a joint perturbation. Reflexes were recorded from electromyographic activity in elbow flexors and extensors while positional perturbations to the elbow joint were applied. Perturbations were delivered during isolated activation of the flexor or extensor muscles as well as during flexor and extensor co-contraction. Across the group, the shortening reflex in the elbow extensor switched from suppression during isolated extensor muscle activation to facilitation during co-contraction. The shortening reflex in the elbow flexor remained suppressive during co-contraction but was significantly smaller compared to the response obtained during isolated elbow flexor activation. This response in the shortened muscle was graded by the level of activation in the lengthened muscle. The lengthening reflex did not change during co-contraction. These results support the idea that reflexes are regulated across multiple muscles around a joint. We speculate that the facilitatory response in the shortened muscle arises through a fast-conducting oligosynaptic pathway involving Ib interneurons. PMID:20878148

  15. Effects of digoxin on muscle reflexes in normal humans.

    PubMed

    Janssen, Christophe; Lheureux, Olivier; Beloka, Sofia; Adamopoulos, Dionysios; Naeije, Robert; van de Borne, Philippe

    2009-11-01

    Blockade of the skeletal muscle Na(+)-K(+)-ATPase pump by digoxin could result in a more marked hyperkaliema during a forearm exercise, which in turn could stimulate the mechano- and metaboreceptors. In a randomized, double-blinded, placebo-controlled, and cross-over-design study, we measured mean blood pressure (MBP), heart rate (HR), ventilation (V(E)), oxygen saturation (SpO(2)), muscle sympathetic nerve activity (MSNA), venous plasma potassium and lactic acid during dynamic handgrip exercises, and local circulatory arrest in 11 healthy subjects. Digoxin enhanced MBP during exercise but not during the post-handgrip ischemia and had no effect on HR, V(E), SpO(2), and MSNA. Venous plasma potassium and lactic acid were also not affected by digoxin-induced skeletal muscle Na(+)-K(+)-ATPase blockade. We conclude that digoxin increased MBP during dynamic exercise in healthy humans, independently of changes in potassium and lactic acid. A modest direct sensitization of the muscle mechanoreceptors is unlikely and other mechanisms, independent of muscle reflexes and related to the inotropic effects of digoxin, might be implicated. PMID:19701647

  16. The Hoffmann reflex of the soleus muscle. A study in leprosy.

    PubMed

    Sebille, A

    1980-03-01

    The H reflex of the soleus muscle was used to investigate the monosynaptic reflex arc of two groups of leprosy patients compared with a similar group of normal subjects. The H reflex recordings show two abnormalities: (1) An increase in the latency of the reflex without difference between lepromatous and borderline patients. (2) A decrease of the Hmax:Mmax amplitude ratio more pronounced in the lepromatous group. The discrepancy between these results and the commonly described preservation of the deep tendon reflexes in leprosy is discussed and the hypothesis that leprosy neuropathy would affect all nerve trunks related to blood vessel changes in suggested. PMID:7365508

  17. Effects of muscle history on the stretch reflex in cat and man.

    PubMed Central

    Gregory, J E; Mark, R F; Morgan, D L; Patak, A; Polus, B; Proske, U

    1990-01-01

    1. This is a report of experiments on cat and man which demonstrate effects of a muscle's previous history of contraction and length changes on the size of the stretch reflex. 2. In adult human subjects the size of the tendon jerk was measured in ankle extensor muscles by tapping the Achilles tendon. Muscle conditioning consisted of a maximum voluntary contraction with the foot dorsiflexed or plantarflexed by 30 deg from the test position, after which the subject was asked to relax while the foot was held still for several seconds before being returned to the test position and a tendon tap given. After a contraction of the lengthened muscle the tendon jerk was smaller than after a contraction of the shortened muscle. 3. The experiment was then repeated, but instead of a tendon jerk an H (Hoffmann) reflex was elicited by transcutaneous electrical stimulation of the tibial nerve in the popliteal fossa. The reflex after a conditioning contraction of the lengthened muscle was larger than after a contraction of the shortened muscle. In other words muscle conditioning produced opposite effects on the tendon jerk and H reflex. 4. These findings were confirmed in cats anaesthetized with chloralose. After a conditioning contraction of triceps surae at a length 5 mm longer than the test length (hold-long) a quick tendon stretch produced a smaller reflex response than following a conditioning contraction with the muscle 5 mm shorter than the test length (hold-short). The reverse trend was seen with a reflex elicited by direct electrical stimulation of the muscle nerve, which stimulates the H reflex. 5. One consequence of a conditioning contraction is that it leads to an alteration of the level of resting discharge of muscle spindles. We propose that the larger tendon jerk after a contraction of the shortened muscle is the result of changes in stretch sensitivity of muscle spindles. The reverse effect on the H reflex we attribute to a rise in the level of resting discharge of

  18. Dynamic control of muscle stiffness and H reflex modulation during hopping and jumping in man.

    PubMed Central

    Dyhre-Poulsen, P; Simonsen, E B; Voigt, M

    1991-01-01

    1. The objective of the study was to evaluate the functional effects of reflexes on muscle mechanics during natural voluntary movements. The excitability of the H (Hoffmann) reflex was used as a measure of the excitability of the central component of the stretch reflex. 2. We recorded EMG, ground reaction forces and the H reflex in the soleus muscle in humans while landing from a downward jump, during drop jumping and during hopping. The movements were also recorded by high-speed cinematography. 3. The EMG pattern was adapted to the motor task. When landing the EMG in the soleus muscle and in the anterior tibial muscle showed preinnervation and alternating activity after touch down. When hopping there was little preinnervation in the soleus muscle, and the activity was initiated about 45 ms after touch down by a peak and continued unbroken until lift off. In the drop jumps the EMG pattern depended on the jumping style used by the subject. 4. The H reflex in the soleus muscle was strongly modulated in a manner appropriate to the requirements of the motor task. During landing from a downward jump the H reflex was low at touch down whereas while hopping it was high at touch down. During drop jumping it was variable and influenced by the jumping technique. 5. Muscle stiffness in the ankle joint was negative after touch down when landing, but always positive when hopping. 6. It is suggested that during landing the alternating EMG pattern after touch down was programmed and little influenced by reflexes. During hopping reflexes could contribute to the initial peak and the EMG during lift off. 7. The programmed EMG activity and the suppression of the H reflex while landing probably contribute to the development of the negative stiffness and change the muscles from a spring to a damping unit. PMID:1890636

  19. Reflexes in cat ankle muscles after landing from falls.

    PubMed Central

    Prochazka, A; Schofield, P; Westerman, R A; Ziccone, S P

    1977-01-01

    1. Electrical activity and length of ankle muscles were recorded by telemetry during free fall and landing in cats. 2. After foot contact, there was a delay in onset of stretch of ankle extensors of between 8 and 11 ms. High-speed cinematography showed the delay to be associated with rapid initial dorsiflexion of the toes. 3. Electromyograms (e.m.g.) from lateral gastrocnemius increased in amplitude prior to landing. An early depression of lateral gastrocnemius e.m.g. commenced at 8 ms after foot contact, and was followed by a large peak of activity commencing some 8 ms after the first increase in lateral gastrocnemius length. 4. Local anaesthesia of the plantar cushion did not alter this pattern of response. 5. The early inhibition of lateral gastrocnemius was attributed to the action on lateral gastrocnemius motoneurones of non-cutaneous afferents responding to the initial toe dorsiflexion. Additional autogenetic inhibition may also have contributed. 6. The subsequent peak of e.m.g. was at a latenty consistent with a rapid stretch reflex, and occurred soon enough for the resulting active tension to contribute significantly to the extensor force during body deceleration. PMID:592210

  20. Simultaneous Measurement of Noise-Activated Middle-Ear Muscle Reflex and Stimulus Frequency Otoacoustic Emissions

    PubMed Central

    Keefe, Douglas H.

    2006-01-01

    Otoacoustic emissions serve as a noninvasive probe of the medial olivocochlear (MOC) reflex. Stimulus frequency otoacoustic emissions (SFOAEs) elicited by a low-level probe tone may be the optimal type of emission for studying MOC effects because at low levels, the probe itself does not elicit the MOC reflex [Guinan et al. (2003) J. Assoc. Res. Otolaryngol. 4:521]. Based on anatomical considerations, the MOC reflex activated by ipsilateral acoustic stimulation (mediated by the crossed olivocochlear bundle) is predicted to be stronger than the reflex to contralateral stimulation. Broadband noise is an effective activator of the MOC reflex; however, it is also an effective activator of the middle-ear muscle (MEM) reflex, which can make results difficult to interpret. The MEM reflex may be activated at lower levels than measured clinically, and most previous human studies have not explicitly included measurements to rule out MEM reflex contamination. The current study addressed these issues using a higher-frequency SFOAE probe tone to test for cochlear changes mediated by the MOC reflex, while simultaneously monitoring the MEM reflex using a low-frequency probe tone. Broadband notched noise was presented ipsilaterally at various levels to elicit probe-tone shifts. Measurements are reported for 15 normal-hearing subjects. With the higher-frequency probe near 1.5 kHz, only 20% of subjects showed shifts consistent with an MOC reflex in the absence of an MEM-induced shift. With the higher-frequency probe near 3.5 kHz, up to 40% of subjects showed shifts in the absence of an MEM-induced shift. However, these responses had longer time courses than expected for MOC-induced shifts, and may have been dominated by other cochlear processes, rather than MOC reflex. These results suggest caution in the interpretation of effects observed using ipsilaterally presented acoustic activators intended to excite the MOC reflex. PMID:16568366

  1. A novel approach using tendon vibration of the human flexor carpi radialis muscle to study spinal reflexes.

    PubMed

    Tsang, Kenneth; de Bruin, Hubert; Archambeault, Mark

    2008-01-01

    Although most muscle spindle investigations have used the cat model and invasive measurement techniques, several investigators have used microneurography to record from the Ia and II fibres in humans during tendon vibration. In these studies the muscle spindle primary endings are stimulated using transverse vibration of the tendon at reflex sub-threshold amplitudes. Others have used low amplitude vibration and the stretch evoked M-wave response to determine reflex properties during both agonist and antagonist voluntary contractions. In the past we have developed a PC based instrument that uses Labview and a linear servomotor to study tendon reflex properties by recording stretch evoked M-wave responses from single tendon taps or electrical stimuli to the afferent nerve. In this paper we describe a further development of this system to provide precise vibrations of the tendon up to 65 Hz with amplitudes up to 4 mm. The resultant M-wave train is extracted from background noise via phase coherent subtractive filtering. Test results from vibrating the human distal flexor carpi radialis tendon at 10 and 30 Hz, for relaxed, slight flexion and slight extension, are also presented. PMID:19163861

  2. Effects of postural threat on spinal stretch reflexes: evidence for increased muscle spindle sensitivity?

    PubMed

    Horslen, Brian C; Murnaghan, Chantelle D; Inglis, J Timothy; Chua, Romeo; Carpenter, Mark G

    2013-08-01

    Standing balance is often threatened in everyday life. These threats typically involve scenarios in which either the likelihood or the consequence of falling is higher than normal. When cats are placed in these scenarios they respond by increasing the sensitivity of muscle spindles imbedded in the leg muscles, presumably to increase balance-relevant afferent information available to the nervous system. At present, it is unknown whether humans also respond to such postural threats by altering muscle spindle sensitivity. Here we present two studies that probed the effects of postural threat on spinal stretch reflexes. In study 1 we manipulated the threat associated with an increased consequence of a fall by having subjects stand at the edge of an elevated surface (3.2 m). In study 2 we manipulated the threat by increasing the likelihood of a fall by occasionally tilting the support surface on which subjects stood. In both scenarios we used Hoffmann (H) and tendon stretch (T) reflexes to probe the spinal stretch reflex circuit of the soleus muscle. We observed increased T-reflex amplitudes and unchanged H-reflex amplitudes in both threat scenarios. These results suggest that the synaptic state of the spinal stretch reflex is unaffected by postural threat and that therefore the muscle spindles activated in the T-reflexes must be more sensitive in the threatening conditions. We propose that this increase in sensitivity may function to satisfy the conflicting needs to restrict movement with threat, while maintaining a certain amount of sensory information related to postural control. PMID:23719208

  3. Interaction between vestibulosympathetic and skeletal muscle reflexes on sympathetic activity in humans

    NASA Technical Reports Server (NTRS)

    Ray, C. A.

    2001-01-01

    Evidence from animals indicates that skeletal muscle afferents activate the vestibular nuclei and that both vestibular and skeletal muscle afferents have inputs to the ventrolateral medulla. The purpose of the present study was to investigate the interaction between the vestibulosympathetic and skeletal muscle reflexes on muscle sympathetic nerve activity (MSNA) and arterial pressure in humans. MSNA, arterial pressure, and heart rate were measured in 17 healthy subjects in the prone position during three experimental trials. The three trials were 2 min of 1) head-down rotation (HDR) to engage the vestibulosympathetic reflex, 2) isometric handgrip (IHG) at 30% maximal voluntary contraction to activate skeletal muscle afferents, and 3) HDR and IHG performed simultaneously. The order of the three trials was randomized. HDR and IHG performed alone increased total MSNA by 46 +/- 16 and 77 +/- 24 units, respectively (P < 0.01). During the HDR plus IHG trial, MSNA increased 142 +/- 38 units (P < 0.01). This increase was not significantly different from the sum of the individual trials (130 +/- 41 units). This finding was also observed with mean arterial pressure (sum = 21 +/- 2 mmHg and HDR + IHG = 22 +/- 2 mmHg). These findings suggest that there is an additive interaction for MSNA and arterial pressure when the vestibulosympathetic and skeletal muscle reflexes are engaged simultaneously in humans. Therefore, no central modulation exists between these two reflexes with regard to MSNA output in humans.

  4. Muscle and reflex changes with varying joint angle in hemiparetic stroke

    PubMed Central

    Mirbagheri, Mehdi M; Alibiglou, Laila; Thajchayapong, Montakan; Rymer, William Z

    2008-01-01

    Background Despite intensive investigation, the origins of the neuromuscular abnormalities associated with spasticity are not well understood. In particular, the mechanical properties induced by stretch reflex activity have been especially difficult to study because of a lack of accurate tools separating reflex torque from torque generated by musculo-tendinous structures. The present study addresses this deficit by characterizing the contribution of neural and muscular components to the abnormally high stiffness of the spastic joint. Methods Using system identification techniques, we characterized the neuromuscular abnormalities associated with spasticity of ankle muscles in chronic hemiparetic stroke survivors. In particular, we systematically tracked changes in muscle mechanical properties and in stretch reflex activity during changes in ankle joint angle. Modulation of mechanical properties was assessed by applying perturbations at different initial angles, over the entire range of motion (ROM). Experiments were performed on both paretic and non-paretic sides of stroke survivors, and in healthy controls. Results Both reflex and intrinsic muscle stiffnesses were significantly greater in the spastic/paretic ankle than on the non-paretic side, and these changes were strongly position dependent. The major reflex contributions were observed over the central portion of the angular range, while the intrinsic contributions were most pronounced with the ankle in the dorsiflexed position. Conclusion In spastic ankle muscles, the abnormalities in intrinsic and reflex components of joint torque varied systematically with changing position over the full angular range of motion, indicating that clinical perceptions of increased tone may have quite different origins depending upon the angle where the tests are initiated. Furthermore, reflex stiffness was considerably larger in the non-paretic limb of stroke patients than in healthy control subjects, suggesting that the non

  5. Trigeminal Proprioception Evoked by Strong Stretching of the Mechanoreceptors in Müller's Muscle Induces Reflex Contraction of the Orbital Orbicularis Oculi Slow-Twitch Muscle Fibers

    PubMed Central

    Ban, Ryokuya; Ban, Midori; Yuzuriha, Shunsuke

    2014-01-01

    Objective: The mixed orbicularis oculi muscle lacks an intramuscular proprioceptive system such as muscle spindles, to induce reflex contraction of its slow-twitch fibers. We evaluated whether the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction of the slow-twitch fibers of the orbicularis oculi in addition to those of the levator and frontalis muscles. Methods: We evaluated in patients with aponeurosis-disinserted blepharoptosis whether strong stretching of the mechanoreceptors in Müller's muscle from upgaze with unilateral lid load induced reflex contraction of the orbicularis oculi slow-twitch fibers and whether anesthesia of Müller's muscle precluded the contraction. We compared the electromyographic responses of the bilateral orbicularis oculi muscles to unilateral intraoperative direct stimulation of the trigeminal proprioceptive nerve with those to unilateral transcutaneous electrical stimulation of the supraorbital nerve. Results: Upgaze with a unilateral 3-g lid load induced reflex contraction of the bilateral orbicularis oculi muscles with ipsilateral dominance. Anesthesia of Müller's muscle precluded the reflex contraction. The orbicularis oculi reflex evoked by stimulation of the trigeminal proprioceptive nerve differed from that by electrical stimulation of the supraorbital nerve in terms of the intensity of current required to induce the reflex, the absence of R1, and duration. Conclusions: The mechanoreceptors in Müller's muscle functions as an extramuscular proprioceptive system to induce reflex contraction of the orbital orbicularis oculi slow-twitch fibers. Whereas reflex contraction of the pretarsal orbicularis fast-twitch fibers functions in spontaneous or reflex blinking, that of the orbital orbicularis oculi slow-twitch fibers may factor in grimacing and blepharospasm. PMID:25210572

  6. [Effect of sydnophen and caffeine on reflex shifts in arterial pressure arising during skeletal muscle contraction].

    PubMed

    Medvedev, O S; Stepochkina, N A

    1977-01-01

    The influence of sydnophen (5-20 mg/kg) and of caffein (10-40 mg/kg) on the pressor reaction of the arterial pressure, provoked by contraction of skeletal muscles following stimulation of the anterior spinal cord roots (L6, L7, S1) was investigated in 17 tests set up on decerebrated non-narcotized cats. The intraveonus injection of sydnophen was attended by a fall of the arterial pressure and inhibition of the pressor reflex. Caffein reduced the intensity of the pressor reflex to a lesser extent and did not modify the initial level of the arterial pressure. PMID:852546

  7. Muscle afferent potential (`A-wave') in the surface electromyogram of a phasic stretch reflex in normal humans

    PubMed Central

    Clarke, Alex. M.; Michie, Patricia T.; Glue, Leonard C. T.

    1972-01-01

    The experiments reported in this paper tested the hypothesis that the afferent potential elicited by a tendon tap in an isometrically recorded phasic stretch reflex can be detected in the surface EMG of normal humans when appropriate techniques are used. These techniques involved (1) training the subjects to relax mentally and physically so that the EMG was silent before and immediately after the diphasic MAP which reflects a highly synchronous discharge of afferent impulses from low threshold muscle stretch receptors after a tendon tap, and (2) using a data retrieval computer to summate stimulus-locked potentials in the EMG over a series of 16 samples using taps of uniform peak force and duration on the Achilles tendon to elicit the tendon jerk in the calf muscles. A discrete, diphasic potential (`A-wave') was recorded from EMG electrodes placed on the surface of the skin over the medial gastrocnemius muscle. The `A-wave' afferent potential had the opposite polarity to the corresponding efferent MAP. Under control conditions of relaxation the `A-wave' had a latency after the onset of the tap of 2 msec, the peak to peak amplitude was of the order of 5 μV and the duration was in the range of 6 to 10 msec. Further experiments were conducted to show that the `A-wave' (1) was not an artefact of the instrumentation used, (2) had a threshold at low intensities of stimulation, and (3) could be reliably augmented by using a Jendrassik manoeuvre compared with the potential observed during control (relaxation) conditions. The results support the conclusion that the `A-wave' emanates from the pool of muscle spindles which discharges impulses along group Ia nerve fibres in response to the phasic stretch stimulus because the primary ending of the spindles is known to initiate the stretch reflex and the spindles can be sensitized by fusimotor impulses so that their threshold is lowered as a result of a Jendrassik manoeuvre. The finding has important implications for the

  8. Trunk muscle activation during golf swing: Baseline and threshold.

    PubMed

    Silva, Luís; Marta, Sérgio; Vaz, João; Fernandes, Orlando; Castro, Maria António; Pezarat-Correia, Pedro

    2013-10-01

    There is a lack of studies regarding EMG temporal analysis during dynamic and complex motor tasks, such as golf swing. The aim of this study is to analyze the EMG onset during the golf swing, by comparing two different threshold methods. Method A threshold was determined using the baseline activity recorded between two maximum voluntary contraction (MVC). Method B threshold was calculated using the mean EMG activity for 1000ms before the 500ms prior to the start of the Backswing. Two different clubs were also studied. Three-way repeated measures ANOVA was used to compare methods, muscles and clubs. Two-way mixed Intraclass Correlation Coefficient (ICC) with absolute agreement was used to determine the methods reliability. Club type usage showed no influence in onset detection. Rectus abdominis (RA) showed the higher agreement between methods. Erector spinae (ES), on the other hand, showed a very low agreement, that might be related to postural activity before the swing. External oblique (EO) is the first being activated, at 1295ms prior impact. There is a similar activation time between right and left muscles sides, although the right EO showed better agreement between methods than left side. Therefore, the algorithms usage is task- and muscle-dependent. PMID:23816264

  9. Activity of latissimus dorsi muscle during inspiratory threshold loads.

    PubMed

    Orozco-Levi, M; Gea, J; Monells, J; Aran, X; Aguar, M C; Broquetas, J M

    1995-03-01

    The ability of the latissimus dorsi muscle (LD) to participate as an accessory inspiratory muscle has been the subject of controversy. Electromyographic (EGM) activity of LD was evaluated in 11 healthy subjects (aged 30 +/- 2 yrs; forced expiratory volume in one second (FEV1) 106 +/- 5% predicted; maximal inspiratory pressure (Pmax), 120 +/- 6 cmH2O) under different breathing conditions. The ipsilateral biceps brachii was chosen as the control muscle. The EMG was recorded from surface electrodes, but needle electrodes were also used for LD evaluation in a subset of three subjects. The EMG signal from both muscles was recorded simultaneously, rectified and integrated, with subtraction of the electrocardiographic signal. Situations evaluated were: 1) maximal voluntary contraction (MVC); 2) apnoea; and 3) breathing under progressive inspiratory threshold loads (20-100% Pmax, at 20% intervals). A close relationship was evident between LD recordings from surface and needle electrodes (r = 0.975). Activity of LD at baseline was 1.8 +/- 0.4% MVC, and showed a phasic increase during inspiration under loads. This change had a linear tendency and was significant for loads corresponding to 40, 60, 80 and 100% of Pmax when compared to the control muscle. At this latter level, LD activity was equivalent to 32 +/- 5% MVC (range 11-61%), whereas mean activity of the control muscle was less than 7.5% MVC.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7789491

  10. Intraoperative electrically elicited stapedius reflex threshold is related to the dosage of hypnotic drugs in general anesthesia.

    PubMed

    Schultz, Arthur; Berger, Frank Andreas; Weber, Benno Paul; Grouven, Ulrich; Niclaus, Oliver; Lüllwitz, Ekkehard; Schultz, Barbara

    2003-12-01

    Today cochlear implantation is a widely used means of treatment in deafness and severe hearing disorders in adults, children, and infants. Postoperative fitting of the externally worn speech processor is very important for successful use of the cochlear implant. However, especially in infants and young children, this fitting process can be difficult because of limited communication capabilities. The use of intraoperatively obtained stapedius reflex thresholds has been proposed for postoperative speech processor fitting, but the influence of anesthetics on threshold values needs to be taken into account. In a retrospective study with 20 patients between 3 and 43 years of age, a highly significant correlation between the dosage of methohexital and the mean stapedius reflex threshold value could be shown (r = 0.65, p = .002). We conclude that more reliable threshold values can be obtained by reducing the dosage of hypnotics to achieve a lighter level of hypnosis during stapedius reflex measurement. To achieve a light, but still sufficient level of hypnosis, electroencephalographic monitoring including automatic interpretation of the complex raw signal should be used. PMID:14703109

  11. Changes in H-reflex amplitude to muscle stretch and lengthening in humans.

    PubMed

    Budini, Francesco; Tilp, Markus

    2016-07-01

    Spinal reflex excitability is traditionally assessed to investigate neural adjustments that occur during human movement. Different experimental procedures are known to condition spinal reflex excitability. Among these, lengthening movements and static stretching the human triceps have been investigated over the last 50 years. The purpose of this review is to shed light on several apparent incongruities in terms of magnitude and duration of the reported results. In the present review dissimilarities in neuro-spinal changes are examined in relation to the methodologies applied to condition and measure them. Literature that investigated three different conditioning procedures was reviewed: passive dorsiflexion, active dorsiflexion through antagonists shortening and eccentric plantar-flexors contractions. Measurements were obtained before, during and after lengthening or stretching. Stimulation intensities and time delays between conditioning procedures and stimuli varied considerably. H-reflex decreases immediately as static stretching is applied and in proportion to the stretch degree. During dorsiflexions the inhibition is stronger with greater dorsiflexion angular velocity and at lower nerve stimulation intensities, while it is weaker if any concomitant muscle contraction is performed. Within 2 s after a single passive dorsiflexion movement, H-reflex is strongly inhibited, and this effect disappears within 15 s. Dorsiflexions repeated over 1 h and prolonged static stretching training induce long-lasting inhibition. This review highlights that the apparent disagreement between studies is ascribable to small methodological differences. Lengthening movements and stretching can strongly influence spinal neural pathways. Results interpretation, however, needs careful consideration of the methodology applied. PMID:27089411

  12. Task-dependent changes in cutaneous reflexes recorded from various muscles controlling finger movement in man.

    PubMed Central

    Evans, A L; Harrison, L M; Stephens, J A

    1989-01-01

    1. Cutaneous reflex responses have been recorded from muscles involved in the control of finger movement following electrical stimulation of the digital nerves of the fingers in man. 2. Recordings have been made while subjects performed various manual tasks. 3. Reflexes recorded while subjects performed a relatively isolated finger movement consisted of an initial short-latency increase in muscle electrical activity, followed by a decrease, followed by a prominent longer-latency increase. The long-latency excitatory component was smaller or absent during those grips used in the present study. 4. The short-latency excitatory (E1) and inhibitory (I1) components of the cutaneomuscular reflex response are mediated via spinal pathways. The second longer-latency excitatory component (E2) is of supraspinal origin, requiring the integrity of the dorsal columns, sensorimotor cortex and corticospinal tract (Jenner & Stephens, 1982). The results of the present study suggest that one or more of these supraspinal pathways is more active when a finger is used in a relatively isolated manner than when the same finger participates in any of the gripping manoeuvres used in the present experiments. PMID:2621613

  13. A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity

    PubMed Central

    Cidem, Muharrem; Karacan, İlhan; Diraçoğlu, Demirhan; Yıldız, Aysel; Küçük, Suat Hayri; Uludağ, Murat; Gün, Kerem; Özkaya, Murat; Karamehmetoğlu, Şafak Sahir

    2014-01-01

    Background: Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neurological mechanism used to explain the effects of vibration on muscular performance. Bone myoregulation reflex is defined as a reflex mechanism in which osteocytes exposed to cyclic mechanical loading induce muscle activity. Aims: The aim of this study was to assess whether bone tissue affected vibration-induced reflex muscle activity and vibration-induced muscle strength gain. Study Design: A prospective, randomised, controlled, double-blind, parallel-group clinical trial. Methods: Thirty-four participants were randomised into two groups. High-magnitude whole-body vibration was applied in the exercise group, whereas low-magnitude whole-body vibration exercises were applied in the control group throughout 20 sessions. Hip bone mineral density, isokinetic muscle strength, and plasma sclerostin levels were measured. The surface electromyography data were processed to obtain the Root Mean Squares, which were normalised by maximal voluntarily contraction. Results: In the exercise group, muscle strength increased in the right and left knee flexors (23.9%, p=0.004 and 27.5%, p<0.0001, respectively). However, no significant change was observed in the knee extensor muscle strength. There was no significant change in the knee muscle strength in the control group. The vibration-induced corrected Root Mean Squares of the semitendinosus muscle was decreased by 2.8 times (p=0.005) in the exercise group, whereas there was no change in the control group. Sclerostin index was decreased by 15

  14. Short-Term Plasticity in a Monosynaptic Reflex Pathway to Forearm Muscles after Continuous Robot-Assisted Passive Stepping.

    PubMed

    Nakajima, Tsuyoshi; Kamibayashi, Kiyotaka; Kitamura, Taku; Komiyama, Tomoyoshi; Zehr, E Paul; Nakazawa, Kimitaka

    2016-01-01

    Both active and passive rhythmic limb movements reduce the amplitude of spinal cord Hoffmann (H-) reflexes in muscles of moving and distant limbs. This could have clinical utility in remote modulation of the pathologically hyperactive reflexes found in spasticity after stroke or spinal cord injury. However, such clinical translation is currently hampered by a lack of critical information regarding the minimum or effective duration of passive movement needed for modulating spinal cord excitability. We therefore investigated the H-reflex modulation in the flexor carpi radialis (FCR) muscle during and after various durations (5, 10, 15, and 30 min) of passive stepping in 11 neurologically normal subjects. Passive stepping was performed by a robotic gait trainer system (Lokomat(®)) while a single pulse of electrical stimulation to the median nerve elicited H-reflexes in the FCR. The amplitude of the FCR H-reflex was significantly suppressed during passive stepping. Although 30 min of passive stepping was sufficient to elicit a persistent H-reflex suppression that lasted up to 15 min, 5 min of passive stepping was not. The duration of H-reflex suppression correlated with that of the stepping. These findings suggest that the accumulation of stepping-related afferent feedback from the leg plays a role in generating short-term interlimb plasticity in the circuitry of the FCR H-reflex. PMID:27499737

  15. Short-Term Plasticity in a Monosynaptic Reflex Pathway to Forearm Muscles after Continuous Robot-Assisted Passive Stepping

    PubMed Central

    Nakajima, Tsuyoshi; Kamibayashi, Kiyotaka; Kitamura, Taku; Komiyama, Tomoyoshi; Zehr, E. Paul; Nakazawa, Kimitaka

    2016-01-01

    Both active and passive rhythmic limb movements reduce the amplitude of spinal cord Hoffmann (H-) reflexes in muscles of moving and distant limbs. This could have clinical utility in remote modulation of the pathologically hyperactive reflexes found in spasticity after stroke or spinal cord injury. However, such clinical translation is currently hampered by a lack of critical information regarding the minimum or effective duration of passive movement needed for modulating spinal cord excitability. We therefore investigated the H-reflex modulation in the flexor carpi radialis (FCR) muscle during and after various durations (5, 10, 15, and 30 min) of passive stepping in 11 neurologically normal subjects. Passive stepping was performed by a robotic gait trainer system (Lokomat®) while a single pulse of electrical stimulation to the median nerve elicited H-reflexes in the FCR. The amplitude of the FCR H-reflex was significantly suppressed during passive stepping. Although 30 min of passive stepping was sufficient to elicit a persistent H-reflex suppression that lasted up to 15 min, 5 min of passive stepping was not. The duration of H-reflex suppression correlated with that of the stepping. These findings suggest that the accumulation of stepping-related afferent feedback from the leg plays a role in generating short-term interlimb plasticity in the circuitry of the FCR H-reflex. PMID:27499737

  16. Asymmetry in reflex responses of nasal muscles in anesthetized guinea pigs.

    PubMed

    Sekizawa, S I; Ishikawa, T; Sant'Ambrogio, G

    1998-07-01

    Nasal reflexes elicited by mechanical or electrical stimulation of nasal afferents were studied in anesthetized guinea pigs. Probing the nasal cavity of one side evoked a greater activation of the contralateral than the ipsilateral nasal muscles and, occasionally, sneezing. Similarly, electrical stimulation of the ethmoidal nerve often caused sneezing, with a greater activation of the nasal muscles and a greater increase in resistance on the contralateral side. Asymmetrical activation of the nasal muscles in response to mechanical stimuli induces asymmetrical airflows, especially during sneezing, between the two sides of the nasal cavity. Most of the expired air is forcibly blown out through the ipsilateral nostril, thus improving the elimination of irritants from the nose. PMID:9655764

  17. Voluntary and reflex control of the biceps brachii muscle in spastic-athetotic patients

    PubMed Central

    Neilson, Peter D.

    1972-01-01

    A cross-correlation technique of analysis was used to measure the transmission characteristics of tonic stretch reflex (TSR) pathways in spastic-athetoid subjects sustaining a voluntary contraction in the biceps brachii muscle. A comparison was made with the transmission characteristics of normal subjects measured by the same technique. It was found that gain and phase characteristics of spastic patients did not display the large resonant peaks present in normals. It is proposed that the resonant peaks in the TSR transmission of normal subjects were caused by long loop pathways. The absence of these peaks in the spastic patients supports the hypothesis that short-circuiting of long loop pathways by hyperactive spinal reflexes is part of the mechanism of spasticity. PMID:4343479

  18. Electromyographic analysis of male rat perineal muscles during copulation and reflexive erections.

    PubMed

    Holmes, G M; Chapple, W D; Leipheimer, R E; Sachs, B D

    1991-06-01

    Anatomical examination of the ventral bulbospongiosus (BS) muscle suggested that its proximal and distal portions may act during penile erection as a two-stage pump governing the intensity of glans erections. The coordination between these portions of the BS, and of the proximal BS with the ischiocavernosus (IC) muscle, was studied using electromyographic (EMG) recordings taken during copulation and reflexive erections. Mounts without intromission were accompanied by either strong IC activity with little or no proximal BS activity, or strong proximal BS activity preceding the onset of IC activity. Activity in the proximal BS during mounts was variable in both duration and amplitude but uniform in frequency. During mounts with intromission, EMG activity of the proximal BS consisted of two characteristic phases, an early phase of low-amplitude activity which was similar to proximal BS activity during nonintromissive mounts, followed by an intromissive phase of high-amplitude, high-frequency activity. During intromission patterns, IC activity reliably preceded proximal BS activity. Ejaculations were accompanied by stronger proximal BS activity than were other copulatory events and were followed by a series of proximal BS and IC bursts lasting for 10-20 seconds. During reflexive erections, EMG activity in the proximal BS was always fusiform and varied with the intensity of erection only in frequency. In contrast to the proximal BS, activity in the distal BS was similar in frequency and amplitude across copulatory and reflexive events. These findings suggest that: a) different motoneuron pools serve the different portions of the BS muscle; b) the distal BS does not differentially affect glans erection but may serve primarily to promote rigidity of the portion of the bulb that it surrounds, while the proximal BS acts as the variable aspect of a hypothetical two-stage pump, and c) activity in the IC must precede activity in the proximal BS to achieve intromission. PMID

  19. The proprioceptive reflex control of the intercostal muscles during their voluntary activation

    PubMed Central

    Davis, J. Newsom; Sears, T. A.

    1970-01-01

    1. A quantitative study has been made of the reflex effects of sudden changes in mechanical load on contracting human intercostal muscles during willed breathing movements involving the chest wall. Averaging techniques were applied to recordings of electromyogram (EMG) and lung volume, and to other parameters of breathing. 2. Load changes were effected for brief periods (10-150 msec) at any predetermined lung volume by sudden connexion of the airway to a pressure source variable between ± 80 cm H2O so that respiratory movement could be either assisted or opposed. In some experiments airway resistance was suddenly reduced by porting from a high to a low resistance external airway. 3. Contracting inspiratory and expiratory intercostal muscles showed a `silent period' with unloading which is attributed to the sudden withdrawal from intercostal motoneurones of monosynaptic excitation of muscle spindle origin. 4. For both inspiratory and expiratory intercostal muscles the typical immediate effect of an increase in load was an inhibitory response (IR) with a latency of about 22 msec followed by an excitatory response (ER) with a latency of 50-60 msec. 5. It was established using brief duration stimuli (< 40 msec) that the IR depended on mechanical events associated with the onset of stimulation, whereas stimuli greater than 40 msec in duration were required to evoke the ER. 6. For constant expiratory flow rate and a constant load, the ER of expiratory intercostal muscles increased as lung volume decreased within the limits set by maximal activation of the motoneurone pool as residual volume was approached. 7. The ER to a constant load increased directly with the expiratory flow rate at which the load applied, also within limits set by maximal activation of the motoneurone pool. 8. For a given load, the ER during phonation was greater than that occurring at a similar expiratory flow rate without phonation when the resistance of the phonating larynx was mimicked by an

  20. Muscle Weakness Thresholds for Prediction of Diabetes in Adults

    PubMed Central

    Peterson, Mark D.; Zhang, Peng; Choksi, Palak; Markides, Kyriakos S.; Al Snih, Soham

    2016-01-01

    Background Despite the known links between weakness and early mortality, what remains to be fully understood is the extent to which strength preservation is associated with protection from cardiometabolic diseases such as diabetes. Purpose The purposes of this study were to determine the association between muscle strength and diabetes among adults, and to identify age- and sex-specific thresholds of low strength for detection of risk. Methods A population-representative sample of 4,066 individuals, aged 20–85 years, was included from the combined 2011–2012 National Health and Nutrition Examination Survey datasets. Strength was assessed using a hand-held dynamometer, and the single largest reading from either hand was normalized to body mass. A logistic regression model was used to assess the association between normalized grip strength and risk of diabetes, as determined by hemoglobin A1c (HbA1c) levels (≥6.5% [≥48 mmol/mol]), while controlling for sociodemographic characteristics, anthropometric measures, and television viewing time. Results For every 0.05 decrement in normalized strength, there was a 1.26 times increased adjusted odds for diabetes in men and women. Women were at lower odds of having diabetes (OR: 0.49; 95% CI: 0.29–0.82), whereas age, waist circumference and lower income were inversely associated. Optimal sex- and age-specific weakness thresholds to detect diabetes were 0.56, 0.50, and 0.45 for men, and 0.42, 0.38, and 0.33 for women, for ages 20–39 years, 40–59 years, and 60–80 years. Conclusions and Clinical Relevance We present thresholds of strength that can be incorporated into a clinical setting for identifying adults that are at risk for developing diabetes, and that might benefit from lifestyle interventions to reduce risk. PMID:26744337

  1. Limb segment vibration modulates spinal reflex excitability and muscle mRNA expression after spinal cord injury

    PubMed Central

    Chang, Shuo-Hsiu; Tseng, Shih-Chiao; McHenry, Colleen L.; Littmann, Andrew E.; Suneja, Manish; Shields, Richard K.

    2012-01-01

    Objective We investigated the effect of various doses of vertical oscillation (vibration) on soleus H-reflex amplitude and post-activation depression in individuals with and without SCI. We also explored the acute effect of short-term limb vibration on skeletal muscle mRNA expression of genes associated with spinal plasticity. Methods Six healthy adults and five chronic complete SCI subjects received vibratory stimulation of their tibia over three different gravitational accelerations (0.3g, 0.6g, and 1.2g) at a fixed frequency (30 Hz). Soleus H-reflexes were measured before, during, and after vibration. Two additional chronic complete SCI subjects had soleus muscle biopsies 3 h following a single bout of vibration. Results H-reflex amplitude was depressed over 83% in both groups during vibration. This vibratory-induced inhibition lasted over 2 min in the control group, but not in the SCI group. Post-activation depression was modulated during the long-lasting vibratory inhibition. A single bout of mechanical oscillation altered mRNA expression from selected genes associated with synaptic plasticity. Conclusions Vibration of the lower leg inhibits the H-reflex amplitude, influences post-activation depression, and alters skeletal muscle mRNA expression of genes associated with synaptic plasticity. Significance Limb segment vibration may offer a long term method to reduce spinal reflex excitability after SCI. PMID:21963319

  2. Effects of Exercise Induced Low Back Pain on Intrinsic Trunk Stiffness and Paraspinal Muscle Reflexes

    PubMed Central

    Miller, Emily M.; Bazrgari, Babak; Nussbaum, Maury A.; Madigan, Michael L.

    2012-01-01

    The purpose of this study was to 1) compare trunk neuromuscular behavior between individuals with no history of low back pain (LBP) and individuals who experience exercise-induced LBP (eiLBP) when pain free, and 2) investigate changes in trunk neuromuscular behavior with eiLBP. Seventeen young adult males participated including eight reporting recurrent, acute eiLBP and nine control participants reporting no history of LBP. Intrinsic trunk stiffness and paraspinal muscle reflex delay were determined in both groups using sudden trunk flexion position perturbations 1-2 days following exercise when the eiLBP participants were experiencing an episode of LBP (termed post-exercise) and 4-5 days following exercise when eiLBP had subsided (termed post-recovery). Post-recovery, when the eiLBP group was experiencing minimal LBP, trunk stiffness was 26% higher in the eiLBP group compared to the control group (p=0.033) and reflex delay was not different (p=0.969) between groups. Trunk stiffness did not change (p=0.826) within the eiLBP group from post-exercise to post-recovery, but decreased 22% within the control group (p=0.002). Reflex delay decreased 11% within the eiLBP group from post-exercise to post-recovery (p=0.013), and increased 15% within the control group (p=0.006). Although the neuromuscular mechanisms associated with eiLBP and chronic LBP may differ, these results suggest that previously-reported differences in trunk neuromuscular behavior between individuals with chronic LBP and healthy controls reflect a combination of inherent differences in neuromuscular behavior between these individuals as well as changes in neuromuscular behavior elicited by pain. PMID:23182221

  3. The effects of isometric resistance training on stretch reflex induced tremor in the knee extensor muscles.

    PubMed

    Durbaba, Rade; Cassidy, Angela; Budini, Francesco; Macaluso, Andrea

    2013-06-15

    This study examines the effect of 4 wk of high-intensity isometric resistance training on induced tremor in knee extensor muscles. Fourteen healthy volunteers were assigned to either the training group (n = 7) or the nontraining control group (n = 7). Induced tremor was assessed by measuring force fluctuations during anisometric contractions against spring loading, whose compliance was varied to allow for preferential activation of the short or long latency stretch reflex components. Effects of high-intensity isometric resistance training on induced tremor was assessed under two contraction conditions: relative force matching, where the relative level of activity was equal for both pre- and post-training sessions, set at 30% maximum voluntary contraction (MVC), and absolute force matching, where the level of activity was set to 30% pretrained MVC. The training group experienced a 26.5% increase in MVC in contrast to the 0.8% for the control group. For relative force-matching contractions, induced tremor amplitude and frequency did not change in either the training or control group. During absolute force-matching contractions, induced tremor amplitude was decreased by 37.5% and 31.6% for the short and long components, respectively, with no accompanying change in frequency, for the training group. No change in either measure was observed in the control group for absolute force-matching contractions. The results are consistent with high-intensity isometric resistance training induced neural changes leading to increased strength, coupled with realignment of stretch reflex automatic gain compensation to the new maximal force output. Also, previous reported reductions in anisometric tremor following strength training may partly be due to changed stretch reflex behavior. PMID:23580599

  4. Acute effects of high-frequency microfocal vibratory stimulation on the H reflex of the soleus muscle. A double-blind study in healthy subjects

    PubMed Central

    Alfonsi, Enrico; Paone, Paolo; Tassorelli, Cristina; De Icco, Roberto; Moglia, Arrigo; Alvisi, Elena; Marchetta, Lucky; Fresia, Mauro; Montini, Alessandra; Calabrese, Marzia; Versiglia, Vittorio; Sandrini, Giorgio

    2015-01-01

    Summary This study in healthy subjects examined the effects of a system delivering focal microvibrations at high frequency (Equistasi®) on tonic vibration stimulus (TVS)-induced inhibition of the soleus muscle H reflex. High-frequency microvibrations significantly increased the inhibitory effect of TVS on the H reflex for up to three minutes. Moreover, Equistasi® also significantly reduced alpha-motoneuron excitability, as indicated by the changes in the ratio between the maximum-amplitude H reflex (Hmax reflex) and the maximum-amplitude muscle response (Mmax response); this effect was due to reduction of the amplitude of the H reflex because the amplitude of muscle response remained unchanged. The present findings indicate that Equistasi® has a modulatory effect on proprioceptive reflex circuits. Therefore, Equistasi® might interfere with some mechanisms involved in both physiological and pathophysiological control of movement and of posture. PMID:26727706

  5. Human flexor reflexes

    PubMed Central

    Shahani, Bhagwan T.; Young, Robert R.

    1971-01-01

    One type of flexor reflex, that recorded from the tibialis anterior muscle in response to electrical stimulation of the sole of the foot, was studied in normal subjects and patients with several neurological disorders. Normally this reflex consists of two components, the second of which is related to the actual withdrawal. The first component, normally of lower threshold, is difficult to evoke in patients with chronic spinal cord or discrete cerebral lesions, whereas it has an unusually low threshold and is very clearly seen in those with Parkinson's disease. In patients with spinal cord disease, the exaggerated flexor reflexes are seen at long latencies after relatively small stimuli. During the early phase of recovery from spinal transection, both components may be seen and are, therefore, spinal in origin. Studies of patients with the sensory neuropathy of Friedreich's ataxia suggest that the afferent fibres responsible for these flexor reflexes are the small myelinated fibres. Recovery curves demonstrate very long-lasting changes in flexor reflex excitability in normal subjects and patients with `spasticity' from spinal lesions. This differs in patients with `spasticity' from lesions rostral to the brain-stem. Examples in man of such physiological phenomena as reciprocal inhibition, local sign, habituation, temporal and spatial summation are discussed. Images PMID:5122389

  6. Moro reflex

    MedlinePlus

    ... area into the arm may be present (these nerves are called brachial plexus). A Moro reflex in an older infant, child, or adult is ... be done to examine the child's muscles and nerves. Diagnostic ... absent reflex, may include: Shoulder x-ray Tests for disorders ...

  7. Aging alters muscle reflex control of autonomic cardiovascular responses to rhythmic contractions in humans.

    PubMed

    Sidhu, Simranjit K; Weavil, Joshua C; Venturelli, Massimo; Rossman, Matthew J; Gmelch, Benjamin S; Bledsoe, Amber D; Richardson, Russell S; Amann, Markus

    2015-11-01

    We investigated the influence of aging on the group III/IV muscle afferents in the exercise pressor reflex-mediated cardiovascular response to rhythmic exercise. Nine old (OLD; 68 ± 2 yr) and nine young (YNG; 24 ± 2 yr) males performed single-leg knee extensor exercise (15 W, 30 W, 80% max) under control conditions and with lumbar intrathecal fentanyl impairing feedback from group III/IV leg muscle afferents. Mean arterial pressure (MAP), cardiac output, leg blood flow (QL), systemic (SVC) and leg vascular conductance (LVC) were continuously determined. With no hemodynamic effect at rest, fentanyl blockade during exercise attenuated both cardiac output and QL ∼17% in YNG, while the decrease in cardiac output in OLD (∼5%) was significantly smaller with no impact on QL (P = 0.8). Therefore, in the face of similar significant ∼7% reduction in MAP during exercise with fentanyl blockade in both groups, LVC significantly increased ∼11% in OLD, but decreased ∼8% in YNG. The opposing direction of change was reflected in SVC with a significant ∼5% increase in OLD and a ∼12% decrease in YNG. Thus while cardiac output seems to account for the majority of group III/IV-mediated MAP responses in YNG, the impact of neural feedback on the heart may decrease with age and alterations in SVC become more prominent in mediating the similar exercise pressor reflex in OLD. Interestingly, in terms of peripheral hemodynamics, while group III/IV-mediated feedback plays a clear role in increasing LVC during exercise in the YNG, these afferents seem to actually reduce LVC in OLD. These peripheral findings may help explain the limited exercise-induced peripheral vasodilation often associated with aging. PMID:26386110

  8. Effect of angular velocity on soleus and medial gastrocnemius H-reflex during maximal concentric and eccentric muscle contraction.

    PubMed

    Duclay, Julien; Robbe, Alice; Pousson, Michel; Martin, Alain

    2009-10-01

    At rest, the H-reflex is lower during lengthening than shortening actions. During passive lengthening, both soleus (SOL) and medial gastrocnemius (MG) H-reflex amplitudes decrease with increasing angular velocity. This study was designed to investigate whether H-reflex amplitude is affected by angular velocity during concentric and eccentric maximal voluntary contraction (MVC). Experiments were performed on nine healthy men. At a constant angular velocity of 60 degrees /s and 20 degrees /s, maximal H-reflex and M-wave potentials were evoked at rest (i.e., H(max) and M(max), respectively) and during concentric and eccentric MVC (i.e., H(sup) and M(sup), respectively). Regardless of the muscle, H(max)/M(max) was lower during lengthening than shortening actions and the H(sup)/M(sup) ratio was higher than H(max)/M(max) during lengthening actions. Whereas no action type and angular velocity effects on the MG H(sup)/M(sup) were found, the SOL H(sup)/M(sup) was lower during eccentric than concentric MVC and this depression was increased with higher angular velocity. Our findings indicate that the depression of the H-reflex amplitude during eccentric compared to concentric MVC depends mainly on the amount of inhibition induced by lengthening action. In conclusion, H-reflex should be evoked during both passive and active dynamic trials to evaluate the plasticity of the spinal loop. PMID:18555699

  9. Temporal, but not Directional, Prior Knowledge Shortens Muscle Reflex Latency in Response to Sudden Transition of Support Surface During Walking

    PubMed Central

    Shinya, Masahiro; Kawashima, Noritaka; Nakazawa, Kimitaka

    2016-01-01

    The central nervous system takes advantage of prior knowledge about potential upcoming perturbations for modulating postural reflexes. There are two distinct aspects of prior knowledge: spatial and temporal. This study investigated how each of spatial and temporal prior knowledge contributes to the shortening of muscle response latency. Eleven participants walked on a split-belt treadmill and perturbed by sudden acceleration or deceleration of the right belt at right foot contact. Spatial prior knowledge was given by instruction of possible direction (e.g., only acceleration) of upcoming perturbation at the beginning of an experimental session. Temporal prior knowledge was given to subjects by warning tones at foot contact during three consecutive strides before the perturbation. In response to acceleration perturbation, reflexive muscle activity was observed in soleus (SOL) and gastrocnemius (GAS) muscles. Onset latency of the GAS response was shorter (72 ms vs. 58 ms) when subjects knew the timing of the upcoming perturbation, whereas the latency was independent of directional prior knowledge. SOL onset latency (44 ms) was not influenced by directional nor temporal prior knowledge. Although spinal neural circuit that mediates short-latency reflex was not influenced by the prior knowledge, excitability in supra-spinal neural circuit that mediates medium- and long-latency reflex might be enhanced by knowing the timing of the upcoming perturbation. PMID:26903838

  10. Temporal, but not Directional, Prior Knowledge Shortens Muscle Reflex Latency in Response to Sudden Transition of Support Surface During Walking.

    PubMed

    Shinya, Masahiro; Kawashima, Noritaka; Nakazawa, Kimitaka

    2016-01-01

    The central nervous system takes advantage of prior knowledge about potential upcoming perturbations for modulating postural reflexes. There are two distinct aspects of prior knowledge: spatial and temporal. This study investigated how each of spatial and temporal prior knowledge contributes to the shortening of muscle response latency. Eleven participants walked on a split-belt treadmill and perturbed by sudden acceleration or deceleration of the right belt at right foot contact. Spatial prior knowledge was given by instruction of possible direction (e.g., only acceleration) of upcoming perturbation at the beginning of an experimental session. Temporal prior knowledge was given to subjects by warning tones at foot contact during three consecutive strides before the perturbation. In response to acceleration perturbation, reflexive muscle activity was observed in soleus (SOL) and gastrocnemius (GAS) muscles. Onset latency of the GAS response was shorter (72 ms vs. 58 ms) when subjects knew the timing of the upcoming perturbation, whereas the latency was independent of directional prior knowledge. SOL onset latency (44 ms) was not influenced by directional nor temporal prior knowledge. Although spinal neural circuit that mediates short-latency reflex was not influenced by the prior knowledge, excitability in supra-spinal neural circuit that mediates medium- and long-latency reflex might be enhanced by knowing the timing of the upcoming perturbation. PMID:26903838

  11. [The threshold levels of the stapedius reflex depending on the relationship between the gas pressure in the external auditory meatus and the middle ear].

    PubMed

    Petrov, S M; Azizov, G R; Gritsiuk, M I; Timenko, A N

    2014-01-01

    The objective of the present work was to detect and elucidate effects of a single factor (gas pressure) responsible for the threshold levels of stapedius reflex. It was shown that the threshold reflexes were recorded at 105 dB SPL when the gas pressure in the external auditory meatus decreased by 150-200 pPa against the atmospheric pressure and when it increased by 100-150 pPa. These effects can be accounted for by the reduced compliance of the tympanic membrane and different changes in the state of the auditory ossicles undergoing compression and tension. When entering the most comfortable stapedial reflex levels into the patient's tuning chart, an account should be taken of the maximum value of tympanic membrane compliance. PMID:25377672

  12. [Sugammadex reversal after extubation under muscle relaxation to prevent cough reflex in a patient with intractable spontaneous pneumothorax].

    PubMed

    Ota, Chiho; Ueta, Kazuyoshi; Imada, Tatsuyuki; Hayashi, Yukio; Mashimo, Takashi

    2013-08-01

    A 40-year-old man (168 cm tall and weighing 71 kg) with intractable pneumothorax was operated for resection of a bulla in the left lung. After insertion of epidural catheter via T 5-6 interspace, general anesthesia was induced and maintained with propofol, remifentanil and rocuronium. The duration of surgery was 1h 48 min and rocuronium given during surgery was 110 mg. After completion of surgery, the double-lumen tube was replaced with laryngeal mask airway to prevent cough reflex. However, infusion of sugammadex 200 mg induced mild cough reflex, resulting in air leakage from thoracic drainage. Because air leakage still continued after extubation, reoperation must be done and re-intubation was required. Since rocuronium 50 mg did not provide satisfactory muscle relaxation measured by train of four, additional dose of rocuronium 40 mg was administered and re-intubation was successfully performed without cough reflex. Reoperation lasted for 43 minutes and rocuronium infused was 100 mg. Nasal airway was inserted to prevent airway obstruction by the tongue and extubation was performed under muscle relaxation with infusion of rocuronium 10 mg. And then, immediate administration of sugammadex 400 mg could elicit spontaneous respiration without cough reflex. PMID:23984577

  13. P2X and NMDA receptor involvement in temporomandibular joint-evoked reflex activity in rat jaw muscles.

    PubMed

    Watanabe, T; Tsuboi, Y; Sessle, B J; Iwata, K; Hu, J W

    2010-07-30

    We have previously shown that injection of the excitatory amino glutamate into the rat temporomandibular joint (TMJ) evokes reflex activity in both anterior digastric (DIG) and masseter (MASS) muscles that can be attenuated by prior TMJ injection of an N-methyl-d-aspartate (NMDA) receptor antagonist. The aim of the present study was to test if jaw muscle activity could also be evoked by P2X receptor agonist injection into the rat TMJ region and if the reflex activity could be modulated by TMJ injection of P2X receptor antagonist or NMDA receptor antagonist. The selective P2X subtype agonist alpha,beta-methylene adenosine 5'-triphosphate (alpha,beta-me ATP) and vehicle (phosphate-buffered saline) or the selective P2X antagonist, 2'-(or-3')-O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate (TNP-ATP) or the selective NMDA antagonist (+/-)-d-2-amino-5-phosphonovalerate(APV) were injected into the rat TMJ region. Electromyographic (EMG) reflex activity was recorded in both DIG and MASS muscles. Compared with the baseline EMG activity, alpha,beta-me-ATP injection into the TMJ (but not its systemic administration) following pre-injection of the vehicle significantly increased the magnitude and the duration of ipsilateral DIG and MASS EMG activity in a dose-dependent manner. The alpha,beta-me-ATP-evoked responses could be antagonized by pre-injection of TNP-ATP into the same TMJ site but contralateral TMJ injection of TNP-ATP proved ineffective. Furthermore, the alpha,beta-me-ATP-evoked responses could also be antagonized by APV injected into the same TMJ site but not by its systemic injection. These results indicate the interaction of peripheral purinergic as well as glutamatergic receptor mechanisms in the processing of TMJ nociceptive afferent inputs that evoke reflex activity in jaw muscles. PMID:20501327

  14. Connecting ears to eye muscles: evolution of a 'simple' reflex arc.

    PubMed

    Straka, Hans; Fritzsch, Bernd; Glover, Joel C

    2014-01-01

    Developmental and evolutionary data from vertebrates are beginning to elucidate the origin of the sensorimotor pathway that links gravity and motion detection to image-stabilizing eye movements--the vestibulo-ocular reflex (VOR). Conserved transcription factors coordinate the development of the vertebrate ear into three functional sensory compartments (graviception/translational linear acceleration, angular acceleration and sound perception). These sensory components connect to specific populations of vestibular and auditory projection neurons in the dorsal hindbrain through undetermined molecular mechanisms. In contrast, a molecular basis for the patterning of the vestibular projection neurons is beginning to emerge. These are organized through the actions of rostrocaudally and dorsoventrally restricted transcription factors into a 'hodological mosaic' within which coherent and largely segregated subgroups are specified to project to different targets in the spinal cord and brain stem. A specific set of these regionally diverse vestibular projection neurons functions as the central element that transforms vestibular sensory signals generated by active and passive head and body movements into motor output through the extraocular muscles. The large dynamic range of motion-related sensory signals requires an organization of VOR pathways as parallel, frequency-tuned, hierarchical connections from the sensory periphery to the motor output. We suggest that eyes, ears and functional connections subserving the VOR are vertebrate novelties that evolved into a functionally coherent motor control system in an almost stereotypic organization across vertebrate taxa. PMID:24776996

  15. Training-specific adaptations of H- and stretch reflexes in human soleus muscle.

    PubMed

    Gruber, M; Taube, W; Gollhofer, A; Beck, S; Amtage, F; Schubert, M

    2007-01-01

    The authors investigated the effect of physical exercise on reflex excitability in a controlled intervention study. Healthy participants (N = 21) performed 4 weeks of either power training (ballistic strength training) or balance training (sensorimotor training [SMT]). Both training regimens enhanced balance control and rate of force development, whereas reductions in peak-to-peak amplitudes of stretch reflexes and in the ratio of the maximum Hoffman reflex to the maximum efferent motor response (Hmax:Mmax) measured at rest were limited to SMT. The differences in reflex excitability between the training regimens indicated different underlying neural mechanisms of adaptation. The reduced reflex excitability following SMT was most likely induced by supraspinal influence. The authors discuss an overall increase in presynaptic inhibition of Ia afferent fibers as a possible mechanism. PMID:17251172

  16. Infant reflexes

    MedlinePlus

    ... neck reflex; Galant reflex; Truncal incurvation; Rooting reflex; Parachute reflex; Grasp reflex ... was stroked and begin to make sucking motions. PARACHUTE REFLEX This reflex occurs in slightly older infants ...

  17. Combined, but not individual, blockade of ASIC3, P2X, and EP4 receptors attenuates the exercise pressor reflex in rats with freely perfused hindlimb muscles.

    PubMed

    Stone, Audrey J; Copp, Steven W; Kim, Joyce S; Kaufman, Marc P

    2015-12-01

    In healthy humans, tests of the hypothesis that lactic acid, PGE2, or ATP plays a role in evoking the exercise pressor reflex proved controversial. The findings in humans resembled ours in decerebrate rats that individual blockade of the receptors to lactic acid, PGE2, and ATP had only small effects on the exercise pressor reflex provided that the muscles were freely perfused. This similarity between humans and rats prompted us to test the hypothesis that in rats with freely perfused muscles combined receptor blockade is required to attenuate the exercise pressor reflex. We first compared the reflex before and after injecting either PPADS (10 mg/kg), a P2X receptor antagonist, APETx2 (100 μg/kg), an activating acid-sensing ion channel 3 (ASIC) channel antagonist, or L161982 (2 μg/kg), an EP4 receptor antagonist, into the arterial supply of the hindlimb of decerebrated rats. We then examined the effects of combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the exercise pressor reflex using the same doses, intra-arterial route, and time course of antagonist injections as those used for individual blockade. We found that neither PPADS (n = 5), APETx2 (n = 6), nor L161982 (n = 6) attenuated the reflex. In contrast, combined blockade of these receptors (n = 7) attenuated the peak (↓27%, P < 0.019) and integrated (↓48%, P < 0.004) pressor components of the reflex. Combined blockade injected intravenously had no effect on the reflex. We conclude that combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the endings of thin fiber muscle afferents is required to attenuate the exercise pressor reflex in rats with freely perfused hindlimbs. PMID:26472871

  18. [Skin temperature and lactate threshold during muscle work in sportsmen].

    PubMed

    Akimov, E B; Son'kin, V D

    2011-01-01

    The purpose of the investigation was to estimate change of a thermal condition of an organism during exhausting work (maximal aerobic test) on cycle ergometer on the basis of studying of dynamics of temperature of a forehead skin. Regularly training 20 men have taken part in the research--sportsmen of various specializations (skiers, rock-climbers, boxers, etc.). Temperature of forehead skin was registered by infrared thermovision chamber Nec TH 9100SL. These results compared with the data of measurements of heart rate, gas exchange, the lactate concentration in peripheral blood, and also with anthropometrical characteristics. It was shown that on dynamics of skin temperature at maximal work load it was possible to divide all subjects into 2 unequal groups: 1 (2/3 subjects, the majority of which trains endurance) - after temperature decrease take place its smooth increase up to refusal ofwork; 2 (1/3 subjects, concerning various sports specializations)--from the moment of the beginning of active evaporation of sweat the temperature decreases to the work termination. In group 1 lactate threshold (lactate concentration in blood--4 mm/l) corresponds to the beginning of rise in temperature after its decrease as a result of sweat evaporation. In group 2 lactate threshold was necessary on a phase of decrease in temperature at the moment of active evaporation of sweat. Distinctions between groups in structure of correlation relationship between the measured indicators are revealed, inversion of a sign ofcorrelation quotient in some cases were shown. Thus significant distinctions between groups in the level of the working capacity indicators were not revealed. All it testifies to existence possibility at least two various successful strategy of urgent adaptation of system of thermoregulation to intense muscular work. PMID:22117467

  19. Differences in unconditioned and conditioned responses of the human withdrawal reflex during stance: muscle responses and biomechanical data.

    PubMed

    Kaulich, Thomas; Föhre, Wolfram; Kutz, Dieter Friedhelm; Gerwig, Markus; Timmann, Dagmar; Kolb, Florian Peter

    2010-04-22

    The aim of this study was to characterize differences between unconditioned and classically conditioned lower limb withdrawal reflexes in young subjects during standing. Electromyographic activity in the main muscle groups and biomechanical signals from a strain-gauge-equipped platform on which subjects stood were recorded from 17 healthy subjects during unconditioned stimulus (US)-alone trials and during auditory conditioning stimuli (CS) and US trials. In US-alone trials the leg muscle activation sequence was characteristic: ipsilateral, distal muscles were activated prior to proximal muscles; contralaterally the sequence was reversed. In CSUS trials latencies were shorter. Subjects unloaded the stimulated leg and shifted body weight to the supporting leg. In US-alone and in CSUS trials leg forces on each side were inversely related and asymmetric, due to preparation for unloading, whilst conditioned responses (CR), representing the unloading preparation, were symmetric. The trajectory of the center of vertical pressure during US-alone trials moved initially forward (a preparatory balance reaction) and to the stimulation side, followed by a large lateral shift to the side of the supporting limb. During CSUS trials the forwards shift was absent but the CR (early lateral shift) represented a preponed preparatory unloading. Electrophysiological and biomechanical responses of the classically conditioned lower limb withdrawal reflex in standing subjects changed significantly in CSUS trials compared to US-alone trials with higher sensitivity in the biomechanics. These findings will serve as a basis for a subsequent study on a group of patients with cerebellar diseases in whom the success of establishing procedural processes is known to be impaired. PMID:20188078

  20. Desensitization of the Mechanoreceptors in Müller's Muscle Reduces the Increased Reflex Contraction of the Orbicularis Oculi Slow-Twitch Fibers in Blepharospasm

    PubMed Central

    Ban, Ryokuya; Ban, Midori

    2014-01-01

    Objective: Although the mixed orbicularis oculi muscle lacks the muscle spindles required to induce reflex contraction of its slow-twitch fibers, the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction. We hypothesize that strong stretching of these mechanoreceptors increases reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. Methods: We examined a 71-year-old man with right blepharospasm and bilateral aponeurosis-disinserted blepharoptosis to determine whether the patient's blepharospasm was worsened by increased trigeminal proprioceptive evocation via stretching of the mechanoreceptors in Müller's muscle owing to a 60° upward gaze and serrated eyelid closure, and whether local anesthesia of the mechanoreceptors via lidocaine administration to the upper fornix as well as surgical disinsertion of Müller's muscle from the tarsus and fixation of the disinserted aponeurosis to the tarsus decreased trigeminal proprioceptive evocation and improved patient's blepharospasm. Results: Before pharmacological desensitization, 60° upward gaze and serrated eyelid closure exacerbated the patient's blepharospasm. In contrast, these maneuvers did not worsen his blepharospasm following lidocaine administration. One year after surgical desensitization, the blepharospasm had disappeared and a 60° upward gaze did not induce blepharospasm. Conclusions: Strong stretching of the mechanoreceptors in Müller's muscle appeared to increase reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. In addition to botulinum neurotoxin injections into the involuntarily contracted orbicularis oculi muscle and myectomy, surgical desensitization of the mechanoreceptors in Müller's muscle may represent an additional procedure to reduce blepharospasm. PMID:25328566

  1. The strength of the reflex response to sinusoidal stretch of monkey jaw closing muscles during voluntary contraction.

    PubMed

    Goodwin, G M; Hoffman, D; Luschei, E S

    1978-06-01

    1. Rhesus monkeys were trained to exert steady biting forces of 3--60 N for 1--2 sec. This behaviour was well maintained while sinusoidal or step opening and closing movements were imposed on the jaw. 2. The amplitude of the force modulation during sinusoidal stretching was divided by the amplitude of movement to obtain the magnitude of stiffness. This estimate was made at frequencies from 2 to 50 Hz at amplitudes of 100 and 500 micrometer (half the peak-to-peak movement at the incisors). 3. Peak magnitudes of stiffness were seen with frequencies of 8--15 Hz when the amplitude of movement was small; there was a great deal of variation between individual animals. This variation was most striking with mean forces of 25--35 N. The stiffness was greatest in animals that showed considerable spontaneous tremor, and the highest levels of stiffness were often recorded with frequencies near which tremor amplitude was large. A marked phase lag in the force response was often seen during small amplitude stretching at 8--30 Hz. 4. Estimates of stiffness for larger amplitude (500 micrometer) stretching showed less variation; the magnitude of stiffness showed maximum values below 10 Hz and a minimum at 15--30 Hz. Force always showed a phase lead on position although this lead became small in the frequency range where with smaller movement there had been phase lags. The magnitude of stiffness increased with increasing mean force. 5. Bilateral electrolytic lesions were made in the brain stems of three animals; they reduced by over 95% the expected number of cells in the mesencephalic nucleus of the fifth cranial nerve on either side. These lesions interrupted the afferent pathway for the stretch reflex and so abolished excitatory electromyogram (e.m.g.) responses to step stretches of the jaw closing muscles. 6. Such reflex responses as persisted after the lesions were small and inhibitory. E.m.g. silences followed both step stretch and release; the response to release was a 'load

  2. Stretch shortening cycle fatigue: interactions among joint stiffness, reflex, and muscle mechanical performance in the drop jump [corrected].

    PubMed

    Horita, T; Komi, P V; Nicol, C; Kyröläinen, H

    1996-01-01

    The purpose of the present study was to investigate the effect of strenuous stretch-shortening cycle exercise on the relationship between reflex and stiffness regulation during the drop jump. Ten healthy male subjects performed submaximal stretch-shortening cycle exercise on a special sledge apparatus. Exhaustion occurred on average within 3 min. A drop jump test from a 50-cm height was performed immediately before and after the sledge exercise, as well as 2 h, 2 days and 4 days later. The fatigue exercise showed relatively high blood lactate concentrations 12.5 (SD 2.6) mmol.l-1 and a 2-day delayed increase of serum cretaine kinase concentration. In drop jumps, the short latency M1 component of the vastus lateralis muscle electromyogram (EMG) response showed a continuous decline throughout the entire follow-up period after fatigue (NS), whereas the medium latency EMG component increased 2 days after the postfatigue sessions (P < 0.05). Immediately after the fatigue exercise a positive correlation (P < 0.05) was found between the changes in the short latency EMG response and in the amount of knee joint stiffness during the early postlanding phase of the drop jump. This suggests that the M1 response was closely related to the stiffness changes during the initial braking phase of the drop jump. Increase of creatine kinase concentration on the 2nd day correlated negatively with the changes in the drop jump performance (P < 0.05). Since the short latency EMG component has almost recovered on the 2nd day, impairment of the mechanical function of the muscle might have taken place. In conclusion, exhausting stretch-shortening cycle exercise induced local muscle impairment, which resulted in modulation of the reflex and stiffness interaction in the drop jump as well as compensation by central motor command. PMID:8803498

  3. A common neural element receiving rhythmic arm and leg activity as assessed by reflex modulation in arm muscles.

    PubMed

    Sasada, Syusaku; Tazoe, Toshiki; Nakajima, Tsuyoshi; Futatsubashi, Genki; Ohtsuka, Hiroyuki; Suzuki, Shinya; Zehr, E Paul; Komiyama, Tomoyoshi

    2016-04-01

    Neural interactions between regulatory systems for rhythmic arm and leg movements are an intriguing issue in locomotor neuroscience. Amplitudes of early latency cutaneous reflexes (ELCRs) in stationary arm muscles are modulated during rhythmic leg or arm cycling but not during limb positioning or voluntary contraction. This suggests that interneurons mediating ELCRs to arm muscles integrate outputs from neural systems controlling rhythmic limb movements. Alternatively, outputs could be integrated at the motoneuron and/or supraspinal levels. We examined whether a separate effect on the ELCR pathways and cortico-motoneuronal excitability during arm and leg cycling is integrated by neural elements common to the lumbo-sacral and cervical spinal cord. The subjects performed bilateral leg cycling (LEG), contralateral arm cycling (ARM), and simultaneous contralateral arm and bilateral leg cycling (A&L), while ELCRs in the wrist flexor and shoulder flexor muscles were evoked by superficial radial (SR) nerve stimulation. ELCR amplitudes were facilitated by cycling tasks and were larger during A&L than during ARM and LEG. A low stimulus intensity during ARM or LEG generated a larger ELCR during A&L than the sum of ELCRs during ARM and LEG. We confirmed this nonlinear increase in single motor unit firing probability following SR nerve stimulation during A&L. Furthermore, motor-evoked potentials following transcranial magnetic and electrical stimulation did not show nonlinear potentiation during A&L. These findings suggest the existence of a common neural element of the ELCR reflex pathway that is active only during rhythmic arm and leg movement and receives convergent input from contralateral arms and legs. PMID:26961103

  4. Muscle-specific modulation of vestibular reflexes with increased locomotor velocity and cadence.

    PubMed

    Dakin, Christopher J; Inglis, John Timothy; Chua, Romeo; Blouin, Jean-Sébastien

    2013-07-01

    Vestibular information is one of the many sensory signals used to stabilize the body during locomotion. When locomotor velocity increases, the influence of these signals appears to wane. It is unclear whether vestibular signals are globally attenuated with velocity or are influenced by factors such as whether a muscle is contributing to balance control. Here we investigate how vestibular sensory signals influence muscles of the leg during locomotion and what causes their attenuation with increasing locomotor velocity. We hypothesized that 1) vestibular signals influence the activity of all muscles engaged in the maintenance of medio-lateral stability during locomotion and 2) increases in both cadence and velocity would be associated with attenuation of these signals. We used a stochastic vestibular stimulus and recorded electromyographic signals from muscles of the ankle, knee, and hip. Participants walked using two cadences (52 and 78 steps/min) and two walking velocities (0.4 and 0.8 m/s). We observed phase-dependent modulation of vestibular influence over ongoing muscle activity in all recorded muscles. Within a stride, reversals of the muscle responses were observed in the biceps femoris, tibialis anterior, and rectus femoris. Vestibular-muscle coupling decreases with increases in both cadence and walking velocity. These results show that the observed vestibular suppression is muscle- and phase dependent. We suggest that the phase- and muscle-specific influence of vestibular signals on locomotor activity is organized according to each muscle's functional role in body stabilization during locomotion. PMID:23576695

  5. Cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator muscle are located in the mesencephalic trigeminal nucleus in rats.

    PubMed

    Fujita, Kenya; Matsuo, Kiyoshi; Yuzuriha, Shunsuke; Kawagishi, Kyutaro; Moriizumi, Tetsuji

    2012-12-01

    Since the levator and frontalis muscles lack interior muscle spindles despite being antigravity mixed muscles to involuntarily sustain eyelid opening and eyebrow lifting, this study has proposed a hypothetical mechanism to compensate for this anatomical defect. The voluntary contraction of fast-twitch fibres of the levator muscle stretches the mechanoreceptors in Müller's muscle to evoke proprioception, which continuously induces reflex contraction of slow-twitch fibres of the levator and frontalis muscles. This study confirmed the presence of cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator and frontalis muscles. After confirming that severing the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle induced ipsilateral eyelid ptosis, Fluorogold was applied as a tracer to the proximal stump of the trigeminal proprioceptive nerve in rats. Fluorogold labelled the cell bodies of the trigeminal proprioceptive neurons, not in any regions of the rat brain including the trigeminal ganglion, but in the ipsilateral mesencephalic trigeminal nucleus neighbouring the locus ceruleus. Some Fluorogold particles accumulated in the area of the locus ceruleus. The trigeminal proprioceptive neurons could be considered centrally displaced ganglion cells to transmit afferent signal from the mechanoreceptors in Müller's muscle to the mesencephalon, where they may be able to make excitatory synaptic connections with both the oculomotor neurons and the frontalis muscle motoneurons for the involuntary coordination of the eyelid and eyebrow activities, and potentially to the locus ceruleus. PMID:23157498

  6. A threshold-based approach for muscle contraction detection from surface EMG signals

    NASA Astrophysics Data System (ADS)

    Morantes, Gaudi; Fernández, Gerardo; Altuve, Miguel

    2013-11-01

    Surface electromyographic (SEMG) signals are commonly used as control signals in prosthetic and orthotic devices. Super cial electrodes are placed on the skin of the subject to acquire its muscular activity through this signal. The muscle contraction episode is then in charge of activating and deactivating these devices. Nevertheless, there is no gold standard" to detect muscle contraction, leading to delayed responses and false and missed detections. This fact motivated us to propose a new approach that compares a smoothed version of the SEMG signal with a xed threshold, in order to detect muscle contraction episodes. After preprocessing the SEMG signal, the smoothed version is obtained using a moving average lter, where three di erent window lengths has been evaluated. The detector was tuned by maximizing sensitivity and speci city and evaluated using SEMG signals obtained from the anterior tibial and gastrocnemius muscles, taken during the walking of ve subjects. Compared with traditional detection methods, we obtain a reduction of 3 ms in the detection delay, an increase of 8% in sensitivity but a decrease of 15% in speci city. Future work is directed to the inclusion of a temporal threshold (a double-threshold approach) to minimize false detections and reduce detection delays.

  7. Dual Modulation of Nociception and Cardiovascular Reflexes during Peripheral Ischemia through P2Y1 Receptor-Dependent Sensitization of Muscle Afferents

    PubMed Central

    Queme, Luis F.; Ross, Jessica L.; Lu, Peilin; Hudgins, Renita C.

    2016-01-01

    Numerous musculoskeletal pain disorders are based in dysfunction of peripheral perfusion and are often comorbid with altered cardiovascular responses to muscle contraction/exercise. We have recently found in mice that 24 h peripheral ischemia induced by a surgical occlusion of the brachial artery (BAO) induces increased paw-guarding behaviors, mechanical hypersensitivity, and decreased grip strength. These behavioral changes corresponded to increased heat sensitivity as well as an increase in the numbers of chemosensitive group III/IV muscle afferents as assessed by an ex vivo forepaw muscles/median and ulnar nerves/dorsal root ganglion (DRG)/spinal cord (SC) recording preparation. Behaviors also corresponded to specific upregulation of the ADP-responsive P2Y1 receptor in the DRGs. Since group III/IV muscle afferents have separately been associated with regulating muscle nociception and exercise pressor reflexes (EPRs), and P2Y1 has been linked to heat responsiveness and phenotypic switching in cutaneous afferents, we sought to determine whether upregulation of P2Y1 was responsible for the observed alterations in muscle afferent function, leading to modulation of muscle pain-related behaviors and EPRs after BAO. Using an afferent-specific siRNA knockdown strategy, we found that inhibition of P2Y1 during BAO not only prevented the increased mean blood pressure after forced exercise, but also significantly reduced alterations in pain-related behaviors. Selective P2Y1 knockdown also prevented the increased firing to heat stimuli and the BAO-induced phenotypic switch in chemosensitive muscle afferents, potentially through regulating membrane expression of acid sensing ion channel 3. These results suggest that enhanced P2Y1 in muscle afferents during ischemic-like conditions may dually regulate muscle nociception and cardiovascular reflexes. SIGNIFICANCE STATEMENT Our current results suggest that P2Y1 modulates heat responsiveness and chemosensation in muscle afferents

  8. Soleus H-reflex gain in humans walking and running under simulated reduced gravity

    NASA Technical Reports Server (NTRS)

    Ferris, D. P.; Aagaard, P.; Simonsen, E. B.; Farley, C. T.; Dyhre-Poulsen, P.

    2001-01-01

    The Hoffmann (H-) reflex is an electrical analogue of the monosynaptic stretch reflex, elicited by bypassing the muscle spindle and directly stimulating the afferent nerve. Studying H-reflex modulation provides insight into how the nervous system centrally modulates stretch reflex responses.A common measure of H-reflex gain is the slope of the relationship between H-reflex amplitude and EMG amplitude. To examine soleus H-reflex gain across a range of EMG levels during human locomotion, we used simulated reduced gravity to reduce muscle activity. We hypothesised that H-reflex gain would be independent of gravity level.We recorded EMG from eight subjects walking (1.25 m s-1) and running (3.0 m s-1) at four gravity levels (1.0, 0.75, 0.5 and 0.25 G (Earth gravity)). We normalised the stimulus M-wave and resulting H-reflex to the maximal M-wave amplitude (Mmax) elicited throughout the stride to correct for movement of stimulus and recording electrodes relative to nerve and muscle fibres. Peak soleus EMG amplitude decreased by 30% for walking and for running over the fourfold change in gravity. As hypothesised, slopes of linear regressions fitted to H-reflex versus EMG data were independent of gravity for walking and running (ANOVA, P > 0.8). The slopes were also independent of gait (P > 0.6), contrary to previous studies. Walking had a greater y-intercept (19.9% Mmax) than running (-2.5% Mmax; P < 0.001). At all levels of EMG, walking H-reflex amplitudes were higher than running H-reflex amplitudes by a constant amount. We conclude that the nervous system adjusts H-reflex threshold but not H-reflex gain between walking and running. These findings provide insight into potential neural mechanisms responsible for spinal modulation of the stretch reflex during human locomotion.

  9. Tissue engineering the mechanosensory circuit of the stretch reflex arc: sensory neuron innervation of intrafusal muscle fibers

    PubMed Central

    Rumsey, John W; Das, Mainak; Bhalkikar, Abhijeet; Stancescu, Maria; Hickman, James J

    2010-01-01

    The sensory circuit of the stretch reflex arc, composed of specialized intrafusal muscle fibers and type Ia proprioceptive sensory neurons, converts mechanical information regarding muscle length and stretch to electrical action potentials and relays them to the central nervous system. Utilizing a non-biological substrate, surface patterning photolithography and a serum-free medium formulation a co-culture system was developed that facilitated functional interactions between intrafusal muscle fibers and sensory neurons. The presence of annulospiral wrappings (ASWs) and flower spray endings (FSEs), both physiologically relevant morphologies in sensory neuron-intrafusal fiber interactions, were demonstrated and quantified using immunocytochemistry. Furthermore, two proposed components of the mammalian mechanosensory transduction system, BNaC1 and PICK1, were both identified at the ASWs and FSEs. To verify functionality of the mechanoreceptor elements the system was integrated with a MEMS cantilever device, and Ca2+ currents were imaged along the length of an axon innervating an intrafusal fiber when stretched by cantilever deflection. This system provides a platform for examining the role of this mechanosensory complex in the pathology of myotonic and muscular dystrophies, peripheral neuropathy, and spasticity inducing diseases like Parkinson's. These studies will also assist in engineering fine motor control for prosthetic devices by improving our understanding of mechanosensitive feedback. PMID:20708792

  10. An Intelligent Computerized Stretch Reflex Measurement System For Clinical And Investigative Neurology

    NASA Astrophysics Data System (ADS)

    Flanagan, P. M.; Chutkow, J. G.; Riggs, M. T.; Cristiano, V. D.

    1987-05-01

    We describe the design of a reliable, user-friendly preprototype system for quantifying the tendon stretch reflexes in humans and large mammals. A hand-held, instrumented reflex gun, the impactor of which contains a single force sensor, interfaces with a computer. The resulting test system can deliver sequences of reproducible stimuli at graded intensities and adjustable durations to a muscle's tendon ("tendon taps"), measure the impacting force of each tap, and record the subsequent reflex muscle contraction from the same tendon -- all automatically. The parameters of the reflex muscle contraction include latency; mechanical threshold; and peak time, peak magnitude, and settling time. The results of clinical tests presented in this paper illustrate the system's potential usefulness in detecting neurologic dysfunction affecting the tendon stretch reflexes, in documenting the course of neurologic illnesses and their response to therapy, and in clinical and laboratory neurologic research.

  11. Superposition of H reflexes on steady contractions in man.

    PubMed Central

    Rüegg, D G; Krauer, R; Drews, H

    1990-01-01

    1. The aim of the investigation was to study the influence of steady isometric contractions on H reflexes of human soleus muscle. 2. Stimulating and recording conditions were hardly affected by plantar flexions which subjects maintained in a force matching task. 3. If the interval between a preceding control and the test stimulus was less than 8 s the test H reflex was depressed in the relaxed subject. The depression was diminished or removed if the test reflex was superimposed on a background activity. The interval between control and test H reflex was at least 8 s in the following experiments. 4. H reflexes were nearly independent of steady plantar flexions on which they were superimposed. In some subjects, there was a slight increase with increasing torque. During dorsal flexions, H reflexes in all subjects were inhibited with increasing torque. 5. The relationship between test H reflexes, control H reflexes and background activity was evaluated by varying pseudo-randomly stimulus intensity and steady flexion torque. The surface defined by this three-dimensional relation approximated a plane suggesting linear properties of the H reflex. In some subjects threshold intensity decreased slightly with torque, in others it was constant. 6. In response to a warning signal, human subjects initiated steady plantar or dorsal flexions in both feet and, at the same time, they started to concentrate on a light at the onset of which they performed a unilateral ballistic plantar contraction as fast as possible. The relations between H reflex and maintained flexion force during the warning period of the reaction time task were identical to those during force matching, showing that the behavioural context did not modulate the relations. 7. The relations were also the same if reflexes were evoked bi- or unilaterally, illustrating the absence of a mutual modification of simultaneously evoked H reflexes. 8. The relation was the same with ipsilateral matching and relaxed

  12. Inspiratory muscle training with threshold or incentive spirometry: Which is the most effective?

    PubMed

    Paiva, Dulciane Nunes; Assmann, Laíse Bender; Bordin, Diogo Fanfa; Gass, Ricardo; Jost, Renan Trevisan; Bernardo-Filho, Mario; França, Rodrigo Alves; Cardoso, Dannuey Machado

    2015-01-01

    Inspiratory muscular training (IMT) increases the respiratory muscle strength, however, there is no data demonstrating its superiority over the incentive spirometry (IS) in doing so. Values of muscle strength after IMT (Threshold IMT(®)) and by the IS (Voldyne(®)) in healthy females was compared. Subjects (n=40) were randomly divided into control group (CG, n=14), IS group (ISG, n=13) and threshold group (TG, n=13). PImax was measured before (pre-IMT), at 15 and 30 days of IMT. There was an increase in PImax of the TG at 15 days (p<0.001) and 30 days of IMT (p<0.001). The same occurred with the ISG, which increased the PImax at 15 days (p<0.001) and 30 days of training (p<0.001). After 30 days of IMT, the TG presented a PImax which was significantly higher than ISG and the CG (p=0.045 and p<0.001, respectively). It can be concluded that IMT by threshold was more effective in increasing muscle strength than the Voldyne. PMID:25926370

  13. The effects of smartphone use on upper extremity muscle activity and pain threshold.

    PubMed

    Lee, Minkyung; Hong, Yunkyung; Lee, Seunghoon; Won, Jinyoung; Yang, Jinjun; Park, Sookyoung; Chang, Kyu-Tae; Hong, Yonggeun

    2015-06-01

    [Purpose] The purpose of this study was to determine whether muscle activity and pressure-induced pain in the upper extremities are affected by smartphone use, and to compare the effects of phone handling with one hand and with both hands. [Subjects] The study subjects were asymptomatic women 20-22 years of age. [Methods] The subjects sat in a chair with their feet on the floor and the elbow flexed, holding a smartphone positioned on the thigh. Subsequently, the subjects typed the Korean anthem for 3 min, one-handed or with both hands. Each subject repeated the task three times, with a 5-min rest period between tasks to minimize fatigue. Electromyography (EMG) was used to record the muscle activity of the upper trapezius (UT), extensor pollicis longus (EPL), and abductor pollicis (AP) during phone operation. We also used a dolorimeter to measure the pressure-induced pain threshold in the UT. [Results] We observed higher muscle activity in the UT, AP, and EPL in one-handed smartphone use than in its two-handed use. The pressure-induced pain threshold of the UT was lower after use of the smartphone, especially after one-handed use. [Conclusion] Our results show that smartphone operation with one hand caused greater UT pain and induced increased upper extremity muscle activity. PMID:26180311

  14. The effects of smartphone use on upper extremity muscle activity and pain threshold

    PubMed Central

    Lee, Minkyung; Hong, Yunkyung; Lee, Seunghoon; Won, Jinyoung; Yang, Jinjun; Park, Sookyoung; Chang, Kyu-Tae; Hong, Yonggeun

    2015-01-01

    [Purpose] The purpose of this study was to determine whether muscle activity and pressure-induced pain in the upper extremities are affected by smartphone use, and to compare the effects of phone handling with one hand and with both hands. [Subjects] The study subjects were asymptomatic women 20–22 years of age. [Methods] The subjects sat in a chair with their feet on the floor and the elbow flexed, holding a smartphone positioned on the thigh. Subsequently, the subjects typed the Korean anthem for 3 min, one-handed or with both hands. Each subject repeated the task three times, with a 5-min rest period between tasks to minimize fatigue. Electromyography (EMG) was used to record the muscle activity of the upper trapezius (UT), extensor pollicis longus (EPL), and abductor pollicis (AP) during phone operation. We also used a dolorimeter to measure the pressure-induced pain threshold in the UT. [Results] We observed higher muscle activity in the UT, AP, and EPL in one-handed smartphone use than in its two-handed use. The pressure-induced pain threshold of the UT was lower after use of the smartphone, especially after one-handed use. [Conclusion] Our results show that smartphone operation with one hand caused greater UT pain and induced increased upper extremity muscle activity. PMID:26180311

  15. Evaluation of the THRESHOLD trainer for inspiratory muscle endurance training: comparison with the weighted plunger method.

    PubMed

    Johnson, P H; Cowley, A J; Kinnear, W J

    1996-12-01

    Inspiratory muscle training (IMT) has been shown to enhance exercise performance. The weighted plunger (WP) system of inspiratory threshold loading is the most commonly used method of IMT, but is expensive and cumbersome. We have evaluated a commercially available portable spring-loaded IMT device, the THRESHOLD trainer. The WP and THRESHOLD trainer devices were evaluated with their opening pressures set, in random order, at 10, 20, 30 and 40 cmH2O. Using an airpump, pressure at the valve inlet was recorded at the point at which the valve opened, and at airflow rates of 20, 40, 60, 80 and 100 L.min-1. Ten THRESHOLD trainers were then compared using the same opening pressures and airflow rates. Finally, 10 patients with stable chronic heart failure (CHF) inspired, in random order, through the WP and THRESHOLD trainer for 4 min each. The pressure-time product (PTP) was calculated for each 4 min period, to compare the work performed on inspiring through each device. The mean measured opening pressures for the WP set at 10, 20, 30 and 40 cmH2O, were 9.0, 19.3, 27.9 and 39.2 cmH2O, respectively, and there was little change over the range of flow tested. Corresponding values for the THRESHOLD trainer were 7.5, 16.9, 26.2 and 39.1 cmH2O, with the pressure being closer to the set pressure as flow increased to that seen in clinical practice. The 10 different trainers tested performed very similarly to one another. Work performed (as measured by PTP) on inspiring through the WP and THRESHOLD trainer was not significantly different. Although less accurate than the weighted plunger, the THRESHOLD trainer is an inexpensive device of consistent quality. In a clinical setting it would be a satisfactory option for inspiratory muscle training in most patients, but less so in patients with very low inspiratory flow rates. PMID:8980985

  16. The Effects of Temporal and Spatial Predictions on Stretch Reflexes of Ankle Flexor and Extensor Muscles While Standing

    PubMed Central

    Kawashima, Noritaka; Nakazawa, Kimitaka

    2016-01-01

    The purpose of the present study was to investigate how stretch reflex (SR) responses in the ankle extensor (soleus: SOL) and flexor (tibialis anterior: TA) muscles would be modulated with temporal and/or spatial predictions of external perturbations and whether their effects are specific to the standing posture. SR responses in the SOL/TA were elicited by imposing quick ankle toes-up/toes-down rotations while standing upright and in the supine position. We designed four experimental conditions based on pre-information about perturbations: no information (No Cue), the timing of the perturbation onset (TIM), the direction of the perturbation (DIR), and both the timing and direction of the perturbation (TIM/DIR). Each condition was separated and its order was counterbalanced. In the SR of TA evoked by toes-down rotation, integrated electromyography activities of the late component were significantly reduced in the TIM and TIM/DIR conditions as compared with those in the No Cue and DIR conditions. The occurrence rate of late SR components that reflects how often the reflex response was observed was also lower in the TIM and TIM/DIR conditions as compared with that in the No Cue and DIR conditions. On the other hand, no significant changes were seen among the four conditions in the early SR component in the TA and both SR components in the SOL. The same results in the occurrence rate were found in the supine position. The present results suggest (1) only temporal predictions have a remarkable effect on the SR excitability of the TA, and (2) this effect is independent of posture. PMID:27385043

  17. The relationship between the flexion synergy and stretch reflexes in individuals with chronic hemiparetic stroke.

    PubMed

    McPherson, Jacob G; Stienen, Arno H A; Drogos, Justin M; Dewald, Julius P A

    2011-01-01

    This study utilized a novel robotic device, the ACT-4D, to investigate the relationship between the flexion synergy and stretch reflexes in individuals with chronic hemiparetic stroke. Because the flexion synergy influences the amount of elbow flexor muscle activation present in the paretic limb during tasks requiring shoulder abduction loading, it was hypothesized that stretch reflexes may be modulated by expression of this abnormal muscle coactivation pattern. To test this hypothesis, the ACT-4D was used to enable 10 individuals with chronic hemiparetic stroke to generate varying amounts of shoulder abduction torque while concurrently receiving elbow extension position perturbations. It was found that increased expression of the flexion synergy led to greater reflex amplitudes as well as lower reflex velocity thresholds. The physiological basis of the flexion synergy is briefly discussed, as are the implications of the flexion synergy and stretch reflexes for purposeful movement. PMID:22275712

  18. Role of the middle ear muscle apparatus in mechanisms of speech signal discrimination

    NASA Technical Reports Server (NTRS)

    Moroz, B. S.; Bazarov, V. G.; Sachenko, S. V.

    1980-01-01

    A method of impedance reflexometry was used to examine 101 students with hearing impairment in order to clarify the interrelation between speech discrimination and the state of the middle ear muscles. Ability to discriminate speech signals depends to some extent on the functional state of intraaural muscles. Speech discrimination was greatly impaired in the absence of stapedial muscle acoustic reflex, in the presence of low thresholds of stimulation and in very small values of reflex amplitude increase. Discrimination was not impeded in positive AR, high values of relative thresholds and normal increase of reflex amplitude in response to speech signals with augmenting intensity.

  19. Postnatal development of the nociceptive withdrawal reflexes in the rat: a behavioural and electromyographic study.

    PubMed Central

    Holmberg, H; Schouenborg, J

    1996-01-01

    1. The postnatal development of nociceptive withdrawal reflexes was studied. In awake intact rats, forelimb, hindlimb and tail reflexes were recorded on videotape. In decerebrate spinal rats, electromyography (EMG) was used to record nociceptive withdrawal reflexes in musculi extensor digitorum longus (EDL), peronei, gastrocnemius-soleus (G-S) and biceps posterior-semitendinosus (BP-ST). Thermal (short-lasting CO2 laser pulses) and mechanical stimulation were used. 2. In adults, nociceptive withdrawal reflexes were typically well directed and reflex pathways to single hindlimb muscles had functionally adapted receptive fields. By contrast, at postnatal day (P) 1-7, the nociceptive withdrawal reflexes were often inappropriate, sometimes producing movements towards the stimulation, and EMG recordings revealed unadapted variable receptive fields. With increasing age, the nociceptive withdrawal reflexes progressively became well directed, thus producing localized withdrawal. Both withdrawal movements and spatial organization of the receptive fields were adult-like at P20-25. 3. Up to P25, reflex thresholds were more or less constant in both intact awake rats and spinal decerebrate rats, except in G-S in which no nociceptive withdrawal reflexes were evoked from P20 on. After P25, mechanical, but not thermal, thresholds increased dramatically. 4. EMG recordings revealed that during the first three postnatal weeks, the latency of the CO2 laser-evoked nociceptive withdrawal reflexes decreased significantly in peronei and BP-ST, but not in EDL, and thereafter increased significantly in peronei, BP-ST and EDL. The magnitude of the nociceptive withdrawal reflexes in these muscles increased markedly between P7 and P20 and showed little change thereafter. 5. Possible mechanisms underlying the postnatal tuning of the nociceptive withdrawal reflexes are discussed. PMID:8735709

  20. Neck afferents and muscle sympathetic activity in humans: implications for the vestibulosympathetic reflex.

    PubMed

    Ray, C A; Hume, K M

    1998-02-01

    We have shown previously that head-down neck flexion (HDNF) in humans elicits increases in muscle sympathetic nerve activity (MSNA). The purpose of this study was to determine the effect of neck muscle afferents on MSNA. We studied this question by measuring MSNA before and after head rotation that would activate neck muscle afferents but not the vestibular system (i.e., no stimulation of the otolith organs or semicircular canals). After a 3-min baseline period with the head in the normal erect position, subjects rotated their head to the side (approximately 90%) and maintained this position for 3 min. Head rotation was performed by the subjects in both the prone (n = 5) and sitting (n = 6) positions. Head rotation did not elicit changes in MSNA. Average MSNA, expressed as burst frequency and total activity, was 13 +/- 1 and 13 +/- 1 bursts/min and 146 +/-34 and 132 +/- 27 units/min during baseline and head rotation, respectively. There were no significant changes in calf blood flow (2.6 +/- 0.3 to 2.5 +/- 0.3 ml.100 ml-1.min-1, n = 8) and calf vascular resistance (39 +/- 4 to 41 +/- 4 units; n = 8). Heart rate (64 +/- 3 to 66 +/- 3 beats/min; P = 0.058) and mean arterial pressure (90 +/- 3 to 93 +/- 3; P < 0.05) increased slightly during head rotation. Additional neck flexion studies were performed with subjects lying on their side (n = 5), MSNA, heart rate, and mean arterial pressure were unchanged during this maneuver, which also does not engage the vestibular system. HDNF was tested in 9 of the 13 subjects. MSNA was significantly increased by 79 +/- 12% (P < 0.001) during HDNF. These findings indicate that neck afferents activated by horizontal neck rotation or flexion in the absence of significant force development do not elicit changes in MSNA. These findings support the concept that HDNF increases MSNA by the activation of the vestibular system. PMID:9475851

  1. Motor cortical plasticity in extrinsic hand muscles is determined by the resting thresholds of overlapping representations.

    PubMed

    Mirdamadi, J L; Suzuki, L Y; Meehan, S K

    2016-10-01

    Knowledge of the properties that govern the effectiveness of transcranial magnetic stimulation (TMS) interventions is critical to clinical application. Extrapolation to clinical populations has been limited by high inter-subject variability and a focus on intrinsic muscles of the hand in healthy populations. Therefore, the current study assessed variability of continuous theta burst stimulation (cTBS), a patterned TMS protocol, across an agonist-antagonist pair of extrinsic muscles of the hand. Secondarily, we assessed whether concurrent agonist contraction could enhance the efficacy of cTBS. Motor evoked potentials (MEP) were simultaneously recorded from the agonist flexor (FCR) and antagonist extensor (ECR) carpi radialis before and after cTBS over the FCR hotspot. cTBS was delivered with the FCR relaxed (cTBS-Relax) or during isometric wrist flexion (cTBS-Contract). cTBS-Relax suppressed FCR MEPs evoked from the FCR hotspot. However, the extent of FCR MEP suppression was strongly correlated with the relative difference between FCR and ECR resting motor thresholds. cTBS-Contract decreased FCR suppression but increased suppression of ECR MEPs elicited from the FCR hotspot. The magnitude of ECR MEP suppression following cTBS-Contract was independent of the threshold-amplitude relationships observed with cTBS-Relax. Contraction alone had no effect confirming the effect of cTBS-Contract was driven by the interaction between neuromuscular activity and cTBS. Interactions across muscle representations should be taken into account when predicting cTBS outcomes in healthy and clinical populations. Contraction during cTBS may be a useful means of focusing aftereffects when differences in baseline excitability across overlapping agonist-antagonist cortical representations may mitigate the inhibitory effect of cTBS. PMID:27425211

  2. Inspiratory muscle performance relative to the anaerobic threshold in patients with COPD.

    PubMed

    Wanke, T; Formanek, D; Lahrmann, H; Merkle, M; Rauscher, H; Zwick, H

    1993-09-01

    Rehabilitation programmes in chronic obstructive pulmonary disease (COPD) require exercise training above the anaerobic threshold. However, not all COPD patients develop metabolic acidosis during exercise. The hypothesis of this study was that non-exercise variables, characterizing the mechanical load on the inspiratory muscles during breathing at rest, can be used to reliably predict which patients with COPD are not able to develop metabolic acidosis during exercise. Thirty participants with COPD performed a symptom-limited cycle ergometer test. The oesophageal pressure/time index (PTIoes: the product of pressure magnitude and duration), the mean rate of pressure development during inspiration (Poes/TI), and the mean airway resistance (Raw)/maximal oesophageal pressure (Poesmax) ratio served as indices for the mechanical load on the inspiratory muscles. The oxygen uptake (VO2) at which plasma standard bicarbonate was seen to decrease from its baseline value was taken as the anaerboic threshold (AT). Mean Raw was significantly higher in those patients in whom the AT could not be detected. No other lung function parameters measured at rest allowed the accurate selection of those patients who did or did not develop exercise metabolic acidosis. On the other hand, Raw/Poesmax, PTIoes and Poes/TI were significantly different in the two patient groups. Additionally, whereas in the patient group with identifiable AT exercise hyperpnoea produced a non-linear increase of Poes/TI with respect to PTIoes above the AT, in the patient group without identifiable AT there was a linear relationship between Poes/TI and PTIoes throughout exercise. We conclude that the determination of inspiratory muscle load indices at rest may be useful in pulmonary rehabilitation programmes, for identifying those patients with COPD who do not develop exercise induced metabolic acidosis.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8224135

  3. [Use of conditioned reflex therapy in patients with masticatory muscles hypertension].

    PubMed

    Trezubov, V N; Bulycheva, E A

    2010-01-01

    This work deals with the thoughts on the nature and origin of disorders of masticatory muscles and temporor joint. The authors incline to opinion of their psychosomatic origin. In connection with this point of view the methods of investigations were added by the psychosomatic approach (Eysenk, Spilberger-Hanin, Lichko, Vassermann): so the methods of direct and indirect psychotherapy (behavior therapy and placebo), the same as psychopharmaco-therapy were included in complex rehabilitation. As behaviour therapy method the computer videoautotraining with biological adaptive reverse connection was used. 185 patients (61 men and 124 women) in age of 16-70 (mean age: 34,9+/-1,3 years old) were investigated. Complete recovery or significant improvement of health took place in 97% of patients, insufficient effect - 3% of investigative patients. PMID:20559238

  4. Effect of training intensity on muscle lactate transporters and lactate threshold of cross-country skiers.

    PubMed

    Evertsen, F; Medbø, J I; Bonen, A

    2001-10-01

    The training intensity may affect the monocarboxylate transporters MCT1 and MCT4 in skeletal muscle. Therefore, 20 elite cross-country skiers (11 men and nine women) trained hard for 5 months at either moderate (MIG, 60-70% of VO2max) or high intensity (HIG, 80-90%). The lactate threshold, several performance parameters, and the blood lactate concentration (cLa) after exhausting treadmill running were also determined. Muscle biopsies taken from the vastus lateralis muscle before and after the training period were analysed for the two MCTs and for muscle fibre types and six enzymes. The concentration of MCT1 did not change for HIG (P=0.3) but fell for MIG (-12 +/- 3%, P=0.01); the training response differed between the two groups (P=0.05). The concentration of MCT4 did not change during the training period (P > 0.10). The concentration of the two MCTs did not differ between the two sexes (P=0.9). The running speed at the lactate threshold rose for HIG (+3.2 +/- 0.9%, P=0.003), while no change was seen for MIG (P=0.54); the training response differed between the two groups (P=0.04). The cLa after long-lasting exhausting treadmill running correlated with the concentration of MCT1 (rs=0.69, P=0.002), but not with that of MCT4 (rs=0.2, P=0.2). There were no other significant correlations between the concentrations of the two MCTs and the performance parameters, muscle fibre types, or enzymes (r < or = 0.36, P > 0.10). Thus, the training response differed between MIG and HIG both in terms of performance and of the effect on MCT1. Training at high intensity may be more effective for cross-country skiers. Finally, MCT1 may be important for releasing lactate to the blood during long-lasting exercise. PMID:11683677

  5. Role played by NaV 1.7 channels on thin-fiber muscle afferents in transmitting the exercise pressor reflex.

    PubMed

    Stone, Audrey J; Copp, Steven W; Kaufman, Marc P

    2015-11-15

    Voltage-gated sodium channels (NaV) 1.7 are highly expressed on the axons of somatic afferent neurons and are thought to play an important role in the signaling of inflammatory pain. NaV 1.7 channels are classified as tetrodotoxin (TTX)-sensitive, meaning that they are blocked by TTX concentrations of less than 300 nM. These findings prompted us to determine in decerebrated, unanesthetized rats, the role played by NaV 1.7 channels in the transmission of muscle afferent input evoking the exercise pressor reflex. We first showed that the exercise pressor reflex, which was evoked by static contraction of the triceps surae muscles, was reversibly attenuated by application of 50 nM TTX, but not 5 nM TTX, to the L4-L5 dorsal roots (control: 21 ± 1 mmHg, TTX: 8 ± 2 mmHg, recovery: 21 ± 3 mmHg; n = 6; P < 0.01). We next found that the peak pressor responses to contraction were significantly attenuated by dorsal root application of 100 nM Ssm6a, a compound that is a selective NaV 1.7 channel inhibitor. Removal of Ssm6a restored the reflex to its control level (control: 19 ± 3 mmHg, Ssm6a: 10 ± 1 mmHg, recovery: 19 ± 4 mmHg; n = 6; P < 0.05). Compound action potentials recorded from the L4 and L5 dorsal roots and evoked by single-pulse stimulation of the sciatic nerve showed that both TTX and Ssm6a attenuated input from group III, as well as group IV afferents. We conclude that NaV 1.7 channels play a role in the thin-fiber muscle afferent pathway evoking the exercise pressor reflex. PMID:26310938

  6. Clinical interest of postural and vestibulo-ocular reflex changes induced by cervical muscles and skull vibration in compensated unilateral vestibular lesion patients.

    PubMed

    Dumas, Georges; Lion, Alexis; Gauchard, Gérome C; Herpin, Guillaume; Magnusson, Måns; Perrin, Philippe P

    2013-01-01

    Skull vibration induces nystagmus in unilateral vestibular lesion (UVL) patients. Vibration of skull, posterior cervical muscles or inferior limb muscles alters posture in recent UVL patients. This study aimed to investigate the postural effect of vibration in chronic compensated UVL patients. Vibration was applied successively to vertex, each mastoid, each side of posterior cervical muscles and of triceps surae in 12 UVL patients and 9 healthy subjects. Eye movements were recorded with videonystagmography. Postural control was evaluated in eyes open (EO) and eyes closed (EC) conditions. Sway area, sway path, anteroposterior and medio-lateral sways were recorded.A vibration induced nystagmus (VIN) beating toward the healthy side was obtained for each UVL patient during mastoid vibration. In EO, only sway path was higher in UVL group during vibration of mastoids and posterior cervical muscles.The EO postural impairments of UVL patients could be related to the eye movements or VIN, leading to visual perturbations, or to a proprioceptive error signal, providing an erroneous representation of head position. The vibration-induced sway was too small to be clinically useful. Vestibulo-ocular reflex observed with videonystagmography during mastoid vibration seems more relevant to reveal chronic UVL than vestibulo-spinal reflex observed with posturography. PMID:23549054

  7. Role of muscle pulleys in producing eye position-dependence in the angular vestibuloocular reflex: a model-based study

    NASA Technical Reports Server (NTRS)

    Thurtell, M. J.; Kunin, M.; Raphan, T.; Wall, C. C. (Principal Investigator)

    2000-01-01

    It is well established that the head and eye velocity axes do not always align during compensatory vestibular slow phases. It has been shown that the eye velocity axis systematically tilts away from the head velocity axis in a manner that is dependent on eye-in-head position. The mechanisms responsible for producing these axis tilts are unclear. In this model-based study, we aimed to determine whether muscle pulleys could be involved in bringing about these phenomena. The model presented incorporates semicircular canals, central vestibular pathways, and an ocular motor plant with pulleys. The pulleys were modeled so that they brought about a rotation of the torque axes of the extraocular muscles that was a fraction of the angle of eye deviation from primary position. The degree to which the pulleys rotated the torque axes was altered by means of a pulley coefficient. Model input was head velocity and initial eye position data from passive and active yaw head impulses with fixation at 0 degrees, 20 degrees up and 20 degrees down, obtained from a previous experiment. The optimal pulley coefficient required to fit the data was determined by calculating the mean square error between data and model predictions of torsional eye velocity. For active head impulses, the optimal pulley coefficient varied considerably between subjects. The median optimal pulley coefficient was found to be 0.5, the pulley coefficient required for producing saccades that perfectly obey Listing's law when using a two-dimensional saccadic pulse signal. The model predicted the direction of the axis tilts observed in response to passive head impulses from 50 ms after onset. During passive head impulses, the median optimal pulley coefficient was found to be 0.21, when roll gain was fixed at 0.7. The model did not accurately predict the alignment of the eye and head velocity axes that was observed early in the response to passive head impulses. We found that this alignment could be well predicted if

  8. Infant reflexes

    MedlinePlus

    ... or her hips toward the touch in a dancing movement. Grasp reflex . This reflex occurs if you ... reflex occurs in slightly older infants when the child is held upright and the baby’s body is ...

  9. The effect on mechanical pain threshold over human muscles by oral administration of granisetron and diclofenac-sodium.

    PubMed

    Christidis, Nikolaos; Kopp, Sigvard; Ernberg, Malin

    2005-02-01

    Previous studies indicate that plasma levels of serotonin (5-HT) and intramuscular prostaglandin E2 (PGE2) participate in determining the mechanical pain threshold and tolerance level to pressure applied on the skin over healthy muscles. Other studies reported gender differences regarding responses to noxious stimuli. The present study aimed to determine whether the mechanical pain threshold of healthy muscles is influenced by oral administration of 5-HT3 or PGE2-inhibitors and if there are any gender differences in this respect. Ten healthy female subjects and 10 age-matched healthy male subjects participated in the study, which was randomized and double blind with crossover design. Granisetron (5-HT3-antagonist), diclofenac-sodium (PGE2-antagonist) and placebo were administered for 3 days. The pressure pain threshold (PPT) was recorded bilaterally with an algometer over certain orofacial, trunk, and limb muscles before and after administration of the antagonists. The PPT over all muscles combined increased after administration of granisetron. There was no change after administration of placebo. The difference between granisetron and placebo was significant for the trapezius and tibialis anterior muscles. Diclofenac-sodium did not influence the PPT and there was no difference compared to placebo. Although the basal PPT values were lower in females, the PPT response to granisetron differed significantly between genders only in the tibialis anterior muscle. In conclusion, the results of this study showed that oral administration of the 5-HT3-antagonist granisetron increased the PPT over healthy trunk and limb muscles but not over orofacial muscles, and that the response in the limb muscles was greater in males. PMID:15661432

  10. Changes in the Achilles tendon reflexes following Skylab missions

    NASA Technical Reports Server (NTRS)

    Baker, J. T.; Nicogossian, A. E.; Hoffler, G. W.; Johnson, R. L.; Hordinsky, J. R.

    1977-01-01

    Postflight measurements of Achilles tendon reflex duration on Skylab crewmen indicate a state of disequilibrium between the flexor and extensor muscle groups with an initial decrease in reflex duration. As the muscles regain strength and mass there occurs an overcompensation reflected by increased reflex duration. Finally, when a normal neuromuscular state is reached the reflex duration returns to baseline value.

  11. TETANUS TOXIN REDUCES LOCAL AND DESCENDING REGULATION OF THE H-REFLEX

    PubMed Central

    MATTHEWS, CHRISTOPHER C.; FISHMAN, PAUL S.; WITTENBERG, GEORGE F.

    2015-01-01

    Introduction Skeletal muscles that are under the influence of tetanus toxin show an exaggerated reflex response to stretch. We examined which changes in the stretch reflex may underlie the exaggerated response. Methods H-reflexes were obtained from the tibialis anterior (TA) and flexor digitorum brevis (FDB) muscles in rats 7 days after intramuscular injection of tetanus toxin into the TA. Results We found effects of the toxin on the threshold, amplitude, and duration of H-waves from the TA. The toxin inhibited rate-dependent depression in the FDB between the stimulation frequencies of 0.5–50 HZ and when a conditioning magnetic stimulus applied to the brain preceded a test electrical stimulus delivered to the plantar nerve. Conclusions Tetanus toxin increased the amplitude of the H-wave and reduced the normal depression of H-wave amplitude that is associated with closely timed stimuli, two phenomena that could contribute to hyperactivity of the stretch reflex. PMID:24772492

  12. Organization of sensory input to the nociceptive-specific cutaneous trunk muscle reflex in rat, an effective experimental system for examining nociception and plasticity

    PubMed Central

    Petruska, Jeffrey C.; Barker, Darrell F.; Garraway, Sandra M.; Trainer, Robert; Fransen, James W.; Seidman, Peggy A.; Soto, Roy G.; Mendell, Lorne M.; Johnson, Richard D.

    2013-01-01

    Detailed characterization of neural circuitries furthers our understanding of how nervous systems perform specific functions and enables the use of those systems to test hypotheses. We have characterized the sensory input to the cutaneous trunk muscle (CTM; also cutaneus trunci (rat) or cutaneus maximus (mouse)) reflex (CTMR), which manifests as a puckering of the dorsal thoracolumbar skin and is selectively driven by noxious stimuli. CTM electromyography (EMG) and neurogram recordings in naïve rats revealed that CTMR responses were elicited by natural stimuli and electrical stimulation of all segments from C4 to L6, a much greater extent of segmental drive to the CTMR than previously described. Stimulation of some subcutaneous paraspinal tissue can also elicit this reflex. Using a selective neurotoxin, we also demonstrate differential drive of the CTMR by trkA-expressing and non-expressing small diameter afferents. These observations highlight aspects of the organization of the CTMR system which make it attractive for studies of nociception and anesthesiology and plasticity of primary afferents, motoneurons, and the propriospinal system. We use the CTMR system to qualitatively and quantitatively demonstrate that experimental pharmacological treatments can be compared to controls applied either to the contralateral side or to another segment, with the remaining segments providing controls for systemic or other treatment effects. These data indicate the potential for using the CTMR system as both an invasive and non-invasive quantitative assessment tool providing improved statistical power and reduced animal use. PMID:23983104

  13. Sympathetic reflex control of skeletal muscle blood flow in patients with congestive heart failure: evidence for beta-adrenergic circulatory control

    SciTech Connect

    Kassis, E.; Jacobsen, T.N.; Mogensen, F.; Amtorp, O.

    1986-11-01

    Mechanisms controlling forearm muscle vascular resistance (FMVR) during postural changes were investigated in seven patients with severe congestive heart failure (CHF) and in seven control subjects with unimpaired left ventricular function. Relative brachioradial muscle blood flow was determined by the local /sup 133/Xe-washout technique. Unloading of baroreceptors with use of 45 degree upright tilt was comparably obtained in the patients with CHF and control subjects. Control subjects had substantially increased FMVR and heart rate to maintain arterial pressure whereas patients with CHF had decreased FMVR by 51 +/- 11% and had no increase in heart rate despite a fall in arterial pressure during upright tilt. The autoregulatory and local vasoconstrictor reflex responsiveness during postural changes in forearm vascular pressures were intact in both groups. In the patients with CHF, the left axillary nerve plexus was blocked by local anesthesia. No alterations in forearm vascular pressures were observed. This blockade preserved the local regulation of FMVR but reversed the vasodilator response to upright tilt as FMVR increased by 30 +/- 7% (p less than .02). Blockade of central neural impulses to this limb combined with brachial arterial infusions of phentolamine completely abolished the humoral vasoconstriction in the tilted position. Infusions of propranolol to the contralateral brachial artery that did not affect baseline values of heart rate, arterial pressure, or the local reflex regulation of FMVR reversed the abnormal vasodilator response to upright tilt as FMVR increased by 42 +/- 12% (p less than .02). Despite augmented baseline values, forearm venous but not arterial plasma levels of epinephrine increased in the tilted position, as did arteri rather than venous plasma concentrations of norepinephrine in these patients.

  14. The combined effects of transcutaneous electrical nerve stimulation (TENS) and stretching on muscle hardness and pressure pain threshold

    PubMed Central

    Karasuno, Hiroshi; Ogihara, Hisayoshi; Morishita, Katsuyuki; Yokoi, Yuka; Fujiwara, Takayuki; Ogoma, Yoshiro; Abe, Koji

    2016-01-01

    [Purpose] This study aimed to clarify the immediate effects of a combined transcutaneous electrical nerve stimulation and stretching protocol. [Subjects] Fifteen healthy young males volunteered to participate in this study. The inclusion criterion was a straight leg raising range of motion of less than 70 degrees. [Methods] Subjects performed two protocols: 1) stretching (S group) of the medial hamstrings, and 2) tanscutaneous electrical nerve stimulation (100 Hz) with stretching (TS group). The TS group included a 20-minute electrical stimulation period followed by 10 minutes of stretching. The S group performed 10 minutes of stretching. Muscle hardness, pressure pain threshold, and straight leg raising range of motion were analyzed to evaluate the effects. The data were collected before transcutaneous electrical nerve stimulation (T1), before stretching (T2), immediately after stretching (T3), and 10 minutes after stretching (T4). [Results] Combined transcutaneous electrical nerve stimulation and stretching had significantly beneficial effects on muscle hardness, pressure pain threshold, and straight leg raising range of motion at T2, T3, and T4 compared with T1. [Conclusion] These results support the belief that transcutaneous electrical nerve stimulation combined with stretching is effective in reducing pain and decreasing muscle hardness, thus increasing range of motion. PMID:27190439

  15. The combined effects of transcutaneous electrical nerve stimulation (TENS) and stretching on muscle hardness and pressure pain threshold.

    PubMed

    Karasuno, Hiroshi; Ogihara, Hisayoshi; Morishita, Katsuyuki; Yokoi, Yuka; Fujiwara, Takayuki; Ogoma, Yoshiro; Abe, Koji

    2016-04-01

    [Purpose] This study aimed to clarify the immediate effects of a combined transcutaneous electrical nerve stimulation and stretching protocol. [Subjects] Fifteen healthy young males volunteered to participate in this study. The inclusion criterion was a straight leg raising range of motion of less than 70 degrees. [Methods] Subjects performed two protocols: 1) stretching (S group) of the medial hamstrings, and 2) tanscutaneous electrical nerve stimulation (100 Hz) with stretching (TS group). The TS group included a 20-minute electrical stimulation period followed by 10 minutes of stretching. The S group performed 10 minutes of stretching. Muscle hardness, pressure pain threshold, and straight leg raising range of motion were analyzed to evaluate the effects. The data were collected before transcutaneous electrical nerve stimulation (T1), before stretching (T2), immediately after stretching (T3), and 10 minutes after stretching (T4). [Results] Combined transcutaneous electrical nerve stimulation and stretching had significantly beneficial effects on muscle hardness, pressure pain threshold, and straight leg raising range of motion at T2, T3, and T4 compared with T1. [Conclusion] These results support the belief that transcutaneous electrical nerve stimulation combined with stretching is effective in reducing pain and decreasing muscle hardness, thus increasing range of motion. PMID:27190439

  16. Development of the Stretch Reflex in the Newborn: Reciprocal Excitation and Reflex Irradiation.

    ERIC Educational Resources Information Center

    Myklebust, Barbara M.; Gottlieb, Gerald L.

    1993-01-01

    When tendon jerk reflexes were tested in seven newborns from one- to three-days old, stretch reflex responses in all major muscle groups of the lower limb were elicited. This "irradiation of reflexes" is a normal phenomenon in newborns, with the pathway becoming suppressed during normal maturation. In individuals with cerebral palsy, however, the…

  17. Jaw-Opening Reflex and Corticobulbar Motor Excitability Changes During Quiet Sleep in Non-Human Primates

    PubMed Central

    Yao, Dongyuan; Lavigne, Gilles J.; Lee, Jye-Chang; Adachi, Kazunori; Sessle, Barry J.

    2013-01-01

    Study Objective: To test the hypothesis that the reflex and corticobulbar motor excitability of jaw muscles is reduced during sleep. Design: Polysomnographic recordings in the electrophysiological study. Setting: University sleep research laboratories. Participants and Interventions: The reflex and corticobulbar motor excitability of jaw muscles was determined during the quiet awake state (QW) and quiet sleep (QS) in monkeys (n = 4). Measurements and Results: During QS sleep, compared to QW periods, both tongue stimulation-evoked jaw-opening reflex peak and root mean square amplitudes were significantly decreased with stimulations at 2-3.5 × thresholds (P < 0.001). The jaw-opening reflex latency during sleep was also significantly longer than during QW. Intracortical microstimulation (ICMS) within the cortical masticatory area induced rhythmic jaw movements at a stable threshold (≤ 60 μA) during QW; but during QS, ICMS failed to induce any rhythmic jaw movements at the maximum ICMS intensity used, although sustained jaw-opening movements were evoked at significantly increased threshold (P < 0.001) in one of the monkeys. Similarly, during QW, ICMS within face primary motor cortex induced orofacial twitches at a stable threshold (≤ 35 μA), but the ICMS thresholds were elevated during QS. Soon after the animal awoke, rhythmic jaw movements and orofacial twitches could be evoked at thresholds similar to those before QS. Conclusions: The results suggest that the excitability of reflex and corticobulbar-evoked activity in the jaw motor system is depressed during QS. Citation: Yao D; Lavigne GJ; Lee JC; Adachi K; Sessle BJ. Jaw-opening reflex and corticobulbar motor excitability changes during quiet sleep in non-human primates. SLEEP 2013;36(2):269-280. PMID:23372275

  18. The relationship between the kinematics of passive movement, the stretch of extensor muscles of the leg and the change induced in the gain of the soleus H reflex in humans.

    PubMed

    Cheng, J; Brooke, J D; Misiaszek, J E; Staines, W R

    1995-02-20

    The gain of the H reflex attenuates during passive stepping and pedalling movements of the leg. We hypothesized that the kinematics of the movement indirectly reflect the receptor origin of this attenuation. In the first experiment, H reflexes were evoked in soleus at 26 points in the cycle of slow, passive pedalling movement of the leg and at 13 points with the leg static (the ankle was always immobilized). Maximum inhibition occurred as the leg moved through its most flexed position (P < 0.05). Inhibition observed in the static leg was also strongest at this position (P < 0.05). The increase in inhibition was gradual during flexion movement, with rapid reversal of this increase during extension. In the second experiment, the length of stretch of the vasti muscles was modelled. Variable pedal crank lengths and revolutions per minute (rpm) altered leg joint displacements and angular velocities. Equivalent rates of stretch of the vasti, achieved through different combinations of joint displacements and velocities, elicited equivalent attenuations of mean reflex magnitudes in the flexed leg. Reflex gain exponentially related to rate of stretch (R2 = 0.98 P < 0.01). The results imply that gain attenuation of this spinal sensorimotor path arises from spindle discharge in heteronymous extensor muscles of knee and/or hip, concomitant with movement. PMID:7749757

  19. Molecular Crowding Defines a Common Origin for the Warburg Effect in Proliferating Cells and the Lactate Threshold in Muscle Physiology

    PubMed Central

    Vazquez, Alexei; Oltvai, Zoltán N.

    2011-01-01

    Aerobic glycolysis is a seemingly wasteful mode of ATP production that is seen both in rapidly proliferating mammalian cells and highly active contracting muscles, but whether there is a common origin for its presence in these widely different systems is unknown. To study this issue, here we develop a model of human central metabolism that incorporates a solvent capacity constraint of metabolic enzymes and mitochondria, accounting for their occupied volume densities, while assuming glucose and/or fatty acid utilization. The model demonstrates that activation of aerobic glycolysis is favored above a threshold metabolic rate in both rapidly proliferating cells and heavily contracting muscles, because it provides higher ATP yield per volume density than mitochondrial oxidative phosphorylation. In the case of muscle physiology, the model also predicts that before the lactate switch, fatty acid oxidation increases, reaches a maximum, and then decreases to zero with concomitant increase in glucose utilization, in agreement with the empirical evidence. These results are further corroborated by a larger scale model, including biosynthesis of major cell biomass components. The larger scale model also predicts that in proliferating cells the lactate switch is accompanied by activation of glutaminolysis, another distinctive feature of the Warburg effect. In conclusion, intracellular molecular crowding is a fundamental constraint for cell metabolism in both rapidly proliferating- and non-proliferating cells with high metabolic demand. Addition of this constraint to metabolic flux balance models can explain several observations of mammalian cell metabolism under steady state conditions. PMID:21559344

  20. Muscle repositioning: combining subjective and objective feedbacks in the teaching and practice of a reflex-based myofascial release technique.

    PubMed

    Bertolucci, Luiz Fernando

    2010-01-01

    Muscle Repositioning (MR) is a new style of myofascial release that elicits involuntary motor reactions detectable by electromyography. This article describes the principal theoretical and practical concepts of MR, and summarizes a workshop presented October 31, 2009, after the Second International Fascia Research Congress, held at Vrije Universitiet, Amsterdam.The manual mechanical input of MR integrates the client's body segments into a block, which is evident as a result of the diagnostic manual oscillations the practitioner imparts to the client's body. Segmental integration is achieved when the client's body responds as a unit to the oscillatory assessment. It appears that manually sustaining the condition of segmental integration evokes involuntary muscle reactions, which reactions might correspond to mechanisms that maintain homeostasis, such as pandiculation. It might be that these reactions are part of the MR mechanism of action and underlie its clinically observed efficacy in the treatment of musculoskeletal disorders.For the practitioner and the client alike, segmental integration provides unique sensations. In teaching MR, these paired sensations can be used as kinesthetic feedback resources, because quality of touch can be guided by the client's reported sensations, which should match the practitioner's sensations. Another form of feedback with respect to quality of touch is the visually discernable degree of segmental integration. Finally, because the involuntary motor activity elicited by the MR touch can be objectively monitored through electromyography and possibly other instrumented measurements, the MR approach might yield objectivity, precision, and reproducibility-features seldom found in manual therapies. PMID:21589699

  1. Pulmonary Rehabilitation Using Modified Threshold Inspiratory Muscle Trainer (IMT) in Patients with Tetraplegia.

    PubMed

    Yasar, Funda; Tasci, Canturk; Savci, Sema; Tozkoparan, Ergun; Deniz, Omer; Balkan, Arzu; Bilgic, Hayati

    2012-01-01

    It is aimed to present the usefulness of inspiratory muscle trainer (IMT) in treatment of a 20-year-old male patient with diaphragmatic paralysis and tetraplegia due to spinal cord injury (SCI), and supporting effect of IMT in recovering from respiratory failure by rendering his diaphragm functions. The treatment was applied through the tracheostomy cannula by a modified IMT device. After applying IMT for three weeks, it was observed that the diaphragm recovered its functions in electromyography (EMG) test. As a result, in this study, we present a case where a patient could live without any respiratory device for the rest of his life with the help of modified IMT. PMID:22536264

  2. Neural control of rhythmic, cyclical human arm movement: task dependency, nerve specificity and phase modulation of cutaneous reflexes

    PubMed Central

    Zehr, E Paul; Kido, Aiko

    2001-01-01

    The organization and pattern of cutaneous reflex modulation during rhythmic cyclical movements of the human upper limbs has received much less attention than that afforded the lower limb. Our working hypothesis is that control mechanisms underlying the modulation of cutaneous reflex amplitude during rhythmic arm movement are similar to those that control reflex modulation in the leg. Thus, we hypothesized that cutaneous reflexes would show task dependency and nerve specificity in the upper limb during rhythmic cyclical arm movement as has been demonstrated in the human lower limb. EMG was recorded from 10 muscles crossing the human shoulder, elbow and wrist joints while bilateral whole arm rhythmic cyclical movements were performed on a custom-made, hydraulic apparatus. Cutaneous reflexes were evoked with trains (5× 1.0 ms pulses at 300 Hz) of electrical stimulation delivered at non-noxious intensities (∼2× threshold for radiating parasthesia) to the superficial radial, median and ulnar nerves innervating the hand. Cutaneous reflexes were typically modulated with the movement cycle (i.e. phase dependency was observed). There was evidence for nerve specificity of cutaneous reflexes during rhythmic movement of the upper limbs. Task-dependent modulation was also seen as cutaneous reflexes were of larger amplitude or inhibitory (reflex reversal) during arm cycling as compared to static contraction. While there are some differences in the patterns of cutaneous reflex modulation seen between the arms and legs, it is concluded that cutaneous reflexes are modulated similarly in the upper and lower limbs implicating similar motor control mechanisms. PMID:11744775

  3. A reflex resonance model of vocal vibrato

    NASA Astrophysics Data System (ADS)

    Titze, Ingo R.; Story, Brad; Smith, Marshall; Long, Russel

    2002-05-01

    A reflex mechanism with a long latency (>40 ms) is implicated as a plausible cause of vocal vibrato. At least one pair of agonist-antagonist muscles that can change vocal-fold length is needed, such as the cricothyroid muscle paired with the thyroarytenoid muscle, or the cricothyroid muscle paired with the lateral cricoarytenoid muscle or a strap muscle. Such an agonist-antagonist muscle pair can produce negative feedback instability in vocal-fold length with this long reflex latency, producing oscillations on the order of 5-7 Hz. It is shown that singers appear to increase the gain in the reflex loop to cultivate the vibrato, which grows out of a spectrum of 0-15-Hz physiologic tremors in raw form.

  4. The initial effects of an upper extremity neural mobilization technique on muscle fatigue and pressure pain threshold of healthy adults: a randomized control trial

    PubMed Central

    Kim, Myoung-Kwon; Cha, Hyun-Gyu; Ji, Sang Gu

    2016-01-01

    [Purpose] The purpose of this study was to determine the effects of an upper extremity neural mobilization technique on delayed onset muscle soreness. [Subjects] Forty-five healthy subjects were randomly assigned to two groups: a nerve mobilization group (experimental) and a control group. [Methods] The subjects of the experimental group were administered a median nerve mobilization technique and ultrasound for the biceps brachii muscle. The subjects in the control group were only administered ultrasound for the biceps brachii muscle. Muscle fatigue and the pressure pain threshold were assessed before and after the intervention. [Results] The experimental group showed significant improvements in all variables, compared to pre-intervention. Furthermore, the control group showed significant improvements in the pressure pain threshold, compared to pre-intervention. Significant differences in the post-intervention gains in muscle fatigue and pressure pain threshold were found between the experimental group and the control group. [Conclusion] Application of the upper extremity neural mobilization technique is considered to have a positive effect on recovery from delayed onset muscle soreness. PMID:27134351

  5. The vestibulosympathetic reflex in humans: neural interactions between cardiovascular reflexes

    NASA Technical Reports Server (NTRS)

    Ray, Chester A.; Monahan, Kevin D.

    2002-01-01

    1. Over the past 5 years, there has been emerging evidence that the vestibular system regulates sympathetic nerve activity in humans. We have studied this issue in humans by using head-down rotation (HDR) in the prone position. 2. These studies have clearly demonstrated increases in muscle sympathetic nerve activity (MSNA) and calf vascular resistance during HDR. These responses are mediated by engagement of the otolith organs and not the semicircular canals. 3. However, differential activation of sympathetic nerve activity has been observed during HDR. Unlike MSNA, skin sympathetic nerve activity does not increase with HDR. 4. Examination of the vestibulosympathetic reflex with other cardiovascular reflexes (i.e. barorereflexes and skeletal muscle reflexes) has shown an additive interaction for MSNA. 5. The additive interaction between the baroreflexes and vestibulosympathetic reflex suggests that the vestibular system may assist in defending against orthostatic challenges in humans by elevating MSNA beyond that of the baroreflexes. 6. In addition, the further increase in MSNA via otolith stimulation during isometric handgrip, when arterial pressure is elevated markedly, indicates that the vestibulosympathetic reflex is a powerful activator of MSNA and may contribute to blood pressure and flow regulation during dynamic exercise. 7. Future studies will help evaluate the importance of the vestibulosympathetic reflex in clinical conditions associated with orthostatic hypotension.

  6. Inspiratory muscle training in chronic airflow limitation: comparison of two different training loads with a threshold device.

    PubMed

    Lisboa, C; Muñoz, V; Beroiza, T; Leiva, A; Cruz, E

    1994-07-01

    The usefulness of inspiratory muscle training (IMT) in chronic airflow limitation (CAL) patients is a controversial issue, mainly due to differences in the training load. To further evaluate this aspect, we studied the effect of the magnitude of the load using a threshold pressure trainer. Ten CAL patients (5 males, 5 females) 67 +/- 2 yrs (mean +/- SEM) and forced expiratory volume in one second (FEV1) 36 +/- 2% pred, were trained for 30 min a day using a load of 30% of their maximal inspiratory mouth pressure (PImax) (Group 1). Another 10 CAL patients (5 males, 5 females), 73 +/- 2 yrs and FEV1 37 +/- 2% pred), were trained using only 12% of their PImax (Group 2). Training was assessed by PImax, inspiratory muscle power output (IMPO), sustainable inspiratory pressure (SIP), maximal inspiratory flow rate (VImax), pattern of breathing during loaded breathing, Mahler's dyspnoea score, and the 6 min walking distance (6MWD). After 5 weeks of training, Group 1 exhibited significant increments in: PImax (34 +/- 11%); IMPO (92 +/- 16%); SIP (36 +/- 9%); and VImax (34 +/- 13%). Dyspnoea was also reduced, and the 6MWD increased by 48 +/- 22 m. We observed no significant changes in Group 2. During loaded breathing, Group 1 showed a significant increment in tidal volume (VT) and mean inspiratory flow (VT/TI), and a reduction in inspiratory time (TI). In Group 2, VT and VT/TI also increased significantly, but the breathing frequency increased with a reduction of expiratory time.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7925905

  7. Are Electrically Induced Muscle Cramps Able to Increase the Cramp Threshold Frequency, When Induced Once a Week?

    PubMed Central

    Link, Tobias Walter; Montag, Johannes Caspar Konrad; McCourt, Molly Leigh; Mester, Joachim

    2015-01-01

    The cramp threshold frequency (CTF) is known to be positively correlated with the individual cramp susceptibility. Here we assessed CTF changes after two bouts of electrically induced muscle cramps (EIMCs). The EIMCs (6×5 sec) were unilaterally induced twice (separated by one week) in the gastrocnemius of an intervention group (n=8), while 5 participants served as control. The CTF increased from 25.1±4.6 Hz at baseline to 31.4±9.0 Hz and 31.7±8.5 Hz 24 h after bout 1 and 2 (P<0.05). Thereafter, the CTF declined following both bouts to reach values of 28.0±6.7 Hz and 29.1±7.7 Hz after 72 h after bout 1 and 2. Creatine kinase (CK) activity and perceived discomfort during cramps was lower after bout 2 (P<0.05). CTF, CK, and discomfort did not change in CG. That is, a single bout of EIMCs induces a 24 h CTF increment and a second bout sustains this effect, while perceived discomfort and muscle damage decreases. This short term effect may help athletes to reduce the cramp susceptibility for an important match. PMID:26605029

  8. Muscle metaboreflex activation during dynamic exercise vasoconstricts ischemic active skeletal muscle.

    PubMed

    Kaur, Jasdeep; Machado, Tiago M; Alvarez, Alberto; Krishnan, Abhinav C; Hanna, Hanna W; Altamimi, Yasir H; Senador, Danielle; Spranger, Marty D; O'Leary, Donal S

    2015-12-15

    Metabolite accumulation due to ischemia of active skeletal muscle stimulates group III/IV chemosensitive afferents eliciting reflex increases in arterial blood pressure and sympathetic activity, termed the muscle metaboreflex. We and others have previously demonstrated sympathetically mediated vasoconstriction of coronary, renal, and forelimb vasculatures with muscle metaboreflex activation (MMA). Whether MMA elicits vasoconstriction of the ischemic muscle from which it originates is unknown. We hypothesized that the vasodilation in active skeletal muscle with imposed ischemia becomes progressively restrained by the increasing sympathetic vasoconstriction during MMA. We activated the metaboreflex during mild dynamic exercise in chronically instrumented canines via graded reductions in hindlimb blood flow (HLBF) before and after α1-adrenergic blockade [prazosin (50 μg/kg)], β-adrenergic blockade [propranolol (2 mg/kg)], and α1 + β-blockade. Hindlimb resistance was calculated as femoral arterial pressure/HLBF. During mild exercise, HLBF must be reduced below a threshold level before the reflex is activated. With initial reductions in HLBF, vasodilation occurred with the imposed ischemia. Once the muscle metaboreflex was elicited, hindlimb resistance increased. This increase in hindlimb resistance was abolished by α1-adrenergic blockade and exacerbated after β-adrenergic blockade. We conclude that metaboreflex activation during submaximal dynamic exercise causes sympathetically mediated α-adrenergic vasoconstriction in ischemic skeletal muscle. This limits the ability of the reflex to improve blood flow to the muscle. PMID:26475591

  9. Vestibulo-spinal reflex mechanisms

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.

    1981-01-01

    The specific objectives of experiments designed to investigate postural reflex behavior during sustained weightlessness are discussed. The first is to investigate, during prolonged weightlessness with Hoffmann response (H-reflex) measurement procedures, vestibulo-spinal reflexes associated with vestibular (otolith) responses evoked during an applied linear acceleration. This objective includes not only an evaluation of otolith-induced changes in a major postural muscle but also an investigation with this technique of the adaptive process of the vestibular system and spinal reflex mechanisms to this unique environment. The second objective is to relate space motion sickness to the results of this investigation. Finally, a return to the vestibulo-spinal and postural reflexes to normal values following the flight will be examined. The flight experiment involves activation of nerve tissue (tibial N) with electrical shock and the recording of resulting muscle activity (soleus) with surface electrodes. Soleus/spinal H-reflex testing procedures will be used in conjuction with linear acceleration through the subject's X-axis.

  10. Cutaneous reflex modulation and self-induced reflex attenuation in cerebellar patients.

    PubMed

    Hoogkamer, Wouter; Van Calenbergh, Frank; Swinnen, Stephan P; Duysens, Jacques

    2015-02-01

    Modulation of cutaneous reflexes is important in the neural control of walking, yet knowledge about underlying neural pathways is still incomplete. Recent studies have suggested that the cerebellum is involved. Here we evaluated the possible roles of the cerebellum in cutaneous reflex modulation and in attenuation of self-induced reflexes. First we checked whether leg muscle activity during walking was similar in patients with focal cerebellar lesions and in healthy control subjects. We then recorded cutaneous reflex activity in leg muscles during walking. Additionally, we compared reflexes after standard (computer triggered) stimuli with reflexes after self-induced stimuli for both groups. Biceps femoris and gastrocnemius medialis muscle activity was increased in the patient group compared with the control subjects, suggesting a coactivation strategy to reduce instability of gait. Cutaneous reflex modulation was similar between healthy control subjects and cerebellar patients, but the latter appeared less able to attenuate reflexes to self-induced stimuli. This suggests that the cerebellum is not primarily involved in cutaneous reflex modulation but that it could act in attenuation of self-induced reflex responses. The latter role in locomotion would be consistent with the common view that the cerebellum predicts sensory consequences of movement. PMID:25392164

  11. Cutaneous reflex modulation and self-induced reflex attenuation in cerebellar patients

    PubMed Central

    Van Calenbergh, Frank; Swinnen, Stephan P.; Duysens, Jacques

    2014-01-01

    Modulation of cutaneous reflexes is important in the neural control of walking, yet knowledge about underlying neural pathways is still incomplete. Recent studies have suggested that the cerebellum is involved. Here we evaluated the possible roles of the cerebellum in cutaneous reflex modulation and in attenuation of self-induced reflexes. First we checked whether leg muscle activity during walking was similar in patients with focal cerebellar lesions and in healthy control subjects. We then recorded cutaneous reflex activity in leg muscles during walking. Additionally, we compared reflexes after standard (computer triggered) stimuli with reflexes after self-induced stimuli for both groups. Biceps femoris and gastrocnemius medialis muscle activity was increased in the patient group compared with the control subjects, suggesting a coactivation strategy to reduce instability of gait. Cutaneous reflex modulation was similar between healthy control subjects and cerebellar patients, but the latter appeared less able to attenuate reflexes to self-induced stimuli. This suggests that the cerebellum is not primarily involved in cutaneous reflex modulation but that it could act in attenuation of self-induced reflex responses. The latter role in locomotion would be consistent with the common view that the cerebellum predicts sensory consequences of movement. PMID:25392164

  12. Electrical Stimulation of Sacral Dermatomes Can Suppress Aberrant Urethral Reflexes in Felines with Chronic Spinal Cord Injury

    PubMed Central

    McCoin, Jaime L.; Bhadra, Narendra; Gustafson, Kenneth J.

    2012-01-01

    Aims Uncoordinated reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurologic injury. Patterned stimulation of sacral afferent pathways can reduce abnormal EUS reflexes after acute SCI; however, effectiveness following chronic SCI is unknown. Methods Four adult male cats were implanted with bilateral extradural sacral root electrodes to allow bladder activation and underwent subsequent spinal transection (T10–12). Nine weeks after SCI urethral and bladder pressures were recorded with and without sacral afferent stimulation. Surface electrodes were applied to sacral and lumbar dermatomes and stimulus amplitude set below the muscle fasciculation threshold. The stimulation pattern was varied by on/off times of fixed frequency at each location. Results Reflexive EUS contractions were observed in all animals after chronic SCI. Patterned sacral dermatome stimulation reduced EUS reflex rate and amplitude in 2 of 4 cats. Suppression was dependent on both the stimulus location and pattern. Sacral locations and a stimulation pattern of (0.75 seconds on, 0.25 seconds off, 20 Hz) were effective in both responder animals. Conclusions Patterned sacral dermatome stimulation can reduce urethral abnormal reflexes following chronic SCI. Reflex suppression is dependent on both the stimulation location and stimulus pattern. Reduction of reflexive EUS activity after chronic SCI with this non-destructive and non-invasive approach may provide an advance for the treatment of detrusor-sphincter-dyssynergia. PMID:22674730

  13. Movement-induced gain modulation of somatosensory potentials and soleus H-reflexes evoked from the leg. II. Correlation with rate of stretch of extensor muscles of the leg.

    PubMed

    Staines, W R; Brooke, J D; Misiaszek, J E; McIlroy, W E

    1997-06-01

    Attenuation of initial somatosensory evoked potential (SEP) gain becomes more pronounced with increased rates of movement. Manipulation of the range of movement also might alter the SEP gain. It could alter joint receptor discharge; it should alter the discharge of muscle stretch receptors. We hypothesized that: (1) SEP gain reduction correlates with both the range and the rate of movement, and (2) manipulation of range and rate of movement to achieve similar estimated rates of stretch of a leg extensor muscle group (the vasti) results in similar decreases in SEP gain. SEPs from Cz', referenced to Fpz' (2 cm caudal to Cz and Fpz, respectively, according to the International 10-20 System), along with soleus H-reflexes were elicited by electrical stimulation of the tibial nerve at the popliteal fossa. Stable magnitudes of small M-waves indicated stability of stimulation. A modified cycle ergometer with an adjustable pedal crank and electric motor was used to passively rotate the right leg over three ranges (producing estimated vasti stretch of 12, 24 and 48 mm) and four rates (0, 20, 40 and 80 rpm) of movement. Two experiments were conducted. Ranges and rates of pedalling movement were combined to produce two or three equivalent estimated rates of tissue stretch of the vasti muscles at each of 4, 16, 32 and 64 mm/s. Tibial nerve stimuli were delivered when the knee was moved through its most flexed position and the hip was nearing its most flexed position. Means of SEP, H-reflex and M-wave magnitudes were tested for rate and range effects (ANOVA). A priori contrasts compared means produced by equivalent estimated rates of vasti stretch. Increasing the rate of movement significantly increased the attenuation of SEP and H-reflex gain (P<0.05). Increasing the range of movement also significantly increased these gain attenuations (P<0.05). Combining these to achieve equivalent rates of stretch, through different combinations of rate and range, resulted in equivalent

  14. Asthma as an axon reflex.

    PubMed

    Barnes, P J

    1986-02-01

    In asthma, damage to airway epithelium, possibly caused by eosinophil products, exposes C-fibre afferent nerve endings. Stimulation of these endings by inflammatory mediators such as bradykinin may result in an axon (local) reflex with antidromic conduction down afferent nerve collaterals and release of sensory neuropeptides such as substance P, neurokinin A, and calcitonin gene-related peptide. These peptides are potent inducers of airway smooth muscle contraction, bronchial oedema, extravasation of plasma, mucus hypersecretion, and possibly inflammatory cell infiltration and secretion. Thus, axon reflexes could account for at least some of the pathophysiology of asthma and this concept might lead to new strategies for treatment. PMID:2418322

  15. Reflexives in Mohawk.

    ERIC Educational Resources Information Center

    Bonvillain, Nancy

    1994-01-01

    This paper presents an analysis of the meanings and uses of two reflexive morphemes in the Mohawk language. Reflexive "atat" is shown to have both reflexive and reciprocal meanings. It is also realized in kinship terms and in the transitive pronominal prefix "yutat." Semi-reflexive "at" has some reflexive functions, and can mark middle voice and…

  16. Patterning of somatosympathetic reflexes

    NASA Technical Reports Server (NTRS)

    Kerman, I. A.; Yates, B. J.

    1999-01-01

    In a previous study, we reported that vestibular nerve stimulation in the cat elicits a specific pattern of sympathetic nerve activation, such that responses are particularly large in the renal nerve. This patterning of vestibulosympathetic reflexes was the same in anesthetized and decerebrate preparations. In the present study, we report that inputs from skin and muscle also elicit a specific patterning of sympathetic outflow, which is distinct from that produced by vestibular stimulation. Renal, superior mesenteric, and lumbar colonic nerves respond most strongly to forelimb and hindlimb nerve stimulation (approximately 60% of maximal nerve activation), whereas external carotid and hypogastric nerves were least sensitive to these inputs (approximately 20% of maximal nerve activation). In contrast to vestibulosympathetic reflexes, the expression of responses to skin and muscle afferent activation differs in decerebrate and anesthetized animals. In baroreceptor-intact animals, somatosympathetic responses were strongly attenuated (to <20% of control in every nerve) by increasing blood pressure levels to >150 mmHg. These findings demonstrate that different types of somatic inputs elicit specific patterns of sympathetic nerve activation, presumably generated through distinct neural circuits.

  17. Variability in Hoffmann and tendon reflexes in healthy male subjects

    NASA Technical Reports Server (NTRS)

    Good, E.; Do, S.; Jaweed, M.

    1992-01-01

    There is a time dependent decrease in amplitude of H- and T-reflexes during Zero-G exposure and subsequently an increase in the amplitude of the H-reflex 2-4 hours after return to a 1-G environment. These alterations have been attributed to the adaptation of the human neurosensory system to gravity. The Hoffman reflex (H-reflex) is an acknowledged method to determine the integrity of the monosynaptic reflex arc. However deep tendon reflexes (DTR's or T-reflexes), elicited by striking the tendon also utilize the entire reflex arc. The objective of this study was to compare the variability in latency and amplitude of the two reflexes in healthy subjects. Methods: Nine healthy male subjects, 27-43 years in age, 161-175 cm in height plus 60-86 Kg in weight, underwent weekly testing for four weeks with a Dan-Tec EMG counterpoint EMG system. Subjects were studied prone and surface EMG electrodes were placed on the right and left soleus muscles. The H-reflex was obtained by stimulating the tibial nerve in the politeal fossa with a 0.2 msec square wave pulse delivered at 2 Hz until the maximum H-reflex was obtained. The T-reflex was invoked by tapping the achilles tendon with a self triggering reflex hammer connected to the EMG system. The latencies and amplitudes for the H- and T-reflexes were measured. Results: These data indicate that the amplitudes of these reflexes varied considerably. However, latencies to invoked responses were consistent. The latency of the T-reflex was approximately 3-5 msec longer than the H-reflex. Conclusion: The T-reflex is easily obtained, requires less time, and is more comfortable to perform. Qualitative data can be obtained by deploying self triggering, force plated reflex hammers both in the 1-G and Zero-G environment.

  18. Convergence in Reflex Pathways from Multiple Cutaneous Nerves Innervating the Foot Depends upon the Number of Rhythmically Active Limbs during Locomotion

    PubMed Central

    Nakajima, Tsuyoshi; Mezzarane, Rinaldo A.; Hundza, Sandra R.; Komiyama, Tomoyoshi; Zehr, E. Paul

    2014-01-01

    Neural output from the locomotor system for each arm and leg influences the spinal motoneuronal pools directly and indirectly through interneuronal (IN) reflex networks. While well documented in other species, less is known about the functions and features of convergence in common IN reflex system from cutaneous afferents innervating different foot regions during remote arm and leg movement in humans. The purpose of the present study was to use spatial facilitation to examine possible convergence in common reflex pathways during rhythmic locomotor limb movements. Cutaneous reflexes were evoked in ipsilateral tibialis anterior muscle by stimulating (in random order) the sural nerve (SUR), the distal tibial nerve (TIB), and combined simultaneous stimulation of both nerves (TIB&SUR). Reflexes were evoked while participants performed rhythmic stepping and arm swinging movement with both arms and the leg contralateral to stimulation (ARM&LEG), with just arm movement (ARM) and with just contralateral leg movement (LEG). Stimulation intensities were just below threshold for evoking early latency (<80 ms to peak) reflexes. For each stimulus condition, rectified EMG signals were averaged while participants held static contractions in the stationary (stimulated) leg. During ARM&LEG movement, amplitudes of cutaneous reflexes evoked by combined TIB&SUR stimulation were significantly larger than simple mathematical summation of the amplitudes evoked by SUR or TIB alone. Interestingly, this extra facilitation seen during combined nerve stimulation was significantly reduced when performing ARM or LEG compared to ARM&LEG. We conclude that locomotor rhythmic limb movement induces excitation of common IN reflex pathways from cutaneous afferents innervating different foot regions. Importantly, activity in this pathway is most facilitated during ARM&LEG movement. These results suggest that transmission in IN reflex pathways is weighted according to the number of limbs directly engaged

  19. Mechanism of the vibration paradox: excitatory and inhibitory effects of tendon vibration on single soleus muscle motor units in man

    PubMed Central

    Desmedt, John E.; Godaux, Emile

    1978-01-01

    1. The parameters of presynaptic inhibition of the Ia spindle afferents from soleus muscle by vibration have been investigated. The inhibitory effects increase with the amplitude of vibration, but decrease when the vibration frequency is increased. 2. The monosynaptic reflex threshold of twenty-one single soleus motor units activated in the H (Hoffmann) reflex by a single electrical stimulus to the posterior tibial nerve was estimated quantitatively and expressed in relation to the size of the simultaneously recorded H reflex. 3. A parametric study of the effects of various Achilles tendon vibrations on the reflex threshold of the single soleus motor units indicated that their order of derecruitment is concordant with their rank order for activation in the phasic reflexes of the soleus. The last recruited motoneurones are the most susceptible to being silenced by steady vibration. 4. Muscle vibration progressively recruits single motor units according to the motoneurone size principle through polysynaptic proprioceptive pathways. However the presynaptic inhibition of Ia spindle afferents simultaneously induced by the vibration works in reverse on the same rank order of motoneurones of the soleus spinal pool, thereby limiting the polysynaptic recruitment of units in the tonic vibration reflex while depressing the autogenic phasic proprioceptive reflexes. These mechanisms elucidate the so-called vibration paradox and extend the size principle of Henneman to presynaptic inhibitory effects. PMID:154563

  20. Whole-body vibration-induced muscular reflex: Is it a stretch-induced reflex?

    PubMed Central

    Cakar, Halil Ibrahim; Cidem, Muharrem; Sebik, Oguz; Yilmaz, Gizem; Karamehmetoglu, Safak Sahir; Kara, Sadik; Karacan, Ilhan; Türker, Kemal Sıtkı

    2015-01-01

    [Purpose] Whole-body vibration (WBV) can induce reflex responses in muscles. A number of studies have reported that the physiological mechanisms underlying this type of reflex activity can be explained by reference to a stretch-induced reflex. Thus, the primary objective of this study was to test whether the WBV-induced muscular reflex (WBV-IMR) can be explained as a stretch-induced reflex. [Subjects and Methods] The present study assessed 20 healthy males using surface electrodes placed on their right soleus muscle. The latency of the tendon reflex (T-reflex) as a stretch-induced reflex was compared with the reflex latency of the WBV-IMR. In addition, simulations were performed at 25, 30, 35, 40, 45, and 50 Hz to determine the stretch frequency of the muscle during WBV. [Results] WBV-IMR latency (40.5 ± 0.8 ms; 95% confidence interval [CI]: 39.0–41.9 ms) was significantly longer than T-reflex latency (34.6 ± 0.5 ms; 95% CI: 33.6–35.5 ms) and the mean difference was 6.2 ms (95% CI of the difference: 4.7–7.7 ms). The simulations performed in the present study demonstrated that the frequency of the stretch signal would be twice the frequency of the vibration. [Conclusion] These findings do not support the notion that WBV-IMR can be explained by reference to a stretch-induced reflex. PMID:26310784

  1. Distribution and threshold expression of the tRNA[sup Lys] mutation in skeletal muscle of patients with myoclonic epilepsy and ragged-red fibers (MERRF)

    SciTech Connect

    Boulet, L.; Karpati, G. ); Shoubridge, E.A. McGill Univ., Montreal, Quebec )

    1992-12-01

    The authors investigated the distribution and expression of mutant mtDNAs carrying the A-to-G mutation at position 8344 in the tRNA[sup Lys] gene in the skeletal muscle of four patients with myoclonus epilepsy and ragged-red fibers (MERRF). The proportion of mutant genomes was greater than 80% of total mtDNAs in muscle samples of all patients and was associated with a decrease in the activity of cytochrome c oxidase (COX). The vast majority of myoblasts, cloned from the satellite-cell population in the same muscles, were homoplasmic for the mutation. The overall proportion of mutant mtDNAs in this population was similar to that in differentiated muscle, suggesting that the ratio of mutant to wild-type mtDNAs in skeletal muscle is determined either in the ovum or during early development and changes little with age. Translation of all mtDNA-encoded genes was severely depressed in homoplasmic mutant myoblast clones but not in heteroplasmic or wild-type clones. The threshold for biochemical expression of the mutation was determined in heteroplasmic myotubes formed by fusion of different proportions of mutant and wild-type myoblasts. The magnitude of the decrease in translation in myotubes containing mutant mtDNAs was protein specific. Complex I and IV subunits were more affected than complex V subunits, and there was a rough correlation with both protein size and number of lysine residues. Approximately 15% wild-type mtDNAs restored translation and COX activity to near normal levels. These results show that the A-to-G substitution in tRNA[sup Lys] is a functionally recessive mutation that can be rescued by intraorganellar complementation with a small proportion of wild-type mtDNAs and explain the steep threshold for expression of the MERRF clinical phenotype. 40 refs., 7 figs., 2 tabs.

  2. Excess VO2 during ramp exercise is positively correlated to intercostal muscles deoxyhemoglobin levels above the gas exchange threshold in young trained cyclists.

    PubMed

    Oueslati, Ferid; Girard, Olivier; Tabka, Zouhair; Ahmaidi, Said

    2016-07-01

    We assessed respiratory muscles oxygenation responses during a ramp exercise to exhaustion and further explored their relationship with the non-linear increase of VO2 (VO2 excess) observed above the gas-exchange threshold. Ten male cyclists completed a ramp exercise to exhaustion on an electromagnetically braked cycle-ergometer with a rate of increment of 30Wmin(-1) with continuous monitoring of expired gases (breath-by-breath) and oxygenation status of intercostal muscles. Maximal inspiratory and expiratory pressure measurements were taken at rest and at exhaustion. The VO2 excess represents the difference between VO2max observed and VO2max expected using linear equation between the VO2 and the intensity before gas-exchange threshold. The deoxyhemoglobin remained unchanged until 60% of maximal aerobic power (MAP) and thereafter increased significantly by 37±18% and 40±22% at 80% and 100% of MAP, respectively. Additionally, the amplitude of deoxyhemoglobin increase between 60 and 100% of MAP positively correlated with the VO2 excess (r=0.69, p<0.05). Compared to exercise start, the oxygen tissue saturation index decreased from 80% of MAP (-4.8±3.2%, p<0.05) onwards. At exhaustion, maximal inspiratory and expiratory pressures declined by 7.8±16% and 12.6±10% (both p<0.05), respectively. In summary, our results suggest a significant contribution of respiratory muscles to the VO2 excess phenomenon. PMID:26996071

  3. Reflexives in Japanese

    ERIC Educational Resources Information Center

    Kishida, Maki

    2011-01-01

    The purpose of this dissertation is to reconsider reflexives in Japanese through the following three steps: (a) separation of genuine reflexive elements from elements that are confounded as reflexives, (b) classification of reflexive anaphors into subtypes based on their semantic difference, and (c) classification of predicates that occur with…

  4. Reflexives in Veracruz Huastec.

    ERIC Educational Resources Information Center

    Constable, Peter G.

    A study examines various Huastec clause types that are reflexive in some sense, including ordinary reflexives, which involve co-reference. Two mutually exclusive morphosyntactic devices are used in Huastec: reflexive pronouns and verbal morphology. In this way, Huastec is like various European languages. Clauses involving reflexive pronouns and…

  5. Voluntary modulation of human stretch reflexes.

    PubMed

    Ludvig, Daniel; Cathers, Ian; Kearney, Robert E

    2007-11-01

    It has been postulated that the central nervous system (CNS) can tune the mechanical behavior of a joint by altering reflex stiffness in a task-dependant manner. However, most of the evidence supporting this hypothesis has come from the analysis of H-reflexes or electromyogram (EMG) responses. Changes in overall stiffness have been documented but, as yet, there is no direct evidence that the CNS can control reflex stiffness independently of the intrinsic stiffness. We have used a novel identification algorithm to estimate intrinsic and reflex stiffness and feed it back to subjects in real-time. Using this biofeedback, subjects could learn to control reflex stiffness independently of intrinsic stiffness. At low torque levels, subjects could vary their reflex stiffness gain by a factor of 4, while maintaining elastic stiffness and torque constant. EMG measurements confirmed that the contraction levels of the ankle muscles remained constant. Further experiments showed that subjects could change their reflexes rapidly on command. Thus, we conclude that the CNS can control reflex stiffness independently and so has great flexibility in adjusting the mechanical properties of a joint to meet functional requirements. PMID:17628793

  6. Role of stretch reflex in voluntary movements. [of human foot

    NASA Technical Reports Server (NTRS)

    Gottlieb, G. L.; Agarwal, G. C.

    1975-01-01

    The stretch reflex is often described as a spinal servomechanism, a device for assisting in the regulation of muscle length. Observation of the EMG response to mechanical interruption of voluntary movements fails to demonstrate a significant role for spinal reflexes at 40 msec latency. Two functional responses with latencies of 120 msec and 200 msec, implying supraspinal mediation, are observed.

  7. Electrophysiological Correlates of the Threshold to Detection of Passive Motion: An Investigation in Professional Volleyball Athletes with and without Atrophy of the Infraspinatus Muscle

    PubMed Central

    Salles, José Inácio; Cossich, Victor Rodrigues Amaral; Amaral, Marcus Vinicius; Monteiro, Martim T.; Cagy, Maurício; Motta, Geraldo; Velasques, Bruna; Piedade, Roberto; Ribeiro, Pedro

    2013-01-01

    The goal of the present study is to compare the electrophysiological correlates of the threshold to detection of passive motion (TTDPM) among three groups: healthy individuals (control group), professional volleyball athletes with atrophy of the infraspinatus muscle on the dominant side, and athletes with no shoulder pathologies. More specifically, the study aims at assessing the effects of infraspinatus muscle atrophy on the cortical representation of the TTDPM. A proprioception testing device (PTD) was used to measure the TTDPM. The device passively moved the shoulder and participants were instructed to respond as soon as movement was detected (TTDPM) by pressing a button switch. Response latency was established as the delay between the stimulus (movement) and the response (button press). Electroencephalographic (EEG) and electromyographic (EMG) activities were recorded simultaneously. An analysis of variance (ANOVA) and subsequent post hoc tests indicated a significant difference in latency between the group of athletes without the atrophy when compared both to the group of athletes with the atrophy and to the control group. Furthermore, distinct patterns of cortical activity were observed in the three experimental groups. The results suggest that systematically trained motor abilities, as well as the atrophy of the infraspinatus muscle, change the cortical representation of the different stages of proprioceptive information processing and, ultimately, the cortical representation of the TTDPM. PMID:23484136

  8. Vestibular reflexes of otolith origin

    NASA Technical Reports Server (NTRS)

    Wilson, Victor J.

    1988-01-01

    The vestibular system and its role in the maintenance of posture and in motion sickness is investigated using cats as experimental subjects. The assumption is that better understanding of the physiology of vestibular pathways is not only of intrinsic value, but will help to explain and eventually alleviate the disturbances caused by vestibular malfunction, or by exposure to an unusual environment such as space. The first project deals with the influence on the spinal cord of stimulation of the vestibular labyrinth, particularly the otoliths. A second was concerned with the properties and neural basis of the tonic neck reflex. These two projects are related, because vestibulospinal and tonic neck reflexes interact in the maintenance of normal posture. The third project began with an interest in mechanisms of motion sickness, and eventually shifted to a study of central control of respiratory muscles involved in vomiting.

  9. Inhibitory effect of cervical trachea and chest wall vibrations on cough reflex sensitivity and perception of urge-to-cough in healthy male never-smokers

    PubMed Central

    2013-01-01

    Background Non-pharmacological options for symptomatic management of cough are desired. Although chest wall mechanical vibration is known to ameliorate cough reflex sensitivity, the effect of mechanical vibrations on perceptions of urge-to-cough has not been studied. Therefore, we investigated the effect of mechanical vibration of cervical trachea, chest wall and femoral muscle on cough reflex sensitivity, perceptions of urge-to-cough as well as dyspnea. Methods Twenty-four healthy male never-smokers were investigated for cough reflex sensitivity, perceptions of the urge-to-cough and dyspnea with or without mechanical vibration. Cough reflex sensitivity and urge-to-cough were evaluated by the inhalation of citric acid. The perception of dyspnea was evaluated by Borg scores during applications of external inspiratory resistive loads. Mechanical vibration was applied by placing a vibrating tuning fork on the skin surface of cervical trachea, chest wall and femoral muscle. Results Cervical trachea vibration significantly increased cough reflex threshold, as expressed by the lowest concentration of citric acid that elicited five or more coughs (C5), and urge-to-cough threshold, as expressed by the lowest concentration of citric acid that elicited urge-to-cough (Cu), but did not significantly affect dypnea sensation during inspiratory resistive loading. On the other hand, the chest wall vibration not only significantly increased C5 and Cu but also significantly ameliorated the load-response curve of dyspnea sensation. Conclusions Both cervical and trachea vibrations significantly inhibited cough reflex sensitivity and perception of urge-to-cough. These vibration techniques might be options for symptomatic cough management. PMID:24088411

  10. Modulation of two types of jaw-opening reflex by stimulation of the red nucleus.

    PubMed

    Satoh, Yoshihide; Yajima, Eriko; Ishizuka, Ken'Ichi; Nagamine, Yasuhiro; Iwasaki, Shin-ichi

    2013-08-01

    The red nucleus (RN) is divided cytoarchitecturally into two parts, the parvicellular part (RPC) and the magnocellular part (RMC). The present study aims, first, to compare the effects of RN stimulation between low- and high-threshold afferents-evoked jaw opening reflexes (JORs), and secondly to compare the size of these effects in the RPC and RMC. Experiments were performed on rats anesthetized with urethane-chloralose. The JOR was evoked by electrical stimulation of the inferior alveolar nerve and was recorded as the electromyographic response of the anterior belly of the digastric muscle. The stimulus intensity was either 1.2 (low-threshold) or 4.0 (high-threshold) times that necessary to elicit the JOR. Conditioning electrical stimulation of the RN significantly facilitated the JOR evoked by the low-threshold afferents. On the other hand, conditioning electrical stimulation of the RN significantly suppressed the JOR evoked by the high-threshold afferents. Microinjection of monosodium glutamate into the RN also facilitated the JOR evoked by the low-threshold afferents, but suppressed that evoked by high-threshold afferents. Facilitation did not differ between the RMC and the RPC. Suppression by the RMC stimulation was significantly greater than that by the RPC stimulation. These results suggest that the RN has distinct functional roles in the control of the JOR. PMID:23708019

  11. Deficits in Lower Limb Muscle Reflex Contraction Latency and Peak Force Are Associated With Impairments in Postural Control and Gross Motor Skills of Children With Developmental Coordination Disorder

    PubMed Central

    Fong, Shirley S.M.; Ng, Shamay S.M.; Guo, X.; Wang, Yuling; Chung, Raymond C.K.; Stat, Grad; Ki, W.Y.; Macfarlane, Duncan J.

    2015-01-01

    Abstract This cross-sectional, exploratory study aimed to compare neuromuscular performance, balance and motor skills proficiencies of typically developing children and those with developmental coordination disorder (DCD) and to determine associations of these neuromuscular factors with balance and motor skills performances in children with DCD. One hundred thirty children with DCD and 117 typically developing children participated in the study. Medial hamstring and gastrocnemius muscle activation onset latencies in response to an unexpected posterior-to-anterior trunk perturbation were assessed by electromyography and accelerometer. Hamstring and gastrocnemius muscle peak force and time to peak force were quantified by dynamometer, and balance and motor skills performances were evaluated with the Movement Assessment Battery for Children (MABC). Independent t tests revealed that children with DCD had longer hamstring and gastrocnemius muscle activation onset latencies (P < 0.001) and lower isometric peak forces (P < 0.001), but not times to peak forces (P > 0.025), than the controls. Multiple regression analysis accounting for basic demographics showed that gastrocnemius peak force was independently associated with the MABC balance subscore and ball skills subscore, accounting for 5.7% (P = 0.003) and 8.5% (P = 0.001) of the variance, respectively. Gastrocnemius muscle activation onset latency also explained 11.4% (P < 0.001) of the variance in the MABC ball skills subscore. Children with DCD had delayed leg muscle activation onset times and lower isometric peak forces. Gastrocnemius peak force was associated with balance and ball skills performances, whereas timing of gastrocnemius muscle activation was a determinant of ball skill performance in the DCD population. PMID:26469921

  12. Embodied Self-Reflexivity

    ERIC Educational Resources Information Center

    Pagis, Michal

    2009-01-01

    Drawing on G. H. Mead and Merleau-Ponty, this paper aims to extend our understanding of self-reflexivity beyond the notion of a discursive, abstract, and symbolic process. It offers a framework for embodied self-reflexivity, which anchors the self in the reflexive capacity of bodily sensations. The data consist of two years of ethnographic…

  13. Computation of inverse functions in a model of cerebellar and reflex pathways allows to control a mobile mechanical segment.

    PubMed

    Ebadzadeh, M; Tondu, B; Darlot, C

    2005-01-01

    The command and control of limb movements by the cerebellar and reflex pathways are modeled by means of a circuit whose structure is deduced from functional constraints. One constraint is that fast limb movements must be accurate although they cannot be continuously controlled in closed loop by use of sensory signals. Thus, the pathways which process the motor orders must contain approximate inverse functions of the bio-mechanical functions of the limb and of the muscles. This can be achieved by means of parallel feedback loops, whose pattern turns out to be comparable to the anatomy of the cerebellar pathways. They contain neural networks able to anticipate the motor consequences of the motor orders, modeled by artificial neural networks whose connectivity is similar to that of the cerebellar cortex. These networks learn the direct biomechanical functions of the limbs and muscles by means of a supervised learning process. Teaching signals calculated from motor errors are sent to the learning sites, as, in the cerebellum, complex spikes issued from the inferior olive are conveyed to the Purkinje cells by climbing fibers. Learning rules are deduced by a differential calculation, as classical gradient rules, and they account for the long term depression which takes place in the dendritic arborizations of the Purkinje cells. Another constraint is that reflexes must not impede voluntary movements while remaining at any instant ready to oppose perturbations. Therefore, efferent copies of the motor orders are sent to the interneurones of the reflexes, where they cancel the sensory-motor consequences of the voluntary movements. After learning, the model is able to drive accurately, both in velocity and position, angular movements of a rod actuated by two pneumatic McKibben muscles. Reflexes comparable to the myotatic and tendinous reflexes, and stabilizing reactions comparable to the cerebellar sensory-motor reactions, reduce efficiently the effects of perturbing torques

  14. Evaluation of muscle metaboreflex function through graded reduction in forearm blood flow during rhythmic handgrip exercise in humans.

    PubMed

    Ichinose, Masashi; Delliaux, Stephane; Watanabe, Kazuhito; Fujii, Naoto; Nishiyasu, Takeshi

    2011-08-01

    Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Our aim was to determine the muscle metaboreflex threshold and gain in humans by creating an open-loop relationship between active muscle blood flow and hemodynamic responses during a rhythmic handgrip exercise. Eleven healthy subjects performed the exercise at 5 or 15% of maximal voluntary contraction (MVC) in random order. During the exercise, forearm blood flow (FBF), which was continuously measured using Doppler ultrasound, was reduced in five steps by manipulating the inner pressure of an occlusion cuff on the upper arm. The FBF at each level was maintained for 3 min. The initial reductions in FBF elicited no hemodynamic changes, but once FBF fell below a threshold, mean arterial blood pressure (MAP) and heart rate (HR) increased and total vascular conductance (TVC) decreased in a linear manner. The threshold FBF during the 15% MVC trial was significantly higher than during the 5% MVC trial. The gain was then estimated as the slope of the relationship between the hemodynamic responses and FBFs below the threshold. The gains for the MAP and TVC responses did not differ between workloads, but the gain for the HR response was greater in the 15% MVC trial. Our findings thus indicate that increasing the workload shifts the threshold for the muscle metaboreflex to higher blood flows without changing the gain of the reflex for the MAP and TVC responses, whereas it enhances the gain for the HR response. PMID:21602474

  15. Vestibulocollic reflexes in the absence of head postural control

    PubMed Central

    Forbes, Patrick A.; Siegmund, Gunter P.; Happee, Riender; Schouten, Alfred C.

    2014-01-01

    Percutaneous electrical vestibular stimulation evokes reflexive responses in appendicular muscles that are suppressed during tasks in which the muscles are not contributing to balance control. In neck muscles, which stabilize the head on the torso and in space, it is unclear whether similar postural task dependence shapes vestibular reflexes. We investigated whether vestibulocollic reflexes are modulated during tasks in which vestibular information is not directly relevant to maintaining the head balanced on the torso. We hypothesized that vestibulocollic reflexes would be 1) evoked when neck muscles are not involved in balancing the head on the torso and 2) invariant across synergistic neck muscle contraction tasks. Muscle activity was recorded bilaterally in sternocleidomastoid and splenius capitis muscles during head-free and head-fixed conditions while subjects were exposed to stochastic electrical vestibular stimulation (±5 mA, 0–75 Hz). Significant vestibular reflex responses (P < 0.05) were observed during head-free and head-fixed trials. Response magnitude and timing were similar between head-free and head-fixed trials for sternocleidomastoid, but splenius capitis magnitudes decreased with the head fixed by ∼25% (P < 0.05). Nevertheless, this indicates that vestibulocollic responses are evoked independent of the requirement to maintain postural control of the head on the torso. Response magnitude and timing were similar across focal muscle contractions (i.e., axial rotation/flexion/extension) provided the muscle was active. In contrast, when subjects cocontracted neck muscles, vestibular-evoked responses decreased in sternocleidomastoid by ∼30–45% (P < 0.05) compared with focal muscle contractions but remained unchanged in splenius capitis. These results indicate robust vestibulocollic reflex coupling, which we suggest functions through its closed-loop influence on head posture to ensure cervical spine stabilization. PMID:25008409

  16. Assessment of Hyperactive Reflexes in Patients with Spinal Cord Injury

    PubMed Central

    Yang, Chung-Yong

    2015-01-01

    Hyperactive reflexes are commonly observed in patients with spinal cord injury (SCI) but there is a lack of convenient and quantitative characterizations. Patellar tendon reflexes were examined in nine SCI patients and ten healthy control subjects by tapping the tendon using a hand-held instrumented hammer at various knee flexion angles, and the tapping force, quadriceps EMG, and knee extension torque were measured to characterize patellar tendon reflexes quantitatively in terms of the tendon reflex gain (Gtr), contraction rate (Rc), and reflex loop time delay (td). It was found that there are significant increases in Gtr and Rc and decrease in td in patients with spinal cord injury as compared to the controls (P < 0.05). This study presented a convenient and quantitative method to evaluate reflex excitability and muscle contraction dynamics. With proper simplifications, it can potentially be used for quantitative diagnosis and outcome evaluations of hyperreflexia in clinical settings. PMID:25654084

  17. The effect of dry needling on pain, pressure pain threshold and disability in patients with a myofascial trigger point in the upper trapezius muscle.

    PubMed

    Ziaeifar, Maryam; Arab, Amir Massoud; Karimi, Noureddin; Nourbakhsh, Mohammad Reza

    2014-04-01

    Dry needling (DN) has been used recently by physical therapists as a therapy of choice for patients with myofascial trigger points (TrP). The purpose of this randomized controlled trial was to investigate the effect of DN in the treatment of TrPs in the upper trapezius (UT) muscle. A sample of convenience of 33 patients with TrP in the UT muscle participated in this study. Patients were randomly assigned to a standard (N = 17) or experimental group (N = 16). The treatment protocol for the standard group consisted of trigger point compression technique (TCT) on MTP, while the patients in the experimental group received DN. Pain intensity and pressure pain thresholds were assessed for both groups before and after the treatment sessions. In addition, the Disability of Arm, Hand, and Shoulder (DASH) was administered. Statistical analysis (paired t-test) revealed a significant improvement in pain, PPT and DASH scores after treatment in the experimental (DN) and standard (TCT) group compared with before treatment (P < 0.05). The ANCOVA revealed significant differences between the DN and TCT groups on the post-measurement VAS score (P = 0.01). There was, however, no significant difference between the two groups on the post-measurement score of the PPT (P = 0.08) and DASH (P = 0.34). DN produces an improvement in pain intensity, PPT and DASH and may be prescribed for subjects with TrP in UT muscles especially when pain relief is the goal of the treatment. PMID:24725800

  18. Surface EMG Recording of the Perioral Reflexes: Preliminary Observations on Stutterers and Nonstutterers.

    ERIC Educational Resources Information Center

    McClean, Michael D.

    1987-01-01

    Surface electrodes were used to describe the perioral reflexes in seven stutterers and five nonstutterers and electromyographic (EMG) recordings were obtained at electrode sites associated with the orbicularis oris inferior muscle and the depressor labia inferior muscle. A difference was noted in the pattern of reflex response between the two…

  19. Deficits in the coordination of agonist and antagonist muscles in stroke patients: implications for normal motor control.

    PubMed

    Levin, M F; Selles, R W; Verheul, M H; Meijer, O G

    2000-01-24

    Movement impairments about a single joint in stroke patients may be related to deficits in the central regulation of stretch reflex (SR) thresholds of agonist and antagonist muscles. One boundary of the SR threshold range for elbow flexor and extensor muscles was measured in hemiparetic subjects by analysing electromyographic activity during stretching of relaxed muscles at seven different velocities. For each velocity, dynamic SR thresholds were measured as angles at which electromyographic activity appeared. These data were used to determine the sensitivity of the threshold to velocity and the static SR thresholds for flexors and extensors. In contrast to relaxed muscles in healthy subjects, static flexor and extensor thresholds lay within the physiological range in 11/12 and 4/12 subjects, respectively. This implies that, in the range between the static SR threshold and one of the physiological joint limits, relaxation of the muscle was impossible. Subjects then made slow movements against different loads to determine their ranges of active movement. Maximal flexor and extensor torques were lower in hemiparetic subjects throughout the angular range. In some subjects, ranges were found in which no active torque could be produced in either extensor or both muscle groups. These ranges were related to the boundary values of SR thresholds found during passive muscle stretch. The range in which reciprocally organized agonist and antagonist muscle activity could be generated was limited in all but one subject. When attempting to produce torque from positions outside their measured range of movement, excessive muscle coactivation occurred, typically producing no or paradoxical motion in the opposite direction. Results suggest a relationship between spasticity measured at rest and the movement deficit in stroke by demonstrating a link between motor deficits and control deficits in the central regulation of individual SR thresholds. PMID:10640634

  20. The spinal reflex cannot be perceptually separated from voluntary movements.

    PubMed

    Ghosh, Arko; Haggard, Patrick

    2014-01-01

    Both voluntary and involuntary movements activate sensors in the muscles, skin, tendon and joints. As limb movement can result from a mixture of spinal reflexes and voluntary motor commands, the cortical centres underlying conscious proprioception might either aggregate or separate the sensory inputs generated by voluntary movements from those generated by involuntary movements such as spinal reflexes. We addressed whether healthy volunteers could perceive the contribution of a spinal reflex during movements that combined both reflexive and voluntary contributions. Volunteers reported the reflexive contribution in leg movements that were partly driven by the knee-jerk reflex induced by a patellar tendon tap and partly by voluntary motor control. In one condition, participants were instructed to kick back in response to a tendon tap. The results were compared to reflexes in a resting baseline condition without voluntary movement. In a further condition, participants were instructed to kick forwards after a tap. Volunteers reported the perceived reflex contribution by repositioning the leg to the perceived maximum displacement to which the reflex moved the leg after each tendon tap. In the resting baseline condition, the reflex was accurately perceived. We found a near-unity slope of linear regressions of perceived on actual reflexive displacement. Both the slope value and the quality of regression fit in individual volunteers were significantly reduced when volunteers were instructed to generate voluntary backward kicks as soon as they detected the tap. In the kick forward condition, kinematic analysis showed continuity of reflex and voluntary movements, but the reflex contribution could be estimated from electromyography (EMG) recording on each trial. Again, participants' judgements of reflexes showed a poor relation to reflex EMG, in contrast to the baseline condition. In sum, we show that reflexes can be accurately perceived from afferent information. However

  1. Intact thumb reflex in areflexic Guillain Barré syndrome: A novel phenomenon

    PubMed Central

    Naik, Karkal Ravishankar; Saroja, Aralikatte Onkarappa; Mahajan, Manik

    2014-01-01

    Introduction: Areflexia is one of the cardinal clinical features for the diagnosis of Guillain Barré syndrome. However, some patients may have sluggish proximal muscle stretch reflexes. Presence of thumb reflex, a distal stretch muscle reflex has not been documented in Guillain Barré syndrome. Materials and Methods: We prospectively evaluated thumb reflex in Guillain Barré syndrome patients and age matched controls from April to September 2013. Results: There were 31 patients with Guillain Barré syndrome in whom thumb reflex could be elicited in all (24 brisk, 7 sluggish), whereas all the other muscle stretch reflexes were absent in 29 patients at presentation and the remaining two had sluggish biceps and quadriceps reflexes (P = 0.001). Serial examination revealed gradual diminution of the thumb reflex (P < 0.001). Rapid progression of weakness was associated with early loss of the thumb reflex. Conclusion: Thumb reflex, a distal stretch reflex is preserved in the early phase of Guillain Barré syndrome. PMID:25024572

  2. What is a reflex?

    PubMed Central

    Truog, Robert D.

    2015-01-01

    Uncertainty in diagnosing disorders of consciousness, and specifically in determining whether consciousness has been lost or retained, poses challenging scientific and ethical questions. Recent neuroimaging-based tests for consciousness have cast doubt on the reliability of behavioral criteria in assessing states of consciousness and generate new questions about the assumptions used in formulating coherent diagnostic criteria. The reflex, a foundational diagnostic tool, offers unique insight into these disorders; behaviors produced by unconscious patients are thought to be purely reflexive, whereas those produced by conscious patients can be volitional. Further investigation, however, reveals that reflexes cannot be reliably distinguished from conscious behaviors on the basis of any generalizable empirical characteristics. Ambiguity between reflexive and conscious behaviors undermines the capacity of the reflex to distinguish between disorders of consciousness and has implications for how these disorders should be conceptualized in future diagnostic criteria. PMID:26085602

  3. Characteristics of Glottic Closure Reflex in a Canine Model

    PubMed Central

    Kang, Ju Wan; Kim, Kwang-Moon

    2009-01-01

    Purpose The most important function of the larynx is airway protection which is provided through a polysynaptic reflex closure triggered by the receptors in the glottic and supraglottic mucosa, evoking the reflex contraction of the laryngeal muscles especially by strong adduction of vocal cords. Based on the hypotheses that central facilitation is essential for this bilateral adductor reflex and that its disturbance can result in weakened laryngeal closure, we designed this study to elucidate the effect of central facilitation on this protective reflex. Materials and Methods Seven adult, 20 kg mongrel dogs underwent evoked response laryngeal electromyography under 0.5 to 1.0 MAC (minimum alveolar concentration) isoflurane anesthesia. The internal branch of the superior laryngeal nerve was stimulated through bipolar platinum-iridium electrodes, and recording electrodes were positioned in the ipsilateral and contralateral thyroarytenoid muscles. Results Ipsilateral reflex closure was consistantly recorded regardless of anesthetic levels. However, contralateral reflex responses disappeared as anesthetic levels were deepened. Additionally, late responses (R2) were detected in one animal at lower level of anesthesia. Conclusions Deepened level of anesthesia affects central facilitation and results in the loss of the crossed adductor reflex, predisposing to a weakened glottic closure response. Precise understanding of this effect may possibly provide a way to prevent aspiration in unconscious patients. PMID:19568600

  4. On Reflexive Data Models

    SciTech Connect

    Petrov, S.

    2000-08-20

    An information system is reflexive if it stores a description of its current structure in the body of stored information and is acting on the base of this information. A data model is reflexive, if its language is meta-closed and can be used to build such a system. The need for reflexive data models in new areas of information technology applications is argued. An attempt to express basic notions related to information systems is made in the case when the system supports and uses meta-closed representation of the data.

  5. Effects of intrathecal or intracerebroventricular administration of nonsteroidal anti-inflammatory drugs on a C-fiber reflex in rats.

    PubMed

    Bustamante, D; Paeile, C; Willer, J C; Le Bars, D

    1997-06-01

    A C-fiber reflex elicited by electrical stimulation within the territory of the sural nerve was recorded from the ipsilateral biceps femoris muscle in anesthetized rats. The temporal evolution of the response was studied using a constant stimulus intensity (3 times threshold), and recruitment curves were built by varying the stimulus intensity from 0 to 7 times threshold. The intrathecal (i.t.) but not i.c.v. administration of aspirin, indomethacin, ketoprofen and lysine clonixinate resulted in dose-dependent depressions of the C-fiber reflex. In contrast, saline was ineffective. Regardless of the route of administration, the drugs never produced disturbances in heart rate and/or acid-base equilibrium. When a constant level of stimulation was used, 500 microg of aspirin i.t. induced a blockade of the reflex immediately after the injection, followed by a partial recovery. Indomethacin produced a stable depression, which reached 80 to 90% with an i.t. dose of 500 microg. Ketoprofen and lysine clonixinate produced a more stable effect; the highest doses (500 microg) produced a steady-state depression of approximately 50% for approximately 30 min. When the recruitment curves were built with a range of nociceptive stimulus intensities, all of the drugs except for indomethacin produced a dose-dependent decrease in the slopes and the areas under the recruitment curves without major modifications in the thresholds; indomethacin also induced a significant dose-related increase in the threshold. The orders of potency for both stimulation paradigms with the i.t. route were the same, namely aspirin > indomethacin > lysine clonixinate > or = ketoprofen. It is concluded that nonsteroidal anti-inflammatory drugs elicit significant antinociceptive effects at a spinal level, which do not depend on the existence of a hyperalgesic or inflammatory state. Such effects were not seen after injections within the lateral ventricle. PMID:9190874

  6. Reflex operculoinsular seizures.

    PubMed

    Xiao, Handsun; Tran, Thi Phuoc Yen; Pétrin, Myriam; Boucher, Olivier; Mohamed, Ismail; Bouthillier, Alain; Nguyen, Dang Khoa

    2016-03-01

    Activation of specific cortical territories by certain stimuli is known to trigger focal seizures. We report three cases of well documented operculo-insular reflex seizures, triggered by somatosensory stimuli in two and loud noises in the third. Limited operculoinsular resection resulted in an excellent outcome for all. We discuss these observations in regard to the literature on reflex epilepsy and known functions of the insula. [Published with video sequences online]. PMID:26892245

  7. [The endonasopalpebral reflex].

    PubMed

    Vinnitskiĭ, A R; Vinnitskaia, N V

    1989-06-01

    The authors describe the endonasopalpebral reflex which is evoked from the nasal mucosa. Reduction of this reflex may be used as a fine index of involvement of the trigeminus in patients with acoustic neuromas. This makes it possible to differentiate this tumour at early stages of its development from neuritis of the acoustic nerve. This is of great importance for this pathological situation. PMID:2781776

  8. Muscle Activation Patterns When Passively Stretching Spastic Lower Limb Muscles of Children with Cerebral Palsy

    PubMed Central

    Bar-On, Lynn; Aertbeliën, Erwin; Molenaers, Guy; Desloovere, Kaat

    2014-01-01

    The definition of spasticity as a velocity-dependent activation of the tonic stretch reflex during a stretch to a passive muscle is the most widely accepted. However, other mechanisms are also thought to contribute to pathological muscle activity and, in patients post-stroke and spinal cord injury can result in different activation patterns. In the lower-limbs of children with spastic cerebral palsy (CP) these distinct activation patterns have not yet been thoroughly explored. The aim of the study was to apply an instrumented assessment to quantify different muscle activation patterns in four lower-limb muscles of children with CP. Fifty-four children with CP were included (males/females n = 35/19; 10.8±3.8 yrs; bilateral/unilateral involvement n =  32/22; Gross Motor Functional Classification Score I–IV) of whom ten were retested to evaluate intra-rater reliability. With the subject relaxed, single-joint, sagittal-plane movements of the hip, knee, and ankle were performed to stretch the lower-limb muscles at three increasing velocities. Muscle activity and joint motion were synchronously recorded using inertial sensors and electromyography (EMG) from the adductors, medial hamstrings, rectus femoris, and gastrocnemius. Muscles were visually categorised into activation patterns using average, normalized root mean square EMG (RMS-EMG) compared across increasing position zones and velocities. Based on the visual categorisation, quantitative parameters were defined using stretch-reflex thresholds and normalized RMS-EMG. These parameters were compared between muscles with different activation patterns. All patterns were dominated by high velocity-dependent muscle activation, but in more than half, low velocity-dependent activation was also observed. Muscle activation patterns were found to be both muscle- and subject-specific (p<0.01). The intra-rater reliability of all quantitative parameters was moderate to good. Comparing RMS-EMG between incremental

  9. Changes in perceived heaviness and motor commands produced by cutaneous reflexes in man.

    PubMed Central

    Aniss, A M; Gandevia, S C; Milne, R J

    1988-01-01

    1. This study examined the relationship between the perceived heaviness of a weight and reflexes acting on the motoneurones required for the contraction. The perceived heaviness of low (100 g) and high (500 g) reference weights lifted by the first dorsal interosseous muscle was estimated using a matching task. Weights were also lifted during stimulation of the digital nerves of the index finger at two times and four times sensory threshold (T). Averages of force and EMG were also made when isometric forces of 100 and 500 g were maintained. 2. Stimuli at 4T produced a significant increase in perceived heaviness in each subject for both reference weights. Averages of EMG made under isometric conditions showed a short-latency inhibition with a reflex reduction in force following single stimuli. This inhibition was also observed during weight lifting when trains of stimuli were given. 3. Stimuli at 2T produced less-marked changes in EMG, averaged force, and perceived heaviness for individual subjects. However, for the group of subjects, perceived heaviness declined significantly with 2T stimuli for the 500 g but not the 100 g weight. This decrease in perceived heaviness was associated with evidence of short-latency facilitation within the motoneurone pool. 4. Inhibition of the motoneurone pool was associated with an increase and facilitation with a decrease in perceived heaviness. These observations favour a role for a signal of centrally generated motor command in the sensation of heaviness and provide insight as to how this signal must change when reflex inputs change and when high-threshold motoneurones are recruited. PMID:3411508

  10. Electrically induced blink reflex and facial motor nerve stimulation in beagles.

    PubMed

    Añor, S; Espadaler, J M; Pastor, J; Pumarola, M

    2000-01-01

    Electrophysiologic assessment of the blink reflex test and the muscle-evoked potentials evoked by stimulation of the facial nerve were performed in 15 healthy adult Beagles before and after supraorbital (trigeminal) and facial anesthetic nerve blocks performed by lidocaine injections. Unilateral electrical stimulation of the supraorbital nerve elicited 2 ipsilateral (R1 and R2) and a contralateral (Rc) reflex muscle potential in orbicularis oculi muscles. Electrical stimulation of the facial nerve elicited 2 muscle potentials (a direct response [D] and a reflex faciofacial response [RF]) in the ipsilateral orbicularis oculi muscle. Anesthetic block of the left supraorbital nerve resulted in bilateral lack of responses upon left supraorbital nerve stimulation, but normal responses in right and left orbicularis oculi muscles upon right supraorbital stimulation. Right facial anesthetic block produced lack of responses in the right orbicularis oculi muscle regardless the side of supraorbital nerve stimulation. Results of this study demonstrate that the blink reflex can be electrically elicited and assessed in dogs. Reference values for the blink reflex responses and for the muscle potentials evoked by direct facial nerve stimulation in dogs are provided. The potential usefulness of the electrically elicited blink reflex test in the diagnosis of peripheral facial and trigeminal dysfunction in dogs was demonstrated. PMID:10935892

  11. Interlimb Reflexes Induced by Electrical Stimulation of Cutaneous Nerves after Spinal Cord Injury

    PubMed Central

    Butler, Jane E.; Godfrey, Sharlene; Thomas, Christine K.

    2016-01-01

    Whether interlimb reflexes emerge only after a severe insult to the human spinal cord is controversial. Here the aim was to examine interlimb reflexes at rest in participants with chronic (>1 year) spinal cord injury (SCI, n = 17) and able-bodied control participants (n = 5). Cutaneous reflexes were evoked by delivering up to 30 trains of stimuli to either the superficial peroneal nerve on the dorsum of the foot or the radial nerve at the wrist (5 pulses, 300 Hz, approximately every 30 s). Participants were instructed to relax the test muscles prior to the delivery of the stimuli. Electromyographic activity was recorded bilaterally in proximal and distal arm and leg muscles. Superficial peroneal nerve stimulation evoked interlimb reflexes in ipsilateral and contralateral arm and contralateral leg muscles of SCI and control participants. Radial nerve stimulation evoked interlimb reflexes in the ipsilateral leg and contralateral arm muscles of control and SCI participants but only contralateral leg muscles of control participants. Interlimb reflexes evoked by superficial peroneal nerve stimulation were longer in latency and duration, and larger in magnitude in SCI participants. Interlimb reflex properties were similar for both SCI and control groups for radial nerve stimulation. Ascending interlimb reflexes tended to occur with a higher incidence in participants with SCI, while descending interlimb reflexes occurred with a higher incidence in able-bodied participants. However, the overall incidence of interlimb reflexes in SCI and neurologically intact participants was similar which suggests that the neural circuitry underlying these reflexes does not necessarily develop after central nervous system injury. PMID:27049521

  12. Separating medial olivocochlear from acoustic reflex effects on transient evoked otoacoustic emissions in unanesthetized mice

    NASA Astrophysics Data System (ADS)

    Xu, Yingyue; Cheatham, Mary Ann; Siegel, Jonathan

    2015-12-01

    Descending neural pathways in the mammalian auditory system are believed to modulate the function of the peripheral auditory system [3, 8, 10]. These pathways include the medial olivocochlear (MOC) efferent innervation to the cochlear outer hair cells (OHCs) and the acoustic reflex pathways mediating middle ear muscle (MEM) contractions. The MOC effects can be monitored noninvasively using otoacoustic emissions (OAEs) [5, 6], which are acoustic byproducts of cochlear function [7]. In this study, we applied a sensitive method to determine when and to what degree contralateral MEM suppression contaminated MOC efferent effects on TEOAEs in unanesthetized mice. The lowest contralateral broadband noise evoking MEM contractions varied across animals. Examples of potential MOC-mediated TEOAE suppression with contralateral noise below MEM contraction thresholds were seen, but this behavior did not occur in the majority of cases.

  13. Phase-dependent reversal of the crossed conditioning effect on the soleus Hoffmann reflex from cutaneous afferents during walking in humans.

    PubMed

    Suzuki, Shinya; Nakajima, Tsuyoshi; Futatsubashi, Genki; Mezzarane, Rinaldo A; Ohtsuka, Hiroyuki; Ohki, Yukari; Komiyama, Tomoyoshi

    2016-02-01

    We previously demonstrated that non-noxious electrical stimulation of the cutaneous nerve innervating the contralateral foot modified the excitability of the Hoffmann (H-) reflex in the soleus muscle (SOL) in a task-dependent manner during standing and walking in humans. To date, however, it remains unclear how the crossed conditioning effect on the SOL H-reflex from the contralateral foot is modified during the various phases of walking. We sought to answer this question in the present study. The SOL H-reflex was evoked in healthy volunteers by an electrical test stimulation (TS) of the right (ipsilateral) posterior tibial nerve at five different phases during treadmill walking (4 km/h). A non-noxious electrical stimulation was delivered to the superficial peroneal nerve of the left (contralateral) ankle ~100 ms before the TS as a conditioning stimulation (CS). This CS significantly suppressed the H-reflex amplitude during the early stance phase, whereas the same CS significantly facilitated the H-reflex amplitude during the late stance phase. The CS alone did not produce detectable changes in the full-wave rectified electromyogram of the SOL. This result indicates that presynaptic mechanisms driven by the activation of low-threshold cutaneous afferents in the contralateral foot play a role in regulating the transmission between the Ia terminal and motoneurons in a phase-dependent manner. The modulation pattern of the crossed conditioning effect on the SOL H-reflex may be functionally relevant for the left-right coordination of leg movements during bipedal walking. PMID:26573576

  14. Physiological tremor enhanced by manoeuvres affecting the segmental stretch reflex.

    PubMed Central

    Young, R R; Hagbarth, K E

    1980-01-01

    In view of recent evidence that physiological tremor can be enhanced by positive feedback via the segmental stretch reflex, several manoeuvres and procedures were employed to enhance the finger and hand tremor of healthy subjects--the purpose being to determine if tremorogenic effects, at least in part, are due to increase efficacy of the stretch reflex servo. Mechanical events during tremor (and during voluntary or electrically induced muscle twitches) were recorded together with EMG activity from wrist and finger flexor muscles and discharges from primary spindle endings in these muscles. Physiological tremor can be enhanced not only by manoeuvres which increase the gain of segmental stretch reflexes (Jendrassik manoeuvre) but also by manoeuvres which increase the contrast in spindle firing during stretch versus shortening phases of tremor, thus enhancing reflex modulation. Effects of the latter type can be achieved by procedures which alter mechanical twitch properties of extrafusal fibres (isoproterenol infusions and fatigue) and by procedures which involve application of spindle stimuli acting preferentially during stretch phases of tremor movements (muscle vibrations). Physiological tremor, which can be temporarily enhanced by an externally applied muscle perturbation, also becomes accentuated by those small "pseudo-myoclonic" jerks which occur in all normal subjects attempting to perform slow, smooth movements. PMID:7373322

  15. Electrically induced blink reflex in horses.

    PubMed

    Añor, S; Espadaler, J M; Monreal, L; Mayhew, I G

    The electrically induced blink reflex was studied electromyographically in 21 healthy adult, detomidine-sedated horses. Using surface electrodes, the supraorbital nerve was electrically stimulated at the supraorbital foramen. The responses were recorded from the ipsilateral and contralateral orbicularis oculi muscles with concentric needle electrodes inserted in the lateral aspect of the ventral eyelids. Ipsilateral and contralateral recordings were made on successive stimulations of the same side of the face, maintaining a constant stimulus intensity. The electromyographically recorded responses consisted of an early R1 response in the orbicularis oculi muscle ipsilateral to the side of stimulation, a bilateral late response (ipsilateral R2 and contralateral Rc) and a third, R3 response, in the ipsilateral orbicularis oculi muscle. All the responses were polyphasic muscle potentials of variable duration and peak to peak amplitudes. The reflex latency of the R1 response was, as in man, fairly stable. The R2 response showed greater variability both within and between individual horses. The Rc response was recorded in only 13 of the 21 horses and showed a slightly longer latency than the corresponding R2. The R3 response, which is significantly related to pain sensation in man, appeared in 19 horses and showed the greatest variability in latency. PMID:9123787

  16. Crossed linguo-buccal reflex in post-stroke patients.

    PubMed

    Nagumo, K; Hirayama, K; Nakajima, Y; Takahashi, M

    2000-12-15

    A pathological crossed orofacial reflex, called crossed linguo-buccal reflex in the present study, was observed in approximately 1/3 of post-stroke patients with central facial palsy. Stroking with pressure two or three times with a split wooden tongue-blade to the tongue or palate contralateral to the central facial palsy elicited a reflex movement consisting of retraction of the angle of mouth and medio-posterior withdrawal of the buccal mucosa on the paretic side. Seventy-seven patients with central hemifacial palsy caused by a unilateral cerebral lesion were examined clinically, electromyographically and by computed tomography (CT) and magnetic resonance imaging (MRI). In addition, three men with bilateral cerebral lesions and bilateral crossed linguo-buccal reflexes were electromyographically examined. Twenty-two patients with unilateral cerebral lesions had this reflex. It was found that this reflex was most frequently observed in patients with a capsulo-caudate lesion involving the head of the caudate nucleus, the anterior limb and genu of the internal capsule. The electromyogram of the reflex showed increased activity in the orbicularis oris, depressor anguli oris, risorius, zygomaticus major and buccinator muscles on the paretic side with a long latency (254-856 ms), and a prolonged after-discharge after the stimulation. Reciprocal inhibition was observed in patients with bilateral positive reflexes. These findings suggest that liberation of the polysynaptic brainstem reflex in the medulla oblongata and pons from the indirect corticobulbar inhibition may underlie the occurrence of the crossed linguo-buccal reflex in post-stroke patients. PMID:11102639

  17. H-reflex changes following spinal cord injury.

    PubMed

    Little, J W; Halar, E M

    1985-01-01

    Changes in both central synaptic excitability (CSE) and peripheral sensitivity of muscle spindle stretch receptors have been hypothesized to contribute to hyperactive stretch reflexes of spasticity. To assess CSE, the monosynaptic H-reflex to the triceps surae muscles was tested serially over the first six months after traumatic spinal cord injury (SCI). Six clinically complete SCI patients were compared to age-matched control subjects. As a measure of H-reflex excitability, H/M ratios were calculated by dividing maximum H-reflex by maximum M-response amplitude. Analysis of variance over the testing trials showed significant change in H/M ratios for SCI patients (p less than 0.01). T-tests comparing mean H/M ratios at different time periods after SCI revealed a significant increment after three months (p less than 0.01). H-reflex amplitude also increased significantly over this time period (p less than 0.04), but M-response amplitude did not change significantly. These increases in H/M ratio and H-reflex amplitude suggest that an increase in CSE may contribute to the appearance of hyperreflexia after SCI. PMID:3966862

  18. Changes in Soleus H-Reflex Modulation after Treadmill Training in Children with Cerebral Palsy

    ERIC Educational Resources Information Center

    Hodapp, Maike; Vry, Julia; Mall, Volker; Faist, Michael

    2009-01-01

    In healthy children, short latency leg muscle reflexes are profoundly modulated throughout the step cycle in a functionally meaningful way and contribute to the electromyographic (EMG) pattern observed during gait. With maturation of the corticospinal tract, the reflex amplitudes are depressed via supraspinal inhibitory mechanisms. In the soleus…

  19. Corneomandibular reflex: Anatomical basis

    PubMed Central

    Pistacchi, Michele; Gioulis, Manuela; Mazzon, Davide; Marsala, Sandro Zambito

    2015-01-01

    Corneomandibular reflex is a pathological phenomenon evident in cases of severe brainstem damage. It is considered to be a pathological exteroceptive reflex, associated with precentro bulbar tract lesions. The sign is useful in distinguishing central neurological injuries to metabolic disorders in acutely comatose patients, localizing lesions to the upper brainstem area, determining the depth of coma and its evolution, providing evidence of uncal or transtentorial herniation in acute cerebral hemisphere lesions, and it is a marker of supraspinal level impairment in amyotrophic lateral sclerosis and multiple sclerosis. This sign was evident in a patient with severe brain damage. We discuss the literature findings and its relevance in prognosis establishment. PMID:26752910

  20. Experimenting With Baroreceptor Reflexes

    NASA Technical Reports Server (NTRS)

    Eckberg, Dwain L.; Goble, Ross L.

    1988-01-01

    Carotid arteries stimulated by pressure or suction on neck. Baro-Cuff is silicone-rubber chamber that fits on front of subject's neck. Electronic system, stepping motor, bellows, and umbilical tube furnish controlled pressure to chamber. Pressure sensor provides feedback to microprocessor in electronic system. Developed to study blood-pressure-reflex responses of astronauts in outer space. Useful for terrestrial studies of patients with congestive heart failure, chronic diabetes mellitus, and other conditions in which blood-pressure-reflex controls behave abnormally.

  1. Reflexivity in Pigeons

    ERIC Educational Resources Information Center

    Sweeney, Mary M.; Urcuioli, Peter J.

    2010-01-01

    A recent theory of pigeons' equivalence-class formation (Urcuioli, 2008) predicts that reflexivity, an untrained ability to match a stimulus to itself, should be observed after training on two "mirror-image" symbolic successive matching tasks plus identity successive matching using some of the symbolic matching stimuli. One group of pigeons was…

  2. Reliability of the Achilles tendon tap reflex evoked during stance using a pendulum hammer.

    PubMed

    Mildren, Robyn L; Zaback, Martin; Adkin, Allan L; Frank, James S; Bent, Leah R

    2016-01-01

    The tendon tap reflex (T-reflex) is often evoked in relaxed muscles to assess spinal reflex circuitry. Factors contributing to reflex excitability are modulated to accommodate specific postural demands. Thus, there is a need to be able to assess this reflex in a state where spinal reflex circuitry is engaged in maintaining posture. The aim of this study was to determine whether a pendulum hammer could provide controlled stimuli to the Achilles tendon and evoke reliable muscle responses during normal stance. A second aim was to establish appropriate stimulus parameters for experimental use. Fifteen healthy young adults stood on a forceplate while taps were applied to the Achilles tendon under conditions in which postural sway was constrained (by providing centre of pressure feedback) or unconstrained (no feedback) from an invariant release angle (50°). Twelve participants repeated this testing approximately six months later. Within one experimental session, tap force and T-reflex amplitude were found to be reliable regardless of whether postural sway was constrained (tap force ICC=0.982; T-reflex ICC=0.979) or unconstrained (tap force ICC=0.968; T-reflex ICC=0.964). T-reflex amplitude was also reliable between experimental sessions (constrained ICC=0.894; unconstrained ICC=0.890). When a T-reflex recruitment curve was constructed, optimal mid-range responses were observed using a 50° release angle. These results demonstrate that reliable Achilles T-reflexes can be evoked in standing participants without the need to constrain posture. The pendulum hammer provides a simple method to allow researchers and clinicians to gather information about reflex circuitry in a state where it is involved in postural control. PMID:26454702

  3. The Use of an Alternative Extraoral Periapical Technique for Patients with Severe Gag Reflex

    PubMed Central

    e Silva, Mauro Henrique Chagas; Santos, Mariane Floriano Lopes; de Lima, Carolina Oliveira; Campos, Celso Neiva

    2016-01-01

    Gag reflex is a physiologic mechanism that promotes contraction of the muscles of the tongue and pharyngeal walls. Different factors, including intraoral radiographic films and sensors, may trigger this reflex. Patients with severe gag reflex may not be able to tolerate the presence of intraoral radiographic films or sensors during root canal therapy (RCT). This factor may prevent an appropriate intraoral radiograph, which is important in RCT. Different approaches have been used to facilitate dental procedures in patients suffering from severe gag reflex. The use of an extraoral radiographic technique is an alternative method to obtain working length confirmation in patients with severe gag reflex. In this report of 2 cases, the use of an extraoral radiographic technique as an alternative approach during RCT in patients with severe gag reflex associated with phobic behavior and trismus was successfully demonstrated. PMID:27547474

  4. The Use of an Alternative Extraoral Periapical Technique for Patients with Severe Gag Reflex.

    PubMed

    E Silva, Mauro Henrique Chagas; Coelho, Marcelo Santos; Santos, Mariane Floriano Lopes; de Lima, Carolina Oliveira; Campos, Celso Neiva

    2016-01-01

    Gag reflex is a physiologic mechanism that promotes contraction of the muscles of the tongue and pharyngeal walls. Different factors, including intraoral radiographic films and sensors, may trigger this reflex. Patients with severe gag reflex may not be able to tolerate the presence of intraoral radiographic films or sensors during root canal therapy (RCT). This factor may prevent an appropriate intraoral radiograph, which is important in RCT. Different approaches have been used to facilitate dental procedures in patients suffering from severe gag reflex. The use of an extraoral radiographic technique is an alternative method to obtain working length confirmation in patients with severe gag reflex. In this report of 2 cases, the use of an extraoral radiographic technique as an alternative approach during RCT in patients with severe gag reflex associated with phobic behavior and trismus was successfully demonstrated. PMID:27547474

  5. Adaptive Thresholds

    SciTech Connect

    Bremer, P. -T.

    2014-08-26

    ADAPT is a topological analysis code that allow to compute local threshold, in particular relevance based thresholds for features defined in scalar fields. The initial target application is vortex detection but the software is more generally applicable to all threshold based feature definitions.

  6. An artificial muscle computer

    NASA Astrophysics Data System (ADS)

    Marc O'Brien, Benjamin; Alexander Anderson, Iain

    2013-03-01

    We have built an artificial muscle computer based on Wolfram's "2, 3" Turing machine architecture, the simplest known universal Turing machine. Our computer uses artificial muscles for its instruction set, output buffers, and memory write and addressing mechanisms. The computer is very slow and large (0.15 Hz, ˜1 m3); however by using only 13 artificial muscle relays, it is capable of solving any computable problem given sufficient memory, time, and reliability. The development of this computer shows that artificial muscles can think—paving the way for soft robots with reflexes like those seen in nature.

  7. THE ACTION OF SODIUM 4-HYDROXYBUTYRATE ON SPINAL REFLEXES.

    PubMed

    BASIL, B; BLAIR, A M; HOLMES, S W

    1964-04-01

    The actions of sodium 4-hydroxybutyrate, gamma-aminobutyric acid and meprobamate have been studied in unanaesthetized animals, in local anaesthetic tests, on isolated organ preparations, on convulsions induced by picrotoxin and strychnine, and on monosynaptic (patellar) and polysynaptic (plantar) reflexes of the spinal cord. Sodium 4-hydroxybutyrate induced a sleep-like state with three unusual features: the righting reflex was remarkably persistent, respiration was good throughout and recovery was abrupt. gamma-Aminobutyric acid was inactive and meprobamate caused flaccid paralysis with loss of the righting reflex. None of the agents affected the responses of the rat diaphragm either to direct stimulation of the muscle or to indirect stimulation through the phrenic nerve. Only meprobamate reduced the responses of theguinea-pig isolated ileum preparation, showed local anaesthetic action and had an anticonvulsant action. All three compounds were capable, after intravenous or topical application, of blocking plantar reflexes in doses which did not affect the patellar reflex. The spinal animal responded in the same way, to the same dose of sodium 4-hydroxybutyrate, as the decerebrate preparation. Topical application to the motor cortex had no effect on spinal reflexes. We conclude that sodium 4-hydroxybutyrate acts preferentially on the internuncial neurones in the spinal cord but differs from meprobamate in its other actions. The similarity between the actions of sodium 4-hydroxybutyrate and of gamma-aminobutyric acid provides furtherevidence in support of the hypothesis that sodium 4-hydroxybutyrate is involved in the gamma-aminobutyric acid metabolic pathways. PMID:14190466

  8. Measurement of the lateral thoracic reflex latency in ponies.

    PubMed

    Hahn, C N; Mayhew, I G; Washbourne, J R

    1998-01-01

    Lateral thoracic nerve reflex latencies values were measured in ponies using a simple, non-invasive technique. The reflex was elicited using an external triggering hammer attached to an electrodiagnostic unit. The resulting evoked, compound muscle action potentials were recorded with electrodes, which were placed over the 6th ribs or 11th rib level with the axilla. Two superimposed repeats of 4 signal-averaged sweeps of 50 or 100 milliseconds were recorded and the estimated reflex pathway was measured for each subject in order to calculate the reflex latencies and latency velocities. Mean left and right 6th rib peak latencies were not significantly different from each other (P = .609), but left 6th rib latencies were shorter than those recorded from the 11th rib (P < .0001), substantiating the existence of an indirect (central) pathway to the reflex. The calculated left and right 6th rib latency velocities were not significantly different from each other (P = .58) but left 6th rib latency velocities were different from left 11th rib (P = .009). The calculated latency velocities were within the broad range for corticospinal tract motor conduction velocities and comparable to magnetic motor evoked latency velocities. The use of lateral thoracic reflex latency measurements to objectively identify the site of spinal cord lesions is discussed. PMID:9686392

  9. Corporeal reflexivity and autism.

    PubMed

    Ochs, Elinor

    2015-06-01

    Ethnographic video recordings of high functioning children with autism or Aspergers Syndrome in everyday social encounters evidence their first person perspectives. High quality visual and audio data allow detailed analysis of children's bodies and talk as loci of reflexivity. Corporeal reflexivity involves displays of awareness of one's body as an experiencing subject and a physical object accessible to the gaze of others. Gaze, demeanor, actions, and sotto voce commentaries on unfolding situations indicate a range of moment-by-moment reflexive responses to social situations. Autism is associated with neurologically based motor problems (e.g. delayed action-goal coordination, clumsiness) and highly repetitive movements to self-soothe. These behaviors can provoke derision among classmates at school. Focusing on a 9-year-old girl's encounters with peers on the playground, this study documents precisely how autistic children can become enmeshed as unwitting objects of stigma and how they reflect upon their social rejection as it transpires. Children with autism spectrum disorders in laboratory settings manifest diminished understandings of social emotions such as embarrassment, as part of a more general impairment in social perspective-taking. Video ethnography, however, takes us further, into discovering autistic children's subjective sense of vulnerability to the gaze of classmates. PMID:25939529

  10. Speech-Muscle Visuomotor Tracking in Dysarthric and Nonimpaired Speakers.

    ERIC Educational Resources Information Center

    McClean, Michael D.; And Others

    1987-01-01

    Surface electrodes were used to describe the perioral reflexes in seven stutterers and five nonstutterers and electromyographic (EMG) recordings were obtained at electrode sites associated with the orbicularis oris inferior muscle and the depressor labia inferior muscle. A difference was noted in the pattern of reflex response between the two…

  11. Implementation of reflex loops in a biomechanical finite element model.

    PubMed

    Salin, Dorian; Arnoux, Pierre-Jean; Kayvantash, Kambiz; Behr, Michel

    2016-11-01

    In the field of biomechanics, the offer of models which are more and more realistic requires to integrate a physiological response, in particular, the controlled muscle bracing and the reflexes. The following work aims to suggest a unique methodology which couples together a sensory and motor loop with a finite element model. Our method is applied to the study of the oscillation of the elbow in the case of a biceps brachial stretch reflex. The results obtained are promising in the purpose of the development of reactive human body models. PMID:27108871

  12. Calibration of ipsilateral stimulus transducer for acoustic reflex measurements.

    PubMed

    Olsen, S; Osterhammel, P A; Rasmussen, A N; Nielsen, L H

    1995-01-01

    Pure-tone Reference Equivalent Threshold Sound Pressure Level (RETSPL) of the ipsilateral stimulus receiver for acoustic reflex measurements on Madsen Electronics type Zodiac 901 impedance audiometer is provided. The results, obtained from 20 normal-hearing subjects, are achieved by comparing hearing threshold levels measured using a TDH 39 telephone (calibrated to ISO 389) with thresholds recorded using the ipsilateral stimulus insert phone. The calibration is referenced to an IEC-711 ear simulator and comprises the following frequencies: 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, 8000 Hz. PMID:8552975

  13. Are H and stretch reflexes in hemiparesis reproducible and correlated with spasticity?

    PubMed

    Levin, M F; Hui-Chan, C

    1993-02-01

    The measurement of spasticity has always presented a problem to clinicians and researchers alike. As yet, there is no literature addressing the reproducibility of the existing barrage of clinical evaluations of spasticity and reflex measurement. Also not clear is whether or not a systematic relationship might exist between these multiple indices of spasticity. After delineating the differences in spasticity scores and reflex functions between spastic and normal states, the aims of this study were to examine the reliability of these measurements in hemiparetic subjects, and the correlation between altered reflex functions and clinically measured spasticity. An aggregate of lower limb reflexes was compared between ten spastic hemiparetic and seven age-matched normal subjects. Lower limb reflexes examined were: (1) the ratio of maximal H reflex to M response (H/M ratio), (2) the inhibition of the H reflex during vibration (Hvib/Hctl ratio), and (3) soleus stretch reflexes (SR/M ratio). H and stretch reflex latencies were shorter (P < 0.05), and reflex amplitudes were significantly greater (H/M ratios, P < 0.05; SR/M areas, P < 0.005) in spastic subjects. While H/M ratios, Hvib/Hctl ratios, SR/M areas and SR onset angles were highly reproducible, only some physiological measurements showed consistent but non-significant relationships with clinical spasticity. The decreased reflex latencies and increased reflex responses in the hemiparetic subjects suggested that spasticity may be related to reduced reflex thresholds. The physiological measurements and clinically assessed tone were both valid and reproducible, indicating that they can be used to evaluate the long-term effects of therapeutic intervention.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8437021

  14. No evidence hip joint angle modulates intrinsically produced stretch reflex in human hopping.

    PubMed

    Gibson, W; Campbell, A; Allison, G

    2013-09-01

    Motor output in activities such as walking and hopping is suggested to be mediated neurally by purported stretch reflex augmentation of muscle output. Reflex EMG activity during these tasks has been frequently investigated in the soleus muscle; with alterations in reflex amplitude being associated with changes in hip joint angle/phase of the gait cycle. Previous work has focussed on reflex activity induced by an artificial perturbation or by induction of H-reflexes. As such, it is currently unknown if stretch reflex activity induced intrinsically (as part of the task) is modulated by changes in hip joint angle. This study investigated whether hip joint angle modulated reflex EMG 'burst' activity during a hopping task performed on a custom-built partially reclined sleigh. Ten subjects participated; EMG and kinematic data (VICON motor capture system) was collected for each hop cycle. Participants completed 5 sets of 30s of self-paced hopping in (1) hip neutral and (2) hip 60° flexion conditions. There was no difference in EMG 'burst' activity or in sagittal plane kinematics (knee/ankle) in the hopping task between the two conditions. The results indicate that during a functional task such as hopping, changes in hip angle do not alter the stretch reflex-like activity associated with landing. PMID:23791780

  15. [Electrostimulation-induced stapedius reflex. Presentation of a standardized procedure and results of clinical studies].

    PubMed

    Steinhart, H; Nagel, D

    1995-03-01

    The electro-tactile elicitation of the stapedius muscle reflex is well known but not used in clinical practice. Despite a complex reflex pathway in the brainstem, correlations between reflex parameters and neurological impairments are still possible. We have developed a method for eliciting the electro-tactile stapedius muscle reflex and automatic analysis of different reflex parameters by using an analog-digital converter and a personal computer-integrated signal analysis system. Clinical investigations were carried out with a group of 55 healthy persons (control group), 13 patients with central facial palsies, 51 patients with multiple sclerosis (MS group) and 24 patients with absent acoustic-stapedius muscle reflexes. Findings demonstrated that the latency between stimulus and beginning of the reflex (L1) was significantly longer in the MS group compared with the control group. The best parameter for dividing the MS group into groups with different disability scores was S, which was the parameter for the increase in the L1 growth curve at different stimulus levels. Reproduction of the parameter S in repeated tests with different locations of the stimulus-electrode was excellent. PMID:7759297

  16. [Laryngeal and larynx-associated reflexes].

    PubMed

    Ptok, M; Kühn, D; Miller, S; Jungheim, M; Schroeter, S

    2016-06-01

    The laryngeal adductor reflex and the pharyngoglottal closure reflex protect the trachea and lower respiratory tract against the entrance of foreign material. The laryngeal expiration reflex and the cough reflex serve to propel foreign material, which has penetrated in the cranial direction. The inspiration reflex, the sniff reflex, and the swallowing reflex are further larynx-associated reflexes. In patients with dysphagia the laryngeal adductor reflex can be clinically tested with air pulses. The water swallow test serves to show the integrity of the cough reflex. The sniff reflex is useful to test the abduction function of the vocal folds. Future studies should address laryngeal reflexes more specifically, both for a better understanding of these life-supporting mechanisms and to improve diagnostic procedures in patients with impaired laryngeal function. PMID:27240793

  17. Monopolar recording of H reflexes at various sites.

    PubMed

    Little, J W; Hayward, L F; Halar, E

    1989-01-01

    Various monopolar recording electrode sites have been used to record H reflexes and M responses. This investigation revealed a decrease in maximum M response amplitude accompanied by an increase in the H/M amplitude ratio as the active recording electrode was positioned more distally, below the gastrocnemii muscle bellies. H and M latencies were also significantly longer at the most distal recording site, but the latency difference is relatively independent of recording site. Serial variation was least at the most proximal recording site for an immobilized ankle. For an unrestrained ankle, serial variation was greater, but was least at the most distal site. The standard recording site, midway between knee and ankle, was not the best site for minimizing serial variation, and it was the least sensitive to vibration-induced reflex excitability changes. For serial testing of H reflex excitability, an immobilized ankle and measured proximal and distal recording sites are recommended. PMID:2752953

  18. The use of bilateral blink reflexes in intraoperative monitoring of facial-trigeminal nerves in cerebello-pontine angle operations

    PubMed Central

    Jamshidi Fard, Alireza; Dalvandi, Mohsen; Mohammadi, Alireza

    2012-01-01

    Abstract: Background: Intraoperative monitoring (IOM) of facial nerve is routinely recommended in Cerebello-Pontine Angle (CP Angle) operations. Middle cranial nerves: V, VII, VIII are mainly involved since these nerves are sometimes separated by the tumor mass causing an inadvertent section of the facial nerve. Blink reflex could be elicited by stimulation of supraorbital branch of Trigeminal nerve which elicits EMG responses in facial muscles. Threshold, amplitude, latencies, pre-post surgery are strong predictors of postoperative facial function. Methods: In 17 cases of CP angle tumors (24-43 mm, by MRI) approached suboccipitally, we performed bilateral blink reflexes pre/intra/post surgery. The setup consisted of a Nicolet Endeavor IOM system( VIASYS Healthcare, 2005, USA) with the ability to perform several voltage/current stimulations and recordingsup to 20 Evoked Potentials and Electromyography (EMG) simultaneously. Bilateral blink reflexes were evoked by stimulation of bilateral supraorbital nerves. Stimulating pulses of 0.1 ms duration and 5-20 mA intensity were applied percutaneously at the intervals of 10-20 s. The orbicularis oculi muscle responses were recorded using surface electrodes. Early EMG responses (R1) and later reflex activities (R2) were elicited ipsi/contra laterally (R1/2-i/c). Every five successive trials were superimposed and the lowest latencies were used for comparison. Blink reflexes of each subject considered pathologic if: 1- Loss of R1-i,c to the operation side, latencies are more than 15 ms or side differences are 3 ms or more; 2- Loss of R2-i, latencies are more than 50 ms or side differences are 10 ms or more. 3- Loss of R2-c, latencies are more than 55 ms or side differences are 10 ms or more. Recordings were performed 2-3 days before operaration, intraoperative and 21 days after operation. Results: Before surgery, in 15 subjects, the amplitudes of R1-i responses were significantly lower than the R1-c. However, in 2 cases with

  19. Females Exhibit Shorter Paraspinal Reflex Latencies than Males in Response to Sudden Trunk Flexion Perturbations

    PubMed Central

    Miller, Emily M.; Slota, Gregory P.; Agnew, Michael J.; Madigan, Michael L.

    2010-01-01

    Background Females have a higher risk of experiencing low back pain or injury than males. One possible reason for this might be altered reflexes since longer paraspinal reflex latencies exist in injured patients versus healthy controls. Gender differences have been reported in paraspinal reflex latency, yet findings are inconsistent. The goal here was to investigate gender differences in paraspinal reflex latency, avoiding and accounting for potentially gender-confounding experimental factors. Methods Ten males and ten females underwent repeated trunk flexion perturbations. Paraspinal muscle activity and trunk kinematics were recorded to calculate reflex latency and maximum trunk flexion velocity. Two-way mixed model ANOVAs were used to determine the effects of gender on reflex latency and maximum trunk flexion velocity. Findings Reflex latency was 18.7% shorter in females than in males (P=0.02) when exposed to identical trunk perturbations, and did not vary by impulse (P=0.38). However, maximum trunk flexion velocity was 35.3% faster in females than males (P=0.01) when exposed to identical trunk perturbations, and increased with impulse (P<0.01). While controlling for differences in maximum trunk flexion velocity, reflex latency was 16.4% shorter in females than males (P=0.04). Implications The higher prevalence of low back pain and injury among females does not appear to result from slower paraspinal reflexes. PMID:20359800

  20. Operant conditioning of the soleus H-reflex does not induce long-term changes in the gastrocnemius H-reflexes and does not disturb normal locomotion in humans.

    PubMed

    Makihara, Yukiko; Segal, Richard L; Wolpaw, Jonathan R; Thompson, Aiko K

    2014-09-15

    In normal animals, operant conditioning of the spinal stretch reflex or the H-reflex has lesser effects on synergist muscle reflexes. In rats and people with incomplete spinal cord injury (SCI), soleus H-reflex operant conditioning can improve locomotion. We studied in normal humans the impact of soleus H-reflex down-conditioning on medial (MG) and lateral gastrocnemius (LG) H-reflexes and on locomotion. Subjects completed 6 baseline and 30 conditioning sessions. During conditioning trials, the subject was encouraged to decrease soleus H-reflex size with the aid of visual feedback. Every sixth session, MG and LG H-reflexes were measured. Locomotion was assessed before and after conditioning. In successfully conditioned subjects, the soleus H-reflex decreased 27.2%. This was the sum of within-session (task dependent) adaptation (13.2%) and across-session (long term) change (14%). The MG H-reflex decreased 14.5%, due mainly to task-dependent adaptation (13.4%). The LG H-reflex showed no task-dependent adaptation or long-term change. No consistent changes were detected across subjects in locomotor H-reflexes, EMG activity, joint angles, or step symmetry. Thus, in normal humans, soleus H-reflex down-conditioning does not induce long-term changes in MG/LG H-reflexes and does not change locomotion. In these subjects, task-dependent adaptation of the soleus H-reflex is greater than it is in people with SCI, whereas long-term change is less. This difference from results in people with SCI is consistent with the fact that long-term change is beneficial in people with SCI, since it improves locomotion. In contrast, in normal subjects, long-term change is not beneficial and may necessitate compensatory plasticity to preserve satisfactory locomotion. PMID:24944216

  1. Brain lesions affect penile reflexes.

    PubMed

    Monaghan, E P; Arjomand, J; Breedlove, S M

    1993-03-01

    Electrolytic lesions of several potential brain afferents to the spinal nucleus of the bulbocavernosus (SNB) affect the display of penile reflexes. Ablation of the median and pontine raphe areas significantly potentiates the expression of cups and flips. Animals with a bilateral lesion of the paraventricular nucleus of the hypothalamus have a shorter latency to the first erection but otherwise display normal reflex behavior. Although bilateral destruction of the lateral vestibular nucleus (LVN) completely eliminated penile reflex activity, it also caused significant motor impairment thus clouding conclusions concerning the normal role of the LVN in penile reflex behavior. These and other results support the hypothesis that these brain regions which project to the SNB region normally modulate spinal reflex behavior of the rat penis. PMID:8440513

  2. [Reflex seizures, cinema and television].

    PubMed

    Olivares-Romero, Jesús

    2015-12-16

    In movies and television series are few references to seizures or reflex epilepsy even though in real life are an important subgroup of total epileptic syndromes. It has performed a search on the topic, identified 25 films in which they appear reflex seizures. Most seizures observed are tonic-clonic and visual stimuli are the most numerous, corresponding all with flashing lights. The emotions are the main stimuli in higher level processes. In most cases it is not possible to know if a character suffers a reflex epilepsy or suffer reflex seizures in the context of another epileptic syndrome. The main conclusion is that, in the movies, the reflex seizures are merely a visual reinforcing and anecdotal element without significant influence on the plot. PMID:26662874

  3. Quantifying the effects of voluntary contraction and inter-stimulus interval on the human soleus H-reflex

    PubMed Central

    Estabrooks, Kristen L.; McGie, Steven; Roth, Michael J.; Jones, Kelvin E.

    2016-01-01

    The human soleus H-reflex is commonly tested as an indicator of the reflex excitability of the calf muscles with infrequent stimuli to a subject seated and at rest. However, the reflex varies widely with the level of voluntary contraction and with the time history of stimulation. We studied two aspects of this variation. Antagonist (tibialis anterior) activation decreases the response, while increasing agonist (soleus) activation increases the H-reflex to a peak after which it declines. In subjects with large H-reflexes at rest, the reflex peaked at low levels of contraction. In contrast, in subjects with small H-reflexes at rest, the reflex peaked at higher levels of contraction for reasons that were elucidated using a realistic computer model. A parabolic curve fitted the maximum amplitude of the H-reflex in the model and over the entire range of contractile levels studied. The second aspect studied was post-activation depression or homosynaptic depression (HD), which has been described previously as a reduction of a second H-reflex elicited shortly after an initial reflex. We confirmed the presence of HD in resting, seated subjects for intervals up to 4 s. However, by voluntarily activating the soleus muscle, HD was drastically reduced when seated and abolished when standing. This suggests that HD may be absent in normal, functional movements and perhaps in clinical conditions that alter H-reflexes. Meaningful, quantitative measurements of reflex excitability can only be made under voluntary activity that mimics the condition of interest. PMID:17562030

  4. Measurement of a single tendon reflex in conjunction with a myogram - The second manned Skylab mission

    NASA Technical Reports Server (NTRS)

    Baker, J. T.; Nicogossian, A. E.; Hoffler, G. W.; Johnson, R. L.

    1976-01-01

    A generalized hyperreflexia was observed in Skylab 2 crew members immediately postflight. Duration of the Achilles reflex was significantly shortened. Further shortening was observed on the fourth day after recovery. At the 16th and 29th postrecovery days a lengthening of the reflex was observed in two of the three crew members. The muscle potential intervals were shortened immediately postflight and remained shortened throughout the 29 day postflight evaluation period.

  5. Tonic vibration reflex in Holmes-Adie syndrome: an electrophysiological study

    PubMed Central

    Abbruzzese, Giovanni; Abbruzzese, Michele; Favale, Emilio; Ratto, Sandro

    1979-01-01

    The pathophysiological mechanisms underlying benign areflexia were studied in six patients with Holmes-Adie syndrome. No impairment of sensory conduction velocity of sural nerve was found. A normal tonic vibration reflex was obtained in all patients. H reflex was absent in five patients, but responses like F waves were recorded in three subjects. These findings suggest that muscle spindles are not affected and that spinal motoneurone excitability is normal. PMID:512669

  6. Slipped and lost extraocular muscles.

    PubMed

    Lenart, T D; Lambert, S R

    2001-09-01

    A slipped or lost muscle should be considered in the differential diagnosis of a patient presenting with a marked limitation of duction and inability to rotate the eye beyond the midline. Loss of a rectus muscle can occur after strabismus surgery, trauma, paranasal sinus surgery, orbital surgery, or retinal detachment surgery. The extraocular rectus muscle most frequently slipped or lost is the medial rectus muscle. Forced ductions, active force generation, saccadic velocity studies, differential intraocular pressure measurements, and orbital imaging studies may aid in identifying a slipped or lost muscle. However, no single diagnostic test provides absolute reliability for determining a lost muscle. Slipped muscles develop when the muscular capsule is imbricated without including the muscle or muscle tendon during strabismus surgery. When the capsule is reattached to the sclera, the tendon and muscle are then free to slip posteriorally from the site of attachment. Slipped muscles are retrieved by following the thin avascular muscle capsule posteriorally until the muscle is identified. A lost muscle can be found using a traditional conjunctival approach, by an external orbitotomy, or by an endoscopic transnasal approach. Although many diagnostic maneuvers are useful in identifying a lost rectus muscle, the oculocardiac reflex is the most important. Once the lost muscle is identified, the muscle should be imbricated with a nonabsorbable synthetic suture and securely reattached to the globe. PMID:11705143

  7. Differences in motor activation of voluntary and reflex cough in humans

    PubMed Central

    Lasserson, D; Mills, K; Arunachalam, R; Polkey, M; Moxham, J; Kalra, L

    2006-01-01

    Objectives To study motor activation patterns of voluntary and reflex cough adjusted for cough flow rates. Methods Surface electromyography (EMG) and cough flow rate were measured in 10 healthy volunteers. Voluntary cough was assessed for 20 efforts in each quintile of increasing cough flow rate. Reflex cough was assessed for 25 efforts produced by nebulised l‐tartaric acid. EMG was recorded over the expiratory (rectus abdominis, obliques, lower intercostals) and accessory (trapezius, pectoralis major, deltoid, latissimus dorsi) muscles. EMG activity, burst duration and onset were compared for each quintile of voluntary cough, and between voluntary and reflex cough matched for cough flow rate. Results EMG activity and burst duration of expiratory and accessory muscles during voluntary cough increased in proportion to cough flow. Expiratory muscles had longer EMG burst duration (difference 68 ms (95% CI 34 to 102), p<0.01) and earlier onset of EMG activity (difference 44 ms (95% CI 20 to 68), p<0.0001) compared with accessory muscles. EMG activity in all muscles was increased (mean 110.2% v 56.1%, p<0.001) and burst duration (mean 206 ms v 280 ms, p = 0.013) decreased in reflex cough compared with voluntary cough of equal flow rate. There were no differences in EMG onset (difference 8 ms (95% CI 25 to −9) or burst duration (difference 27 ms (95% CI 58 to −4) between expiratory and accessory muscles. Conclusions Functional organisation of motor activity differs between voluntary and reflex cough. Voluntary cough is characterised by sequential activation whereas reflex cough is associated with early and simultaneous activation of expiratory and accessory muscles. PMID:16601089

  8. Reflex responses at the human ankle: the importance of tendon compliance.

    PubMed Central

    Rack, P M; Ross, H F; Thilmann, A F; Walters, D K

    1983-01-01

    Subjects with active stretch reflexes responded to an imposed sinusoidal movement of the ankle joint with a reflex force whose amplitude and timing varied widely with changes in the frequency of movement. At some frequency between 6 and 8 Hz, the reflex force tended to offset the non-reflex component of resistance, and thus to reduce the total resistance to movement. At this frequency the reflex response was particularly vigorous, with a deep modulation of electromyogram (e.m.g.) activity and a displacement of the joint stiffness vectors far from their high frequency values. The total resistance to movement might then be small, or it might be zero, or the reflex might actually assist the movement. As the frequency of movement was decreased through this critical range, the timing of the reflex response to movement changed rapidly with an abrupt advancement of the triceps surae e.m.g. signal, and a wide separation of the joint stiffness vectors as they passed close to the origin. This result was attributed to a changing distribution of the movement between the muscle fibres and an elastic Achilles tendon. It was assumed that at most frequencies the muscle fibres resisted extension, so that a major part of the imposed movement went into stretching the tendon; when, however, at 6-8 Hz, the reflex response was so timed as to reduce or abolish the resistance of the muscle fibres, more of the movement would take place in them. The muscle spindles would 'see' this larger movement of the muscle fibres, and generate correspondingly more reflex activity. A simplified model of the muscle-tendon combination behaves in a way that supports this view, and the available information about the human Achilles tendon indicates that it is sufficiently compliant for such an explanation. Therefore, movements imposed on the ankle joint would not necessarily be 'seen' by the muscle spindles, since they would be modified by transmission through a compliant tendon. By assuming a value for the

  9. Deficits in Lower Limb Muscle Reflex Contraction Latency and Peak Force Are Associated With Impairments in Postural Control and Gross Motor Skills of Children With Developmental Coordination Disorder: A Cross-Sectional Study.

    PubMed

    Fong, Shirley S M; Ng, Shamay S M; Guo, X; Wang, Yuling; Chung, Raymond C K; Stat, Grad; Ki, W Y; Macfarlane, Duncan J

    2015-10-01

    This cross-sectional, exploratory study aimed to compare neuromuscular performance, balance and motor skills proficiencies of typically developing children and those with developmental coordination disorder (DCD) and to determine associations of these neuromuscular factors with balance and motor skills performances in children with DCD.One hundred thirty children with DCD and 117 typically developing children participated in the study. Medial hamstring and gastrocnemius muscle activation onset latencies in response to an unexpected posterior-to-anterior trunk perturbation were assessed by electromyography and accelerometer. Hamstring and gastrocnemius muscle peak force and time to peak force were quantified by dynamometer, and balance and motor skills performances were evaluated with the Movement Assessment Battery for Children (MABC).Independent t tests revealed that children with DCD had longer hamstring and gastrocnemius muscle activation onset latencies (P < 0.001) and lower isometric peak forces (P < 0.001), but not times to peak forces (P > 0.025), than the controls. Multiple regression analysis accounting for basic demographics showed that gastrocnemius peak force was independently associated with the MABC balance subscore and ball skills subscore, accounting for 5.7% (P = 0.003) and 8.5% (P = 0.001) of the variance, respectively. Gastrocnemius muscle activation onset latency also explained 11.4% (P < 0.001) of the variance in the MABC ball skills subscore.Children with DCD had delayed leg muscle activation onset times and lower isometric peak forces. Gastrocnemius peak force was associated with balance and ball skills performances, whereas timing of gastrocnemius muscle activation was a determinant of ball skill performance in the DCD population. PMID:26469921

  10. [Electrically induced cutaneo-muscular reflex from the m. extensor digitorum brevis].

    PubMed

    Piepenbrock, N; Hess, C W; Ludin, H P; Mumenthaler, M

    1987-06-01

    We recorded the cutaneo-muscular reflexes in 90 normal subjects from the extensor digitorum brevis muscle following electrical stimulation at the second toe. In 88 subjects an early and a late EMG response were obtained. The mean latency of the second reflex response was 91.9 +/- 12.1 ms and the mean duration was 27.3 +/- 11.6 ms. However, there was considerable variability of the interindividual amplitudes. Comparison of the age related changes in the latencies of the first and second reflexes yielded results consistent with the transcortical or spino-bulbo-spinal hypothesis. PMID:3111831

  11. Human flexor reflex modulation during cycling.

    PubMed

    Brown, D A; Kukulka, C G

    1993-04-01

    1. Human flexor reflex (HFR) responses were elicited during ergometer cycling in neurologically intact humans with the objective of understanding the influence of lower limb muscle activity on phase-dependent reflex modulation during movement. The experimental setup permitted control over background muscle activity and stimulus intensity without significantly interfering with the cycling motion. 2. All experiments involved cycling on an ergometer at a set rate and workload. A 333-Hz, 15-ms pulse train of electrical stimulation was randomly delivered to the skin over the tibial nerve at the ankle at selected lower limb positions. In the first group of experiments, subjects were stimulated at six cycling phases while pedaling with normal, phasic ankle activity (free-form cycling). The second and third group of experiments involved stimulation under static limb positioning conditions and during active pedaling while subjects were asked to maintain a consistent background level of isolated tibialis anterior (TA) or soleus (SOL) electromyographic (EMG) activity. 3. Control criteria were established to assure similar isolated muscle EMG levels and sensory stimulation intensities throughout the experiments. With the aid of the application of a lower extremity brace and visual EMG feedback, SOL and TA activity were confined by the subject to a narrow range during the task of cycling. Stimulus consistency was achieved through maintenance of flexor hallucis brevis M-waves to within an envelope encompassing the mean value +/- 5% of the maximum M-wave amplitude in all experimental conditions. 4. When the subject's limb was statically positioned, the HFR responses in the SOL muscle showed no significant changes in pattern when compared at various limb positions. During cycling with consistent SOL activity, a response waveform pattern of early-latency-long-duration depression was followed by a later-latency facilitation response in all positions except the initial power phase

  12. [Reflexes, instincts, emotions and passions].

    PubMed

    Sánchez, Alberto Portera

    2008-01-01

    In animals of the same species, the reflexes, having evolved similarly, in a few milliseconds, automatically activate the corresponding reflex arch and without the intervention of the animal generate the adequate response: medullary, mesencephalic or trans-hemispheric. These neurophysiological functions have allowed the animals to be free from predators and increasy their longevity and, as a consequence, the appearance of numerous species during millions of years. A further step in the reflexes evolution, the instincts emerged and their activity, a result of neuro-hormonal functions, stimulates the male's sexual appetite when the females are receptive for their copulation and fecundation. PMID:18924359

  13. Soleus stretch reflex during cycling.

    PubMed

    Grey, M J; Pierce, C W; Milner, T E; Sinkjaer, T

    2001-01-01

    The modulation and strength of the human soleus short latency stretch reflex was investigated by mechanically perturbing the ankle during an unconstrained pedaling task. Eight subjects pedaled at 60 rpm against a preload of 10 Nm. A torque pulse was applied to the crank at various positions during the crank cycle, producing ankle dorsiflexion perturbations of similar trajectory. The stretch reflex was greatest during the power phase of the crank cycle and was decreased to the level of background EMG during recovery. Matched perturbations were induced under static conditions at the same crank angle and background soleus EMG as recorded during the power phase of active pedaling. The magnitude of the stretch reflex was not statistically different from that during the static condition throughout the power phase of the movement. The results of this study indicate that the stretch reflex is not depressed during active cycling as has been shown with the H-reflex. This lack of depression may reflect a decreased susceptibility of the stretch reflex to inhibition, possibly originating from presynaptic mechanisms. PMID:11232549

  14. [Reflex sympathetic dystrophy].

    PubMed

    Oliveira, Marta; Manuela, Manuela; Cantinho, Guilhermina

    2011-01-01

    Reflex Sympathetic Dystrophy is rare in pediatrics. It is a complex regional pain syndrome, of unknown etiology, usually post-traumatic, characterized by dysfunctions of the musculoskeletal, vascular and skin systems: severe persistent pain of a limb, sensory and vascular alterations, associated disability and psychosocial dysfunction. The diagnosis is based in high clinical suspection. In children and adolescents there are aspects that are different from the adult ones. Excessive tests may result in worsening of the clinical symptoms. Bone scintigraphy can help. Pain treatment is difficult, not specific. Physical therapies and relaxation technics give some relief. Depression must be treated. This syndrome includes fibromyalgia and complex regional pain syndrome type I. We present a clinical report of an adolescent girl, referred for pain, cold temperature, pallor and functional disability of an inferior limb, all signals disclosed by a minor trauma. She had been diagnosed depression the year before. The bone scintigraphy was a decisive test. The treatment with gabapentin, C vitamin, physiotherapy and pshycotherapy has been effective. PMID:22713207

  15. Intracranial causes of ophthalmoplegia: the visual reflex pathways.

    PubMed

    Stalcup, Seth T; Tuan, August S; Hesselink, John R

    2013-01-01

    The gathering of visual information is a complex process that relies on concerted movements of the eyes, and cranial nerves II-VIII are at least partially involved in the visual system. The cranial nerves do not function in isolation, however, and there are multiple higher-order cortical centers that have input into the cranial nerves to coordinate eye movement. Among the functions of the cortical reflex pathways are (a) controlling vertical and horizontal gaze in response to vestibular input to keep the eyes focused on an object as the head moves through space, and (b) controlling rapid, coordinated eye movement to a new visual target (saccades). There are also reflex pathways connecting the cranial nerves involved in vision that produce consensual blinking of the eyes in response to corneal stimulation of one eye and consensual pupillary constriction in response to light input on one pupil. A variety of intracranial pathologic conditions, including benign and malignant neoplasms, infection, trauma, autoimmune diseases, vascular anomalies, degenerative diseases, and inherited-congenital disorders, can disrupt the cranial nerves and visual reflex pathways. This disruption can manifest in myriad ways-for example, as extraocular muscle paresis, afferent pupillary defect, oculosympathetic paresis (Horner syndrome), internuclear ophthalmoplegia, dorsal midbrain (Parinaud) syndrome, or loss of the corneal reflex. Knowledge of the function and anatomy of the cranial nerves and visual reflex pathways, coupled with selection of the proper magnetic resonance pulse sequence, will allow the radiologist to order appropriate imaging of the involved cranial nerve or visual reflex pathway based on the patient's symptoms and thereby play an essential role in establishing the diagnosis and planning appropriate therapy. PMID:24025940

  16. Normal values of patellar and ankle tendon reflex latencies.

    PubMed

    Frijns, C J; Laman, D M; van Duijn, M A; van Duijn, H

    1997-02-01

    The clinical value of latency measurement of tendon reflexes in neurological patients has been reported by several authors. However, normal values are not readily comparable. In the present study, latencies and amplitudes of patellar (PTR) and ankle tendon reflexes (ATR) were measured at rest and after facilitation in 102 normal controls. A manually operated reflex hammer, tipped with electrically conductive rubber, ensured an immediate start of the sweep of the oscilloscope. Latencies showed a significant correlation with height (r = 0.70 for PTR and r = 0.72 for ATR, P < 0.0001) and to a lesser degree with age (r = 0.16 and r = 0.30, P < 0.0001). While amplitudes were highly variable, rendering them less useful for diagnostic purposes, latencies showed minimal intra-individual variability (CV 1.5 and 0.8%, respectively). Correlation of ATR-latency with the H-reflex latency of the soleus muscle was very high (r = 0.97, P < 0.0001). Comparison with three other hammer types yielded corresponding results with a hammer supplied with a piezo-electric element; however, significantly shorter latencies were found with a hammer with a microswitch, and with another hammer with a spring-contact, due to a delay from the tap on the tendon until the start of the sweep of the monitor. PMID:9107465

  17. The muscle spindle as a feedback element in muscle control

    NASA Technical Reports Server (NTRS)

    Andrews, L. T.; Iannone, A. M.; Ewing, D. J.

    1973-01-01

    The muscle spindle, the feedback element in the myotatic (stretch) reflex, is a major contributor to muscular control. Therefore, an accurate description of behavior of the muscle spindle during active contraction of the muscle, as well as during passive stretch, is essential to the understanding of muscle control. Animal experiments were performed in order to obtain the data necessary to model the muscle spindle. Spectral density functions were used to identify a linear approximation of the two types of nerve endings from the spindle. A model reference adaptive control system was used on a hybrid computer to optimize the anatomically defined lumped parameter estimate of the spindle. The derived nonlinear model accurately predicts the behavior of the muscle spindle both during active discharge and during its silent period. This model is used to determine the mechanism employed to control muscle movement.

  18. Differences in recruitment order of motor units in phasic and tonic flexion reflex in `spinal man'

    PubMed Central

    Grimby, Lennart; Hannerz, Jan

    1970-01-01

    The recruitment order of motoneurones in muscle contractions has been held to be largely constant and determined by the size of the cell. However, as shown in a previous investigation using electromyographic techniques, the order in which different motor units are activated during voluntary muscle contractions changes in normal human subjects on shifts from phasic to tonic contraction. In order to investigate these two types of activity also in cases in which the cerebral influence on the motoneurone pool is blocked, an analysis was made of the recruitment order in phasic and tonic flexion reflexes in 10 patients with total interruption of the spinal cord. The following four principles were found to apply and presumed to be generally valid for the isolated human spinal cord: (1) in the phasic exteroceptive reflex, the order of recruitment varies despite application of a standardized stimulus; (2) in the tonic reflex, the first unit to be recruited is usually the same even with widely different types of stimuli; (3) a shift from phasic to tonic reflex activation may result in considerable changes in recruitment order; (4) after facilitation by a subliminal long-lasting stimulus, the first unit to be recruited in the phasic reflex is also the first to be recruited in the tonic reflex. It is suggested that a tonic influence on the motoneurone pool is required for the presupposed constancy of the recruitment order. Images PMID:5478941

  19. Proprioceptive neuropathy affects normalization of the H-reflex by exercise after spinal cord injury

    PubMed Central

    Ollivier-Lanvin, Karen; Keeler, Benjamin E.; Siegfried, Rachel; Houlé, John D.; Lemay, Michel A.

    2009-01-01

    The H-reflex habituates at relatively low frequency (10 Hz) stimulation in the intact spinal cord, but loss of descending inhibition resulting from spinal cord transection reduces this habituation. There is a return towards a normal pattern of low-frequency habituation in the reflex activity with cycling exercise of the affected hind limbs. This implies that repetitive passive stretching of the muscles in spinalized animals and the accompanying stimulation of large (Group I and II) proprioceptive fibers has modulatory effects on spinal cord reflexes after injury. To test this hypothesis, we induced pyridoxine neurotoxicity that preferentially affects large dorsal root ganglia neurons in intact and spinalized rats. Pyridoxine or saline injections were given twice daily (IP) for 6 weeks and half of the spinalized animals were subjected to cycling exercise during that period. After 6 weeks, the tibial nerve was stimulated electrically and recordings of M and H waves were made from interosseous muscles of the hind paw. Results show that pyridoxine treatment completely eliminated the H-reflex in spinal intact animals. In contrast, transection paired with pyridoxine treatment resulted in a reduction of the frequency-dependent habituation of the H-reflex that was not affected by exercise. These results indicate that normal Group I and II afferent input is critical to achieve exercise-based reversal of hyper-reflexia of the H-reflex after spinal cord injury. PMID:19913536

  20. Restoring Walking after SCI: Operant Conditioning of Spinal Reflexes Can Help

    PubMed Central

    Thompson, Aiko K.; Wolpaw, Jonathan R.

    2014-01-01

    People with incomplete spinal cord injury (SCI) frequently suffer motor disabilities due to spasticity and poor muscle control, even after conventional therapy. Abnormal spinal reflex activity often contributes to these problems. Operant conditioning of spinal reflexes, which can target plasticity to specific reflex pathways, can enhance recovery. In rats in which a right lateral column lesion had weakened right stance and produced an asymmetrical gait, up-conditioning of the right soleus H-reflex, which increased muscle spindle afferent excitation of soleus, strengthened right stance and eliminated the asymmetry. In people with hyperreflexia due to incomplete SCI, down-conditioning of the soleus H-reflex improved walking speed and symmetry. Furthermore, modulation of EMG activity during walking improved bilaterally, indicating that a protocol that targets plasticity to a specific pathway can trigger widespread plasticity that improves recovery far beyond that attributable to the change in the targeted pathway. These improvements were apparent to people in their daily lives. They reported walking faster and farther, and noted less spasticity and better balance. Operant conditioning protocols could be developed to modify other spinal reflexes or corticospinal connections; and could be combined with other therapies to enhance recovery in people with SCI or other neuromuscular disorders. PMID:24636954

  1. Modulation of defensive reflex conditioning in snails by serotonin.

    PubMed

    Andrianov, Vyatcheslav V; Bogodvid, Tatiana K; Deryabina, Irina B; Golovchenko, Aleksandra N; Muranova, Lyudmila N; Tagirova, Roza R; Vinarskaya, Aliya K; Gainutdinov, Khalil L

    2015-01-01

    Highlights Daily injection of serotonin before a training session accelerated defensive reflex conditioning in snails.Daily injection of 5-hydroxytryptophan before a training session in snails with a deficiency of serotonin induced by the "neurotoxic" analog of serotonin 5,7-dihydroxytryptamine, restored the ability of snails to learn.After injection of the "neurotoxic" analogs of serotonin 5,6- and 5,7-dihydroxytryptamine as well as serotonin, depolarization of the membrane and decrease of the threshold potential of premotor interneurons was observed. We studied the role of serotonin in the mechanisms of learning in terrestrial snails. To produce a serotonin deficit, the "neurotoxic" analogs of serotonin, 5,6- or 5,7-dihydroxytryptamine (5,6/5,7-DHT) were used. Injection of 5,6/5,7-DHT was found to disrupt defensive reflex conditioning. Within 2 weeks of neurotoxin application, the ability to learn had recovered. Daily injection of serotonin before a training session accelerated defensive reflex conditioning and daily injections of 5-HTP in snails with a deficiency of serotonin induced by 5,7-DHT restored the snail's ability to learn. We discovered that injections of the neurotoxins 5,6/5,7-DHT as well as serotonin, caused a decrease in the resting and threshold potentials of the premotor interneurons LPa3 and RPa3. PMID:26557063

  2. Modulation of defensive reflex conditioning in snails by serotonin

    PubMed Central

    Andrianov, Vyatcheslav V.; Bogodvid, Tatiana K.; Deryabina, Irina B.; Golovchenko, Aleksandra N.; Muranova, Lyudmila N.; Tagirova, Roza R.; Vinarskaya, Aliya K.; Gainutdinov, Khalil L.

    2015-01-01

    Highlights Daily injection of serotonin before a training session accelerated defensive reflex conditioning in snails.Daily injection of 5-hydroxytryptophan before a training session in snails with a deficiency of serotonin induced by the “neurotoxic” analog of serotonin 5,7-dihydroxytryptamine, restored the ability of snails to learn.After injection of the “neurotoxic” analogs of serotonin 5,6- and 5,7-dihydroxytryptamine as well as serotonin, depolarization of the membrane and decrease of the threshold potential of premotor interneurons was observed. We studied the role of serotonin in the mechanisms of learning in terrestrial snails. To produce a serotonin deficit, the “neurotoxic” analogs of serotonin, 5,6- or 5,7-dihydroxytryptamine (5,6/5,7-DHT) were used. Injection of 5,6/5,7-DHT was found to disrupt defensive reflex conditioning. Within 2 weeks of neurotoxin application, the ability to learn had recovered. Daily injection of serotonin before a training session accelerated defensive reflex conditioning and daily injections of 5-HTP in snails with a deficiency of serotonin induced by 5,7-DHT restored the snail's ability to learn. We discovered that injections of the neurotoxins 5,6/5,7-DHT as well as serotonin, caused a decrease in the resting and threshold potentials of the premotor interneurons LPa3 and RPa3. PMID:26557063

  3. The effect of cannabinoids on the stretch reflex in multiple sclerosis spasticity.

    PubMed

    Marinelli, Lucio; Mori, Laura; Canneva, Stefania; Colombano, Federica; Currà, Antonio; Fattapposta, Francesco; Bandini, Fabio; Capello, Elisabetta; Abbruzzese, Giovanni; Trompetto, Carlo

    2016-07-01

    The aim of this observational study was to assess the efficacy of a tetrahydrocannabinol-cannabidiol (THC : CBD) oromucosal spray on spasticity using the stretch reflex in patients with multiple sclerosis (MS). Numeric rating scale (NRS) for spasticity, modified Ashworth scale (MAS), and the stretch reflex were assessed before and during treatment in 57 MS patients with spasticity eligible for THC : CBD treatment. A significant reduction in stretch reflex amplitude as well as significant reductions of NRS and MAS scores were observed. There was a low concordance between the three measures (stretch reflex, NRS, and MAS), likely related to the different aspects of muscle hypertonia assessed. Stretch reflex responders were taking a significantly higher number of puffs, whereas no differences were found in the responders by the other scales, suggesting that a higher dosage would add benefit if tolerated. The present study confirms the efficacy of cannabinoids in reducing spasticity in patients with MS, suggesting a higher sensitivity and specificity of the stretch reflex compared with other measures. As an objective and quantitative measure of spasticity, the stretch reflex is particularly useful to assess the effects of cannabinoids on spinal excitability and may play a role in future pharmacological studies. PMID:27003093

  4. How Can Hypnodontics Manage Severe Gag Reflex for Root Canal Therapy? A Case Report

    PubMed Central

    Ramazani, Mohsen; zarenejad, Nafiseh; Parirokh, Masoud; Zahedpasha, Samir

    2016-01-01

    In endodontics, severe involuntary gagging can have a severe impact on treatment procedure. There are many ways to ease the gag reflex, one of which is hypnosis. A 34-year-old male was referred for root canal treatment of a molar tooth. He had not received any dental treatments for the past nine years due to fear of severe gag reflex. Three hypnotic sessions based upon eye fixation, progressive muscle relaxation and guided imagery techniques were spent for psychosomatic management. The gag reflex was controlled and reduced to a normal level, and the required dental treatments including root canal therapy and restoration were performed successfully. This report shows that hypnosis can control gag reflex for dental treatments. PMID:27141226

  5. How Can Hypnodontics Manage Severe Gag Reflex for Root Canal Therapy? A Case Report.

    PubMed

    Ramazani, Mohsen; Zarenejad, Nafiseh; Parirokh, Masoud; Zahedpasha, Samir

    2016-01-01

    In endodontics, severe involuntary gagging can have a severe impact on treatment procedure. There are many ways to ease the gag reflex, one of which is hypnosis. A 34-year-old male was referred for root canal treatment of a molar tooth. He had not received any dental treatments for the past nine years due to fear of severe gag reflex. Three hypnotic sessions based upon eye fixation, progressive muscle relaxation and guided imagery techniques were spent for psychosomatic management. The gag reflex was controlled and reduced to a normal level, and the required dental treatments including root canal therapy and restoration were performed successfully. This report shows that hypnosis can control gag reflex for dental treatments. PMID:27141226

  6. Stretch reflex responses in the human elbow joint during a voluntary movement.

    PubMed Central

    Bennett, D J

    1994-01-01

    1. The responsiveness of the stretch reflex is modulated during human voluntary limb movements. The influence of this modulation on the limb mechanical properties (stiffness) was investigated. 2. Subjects were taught to replicate accurately a rapid (4.0 rad s-1) targeted elbow flexion movement of 1 rad. From the onset of 12% of the trials a sinusoidal position disturbance (0.05 rad) was superimposed on the normal (trained) movement trajectory. The net joint torque (muscle torque) resisting these stretches was computed from measurements of applied torque, acceleration and limb inertia. Electromyographic (EMG) responses in the triceps brachii (TB), brachialis (Br) and biceps brachii (BB) were monitored. 3. The EMG responses to sinusoidal stretches applied early in the movement were less than those responses to perturbations applied when the arm neared the target (especially in the antagonist muscle TB). These EMG responses caused fluctuations in the resistance to the perturbation (stiffness), as described below. 4. When the perturbation frequency was low (< 4 Hz) the resistance of the elbow muscles to the stretch increased as the arm approached the target (48% increase). In contrast, when the stretch frequency was 7 Hz the resistance decreased by 63%. This decrease can be explained by the increased reflex response, since at 7 Hz the reflex response is probably timed so that it assists, rather than resists, the stretching as a result of loop delays. This reflex timing was confirmed by observing that, after abruptly stopping the sinusoidal stretch, the reflex response persisted for 100 ms and was indeed in a direction that would have reduced the resistance, had the perturbation continued. 5. The time course of the net muscle stiffness was estimated for frequencies ranging from 4 to 8 Hz and for each 40 ms interval a Nyquist plot was constructed, forming a C-shaped curve as frequency was varied. The size of this curve gave a measure of the stiffness resulting from

  7. Effects of intravenous nonsteroidal antiinflammatory drugs on a C-fiber reflex elicited by a wide range of stimulus intensities in the rat.

    PubMed

    Bustamante, D; Paeile, C; Willer, J C; Le Bars, D

    1996-03-01

    A C-fiber reflex elicited by electrical stimulation within the territory of the sural nerve, was recorded from the ipsilateral biceps femoris muscle in anesthetized rats. The temporal evolution of the response was studied using a constant stimulus intensity (3 x threshold) and recruitment curves were built by varying stimulus intensity from 0 to 7 x threshold. The i.v. administration of aspirin, indomethacin, ketoprofen, paracetamol (= acetaminophen) and lysine clonixinate resulted in dose-dependent depressions of the C-fiber reflex by up to 30 to 40%. By contrast, saline was ineffective. High doses of the effective drugs that produced large disturbances in heart rate and/or acid-base equilibrium were not considered in the pharmacological analysis. When a constant level of stimulation was used, different dose-dependent profiles of drug action were observed. Aspirin induced a slow and gradual depression, although indomethacin, ketoprofen and paracetamol produced a peak effect within the first 10-min period and then reached a steady state phase for up to 30 min. The depressive effects of lysine clonixinate appeared more stable. When recruitment curves were built with a range of nociceptive stimulus intensities, all the drugs produced a dose-dependent decrease in the slopes and the areas under the recruitment curves without any major modification in the thresholds. The order of potency was the same for both stimulation paradigms, e.g., aspirin < paracetamol < lysine clonixinate = ketoprofen < indomethacin. It is concluded that NSAID elicit significant antinociceptive effects at a central level, which do not depend on the existence of a hyperalgesic or inflammatory state. PMID:8786556

  8. Restoration of post-activation depression of the H-reflex by treadmill exercise in aged rats.

    PubMed

    Caron, Guillaume; Marqueste, Tanguy; Decherchi, Patrick

    2016-06-01

    The purpose of this study was to evaluate the effects of aging and chronic physical activity on the postactivation depression of the Hoffman reflex (H-reflex). The maximal amplitude H wave/maximal amplitude M wave ratio was measured, and the rate-sensitive depression of the H-reflex was assessed. Measurements were performed on sedentary rats aged of 3, 6, 12, and 20 months and on animals aged of 12 and 20 months performing an incremental treadmill exercise protocol during the last eight weeks preceding the recordings. At the end of the experiment, the muscle mass and/or body mass ratio was calculated. Results indicated that the H-reflex depression of the tibialis anterior and soleus muscles were present until age of 6 and 12 months, respectively. For the tibialis anterior muscle, results also pointed out a decrease in the relative muscle mass with age and that the exercise allowed to restore the rate-sensitive depression of the H-reflex and to increase the relative muscle mass in comparison with sedentary animals. These findings clearly demonstrate that neural alteration of the spinal cord is prevented by activity in aged rats. PMID:27143422

  9. Your Muscles

    MedlinePlus

    ... Homework? Here's Help White House Lunch Recipes Your Muscles KidsHealth > For Kids > Your Muscles Print A A ... and skeletal (say: SKEL-uh-tul) muscle. Smooth Muscles Smooth muscles — sometimes also called involuntary muscles — are ...

  10. The effects of the cerebral, cerebellar and vestibular systems on the head stabilization reflex.

    PubMed

    Bademkiran, Fikret; Uludag, Burhanettin; Guler, Ayse; Celebisoy, Nese

    2016-05-01

    The head stabilization reflex (HSR) is a brain stem reflex which appears in the neck muscles in response to sudden head position changes and brings the head to its previous position. The reflex mechanism has not been understood. The afferent fibers come from cervical muscle spindles, vestibular structures, and the accessory nerve, the efferents from the accessory nerve. In this study, we aim to investigate the roles of supraspinal neural structures and the vestibular system on the HSR. The patient group consisted of 86 patients (33 cerebral cortical lesion, 14 cerebellar syndrome and 39 vestibular inexcitability or hypoexcitability); the control group was composed of 32 healthy volunteers. Concentric needle electrodes were inserted into the sternocleidomastoid muscle (SCM) and the accessory nerves were stimulated with the electrical stimulator. A reflex response of about 45-55 ms was obtained from the contralateral SCM muscle. 50 % of cases had bilateral loss whereas 37 % of cases with unilateral cerebellar lesions had an ipsilateral reflex loss. Bilateral HSR loss was detected in 84 % of cases with bilateral cerebellar lesions. Bilateral reflex loss was observed in 70 % of patients with unilateral cortical lesions and 94 % of those with bilateral vestibular dysfunction. Ipsilateral HSR loss was observed in 55 % of cases with unilateral vestibular dysfunction. It was discovered that supraspinal structures and the vestibular system may have an excitatory effect on HSR. This effect may be lost in supra-segmental and vestibular dysfunctions. The localization value of HSR was found to be rather poor in our study. PMID:26732581

  11. Influences of Changes in the Level of Support and Walking Speed on the H Reflex of the Soleus Muscle and Circulatory Dynamics on Body Weight-supported Treadmill Training: Investigation in Healthy Adults

    PubMed Central

    Watanabe, Shinichi; Oya, Yosuke; Iwata, Jun; Someya, Fujiko

    2014-01-01

    [Purpose] To investigate the therapeutic usefulness of treadmill walking using a body weight support device (BWS), changes in circulatory dynamics and muscle activities with various levels of support were investigated. [Subjects and Methods] The subjects were divided into 3 groups: 20% BWS, 40% BWS, and full body weight (FBW). The subjects walked at maximum and normal speeds. Under each condition, H and M waves and skin temperature before and after walking and changes in the heart rate during walking were measured. [Results] The heart rate continued to increase after 3 minutes of FBW at the maximum walking speed, but a steady state was reached after 3 minutes under the other walking conditions. Regarding skin temperature, no significant difference from that at rest was noted 30 minutes after walking at the normal speed, but it was significantly higher than that at rest at 30 minutes after walking at the maximum speed. The H/M ratio was significantly higher after walking at the maximum walking speed in the FBW and 20% BWS groups compared with the 40% BWS groups. [Conclusion] Treatment with 40% BWS at the maximum walking speed was safe for the circulatory system and may be effective in elevating the skin temperature for a prolonged period compared with the effects of the other walking conditions at normal speed. PMID:25276013

  12. The amplitude of interlimb cutaneous reflexes in the leg is influenced by fingertip touch and vision during treadmill locomotion.

    PubMed

    Forero, Juan; Misiaszek, John E

    2015-06-01

    Light touch at the fingertip has been shown to influence postural control during standing and walking. Interlimb cutaneous reflexes have been proposed to provide a neural link between the upper and lower limbs to assist in interlimb coordination during activities such as walking. In this study, we tested the hypothesis that cutaneous sensory pathways linking the arm and leg will be facilitated if subjects use light touch to assist with postural control during treadmill walking. To test this, interlimb cutaneous reflexes from the median nerve, serving the skin contact region, and radial nerve, serving an irrelevant sensory territory, were tested in the legs of subjects walking on treadmill in an unstable environment. Interlimb cutaneous reflexes were tested while subjects (a) touched or (b) did not touch a stable contact with their fingertip, and while the eyes were either (c) open or (d) closed. Reflexes arising from both nerves were facilitated when vision was removed that was then ameliorated when touch was provided. These changes in reflex amplitude during the eyes closed conditions were mirrored by changes in background muscle activity. We suggest that this facilitation of interlimb reflexes from both nerves arises from a generalized increase in excitability related to the postural anxiety of walking on a treadmill with the eyes closed, which is then restored by the provision of light touch. However, the influence of touch when the eyes were open differed depending upon the nerve stimulated. Radial nerve reflexes in the legs were suppressed when touch was provided, mirroring a suppression in the background muscle activity. In contrast, median nerve reflexes in the leg were larger when touch was provided with the eyes open, despite a suppression of background muscle activity. This nerve-specific effect of touch on the amplitude of the interlimb cutaneous reflexes suggests that touch sensory information from the median nerve was facilitated when that input was

  13. Excitability of the soleus reflex arc during intensive stretch-shortening cycle exercise in two power-trained athlete groups.

    PubMed

    Avela, Janne; Finni, Jarkko; Komi, Paavo V

    2006-07-01

    In several explosive types of sport events the leg extensor muscles are subjected to very high impact loads. Thus, extreme requirements exist for the neuromuscular system to develop sufficient muscle stiffness in the lower extremities in order to tolerate these high impact loads. Therefore, it would be challenging to measure reflex modulation during high impact activities, and with different athlete populations. In the present experiment, H-reflex and short latency reflex (M1) sensitivity was measured during drop jump exercises among high jumpers and sprinters. The changes in both reflex peak-to-peak amplitudes showed a significant (P < 0.05) reduction towards the end of the exercise for the sprinters. In addition, the same subject group showed a remarkable increase in serum creatine kinase (CK) activity 2 h after the jumps. Similar changes could not be observed for the high jumpers. These results clearly indicate different neural adaptation strategies for the two athlete groups. Reduction in H-reflex sensitivity and an increase in CK-activity in sprinters were taken as evidence for presynaptic inhibition, probably induced by substances related to muscle damage. Since high jump training includes more high impact loading, it was assumed that it could lead to some structural adaptation and, thus, prevents exercise induced reflex modification to a certain extent. PMID:16763835

  14. Effects of movement-related afferent inputs on spinal reflexes evoked by transcutaneous spinal cord stimulation during robot-assisted passive stepping.

    PubMed

    Masugi, Yohei; Kawashima, Noritaka; Inoue, Daisuke; Nakazawa, Kimitaka

    2016-08-01

    Studies of robot-assisted passive stepping paradigms have reported that movement-related afferent inputs strongly inhibit the excitability of the Hoffmann (H) reflex in the soleus (Sol) during walking. However, it is unknown if movement-related afferent inputs have the same effect on the excitability of spinal reflexes in the other lower-limb muscles that are involved in normal walking in healthy subjects. The aim of this study was to examine the effects of movement-related afferent inputs on the spinal reflexes in lower-limb muscles during walking. Spinal reflexes that were elicited by transcutaneous spinal cord stimulation (tSCS) were recorded during passive air standing and air stepping at three stepping velocities (stride frequencies: 14, 25, and 36 strides/min). The amplitude of the spinal reflexes was reduced in most of the recorded muscles during passive air stepping compared with air standing. Furthermore, in the Sol and lateral gastrocnemius, the amplitude of the reflexes during air stepping significantly decreased as stride frequency increased. These results demonstrate that movement-related afferent inputs inhibit spinal reflexes in the Sol and other lower-limb muscles during walking. PMID:27235576

  15. Toward reflexive climate adaptation research

    DOE PAGESBeta

    Preston, Benjamin L.; Rickards, Lauren; Fünfgeld, Hartmut; Keenan, Rodney J.

    2015-06-22

    Climate adaptation research is expanding very quickly within an increasingly reflexive society where the relationship between academia and other social institutions is in a state of flux. Tensions exist between the two dominant research orientations of research about and research for adaptation. In particular, the research community is challenged to develop processes for successfully executing transdisciplinary research for adaptation when academic institutions and researchers are largely structured around traditional, disciplinary expertise and funding models. One tool for helping to manage this tension is a third, more reflexive, orientation toward adaptation research that is emerging in the literature. Finally, this newmore » ‘research on adaptation research’ promises to help enhance understanding of the research enterprise itself and how it can become more adaptive.« less

  16. Toward reflexive climate adaptation research

    SciTech Connect

    Preston, Benjamin L.; Rickards, Lauren; Fünfgeld, Hartmut; Keenan, Rodney J.

    2015-06-22

    Climate adaptation research is expanding very quickly within an increasingly reflexive society where the relationship between academia and other social institutions is in a state of flux. Tensions exist between the two dominant research orientations of research about and research for adaptation. In particular, the research community is challenged to develop processes for successfully executing transdisciplinary research for adaptation when academic institutions and researchers are largely structured around traditional, disciplinary expertise and funding models. One tool for helping to manage this tension is a third, more reflexive, orientation toward adaptation research that is emerging in the literature. Finally, this new ‘research on adaptation research’ promises to help enhance understanding of the research enterprise itself and how it can become more adaptive.

  17. Human stretch reflex pathways reexamined

    PubMed Central

    Yavuz, Ş. Utku; Mrachacz-Kersting, Natalie; Sebik, Oğuz; Berna Ünver, M.; Farina, Dario

    2013-01-01

    Reflex responses of tibialis anterior motor units to stretch stimuli were investigated in human subjects. Three types of stretch stimuli were applied (tap-like, ramp-and-hold, and half-sine stretch). Stimulus-induced responses in single motor units were analyzed using the classical technique, which involved building average surface electromyogram (SEMG) and peristimulus time histograms (PSTH) from the discharge times of motor units and peristimulus frequencygrams (PSF) from the instantaneous discharge rates of single motor units. With the use of SEMG and PSTH, the tap-like stretch stimulus induced five separate reflex responses, on average. With the same single motor unit data, the PSF technique indicated that the tap stimulus induced only three reflex responses. Similar to the finding using the tap-like stretch stimuli, ramp-and-hold stimuli induced several peaks and troughs in the SEMG and PSTH. The PSF analyses displayed genuine increases in discharge rates underlying the peaks but not underlying the troughs. Half-sine stretch stimuli induced a long-lasting excitation followed by a long-lasting silent period in SEMG and PSTH. The increase in the discharge rate, however, lasted for the entire duration of the stimulus and continued during the silent period. The results are discussed in the light of the fact that the discharge rate of a motoneuron has a strong positive linear association with the effective synaptic current it receives and hence represents changes in the membrane potential more directly and accurately than the other indirect measures. This study suggests that the neuronal pathway of the human stretch reflex does not include inhibitory pathways. PMID:24225537

  18. Effect of thermal stress on the vestibulosympathetic reflexes in humans.

    PubMed

    Wilson, Thad E; Ray, Chester A

    2004-10-01

    Both heat stress and vestibular activation alter autonomic responses; however, the interaction of these two sympathetic activators is unknown. To determine the effect of heat stress on the vestibulosympathetic reflex, eight subjects performed static head-down rotation (HDR) during normothermia and whole body heating. Muscle sympathetic nerve activity (MSNA; peroneal microneurography), mean arterial blood pressure (MAP), heart rate (HR), and internal temperature were measured during the experimental trials. HDR during normothermia caused a significant increase in MSNA (Delta5 +/- 1 bursts/min; Delta53 +/- 14 arbitrary units/min), whereas no change was observed in MAP, HR, or internal temperature. Whole body heating significantly increased internal temperature (Delta0.9 +/- 0.1 degrees C), MSNA (Delta10 +/- 3 bursts/min; Delta152 +/- 44 arbitrary units/min), and HR (Delta25 +/- 6 beats/min), but it did not alter MAP. HDR during whole body heating increased MSNA (Delta16 +/- 4 bursts/min; Delta233 +/- 90 arbitrary units/min from normothermic baseline), which was not significantly different from the algebraic sum of HDR during normothermia and whole body heating (Delta15 +/- 4 bursts/min; Delta205 +/- 55 arbitrary units/min). These data suggest that heat stress does not modify the vestibulosympathetic reflex and that both the vestibulosympathetic and thermal reflexes are robust, independent sympathetic nervous system activators. PMID:15169749

  19. Stretch Reflex as a Simple Measure to Evaluate the Efficacy of Potential Flight Countermeasures Using the Bed Rest Environment

    NASA Technical Reports Server (NTRS)

    Cerisano, J. M.; Reschke, M. F.; Kofman, I. S.; Fisher, E. A.; Harm, D. L.

    2010-01-01

    INTRODUCTION: Spaceflight is acknowledged to have significant effects on the major postural muscles. However, it has been difficult to separate the effects of ascending somatosensory changes caused by the unloading of these muscles during flight from changes in sensorimotor function caused by a descending vestibulo-cerebellar response to microgravity. It is hypothesized that bed rest is an adequate model to investigate postural muscle unloading given that spaceflight and bed rest may produce similar results in both nerve axon and muscle tissue. METHODS: To investigate this hypothesis, stretch reflexes were measured on 18 subjects who spent 60 to 90 days in continuous 6 head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 deg at a peak velocity of approximately 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender and compared with spaceflight data. RESULTS: Although no gender differences were found, bed rest induced changes in reflex latency and CV similar to the ones observed during spaceflight. Also, a relationship between CV and loss of muscle strength in the lower leg was observed for most bed rest subjects. CONCLUSION: Even though bed rest (limb unloading) alone may not mimic all of the synaptic and muscle tissue loss that is observed as a result of spaceflight, it can serve as a working analog of flight for the evaluation of potential countermeasures that may be beneficial in mitigating unwanted changes in the major postural muscles that are observed post flight.

  20. Laryngeal reflex responses are not modulated during human voice and respiratory tasks

    PubMed Central

    Henriquez, Victor M; Schulz, Geralyn M; Bielamowicz, Steven; Ludlow, Christy L

    2007-01-01

    The laryngeal adductor response (LAR) is a protective reflex that prevents aspiration and can be elicited either by electrical stimulation of afferents in the superior laryngeal nerve (SLN) or by deflection of mechanoreceptors in the laryngeal mucosa. We hypothesized that because this reflex is life-sustaining, laryngeal muscle responses to sensory stimuli would not be suppressed during volitional laryngeal tasks when compared to quiet respiration. Unilateral electrical superior laryngeal nerve stimulation was used to elicit early (R1) and late (R2) responses in the ipsilateral thyroarytenoid muscle in 10 healthy subjects. The baseline levels of muscle activity before stimulation, R1 and R2 response occurrence and the integrals of responses were measured during each task: quiet inspiration, prolonged vowels, humming, forced inhalation and effort closure. We tested whether R1 response integrals during tasks were equal to either: (1) baseline muscle activity during the task added to the response integral at rest; (2) the response integral at rest minus the baseline muscle activity during the task; or (3) the response integral at rest. R1 response occurrence was not altered by task from rest while fewer R2 responses occurred only during effort closure and humming compared to rest. Because the R1 response integrals did not change from rest, task increases in motor neuron firing did not alter the LAR. These findings demonstrate that laryngeal motor neuron responses to sensory inputs are not gated during volitional tasks confirming the robust life-sustaining protective mechanisms provided by this airway reflex. PMID:17962327

  1. Effects of Bed Rest on Conduction Velocity of the Triceps Surae Stretch Reflex and Postural Control

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.; Wood, S. J.; Cerisano, J. M.; Kofman, I. S.; Fisher, E. A.; Esteves, J. T.; Taylor, L. C.; DeDios, Y. E.; Harm, D. L.

    2011-01-01

    Despite rigorous exercise and nutritional management during space missions, astronauts returning from microgravity exhibit neuromuscular deficits and a significant loss in muscle mass in the postural muscles of the lower leg. Similar changes in the postural muscles occur in subjects participating in long-duration bed rest studies. These adaptive muscle changes manifest as a reduction in reflex conduction velocity during head-down bed rest. Because the stretch reflex encompasses both the peripheral (muscle spindle and nerve axon) and central (spinal synapse) components involved in adaptation to calf muscle unloading, it may be used to provide feedback on the general condition of neuromuscular function, and might be used to evaluate the effectiveness of countermeasures aimed at preserving muscle mass and function during periods of unloading. Stretch reflexes were measured on 18 control subjects who spent 60 to 90 days in continuous 6 deg head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 degrees at a peak velocity of about 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender. Computerized posturography was also conducted on these same subjects before and after bed rest as part of the standard measures. Peak-to-peak sway was measured during Sensory Organization Tests (SOTs) to evaluate changes in the ability to effectively use or suppress visual, vestibular, and proprioceptive information for postural control. Although no gender differences were found, a significant increase in reflex latency and a significant decrease in CV were observed during the bed

  2. The "temporalis-inhibitory reflex" in post-lumbar puncture headache.

    PubMed

    Wallasch, T M; Niemann, U; Strenge, H

    1992-01-01

    Nausea and rigidity of the neck muscles, typical symptoms of post-lumbar puncture syndrome (PPS), may also be found in patients suffering from chronic headache of the tension-type. A decreased duration of the late suppression period of temporal muscle activity indicating a central disturbance of pericranial muscle control, can be observed in these patients. We have studied the temporalis-inhibitory reflex in 47 neurological inpatients requiring lumbar puncture. There were no significant differences of latencies or durations of temporalis silent periods between patients with and without PPS before, and 48 h following, lumbar puncture. PMID:1292957

  3. Role of the flocculus of the cerebellum in motor learning of the vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Highstein, S. M.

    1998-01-01

    Structure-function studies at the systems level are an effective method for understanding the relationship of the central nervous system to behavior. Motor learning or adaptation of the vestibulo-ocular reflex is a clear example wherein this approach has been productive. During a vestibulo-ocular reflex the brain converts a head velocity signal, transduced through the vestibular semicircular canals, into an eye movement command delivered to the extraocular muscles. If the viewed target remains on the fovea of the retina, the reflex is compensatory, and its gain, eye velocity/head velocity, is one. When the image of the viewed object slips across the retina, visual acuity decreases, and the gain of the reflex, which is no longer one, is plastically adapted or adjusted until retinal stability is restored. The anatomic substrate for this plasticity thus involves brain structures in which visual-vestibular interaction can potentially occur, as well as vestibular and visual sensory and oculomotor motor structures. Further, it has been known for many years that removal of the flocculus of the cerebellum permanently precludes further vestibulo-ocular reflex adaptation, demonstrating the involvement of the cerebellum in this behavior. Maekawa and Simpson (J Neurophysiol 1973;36: 649-66) discovered that one visual input to the flocculus involved the accessory optic system and the inferior olive. Ensuing work has demonstrated that the visual signals used to adapt the vestibulo-ocular reflex are transmitted by this accessory optic system to the flocculus and subsequently to brain stem structures involved in vestibulo-ocular reflex plasticity. Presently the inclusive list of anatomic sites involved in vestibulo-ocular reflex circuitry and its adaptive plasticity is small. Our laboratory continues to believe that this behavior should be caused by interactions within this small class of neurons. By studying each class of identified neuron and its interactions with others within

  4. Acute Effects of Kinesio Taping on Knee Extensor Peak Torque and Stretch Reflex in Healthy Adults.

    PubMed

    Yeung, Simon S; Yeung, Ella W

    2016-01-01

    Kinesio Tex tape (KT) is used to prevent and treat sports-related injuries and to enhance muscle performance. It has been proposed that the direction of taping may either facilitate or inhibit the muscle by having different effects on cutaneous receptors that modulate excitability of the motor neurons. This study had 2 goals. First, we wished to determine if KT application affects muscle performance and if the method of application facilitates or inhibits muscle performance. This was assessed by measuring isokinetic knee extension peak torque in the knee extensor. Second, we assessed neurological effects of taping on the excitability of the motor neurons by measuring the reflex latency and action potential by electromyography (EMG) in the patellar reflex. The study was a single-blind, placebo-controlled crossover trial with 28 healthy volunteers with no history of knee injuries. Participants received facilitative KT treatment, inhibitory KT treatment, or Hypafix taping of the knee extensor. There were significant differences in the peak torque between 3 treatments (F(2,54) = 4.873, P < 0.01). Post hoc analysis revealed that facilitative KT treatment resulted in higher knee extensor peak torque performance than inhibitory KT treatment (P = 0.036, effect size 0.26). There were, however, no significant differences in the reflex latency (F(2,54) = 2.84, P = 0.067) nor in the EMG values (F(2,54) = 0.18, P = 0.837) in the patellar reflex between the 3 taping applications. The findings suggest that the direction of KT application over the muscle has specific effects on muscle performance. Given the magnitude of effect is small, interpretation of clinical significance should be considered with caution. The underlying mechanism warrants further investigation. PMID:26825916

  5. [Reflexivity: a critical issue in qualitative research].

    PubMed

    de la Cuesta-Benjumea, Carmen

    2011-01-01

    Reflexivity is an English term that Spanish speaking people have to assign a technical meaning. Reflexivity expresses the conscience of researchers conscience and refers to their connection with the study's situation. It is a process by which researchers step back to critically exam the effect they have on the study and the impact of their interactions with participants. The reflexive process is embedded in all research levels and is present in all the research phases, from the research question to fieldwork, from data analysis to writing the final report. Nevertheless, the question is not so much to engage in reflective activities but to be a reflexive researcher. Reflexivity is a human ability that is present during social interactions. For this reason it is present in qualitative research. A self inquirer can be addressed as it is constructed by the relationships and interactions that are established with study participants. Reflexivity has an educational character that continues after the study is completed. PMID:21531602

  6. Portraying Reflexivity in Health Services Research.

    PubMed

    Rae, John; Green, Bill

    2016-09-01

    A model is proposed for supporting reflexivity in qualitative health research, informed by arguments from Bourdieu and Finlay. Bourdieu refers to mastering the subjective relation to the object at three levels-the overall social space, the field of specialists, and the scholastic universe. The model overlays Bourdieu's levels of objectivation with Finlay's three stages of research (pre-research, data collection, and data analysis). The intersections of these two ways of considering reflexivity, displayed as cells of a matrix, pose questions and offer prompts to productively challenge health researchers' reflexivity. Portraiture is used to show how these challenges and prompts can facilitate such reflexivity, as illustrated in a research project. PMID:26935721

  7. Generalized versus partial reflex seizures: a review.

    PubMed

    Italiano, Domenico; Ferlazzo, Edoardo; Gasparini, Sara; Spina, Edoardo; Mondello, Stefania; Labate, Angelo; Gambardella, Antonio; Aguglia, Umberto

    2014-08-01

    In this review we assess our currently available knowledge about reflex seizures with special emphasis on the difference between "generalized" reflex seizures induced by visual stimuli, thinking, praxis and language tasks, and "focal" seizures induced by startle, eating, music, hot water, somatosensory stimuli and orgasm. We discuss in particular evidence from animal, clinical, neurophysiological and neuroimaging studies supporting the concept that "generalized" reflex seizures, usually occurring in the setting of IGE, should be considered as focal seizures with quick secondary generalization. We also review recent advances in genetic and therapeutic approach of reflex seizures. PMID:24766826

  8. Paradoxical muscle movement in human standing

    PubMed Central

    Loram, Ian D; Maganaris, Constantinos N; Lakie, Martin

    2004-01-01

    In human standing, gravity causes forward toppling about the ankle joint which is prevented by activity in the soleus and gastrocnemius muscles. It has long been assumed that when people sway forwards the calf muscles are stretched and conversely that they shorten with backward sway. Consequently, for many years, two explanations for standing stabilization have flourished. First, tonic muscle activity itself may generate adequate intrinsic ankle stiffness. Second, if intrinsic ankle stiffness is inadequate, the resistance to stretch of the calf muscles may be augmented by stretch reflexes or by central control. These explanations require that the passive tissue (Achilles' tendon, foot) transmitting the calf muscle tension is stiff. However, our recent measurements have indicated that this passive tissue is not stiff during standing. Accordingly, we predicted a counterintuitive mode of control where the muscles and body must, on average, move in opposite directions (paradoxical movements). Here we use dynamic ultrasound imaging in vivo with novel automated tracking of muscle length to test our hypothesis. We show that soleus and gastrocnemius do indeed move paradoxically, shortening when the body sways forward and lengthening when the body returns. This confirms that intrinsic ankle stiffness is too low to stabilize human standing. Moreover, it shows that the increase in active tension is associated with muscle shortening. This pattern cannot be produced by muscle stretch reflexes and can only arise from the anticipatory neural control of muscle length that is necessary for balance. PMID:15047776

  9. Device for rapid quantification of human carotid baroreceptor-cardiac reflex responses

    NASA Technical Reports Server (NTRS)

    Sprenkle, J. M.; Eckberg, D. L.; Goble, R. L.; Schelhorn, J. J.; Halliday, H. C.

    1986-01-01

    A new device has been designed, constructed, and evaluated to characterize the human carotid baroreceptor-cardiac reflex response relation rapidly. This system was designed for study of reflex responses of astronauts before, during, and after space travel. The system comprises a new tightly sealing silicon rubber neck chamber, a stepping motor-driven electrodeposited nickel bellows pressure system, capable of delivering sequential R-wave-triggered neck chamber pressure changes between +40 and -65 mmHg, and a microprocessor-based electronics system for control of pressure steps and analysis and display of responses. This new system provokes classic sigmoid baroreceptor-cardiac reflex responses with threshold, linear, and saturation ranges in most human volunteers during one held expiration.

  10. Repetitive jumping and sprinting until exhaustion alters hamstring reflex responses and tibial translation in males and females.

    PubMed

    Behrens, Martin; Mau-Moeller, Anett; Wassermann, Franziska; Plewka, Antje; Bader, Rainer; Bruhn, Sven

    2015-11-01

    The incidence of anterior cruciate ligament injuries is considerably higher in females than in males and the underlying mechanisms are still under debate. Research indicates that the neuromuscular system of females and males might respond differently to the same fatigue protocol due to differences in muscle activation during movement tasks. This study analyzed sex differences in hamstring reflex responses and posterior-anterior tibial translation (TT) before and after fatiguing exercise. We measured the isolated movement of the tibia relative to the femur as a consequence of mechanically induced TT in standing subjects as well as muscle activity of the hamstrings before and after repetitive jumping and sprinting until exhaustion. Muscle fatigue delayed reflex onset latencies in females and males. A reduction in reflex responses associated with an increased TT was observed after fatiguing exercise for both sexes. Data indicate that the used fatigue protocol altered the latency and magnitude of reflex responses as well as TT in females and males. Based on the results of previous research and the outcome of this study, it might be that sex-specific effects of fatigue on reflex activity and mechanical stability of the knee depend on the kind of fatiguing exercise. PMID:25941064

  11. Effects of aging and levodopa on the laryngeal adductor reflex in rats

    PubMed Central

    Feng, Xin; Xu, Zengrui; Butler, Susan G.; Leng, Iris; Zhang, Tan; Kritchevsky, Stephen B.

    2016-01-01

    Dopaminergic neurotransmission plays an essential role in sensorimotor function, and declines with age. Previously, we found the laryngeal adductor reflex (LAR) was increased in excitation by a dopamine receptor antagonist. If this airway-protective reflex is similarly affected by aging, it will interfere with volitional control in older adults. The current study tested whether the LAR was affected by aging, and whether such deficits were reversed by levodopa administration in aging rats. We recorded thyroarytenoid (TA) muscle activity at rest and during elicitation of LAR responses by stimulation of the internal branch of the superior laryngeal nerve (iSLN) in 6-, 18- and 30-month-old rats under alpha-chloralose anesthesia. Using paired stimuli at different inter-stimulus intervals (ISIs), LAR central conditioning, resting muscle activity, and reflex latency and amplitudes were quantified. Numbers of dopaminergic neurons in the substantia nigra pars compacta (SNpc) were measured using tyrosine hydroxylase staining. We found: (1) increased resting TA muscle activity and LAR amplitude occurred with fewer dopaminergic neurons in the SNpc in 18- and 30-month-old rats; (2) decreases in LAR latency and increases in amplitude correlated with reduced numbers of dopaminergic neurons in the SNpc; (3) test responses were greater at 1000 ms ISI in 18-month-old rats compared with 6-month-old rats; and (4) levodopa administration further increased response latency but did not alter muscle activity, response amplitude, or central conditioning. In conclusion, increases in laryngeal muscle activity levels and re-flex amplitudes accompanied age reductions in dopaminergic neurons but were not reversed with levodopa administration. PMID:22824541

  12. Quantification of jaw reflexes evoked by natural tooth contact in human subjects.

    PubMed

    Ainine, Salma; Mason, Andrew G; Cadden, Samuel W

    2011-09-01

    Inhibitory jaw reflexes are believed to be important for protecting the teeth and temporo-mandibular structures from damage during sudden or forceful biting or mastication. Accordingly, alterations in these reflexes are sometimes implicated in aetiologies proposed for oro-facial pain syndromes, although the association is not well-established. We now aim to develop a method for quantifying objectively inhibitory jaw reflexes evoked by natural tooth contact. In the longer term, this may provide a new approach to examining the association of altered reflexes and clinical conditions. Eighteen subjects gave their written, informed consent, and were recruited to participate in this study. They were instructed to clench their teeth together in response to visual cues. They performed two such tasks twenty times: from the jaw postural position and from a more open position with the jaws set 10mm apart. Both tasks produced a rapid rise then stabilisation in electromyographic activity in the masseter muscle. This was always interrupted by a large inhibitory reflex starting 11.1±1.5 ms (mean±SD) after tooth contact. The inhibitions produced during the second task were similar but of significantly longer duration (24.3±6.4 vs 18.4±6.5 ms, P=0.0003, paired t-test) and greater magnitude (measured as an integral of the waveform: 1577±478 vs 1279±425%.ms, P=0.007, paired t-test). Interestingly, in a minority (13%) of the tasks, a second inhibition with a longer latency (50.9±0.9 ms) was also observed. Thus reflex responses in the masseter muscle to natural tooth contact usually consist of single inhibitory periods. In this respect they are like those induced by externally applied tooth pushing although occasionally there is a second inhibition, reminiscent of that seen with externally applied tooth taps. PMID:21419390

  13. Reflexivity: Towards a Theory of Lifelong Learning.

    ERIC Educational Resources Information Center

    Edwards, Richard; Ranson, Stewart; Strain, Michael

    2002-01-01

    The current notion of lifelong learning in policy and practice is dominated by behaviorist, adaptive accumulation of skills and qualifications. An alternative is reflexive lifelong learning, developed through social learning networks within the context of dislocation and uncertainty. It involves the reflexive practices of metacognitive analysis…

  14. Creating a Complex Schedule with "REFLEX."

    ERIC Educational Resources Information Center

    Kren, George M.; Christakes, George

    1991-01-01

    Discusses "REFLEX," a software package for scheduling. Explores the program's applications in preparing a departmental class schedule. Explains that "REFLEX" includes a filter function and some attributes of a spreadsheet but lacks the ability to interact with other databases. Concludes that the program can make scheduling easier and more…

  15. A new objective method for acquisition and quantification of reflex receptive fields.

    PubMed

    Jensen, Michael Brun; Manresa, José Biurrun; Andersen, Ole Kæseler

    2015-03-01

    The nociceptive withdrawal reflex (NWR) is a polysynaptic spinal reflex correlated with pain perception. Assessment of this objective physiological measure constitutes the core of existing methods for quantification of reflex receptive fields (RRFs), which however still suffer from a certain degree of subjective involvement. This article proposes a strictly objective methodology for RRF quantification based on automated identification of NWR thresholds (NWR-Ts). Nociceptive withdrawal reflex thresholds were determined for 10 individual stimulation sites using an interleaved up-down staircase method. Reflexes were detected from electromyography by evaluation of interval peak z scores and application of conduction velocity analysis. Reflex receptive field areas were quantified from interpolated mappings of NWR-Ts and compared with existing RRF quantifications. A total of 3 repeated measures were performed in 2 different sessions to evaluate the test-retest reliability of the various quantifications, using coefficients of repeatability (CRs) and hypothetical sample sizes. The novel quantifications based on identification of NWR-Ts showed a similar level of reliability within and between sessions, whereas existing quantifications all demonstrated worse between-session than within-session reliability. The NWR-T-based quantifications required a smaller sample size than any of the existing RRF measures to detect a clinically relevant effect in a crossover study design involving more than 1 session. Of all measures, quantification from mapping of inversed NWR-Ts demonstrated superior reliability both within (CR, 0.25) and between sessions (CR, 0.28). The study presents a more reliable and robust quantification of the RRF to be used as biomarker of pain hypersensitivity in clinical and experimental research. PMID:25599237

  16. [Complex profile of the reflex diving response].

    PubMed

    Wierzba, Tomasz H; Ropiak, Arkadiusz

    2011-01-01

    Breath-holding coupled with face cooling triggers a set of the reflex cardiovascular responses, defined as a diving reflex. The major reflex responses include a decrease in heart rate and peripheral vasoconstriction with an increase of arterial pressure to evoke central blood pooling with preferential provision of the brain and heart perfusion. Due to high individual variability and situational dependence the individual course of the reflex response is hardly predictable. Heart rhythm disturbances are the major, sometimes fatal complications of the response. This review is an outline of causing factors, circumstances, mechanisms and the effects of the diving reflex and their practical implications, including risk factors of the critical arrhythmias occurred in diving. PMID:22125213

  17. Muscle atrophy

    MedlinePlus

    Muscle wasting; Wasting; Atrophy of the muscles ... There are two types of muscle atrophy. Disuse atrophy occurs from a lack of physical activity. In most people, muscle atrophy is caused by not using the ...

  18. Muscle Disorders

    MedlinePlus

    Your muscles help you move and help your body work. Different types of muscles have different jobs. There are many problems that can affect muscles. Muscle disorders can cause weakness, pain or even ...

  19. Muscle atrophy

    MedlinePlus

    Muscle wasting; Wasting; Atrophy of the muscles ... There are two types of muscle atrophy: disuse and neurogenic. Disuse atrophy is caused by not using the muscles enough . This type of atrophy can often be ...

  20. Muscle Cramps

    MedlinePlus

    Muscle cramps are sudden, involuntary contractions or spasms in one or more of your muscles. They often occur after exercise or at night, ... to several minutes. It is a very common muscle problem. Muscle cramps can be caused by nerves ...

  1. Periodic modulation of repetitively elicited monosynaptic reflexes of the human lumbosacral spinal cord.

    PubMed

    Hofstoetter, Ursula S; Danner, Simon M; Freundl, Brigitta; Binder, Heinrich; Mayr, Winfried; Rattay, Frank; Minassian, Karen

    2015-07-01

    In individuals with motor-complete spinal cord injury, epidural stimulation of the lumbosacral spinal cord at 2 Hz evokes unmodulated reflexes in the lower limbs, while stimulation at 22-60 Hz can generate rhythmic burstlike activity. Here we elaborated on an output pattern emerging at transitional stimulation frequencies with consecutively elicited reflexes alternating between large and small. We analyzed responses concomitantly elicited in thigh and leg muscle groups bilaterally by epidural stimulation in eight motor-complete spinal cord-injured individuals. Periodic amplitude modulation of at least 20 successive responses occurred in 31.4% of all available data sets with stimulation frequency set at 5-26 Hz, with highest prevalence at 16 Hz. It could be evoked in a single muscle group only but was more strongly expressed and consistent when occurring in pairs of antagonists or in the same muscle group bilaterally. Latencies and waveforms of the modulated reflexes corresponded to those of the unmodulated, monosynaptic responses to 2-Hz stimulation. We suggest that the cyclical changes of reflex excitability resulted from the interaction of facilitatory and inhibitory mechanisms emerging after specific delays and with distinct durations, including postactivation depression, recurrent inhibition and facilitation, as well as reafferent feedback activation. The emergence of large responses within the patterns at a rate of 5.5/s or 8/s may further suggest the entrainment of spinal mechanisms as involved in clonus. The study demonstrates that the human lumbosacral spinal cord can organize a simple form of rhythmicity through the repetitive activation of spinal reflex circuits. PMID:25904708

  2. Dynamic iso-resistive trunk extension simulation: contributions of the intrinsic and reflexive mechanisms to spinal stability.

    PubMed

    Davarani, S Zeinali; Shirazi-Adl, A; Hemami, H; Mousavi, S J; Parnianpour, M

    2007-01-01

    The effects of external resistance on the recruitment of trunk muscles and the role of intrinsic and reflexive mechanisms to ensure the spinal stability are significant issues in spinal biomechanics. A computational model of spine under the control of 48 anatomically oriented muscle actions was used to simulate iso-resistive trunk movements. Neural excitation of muscles was attained based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. In this study, the trunk extension movement at various resistance levels while extending from 60 degrees flexion to the upright posture was investigated. Incorporation of the stability condition as an additional constraint in the optimization algorithm increased antagonistic activities for all resistance levels demonstrating that the co-activation caused an increase in the intrinsic stiffness of the spine and its stability in a feed-forward manner. During the acceleration phase of the movement, extensors activity increased while flexors activity decreased in response to the higher resistance. The co-activation ratio noticed in the braking phase of the movement increased with higher resistance. In presence of a 30 Nm flexion perturbation moment, reflexive feed-back noticeably decreased the induced deviation of the velocity and position profiles from the desired ones at all resistance levels. The stability-generated co-activation decreased the reflexive response of muscle spindles to the perturbation demonstrating that both intrinsic and reflexive mechanisms contribute to the trunk stability. The rise in muscle co-activation can ameliorate the corruption of afferent neural sensory system at the expense of higher loading of the spine. PMID:18057565

  3. A Comparison of Total and Intrinsic Muscle Stiffness Among Flexors and Extensors of the Ankle, Knee and Elbow

    NASA Technical Reports Server (NTRS)

    Lemoine, Sandra M.

    1997-01-01

    This study examined 3 methods that assessed muscle stiffness. Muscle stiffness has been quantified by tissue reactive force (transverse stiffness), vibration, and force (or torque) over displacement. Muscle stiffness also has two components: reflex (due to muscle sensor activity) and intrinsic (tonic firing of motor units, elastic nature of actin and myosin cross bridges, and connective tissue). This study compared three methods of measuring muscle stiffness of agonist-antagonist muscle pairs of the ankle, knee and elbow.

  4. Propranolol, but not naloxone, enhances spinal reflex bladder activity and reduces pudendal inhibition in cats.

    PubMed

    Rogers, Marc J; Xiao, Zhiying; Shen, Bing; Wang, Jicheng; Schwen, Zeyad; Roppolo, James R; de Groat, William C; Tai, Changfeng

    2015-01-01

    This study examined the role of β-adrenergic and opioid receptors in spinal reflex bladder activity and in the inhibition induced by pudendal nerve stimulation (PNS) or tibial nerve stimulation (TNS). Spinal reflex bladder contractions were induced by intravesical infusion of 0.25% acetic acid in α-chloralose-anesthetized cats after an acute spinal cord transection (SCT) at the thoracic T9/T10 level. PNS or TNS at 5 Hz was applied to inhibit these spinal reflex contractions at 2 and 4 times the threshold intensity (T) for inducing anal or toe twitch, respectively. During a cystrometrogram (CMG), PNS at 2T and 4T significantly (P < 0.05) increased bladder capacity from 58.0 ± 4.7% to 85.8 ± 10.3% and 96.5 ± 10.7%, respectively, of saline control capacity, while TNS failed to inhibit spinal reflex bladder contractions. After administering propranolol (3 mg/kg iv, a β₁/β₂-adrenergic receptor antagonist), the effects of 2T and 4T PNS on bladder capacity were significantly (P < 0.05) reduced to 64.5 ± 9.5% and 64.7 ± 7.3%, respectively, of the saline control capacity. However, the residual PNS inhibition (about 10% increase in capacity) was still statistically significant (P < 0.05). Propranolol treatment also significantly (P = 0.0019) increased the amplitude of bladder contractions but did not change the control bladder capacity. Naloxone (1 mg/kg iv, an opioid receptor antagonist) had no effect on either spinal reflex bladder contractions or PNS inhibition. At the end of experiments, hexamethonium (10 mg/kg iv, a ganglionic blocker) significantly (P < 0.05) reduced the amplitude of the reflex bladder contractions. This study indicates an important role of β₁/β₂-adrenergic receptors in pudendal inhibition and spinal reflex bladder activity. PMID:25394827

  5. Stretch reflex improves rolling stability during hopping of a decerebrate biped system.

    PubMed

    Rosendo, Andre; Liu, Xiangxiao; Shimizu, Masahiro; Hosoda, Koh

    2015-01-01

    When humans hop, attitude recovery can be observed in both the sagittal and frontal planes. While it is agreed that the brain plays an important role in leg placement, the role of low-level feedback (the stretch reflex) on frontal plane stabilization remains unclear. Seeking to better understand the contribution of the soleus stretch reflex to rolling stability, we performed experiments on a biomimetic humanoid hopping robot. Various reflex responses to touching the floor, ranging from no response to long muscle activations, were examined, and the effect of a delay upon touching the floor was also examined. We found that the stretch reflex brought the system closer to stable, straight hopping. The presence of a delay did not affect the results; both the cases with and without a delay outperformed the case without a reflex response. The results of this study highlight the importance of low-level control in locomotion for which body stabilization does not require higher-level signals. PMID:25599138

  6. Acute Whole-Body Vibration does not Facilitate Peak Torque and Stretch Reflex in Healthy Adults

    PubMed Central

    Yeung, Ella W.; Lau, Cheuk C.; Kwong, Ada P.K.; Sze, Yan M.; Zhang, Wei Y.; Yeung, Simon S.

    2014-01-01

    The acute effect of whole-body vibration (WBV) training may enhance muscular performance via neural potentiation of the stretch reflex. The purpose of this study was to investigate if acute WBV exposure affects the stretch induced knee jerk reflex [onset latency and electromechanical delay (EMD)] and the isokinetic knee extensor peak torque performance. Twenty-two subjects were randomly assigned to the intervention or control group. The intervention group received WBV in a semi-squat position at 30° knee flexion with an amplitude of 0.69 mm, frequency of 45 Hz, and peak acceleration of 27.6 m/s2 for 3 minutes. The control group underwent the same semii-squatting position statically without exposure of WBV. Two-way mixed repeated measures analysis of variance revealed no significant group effects differences on reflex latency of rectus femoris (RF) and vastus lateralis (VL; p = 0.934 and 0.935, respectively) EMD of RF and VL (p = 0.474 and 0.551, respectively) and peak torque production (p = 0.483) measured before and after the WBV. The results of this study indicate that a single session of WBV exposure has no potentiation effect on the stretch induced reflex and peak torque performance in healthy young adults. Key Points There is no acute potentiation of stretch reflex right after whole body vibration. Acute whole body vibration does not improve mus-cle peak torque performance in healthy young adults. PMID:24570602

  7. Aging attenuates the vestibulosympathetic reflex in humans

    NASA Technical Reports Server (NTRS)

    Ray, Chester A.; Monahan, Kevin D.

    2002-01-01

    BACKGROUND: The vestibular system contributes to sympathetic activation by engagement of the otolith organs. However, there is a significant loss of vestibular function with aging. Therefore, the purpose of the present study was to determine if young and older individuals differ in their cardiovascular and sympathetic responses to otolithic stimulation (ie, head-down rotation, HDR). We hypothesized that responses to otolithic stimulation would be attenuated in older adults because of morphological and physiological alterations that occur in the vestibular system with aging. METHODS AND RESULTS: Arterial blood pressure, heart rate, muscle sympathetic nerve activity (MSNA), and head rotation were measured during HDR in 11 young (26 +/- 1 years) and 11 older (64 +/- 1 years) subjects in the prone posture. Five older subjects performed head rotation (chin to chest) in the lateral decubitus position, which simulates HDR but does not alter afferent inputs from the vestibular system. MSNA responses to HDR were significantly attenuated in older as compared with young subjects (P<0.01). MSNA increased in the older subjects by only 12 +/- 5% as compared with 85 +/- 16% in the young. Furthermore, HDR elicited significant reductions in mean arterial blood pressure in older (Delta-6 +/- 1 mm Hg; P<0.01) but not young subjects (Delta1 +/- 1 mm Hg). In contrast to HDR, head rotation performed in the lateral decubitus position did not elicit hypotension. MSNA responses to baroreceptor unloading and the cold pressor test were not different between the age groups. CONCLUSIONS: These data indicate that aging attenuates the vestibulosympathetic reflex in humans and may contribute to the increased prevalence of orthostatic hypotension with age.

  8. H-reflex latency in uremic neuropathy: correlation with NCV and clinical findings.

    PubMed

    Halar, E M; Brozovich, F V; Milutinovic, J; Inouye, V L; Becker, V M

    1979-04-01

    Sixty-two uremic patients on dialysis of varying durations were tested bilaterally for posterior tibial nerve H-reflex latency, at 3-month intervals. Bilateral nerve conduction velocities (NCVs) of the peroneal, tibial, and sural nerves were concomitantly determined in all subjects. Proprioception sense, vibration perception threshold at the great toes, and deep tendon reflexes at the knee and ankle were determined in all subjects on the day of electrodiagnostic testing. The sensitivity of the H-reflex latency in detection of the onset and severity of uremic neuropathy was assessed. H-reflex latency changes were compared to NCV and clinical test results. The following was found: (1) of the parameters studied, the H-reflex latency appeared to be the most sensitive indicator of early uremic polyneuropathies, (2) electrodiagnostic tests were more sensitive to the onset of neuropathies than the clinical testing parameters studied, and (3) the sural sensory nerve appeared to be involved earlier than peroneal and tibial motor nerves in neuropathies studied. PMID:224838

  9. CARA Risk Assessment Thresholds

    NASA Technical Reports Server (NTRS)

    Hejduk, M. D.

    2016-01-01

    Warning remediation threshold (Red threshold): Pc level at which warnings are issued, and active remediation considered and usually executed. Analysis threshold (Green to Yellow threshold): Pc level at which analysis of event is indicated, including seeking additional information if warranted. Post-remediation threshold: Pc level to which remediation maneuvers are sized in order to achieve event remediation and obviate any need for immediate follow-up maneuvers. Maneuver screening threshold: Pc compliance level for routine maneuver screenings (more demanding than regular Red threshold due to additional maneuver uncertainty).

  10. Achilles tendon reflex measuring system

    NASA Astrophysics Data System (ADS)

    Szebeszczyk, Janina; Straszecka, Joanna

    1995-06-01

    The examination of Achilles tendon reflex is widely used as a simple, noninvasive clinical test in diagnosis and pharmacological therapy monitoring in such diseases as: hypothyroidism, hyperthyroidism, diabetic neuropathy, the lower limbs obstructive angiopathies and intermittent claudication. Presented Achilles tendon reflect measuring system is based on the piezoresistive sensor connected with the cylinder-piston system. To determinate the moment of Achilles tendon stimulation a detecting circuit was used. The outputs of the measuring system are connected to the PC-based data acquisition board. Experimental results showed that the measurement accuracy and repeatability is good enough for diagnostics and therapy monitoring purposes. A user friendly, easy-to-operate measurement system fulfills all the requirements related to recording, presentation and storing of the patients' reflexograms.