Magro, Cátia; Nora, David; Marques, Miguel; Alves, Angela Garcia
Thoracoabdominal aortic disease (aneurysm or dissection) has increased in recent decades. Surgery is the curative treatment but is associated to high perioperative morbidity and mortality risks. Paraplegia is one of the most severe complications, whose incidence has decreased significantly with the implementation of spinal cord protection strategies. No single method or combination of methods has proven to be fully effective in preventing paraplegia. This review is intended to analyse the scientific evidence available on the role of intraoperative monitoring with motor evoked potentials in the neurological outcome of patients undergoing thoracoabdominal aortic surgery. An online search (PubMed) was conducted. Relevant references were selected and reviewed. Intraoperative monitoring with motor evoked potentials (MEP) allows early detection of ischemic events and a targeted intervention to prevent the development of spinal cord injury, significantly reducing the incidence of postoperative paraplegia. MEP monitoring may undergo several intraoperative interferences which may compromise their interpretation. Neuromuscular blockade is the main limiting factor of anesthetic origin. It is essential to strike a balance between monitoring conditions and surgical and anesthetic needs as well as to evaluate the risks and benefits of the technique for each patient. MEP monitoring improves neurological outcome when integrated in a multidisciplinary strategy which must include multiple protective mechanisms that should be tailored to each hospital reality.
van der Linden, C; Bruggeman, R; Goldman, W H
To evaluate the effect of stereotactic thalamotomy on the function of the corticospinal tract, we studied motor evoked potentials (MEPs) recorded by surface electromyography (EMG) in the left extensor carpi radialis (ECR) and flexor carpi radialis (FCR) with magnetic stimulation of the contralateral motor cortex in a 43-year-old patient with a severe postural and resting tremor of the left hand. The patient was diagnosed eight years previously with left hemiparkinsonism. The tremor was unresponsive to various medications. After thalamotomy the tremor had disappeared, confirmed by EMG studies. MEP latencies at rest were normal and did not change after thalamotomy. Volitional contraction of either ECR or FCR shortened the latency of the corresponding MEP before and after thalamotomy. However, before thalamotomy responses at rest were less well synchronized and followed by EMG silence with subsequent long duration tonic after discharges. Furthermore, during voluntary contraction the responses only slightly enhanced. After surgery MEPs at rest in both muscles were more synchronized and after-discharges had disappeared. Moreover, with volitional contraction of either ECR of FCR, the MEPs enhanced more dramatically. The silent periods (SPs) following the MEP during sustained voluntary contraction were longer after thalamotomy. The consistent MEP latencies suggest that the conduction of the pyramidal tract is unaffected by thalamotomy. The better synchronized responses, the alleviation of after-discharges and the longer SPs in this patient with hemiparkinsonism following thalamotomy suggest an improved sensorimotor integration, which may be the result of a reduced thalamic input onto suprasegmental levels.
Kaelin-Lang, Alain; Conforto, Adriana B; Z'Graggen, Werner; Hess, Christian W
Motor unit action potentials (MUAPs) evoked by repetitive, low-intensity transcranial magnetic stimulation can be modeled as a Poisson process. A mathematical consequence of such a model is that the ratio of the variance to the mean of the amplitudes of motor evoked potentials (MEPs) should provide an estimate of the mean size of the individual MUAPs that summate to generate each MEP. We found that this is, in fact, the case. Our finding thus supports the use of the Poisson distribution to model MEP generation and indicates that this model enables characterization of the motor unit population that contributes to near-threshold MEPs.
Ma, Ying; Thakor, Nitish V; Jia, Xiaofeng
Motor evoked potentials (MEPs) convey information regarding the functional integrity of the descending motor pathways. Absence of the MEP has been used as a neurophysiological marker to suggest cortico-spinal abnormalities in the operating room. Due to their high variability and sensitivity, detailed quantitative studies of MEPs are lacking. This paper applies a statistical method to characterize MEPs by estimating the number of motor units and single motor unit potential amplitudes. A clearly increasing trend of single motor unit potential amplitudes in the MEPs after each pulse of the stimulation pulse train is revealed by this method. This statistical method eliminates the effects of anesthesia, and provides an objective assessment of MEPs. Consequently this statistical method has high potential to be useful in future quantitative MEPs analysis.
Coselli, Joseph S; Tsai, Peter I
Thoracoabdominal aortic aneurysms (TAAAs) have a dismal natural history that frequently necessitates surgical repair, but such repairs sometimes result in paraplegia and paraparesis. To reduce the risk of these complications, intraoperative monitoring of spinal cord motor evoked potentials (MEPs) can be used to guide TAAA repair procedures and may potentially minimize spinal cord ischemia. However, the use of MEP monitoring techniques requires important changes to anesthetic management, entails certain risks, and has important contraindications.
Koht, Antoun; Sloan, Tod B
Advances in electrophysiological monitoring have improved the ability of surgeons to make decisions and minimize the risks of complications during surgery and interventional procedures when the central nervous system (CNS) is at risk. Individual techniques have become important for identifying or mapping the location and pathway of critical neural structures. These techniques are also used to monitor the progress of procedures to augment surgical and physiologic management so as to reduce the risk of CNS injury. Advances in motor evoked potentials have facilitated mapping and monitoring of the motor tracts in newer, more complex procedures.
Inoue, Ken; Mimori, Yasuyo; Nakamura, Shigenobu
When stimulating the mixed nerve to record evoked potential, both sensory and motor fibers are activated before entering the spinal cord. The N10 potential has been described as an antidromic motor evoked potential based on results obtained by recording at the anterior midneck. In the present study, we examined the changes in latencies of Erb's potential, N10, and N13 by stimulating the median nerve distally at the wrist and proximally at the elbow. The conduction velocity of N10 calculated by the difference between N10 latencies at the two stimulation points was consistent with motor conduction velocity, although N13 conduction velocity estimated by the same method reflected a sensory conduction velocity. A positive relation was also observed between the indirect latency from the stimulation point to the anterior root as calculated using the equation (F - M - 1) / 2 (ms) and the direct latency to the negative peak of the N10 potential. Our data support the notion that N10 represents antidromic motor potential originating in the spinal entry zone of the anterior root.
Muellbacher, W.; Artner, C.; Mamoli, B.
OBJECTIVES—The occurrence of a lingual paralysis after unilateral upper motor neuron lesions is an infrequent clinical phenomenon, and the underlying pathophysiological mechanisms are poorly understood. We studied the cortical motor representations of ipsilateral and contralateral lingual muscles in healthy controls and in a selected group of stroke patients, to clarify the variable occurrence of a lingual paralysis after recent monohemispheric ischaemia. METHODS—A special bipolar surface electrode was used to record the ipsilateral and contralateral compound muscle action potentials (CMAPs) from the lingual muscles after transcranial magnetic stimulation (TMS) of the human motor cortex and peripheral electrical stimulation (PES) of the hypoglossal nerve medial to the angle of the jaw. Four patients with a lingual paralysis (group 1) and four patients with symmetric lingual movements (group 2) after monohemispheric first ever stroke were studied and compared with 40 healthy controls. RESULTS—In controls, TMS of either hemisphere invariably produces CAMPs in the ipsilateral and contralateral lingual muscles, elicited through crossed and uncrossed central motor pathways, respectively. In the 40 healthy controls, TMS of either hemisphere elicited CMAPs of significantly greater amplitudes and shorter onset latencies from the contralateral muscles compared with the ipsilateral responses (p<0.0001). In the patient groups, TMS of the affected hemisphere failed to evoke any CMAP from either lingual side; TMS of the unsevered hemisphere always produced normal ipsilateral and contralateral responses, irrespective of whether the ipsilateral muscles were paralysed or not. CONCLUSIONS—Bilateral crossed and uncrossed corticonuclear projections are invariably existent in humans. After unilateral interruption of these pathways, some people do exhibit a lingual paralysis whereas others do not. The development of a central lingual paralysis is most likely dependent on
Turkof, Edvin; Jurasch, Nikita; Knolle, Erik; Schwendenwein, Ilse; Habib, Danja; Unger, Ewald; Reichel, Martin; Losert, Udo
Differentiation between motor and sensory fascicles is frequently necessary in reconstructive peripheral nerve surgery. The goal of this experimental study was to verify if centrally motor evoked potentials (MEP) could be implemented to differentiate sensory from motor fascicles, despite the well-known intermingling between nerve fascicles along their course to their distant periphery. This new procedure would enable surgeons to use MEP for placing nerve grafts at corresponding fascicles in the proximal and distal stumps without the need to use time-consuming staining. In ten sheep, both ulnar nerves were exposed at the terminal bifurcation between the last sensory and motor branch. Animals were then relaxed to avoid volume conduction. On central stimulation, the evoked nerve compound action potentials were simultaneously recorded from both terminal branches. In all cases, neurogenic motor nerve action potentials were recorded only from the terminal motor branch. The conclusion was that MEPs can be used for intraoperative differentiation between sensory and motor nerves. Further studies are necessary to develop this method for in situ measurements on intact nerve trunks.
Grosprêtre, Sidney; Martin, Alain
The aim of this study was to examine the collision responsible for the volitional V-wave evoked by supramaximal electrical stimulation of the motor nerve during voluntary contraction. V-wave was conditioned by transcranial magnetic stimulation (TMS) over the motor cortex at several inter-stimuli intervals (ISI) during weak voluntary plantar flexions (n = 10) and at rest for flexor carpi radialis muscle (FCR; n = 6). Conditioning stimulations were induced by TMS with intensity eliciting maximal motor-evoked potential (MEPmax). ISIs used were ranging from -20 to +20 msec depending on muscles tested. The results showed that, for triceps surae muscles, conditioning TMS increased the V-wave amplitude (~ +250%) and the associated mechanical response (~ +30%) during weak voluntary plantar flexion (10% of the maximal voluntary contraction -MVC) for ISIs ranging from +6 to +18 msec. Similar effect was observed at rest for the FCR with ISI ranging from +6 to +12 msec. When the level of force was increased from 10 to 50% MVC or the conditioning TMS intensity was reduced to elicit responses of 50% of MEPmax, a significant decrease in the conditioned V-wave amplitude was observed for the triceps surae muscles, linearly correlated to the changes in MEP amplitude. The slope of this correlation, as well as the electro-mechanical efficiency, was closed to the identity line, indicating that V-wave impact at muscle level seems to be similar to the impact of cortical stimulation. All these results suggest that change in V-wave amplitude is a great index to reflect changes in cortical neural drive addressed to spinal motoneurons.
Kallioniemi, Elisa; Pitkänen, Minna; Säisänen, Laura; Julkunen, Petro
Cortical motor mapping in pre-surgical applications can be performed using motor evoked potential (MEP) amplitudes evoked with neuronavigated transcranial magnetic stimulation. The MEP latency, which is a more stable parameter than the MEP amplitude, has not so far been utilized in motor mapping. The latency, however, may provide information about the stress in damaged motor pathways, e.g. compression by tumors, which cannot be observed from the MEP amplitudes. Thus, inclusion of this parameter could add valuable information to the presently used technique of MEP amplitude mapping. In this study, the functional cortical representations of first dorsal interosseous (FDI), abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles were mapped in both hemispheres of ten healthy righthanded volunteers. The cortical muscle representations were evaluated by the area and centre of gravity (CoG) by using MEP amplitudes and latencies. As expected, the latency and amplitude CoGs were congruent and were located in the centre of the maps but in a few subjects, instead of a single centre, several loci with short latencies were observed. In conclusion, MEP latencies may be useful in distinguishing the cortical representation areas with the most direct pathways from those pathways with prolonged latencies. However, the potential of latency mapping to identify stressed motor tract connections at the subcortical level will need to be verified in future studies with patients.
Confais, Joachim; Ponce-Alvarez, Adrián; Diesmann, Markus; Riehle, Alexa
Evoked potentials (EPs) are observed in motor cortical local field potentials (LFPs) during movement execution (movement-related potentials [MRPs]) and in response to relevant visual cues (visual evoked potentials [VEPs]). Motor cortical EPs may be directionally selective, but little is known concerning their relation to other aspects of motor behavior, such as task timing and performance. We recorded LFPs in motor cortex of two monkeys during performance of a precued arm-reaching task. A time cue at the start of each trial signaled delay duration and thereby the pace of the task and the available time for movement preparation. VEPs and MRPs were strongly modulated by the delay duration, VEPs being systematically larger in short-delay trials and MRPs larger in long-delay trials. Despite these systematic modulations related to the task timing, directional selectivity was similar in short and long trials. The behavioral reaction time was positively correlated with MRP size and negatively correlated with VEP size, within sessions. In addition, the behavioral performance improved across sessions, in parallel with a slow decrease in the size of VEPs and MRPs. Our results clearly show the strong influence of the behavioral context and performance on motor cortical population activity during movement preparation and execution. PMID:20884766
Benavides, Francisco D; Santamaria, Andrea J; Bodoukhin, Nikita; Guada, Luis G; Solano, Juan P; Guest, James D
Yucatan micropigs have brain and spinal cord dimensions similar to humans and are useful for certain spinal cord injury (SCI) translational studies. Micropigs are readily trained in behavioral tasks, allowing consistent testing of locomotor loss and recovery. However, there has been little description of their motor and sensory pathway neurophysiology. We established methods to assess motor and sensory cortical evoked potentials in the anesthetized, uninjured state. We also evaluated epidurally evoked motor and sensory stimuli from the T6 and T9 levels, spanning the intended contusion injury epicenter. Response detection frequency, mean latency and amplitude values, and variability of evoked potentials were determined. Somatosensory evoked potentials were reliable and best detected during stimulation of peripheral nerve and epidural stimulation by referencing the lateral cortex to midline Fz. The most reliable hindlimb motor evoked potential (MEP) occurred in tibialis anterior. We found MEPs in forelimb muscles in response to thoracic epidural stimulation likely generated from propriospinal pathways. Cranially stimulated MEPs were easier to evoke in the upper limbs than in the hindlimbs. Autopsy studies revealed substantial variations in cortical morphology between animals. This electrophysiological study establishes that neurophysiological measures can be reliably obtained in micropigs in a time frame compatible with other experimental procedures, such as SCI and transplantation. It underscores the need to better understand the motor control pathways, including the corticospinal tract, to determine which therapeutics are suitable for testing in the pig model.
Carson, Richard G; Ruddy, Kathy L; McNickle, Emmet
Thirty years ago, the first magnetic device capable of stimulating the human brain without discomfort through the intact skull was unveiled in Sheffield, England (Barker et al. in Lancet 1:1106-1107, 1985). Since that time, transcranial magnetic stimulation (TMS) has become the tool of choice for many scientists investigating human motor control and learning. In light of the fact that there are limits to the information that can be provided by any experimental technique, we first make the case that the necessarily restricted explanatory scope of the TMS technique-and the motor-evoked potentials to which it gives rise, is not yet reflected adequately in the research literature. We also argue that this inattention, coupled with the pervasive adoption of TMS as an investigative tool, may be restricting the elaboration of knowledge concerning the neural processes that mediate human motor learning. In order to make these points, we use as an exemplar the study of cross-education-the interlimb transfer of functional capacity.
Objective To investigate the clinical significance of quantitative parameters in transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEP) which can be adopted to predict functional recovery of the upper limb in stroke patients in the early subacute phase. Methods One hundred thirteen patients (61 men, 52 women; mean age 57.8±12.2 years) who suffered faiarst-ever stroke were included in this study. All participants underwent TMS-induced MEP session to assess the corticospinal excitability of both hand motor cortices within 3 weeks after stroke onset. After the resting motor threshold (rMT) was assessed, five sweeps of MEP were performed, and the mean amplitude of the MEP was measured. Latency of MEP, volume of the MEP output curve, recruitment ratios, and intracortical inhibition and facilitation were also measured. Motor function was assessed using the Fugl-Meyer Assessment scale (FMA) within 3 weeks and at 3 months after stroke onset. Correlation analysis was performed between TMS-induced MEP derived measures and FMA scores. Results In the MEP response group, rMT and rMT ratio measures within 3 weeks after stroke onset showed a significant negative correlation with the total and upper limb FMA scores at 3 months after stroke (p<0.001). Multiple regression analysis revealed that FMA score and rMT ratio, but not rMT within 3 weeks were independent prognostic factors for FMA scores at 3 months after stroke. Conclusion These results indicated that the quantitative parameter of TMS-induced MEP, especially rMT ratio in the early subacute phase, could be used as a parameter to predict motor function in patients with stroke. PMID:27847710
Hirano, Masato; Kubota, Shinji; Koizume, Yoshiki; Tanaka, Shinya; Funase, Kozo
Motor training induces plastic changes in the primary motor cortex (M1). However, it is unclear whether and how the latency of motor-evoked potentials (MEP) and MEP amplitude are affected by implicit and/or explicit motor learning. Here, we investigated the changes in M1 excitability and MEP latency induced by implicit and explicit motor learning. The subjects performed a serial reaction time task (SRTT) with their five fingers. In this task, visual cues were lit up sequentially along with a predetermined order. Through training, the subjects learned the order of sequence implicitly and explicitly. Before and after the SRTT, we recorded MEP at 25 stimulation points around the hot spot for the flexor pollicis brevis (FPB) muscle. Although no changes in MEP amplitude were observed in either session, we found increases in MEP latency and changes in histogram of MEP latency after implicit learning. Our results suggest that reorganization across the motor cortices occurs during the acquisition of implicit knowledge. In contrast, acquisition of explicit knowledge does not appear to induce the reorganization based on the measures we recorded. The fact that the above mentioned increases in MEP latency occurred without any alterations in MEP amplitude suggests that learning has different effects on different physiological signals. In conclusion, our results propose that analyzing a combination of some indices of M1 excitability, such as MEP amplitude and MEP latency, is encouraged in order to understand plasticity across motor cortices. PMID:28101014
Hirano, Masato; Kubota, Shinji; Koizume, Yoshiki; Tanaka, Shinya; Funase, Kozo
Motor training induces plastic changes in the primary motor cortex (M1). However, it is unclear whether and how the latency of motor-evoked potentials (MEP) and MEP amplitude are affected by implicit and/or explicit motor learning. Here, we investigated the changes in M1 excitability and MEP latency induced by implicit and explicit motor learning. The subjects performed a serial reaction time task (SRTT) with their five fingers. In this task, visual cues were lit up sequentially along with a predetermined order. Through training, the subjects learned the order of sequence implicitly and explicitly. Before and after the SRTT, we recorded MEP at 25 stimulation points around the hot spot for the flexor pollicis brevis (FPB) muscle. Although no changes in MEP amplitude were observed in either session, we found increases in MEP latency and changes in histogram of MEP latency after implicit learning. Our results suggest that reorganization across the motor cortices occurs during the acquisition of implicit knowledge. In contrast, acquisition of explicit knowledge does not appear to induce the reorganization based on the measures we recorded. The fact that the above mentioned increases in MEP latency occurred without any alterations in MEP amplitude suggests that learning has different effects on different physiological signals. In conclusion, our results propose that analyzing a combination of some indices of M1 excitability, such as MEP amplitude and MEP latency, is encouraged in order to understand plasticity across motor cortices.
Säisänen, Laura; Julkunen, Petro; Niskanen, Eini; Danner, Nils; Hukkanen, Taina; Lohioja, Tarja; Nurkkala, Jouko; Mervaala, Esa; Karhu, Jari; Könönen, Mervi
Navigated transcranial magnetic stimulation (TMS) is a tool for targeted, noninvasive stimulation of cerebral cortex. Transcranial stimuli can depolarize neurons and evoke measurable effects which are unique in two ways: the effects are caused directly and without a consciousness of the subject, and, the responses from peripheral muscles provide a direct measure for the integrity of the whole motor pathway. The clinical relevance of the method has not always been fully exposed because localizing the optimal stimulation site and determining the optimal stimulation strength have been dependent on time-consuming experimentation and skill. Moreover, in many disorders it has been uncertain, whether the lack of motor responses is the result of true pathophysiological changes or merely because of unoptimal stimulation. We characterized the muscle responses from human primary motor cortex system by navigated TMS to provide normative values for the clinically relevant TMS parameters on 65 healthy volunteers aged 22 to 81 years. We delivered focal TMS pulses on the primary motor area (M1) and recorded muscle responses on thenar and anterior tibial muscles. Motor threshold, latencies and amplitudes of motor-evoked potentials, and silent period duration were measured. The correction of the motor-evoked potential latency for subjects' height is provided. In conclusion, we provide a modified baseline of TMS-related parameters for healthy subjects. Earlier such large-scale baseline material has not been available.
Mihalj, Mario; Lušić, Linda; Đogaš, Zoran
It is unknown to what extent chronic intermittent hypoxaemia in obstructive sleep apnea causes damage to the motor and sensory peripheral nerves. It was hypothesized that patients with obstructive sleep apnea would have bilaterally significantly impaired amplitudes of both motor and sensory peripheral nerve-evoked potentials of both lower and upper limbs. An observational study was conducted on 43 patients with obstructive sleep apnea confirmed by the whole-night polysomnography, and 40 controls to assess the relationship between obstructive sleep apnea and peripheral neuropathy. All obstructive sleep apnea subjects underwent standardized electroneurographic testing, with full assessment of amplitudes of evoked compound muscle action potentials, sensory neural action potentials, motor and sensory nerve conduction velocities, and distal motor and sensory latencies of the median, ulnar, peroneal and sural nerves, bilaterally. All nerve measurements were compared with reference values, as well as between the untreated patients with obstructive sleep apnea and control subjects. Averaged compound muscle action potential and sensory nerve action potential amplitudes were significantly reduced in the nerves of both upper and lower limbs in patients with obstructive sleep apnea compared with controls (P < 0.001). These results confirmed that patients with obstructive sleep apnea had significantly lower amplitudes of evoked action potentials of both motor and sensory peripheral nerves. Clinical/subclinical axonal damage exists in patients with obstructive sleep apnea to a greater extent than previously thought.
Biscevic, Mirza; Biscevic, Sejla; Ljuca, Farid; Smrke, Barbara UR; Ozturk, Cagatay; Tiric-Campara, Merita
ABSTRACT Introduction: Correction of pediatric spine deformities is challenging surgical procedures. This fragile group of patients has many risk factors, therefore prevention of most fearing complication-paraplegia is extremely important. Monitoring of transmission of neurophysiological impulses through motor and sensor pathways of spinal cord gives us an insight into cord's function, and predicts postoperative neurological status. Goal: Aim of this work is to present our experiences in monitoring of spinal cord motor function - MEP during surgical corrections of the hardest pediatric spine deformities, pointing on the most dangerous aspects. Material and methods: We analyzed incidence of MEP changes and postoperative neurological status in patients who had major spine correcting surgery in period April ‘11- April ‘14 on our Spine department. Results: Two of 43 patients or 4.6% in our group experienced significant MEP changes during their major spine reconstructive surgeries. We promptly reduced distractive forces, and MEP normalized, and there were no neurological deficit. Neuromonitoring is reliable method which allows us to “catch” early signs of neurological deficits, when they are still in reversible phase. Although IONM cannot provide complete protection of neurological deficit (it reduces risk of paraplegia about 75%), it at least afford a comfort to the surgeon being fear free that his patient is neurologically intact during long lasting procedures. PMID:25568569
Objective To evaluate whether the combination of muscle motor evoked potentials (mMEPs) and somatosensory evoked potentials (SEPs) measured during spinal surgery can predict immediate and permanent postoperative motor deficits. Methods mMEP and SEP was monitored in patients undergoing spinal surgery between November 2012 and July 2014. mMEPs were elicited by a train of transcranial electrical stimulation over the motor cortex and recorded from the upper/lower limbs. SEPs were recorded by stimulating the tibial and median nerves. Results Combined mMEP/SEP recording was successfully achieved in 190 operations. In 117 of these, mMEPs and SEPs were stable and 73 showed significant changes. In 20 cases, motor deficits in the first 48 postoperative hours were observed and 6 patients manifested permanent neurological deficits. The two potentials were monitored in a number of spinal surgeries. For surgery on spinal deformities, the sensitivity and specificity of combined mMEP/SEP monitoring were 100% and 92.4%, respectively. In the case of spinal cord tumor surgeries, sensitivity was only 50% but SEP changes were observed preceding permanent motor deficits in some cases. Conclusion Intraoperative monitoring is a useful tool in spinal surgery. For spinal deformity surgery, combined mMEP/SEP monitoring showed high sensitivity and specificity; in spinal tumor surgery, only SEP changes predicted permanent motor deficits. Therefore, mMEP, SEP, and joint monitoring may all be appropriate and beneficial for the intraoperative monitoring of spinal surgery. PMID:27446784
TSUTSUI, Shunji; YAMADA, Hiroshi
Transcranial motor evoked potentials (TcMEPs), which are muscle action potentials elicited by transcranial brain stimulation, have been the most popular method for the last decade to monitor the functional integrity of the motor system during surgery. It was originally difficult to record reliable and reproducible potentials under general anesthesia, especially when inhalation-based anesthetic agents that suppressed the firing of anterior horn neurons were used. Advances in anesthesia, including the introduction of intravenous anesthetic agents, and progress in stimulation techniques, including the use of pulse trains, improved the reliability and reproducibility of TcMEP responses. However, TcMEPs are much smaller in amplitude compared with compound muscle action potentials evoked by maximal peripheral nerve stimulation, and vary from one trial to another in clinical practice, suggesting that only a limited number of spinal motor neurons innervating the target muscle are excited in anesthetized patients. Therefore, reliable interpretation of the critical changes in TcMEPs remains difficult and controversial. Additionally, false negative cases have been occasionally encountered. Recently, several facilitative techniques using central or peripheral stimuli, preceding transcranial electrical stimulation, have been employed to achieve sufficient depolarization of motor neurons and augment TcMEP responses. These techniques might have potentials to improve the reliability of intraoperative motor pathway monitoring using TcMEPs. PMID:26935781
Li, Fenghua; Deshaies, Eric M; Allott, Geoffrey; Canute, Gregory; Gorji, Reza
Motor evoked potentials (MEPs) elicited by both direct cortical stimulation (DCS) and transcranial electrical stimulation are used during brain tumor resection. Parallel use of direct cortical stimulation motor evoked potentials (DCS-MEPs) and transcranial electrical stimulation motor evoked potentials (TCeMEPs) has been practiced during brain tumor resection. We report that DCS-MEPs elicited by direct subdural grid stimulation, but not TCeMEPs, detected brain ischemia during brain tumor resection. Following resection of a brainstem high-grade glioma in a 21-year-old, the threshold of cortical motor-evoked-potentials (cMEPs) increased from 13 mA to 20 mA while amplitudes decreased. No changes were noted in transcranial motor evoked potentials (TCMEPs), somatosensory evoked potentials (SSEPs), auditory evoked potentials (AEPs), anesthetics, or hemodynamic parameters. Our case showed the loss of cMEPs and SSEPs, but not TCeMEPs. Permanent loss of DCS-MEPs and SSEPs was correlated with permanent left hemiplegia in our patient even when appropriate action was taken. Parallel use of DCS- and TCeMEPs with SSEPs improves sensitivity of intraoperative detection of motor impairment. DCS may be superior to TCeMEPs during brain tumor resection.
Cantello, R; Gianelli, M; Bettucci, D; Civardi, C; De Angelis, M S; Mutani, R
We studied the EMG potentials evoked in the bilateral first dorsal interosseus muscle by electromagnetic stimulation of the corticomotoneuronal descending system in 10 Parkinson's disease patients and in 10 age- and sex-matched normal controls. We selected patients who did not have tremor but had predominant rigidity with asymmetric body involvement. On the rigid side of the PD patients, the threshold to cortical stimulation was lower than on the contralateral side or than normal values. On average, patients had normal central conduction times, but their motor evoked potentials (MEPs) on the rigid side were larger than those of controls when the cortical stimulus was at rest or during slight tonic contraction of the target muscle. In the latter condition, a silent period shorter than that of controls followed MEPs, whereas the peripheral silent period following ulnar nerve stimulation at the wrist was prolonged. Alpha motor neuron excitability, tested by the F-wave method, was enhanced on the rigid side at rest. In rigidity, spinal motor nuclei may be more responsive than normal to descending inputs from motor cortex, or the entire corticomotoneuron system may prove hyperexcitable under given conditions.
Shalash, Ali Soliman; Hassan, Dalia Mohamed; Elrassas, Hanan Hani; Salama, Mohamed Mosaad; Méndez-Hernández, Edna; Salas-Pacheco, José M.; Arias-Carrión, Oscar
Degeneration of several brainstem nuclei has been long related to motor and non-motor symptoms (NMSs) of Parkinson’s disease (PD). Nevertheless, due to technical issues, there are only a few studies that correlate that association. Brainstem auditory-evoked potential (BAEP) and vestibular-evoked myogenic potential (VEMP) responses represent a valuable tool for brainstem assessment. Here, we investigated the abnormalities of BAEPs, ocular VEMPs (oVEMPs), and cervical VEMPs (cVEMPs) in patients with PD and its correlation to the motor and NMSs. Fifteen patients diagnosed as idiopathic PD were evaluated by Unified Parkinson’s Disease Rating Scale and its subscores, Hoehn and Yahr scale, Schwab and England scale, and Non-Motor Symptoms Scale. PD patients underwent pure-tone, speech audiometry, tympanometry, BAEP, oVEMPs, and cVEMPs, and compared to 15 age-matched control subjects. PD subjects showed abnormal BAEP wave morphology, prolonged absolute latencies of wave V and I–V interpeak latencies. Absent responses were the marked abnormality seen in oVEMP. Prolonged latencies with reduced amplitudes were seen in cVEMP responses. Rigidity and bradykinesia were correlated to the BAEP and cVEMP responses contralateral to the clinically more affected side. Contralateral and ipsilateral cVEMPs were significantly correlated to sleep (p = 0.03 and 0.001), perception (p = 0.03), memory/cognition (p = 0.025), and urinary scores (p = 0.03). The oVEMP responses showed significant correlations to cardiovascular (p = 0.01) and sexual dysfunctions (p = 0.013). PD is associated with BAEP and VEMP abnormalities that are correlated to the motor and some non-motor clinical characteristics. These abnormalities could be considered as potential electrophysiological biomarkers for brainstem dysfunction and its associated motor and non-motor features. PMID:28289399
Shalash, Ali Soliman; Hassan, Dalia Mohamed; Elrassas, Hanan Hani; Salama, Mohamed Mosaad; Méndez-Hernández, Edna; Salas-Pacheco, José M; Arias-Carrión, Oscar
Degeneration of several brainstem nuclei has been long related to motor and non-motor symptoms (NMSs) of Parkinson's disease (PD). Nevertheless, due to technical issues, there are only a few studies that correlate that association. Brainstem auditory-evoked potential (BAEP) and vestibular-evoked myogenic potential (VEMP) responses represent a valuable tool for brainstem assessment. Here, we investigated the abnormalities of BAEPs, ocular VEMPs (oVEMPs), and cervical VEMPs (cVEMPs) in patients with PD and its correlation to the motor and NMSs. Fifteen patients diagnosed as idiopathic PD were evaluated by Unified Parkinson's Disease Rating Scale and its subscores, Hoehn and Yahr scale, Schwab and England scale, and Non-Motor Symptoms Scale. PD patients underwent pure-tone, speech audiometry, tympanometry, BAEP, oVEMPs, and cVEMPs, and compared to 15 age-matched control subjects. PD subjects showed abnormal BAEP wave morphology, prolonged absolute latencies of wave V and I-V interpeak latencies. Absent responses were the marked abnormality seen in oVEMP. Prolonged latencies with reduced amplitudes were seen in cVEMP responses. Rigidity and bradykinesia were correlated to the BAEP and cVEMP responses contralateral to the clinically more affected side. Contralateral and ipsilateral cVEMPs were significantly correlated to sleep (p = 0.03 and 0.001), perception (p = 0.03), memory/cognition (p = 0.025), and urinary scores (p = 0.03). The oVEMP responses showed significant correlations to cardiovascular (p = 0.01) and sexual dysfunctions (p = 0.013). PD is associated with BAEP and VEMP abnormalities that are correlated to the motor and some non-motor clinical characteristics. These abnormalities could be considered as potential electrophysiological biomarkers for brainstem dysfunction and its associated motor and non-motor features.
Fujiki, Minoru; Kobayashi, Hidenori; Inoue, Ryo; Ishii, Keisuke
The present study evaluates motor functional recovery after C2 spinal cord hemisection with or without contralateral brachial root transection, which causes a condition that is similar to the crossed phrenic phenomenon on rats. Descending motor pathways, including the reticulospinal extrapyramidal tract and corticospinal pyramidal tracts, were evaluated by transcranial magnetic motor-evoked potentials (mMEPs) and direct cortical electrical motor-evoked potentials (eMEP), respectively. All MEPs recorded from the left forelimb were abolished immediately after the left C2 hemisection. Left mMEPs recovered dramatically immediately after contralateral right brachial root transection. Corticospinal eMEPs never recovered, regardless of transection. The facilitation of mMEPs in animals that had undergone combined contralateral root transection was well correlated with open-field behavioral motor performance. Both electrophysiological and neurological facilitations were significantly attenuated by the selective serotonin synthesis inhibitor para-chlorophenylalanine (p-CPA). These results suggest that serotonergic reticulospinal fibers located contralateral to hemisection contribute to the behavioral and electrophysiological improvement that immediately follows spinal cord injury (SCI).
Tsutsui, Shunji; Yamada, Hiroshi; Hashizume, Hiroshi; Minamide, Akihito; Nakagawa, Yukihiro; Iwasaki, Hiroshi; Yoshida, Munehito
Transcranial motor evoked potentials (TcMEPs) are widely used to monitor motor function during spinal surgery. However, they are much smaller and more variable in amplitude than responses evoked by maximal peripheral nerve stimulation, suggesting that a limited number of spinal motor neurons to the target muscle are excited by transcranial stimulation. The aim of this study was to quantify the proportion of motor neurons recruited during TcMEP monitoring under general anesthesia. In twenty patients who underwent thoracic and/or lumbar spinal surgery with TcMEP monitoring, the triple stimulation technique (TST) was applied to the unilateral upper arm intraoperatively. Total intravenous anesthesia was employed. Trains of four stimuli were delivered with maximal intensity and an inter-pulse interval of 1.5 ms. TST responses were recorded from the abductor digiti minimi muscle, and the negative peak amplitude and area were measured and compared between the TST test (two collisions between transcranial and proximal and distal peripheral stimulation) and control response (two collisions between two proximal and one distal peripheral stimulation). The highest degree of superimposition of the TST test and control responses was chosen from several trials per patient. The average ratios (test:control) were 17.1 % (range 1.8-38 %) for the amplitudes and 21.6 % (range 2.9-40 %) for the areas. The activity of approximately 80 % of the motor units to the target muscle cannot be detected by TcMEP monitoring. Therefore, changes in evoked potentials must be interpreted cautiously when assessing segmental motor function with TcMEP monitoring.
Zaaroor, M; Bleich, N; Chistyakov, A; Pratt, H; Feinsod, M
Motor evoked potentials and central motor conduction time (CMCT) were examined from both upper and lower limbs in patients with normal pressure hydrocephalus to find a predictor for the success of shunting procedures. The hypotheses that walking disturbances are due to pyramidal tract compression as well as the possibility that the upper limbs are affected subclinically in these patients were also studied. The study suggests that the walking disturbances are not the result of a major pyramidal tract dysfunction but probably involve the sensorimotor integration leading to normal gait. Furthermore, CMCT measured with electromagnetic motor stimulation can help in selecting the patients that will benefit from shunting. The study does not provide electrophysiological evidence of upper limb involvement in normal pressure hydrocephalus. PMID:9153613
Feys, H.; Van Hees, J.; Bruyninckx, F.; Mercelis, R.; De Weerdt, W.
OBJECTIVES—Prediction of motor recovery in the arm in patients with stroke is generally based on clinical examination. However, neurophysiological measures may also have a predictive value. The aims of this study were to assess the role of somatosensory (SSEPs) and motor (MEPs) evoked potentials in the prediction of arm motor recovery and to determine whether these measures added further predictive information to that gained from clinical examination. METHODS—Sixty four patients who had had a stroke and presented with obvious motor deficit of the arm were examined in terms of three clinical variables (motor performance, muscle tone, and overall disability) and for SSEPs and MEPs. Clinical and neurophysiological examinations were done at entry to the study (2 to 5 weeks poststroke), and at about 2 months after stroke. Further clinical follow up was conducted at 6 and 12 months after stroke. RESULTS—Neurophysiological measures made in the acute phase were of little use alone in predicting motor recovery of the arm at 2,6, and 12 months after stroke. At 2 months, the absence of SSEPs and MEPs indicated a very poor outcome. Conversely, if the responses were preserved, a great variation in motor outcome was found. Multiple regression analysis showed that the addition of SSEPs and MEPs to the clinical examination increased the possibility of predicting arm recovery in the long term. In the acute phase, the combination of the motor score and SSEPs were best able to predict outcome. The long term outcome based on variables taken at 2 months, was best predicted through incorporating the three clinical measures and MEPs. CONCLUSIONS—Neurophysiological measures alone are of limited value in predicting long term outcome. However, predictive accuracy is substantially improved through the combined use of both of these measures and clinical variables. PMID:10675214
Imai, T; Yamamoto, T; Ohkubo, Y; Kashiwagi, M; Chiba, S; Matsumoto, H
Changes of motor evoked potentials (MEPs) from the agonist and antagonist forearm muscles were investigated in 13 patients with Parkinson's disease and age-matched controls, in whom transcranial magnetic stimulation (TCMS) was delivered to the cortical hand motor area immediately before voluntary wrist flexion. MEPs recorded from the agonist muscles, namely the wrist flexors, were gradually facilitated in accordance with a shortening of the interval between TCMS and wrist flexion in both groups. In contrast, MEPs recorded from the antagonist muscles, namely the wrist extensors, were gradually facilitated as the intervals were shortened only in parkinsonian patients. The reciprocal facilitation of the antagonist MEPs was statistically significant when TCMS was delivered within 80 msec before the voluntary movements, suggesting the presence of the same underlying mechanism of symptomatic cocontraction observed in patients with Parkinson's disease.
Farajidavar, Aydin; Seifert, Jennifer L; Delgado, Mauricio R; Sparagana, Steven; Romero-Ortega, Mario I; Chiao, J-C
Intraoperative neurophysiological monitoring (IONM) is utilized to minimize neurological morbidity during spine surgery. Transcranial motor evoked potentials (TcMEPs) are principal IONM signals in which the motor cortex of the subject is stimulated with electrical pulses and the evoked potentials are recorded from the muscles of interest. Currently available monitoring systems require the connection of 40-60 lengthy lead wires to the patient. These wires contribute to a crowded and cluttered surgical environment, and limit the maneuverability of the surgical team. In this work, it was demonstrated that the cumbersome wired system is vulnerable to electromagnetic interference (EMI) produced by operating room (OR) equipment. It was hypothesized that eliminating the lengthy recording wires can remove the EMI induced in the IONM signals. Hence, a wireless system to acquire TcMEPs was developed and validated through bench-top and animal experiments. Side-by-side TcMEPs acquisition from the wired and wireless systems in animal experiments under controlled conditions (absence of EMI from OR equipment) showed comparable magnitudes and waveforms, thus demonstrating the fidelity in the signal acquisition of the wireless solution. The robustness of the wireless system to minimize EMI was compared with a wired-system under identical conditions. Unlike the wired-system, the wireless system was not influenced by the electromagnetic waves from the C-Arm X-ray machine and temperature management system in the OR.
Park, Hyun-Joo; Furmaga, Havan; Cooperrider, Jessica; Gale, John T.; Baker, Kenneth B.; Machado, Andre G.
Background Deep brain stimulation (DBS) targeting the dentato-thalamo-cortical (DTC) pathway at its origin in the lateral cerebellar nucleus (LCN) has been shown to enhance motor recovery in a rodent model of cortical ischemia. LCN DBS also yielded frequency specific changes in motor cortex excitability in the normal brain, indexed by motor evoked potential (MEP) amplitude. Objective To investigate the effect of cortical stroke on cortical motor excitability in a rodent ischemia model and to measure the effects of LCN DBS on post-ischemia excitability as a function of stimulation parameters. Methods Adult Sprague-Dawley rats were divided into two groups: naïve and stroke, with cortical ischemia induced through multiple, unilateral endothelin-1 injections. All animals were implanted with a bipolar electrode in the LCN opposite the affected hemisphere. MEPs were elicited from the affected hemisphere using intracortical microstimulation (ICMS) techniques. Multiple LCN DBS parameters were examined, including isochronal stimulation at 20, 30, 50, and 100 Hz as well as a novel burst stimulation pattern. Results ICMS-evoked MEPs were reduced in stroke (n=10) relative to naïve (n=12) animals. However, both groups showed frequency-dependent augmentation of cortical excitability in response to LCN DBS. In the naïve group, LCN DBS increased MEPs by 22–58%, while in the stroke group, MEPs were enhanced by 9–41% compared to OFF DBS conditions. Conclusions Activation of the DTC pathway increases cortical excitability in both naïve and post-stroke animals. These effects may underlie, at least partially, functional reorganization and therapeutic benefits associated with chronic LCN DBS in post-stroke animals. PMID:26215752
Chiou, Ruei-Jen; Lee, Hsiao-Yun; Chang, Chen-Wei; Lin, Kuan-Hung; Kuo, Chung-Chih
Motor cortex stimulation (MCS) is a promising clinical procedure to help alleviate chronic pain. Animal models demonstrated that MCS is effective in lessening nocifensive behaviors. The present study explored the effects of MCS on cortical somatosensory evoked potentials (SEPs) recorded at the primary somatosensory cortex (SI) of the rat. SEPs were evoked by electrical stimulation applied to the contralateral forepaws. Effects of different intensities, frequencies, and durations of MCS were tested. MCS at ≥2V suppressed SEPs of the ipsilateral SI. Suppression lasted 120 min at an intensity of 5 V. The optimal frequency was 50 Hz, and the duration was 30s. In contrast, MCS did not affect SEPs recorded on the contralateral SI. Cortical stimulation out of the motor cortex did not induce a decrease in the ipsilateral SEPs. We also investigated involvement of the endogenous opioid system in this inhibition of SEPs induced by MCS. The opioid antagonist, naloxone (0.5 mg/kg), was administered 30 min before MCS. Application of naloxone completely prevented the inhibitory effect of MCS on ipsilateral SEPs. These results demonstrate that MCS blocked the transmission of somatosensory information to the primary somatosensory cortex, and this interference was mediated by the endogenous opioid system. This inhibitory effect on sensory transmission induced by MCS may reflect its antinociceptive effect.
Ambardekar, A P; Sestokas, A K; Schwartz, D M; Flynn, J M; Rehman, M
Neurophysiologic monitors in the form of transcranial electric motor evoked potentials (tceMEPs) and somatosensory evoked potentials (SSEPs) have become widely used modalities to monitor spinal cord function during major orthopedic spine procedures. In combination with invasive and non-invasive clinical monitoring and an anesthesia information management system (AIMS), we promptly recognized an acute change in hemodynamic and neurophysiologic parameters, managed intraoperative spinal cord contusion, and successfully minimized iatrogenic injury to the spinal cord during corrective spine surgery.
Bharadwaj, Suparna; Haji, Faizal; Hebb, Matthew; Chui, Jason
Motor evoked potentials (MEPs) are commonly used to prevent neurological injury when operating in close proximity to the motor cortex or corticospinal pathway. We report a novel application of the NIM® nerve monitoring system (Medtronic@ NIM response 3.0) for intraoperative direct cortical (dc)-MEPs monitoring. A 69-year-old female patient presented with a 4month history of progressive left hemiparesis resulting from a large right sided posterior frontal meningioma that abutted and compressed the motor cortex. Motor cortical mapping and MEPs were indicated. The patient was anesthetized and maintained on total intravenous anesthetics. Compound muscle action potentials (CMAP) of the right upper limb were monitored using the NIM system. After a craniotomy was performed, we first used the Ojemann stimulator (monopolar) for dc-stimulation and then switched to use the monopolar nerve stimulator probe of the NIM system. The CMAP response was successfully elicited using the NIM stimulating probe (pulse width=250s, train frequency=7pulses/s, current=20mA). A gross total resection of the tumor was achieved with intermittent cortical mapping of MEPs. There were no intraoperative complications and the patient's motor function was preserved after the surgery. In this case, we reported the successful use of the NIM nerve monitoring system to elicit dc-MEPs under general anesthesia. The advantages of using this system include a simple set up and application, neurosurgeon familiarity, wide availability and lower cost. dc-MEPs can be achieved using the NIM system. We conclude that the NIM nerve monitoring system is a feasible alternative to standard neurophysiological monitoring systems.
Gad, Parag; Lavrov, Igor; Shah, Prithvi; Zhong, Hui; Roy, Roland R.; Gerasimenko, Yury
The rat spinal cord isolated from supraspinal control via a complete low- to midthoracic spinal cord transection produces locomotor-like patterns in the hindlimbs when facilitated pharmacologically and/or by epidural electrical stimulation. To evaluate the role of epidural electrical stimulation in enabling motor control (eEmc) for locomotion and posture, we recorded potentials evoked by epidural spinal cord stimulation in selected hindlimb muscles during stepping and standing in adult spinal rats. We hypothesized that the temporal details of the phase-dependent modulation of these evoked potentials in selected hindlimb muscles while performing a motor task in the unanesthetized state would be predictive of the potential of the spinal circuitries to generate stepping. To test this hypothesis, we characterized soleus and tibialis anterior (TA) muscle responses as middle response (MR; 4–6 ms) or late responses (LRs; >7 ms) during stepping with eEmc. We then compared these responses to the stepping parameters with and without a serotoninergic agonist (quipazine) or a glycinergic blocker (strychnine). Quipazine inhibited the MRs induced by eEmc during nonweight-bearing standing but facilitated locomotion and increased the amplitude and number of LRs induced by eEmc during stepping. Strychnine facilitated stepping and reorganized the LRs pattern in the soleus. The LRs in the TA remained relatively stable at varying loads and speeds during locomotion, whereas the LRs in the soleus were strongly modulated by both of these variables. These data suggest that LRs facilitated electrically and/or pharmacologically are not time-locked to the stimulation pulse but are highly correlated to the stepping patterns of spinal rats. PMID:23761695
Gad, Parag; Lavrov, Igor; Shah, Prithvi; Zhong, Hui; Roy, Roland R; Edgerton, V Reggie; Gerasimenko, Yury
The rat spinal cord isolated from supraspinal control via a complete low- to midthoracic spinal cord transection produces locomotor-like patterns in the hindlimbs when facilitated pharmacologically and/or by epidural electrical stimulation. To evaluate the role of epidural electrical stimulation in enabling motor control (eEmc) for locomotion and posture, we recorded potentials evoked by epidural spinal cord stimulation in selected hindlimb muscles during stepping and standing in adult spinal rats. We hypothesized that the temporal details of the phase-dependent modulation of these evoked potentials in selected hindlimb muscles while performing a motor task in the unanesthetized state would be predictive of the potential of the spinal circuitries to generate stepping. To test this hypothesis, we characterized soleus and tibialis anterior (TA) muscle responses as middle response (MR; 4-6 ms) or late responses (LRs; >7 ms) during stepping with eEmc. We then compared these responses to the stepping parameters with and without a serotoninergic agonist (quipazine) or a glycinergic blocker (strychnine). Quipazine inhibited the MRs induced by eEmc during nonweight-bearing standing but facilitated locomotion and increased the amplitude and number of LRs induced by eEmc during stepping. Strychnine facilitated stepping and reorganized the LRs pattern in the soleus. The LRs in the TA remained relatively stable at varying loads and speeds during locomotion, whereas the LRs in the soleus were strongly modulated by both of these variables. These data suggest that LRs facilitated electrically and/or pharmacologically are not time-locked to the stimulation pulse but are highly correlated to the stepping patterns of spinal rats.
Ito, Masaki; Kuroda, Satoshi; Takano, Kazuya; Maruichi, Katsuhiko; Chiba, Yasuhiro; Morimoto, Yuji; Iwasaki, Yoshinobu
Although motor cortex stimulation (MCS) has been accepted as an effective therapeutic option for central pain, the efficacy of MCS widely varies among previous reports. In this report, we describe our recent trial for successful MCS in 3 patients with central pain due to cerebral stroke. Medical treatments were transiently effective, but gradually became ineffective in all of the cases. During surgery, the appropriate cortical target was determined by using neuronavigation, somatosensory evoked potential (SEP), and motor evoked potential (MEP). A flat, four-plate electrode was positioned on the dura mater parallel to the motor cortex. After surgery, pain almost resolved in 2 of 3 patients and markedly improved in another. The pain relief depended on their motor function. These findings strongly suggest that both patient selection and intraoperative monitoring for targeting the motor cortex are quite important for successful MCS, although further studies were essential.
Logullo, F; Di Bella, P; Provinciali, L
The clinical and neurophysiological findings in a patient with a typical stiff-man syndrome and their three-year evolution are described. The patient had high titers of anti-glutamic acid decarboxylase antibodies in both serum and cerebrospinal fluid. Magnetic resonance imaging (MRI) of brain and spinal cord was normal. Transcranial magnetic stimulation (TMS) revealed a distinctive motor evoked potential (MEP) pattern in proximal lower limb muscles consisting of markedly increased MEP amplitudes and MEP/M ratios, reduced excitability thresholds, and absent silent period. However, MEP latencies, central and peripheral conduction times and amplitudes obtained by magnetic spinal root stimulation were normal. Treatment with benzodiazepine and baclofen normalized both the clinical picture and the MEP values. TMS may be useful both as a diagnostic tool and to monitor the response to drug treatment.
Nardone, Raffaele; Bergmann, Jürgen; Kronbichler, Martin; Lochner, Piergiorgio; Caleri, Francesca; Tezzon, Frediano; Ladurner, Gunther; Golaszewski, Stefan
Because in the early phases of spinal cord ischemia magnetic resonance imaging (MRI) can be normal, its clinical diagnosis is often difficult. We aimed to explore if motor-evoked potentials (MEPs) recordings may contribute to earlier diagnosis of spinal cord stroke. The clinical, MRI, and MEP findings in one case each of cervical and lumbar spinal cord infarction were reported. Spinal MRI at admission was unremarkable in both patients. At this time, MEPs were abnormal in both patients, to the upper and lower limbs in the first patient, exclusively to the lower limbs in the second. Follow-up MRI examinations documented an infarction in the territory of the anterior spinal artery and of the Adamkiewicz artery, respectively. MEP study can be useful in demonstrating spinal cord involvement also when radiological evidence for spinal cord damage is absent or equivocal. Early diagnosis may allow earlier intervention and contribute to improved patient management.
Tomio, Ryosuke; Akiyama, Takenori; Toda, Masahiro; Ohira, Takayuki; Yoshida, Kazunari
OBJECTIVE Transcranial motor evoked potential (tMEP) monitoring is popular in neurosurgery; however, the accuracy of tMEP can be impaired by craniotomy. Each craniotomy procedure and changes in the CSF levels affects the current spread. The aim of this study was to investigate the influence of several craniotomies on tMEP monitoring by using C3-4 transcranial electrical stimulation (TES). METHODS The authors used the finite element method to visualize the electric field in the brain, which was generated by TES, using realistic 3D head models developed from T1-weighted MR images. Surfaces of 5 layers of the head (brain, CSF, skull, subcutaneous fat, and skin layer) were separated as accurately as possible. The authors created 5 models of the head, as follows: normal head; frontotemporal craniotomy; parietal craniotomy; temporal craniotomy; and occipital craniotomy. The computer simulation was investigated by finite element methods, and clinical recordings of the stimulation threshold level of upper-extremity tMEP (UE-tMEP) during neurosurgery were also studied in 30 patients to validate the simulation study. RESULTS Bone removal during the craniotomy positively affected the generation of the electric field in the motor cortex if the motor cortex was just under the bone at the margin of the craniotomy window. This finding from the authors' simulation study was consistent with clinical reports of frontotemporal craniotomy cases. A major decrease in CSF levels during an operation had a significantly negative impact on the electric field when the motor cortex was exposed to air. The CSF surface level during neurosurgery depends on the body position and location of the craniotomy. The parietal craniotomy and temporal craniotomy were susceptible to the effect of the changing CSF level, based on the simulation study. A marked increase in the threshold following a decrease in CSF was actually recorded in clinical reports of the UE-tMEP threshold from a temporal craniotomy
Goetz, Stefan M.; Luber, Bruce; Lisanby, Sarah H.; Peterchev, Angel V.
Objective Motor evoked potentials (MEPs) play a pivotal role in transcranial magnetic stimulation (TMS), e.g., for determining the motor threshold and probing cortical excitability. Sampled across the range of stimulation strengths, MEPs outline an input–output (IO) curve, which is often used to characterize the corticospinal tract. More detailed understanding of the signal generation and variability of MEPs would provide insight into the underlying physiology and aid correct statistical treatment of MEP data. Methods A novel regression model is tested using measured IO data of twelve subjects. The model splits MEP variability into two independent contributions, acting on both sides of a strong sigmoidal nonlinearity that represents neural recruitment. Traditional sigmoidal regression with a single variability source after the nonlinearity is used for comparison. Results The distribution of MEP amplitudes varied across different stimulation strengths, violating statistical assumptions in traditional regression models. In contrast to the conventional regression model, the dual variability source model better described the IO characteristics including phenomena such as changing distribution spread and skewness along the IO curve. Conclusions MEP variability is best described by two sources that most likely separate variability in the initial excitation process from effects occurring later on. The new model enables more accurate and sensitive estimation of the IO curve characteristics, enhancing its power as a detection tool, and may apply to other brain stimulation modalities. Furthermore, it extracts new information from the IO data concerning the neural variability—information that has previously been treated as noise. PMID:24794287
Wilkinson, Marshall F; Chowdhury, Tumul; Mutch, W Alan; Kaufmann, Anthony M
OBJECTIVE Hemifacial spasm (HFS) is a cranial nerve hyperactivity disorder characterized by unique neurophysiological features, although the underlying pathophysiology remains disputed. In this study, the authors compared the effects of desflurane on facial motor evoked potentials (MEPs) from the spasm and nonspasm sides of patients who were undergoing microvascular decompression (MVD) surgery to test the hypothesis that HFS is associated with a central elevation of facial motor neuron excitability. METHODS Facial MEPs were elicited in 31 patients who were undergoing MVD for HFS and were administered total intravenous anesthesia (TIVA) with or without additional desflurane, an inhaled anesthetic known to centrally suppress MEPs. All measurements were completed before dural opening while a consistent mean arterial blood pressure was maintained and electroencephalography was performed. The activation threshold voltage and mean amplitudes of the MEPs from both sides of the face were compared. RESULTS There was a significantly lower mean activation threshold of facial MEPs on the spasm side than on the nonspasm side (mean ± SD 162.9 ± 10.1 vs 198.3 ± 10.1 V, respectively; p = 0.01). In addition, MEPs were also elicited more readily when single-pulse transcranial electrical stimulation was used on the spasm side (74% vs 31%, respectively; p = 0.03). Although desflurane (1 minimum alveolar concentration) suppressed facial MEPs on both sides, the suppressive effects of desflurane were less on the spasm side than on the nonspasm side (59% vs 79%, respectively; p = 0.03), and M waves recorded from the mentalis muscle remained unchanged, which indicates that desflurane did not affect the peripheral facial nerve or neuromuscular junction. CONCLUSIONS Centrally acting inhaled anesthetic agents can suppress facial MEPs and therefore might interfere with intraoperative monitoring. The elevated motor neuron excitability and differential effects of desflurane between the spasm
Grimonprez, Annelies; Raedt, Robrecht; De Taeye, Leen; Larsen, Lars Emil; Delbeke, Jean; Boon, Paul; Vonck, Kristl
Vagus nerve stimulation (VNS) is a treatment for refractory epilepsy and depression. Previous studies using invasive recording electrodes showed that VNS induces laryngeal motor-evoked potentials (LMEPs) through the co-activation of the recurrent laryngeal nerve and subsequent contractions of the laryngeal muscles. The present study investigates the feasibility of recording LMEPs in chronically VNS-implanted rats, using a minimally-invasive technique, to assess effective current delivery to the nerve and to determine optimal VNS output currents for vagal fiber activation. Three weeks after VNS electrode implantation, signals were recorded using an electromyography (EMG) electrode in the proximity of the laryngeal muscles and a reference electrode on the skull. The VNS output current was gradually ramped up from 0.1 to 1.0 mA in 0.1 mA steps. In 13/27 rats, typical LMEPs were recorded at low VNS output currents (median 0.3 mA, IQR 0.2-0.3 mA). In 11/27 rats, significantly higher output currents were required to evoke electrophysiological responses (median 0.7 mA, IQR 0.5-0.7 mA, p < 0.001). The latencies of these responses deviated significantly from LMEPs (p < 0.05). In 3/27 rats, no electrophysiological responses to simulation were recorded. Minimally invasive LMEP recordings are feasible to assess effective current delivery to the vagus nerve. Furthermore, our results suggest that low output currents are sufficient to activate vagal fibers.
Casula, Elias P; Tarantino, Vincenza; Basso, Demis; Arcara, Giorgio; Marino, Giuliana; Toffolo, Gianna Maria; Rothwell, John C; Bisiacchi, Patrizia S
The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) have been mostly investigated by peripheral motor-evoked potentials (MEPs). New TMS-compatible EEG systems allow a direct investigation of the stimulation effects through the analysis of TMS-evoked potentials (TEPs). We investigated the effects of 1-Hz rTMS over the primary motor cortex (M1) of 15 healthy volunteers on TEP evoked by single pulse TMS over the same area. A second experiment in which rTMS was delivered over the primary visual cortex (V1) of 15 healthy volunteers was conducted to examine the spatial specificity of the effects. Single-pulse TMS evoked four main components: P30, N45, P60 and N100. M1-rTMS resulted in a significant decrease of MEP amplitude and in a significant increase of P60 and N100 amplitude. There was no effect after V1-rTMS. 1-Hz rTMS appears to increase the amount of inhibition following a TMS pulse, as demonstrated by the higher N100 and P60, which are thought to originate from GABAb-mediated inhibitory post-synaptic potentials. Our results confirm the reliability of the TMS-evoked N100 as a marker of cortical inhibition and provide insight into the neuromodulatory effects of 1-Hz rTMS. The present finding could be of relevance for therapeutic and diagnostic purposes.
Hashimoto, Yuko; Gotanda, Yuki; Ito, Takahiko; Ushijima, Kazuo
Motor evoked potential (MEP) monitoring has been employed to detect the spinal cord injury during spinal, neurosurgical and cardiovascular operations. Muscle relaxants diminish the amplitude of MEP because MEP is the picture of electromyogram. In 5 cases undergoing MEP monitoring, we examined the effect of rocuronium followed by the administration of sugammadex on MEP Anesthesia was induced with propofol (target controlled infusion 3.0-3.5 microg x ml(-1)) and remifentanil 0.15-0.3 microg x kg(-1) x min(-1), and the trachea was intubated with the use of rocuronium 0.6 mg x kg(-1) without any muscle rigidity, bucking and laryngospasm. General anesthesia was maintained by total intravenous anesthesia using propofol and remifentanil with no muscle relaxants. Immediately after the tracheal intubation, sugammadex 4 mg x kg(-1) was intravenously given. The amplitude of MEP was measured just before the administration of rocuronium, immediately after the tracheal intubation, and 1, 2, 3, 5 min following the administration of sugammadex. Sugammadex restored the MEP amplitude, deteriorated by rocuronium, in 3 to 5 min to the level of non-paralytic muscles. In one case, it took 8 min to restore the MEP of hemiparetic leg. Taking these findings into consideration, it is likely that rocuronium might not affect the MEP when reversed by sugammadex, and should be safe for smooth tracheal intubation in patients who need MEP monitoring.
Cakar, Engin; Akyuz, Gulseren; Durmus, Oguz; Bayman, Levent; Yagci, Ilker; Karadag-Saygi, Evrim; Gunduz, Osman Hakan
The standardization of patient evaluation and monitoring methods has a special importance in evaluating the effectiveness of therapeutic methods using drugs or rehabilitative techniques in stroke rehabilitation. The aim of this study was to investigate the relationships between clinical instruments and transcranial magnetic stimulation (TMS)-evoked neurophysiological parameters in stroke patients. This study included 22 chronic post-stroke patients who were clinically assessed using the Motricity Index (MI), finger-tapping test (FTT), Motor Activity Log (MAL) 28, Brunnstrom motor staging and Ashworth Scale (ASH). Motor-evoked potential (MEP) latency and amplitude, resting motor threshold (rMT) and central motor conduction time (CMCT) were measured with TMS. Shorter MEP-latency, shorter CMCT, higher motor-evoked potential amplitude, and diminished rMT exhibited significant correlations with clinical measures evaluating motor stage, dexterity, and daily life functionality. rMT exhibited a negative correlation with hand and lower extremity Brunnstrom stages (r = -0.64, r = -0.51, respectively), MI score (r = -0.48), FTT score (r = -0.69), and also with amount of use scale and quality of movement scale of MAL 28 scores (r = -0.61, r = -0.62, respectively). Higher MEP amplitude and diminished rMT showed positive correlations with reduced ASH score (r = -0.65, r = 0.44, respectively). The TMS-evoked neurophysiologic parameters including MEP latency, amplitude, rMT and CMCT generally have positive correlation with clinical measures which evaluate motor stage, dexterity and daily life functionality. Additionally, spasticity has also remarkable relationships with MEP amplitude and rMT. These results suggest that TMS-evoked neurophysiological parameters were useful measures for monitoring post-stroke patients.
Kobayashi, Kazuyoshi; Imagama, Shiro; Ito, Zenya; Ando, Kei; Hida, Tetsuro; Ito, Kenyu; Tsushima, Mikito; Ishikawa, Yoshimoto; Matsumoto, Akiyuki; Nishida, Yoshihiro; Ishiguro, Naoki
OBJECTIVE Corrective surgery for spinal deformities can lead to neurological complications. Several reports have described spinal cord monitoring in surgery for spinal deformity, but only a few have included patients younger than 20 years with adolescent idiopathic scoliosis (AIS). The goal of this study was to evaluate the characteristics of cases with intraoperative transcranial motor evoked potential (Tc-MEP) waveform deterioration during posterior corrective fusion for AIS. METHODS A prospective database was reviewed, comprising 68 patients with AIS who were treated with posterior corrective fusion in a prospective database. A total of 864 muscles in the lower extremities were chosen for monitoring, and acceptable baseline responses were obtained from 819 muscles (95%). Intraoperative Tc-MEP waveform deterioration was defined as a decrease in intraoperative amplitude of ≥ 70% of the control waveform. Age, Cobb angle, flexibility, operative time, estimated blood loss (EBL), intraoperative body temperature, blood pressure, number of levels fused, and correction rate were examined in patients with and without waveform deterioration. RESULTS The patients (3 males and 65 females) had an average age of 14.4 years (range 11-19 years). The mean Cobb angles before and after surgery were 52.9° and 11.9°, respectively, giving a correction rate of 77.4%. Fourteen patients (20%) exhibited an intraoperative waveform change, and these occurred during incision (14%), after screw fixation (7%), during the rotation maneuver (64%), during placement of the second rod after the rotation maneuver (7%), and after intervertebral compression (7%). Most waveform changes recovered after decreased correction or rest. No patient had a motor deficit postoperatively. In multivariate analysis, EBL (OR 1.001, p = 0.085) and number of levels fused (OR 1.535, p = 0.045) were associated with waveform deterioration. CONCLUSIONS Waveform deterioration commonly occurred during rotation maneuvers
Zhang, Yi Ping; Shields, Lisa B E; Zhang, Yongjie; Pei, Jiong; Xu, Xiao-Ming; Hoskins, Rachel; Cai, Jun; Qiu, Meng Sheng; Magnuson, David S K; Burke, Darlene A; Shields, Christopher B
Assessment of locomotor function of rodents may be supplemented using electrophysiological tests which monitor the integrity of ascending and descending tracts as well as the focal circuitry of the spinal cord in non-sedated rodents. Magnetically induced SSEPs (M-SSEPs) were elicited in rats by activating the hindpaw using magnetic stimulation (MS). M-SSEP response latencies were slightly longer than those elicited by electrical stimulation. M-SSEPs were eliminated following selective dorsal column lacerations of the spinal cord, indicating that they were transmitted via this tract. Magnetically induced motor evoked potentials (M-MEPs) were elicited in mice following transcranial MS and recorded from the gastrocnemius muscles. M-MEPs performed on myelin deficient mice demonstrated longer onset latencies and smaller amplitudes than in wild-type mice. Magnetically induced H-reflexes (MH-reflexes) which assess local circuitry in the lumbosacral area of the spinal cord were performed in rats. This response disappeared following an L3 contusion spinal cord injury, however, kainic acid (KA) injection at L3, known to selectively destroy interneurons, caused a shorter latency and an increase in the amplitude of the MH-reflex. M-SSEPs and MH-reflexes in rats and M-MEPs in mice compliment locomotor evaluation in assessing the functional integrity of the spinal cord under normal and pathological conditions in the non-sedated animal.
Krammer, Matthias Johannes; Wolf, Stefan; Schul, David Baruch; Gerstner, Werner; Lumenta, Christianto Bernardo
Intraoperative motor evoked potential (MEP) monitoring in patients with spinal and cranial lesions is thought to be a valuable tool for prevention of postoperative motor deficits. Aim of this study was to investigate its diagnostic value in a spinal and a cranial patient group. Ninety-six patients, 31 with spinal and 65 with intracranial lesions, were studied. Transcranial stimulation was performed with a high-frequency electrical train stimulation using two subdermal needle electrodes. MEPs were recorded from the pathology-related muscles. Decreasing amplitudes of 50% or more, increasing stimulus intensities of 20% or more or increased latencies were taken as warning criteria. MEP recording was possible in 90% of the spinal and 98% of the cranial group. With two further exclusions, 28 patients of the spinal and 62 of the cranial group were analyzed. We saw a temporary maximum amplitude reduction of 50% or more and an increase in stimulation intensity of 20% or more in 8 spinal and 29 cranial patients. Five of the spinal and nine of the cranial patients deteriorated in motor function postoperatively. One patient with normal MEP monitoring showed a temporary motor weakness postoperatively. Latencies were normal in all patients. Given both warning criteria, intraoperative MEP changes had a sensitivity of 83%/ 100% and a specificity of 86%/ 62% (spinal/ cranial group). The positive predictive value of MEP changes for postoperative motor function deterioration was 63%/ 31%, and the negative predictive value was 95%/ 100%. Transcranial electrical monitoring of MEP is a practicable and safe method. However, there are many events, which can cause amplitude changes of MEP independent from surgical manipulations. Although sensitivity is high for both groups, this results in a moderate specificity for the cranial group and a low positive predictive value for both groups.
Epstein, Nancy E.
Intraoperative neural monitoring (IONM), utilizing somatosensory evoked potentials (SEP) and electromyography (EMG), was introduced to cervical spine surgery in the late 1980's. However, as SEP only provided physiological data regarding the posterior cord, new motor deficits were observed utilizing SEP alone. This prompted the development of motor evoked potential monitoring (MEP) which facilitated real-time assessment of the anterior/anterolateral spinal cord. Although all three modalities, SEP, EMG, and MEP, are routinely available for IONM of cervical spine procedures, MEP are not yet routinely employed. The purpose of this review is to emphasize that MEP should now routinely accompany SEP and EMG when performing IONM of cervical spine surgery. Interestingly, one of the most common reasons for malpractice suits involving the cervical spine, is quadriparesis/quadriplegia following a single level anterior cervical diskectomy and fusion (ACDF). Previously, typical allegations in these suits included; negligent surgery, lack of informed consent, failure to diagnose/treat, and failure to brace. Added to this list, perhaps, as the 5th most reason for a suit will be failure to monitor with MEP. This review documents the value of MEP monitoring in addition to SEP and EMG monitoring in cervical spine surgery. The addition of MEP0 should minimize major motor injuries, and more accurately and reliably detect impending anterior cord deterioration that may be missed with SEP monitoring alone. PMID:24340237
Yellin, Joseph L; Wiggins, Cheryl R; Franco, Alier J; Sankar, Wudbhav N
Transcranial electric stimulation (TES) motor evoked potentials (MEPs) have become a regular part of intraoperative neurophysiologic monitoring (IONM) for posterior spinal fusion (PSF) surgery. Almost all of the relative contraindications to TES have come and gone. One exception is in the case of patients with a cochlear implant (CI). Herein we illustrate two cases of pediatric patients with CIs who underwent PSF using TES MEPs as part of IONM. In both instances the patients displayed no untoward effects from TES, and post-operatively both CIs were intact and functioning as they were prior to surgery.
Kallioniemi, E; Pääkkönen, A; Julkunen, P
Transcranial magnetic stimulation (TMS) can be applied to modulate cortical phenomena. The modulation effect is dependent on the applied stimulation frequency. Repetition suppression (RS) has been demonstrated in the motor system using TMS with short suprathreshold 1-Hz stimulation trains repeated at long inter-train intervals. RS has been reported to occur in the resting motor-evoked potentials (MEPs) with respect to the first pulse in a train of stimuli. Although this RS in the motor system has been described in previous studies, the neuronal origin of the phenomenon is still poorly understood. The present study evaluated RS in three TMS-induced motor responses; resting and active MEPs as well as corticospinal silent periods (SPs) in order to clarify the mechanism behind TMS-induced RS. We studied 10 healthy right-handed subjects using trains of four stimuli with stimulation intensities of 120% of the resting motor threshold (rMT) and 120% of the silent period threshold for an SP duration of 30 ms (SPT30). Inter-trial interval was 20s, with a 1-s inter-stimulus interval within the trains. We confirmed that RS appears in resting MEPs (p < 0.001), whereas active MEPs did not exhibit RS (p > 0.792). SPs, on the contrary, lengthened (p < 0.001) indicating modulation of cortical inhibition. The effects of the two stimulation intensities exhibited a similar trend; however, the SPT30 evoked a more profound inhibitory effect compared to that achieved by rMT. Moreover, the resting MEP amplitudes and SP durations correlated (rho ⩽ -0.674, p < 0.001) and the pre-TMS EMG level did not differ between stimuli in resting MEPs (F = 0.0, p ⩾ 0.999). These results imply that the attenuation of response size seen in resting MEPs might originate from increasing activity of inhibitory GABAergic interneurons which relay the characteristics of SPs.
Eisen, A; Siejka, S; Schulzer, M; Calne, D
Peak-to-peak measurement of the maximum amplitude motor evoked potential (MAXMEP) elicited by 20 consecutive transcranial magnetic stimuli recorded from the contracting thenar and hypothenar muscles measured 9.8 +/- 2.0 mV and 7.25 +/- 2.9 mV respectively (P less than 0.01). The ratio of MAXMEP/CMAP measured 92.6 +/- 25.8% and 54.8 +/- 12.3% respectively (P less than 0.001). Repeat studies showed good individual reproducibility. Amplitudes declined linearly with age (r = -0.836 for thenar MAXMEP P less than 0.001). It is argued that MAXMEP related to age is more meaningful than the MEP/CMAP wave ratio and is proportional to the number of fast conducting cortical motor neurons excited. In 7/18 patients with Parkinson's disease (PD) MAXMEP was increased; in 2 other patients MAXMEP was decreased for their age.
Tsutsui, Shunji; Iwasaki, Hiroshi; Yamada, Hiroshi; Hashizume, Hiroshi; Minamide, Akihito; Nakagawa, Yukihiro; Nishi, Hideto; Yoshida, Munehito
Transcranial motor evoked potentials (TcMEPs) are widely used to monitor motor function during spinal surgery. Improvements in transcranial stimulation techniques and general anesthesia have made it possible to record reliable and reproducible potentials. However, TcMEPs are much smaller in amplitude compared with compound muscle action potentials (CMAPs) evoked by maximal peripheral nerve stimulation. In this study, multi-train transcranial electrical stimulation (mt-TES) was introduced to enhance TcMEPs, and the optimal setting of mt-TES was investigated. In 30 patients undergoing surgical correction of spinal deformities (4 males and 26 females with normal motor status; age range 11-75 years), TcMEPs from the abductor hallucis (AH) and quadriceps femoris (QF) were analyzed. A multipulse (train) stimulus with an individual pulse width of 0.5 ms and an inter-pulse interval of 2 ms was delivered repeatedly (2-7 times) at different rates (2, 5, and 10 Hz). TcMEP amplitudes increased with the number of train stimuli for AH, with the strongest facilitation observed at 5 Hz. The response amplitude increased 6.1 times on average compared with single-train transcranial electrical stimulation (st-TES). This trend was also observed in the QF. No adverse events (e.g., seizures, cardiac arrhythmias, scalp burns, accidental injury resulting from patient movement) were observed in any patients. Although several facilitative techniques using central or peripheral stimuli, preceding transcranial electrical stimulation, have been recently employed to augment TcMEPs during surgery, responses are still much smaller than CMAPs. Changing from conventional st-TES to mt-TES has potential to greatly enhance TcMEP responses.
Ma, Teng; Li, Hui; Deng, Lili; Yang, Hao; Lv, Xulin; Li, Peiyang; Li, Fali; Zhang, Rui; Liu, Tiejun; Yao, Dezhong; Xu, Peng
Objective. Movement control is an important application for EEG-BCI (EEG-based brain–computer interface) systems. A single-modality BCI cannot provide an efficient and natural control strategy, but a hybrid BCI system that combines two or more different tasks can effectively overcome the drawbacks encountered in single-modality BCI control. Approach. In the current paper, we developed a new hybrid BCI system by combining MI (motor imagery) and mVEP (motion-onset visual evoked potential), aiming to realize the more efficient 2D movement control of a cursor. Main result. The offline analysis demonstrates that the hybrid BCI system proposed in this paper could evoke the desired MI and mVEP signal features simultaneously, and both are very close to those evoked in the single-modality BCI task. Furthermore, the online 2D movement control experiment reveals that the proposed hybrid BCI system could provide more efficient and natural control commands. Significance. The proposed hybrid BCI system is compensative to realize efficient 2D movement control for a practical online system, especially for those situations in which P300 stimuli are not suitable to be applied.
Olex-Zarychta, Dorota; Koprowski, Robert; Sobota, Grzegorz; Wróbel, Zygmunt
The aim of the study was to determine the applicability of magnetic stimulation and magnetic motor evoked potentials (MEPs) in motor asymmetry studies by obtaining quantitative and qualitative measures of efferent activity during low intensity magnetic stimulation of the dominant and non-dominant lower extremities. Magnetic stimulation of the tibial nerve in the popliteal fossa was performed in 10 healthy male right-handed and right-footed young adults. Responses were recorded from the lateral head of the gastrocnemius muscles of the right and left lower extremities. Response characteristics (duration, onset latency, amplitude) were analyzed in relation to the functional dominance of the limbs and in relation to the direction of the current in the magnetic coil by use of the Wilcoxon pair sequence test. The CCW direction of coil current was related to reduced amplitudes of recorded MEPs. Greater amplitudes of evoked potentials were recorded in the non-dominant extremity, both in the CW and CCW coil current directions, with the statistical significance of this effect (p=0.005). No differences in duration of response were found in the CW current direction, while in CCW the time of the left-side response was prolonged (p=0.01). In the non-dominant extremity longer onset latencies were recorded in both current directions, but only for the CW direction the side asymmetries showed a statistical significance of p=0.005. In the dominant extremity the stimulation correlated with stronger paresthesias, especially using the CCW direction of coil current. The results indicate that low intensity magnetic stimulation may be useful in quantitative and qualitative research into the motor asymmetry.
Messina, Irene; Cattaneo, Luigi; Venuti, Paola; de Pisapia, Nicola; Serra, Mauro; Esposito, Gianluca; Rigo, Paola; Farneti, Alessandra; Bornstein, Marc H.
Neuroimaging reveals that infant cries activate parts of the premotor cortical system. To validate this effect in a more direct way, we used event-related transcranial magnetic stimulation (TMS). Here, we investigated the presence and the time course of modulation of motor cortex excitability in young adults who listened to infant cries. Specifically, we recorded motor evoked potentials (MEPs) from the biceps brachii (BB) and interosseus dorsalis primus (ID1) muscles as produced by TMS delivered from 0 to 250 ms after sound onset in six steps of 50 ms in 10 females and 10 males. We observed an excitatory modulation of MEPs at 100 ms from the onset of infant cry specific to females and to the ID1 muscle. We regard this modulation as a response to natural cry sounds because it was attenuated to stimuli increasingly different from natural cry and absent in a separate group of females who listened to non-cry stimuli physically matched to natural infant cries. Furthermore, the 100-ms latency of this response is not compatible with a voluntary reaction to the stimulus but suggests an automatic, bottom-up audiomotor association. The brains of adult females appear to be tuned to respond to infant cries with automatic motor excitation. PMID:26779061
Furmaga, Havan; Park, Hyun-Joo; Cooperrider, Jessica; Baker, Kenneth B.; Johnson, Matthew; Gale, John T.; Machado, Andre G.
Few preclinical or clinical studies have evaluated the effect of anesthetics on motor evoked potentials (MEPs), either alone or in the presence of conditioning stimuli such as deep brain stimulation (DBS). In this study we evaluated the effects of two commonly used anesthetic agents, propofol and ketamine (KET), on MEPs elicited by intra-cortical microstimulation of the motor cortex in a rodent model with and without DBS of the dentatothalamocortical (DTC) pathway. The effects of propofol anesthesia on MEP amplitudes during DTC DBS were found to be highly dose dependent. Standard, but not high, dose propofol potentiated the facilitatory effects of 30 Hz DTC DBS on MEPs. This facilitation was sustained and phase-dependent indicating that, compared to high dose propofol, standard dose propofol has a beta-band excitatory effect on cortical networks. In contrast, KET anesthetic demonstrated a monotonic relationship with increasing frequencies of stimulation, such that the highest frequency of stimulation resulted in the greatest MEP amplitude. KET also showed phase dependency but less pronounced than standard dose propofol. The results underscore the importance of better understanding the complex effects of anesthetics on cortical networks and exogenous stimuli. Choice of anesthetic agents and dosing may significantly confound or even skew research outcomes, including experimentation in novel DBS indications and paradigms. PMID:24904312
Drzymała-Celichowska, Hanna; Raikova, Rositsa; Krutki, Piotr
Slow motor units (MUs) have no sag in their unfused tetani. This study in anesthetized rats shows that the sag can be observed in slow soleus MUs after prolonged activity. Twitches and unfused tetanic contractions were recorded from male (n=35) and female (n=39) MUs before and after the four minutes of the fatigue test (trains of 13 pulses at 40 Hz repeated every second). After this activity twitch contractions potentiated and a shift in the steep part of the force-frequency curve towards lower frequencies was observed in both sexes. Initially no sag was visible in unfused tetani, but after the fatigue test the phenomenon was observed in 77% of male, while in 13% of female MUs, the result consistent with the previously reported higher content of IIa myosin and faster contraction of MUs in male soleus. The decomposition of tetani with sag into trains of twitch-shape responses to consecutive stimuli revealed higher forces of initial decomposed twitches than later. The revealed alterations the force development due to long-lasting activation of slow MUs were sex-related and more pronounced in male soleus.
Sykes, Matthew; Matheson, Natalie A.; Brownjohn, Philip W.; Tang, Alexander D.; Rodger, Jennifer; Shemmell, Jonathan B. H.; Reynolds, John N. J.
Repetitive transcranial magnetic stimulation (rTMS) is primarily used in humans to change the state of corticospinal excitability. To assess the efficacy of different rTMS stimulation protocols, motor evoked potentials (MEPs) are used as a readout due to their non-invasive nature. Stimulation of the motor cortex produces a response in a targeted muscle, and the amplitude of this twitch provides an indirect measure of the current state of the cortex. When applied to the motor cortex, rTMS can alter MEP amplitude, however, results are variable between participants and across studies. In addition, the mechanisms underlying any change and its locus are poorly understood. In order to better understand these effects, MEPs have been investigated in vivo in animal models, primarily in rats. One major difference in protocols between rats and humans is the use of general anesthesia in animal experiments. Anesthetics are known to affect plasticity-like mechanisms and so may contaminate the effects of an rTMS protocol. In the present study, we explored the effect of anesthetic on MEP amplitude, recorded before and after intermittent theta burst stimulation (iTBS), a patterned rTMS protocol with reported facilitatory effects. MEPs were assessed in the brachioradialis muscle of the upper forelimb under two anesthetics: a xylazine/zoletil combination and urethane. We found MEPs could be induced under both anesthetics, with no differences in the resting motor threshold or the average baseline amplitudes. However, MEPs were highly variable between animals under both anesthetics, with the xylazine/zoletil combination showing higher variability and most prominently a rise in amplitude across the baseline recording period. Interestingly, application of iTBS did not facilitate MEP amplitude under either anesthetic condition. Although it is important to underpin human application of TMS with mechanistic examination of effects in animals, caution must be taken when selecting an
Sykes, Matthew; Matheson, Natalie A; Brownjohn, Philip W; Tang, Alexander D; Rodger, Jennifer; Shemmell, Jonathan B H; Reynolds, John N J
Repetitive transcranial magnetic stimulation (rTMS) is primarily used in humans to change the state of corticospinal excitability. To assess the efficacy of different rTMS stimulation protocols, motor evoked potentials (MEPs) are used as a readout due to their non-invasive nature. Stimulation of the motor cortex produces a response in a targeted muscle, and the amplitude of this twitch provides an indirect measure of the current state of the cortex. When applied to the motor cortex, rTMS can alter MEP amplitude, however, results are variable between participants and across studies. In addition, the mechanisms underlying any change and its locus are poorly understood. In order to better understand these effects, MEPs have been investigated in vivo in animal models, primarily in rats. One major difference in protocols between rats and humans is the use of general anesthesia in animal experiments. Anesthetics are known to affect plasticity-like mechanisms and so may contaminate the effects of an rTMS protocol. In the present study, we explored the effect of anesthetic on MEP amplitude, recorded before and after intermittent theta burst stimulation (iTBS), a patterned rTMS protocol with reported facilitatory effects. MEPs were assessed in the brachioradialis muscle of the upper forelimb under two anesthetics: a xylazine/zoletil combination and urethane. We found MEPs could be induced under both anesthetics, with no differences in the resting motor threshold or the average baseline amplitudes. However, MEPs were highly variable between animals under both anesthetics, with the xylazine/zoletil combination showing higher variability and most prominently a rise in amplitude across the baseline recording period. Interestingly, application of iTBS did not facilitate MEP amplitude under either anesthetic condition. Although it is important to underpin human application of TMS with mechanistic examination of effects in animals, caution must be taken when selecting an
Cassidy, Jessica M.; Carey, James R.; Lu, Chiahao; Krach, Linda E.; Feyma, Tim; Durfee, William K.; Gillick, Bernadette T.
This study analyzed the relationship between electrophysiological responses to transcranial magnetic stimulation (TMS), finger tracking accuracy, and volume of neural substrate in children with congenital hemiparesis. Nineteen participants demonstrating an ipsilesional motor-evoked potential (MEP) were compared with eleven participants showing an absent ipsilesional MEP response. Comparisons of finger tracking accuracy from the affected and less affected hands and ipsilesional/contralesional (I/C) volume ratio for the primary motor cortex (M1) and posterior limb of internal capsule (PLIC) were done using two-sample t-tests. Participants showing an ipsilesional MEP response demonstrated superior tracking performance from the less affected hand (p = 0.016) and significantly higher I/C volume ratios for M1 (p= 0.028) and PLIC (p = 0.005) compared to participants without an ipsilesional MEP response. Group differences in finger tracking accuracy from the affected hand were not significant. These results highlight differentiating factors amongst children with congenital hemiparesis showing contrasting MEP responses: less affected hand performance and preserved M1 and PLIC volume. Along with MEP status, these factors pose important clinical implications in pediatric stroke rehabilitation. These findings may also reflect competitive developmental processes associated with the preservation of affected hand function at the expense of some function in the less affected hand. PMID:26426515
Lin, Sheng; Dai, Na; Cheng, Zhengyan; Shao, Wei; Fu, Zhijian
This aim of the present study was to evaluate the effects of dexmedetomidine (DEX) on the intraoperative monitoring of somatosensory-evoked potentials (SEPs) and motor-evoked potentials (MEPs) in patients undergoing spinal surgery. A total of 36 patients who received spinal surgery under general anesthesia were randomly divided into two groups (n=18 per group), group C, the test group and group D, the control group, and these groups were subjected to a matching anesthesia induction. In brief, the anesthesia was administered via injection of etomidate and fentanyl; once the patients were unconscious, a laryngeal mask airway (LMA) was inserted, SEPs and MEPs were monitored and the collected data were considered to be basic data. Cisatracurium was subsequently injected and an endotracheal tube (7#) was inserted to replace the LMA. The following procedures were conducted for anesthesia maintenance: Group C, the anesthesia was maintained via target-controlled infusion of etomidate and intermittent injection of fentanyl; and group D, DEX (0.5 μg/kg) was injected over a duration of 10 min and then pumped at a rate of 0.5 μg/kg/h. In the two groups, all of the other drugs used were the same and a muscle relaxant was not administered. The bispectral index was maintained between 45 and 55 during surgery, and the SEPs and MEPs were monitored continuously until the surgery was completed. No significant difference in duration and amplitude of the SEPs (P15-N20) was identified between group C and D (P>0.05). Furthermore, the MEPs were monitored in the two groups at specific durations and no significant difference was observed between the two groups (P>0.05). The SEPs and MEPs were maintained in the patients who were administered with the DEX-etomidate-fentanyl combined anesthesia during spinal surgery.
Kang, Suk Yun; Ma, Hyeo-Il
Objective The aim of this study was to investigate frontal N30 status in Parkinson’s disease (PD) and to examine the correlation between the amplitude of frontal N30 and the severity of motor deficits. Methods The frontal N30 was compared between 17 PD patients and 18 healthy volunteers. Correlations between the amplitude of frontal N30 and the Unified Parkinson’s Disease Rating Scale (UPDRS) motor score of the more severely affected side was examined. Results The mean latency of the N30 was not significantly different between patients and healthy volunteers (p = 0.981), but the mean amplitude was lower in PD patients (p < 0.025). There was a significant negative correlation between the amplitude of N30 and the UPDRS motor score (r = -0.715, p = 0.013). Conclusions The frontal N30 status indicates the motor severity of PD. It can be a useful biomarker reflecting dopaminergic deficits and an objective measurement for monitoring the clinical severity of PD. PMID:26828214
Behrendt, Frank; de Lussanet, Marc H. E.; Zentgraf, Karen; Zschorlich, Volker R.
Facilitation of the primary motor cortex (M1) during the mere observation of an action is highly congruent with the observed action itself. This congruency comprises several features of the executed action such as somatotopy and temporal coding. Studies using reach-grasp-lift paradigms showed that the muscle-specific facilitation of the observer’s motor system reflects the degree of grip force exerted in an observed hand action. The weight judgment of a lifted object during action observation is an easy task which is the case for hand actions as well as for lifting boxes from the ground. Here we investigated whether the cortical representation in M1 for lumbar back muscles is modulated due to the observation of a whole-body lifting movement as it was shown for hand action. We used transcranial magnetic stimulation (TMS) to measure the corticospinal excitability of the m. erector spinae (ES) while subjects visually observed the recorded sequences of a person lifting boxes of different weights from the floor. Consistent with the results regarding hand action the present study reveals a differential modulation of corticospinal excitability despite the relatively small M1 representation of the back also for lifting actions that mainly involve the lower back musculature. PMID:27336751
Doeltgen, Sebastian H; Ridding, Michael C; O'Beirne, Greg A; Dalrymple-Alford, John; Huckabee, Maggie-Lee
Motor evoked potentials (MEPs) recorded from pharyngeal and anterior hyo-mandibular (submental) muscles at rest have been used to evaluate treatment effects on neural pathways underlying swallowing. This study documents a novel methodological approach of recording reliable intra- and inter-session MEPs at the submental muscle group during task-related volitional swallowing. MEPs were elicited by single-pulse transcranial magnetic stimulation (TMS), triggered by a custom-made system when a pre-set level of surface electromyographic activity in the target muscles was breached. Fifteen MEPs were recorded during each of four sessions. Intraclass correlation coefficients (ICCs) were used to assess test-retest reliability within and across sessions for blocks of 3, 5, 10 and 15 trials. Highly reliable intra-session reliability was achieved, maximal for blocks of five trials (0.915). Inter-session reliability varied between 0.474 (three trials per block) and 0.909 (10 trials per block). Surface electromyography-triggered TMS allows reliable measurement of MEP amplitude at the submental muscle group within and across sessions when muscles are pre-activated during volitional swallowing. This methodology will be useful for future investigations on the effects of pathology and modulation of swallowing neural pathways.
de Tommaso, Marina; Brighina, Filippo; Fierro, Brigida; Francesco, Vito Devito; Santostasi, Roberto; Sciruicchio, Vittorio; Vecchio, Eleonora; Serpino, Claudia; Lamberti, Paolo; Livrea, Paolo
The aim of this study was to examine the effects of high-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) of the left primary motor cortex (M1) on subjective pain and evoked responses induced by laser stimulation (LEPs) of the contralateral hand and supraorbital zone in a cohort of migraine patients without aura during the inter-critical phase, and to compare the effects with those of non-migraine healthy controls. Thirteen migraine patients and 12 sex- and age-matched controls were evaluated. Each rTMS session consisted of 1,800 stimuli at a frequency of 5 Hz and 90% motor threshold intensity. Sham (control) rTMS was performed at the same stimulation position. The vertex LEP amplitude was reduced at the trigeminal and hand levels in the sham-placebo condition and after rTMS to a greater extent in the migraine patients than in healthy controls, while the laser pain rating was unaffected. These results suggest that HF rTMS of motor cortex and the sham procedure can both modulate pain-related evoked responses in migraine patients.
Clark, Aaron J.; Safaee, Michael; Chou, Dean; Weinstein, Philip R.; Molinaro, Annette M.; Clark, John P.; Mummaneni, Praveen V.
Study Design Retrospective review. Objective Intraoperative motor evoked potential (MEP) monitoring in spine surgery may assist surgeons in taking corrective measures to prevent neurologic deficits. The efficacy of monitoring MEPs intraoperatively in patients with myelopathy from nondegenerative causes has not been quantified. We compared the sensitivity and specificity of intraoperative MEP monitoring in patients with myelopathy caused by nondegenerative processes to patients with degenerative cervicothoracic spondylotic myelopathy (CSM). Methods We retrospectively reviewed our myelopathy surgical cases during a 1-year period to identify patients with degenerative CSM and CSM of nondegenerative causes and collected data on intraoperative MEP changes and postoperative new deficits. Categorical variables were analyzed by Fisher exact test. Receiver operator curves assessed intraoperative MEP monitoring performance in the two groups. Results In all, 144 patients were identified: 102 had degenerative CSM and 42 had CSM of nondegenerative causes (24 extra-axial tumors, 12 infectious processes, 5 traumatic fractures, and 1 rheumatoid arthritis). For degenerative CSM, there were 11 intraoperative MEP alerts and 7 new deficits (p < 0.001). The corresponding sensitivity was 71% and the specificity was 94%. In the nondegenerative group, there were 11 intraoperative MEP alerts and 3 deficits, which was not significant (p > 0.99). The sensitivity (33%) and specificity (74%) were lower. Among patients with degenerative CSM, the model performed well for predicting postoperative deficits (area under the curve [AUC] 0.826), which appeared better than the nondegenerative group, although it did not reach statistical significance (AUC 0.538, p = 0.16). Conclusions Based on this large retrospective analysis, intraoperative MEP monitoring in surgery for nondegenerative CSM cases appears to be less sensitive to cord injury and less predictive of postoperative
Ulkatan, Sedat; Jaramillo, Ana Maria; Téllez, Maria J; Kim, Jinu; Deletis, Vedran; Seidel, Kathleen
OBJECTIVE The purpose of this study was to investigate the incidence of seizures during the intraoperative monitoring of motor evoked potentials (MEPs) elicited by electrical brain stimulation in a wide spectrum of surgeries such as those of the orthopedic spine, spinal cord, and peripheral nerves, interventional radiology procedures, and craniotomies for supra- and infratentorial tumors and vascular lesions. METHODS The authors retrospectively analyzed data from 4179 consecutive patients who underwent surgery or an interventional radiology procedure with MEP monitoring. RESULTS Of 4179 patients, only 32 (0.8%) had 1 or more intraoperative seizures. The incidence of seizures in cranial procedures, including craniotomies and interventional neuroradiology, was 1.8%. In craniotomies in which transcranial electrical stimulation (TES) was applied to elicit MEPs, the incidence of seizures was 0.7% (6/850). When direct cortical stimulation was additionally applied, the incidence of seizures increased to 5.4% (23/422). Patients undergoing craniotomies for the excision of extraaxial brain tumors, particularly meningiomas (15 patients), exhibited the highest risk of developing an intraoperative seizure (16 patients). The incidence of seizures in orthopedic spine surgeries was 0.2% (3/1664). None of the patients who underwent surgery for conditions of the spinal cord, neck, or peripheral nerves or who underwent cranial or noncranial interventional radiology procedures had intraoperative seizures elicited by TES during MEP monitoring. CONCLUSIONS In this largest such study to date, the authors report the incidence of intraoperative seizures in patients who underwent MEP monitoring during a wide spectrum of surgeries such as those of the orthopedic spine, spinal cord, and peripheral nerves, interventional radiology procedures, and craniotomies for supra- and infratentorial tumors and vascular lesions. The low incidence of seizures induced by electrical brain stimulation
Thirumala, Parthasarathy D; Crammond, Donald J; Loke, Yoon K; Cheng, Hannah L; Huang, Jessie; Balzer, Jeffrey R
OBJECTIVE The goal of this study was to evaluate the efficacy of intraoperative transcranial motor evoked potential (TcMEP) monitoring in predicting an impending neurological deficit during corrective spinal surgery for patients with idiopathic scoliosis (IS). METHODS The authors searched the PubMed and Web of Science database for relevant lists of retrieved reports and/or experiments published from January 1950 through October 2014 for studies on TcMEP monitoring use during IS surgery. The primary analysis of this review fit the operating characteristic into a hierarchical summary receiver operating characteristic curve model to determine the efficacy of intraoperative TcMEP-predicted change. RESULTS Twelve studies, with a total of 2102 patients with IS were included. Analysis found an observed incidence of neurological deficits of 1.38% (29/2102) in the sample population. Of the patients who sustained a neurological deficit, 82.8% (24/29) also had irreversible TcMEP change, whereas 17.2% (5/29) did not. The pooled analysis using the bivariate model showed TcMEP change with sensitivity (mean 91% [95% CI 34%-100%]) and specificity (mean 96% [95% CI 92-98%]). The diagnostic odds ratio indicated that it is 250 times more likely to observe significant TcMEP changes in patients who experience a new-onset motor deficit immediately after IS correction surgery (95% CI 11-5767). TcMEP monitoring showed high discriminant ability with an area under the curve of 0.98. CONCLUSIONS A patient with a new neurological deficit resulting from IS surgery was 250 times more likely to have changes in TcMEPs than a patient without new deficit. The authors' findings from 2102 operations in patients with IS show that TcMEP monitoring is a highly sensitive and specific test for detecting new spinal cord injuries in patients undergoing corrective spinal surgery for IS. They could not assess the value of TcMEP monitoring as a therapeutic adjunct owing to the limited data available and their
Kraft, George H
Before the development of magnetic resonance imaging (MRI), evoked potentials (EPs)-visual evoked potentials, somatosensory evoked potentials, and brain stem auditory evoked responses-were commonly used to determine a second site of disease in patients being evaluated for possible multiple sclerosis (MS). The identification of an area of the central nervous system showing abnormal conduction was used to supplement the abnormal signs identified on the physical examination-thus identifying the "multiple" in MS. This article is a brief overview of additional ways in which central nervous system (CNS) physiology-as measured by EPs-can still contribute value in the management of MS in the era of MRIs.
Chen, Wen-Xiong; Wong, Virginia
The management of neonatal hyperbilirubinemia is very standardized. However, there is a lack of an objective method to evaluate the cerebral effects of bilirubin apart from brainstem auditory evoked potentials. There were few studies evaluating the effects of hyperbilirubinemia or phototherapy on the visual pathway in infants with hyperbilirubinemia. Serial visual evoked potentials of two groups of term neonates (N = 24)--group 1 with moderate hyperbilirubinemia (n = 16) and group 2 with severe hyperbilirubinemia (n = 8)--were evaluated prospectively. All infants had regular physical, neurologic, visual, and auditory evaluations until 3 years. Four (16%) had abnormal visual evoked potentials before 1 year, and the abnormalities returned to normal thereafter. There was no significant difference in visual evoked potentials between the two groups. All had normal neurodevelopmental status by 3 years, with the exception of one child from the severe group with ABO incompatibility with transient mild motor delay, hypotonia, and abnormal visual evoked potential. There were no abnormal effects of phototherapy on visual evoked potentials in infants with neonatal hyperbilirubinemia after 1 year of age. Although our sample size was small, the results suggest that the effects of hyperbilirubinemia on visual evoked potentials might be transient. (J Child Neurol 2006;21:58-62).
Amantini, A; Amadori, A; Fossi, S
The most informative neurophysiological techniques available in the neurosurgical intensive care unit are electroencephalograph and somatosensory evoked potentials. Such tools, which give an evaluation of cerebral function in comatose patients, support clinical evaluation and are complementary to neuroimaging. They serve both diagnostic/prognostic and monitoring purposes. While for the former, discontinuous monitoring is sufficient, for the latter, to obtain increased clinical impact, continuous monitoring is necessary. To perform and interpret these examinations in the neurosurgical intensive care unit, both the technician and the neurophysiologist need specific training in the intensive care field. There is sufficient evidence to show that somatosensory evoked potentials are the best single indicator of early prognosis in traumatic and hypoxic-ischaemic coma compared to the Glasgow Coma Score, computed tomography scan and electroencephalograph. Indeed, somatosensory evoked potentials should always be combined with clinical examination to determine the prognosis of coma. Despite widespread use of somatosensory evoked potentials and their prognostic utility in acute brain injury, few studies exist on continuous somatosensory evoked potential monitoring in the intensive care unit. We carried out a pilot study of continuous electroencephalograph-somatosensory evoked potential monitoring in the neurosurgical intensive care unit (traumatic brain injury and intracranial haemorrhage, Glasgow Coma Score <9, intracranial pressure monitoring). All patients stable from a clinical and computed tomography scan point of view showed no significant somatosensory evoked potential modifications, while in the case of clinical deterioration (23%), somatosensory evoked potentials always showed significant modifications. While somatosensory evoked potentials correlated with short-term outcome, intracranial pressure showed a poor correlation. We believe neurophysiological monitoring is
Geronimo, Andrew; Kamrunnahar, Mst; Schiff, Steven J
For brain-computer interfaces (BCIs) that utilize visual cues to direct the user, the neural signals extracted by the computer are representative of ongoing processes, visual evoked responses, and voluntary modulation. We proposed to use three brain signatures for predicting success on a single trial of a BCI task. The first two features, the amplitude and phase of the pre-trial mu amplitude, were chosen as a correlate for cortical excitability. The remaining feature, related to the visually evoked response to the cue, served as a possible measure of fixation and attention to the task. Of these three features, mu rhythm amplitude over the central electrodes at the time of cue presentation and to a lesser extent the single trial visual evoked response were correlated with the success on the subsequent imagery task. Despite the potential for gating trials using these features, an offline gating simulation was limited in its ability to produce an increase in device throughput. This discrepancy highlights a distinction between the identification of predictive features, and the use of this knowledge in an online BCI. Using such a system, we cannot assume that the user will respond similarly when faced with a scenario where feedback is altered by trials that are gated on a regular basis. The results of this study suggest the possibility of using individualized, pre-task neural signatures for personalized, and asynchronous (self-paced) BCI applications, although these effects need to be quantified in a real-time adaptive scenario in a future study.
Simpao, Allan F; Janik, Luke S; Hsu, Grace; Schwartz, Alan Jay; Heuer, Gregory G; Warrington, Andrew P; Rehman, Mohamed A
Transcranial electrical motor-evoked potential (tceMEP) monitoring is used in complex intracranial and spinal surgeries to detect and prevent neurological injury. We present a case of transient, reproducible loss of tceMEPs after an infusion of levetiracetam during craniotomy and tumor resection in a child. Cessation of the infusion resulted in restoration of baseline tceMEPs. When the infusion was resumed at the end of the procedure, a similar decrease in tceMEPs was seen as before, after the infusion was stopped. The surgery and postoperative course proceeded without incident, and the patient experienced a full recovery.
Geronimo, Andrew; Kamrunnahar, Mst; Schiff, Steven J.
For brain-computer interfaces (BCIs) that utilize visual cues to direct the user, the neural signals extracted by the computer are representative of ongoing processes, visual evoked responses, and voluntary modulation. We proposed to use three brain signatures for predicting success on a single trial of a BCI task. The first two features, the amplitude and phase of the pre-trial mu amplitude, were chosen as a correlate for cortical excitability. The remaining feature, related to the visually evoked response to the cue, served as a possible measure of fixation and attention to the task. Of these three features, mu rhythm amplitude over the central electrodes at the time of cue presentation and to a lesser extent the single trial visual evoked response were correlated with the success on the subsequent imagery task. Despite the potential for gating trials using these features, an offline gating simulation was limited in its ability to produce an increase in device throughput. This discrepancy highlights a distinction between the identification of predictive features, and the use of this knowledge in an online BCI. Using such a system, we cannot assume that the user will respond similarly when faced with a scenario where feedback is altered by trials that are gated on a regular basis. The results of this study suggest the possibility of using individualized, pre-task neural signatures for personalized, and asynchronous (self-paced) BCI applications, although these effects need to be quantified in a real-time adaptive scenario in a future study. PMID:27199630
Tanaka, Satoshi; Hirao, Jun; Oka, Hidehiro; Akimoto, Jiro; Takanashi, Junko; Yamada, Junichi
Motor-evoked potential (MEP) monitoring was performed during 196 consecutive spinal (79 cervical and 117 lumbar) surgeries for the decompression of compressive spinal and spinal nerve diseases. MEP monitoring in spinal surgery has been considered sensitive to predict postoperative neurological recovery. In this series, transcranial stimulation consisted of trains of five pulses at a constant voltage (200-600 V). For the normalization of MEP, we recorded compound muscle action potentials (CMAP) after peripheral nerve stimulation, usually on the median nerve at the wrist 2 seconds before or after each transcranial stimulation of the motor area, for all operations. The sensitivity and specificity of MEP monitoring was 100% and 97.4%, respectively, or 96.9% with or without CMAP compensation (if the threshold of postoperative motor palsy was defined as 20% relative amplitude rate [RAR]). The mean RAR after CMAP normalization, of the most affected muscle in the patient group with excellent postoperative results (recovery rate of a Japan Orthopedic Association score of more than 50%) was significantly higher than that in the other groups (p=0.0224). All patients with an amplitude increase rate (AIR) with CMAP normalization of more than 20% achieved neurological recovery postoperatively. Our results suggest that if the RAR is more than 20%, postoperative motor palsy can be avoided in spinal surgery. If the AIR with normalization by CMAP after peripheral nerve stimulation is more than 20%, neurological recovery can be expected in spinal surgery.
Kim, Dong-Gun; Choi, Young-Doo; Jin, Seung-Hyun; Kim, Chi Heon; Lee, Kwang-Woo; Park, Kyung Seok
Background and Purpose We studied the clinical significance of amplitude-reduction and disappearance alarm criteria for transcranial electric muscle motor-evoked potentials (MEPs) during cervical spinal surgery according to different lesion locations [intramedullary (IM) vs. nonintramedullary (NIM)] by evaluating the long-term postoperative motor status. Methods In total, 723 patients were retrospectively dichotomized into the IM and NIM groups. Each limb was analyzed respectively. One hundred and sixteen limbs from 30 patients with IM tumors and 2,761 limbs from 693 patients without IM tumors were enrolled. Postoperative motor deficits were assessed up to 6 months after surgery. Results At the end of surgery, 61 limbs (2.2%) in the NIM group and 14 limbs (12.1%) in the IM group showed MEP amplitudes that had decreased to below 50% of baseline, with 13 of the NIM limbs (21.3%) and 2 of the IM limbs (14.3%) showing MEP disappearance. Thirteen NIM limbs (0.5%) and 5 IM limbs (4.3%) showed postoperative motor deficits. The criterion for disappearance showed a lower sensitivity for the immediate motor deficit than did the criterion for amplitude decrement in both the IM and NIM groups. However, the disappearance criterion showed the same sensitivity as the 70%-decrement criterion in IM (100%) and NIM (83%) surgeries for the motor deficit at 6 months after surgery. Moreover, it has the highest specificity for the motor deficits among diverse alarm criteria, from 24 hours to 6 months after surgery, in both the IM and NIM groups. Conclusions The MEP disappearance alarm criterion had a high specificity in predicting the long-term prognosis after cervical spinal surgery. However, because it can have a low sensitivity in predicting an immediate postoperative deficit, combining different MEP alarm criteria according to the aim of specific instances of cervical spinal surgery is likely to be useful in practical intraoperative monitoring. PMID:27730765
Shiiya, Norihiko; Takahashi, Daisuke; Tsuda, Kazumasa
Somatosensory evoked potential (SSEP), evoked spinal cord potential (ESCP) and motor evoked potential (MEP) have been used to detect spinal cord ischemia during aortic surgery. SSEP evaluates the sensory pathway, and is recorded from the sensory cortex by peripheral nerve stimulation. The interval from the onset of ischemia to change is relatively long(5-10 minutes). It has less frequently been used because of the high false negative and false positive rate. ESCP is recorded from the spinal cord by direct stimulation of the cord. It reflects the function of spinal tract but not that of alpha motor neurons. It is resistant to anesthesia and both the sensitivity and specificity is high, but the interval from ischemia to change is relatively long. Together with the necessity of 2 epidural electrodes, its application in aortic surgery has become infrequent. Since the introduction of train pulse transcranial electrical stimulation, myogenic MEP have gained widespread acceptance. It evaluates motor pathways from the cortex to the muscle, and therefore is influenced by non-spinal factors such as peripheral nerve ischemia. Its vulnerability to anesthesia requires special anesthetic consideration, and baseline amplitude fluctuation is common. It is highly sensitive and shows changes in the early phase of spinal cord ischemia.
Xu, Risheng; Ritzl, Eva K.; Sait, Mohammed; Sciubba, Daniel M.; Wolinsky, Jean-Paul; Witham, Timothy F.; Gokaslan, Ziya L.; Bydon, Ali
Background: Although the usage of combined motor and sensory intraoperative monitoring has been shown to improve the surgical outcome of patients with cervical myelopathy, the role of transcranial electric motor evoked potentials (tceMEP) used in conjunction with somatosensory evoked potentials (SSEP) in patients presenting with radiculopathy but without myelopathy has been less clear. Methods: We retrospectively reviewed all patients (n = 57) with radiculopathy but without myelopathy, undergoing anterior cervical decompression and fusion at a single institution over the past 3 years, who had intraoperative monitoring with both tceMEPs and SSEPs. Results: Fifty-seven (100%) patients presented with radiculopathy, 53 (93.0%) with mechanical neck pain, 35 (61.4%) with motor dysfunction, and 29 (50.9%) with sensory deficits. Intraoperatively, 3 (5.3%) patients experienced decreases in SSEP signal amplitudes and 4 (6.9%) had tceMEP signal changes. There were three instances where a change in neuromonitoring signal required intraoperative alteration of the surgical procedure: these were deemed clinically significant events/true positives. SSEP monitoring showed two false positives and two false negatives, whereas tceMEP monitoring only had one false positive and no false negatives. Thus, tceMEP monitoring exhibited higher sensitivity (33.3% vs. 100%), specificity (95.6% vs. 98.1%), positive predictive value (33.3% vs. 75.0%), negative predictive value (97.7% vs. 100%), and efficiency (91.7% vs. 98.2%) compared to SSEP monitoring alone. Conclusions: Here, we present a retrospective series of 57 patients where tceMEP/SSEP monitoring likely prevented irreversible neurologic damage. Though further prospective studies are needed, there may be a role for combined tceMEP/SSEP monitoring for patients undergoing anterior cervical decompression without myelopathy. PMID:22059128
Tomio, Ryosuke; Akiyama, Takenori; Ohira, Takayuki; Yoshida, Kazunari
Background: Intraoperative monitoring of motor evoked potentials by transcranial electric stimulation is popular in neurosurgery for monitoring motor function preservation. Some authors have reported that the peg-screw electrodes screwed into the skull can more effectively conduct current to the brain compared to subdermal cork-screw electrodes screwed into the skin. The aim of this study was to investigate the influence of electrode design on transcranial motor evoked potential monitoring. We estimated differences in effectiveness between the cork-screw electrode, peg-screw electrode, and cortical electrode to produce electric fields in the brain. Methods: We used the finite element method to visualize electric fields in the brain generated by transcranial electric stimulation using realistic three-dimensional head models developed from T1-weighted images. Surfaces from five layers of the head were separated as accurately as possible. We created the “cork-screws model,” “1 peg-screw model,” “peg-screws model,” and “cortical electrode model”. Results: Electric fields in the brain radially diffused from the brain surface at a maximum just below the electrodes in coronal sections. The coronal sections and surface views of the brain showed higher electric field distributions under the peg-screw compared to the cork-screw. An extremely high electric field was observed under cortical electrodes. Conclusion: Our main finding was that the intensity of electric fields in the brain are higher in the peg-screw model than the cork-screw model. PMID:27920938
Vecchio, Eleonora; Ricci, Katia; Montemurno, Anna; Delussi, Marianna; Invitto, Sara; de Tommaso, Marina
Migraine is characterized by an altered cortical excitability. Because transcranial direct current stimulation (tDCS) can change brain activity noninvasively, it is possible to hypothesize its efficacy in modulating pain in migraine. In this study, we compared the effects of tDCS of the left primary motor cortex (M1) and left dorsolateral prefrontal cortex (DLPFC) both on subjective pain and on evoked responses induced by laser stimulation (LEPs). Thirty-two patients and sixteen controls were randomized to receive sham stimulation and real tDCS with the anode centered over M1 or DLPFC. Laser Evoked potentials were recorded in basal, sham and tDCS conditions. We did not find significant acute changes in LEPs parameters and pain perception among subjects who received tDCS of both M1 and DLPFC. After DLPFC tDCS, we observed a significant increase of N2-P2 component habituation in migraine patients while M1 stimulation reduced it. These findings may suggest a modulation of abnormal pain processing induced by DLPFC and M1 anodal tDCS and outline the need for future investigations exploring the possible neuronal plasticity changes supporting the clinical effect on migraine.
ARI Research Note 88-69 0 MitnS.Ktohe U.0 ... Ann-r (. Time Perception and Evoked Potentials Paul FraisseDT ( Lfniversit6 Rene Descartes E LECTE...JOHNSON 00L, [N Technical Dicctojr Cmad Research accomplished under contract for the Department of the Army C. Universite Rene Descartes , Paris )r...ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK Labrato-ire de Psychologie Experimental AREA• WORK UNIT NUMBERS Universite Rene Descartes
Iscan, Zafer; Nazarova, Maria; Fedele, Tommaso; Blagovechtchenski, Evgeny; Nikulin, Vadim V
Inter- and intra-subject variability of the motor evoked potentials (MEPs) to TMS is a well-known phenomenon. Although a possible link between this variability and ongoing brain oscillations was demonstrated, the results of the studies are not consistent with each other. Exploring this topic further is important since the modulation of MEPs provides unique possibility to relate oscillatory cortical phenomena to the state of the motor cortex probed with TMS. Given that alpha oscillations were shown to reflect cortical excitability, we hypothesized that their power and variability might explain the modulation of subject-specific MEPs to single- and paired-pulse TMS (spTMS, ppTMS, respectively). Neuronal activity was recorded with multichannel electroencephalogram. We used spTMS and two ppTMS conditions: intracortical facilitation (ICF) and short-interval intracortical inhibition (SICI). Spearman correlations were calculated within and across subjects between MEPs and the pre-stimulus power of alpha oscillations in low (8-10 Hz) and high (10-12 Hz) frequency bands. Coefficient of quartile variation was used to measure variability. Across-subject analysis revealed no difference in the pre-stimulus alpha power among the TMS conditions. However, the variability of high-alpha power in spTMS condition was larger than in the SICI condition. In ICF condition pre-stimulus high-alpha power variability correlated positively with MEP amplitude variability. No correlation has been observed between the pre-stimulus alpha power and MEP responses in any of the conditions. Our results show that the variability of the alpha oscillations can be more predictive of TMS effects than the commonly used power of oscillations and we provide further support for the dissociation of high and low-alpha bands in predicting responses produced by the stimulation of the motor cortex.
Iscan, Zafer; Nazarova, Maria; Fedele, Tommaso; Blagovechtchenski, Evgeny; Nikulin, Vadim V.
Inter- and intra-subject variability of the motor evoked potentials (MEPs) to TMS is a well-known phenomenon. Although a possible link between this variability and ongoing brain oscillations was demonstrated, the results of the studies are not consistent with each other. Exploring this topic further is important since the modulation of MEPs provides unique possibility to relate oscillatory cortical phenomena to the state of the motor cortex probed with TMS. Given that alpha oscillations were shown to reflect cortical excitability, we hypothesized that their power and variability might explain the modulation of subject-specific MEPs to single- and paired-pulse TMS (spTMS, ppTMS, respectively). Neuronal activity was recorded with multichannel electroencephalogram. We used spTMS and two ppTMS conditions: intracortical facilitation (ICF) and short-interval intracortical inhibition (SICI). Spearman correlations were calculated within and across subjects between MEPs and the pre-stimulus power of alpha oscillations in low (8–10 Hz) and high (10–12 Hz) frequency bands. Coefficient of quartile variation was used to measure variability. Across-subject analysis revealed no difference in the pre-stimulus alpha power among the TMS conditions. However, the variability of high-alpha power in spTMS condition was larger than in the SICI condition. In ICF condition pre-stimulus high-alpha power variability correlated positively with MEP amplitude variability. No correlation has been observed between the pre-stimulus alpha power and MEP responses in any of the conditions. Our results show that the variability of the alpha oscillations can be more predictive of TMS effects than the commonly used power of oscillations and we provide further support for the dissociation of high and low-alpha bands in predicting responses produced by the stimulation of the motor cortex. PMID:27774060
Deguchi, Tsuyoshi; Tsutsui, Shunji; Iwahashi, Hiroki; Nakagawa, Yukihiro; Yoshida, Munehito
Recently, low-frequency multi-train stimulation (MTS) was shown to effectively enhance transcranial motor-evoked potentials (TcMEPs). In contrast, high- frequency double-train stimulation was reported to elicit a marked facilitation. The aim of this study was to evaluate the efficacy of high-frequency MTS in the augmentation of potentials. In addition, we investigated the safety of high-frequency MTS, behaviorally and histologically. TcMEPs were recorded from the triceps surae muscle in 38 rats. A multipulse stimulus was delivered repeatedly at different rates (2, 5, 10, 20, and 50 Hz), and was defined as MTS. A conditioned taste aversion method was used to investigate the effect of high-frequency MTS on learning and memory function. Subsequently, animals were sacrificed, and the brains were removed and examined using the standard hematoxylin-eosin method. Compared with conventional single train stimulation, TcMEP amplitudes increased 1.3, 2.1, 1.9, and 2.0 times on average with 5, 10, 20, and 50 Hz stimulation, respectively. The aversion index was >0.8 in all animals after they received 100 high-frequency MTSs. Histologically, no pathological changes were evident in the rat brains. High-frequency MTS shows potential to effectively enhance TcMEP responses, and to be used safely in transcranial brain stimulation.
Anzak, Anam; Tan, Huiling; Pogosyan, Alek; Khan, Sadaquate; Javed, Shazia; Gill, Steven S; Ashkan, Keyoumars; Akram, Harith; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Green, Alexander L; Aziz, Tipu; Brown, Peter
Enhancements in motor performance have been demonstrated in response to intense stimuli both in healthy subjects and in the form of 'paradoxical kinesis' in patients with Parkinson's disease. Here we identify a mid-latency evoked potential in local field potential recordings from the region of the subthalamic nucleus, which scales in amplitude with both the intensity of the stimulus delivered and corresponding enhancements in biomechanical measures of maximal handgrips, independent of the dopaminergic state of our subjects with Parkinson's disease. Recordings of a similar evoked potential in the related pedunculopontine nucleus - a key component of the reticular activating system - provide support for this neural signature in the subthalmic nucleus being a novel correlate of ascending arousal, propagated from the reticular activating system to exert an 'energizing' influence on motor circuitry. Future manipulation of this system linking arousal and motor performance may provide a novel approach for the non-dopaminergic enhancement of motor performance in patients with hypokinetic disorders such as Parkinson's disease.
Anzak, Anam; Tan, Huiling; Pogosyan, Alek; Khan, Sadaquate; Javed, Shazia; Gill, Steven S.; Ashkan, Keyoumars; Akram, Harith; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Green, Alexander L.; Aziz, Tipu; Brown, Peter
Enhancements in motor performance have been demonstrated in response to intense stimuli both in healthy subjects and in the form of ‘paradoxical kinesis’ in patients with Parkinson's disease. Here we identify a mid-latency evoked potential in local field potential recordings from the region of the subthalamic nucleus, which scales in amplitude with both the intensity of the stimulus delivered and corresponding enhancements in biomechanical measures of maximal handgrips, independent of the dopaminergic state of our subjects with Parkinson's disease. Recordings of a similar evoked potential in the related pedunculopontine nucleus – a key component of the reticular activating system – provide support for this neural signature in the subthalmic nucleus being a novel correlate of ascending arousal, propagated from the reticular activating system to exert an ‘energizing’ influence on motor circuitry. Future manipulation of this system linking arousal and motor performance may provide a novel approach for the non-dopaminergic enhancement of motor performance in patients with hypokinetic disorders such as Parkinson's disease. PMID:26687971
Horvath, Jared Cooney; Vogrin, Simon J; Carter, Olivia; Cook, Mark J; Forte, Jason D
Transcranial direct current stimulation (tDCS) uses a weak electric current to modulate neuronal activity. A neurophysiologic outcome measure to demonstrate reliable tDCS modulation at the group level is transcranial magnetic stimulation engendered motor evoked potentials (MEPs). Here, we conduct a study testing the reliability of individual MEP response patterns following a common tDCS protocol. Fourteen participants (7m/7f) each underwent nine randomized sessions of 1 mA, 10 min tDCS (3 anode; 3 cathode; 3 sham) delivered using an M1/orbito-frontal electrode montage (sessions separated by an average of ~5.5 days). Fifteen MEPs were obtained prior to, immediately following and in 5 min intervals for 30 min following tDCS. TMS was delivered at 130 % resting motor threshold using neuronavigation to ensure consistent coil localization. A number of non-experimental variables were collected during each session. At the individual level, considerable variability was seen among different testing sessions. No participant demonstrated an excitatory response ≥20 % to all three anodal sessions, and no participant demonstrated an inhibitory response ≥20 % to all three cathodal sessions. Intra-class correlation revealed poor anodal and cathodal test-retest reliability [anode: ICC(2,1) = 0.062; cathode: ICC(2,1) = 0.055] and moderate sham test-retest reliability [ICC(2,1) = 0.433]. Results also revealed no significant effect of tDCS at the group level. Using this common protocol, we found the effects of tDCS on MEP amplitudes to be highly variable at the individual level. In addition, no significant effects of tDCS on MEP amplitude were found at the group level. Future studies should consider utilizing a more strict experimental protocol to potentially account for intra-individual response variations.
Andrew, Danielle; Yielder, Paul; Murphy, Bernadette
Central nervous system (CNS) plasticity is essential for development; however, recent research has demonstrated its role in pathology, particularly following overuse and repetition. Previous studies investigating changes in sensorimotor integration (SMI) have used relatively simple paradigms resulting in minimal changes in neural activity, as determined through the use of somatosensory evoked potentials (SEPs). This study sought to utilize complex tasks and compare separate motor paradigms to determine which one best facilitates long-term learning. Spinal, brainstem, and cortical SEPs were recorded following median nerve stimulation at the wrist pre- and postinterventions. Eighteen participants performed the same paradigms, a control condition of 10 min of mental recitation and two interventions, one consisting of 10 min of tracing and the other 10 min of repetitive typing. Significant increases in the N13, N20, P25, and N30 SEP peaks were seen for both interventions. A significant decrease in the N24 SEP peak was observed for both interventions. Significant improvements in accuracy were seen for both interventions postacquisition but only for tracing during retention. The changes seen following motor learning were congruent with those associated with long-term learning, which was also reflected by significant increases in accuracy during retention. Tracing or the pursuit movement paradigm was shown to be a more effective learning tool. The identification of a task that is sufficiently novel and complex, leading to robust changes in SEP peaks, indicates a task that can be utilized in future work to study clinical populations and the effect of experimental interventions on SMI.
Using Transcranial Magnetic Stimulation to Evaluate the Motor Pathways After an Intraoperative Spinal Cord Injury and to Predict the Recovery of Intraoperative Transcranial Electrical Motor Evoked Potentials: A Case Report.
Grover, Helen J; Thornton, Rachel; Lutchman, Lennel N; Blake, Julian C
The authors report a case of unilateral loss of intraoperative transcranial electrical motor evoked potentials (TES MEP) associated with a spinal cord injury during scoliosis correction and the subsequent use of extraoperative transcranial magnetic stimulation to monitor the recovery of spinal cord function. The authors demonstrate the absence of TES MEPs and absent transcranial magnetic stimulation responses in the immediate postoperative period, and document the partial recovery of transcranial magnetic stimulation responses, which corresponded to partial recovery of TES MEPs. Intraoperative TES MEPs were enhanced using spatial facilitation technique, which enabled the patient to undergo further surgery to stabilize the spine and correct her scoliosis. This case report supports evidence of the use of extraoperative transcranial magnetic stimulation to predict the presence of intraoperative TES responses and demonstrates the usefulness of spatial facilitation to monitor TES MEPs in a patient with a preexisting spinal cord injury.
Świdziński, Teodor; Linkowska-Świdzińska, Kamila; Czerniejewska-Wolska, Hanna; Wiskirska-Woźnica, Bożena; Owecki, Maciej; Głowacka, Maria Danuta; Frankowska, Anna; Łącka, Katarzyna; Glapiński, Mariusz; Maciejewska-Szaniec, Zofia; Świdziński, Piotr
Background. Objective electrophysiological methods for investigations of the organ of smell consist in recordings of olfactory cortex responses to specific, time restricted odor stimuli. In hypothyroidism have impaired sense of smell. Material and Methods. Two groups: control of 31 healthy subjects and study group of 21 with hypothyroidism. The inclusion criterion for the study group was the TSH range from 3.54 to 110 μIU/mL. Aim. Assessment of the latency time of evoked responses from the olfactory nerve N1 and the trigeminal nerve N5 using two smells of mint and anise in hypothyroidism. Results. The smell perception in subjective olfactory tests was normal in 85% of the hypothyroid group. Differences were noticed in the objective tests. The detailed intergroup analysis of latency times of recorded cortical responses PN5 and PN1 performed by means between the groups of patients with overt clinical hypothyroidism versus subclinical hypothyroidism demonstrated a significant difference (p < 0.05) whereas no such differences were found between the control group versus subclinical hypothyroidism group (p > 0.05). Conclusion. We can conclude that registration of cortex potentials at irritation of olfactory and trigeminal nerves offers possibilities for using this method as an objective indicator of hypothyroidism severity and prognostic process factor.
Świdziński, Teodor; Czerniejewska-Wolska, Hanna; Wiskirska-Woźnica, Bożena; Owecki, Maciej; Głowacka, Maria Danuta; Frankowska, Anna; Łącka, Katarzyna; Glapiński, Mariusz; Maciejewska-Szaniec, Zofia; Świdziński, Piotr
Background. Objective electrophysiological methods for investigations of the organ of smell consist in recordings of olfactory cortex responses to specific, time restricted odor stimuli. In hypothyroidism have impaired sense of smell. Material and Methods. Two groups: control of 31 healthy subjects and study group of 21 with hypothyroidism. The inclusion criterion for the study group was the TSH range from 3.54 to 110 μIU/mL. Aim. Assessment of the latency time of evoked responses from the olfactory nerve N1 and the trigeminal nerve N5 using two smells of mint and anise in hypothyroidism. Results. The smell perception in subjective olfactory tests was normal in 85% of the hypothyroid group. Differences were noticed in the objective tests. The detailed intergroup analysis of latency times of recorded cortical responses PN5 and PN1 performed by means between the groups of patients with overt clinical hypothyroidism versus subclinical hypothyroidism demonstrated a significant difference (p < 0.05) whereas no such differences were found between the control group versus subclinical hypothyroidism group (p > 0.05). Conclusion. We can conclude that registration of cortex potentials at irritation of olfactory and trigeminal nerves offers possibilities for using this method as an objective indicator of hypothyroidism severity and prognostic process factor. PMID:27656655
Rossi, L; Ubiali, E; Merli, R; Rottoli, M R
The authors study the sensitive potential evoked from point of Erb and from cervical spine in C6-C7, obtained by stimulation of median nerve in a control group (normals) and in a greater group of 40 cases from patients affected by radiculopathie with or without discal protrusion and by myelopathie spondiloartrosic. The date supply significant informations and are (obicurred in analytique) analyzed with accuracy.
Visual, somatosensory, and brainstem auditory evoked potentials provide functional quantitative assessment of the cerebral cortex and brainstem. Their contribution at the acute stage of coma concerns diagnosis, prognosis, and follow-up. Four patterns are observed in traumatic coma: pattern 1=dysfunction of the cerebral cortex, brainstem integrity: good prognosis in more than 80% of cases; pattern 2=midbrain dysfunction: prognosis depends on both the reversibility of midbrain dysfunction and the extent of associated axonal lesions in the hemispheric white matter; pattern 3=pontine dysfunction due to transtentorial herniation: ominous prognosis, this pattern must be early detected by continuous monitoring; pattern 4=brain death: we currently use evoked potentials at the only brain-death confirmatory test, even in sedated patients. The contribution of evoked potentials in vegetative or minimally responsive states concerns the identification of these patients whose state is determined by midbrain dysfunction and the evaluation of persisting cognitive abilities in individual cases.
Leocani, L; Medaglini, S; Comi, G
The usefulness of evoked potentials (EPs) in the diagnosis of multiple sclerosis is limited by its relatively low sensitivity to subclinical lesions. However, they are still a good tool to assess the integrity of afferent and efferent pathways and to quantify the severity of white matter involvement. Transversal and longitudinal studies have demonstrated good correlation between EP abnormalities and disability, suggesting that multimodal evoked potentials could be useful in monitoring the disease evolution in single patients and as surrogate end points in clinical trials.
Miljković, N; Malešević, N; Kojić, V; Bijelić, G; Keller, T; Popović, D B
In order to optimize procedure for the assessment of evoked potentials and to provide visualization of the flow of action potentials along the motor systems, we introduced array electrodes for stimulation and recording and developed software for the analysis of the recordings. The system uses a stimulator connected to an electrode array for the generation of evoked potentials, an electrode array connected to the amplifier, A/D converter and computer for the recording of evoked potentials, and a dedicated software application. The method has been tested for the assessment of the H-reflex on the triceps surae muscle in six healthy humans. The electrode array with 16 pads was positioned over the posterior aspect of the thigh, while the recording electrode array with 16 pads was positioned over the triceps surae muscle. The stimulator activated all the pads of the stimulation electrode array asynchronously, while the signals were recorded continuously at all the recording sites. The results are topography maps (spatial distribution of evoked potentials) and matrices (spatial visualization of nerve excitability). The software allows the automatic selection of the lowest stimulation intensity to achieve maximal H-reflex amplitude and selection of the recording/stimulation pads according to predefined criteria. The analysis of results shows that the method provides rich information compared with the conventional recording of the H-reflex with regard the spatial distribution.
Urumova, L T; Kovalenko, G A; Tsunikov, A I; Sumskiĭ, L I
The article reports on the first study of the evoked activity of the brain in epileptic patients (n = 20) following sleep deprivation. An analysis of the data obtained has revealed a tendency to the shortening of the peak latent intervals of visual evoked potentials in the range of 100-200 mu sec and the V component and the interpeak interval III-V of evoked auditory trunk potentials in patients with temporal epilepsy. The phenomenon may indicate the elimination of stabilizing control involving the specific conductive pathways and, possibly, an accelerated conduction of a specific sensor signal.
Barr, Melodie S; Hamm, Jeff P; Kirk, Ian J; Corballis, Michael C
Three participants with callosal agenesis and 12 neurologically normal participants were tested on a simple reaction time task, with visual evoked potentials collected using a high-density 128-channel system. Independent-components analyses were performed on the averaged visual evoked potentials to isolate the components of interest. Contrary to previous research with acallosals, evidence of ipsilateral activation was present in all 3 participants. Although ipsilateral visual components were present in all 4 unilateral conditions in the 2 related acallosal participants, in the 3rd, these were present only in the crossed visual field-hand conditions and not in the uncrossed conditions. Suggestions are made as to why these results differ from earlier findings and as to the neural mechanisms facilitating this ipsilateral activation.
Heinrich, Sven P
Motion visual evoked potentials (motion VEPs) have been used since the late 1960s to investigate the properties of human visual motion processing, and continue to be a popular tool with a possible future in clinical diagnosis. This review first provides a synopsis of the characteristics of motion VEPs and then summarizes important methodological aspects. A subsequent overview illustrates how motion VEPs have been applied to study basic functions of human motion processing and shows perspectives for their use as a diagnostic tool.
Gilinskiy, M. A.; Korsakov, I. A.
Averaged evoked potentials in the auditory, somatosensory, and motor cortical zones, as well as in the mesencephalic reticular formation were recorded in acute experiments on nonanesthetized, immobilized cats. Omission of the painful stimulus after a number of pairings resulted in the appearance of a delayed evoked potential, often resembling the late phases of the response to the painful stimulus. The characteristics of this response are discussed in comparison with conditioned changes of the sensory potential amplitudes.
Chen, I-An; Hung, Steven Wu; Chen, Yu-Hsien; Lim, Siew-Na; Tsai, Yu-Tai; Hsiao, Cheng-Lun; Hsieh, Hsiang-Yao; Wu, Tony
Laser-evoked potentials are widely used to investigate nociceptive pathways. The newly developed contact heat stimulator for evoking brain response has the advantages of obtaining reliable scalp potentials and absence of cutaneous lesions. This study aimed to identify the most appropriate stimulation site with consistent cortical responses, and to correlate several parameters of the contact heat evoked potentials (CHEPs) with age, gender, and body height in normal subjects. CHEPs were recorded at Cz with a contact heat stimulator (Medoc, Israel) in 35 normal controls. The subjects were asked to keep eyes open and remain alert. The baseline temperature was 32 degrees C, and stimulation peak heat intensity of 51 degrees C was applied to five body sites: bilateral forearm, right dorsum hand, right peroneal area, and right dorsum foot. Reproducible CHEPs were recorded more frequently when stimulated at volar forearm (62.5%) than at the lower limbs (around 40%). The first negative peak latency (N1) was 370.1 +/- 20.3 ms, first positive peak latency (P1) was 502.4 +/- 33.0 ms, and peak to peak amplitude was 10.2 +/- 4.9 microV with stimulation of the forearm. Perceived pain intensity was not correlated with the presence or amplitude of CHEPs. No gender or inter-side differences were observed for N1 latency and N1-P1 amplitude. Also, no correlation was noted between N1 and age or body height. These results support future clinical access of CHEPs as a diagnostic tool.
Gurtubay, I G
The techniques of cognitive evoked potentials are considered long and technically complex, which is why their use in clinical practice is not very widespread in spite of their potential utility. Recent advances in registering and analysis, together with improvement of the software managing these signals, have appreciably reduced these problems. Mismatch negativity stands out as the most promising of all the cognitive potentials due to its special characteristics regarding its generation requisites and its proven clinical utility. The fact that it can be generated without care requirements makes it especially useful for evaluating subjects with a low level of consciousness; it serves for predicting when they will emerge from a coma, amongst other uses. The incorporation of this technique into the arsenal of neurophysiological techniques for evaluating the state of these subjects will bring a substantial improvement in the evaluation of cases whose management in clinical practice is extremely complex.
Telles, Shirley; Deepeshwar, Singh; Naveen, Kalkuni Visweswaraiah; Pailoor, Subramanya
The auditory sensory pathway has been studied in meditators, using midlatency and short latency auditory evoked potentials. The present study evaluated long latency auditory evoked potentials (LLAEPs) during meditation. Sixty male participants, aged between 18 and 31 years (group mean±SD, 20.5±3.8 years), were assessed in 4 mental states based on descriptions in the traditional texts. They were (a) random thinking, (b) nonmeditative focusing, (c) meditative focusing, and (d) meditation. The order of the sessions was randomly assigned. The LLAEP components studied were P1 (40-60 ms), N1 (75-115 ms), P2 (120-180 ms), and N2 (180-280 ms). For each component, the peak amplitude and peak latency were measured from the prestimulus baseline. There was significant decrease in the peak latency of the P2 component during and after meditation (P<.001; analysis of variance and post hoc analysis with Bonferroni adjustment). The P1, P2, and N2 components showed a significant decrease in peak amplitudes during random thinking (P<.01; P<.001; P<.01, respectively) and nonmeditative focused thinking (P<.01; P<.01; P<.05, respectively). The results suggest that meditation facilitates the processing of information in the auditory association cortex, whereas the number of neurons recruited was smaller in random thinking and non-meditative focused thinking, at the level of the secondary auditory cortex, auditory association cortex and anterior cingulate cortex.
Night vision goggles (NVG's) have widespread use in military and civilian environments. NVG's amplify ambient illumination making performance possible when there is insufficient illumination for normal vision. While visual performance through NVG's is commonly assessed by measuring threshold functions such as visual acuity, few attempts have been made to assess vision through NVG's at suprathreshold levels of stimulation. Such information would be useful to better understand vision through NVG's across a range of stimulus conditions. In this study visual evoked potentials (VEP's) were used to evaluate vision through NVG's across a range of stimulus contrasts. The amplitude and latency of the VEP varied linearly with log contrast. A comparison of VEP's recorded with and without NVG's was used to estimate contrast attenuation through the device. VEP's offer an objective, electrophysiological tool to assess visual performance through NVG's at both threshold and suprathreshold levels of visual stimulation.
Fiuza Regaçone, Simone; Baptista de Lima, Daiane Damaris; Engrácia Valenti, Vitor; Figueiredo Frizzo, Ana Cláudia
The objective of this study was to evaluate the association between rest heart rate (HR) and the components of the auditory evoked-related potentials (ERPs) at rest in women. We investigated 21 healthy female university students between 18 and 24 years old. We performed complete audiological evaluation and measurement of heart rate for 10 minutes at rest (heart rate monitor Polar RS800CX) and performed ERPs analysis (discrepancy in frequency and duration). There was a moderate negative correlation of the N1 and P3a with rest HR and a strong positive correlation of the P2 and N2 components with rest HR. Larger components of the ERP are associated with higher rest HR. PMID:26504838
Loring, D W; Levin, H S; Papanicolaou, A C; Larrabee, G J; Eisenberg, H M
Two evoked potential (EP) techniques and the selective reminding test were employed to investigate an apparently benign forgetfulness in seven elderly subjects and seven age-matched elderly subjects with normal memory. EPs were also recorded in a group of seven young adults. Latency of the P3 component, which has been demonstrated to increase in primary degenerative dementia, displayed the normal age-related variation in both elderly groups, but did not differ between the forgetful subjects and the elderly controls. Further, no difference in the recovery cycle of the EP, as measured in a two tone stimulation paradigm, was present between forgetful and elderly control groups. Reexamination of memory after nearly a year disclosed no evidence of deterioration in either elderly group. These findings suggest that senescent forgetfulness, as defined herein, may be a nonprogressive memory disorder.
Tandon, O P; Kumar, V
Pattern reversal visual evoked potentials (pVEP) were studied in 39 male rubber factory workers in the age range of 18-55 years and 20 control subjects (aged 18-46 years) not exposed to the rubber factory environment. Results revealed that 20 (51%) rubber factory workers had abnormal latencies of wave P1 (dominant component of pVEP) as per accepted criteria of 99% tolerance limit set for the control group (i.e. any value above mean +3 SD of control was considered abnormal). The section-wise per cent distribution of abnormalities was vulcanization (83%), tubing (75%), calendering (60%), loading (38%) and mixing (14%). This study provides electrophysiological evidence that rubber factory environments affect the conduction processes in optical pathways from their origin in the retina to striate cortex. However, this study has its limitations in not identifying the specific chemical(s) causing these changes in VEP.
Kirimoto, Hikari; Asao, Akihiko; Tamaki, Hiroyuki; Onishi, Hideaki
This study was performed to investigate the possibility of non-invasive modulation of SEPs by the application of transcranial static magnetic field stimulation (tSMS) over the primary motor cortex (M1) and supplementary motor cortex (SMA), and to measure the strength of the NdFeB magnetic field by using a gaussmeter. An NdFeB magnet or a non-magnetic stainless steel cylinder (for sham stimulation) was settled on the scalp over M1 and SMA of 14 subjects for periods of 15 min. SEPs following right median nerve stimulation were recorded before and immediately after, 5 min after, and 10 min after tSMS from sites C3′ and F3. Amplitudes of the N33 component of SEPs at C3′ significantly decreased immediately after tSMS over M1 by up to 20%. However, tSMS over the SMA did not affect the amplitude of any of the SEP components. At a distance of 2–3 cm (rough depth of the cortex), magnetic field strength was in the range of 110–190 mT. Our results that tSMS over M1 can reduce the amplitude of SEPs are consistent with those of low-frequency repeated TMS and cathodal tDCS studies. Therefore, tSMS could be a useful tool for modulating cortical somatosensory processing. PMID:27698365
Kirimoto, Hikari; Asao, Akihiko; Tamaki, Hiroyuki; Onishi, Hideaki
This study was performed to investigate the possibility of non-invasive modulation of SEPs by the application of transcranial static magnetic field stimulation (tSMS) over the primary motor cortex (M1) and supplementary motor cortex (SMA), and to measure the strength of the NdFeB magnetic field by using a gaussmeter. An NdFeB magnet or a non-magnetic stainless steel cylinder (for sham stimulation) was settled on the scalp over M1 and SMA of 14 subjects for periods of 15 min. SEPs following right median nerve stimulation were recorded before and immediately after, 5 min after, and 10 min after tSMS from sites C3' and F3. Amplitudes of the N33 component of SEPs at C3' significantly decreased immediately after tSMS over M1 by up to 20%. However, tSMS over the SMA did not affect the amplitude of any of the SEP components. At a distance of 2-3 cm (rough depth of the cortex), magnetic field strength was in the range of 110-190 mT. Our results that tSMS over M1 can reduce the amplitude of SEPs are consistent with those of low-frequency repeated TMS and cathodal tDCS studies. Therefore, tSMS could be a useful tool for modulating cortical somatosensory processing.
ACCESSION NO. Brooks AFB, TX 78235-5301 62202F 7757 01 85 11. TITLE (I nclude Security Classification) (U) Auditory Evoked Potentials from the Frog Eighth...identify by block number) S FIELD jGROUP SUB-GROUP F6 07 Auditory Evoked Potential Eighth Nerve Frog 06 10 19. ABSTRACT (Continue on reverse if necessary...and identify by block number) A method for recording evoked potentials from the eighth nerve of frogs using midline and lateral electrodes is described
Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai
Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.
Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai
Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.
Casper, Brandon; Mann, David
Auditory evoked potentials (AEP) were first used to examine hearing in elasmobranchs by Corwin and Bullock in the late 1970s and early 1980s, marking the first time AEPs had been measured in fishes. Results of these experiments identified the regions of the ear and brain in which sound is processed, though no actual hearing thresholds were measured. Those initial experiments provided the ground work for future AEP experiments to measure fish hearing abilities in a manner that is much faster and more convenient than classical conditioning. Data will be presented on recent experiments in which AEPs were used to measure the hearing thresholds of two species of elasmobranchs: the nurse shark, Ginglymostoma cirratum, and the yellow stingray, Urobatis jamaicencis. Audiograms were analyzed and compared to previously published audiograms obtained using classical conditioning with results indicating that hearing thresholds were similar for the two methods. These data suggest that AEP testing is a viable option when measuring hearing in elasmobranchs and can increase the speed in which future hearing measurements can be obtained.
Weinstein, G W
The visually evoked potential (VEP) was studied in normal and abnormal human subjects, and in Rhesus monkeys with central, paracentral, and peripheral photocoagulation lesions. A relatively simple protocol for clinical VEP testing is described. The monkeys showed similar VEP responses but these were smaller in amplitude than those obtained from human subjects. Central, but not paracentral or peripheral retinal lesions were associated with VEP abnormalities. For both monkey and human subjects, some variability of responses between normal and subjects was noted. Generally, there are differences in VEP responses obtained from the affected eye of abnormal subjects who had one eye which could serve as a control, as compared to responses from the normal eye. In these subjects as well as in subjects with two abnormal eyes, computer analysis of digitized VEP data from 10 Hz stimulus responses was performed. Fourier transformation analyses showed abnormalities which could be detected easily by evaluating the pattern of the amplitudes of the fundamental and first three harmonics. With this technique, it was possible to group correctly normal VEP's with eyes with normal visual acuity (greater than or equal to 20/30 or 0.67), and abnormal VEP's with eyes with poor visual acuity (less than 20/30 or 0.67) in 72% of cases. Analysis of the data obtained with 1 Hz and 10 Hz stimulation suggests that the components of the VEP related to visual acuity occur within the first 60-100 msec of the response, corresponding to the primary evoked response of Chiganek. The second, smaller wave of the response complex to 10 Hz flash stimuli corresponds to the primary evoked response, and is closely related to visual acuity. This was further supported in another series in which the digitized data was filtered around the stimulating frequency. It was possible to recognize visually this VEP waveform and subjectively interpret the record correctly in 85% of eyes with regard to visual acuity
evoked potentials. 1982, in preparation. (4) Tweel , L.H. van der, Regan, D. & Spekreijse, H. Some aspects of poten- tials evoked by changes in spatial...brightness contrast. 7th ISCERG Symp., Istanbul (1969), pub. by Univ. of Istanbul (1971), pp. 1-11. (5) Spekreijse, H., van der Tweel , L.H. & Regan, D...ponIses to pattern reversal. References (8) Tweel , L.11. van der & Spekreijse, H. Signal transport and rectifica- tion in the human evoked response
Moncho, Dulce; Poca, María A; Minoves, Teresa; Ferré, Alejandro; Rahnama, Kimia; Sahuquillo, Juan
Introduccion. La malformacion de Chiari (MC) incluye una serie de anomalias congenitas que tienen como comun denominador la ectopia de las amigdalas del cerebelo por debajo del foramen magno, lo que puede condicionar fenomenos compresivos del troncoencefalo, la medula espinal alta y los nervios craneales, alterando las respuestas de los potenciales evocados auditivos del tronco cerebral (PEATC) y de los potenciales evocados somatosensoriales (PESS). Sin embargo, las indicaciones de ambas exploraciones en las MC han sido motivo de estudio en un numero limitado de publicaciones, centradas en series cortas y heterogeneas de pacientes. Objetivo. Revisar los hallazgos de los PEATC y los PESS en los estudios publicados en pacientes con MC tipo 1 (MC-1) o tipo 2 (MC-2), y su indicacion en el diagnostico, tratamiento y seguimiento, especialmente en la MC-1. Desarrollo. Es un estudio de revision realizado mediante analisis de los estudios publicados en Medline desde 1966, localizados mediante PubMed, utilizando combinaciones de las palabras clave 'Chiari malformation', 'Arnold-Chiari malformation', 'Chiari type 1 malformation', 'Arnold-Chiari type 1 malformation', 'evoked potentials', 'brainstem auditory evoked potentials' y 'somatosensory evoked potentials', asi como informacion de pacientes con MC-1 valorados en los servicios de neurocirugia y neurofisiologia clinica del Hospital Universitari Vall d'Hebron. Conclusiones. Los hallazgos mas comunes de los PESS son la reduccion en la amplitud cortical para el nervio tibial posterior, la reduccion o ausencia del potencial cervical del nervio mediano y el aumento del intervalo N13-N20. En el caso de los PEATC, los hallazgos mas frecuentes descritos son el aumento del intervalo I-V y la alteracion periferica o coclear.
Sparacino, Giovanni; Milani, Stefano; Arslan, Edoardo; Cobelli, Claudio
Several approaches, based on different assumptions and with various degree of theoretical sophistication and implementation complexity, have been developed for improving the measurement of evoked potentials (EP) performed by conventional averaging (CA). In many of these methods, one of the major challenges is the exploitation of a priori knowledge. In this paper, we present a new method where the 2nd-order statistical information on the background EEG and on the unknown EP, necessary for the optimal filtering of each sweep in a Bayesian estimation framework, is, respectively, estimated from pre-stimulus data and obtained through a multiple integration of a white noise process model. The latter model is flexible (i.e. it can be employed for a large class of EP) and simple enough to be easily identifiable from the post-stimulus data thanks to a smoothing criterion. The mean EP is determined as the weighted average of the filtered sweeps, where each weight is inversely proportional to the expected value of the norm of the correspondent filter error, a quantity determinable thanks to the employment of the Bayesian approach. The performance of the new approach is shown on both simulated and real auditory EP. A signal-to-noise ratio enhancement is obtained that can allow the (possibly automatic) identification of peak latencies and amplitudes with less sweeps than those required by CA. For cochlear EP, the method also allows the audiology investigator to gather new and clinically important information. The possibility of handling single-sweep analysis with further development of the method is also addressed.
Pietilä, Sari; Lenko, Hanna L; Oja, Sakari; Koivisto, Anna-Maija; Pietilä, Timo; Mäkipernaa, Anne
This population-based cross-sectional study evaluates the clinical value of electroretinography and visual evoked potentials in childhood brain tumor survivors. A flash electroretinography and a checkerboard reversal pattern visual evoked potential (or alternatively a flash visual evoked potential) were done for 51 survivors (age 3.8-28.7 years) after a mean follow-up time of 7.6 (1.5-15.1) years. Abnormal electroretinography was obtained in 1 case, bilaterally delayed abnormal visual evoked potentials in 22/51 (43%) cases. Nine of 25 patients with infratentorial tumor location, and altogether 12 out of 31 (39%) patients who did not have tumors involving the visual pathways, had abnormal visual evoked potentials. Abnormal electroretinographies are rarely observed, but abnormal visual evoked potentials are common even without evident anatomic lesions in the visual pathway. Bilateral changes suggest a general and possibly multifactorial toxic/adverse effect on the visual pathway. Electroretinography and visual evoked potential may have clinical and scientific value while evaluating long-term effects of childhood brain tumors and tumor treatment.
Chertoff, Mark; Lichtenhan, Jeffery; Willis, Marie
In the experiments reported here, the amplitude and the latency of human compound action potentials (CAPs) evoked from a chirp stimulus are compared to those evoked from a traditional click stimulus. The chirp stimulus was created with a frequency sweep to compensate for basilar membrane traveling wave delay using the O-Chirp equations from Fobel and Dau [(2004). J. Acoust. Soc. Am. 116, 2213-2222] derived from otoacoustic emission data. Human cochlear traveling wave delay estimates were obtained from derived compound band action potentials provided by Eggermont [(1979). J. Acoust. Soc. Am. 65, 463-470]. CAPs were recorded from an electrode placed on the tympanic membrane (TM), and the acoustic signals were monitored with a probe tube microphone attached to the TM electrode. Results showed that the amplitude and latency of chirp-evoked N1 of the CAP differed from click-evoked CAPs in several regards. For the chirp-evoked CAP, the N1 amplitude was significantly larger than the click-evoked N1s. The latency-intensity function was significantly shallower for chirp-evoked CAPs as compared to click-evoked CAPs. This suggests that auditory nerve fibers respond with more unison to a chirp stimulus than to a click stimulus.
Silber, D H; Sinoway, L I; Leuenberger, U A; Amassian, V E
Single-pulse magnetic coil stimulation (Cadwell MES 10) over the cranium induces without pain an electric pulse in the underlying cerebral cortex. Stimulation over the motor cortex can elicit a muscle twitch. In 10 subjects, we tested whether motor cortical stimulation could also elicit skin sympathetic nerve activity (SSNA; n = 8) and muscle sympathetic nerve activity (MSNA; n = 5) in the peroneal nerve. Focal motor cortical stimulation predictably elicited bursts of SSNA but not MSNA; with successive stimuli, the SSNA responses did not readily extinguish (94% of discharges to the motor cortex evoked SSNA responses) and had predictable latencies [739 +/- 33 (SE) to 895 +/- 13 ms]. The SSNA responses were similar after stimulation of dominant and nondominant sides. Focal stimulation posterior to the motor cortex elicited extinguishable SSNA responses. In three of six subjects, anterior cortical stimulation evoked SSNA responses similar to those seen with motor cortex stimulation but without detectable movement; in the other subjects, anterior stimulation evoked less SSNA discharge than that seen with motor cortex stimulation. Contrasting with motor cortical stimulation, evoked SSNA responses were more readily extinguished with 1) peripheral stimulation that directly elicited forearm muscle activation accompanied by electromyograms similar to those with motor cortical stimulation; 2) auditory stimulation by the click of the energized coil when off the head; and 3) in preliminary experiments, finger afferent stimulation sufficient to cause tingling. Our findings are consistent with the hypothesis that motor cortex stimulation can cause activation of both alpha-motoneurons and SSNA.
Matas, Carla Gentile; Samelli, Alessandra Giannella; Angrisani, Rosanna Giaffredo; Magliaro, Fernanda Cristina Leite; Segurado, Aluísio C.
Background To characterize the findings of brainstem auditory evoked potential in HIV-positive individuals exposed and not exposed to antiretroviral treatment. Material/Methods This research was a cross-sectional, observational, and descriptive study. Forty-five HIV-positive individuals (18 not exposed and 27 exposed to the antiretroviral treatment – research groups I and II, respectively – and 30 control group individuals) were assessed through brainstem auditory evoked potential. Results There were no significant between-group differences regarding wave latencies. A higher percentage of altered brainstem auditory evoked potential was observed in the HIV-positive groups when compared to the control group. The most common alteration was in the low brainstem. Conclusions HIV-positive individuals have a higher percentage of altered brainstem auditory evoked potential that suggests central auditory pathway impairment when compared to HIV-negative individuals. There was no significant difference between individuals exposed and not exposed to antiretroviral treatment. PMID:26485202
Kiyota, Takeo; Fujiwara, Katsuo
This study measured the postural sway and brain potentials evoked by a visual depth stimulus. Thirteen subjects maintained standing posture on a force platform, and were administered two types of depth stimuli, strong and weak. The latency and amplitude of evoked potentials as well as changes in center of foot pressure (CFP) and the electromyogram (EMG) were examined. CFP displacement was found to change according to stimulus intensity. In the occipital lobe, evoked potentials exhibited a triphasic peak, with the first positive peak at approximately 120 ms (P120), the first negative peak at approximately 160 ms (N200), and the second positive peak at approximately 260 ms (P250). Brain evoked potentials correlated with CFP displacement as well as the latency of onset of EMG response. Onset of EMG response was probably related to the P120 component, whereas CFP displacement was related to the P250 component.
Luo, Jin Jun; Khurana, Divya S; Kothare, Sanjeev V
Measurements of brainstem auditory evoked potentials (BAEP) and middle latency auditory evoked potentials (MLAEP) are readily available neurophysiologic assessments. The generators for BAEP are believed to involve the structures of cochlear nerve, cochlear nucleus, superior olive complex, dorsal and rostral pons, and lateral lemniscus. The generators for MLAEP are assumed to be located in the subcortical area and auditory cortex. BAEP are commonly used in evaluating children with autistic and hearing disorders. However, measurement of MLAEP is rarely performed in young children. To explore the feasibility of this procedure in young children, we retrospectively reviewed our neurophysiology databank and charts for a 3-year period to identify subjects who had both BAEP and MLAEP performed. Subjects with known or identifiable central nervous system abnormalities from the history, neurologic examination and neuroimaging studies were excluded. This cohort of 93 children up to 3 years of age was divided into 10 groups based on the age at testing (upper limits of: 1 week; 1, 2, 4, 6, 8, 10 and 12 months; 2 years; and 3 years of age). Evolution of peak latency, interpeak latency and amplitude of waveforms in BAEP and MLAEP were demonstrated. We concluded that measurement of BAEP and MLAEP is feasible in children, as early as the first few months of life. The combination of both MLAEP and BAEP may increase the diagnostic sensitivity of neurophysiologic assessment of the integrity or functional status of both the peripheral (acoustic nerve) and the central (brainstem, subcortical and cortical) auditory conduction systems in young children with developmental speech and language disorders.
MULTIPLE COLOR STIMULUS INDUCED STEADY STATE VISUAL EVOKED POTENTIALS M. Cheng, X. Gao, S. Gao, D. Xu Institute of Biomedical Engineering...characteristics of high SNR and effectiveness in short-term identification of evoked responses. In most of the SSVEP experiments, single high...frequency stimuli are used. To characterize the complex rhythms in SSVEP, a new multiple color stimulus pattern is proposed in this paper. FFT and
Thirumala, Parthasarathy; Zhou, James; Krishnan, Rohan; Manem, Nihita; Umredkar, Shreya; Hamilton, D K; Balzer, Jeffrey R; Oudega, Martin
Iatrogenic spinal cord injury (SCI) is a cause of potentially debilitating post-operative neurologic complications. Currently, intra-operative neurophysiological monitoring (IONM) via somatosensory evoked potentials and motor-evoked potentials is used to detect and prevent impending SCI. However, no empirically validated interventions exist to halt the progression of iatrogenic SCI once it is detected. This is in part due to the lack of a suitable translational model that mimics the circumstances surrounding iatrogenic SCI detected via IONM. Here, we evaluate a model of simulated contusive iatrogenic SCI detected via IONM in adult female Sprague-Dawley rats. We show that transient losses of somatosensory evoked potentials responses are 88.24% sensitive (95% confidence interval [CI] 63.53-98.20) and 80% specific (95% CI 51.91-95.43) for significant functional impairment following simulated iatrogenic SCI. Similarly, we show that transient losses in motor-evoked potentials responses are 70.83% sensitive (95% CI 48.91-87.33) and 100% specific (95% CI 62.91-100.00) for significant functional impairment following simulated iatrogenic SCI. These results indicate that our model is a suitable replica of the circumstances surrounding clinical iatrogenic SCI.
Ahn, Sangtae; Kim, Kiwoong; Jun, Sung Chan
Brain-computer interface (BCI) performance has achieved continued improvement over recent decades, and sensorimotor rhythm-based BCIs that use motor function have been popular subjects of investigation. However, it remains problematic to introduce them to the public market because of their low reliability. As an alternative resolution to this issue, visual-based BCIs that use P300 or steady-state visually evoked potentials (SSVEPs) seem promising; however, the inherent visual fatigue that occurs with these BCIs may be unavoidable. For these reasons, steady-state somatosensory evoked potential (SSSEP) BCIs, which are based on tactile selective attention, have gained increasing attention recently. These may reduce the fatigue induced by visual attention and overcome the low reliability of motor activity. In this literature survey, recent findings on SSSEP and its methodological uses in BCI are reviewed. Further, existing limitations of SSSEP BCI and potential future directions for the technique are discussed. PMID:26834611
Todd, Neil P M; Paillard, Aurore C; Kluk, Karolina; Whittle, Elizabeth; Colebatch, James G
Acoustic sensitivity of the vestibular apparatus is well-established, but the contribution of vestibular receptors to the late auditory evoked potentials of cortical origin is unknown. Evoked potentials from 500 Hz tone pips were recorded using 70 channel EEG at several intensities below and above the vestibular acoustic threshold, as determined by vestibular evoked myogenic potentials (VEMPs). In healthy subjects both auditory mid- and long-latency auditory evoked potentials (AEPs), consisting of Na, Pa, N1 and P2 waves, were observed in the sub-threshold conditions. However, in passing through the vestibular threshold, systematic changes were observed in the morphology of the potentials and in the intensity dependence of their amplitude and latency. These changes were absent in a patient without functioning vestibular receptors. In particular, for the healthy subjects there was a fronto-central negativity, which appeared at about 42 ms, referred to as an N42, prior to the AEP N1. Source analysis of both the N42 and N1 indicated involvement of cingulate cortex, as well as bilateral superior temporal cortex. Our findings are best explained by vestibular receptors contributing to what were hitherto considered as purely auditory evoked potentials and in addition tentatively identify a new component that appears to be primarily of vestibular origin.
Kothari, Ruchi; Bokariya, Pradeep; Singh, Smita; Singh, Ramji
Visual information is fundamental to how we appreciate our environment and interact with others. The visual evoked potential (VEP) is among those evoked potentials that are the bioelectric signals generated in the striate and extrastriate cortex when the retina is stimulated with light which can be recorded from the scalp electrodes. In the current paper, we provide an overview of the various modalities, techniques, and methodologies which have been employed for visual evoked potentials over the years. In the first part of the paper, we cast a cursory glance on the historical aspect of evoked potentials. Then the growing clinical significance and advantages of VEPs in clinical disorders have been briefly described, followed by the discussion on the earlier and currently available methods for VEPs based on the studies in the past and recent times. Next, we mention the standards and protocols laid down by the authorized agencies. We then summarize the recently developed techniques for VEP. In the concluding section, we lay down prospective research directives related to fundamental and applied aspects of VEPs as well as offering perspectives for further research to stimulate inquiry into the role of visual evoked potentials in visual processing impairment related disorders. PMID:27034907
MARSH, J T; WORDEN, F G; HICKS, L
Auditory potentials were recorded from bipolar electrodes chronically implanted in the cochlear nuclei of four cats. In a training box modified to reduce echoes these animals were exposed to clicks and tone pulses presented from an overhead speaker. Slight changes in the position of the animal in the resulting sound field produced marked changes in the potentials evoked from the cochlear nucleus. These phenomena were observed in the unanesthetized, unrestrained subjects as well as in those under Nembutal anesthesia. It is suggested that these acoustic effects complicate the analysis and interpretation of potentials evoked from the cochlear nucleus under conditions of habituation, shifts in attention, and learning.
Quian Quiroga, R.
We present a method for the analysis of electroencephalograms (EEG). In particular, small signals due to stimulation, so-called evoked potentials (EPs), have to be detected in the background EEG. This is achieved by using a denoising implementation based on the wavelet decomposition. One recording of visual evoked potentials, and recordings of auditory evoked potentials from four subjects corresponding to different age groups are analyzed. We find higher variability in older individuals. Moreover, since the EPs are identified at the single stimulus level (without need of ensemble averaging), this will allow the calculation of better resolved averages. Since the method is parameter free (i.e. it does not need to be adapted to the particular characteristics of each recording), implementations in clinical settings are imaginable.
Watson, Meghan; Sawan, Mohamad
Microstimulation of brain tissue plays a key role in a variety of sensory prosthetics, clinical therapies and research applications, however the effects of stimulation parameters on the responses they evoke remain widely unknown. In particular, the effects of parameters when delivered in the form of a stimulus train as opposed to a single pulse are not well understood despite the prevalence of stimulus train use. We aimed to investigate the contribution of each parameter of a stimulus train to the duration of the motor responses they evoke in forelimb muscles. We used constant-current, biphasic, square wave pulse trains in acute terminal experiments under ketamine anaesthesia. Stimulation parameters were systematically tested in a pair-wise fashion in the caudal forelimb region of the motor cortex in 7 Sprague-Dawley rats while motor evoked potential (MEP) recordings from the forelimb were used to quantify the influence of each parameter in the train. Stimulus amplitude and train duration were shown to be the dominant parameters responsible for increasing the total duration of the MEP, while interphase interval had no effect. Increasing stimulus frequency from 100–200 Hz or pulse duration from 0.18–0.34 ms were also effective methods of extending response durations. Response duration was strongly correlated with peak time and amplitude. Our findings suggest that motor cortex intracortical microstimulations are often conducted at a higher frequency rate and longer train duration than necessary to evoke maximal response duration. We demonstrated that the temporal properties of the evoked response can be both predicted by certain response metrics and modulated via alterations to the stimulation signal parameters. PMID:27442588
Mifsud, Nathan G; Beesley, Tom; Watson, Tamara L; Whitford, Thomas J
Reduction of auditory event-related potentials (ERPs) to self-initiated sounds has been considered evidence for a predictive model in which copies of motor commands suppress sensory representations of incoming stimuli. However, in studies which involve arbitrary auditory stimuli evoked by sensory-unspecific motor actions, learned associations may underlie ERP differences. Here, in a new paradigm, eye motor output generated auditory sensory input, a naïve action-sensation contingency. We measured the electroencephalogram (EEG) of 40 participants exposed to pure tones, which they produced with either a button-press or volitional saccade. We found that button-press-initiated stimuli evoked reduced amplitude compared to externally initiated stimuli for both the N1 and P2 ERP components, whereas saccade-initiated stimuli evoked intermediate attenuation at N1 and no reduction at P2. These results indicate that the motor-to-sensory mapping involved in speech production may be partly generalized to other contingencies, and that learned associations also contribute to the N1 attenuation effect.
Kojder, I; Garell, S; Włodarczyk, E; Sagan, L; Jezewski, D; Slósarek, J
The authors studied auditory brainstem evoked potentials (BAEP) in 27 organ donors aged 40 to 68 years treated in neurosurgery units in Szczecin and Grenoble. Abnormal results were found in all cases. In 63% of cases no evoked action potentials were obtained, in 34% only the 1st wave was obtained, and in two cases evolution was observed with activity extinction. The authors believe that in the process of shaping of BAEP morphotic extinction begins from the later waves to earlier ones in agreement with the rostrocaudal direction of extinction of the functions or brain midline structures, and in a single study various findings may be obtained.
Lentz, Linnea; Zhao, Yan; Kelly, Matthew T; Schindeldecker, William; Goetz, Steven; Nelson, Dwight E; Raike, Robert S
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is used to treat movement disorders, including advanced Parkinson's disease (PD). The pathogenesis of PD and the therapeutic mechanisms of DBS are not well understood. Large animal models are essential for investigating the mechanisms of PD and DBS. The purpose of this study was to develop a novel sheep model of STN DBS and quantify the stimulation-evoked motor behaviors. To do so, a large sample of animals was chronically-implanted with commercial DBS systems. Neuroimaging and histology revealed that the DBS leads were implanted accurately relative to the neurosurgical plan and also precisely relative to the STN. It was also possible to repeatedly conduct controlled evaluations of stimulation-evoked motor behavior in the awake-state. The evoked motor responses depended on the neuroanatomical location of the electrode contact selected for stimulation, as contacts proximal to the STN evoked movements at significantly lower voltages. Tissue stimulation modeling demonstrated that selecting any of the contacts stimulated the STN, whereas selecting the relatively distal contacts often also stimulated thalamus but only the distal-most contact stimulated internal capsule. The types of evoked motor behaviors were specific to the stimulation frequency, as low but not high frequencies consistently evoked movements resembling human tremor or dyskinesia. Electromyography confirmed that the muscle activity underlying the tremor-like movements in the sheep was consistent with human tremor. Overall, this work establishes that the sheep is a viable a large-animal platform for controlled testing of STN DBS with objective motor outcomes. Moreover, the results support the hypothesis that exaggerated low-frequency activity within individual nodes of the motor network can drive symptoms of human movement disorders, including tremor and dyskinesia.
Valverde Junguito, J L; Aldana Díaz, E M; Pérez Lorensu, P J; González Miranda, F
Neurophysiologic monitoring with somatosensory and motor evoked potentials in spinal surgery is now widely applied in order to reduce the risk of neural injury and facilitate intraoperative decision making. Most anesthetics affect such monitoring by altering both somatosensory and motor evoked responses and these effects may place constraints on the choice of anesthetic. Intraoperative management includes maintaining stable physiologic conditions, which involves adjusting hemodynamic parameters, maintaining normal blood flow to promote proper oxygen exchange, ensuring proper ventilation, and avoiding variations in temperature. Close collaboration between the anesthetist, the surgeon, and the neurophysiologist will ensure the success of intraoperative monitoring and make it possible to avoid neural injury by making timely changes in the surgical approach.
Lund, D; Ruggiero, A M; Ferguson, S M; Wright, J; English, B A; Reisz, P A; Whitaker, S M; Peltier, A C; Blakely, R D
The presynaptic, hemicholinium-3 sensitive, high-affinity choline transporter (CHT) supplies choline for acetylcholine (ACh) synthesis. In mice, a homozygous deletion of CHT (CHT-/-) leads to premature cessation of spontaneous or evoked neuromuscular signaling and is associated with perinatal cyanosis and lethality within 1 h. Heterozygous (CHT+/-) mice exhibit diminished brain ACh levels and demonstrate an inability to sustain vigorous motor activity. We sought to explore the contribution of CHT gene dosage to motor function in greater detail using transgenic mice where CHT is expressed under control of the motor neuron promoter Hb9 (Hb9:CHT). On a CHT-/- background, the Hb9:CHT transgene conferred mice with the ability to move and breath for a postnatal period of ∼24 h, thus increasing survival. Conversely, Hb9:CHT expression on a wild-type background (CHT+/+;Hb9:CHT) leads to an increased capacity for treadmill running compared to wild-type littermates. Analysis of the stimulated compound muscle action potential (CMAP) in these animals under basal conditions established that CHT+/+;Hb9:CHT mice display an unexpected, bidirectional change, producing either elevated or reduced CMAP amplitude, relative to CHT+/+ animals. To examine whether these two groups arise from underlying changes in synaptic properties, we used high-frequency stimulation of motor axons to assess CMAP recovery kinetics. Although CHT+/+; Hb9:CHT mice in the two groups display an equivalent, time-dependent reduction in CMAP amplitude, animals with a higher basal CMAP amplitude demonstrate a significantly enhanced rate of recovery. To explain our findings, we propose a model whereby CHT support for neuromuscular signaling involves contributions to ACh synthesis as well as cholinergic synaptic vesicle availability.
Galambos, R.; Benson, P.; Smith, T. S.; Schulman-Galambos, C.; Osier, H.
Confirmation is provided for the belief that evoked potentials may reflect differences in hemispheric functioning that are marginal at best. Subjects were right-handed and audiologically normal men and women, and responses were recorded using standard EEG techniques. Subjects were instructed to listen for the targets while laying in a darkened sound booth. Different stimuli, speech and tone signals, were used. Speech sounds were shown to evoke a response pattern that resembles that to tone or clicks. Analysis of variances on peak amplitude and latency measures showed no significant differences between hemispheres, however, a Wilcoxon test showed significant differences in hemispheres for certain target tasks.
Haupt, Walter F; Pawlik, Gunter; Thiel, Alexander
Results of somatosensory evoked potential (SEP) and brainstem auditory evoked potential (BAEP) examinations performed early in the clinical course of patients with acute cerebrovascular disease correlate statistically significantly with outcome regardless of type and localization of the primary lesion. The prognostic value of serial examinations of SEP and BAEP has not been studied yet. The authors examined a group of 215 patients suffering from acute stroke requiring neurocritical care composed of 75 supratentorial and 36 infratentorial ischemic strokes, 58 supratentorial and 18 infratentorial hemorrhages, and 28 aneurysmatic subarachnoid hemorrhages prospectively using spinal and cortical SEP and BAEP according to routine procedures on admission as well as after 1 and 2 weeks. The findings were correlated to outcome at 4 weeks. Statistical assessment was performed using standard methods of contingency analysis. In all groups, SEP findings were significantly correlated with outcome at initial and all subsequent examinations, similar correlations were also found for BAEP. However, after partialling out the prognostic information gained from the initial examination of SEP and BAEP, the follow-up examinations rendered only a marginal increase in prognostic information. Therefore, the initial examination of evoked potentials supplies valuable prognostic information, however, serial examinations of evoked potentials during the first weeks of disease improve the prognostic information only marginally.
Titlic, M; Isgum, V; Buca, A; Kolic, K; Tonkic, A; Jukic, I; Milas, I
Early diagnosis of spondylodiscitis is a condition of efficient conservative treatment. Somatosensory-evoked potentials with clinical examination results are used in assessing the diagnosis, as well as in monitoring the course of disease and healing. MRI clearly shows the inflammatory process, healing and scars. We report a 46-year-old woman suffering from non-specific interscapular pains. The evoked somatosensory potentials of the tibial nerveshow potential conductivity being slowed down through the thoracic spine, which is clearly evident from the prolonged latency and the decreased amplitude of the evoked response. The performed thoracic spine MRI shows spondylodiscitis at the Thl0-11 level. The subject is a nurse administering BCG therapy at a urology clinic, due to the fact of which this was deemed to have been a case of tuberculous spondylodiscitis. Due to the possibility of scattering the causative agent by needle, the biopsy was given up and antituberculous therapy was administered ex juvantibus. The disease was followed up by clinical examinations, somatosensory-evoked potentials and MRI up to fully successful and final recovery from spondylodiscitis. The above examinations are of great help in diagnosing the tuberculous spondylodiscitis and monitoring the recovery (Fig. 6, Ref. 16).
Munivrana, Boska; Mildner, Vesna
In some cochlear implant users, success is not achieved in spite of optimal clinical factors (including age at implantation, duration of rehabilitation and post-implant hearing level), which may be attributed to disorders at higher levels of the auditory pathway. We used cortical auditory evoked potentials to investigate the ability to perceive…
Sandmann, Pascale; Eichele, Tom; Buechler, Michael; Debener, Stefan; Jancke, Lutz; Dillier, Norbert; Hugdahl, Kenneth; Meyer, Martin
Auditory evoked potentials are tools widely used to assess auditory cortex functions in clinical context. However, in cochlear implant users, electrophysiological measures are challenging due to implant-created artefacts in the EEG. Here, we used independent component analysis to reduce cochlear implant-related artefacts in event-related EEGs of…
Jutzeler, Catherine R.; Warner, Freda M.; Wanek, Johann; Curt, Armin; Kramer, John L. K.
The ‘thermal grill illusion’ (TGI) is a unique cutaneous sensation of unpleasantness, induced through the application of interlacing warm and cool stimuli. While previous studies have investigated optimal parameters and subject characteristics to evoke the illusion, our aim was to examine the modulating effect as a conditioning stimulus. A total of 28 healthy control individuals underwent three testing sessions on separate days. Briefly, 15 contact heat stimuli were delivered to the right hand dorsum, while the left palmar side of the hand was being conditioned with either neutral (32 °C), cool (20 °C), warm (40 °C), or TGI (20/40 °C). Rating of perception (numeric rating scale: 0–10) and evoked potentials (i.e., N1 and N2P2 potentials) to noxious contact heat stimuli were assessed. While cool and warm conditioning decreased cortical responses to noxious heat, TGI conditioning increased evoked potential amplitude (N1 and N2P2). In line with other modalities of unpleasant conditioning (e.g., sound, visual, and olfactory stimulation), cortical and possibly sub-cortical modulation may underlie the facilitation of contact heat evoked potentials. PMID:28079118
Dorokhov, V B; Verbitskaya, Yu S; Lavrova, T P
Sounds provide the most suitable stimuli for studies of information processes occurring in the brain during falling asleep and at different stages of sleep. The widely used analysis of evoked potentials averaged for groups of subjects has a number of disadvantages associated with their individual variability. Thus, in the present study, measures of the individual components of auditory evoked potentials were determined and selectively summed for individual subjects, with subsequent analysis by group. The aim of the present work was to identify measures of auditory evoked potentials providing quantitative assessment of the dynamics of the brain's functional state during the appearance of errors in activity associated with decreases in the level of waking and falling asleep. A monotonous psychomotor test was performed in the lying position with the eyes closed; this consisted of two alternating parts: the first was counting auditory stimuli from 1 to 10 with simultaneous pressing of a button, and the second was counting stimuli from 1 to 5 silently without pressing the button, and so on. Computer-generated sound stimuli (duration 50 msec, envelope filling frequency 1000 Hz, intensity 60 dB) were presented binaurally with interstimulus intervals of 2.4-2.7 sec. A total of 41 subjects took part (both genders, mean age 25 years), of which only 23 fell asleep; data for 14 subjects with sufficient episodes of falling asleep were analyzed. Comparison of measures of auditory evoked potentials (the latencies and amplitudes of the N1, P2, N2, and P3 components) during correct and erroneous psychomotor test trials showed that decreases in the level of consciousness elicited significant increases in the amplitudes of the components of the vertex N1-P2-N2 complex in series without button pressing. The greatest changes in auditory evoked potentials in both series were seen in the N2 component, with latency 330-360 msec, which has a common origin with the EEG theta rhythm and is
Visual evoked potentials (VEPs) were recorded from a 53-year-old man with prosopagnosia during presentation of slides of known and unknown faces and under two control conditions. ANOVA comparisons with a normal male group showed no differences in P100 amplitude, P300 amplitude or P300 latency. There were no significant evoked potential differences between the patient and controls specifically related to the face conditions. There was, however, a significant delay in the latency of P100 from both hemispheres during all types of stimuli. This prolonged latency was asymmetrical, showing a right sided emphasis with the control conditions: pattern reversal and slides of geometric designs. This finding, of a dissociation in the interhemispheric delay, provides physiological evidence of stimulus-specific organisation at an early, sensory level. The fact that the P100 component showed a marked delay, yet P300 fell within normal limits for amplitude and latency, suggests that this patient's problem lies at a perceptual level.
Skidmore, Trent A.
This paper presents experimental evidence to support the feasibility of an evoked-potential vision-tracking system. The topics discussed are stimulator construction, verification of the photic driving response in the electroencephalogram, a method for performing frequency separation, and a transient-analysis example. The final issue considered is that of object multiplicity (concurrent visual stimuli with different flashing rates). The paper concludes by discussing several applications currently under investigation.
Krusienski, Dean J; Allison, Brendan Z
Steady-state visual evoked potentials (SSVEPs) are oscillating components of the electroencephalogram (EEG) that are detected over the occipital areas, having frequencies corresponding to visual stimulus frequencies. SSVEPs have been demonstrated to be reliable control signals for operating a brain-computer interface (BCI). This study uses offline analyses to investigate the characteristics of SSVEP harmonic amplitude and phase coupling and the impact of using this information to construct a matched filter for continuously tracking the signal.
to amplitude-modulated light stimuli, have been extensively investigated and applied in various fields: system identification studies ( Tweel and Lund...msec ( Tweel and Lunel, 1965, for MFs > 35 Hz; Regan, 1972; Spekreijse et al., 1977). 4.1.2 Auditory continuous evoked potentials Contrary to the visual...researchers ( Tweel and Lunel, 1965; Regan, 1966, 1972; Spckreijse, 1966; Spekreijse et al., 1977; Diamond, 1977; Junker, 1984; Junker and Peio, 1984
Liberati, D; DiCorrado, S; Mandelli, S
Single trial analysis of brain-evoked potentials via stochastic parametric identification and filtering is here extended to multichannel recordings, leading to the topographic mapping of the brain activity elicited by a single stimulus, instead of the usual averaged mapping. The temporal dynamics of the subsequent sweeps in the protocol of a neurophysiologic experiment can thus be recovered and quantified also on its spatial characteristic.
Andrillon, Thomas; Kouider, Sid; Agus, Trevor; Pressnitzer, Daniel
Experience continuously imprints on the brain at all stages of life. The traces it leaves behind can produce perceptual learning , which drives adaptive behavior to previously encountered stimuli. Recently, it has been shown that even random noise, a type of sound devoid of acoustic structure, can trigger fast and robust perceptual learning after repeated exposure . Here, by combining psychophysics, electroencephalography (EEG), and modeling, we show that the perceptual learning of noise is associated with evoked potentials, without any salient physical discontinuity or obvious acoustic landmark in the sound. Rather, the potentials appeared whenever a memory trace was observed behaviorally. Such memory-evoked potentials were characterized by early latencies and auditory topographies, consistent with a sensory origin. Furthermore, they were generated even on conditions of diverted attention. The EEG waveforms could be modeled as standard evoked responses to auditory events (N1-P2) , triggered by idiosyncratic perceptual features acquired through learning. Thus, we argue that the learning of noise is accompanied by the rapid formation of sharp neural selectivity to arbitrary and complex acoustic patterns, within sensory regions. Such a mechanism bridges the gap between the short-term and longer-term plasticity observed in the learning of noise [2, 4-6]. It could also be key to the processing of natural sounds within auditory cortices , suggesting that the neural code for sound source identification will be shaped by experience as well as by acoustics.
Amir, Avner; Jewett, Don L.
Methods to localize the sources of Brain Evoked Potential Maps based on modeling of the sources as point dipoles have been widely used for more than twenty years. Such methods still lack a basic theory which can answer questions regarding the resolution and uniqueness of the results in the context of a realistic head model, with no a prior restrictions on the sources. In the first part of the paper we present simple physical models for the origin of far-field potentials associated with the auditory and somatosensory systems. An action potential travels along a straight axon can only produce a quadrupole field at far distances. We show that the far field potentials must originate when the action potential passes through a bent axon or through changes in the conductivities or in the external boundaries of the volume conductor surrounding the axon. We discuss the question of uniqueness of the solution for the 'inverse problem' of evoked potentials. This problem involved the reconstruction of the location and pattern of activity of the neuronal generators in the brain, given the map of the scalp electric potentials. We show that in a head shape with a realistic geometry spatially distinct points, line or open surface generators cannot create the same scalp potential map. The same applies to two non-overlapping generators occupying finite volumes.
Supin, Alexander Ya.; Nactigall, Paul E.; Pawloski, Jeffrey; Au, Whitlow W. L.
The evoked-potential (EP) method is effective in studies of hearing capabilities of cetaceans. However, until now EP studies in cetaceans were performed only in conditions of passive hearing by recording EP to external stimuli. Can this method be applied to study active echolocation in odontocetes? To answer this question, auditory brainstem evoked responses (ABR) were recorded in a false killer whale while the animal echolocated a target within an experiment in which the animal reported the target present or absent. The ABR collection was triggered by echolocation clicks. In these conditions, the recorded ABR pattern contained a duplicate set of waves. A comparison of ABR wave delays recorded during echolocation with those recorded during regular external stimulation has shown that the first set of waves is a response to the emitted click whereas the second one is a response to the echo. Both responses, to the emitted click and to the echo, were of comparable amplitude in spite of the intensity difference of these two sounds of more than 40 dB near the animal's head. This finding indicates some mechanisms releasing responses to echoes from masking by loud emitted clicks. The evoked-potential method may be productive to investigate these mechanisms.
Ohnari, Keiko; Okada, Kazumasa; Takahashi, Toshiyuki; Mafune, Kosuke; Adachi, Hiroaki
Neuromyelitis optica spectrum disorder (NMOSD) has been differentiated from relapsing-remitting multiple sclerosis (RRMS) by clinical, laboratory, and pathological findings, including the presence of the anti-aquaporin 4 antibody. Measurement of evoked potentials (EPs) is often used for the diagnosis of RRMS, although the possibility of applying EPs to the diagnosis of NMOSD has not been investigated in detail. Eighteen patients with NMOSD and 28 patients with RRMS were included in this study. The patients' neurological symptoms and signs were examined and their EPs were recorded. Characteristic findings were absence of visual evoked potentials and absence of motor evoked potentials in the lower extremities in patients with NMOSD, and a delay in these potentials in patients with RRMS. Most patients with NMOSD did not present abnormal subclinical EPs, whereas many patients with RRMS did. None of the patients with NMOSD showed abnormalities in auditory brainstem responses. NMOSD can be differentiated from RRMS by EP data obtained in the early stages of these diseases.
The Efficacy of Intraoperative Neurophysiological Monitoring Using Transcranial Electrically Stimulated Muscle-evoked Potentials (TcE-MsEPs) for Predicting Postoperative Segmental Upper Extremity Motor Paresis After Cervical Laminoplasty
Manabe, Hideki; Izumi, Bunichiro; Tanaka, Hiroyuki; Kawai, Kazumi; Tanaka, Nobuhiro
Study Design: Prospective study. Objective: To investigate the efficacy of transcranial electrically stimulated muscle-evoked potentials (TcE-MsEPs) for predicting postoperative segmental upper extremity palsy following cervical laminoplasty. Summary of Background Data: Postoperative segmental upper extremity palsy, especially in the deltoid and biceps (so-called C5 palsy), is the most common complication following cervical laminoplasty. Some papers have reported that postoperative C5 palsy cannot be predicted by TcE-MsEPs, although others have reported that it can be predicted. Methods: This study included 160 consecutive cases that underwent open-door laminoplasty, and TcE-MsEP monitoring was performed in the biceps brachii, triceps brachii, abductor digiti minimi, tibialis anterior, and abductor hallucis. A >50% decrease in the wave amplitude was defined as an alarm point. According to the monitoring alarm, interventions were performed, which include steroid administration, foraminotomies, etc. Results: Postoperative deltoid and biceps palsy occurred in 5 cases. Among the 155 cases without segmental upper extremity palsy, there were no monitoring alarms. Among the 5 deltoid and biceps palsy cases, 3 had significant wave amplitude decreases in the biceps during surgery, and palsy occurred when the patients awoke from anesthesia (acute type). In the other 2 cases in which the palsy occurred 2 days after the operation (delayed type), there were no significant wave decreases. In all of the cases, the palsy was completely resolved within 6 months. Discussion: The majority of C5 palsies have been reported to occur several days after surgery, but some of them have been reported to occur immediately after surgery. Our results demonstrated that TcE-MsEPs can predict the acute type, whereas the delayed type cannot be predicted. Conclusions: A >50% wave amplitude decrease in the biceps is useful to predict acute-type segmental upper extremity palsy. Further examination
Kileny, Paul R
Evoked potential measures are integral to the treatment of patients with cochlear implants. In particular, these techniques are useful in the management of the pediatric patient. This brief report describes three categories of evoked potentials including clinical and research examples: electrically evoked auditory brain stem responses with transtympanic stimulation, middle-latency responses with cochlear implant stimulation, and cognitive evoked potentials elicited by speech stimuli.
Kim, Ji Sun; Kim, Sungkean; Jung, Wookyoung; Im, Chang-Hwan; Lee, Seung-Hwan
Emotional sensitivity and impulsivity could cause interpersonal conflicts and neuropsychiatric problems. Serotonin is correlated with behavioral inhibition and impulsivity. This study evaluated whether the loudness dependence of auditory evoked potential (LDAEP), a potential biological marker of central serotonergic activity, could reflect emotional sensitivity and impulsivity. A total of 157 healthy individuals were recruited, who performed LDAEP and Go/Nogo paradigms during electroencephalogram measurement. Barratt impulsivity scale (BIS), Conners’ Adult ADHD rating scale (CAARS), and affective lability scale (ALS) were evaluated. Comparison between low and high LDAEP groups was conducted for behavioural, psychological, and event-related potential (ERP) measures. The high LDAEP group showed significantly increased BIS, a subscale of the CAARS, ALS, and false alarm rate of Nogo stimuli compared to the low LDAEP group. LDAEP showed significant positive correlations with the depression scale, ALS scores, subscale of the CAARS and Nogo-P3 amplitude. In the source activity of Nogo-P3, the cuneus, lingual gyrus, and precentral gyrus activities were significantly increased in the high LDAEP group. Our study revealed that LDAEP could reflect emotional sensitivity and impulsivity. LDAEP, an auditory evoked potential could be a useful tool to evaluate emotional regulation. PMID:27910865
Jones, S. M.; Jones, T. A.
Electrophysiological responses to pulsed linear acceleration stimuli were recorded in chicken embryos incubated for 19 or 20 days (E19/E20). Responses occurred within the first 16 ms following the stimulus onset. The evoked potentials disappeared following bilateral labyrinthectomy, but persisted following cochlear destruction alone, thus demonstrating that the responses were vestibular. Approximately 8 to 10 response peaks could be identified. The first 4 positive and corresponding negative components (early peaks with latencies < 6.0 ms) were scored and latencies and amplitudes quantified. Vestibular response latencies were significantly longer (P < 0.01) and amplitudes significantly smaller (P < 0.001) than those observed in 2-week-old birds. Mean response threshold for anesthetized embryos was -15.9dBre 1.0 g/ms, which was significantly higher (P < 0.03) than those observed in 2-week-old birds (-23.0dBre 1.0 g/ms). Latency/intensity functions (that is, slopes) were not significantly different between embryos and 2-week-old animals, but amplitude/intensity functions for embryos were significantly shallower than those for 2-week-old birds (P < 0.001). We presume that these differences reflect the refinement of sensory function that occurs following 19 to 20 days of incubation. The recording of vestibular evoked potentials provides an objective, direct and noninvasive measure of peripheral vestibular function in the embryo and, as such, the method shows promise as an investigative tool. The results of the present study form the definitive basis for using vestibular evoked potentials in the detailed study of avian vestibular ontogeny and factors that may influence it.
The author reviewed clinical aspects of vestibular evoked myogenic potentials (VEMPs). Now two types of VEMPs are available. The first one is cervical VEMP, which is recorded in the sternocleidomastoid muscle and predominantly reflects sacculo-collic reflex. The other is ocular VEMP, which is usually recorded below the lower eye lid and predominantly reflects utriculo-ocular reflex. VEMPs play important roles not only for assessment of common vestibular diseases but also for establishment of new clinical entities. Clinical application in Meniere's disease, vestibular neuritis, benign paroxysmal positional vertigo, vestibular migraine, idiopathic otolithic vertigo, and central vertigo/dizziness was reviewed.
XBAR+X (I) YBAR - YBAR +V (I) CONTINUE XBAR=XBAR/N VBAR= YBAR /N A-0. B-O. DO 10 I=19N C-X(I)-XBAR A=A+ Y (I)*C -36- B=B+C**2 *10 CONTINUE BSLP=A/B BI NT=YDAR...and duration of the latency effect following impact, the following exponential model was proposed: y = B + St + h(t)D + h(t)Aexp(t/T) + £(t) (1) where... y is the value of the shift in latency with respect to the preimpact baseline average evoked potential (AEP
Lucchese, F; Mecacci, L
Visual evoked potentials (VEPs) were recorded in 12 adult participants as a function of the temporal frequency of a phase-reversed checkerboard, with or without a simultaneously presented white noise. During the VEP recordings also the pulse rate was measured. VEP amplitude changed as function of temporal frequency, but it was not affected by noise. Pulse rate was stable during the session without noise, but it increased during the white noise stimulation at high temporal frequencies. Heart acceleration might be associated to conditions when processing at low levels of visual sensitivity (high temporal frequencies) is furthermore disturbed by interfering stimulation (noise).
Hink, R. F.; Van Voorhis, S. T.; Hillyard, S. A.; Smith, T. S.
The sensitivity of the scalp-recorded, auditory evoked potential to selective attention was examined while subjects responded to stimuli presented to one ear (focused attention) and to both ears (divided attention). The amplitude of the N1 component was found to be largest to stimuli in the ear upon which attention was to be focused, smallest to stimuli in the ear to be ignored, and intermediate to stimuli in both ears when attention was divided. The results are interpreted as supporting a capacity model of attention.
Wolf, W.; Appel, U.; Rauner, H.
Transient evoked potentials (EP) are variations of the on-going electroencephalogram (EEG) in response to the application of sensory stimuli. Since their amplitudes are very small in comparison to the spontaneous EEG, signal extraction methods must be applied to them before their characteristics are measureable. Several signal ex-traction methods which are actually used in EP research are outlined, especially those showing an adaptive characteristic. As a further development, a new method is proposed which considers the on-going EEG preceding the stimulus application for the EP processing. The computational procedure will be described and some preliminary results are given.
Piché, M; Arsenault, M; Rainville, P
In the past two decades, functional brain imaging has considerably advanced our knowledge of cerebral pain processing. However, many important links are still missing in our understanding of brain activity in relation to the regulation of pain-related physiological responses. This fMRI study investigates the cerebral correlates of pain (rating), motor responses (RIII-reflex) and autonomic activity (skin conductance response; SCR) evoked by noxious electrical stimulation. Stimulus intensity was adjusted individually based on the RIII threshold to control for differences in peripheral processes and baseline spinal activation. Covariance analyses were used to reveal individual differences in brain activity uniquely associated with individual differences in pain, RIII and SCR. Shock-evoked activity in cingulate, medial orbitofrontal and parahippocampal regions predicted pain sensitivity. Moreover, lateral orbitofrontal and cingulate areas showed strong positive associations with individual differences in motor reactivity but negative associations with autonomic reactivity. Notably, individual differences in OFC activation was almost fully accounted by the combination of individual measures of autonomic and motor reactivity (R(2)=0.93). Additionally, trial-to-trial fluctuations of RIII-reflex and SCR (within-subjects) were proportional to shock-evoked responses in subgenual cingulate cortex (RIII), anterior insula (SCR) and midcingulate cortex (SCR and RIII). Together, these results confirm that individual differences in perceptual, motor, and autonomic components of pain reflect robust individual differences in brain activity. Furthermore, the brain correlates of trial-to-trial fluctuations in pain responses provide additional evidence for a partial segregation of sub-systems involved more specifically in the ongoing monitoring, and possibly the regulation, of pain-related motor and autonomic responses.
Yu, Nannan; Liu, Haikuan; Wang, Xiaoyan; Lu, Hanbing
In this paper, we present a novel approach to solving an evoked potentials estimating problem. Generally, the evoked potentials in two consecutive trials obtained by repeated identical stimuli of the nerves are extremely similar. In order to trace evoked potentials, we propose a joint sparse representation-based double-trial evoked potentials estimation method, taking full advantage of this similarity. The estimation process is performed in three stages: first, according to the similarity of evoked potentials and the randomness of a spontaneous electroencephalogram, the two consecutive observations of evoked potentials are considered as superpositions of the common component and the unique components; second, making use of their characteristics, the two sparse dictionaries are constructed; and finally, we apply the joint sparse representation method in order to extract the common component of double-trial observations, instead of the evoked potential in each trial. A series of experiments carried out on simulated and human test responses confirmed the superior performance of our method.
Heydari, Nahid; Hajiabolhassani, Fahimeh; Fatahi, Jamileh; Movaseghi, Shafieh; Jalaie, Shohreh
Background: Rheumatoid arthritis (RA) is an autoimmune systemic disease. Most common autoimmune diseases are multisystem disorders that may also present with otological manifestations, and autoimmune inner ear disease accompanied by vestibular dysfunction. This study aimed to compare the vestibular function between RA patients and normal subjects using cervical vestibular evoked myogenic potentials (cVEMPs). Methods: In this cross- sectional study, 25patients with RA (19 female and 6 male: mean (±SD) age, 40.00 (±7.92) years) and 20 healthy subjects (15 female and 5 male: mean (±SD) age, 35.35 (±10.48) years) underwent cVEMPs, using 500 Hz-tone bursts at 95 dB nHL intensity level. Data were analyzed using independent sample t-test through SPSS software v. 16. Results: The mean peak latency of p13 was significantly higher in RA patients (p<0.001). The mean peak latency of n23 was significantly higher in patients in the left ear (p=0.03). Vestibular evoked myogenic potential (VEMP) responses were present in all (100%) of the participants. There were no significant differences in mean peak to peak amplitude and amplitude ratio between the two groups. Conclusion: According to the prolonged latency of VEMP responses in RA patients, lesions in the retrolabyrinthine, especially in the vestibulospinal tract are suspected. PMID:26478874
Ye, Jichao; Ma, Mengjun; Xie, Zhongyu; Wang, Peng; Tang, Yong; Huang, Lin; Chen, Keng; Gao, Liangbin; Wu, Yanfeng; Shen, Huiyong; Zeng, Yuanshan
Nonhuman primate models of spinal cord injury (SCI) have been widely used in evaluation of the efficacy and safety of experimental restorative interventions before clinical trials. However, no objective methods are currently available for the evaluation of neural function in nonhuman primates. In our long-term clinical practice, we have used evoked potential (EP) for neural function surveillance during operation and accumulated extensive experience. In the present study, a nonhuman primate model of SCI was established in 6 adult cynomologus monkeys through spinal cord contusion injury at T8–T9. The neural function before SCI and within 6 months after SCI was evaluated based on EP recording. A scoring system including somatosensory evoked potentials (SSEPs) and transcranial electrical stimulation-motor evoked potentials (TES-MEPs) was established for the evaluation of neural function of nonhuman primates with SCI. We compared the motor function scores of nonhuman primates before and after SCI. Our results showed that the EP below the injury level significantly changed during the 6 months after SCI. In addition, a positive correlation was identified between the EP scores and motor function. The EP-based scoring system is a reliable approach for evaluating the motor function changes in nonhuman primates with SCI. PMID:27629352
Dikmen, Pinar Yalinay; Oge, A. Emre
Objective/Context Dermatomal somatosensory-evoked potentials (dSEPs) may be valuable for diagnostic purposes in selected cases with spinal disorders. Design Reports on cases with successful use of dSEPs. Findings Cases 1 and 2 had lesions causing multiple root involvement (upper to middle lumbar region in Case 1 and lower sacral region in Case 2). Cystic lesions in both cases seemed to compress more than one nerve root, and stimulation at the center of the involved dermatomes in dSEPs helped to reveal the functional abnormality. Cases 3 and 4 had lesions involving the spinal cord with or without nerve root impairment. In Case 3, an magnetic resonance imaging (MRI)-verified lesion seemed to occupy a considerable volume of the lower spinal cord, causing only very restricted clinical sensory and motor signs. In Case 4, a cervical MRI showed a small well-circumscribed intramedullary lesion at right C2 level. All neurophysiological investigations were normal in the latter two patients (motor, tibial, and median somatosensory-evoked potentials in Case 3, and electromyography in both) except for the dSEPs. Conclusions Objectifying the presence and degree of sensory involvement in spinal disorders may be helpful for establishing diagnoses and in therapeutic decision-making. Valuable information could be provided by dSEPs in selected patients with multiple root or spinal cord involvement. PMID:24089995
Roberto, Megan E; Brumley, Michele R
The amount of postnatal experience for perinatal rats was manipulated by delivering pups one day early (postconception day 21; PC21) by cesarean delivery and comparing their motor behavior to age-matched controls on PC22 (the typical day of birth). On PC22, pups were tested on multiple measures of motor coordination: leg extension response (LER), facial wiping, contact righting, and fore- and hindlimb stepping. The LER and facial wiping provided measures of synchronous hind- and forelimb coordination, respectively, and were sensory-evoked. Contact righting also was sensory-evoked and provided a measure of axial coordination. Stepping provided a measure of alternated forelimb and hindlimb coordination and was induced with the serotonin receptor agonist quipazine. Pups that were delivered prematurely and spent an additional day in the postnatal environment showed more bilateral limb coordination during expression of the LER and facial wiping, as well as a more mature righting strategy, compared to controls. These findings suggest that experience around the time of birth shapes motor coordination and the expression of species-typical behavior in the developing rat.
Walther, Leif Erik; Cebulla, Mario
Air conducted vestibular evoked myogenic potentials (VEMP) can be elicited by various low frequency and intense sound stimuli, mainly clicks or short tone bursts (STB). Chirp stimuli are increasingly used in diagnostic audiological evaluations as an effective means to obtain acoustically evoked responses in narrowed or extended frequency ranges. We hypothesized in this study that band limited chirp stimulation, which covers the main sensitivity range of sound sensitive otolithic afferents (around 500 Hz), might be useful for application in cervical and ocular VEMP to air conduction. For this purpose we designed a chirp stimulus ranging 250-1000 Hz (up chirp). The chirp stimulus was delivered with a stimulus intensity of 100 dB nHL in normal subjects (n = 10) and patients with otolith involvement (vestibular neuritis) (n = 6). Amplitudes of the designed chirp ("CW-VEMP-chirp, 250-1000 Hz") were compared with amplitudes of VEMPs evoked by click stimuli (0.1 ms) and a short tone burst (STB, 1-2-1, 8 ms, 500 Hz). CVEMPs and oVEMPs were detectable in 9 of 10 normal individuals. Statistical evaluation in healthy patients revealed significantly larger cVEMP and oVEMP amplitudes for CW-VEMP-chirp (250-1000 Hz) stimuli. CVEMP amplitudes evoked by CW-VEMP-chirp (250-1000 Hz) showed a high stability in comparison with click and STB stimulation. CW-VEMP-chirp (250-1000 Hz) showed abnormal cVEMP and oVEMP amplitudes in patients with vestibular neuritis, with the same properties as click and STB stimulated VEMPs. We conclude that the designed CW-VEMP-chirp (250-1000 Hz) is an effective stimulus which can be further used in VEMP diagnostic. Since a chirp stimulus can be easily varied in its properties, in particular with regard to frequency, this might be a promising tool for further investigations.
Ahmadi, Maryam; Quian Quiroga, Rodrigo
We present an automatic denoising method based on the wavelet transform to obtain single trial evoked potentials. The method is based on the inter- and intra-scale variability of the wavelet coefficients and their deviations from baseline values. The performance of the method is tested with simulated event related potentials (ERPs) and with real visual and auditory ERPs. For the simulated data the presented method gives a significant improvement in the observation of single trial ERPs as well as in the estimation of their amplitudes and latencies, in comparison with a standard denoising technique (Donoho's thresholding) and in comparison with the noisy single trials. For the real data, the proposed method largely filters the spontaneous EEG activity, thus helping the identification of single trial visual and auditory ERPs. The proposed method provides a simple, automatic and fast tool that allows the study of single trial responses and their correlations with behavior.
Vayrynen, Eero; Noponen, Kai; Vipin, Ashwati; Thow, X Y; Al-Nashash, Hasan; Kortelainen, Jukka; All, Angelo
In this paper, an approach using polynomial phase chirp signals to model somatosensory evoked potentials (SEPs) is proposed. SEP waveforms are assumed as impulses undergoing group velocity dispersion while propagating along a multipath neural connection. Mathematical analysis of pulse dispersion resulting in chirp signals is performed. An automatic parameterization of SEPs is proposed using chirp models. A Particle Swarm Optimization algorithm is used to optimize the model parameters. Features describing the latencies and amplitudes of SEPs are automatically derived. A rat model is then used to evaluate the automatic parameterization of SEPs in two experimental cases, i.e., anesthesia level and spinal cord injury (SCI). Experimental results show that chirp-based model parameters and the derived SEP features are significant in describing both anesthesia level and SCI changes. The proposed automatic optimization based approach for extracting chirp parameters offers potential for detailed SEP analysis in future studies. The method implementation in Matlab technical computing language is provided online.
Saletu, B; Saletu, M; Herrmann, W M; Itil, T M
The somatosensory evoked potential (SEP) of physically and mentally healthy male subjects was recorded before as well as 4 hours after administration of one single dose of placebo, cyproterone acetate (an antiandrogen), and mesterolone (an androgen). Quantitative evaluation of drug-induced changes in SEP latencies and amplitudes, which, when plotted in terms of t-values, result in the so-called "SEP profiles", did not demonstrate any significant alterations after placebo. Contrary to this, cyproterone acetate induced systematic and significant changes characterized by a latency increase in the early peaks and latency decrease in the late peaks of the SEP. Apart from the non-significant amplitude changes, such alterations were previously described by us as typical for drugs of the anxiolytic class. Mesterolone on the other hand, produced a significant latency decrease in the early part and a latency increase in the late part of the evoked response which was found to be typical for the SEP profiles of tricyclic antidepressants. The amplitude did not show any systematic changes. Based on step-wise discriminant analysis of these data we could significantly differentiate both hormones from placebo as well as from each other. A comparative analysis of low and high doses did not yield any significant differences between the two levels. It was concluded that both test substances have psychoactive properties; whereas cyproterone acetate reveals anxiolytic qualities, mesterolone exhibits antidepressant ones. These findings are discussed from the clinical as well as from the neurophysiological point of view.
Rosengren, S M; Welgampola, M S; Colebatch, J G
Since the first description of sound-evoked short-latency myogenic reflexes recorded from neck muscles, vestibular evoked myogenic potentials (VEMPs) have become an important part of the neuro-otological test battery. VEMPs provide a means of assessing otolith function: stimulation of the vestibular system with air-conducted sound activates predominantly saccular afferents, while bone-conducted vibration activates a combination of saccular and utricular afferents. The conventional method for recording the VEMP involves measuring electromyographic (EMG) activity from surface electrodes placed over the tonically-activated sternocleidomastoid (SCM) muscles. The "cervical VEMP" (cVEMP) is thus a manifestation of the vestibulo-collic reflex. However, recent research has shown that VEMPs can also be recorded from the extraocular muscles using surface electrodes placed near the eyes. These "ocular VEMPs" (oVEMPs) are a manifestation of the vestibulo-ocular reflex. Here we describe the historical development and neurophysiological properties of the cVEMP and oVEMP and provide recommendations for recording both reflexes. While the cVEMP has documented diagnostic utility in many disorders affecting vestibular function, relatively little is known as yet about the clinical value of the oVEMP. We therefore outline the known cVEMP and oVEMP characteristics in common central and peripheral disorders encountered in neuro-otology clinics.
Dmochowski, Jacek P; Greaves, Alex S; Norcia, Anthony M
Due to their high signal-to-noise ratio (SNR) and robustness to artifacts, steady state visual evoked potentials (SSVEPs) are a popular technique for studying neural processing in the human visual system. SSVEPs are conventionally analyzed at individual electrodes or linear combinations of electrodes which maximize some variant of the SNR. Here we exploit the fundamental assumption of evoked responses--reproducibility across trials--to develop a technique that extracts a small number of high SNR, maximally reliable SSVEP components. This novel spatial filtering method operates on an array of Fourier coefficients and projects the data into a low-dimensional space in which the trial-to-trial spectral covariance is maximized. When applied to two sample data sets, the resulting technique recovers physiologically plausible components (i.e., the recovered topographies match the lead fields of the underlying sources) while drastically reducing the dimensionality of the data (i.e., more than 90% of the trial-to-trial reliability is captured in the first four components). Moreover, the proposed technique achieves a higher SNR than that of the single-best electrode or the Principal Components. We provide a freely-available MATLAB implementation of the proposed technique, herein termed "Reliable Components Analysis".
This manuscript characterizes the receptor pathways involved in pattern-evoked potential generation in rats
" NMDA and nicotinic acetylcholine receptors appear to be involved in the generation of the steady-state pattern evoked response in vivo.
" The pattern evok...
Ringelstein, Marius; Kleiter, Ingo; Ayzenberg, Ilya; Borisow, Nadja; Paul, Friedemann; Ruprecht, Klemens; Kraemer, Markus; Cohn, Eva; Wildemann, Brigitte; Jarius, Sven; Hartung, Hans-Peter; Aktas, Orhan; Albrecht, Philipp
Optic neuritis (ON) is a key feature of neuromyelitis optica (NMO). Recently, NMO patients of predominantly Afro-Brazilian origin were evaluated by visual evoked potentials (VEPs) and showed marked amplitude reductions. Here, we analyzed VEPs in a predominantly Caucasian cohort, consisting of 43 patients with definite NMO, 18 with anti-aquaporin (AQP) 4 antibody-seropositive NMO spectrum disorders and 61 matched healthy controls. We found reduced amplitudes in only 12.3%, prolonged latencies in 41.9% and a lack of response in 14.0% of NMO eyes. Delayed P100 latencies in eyes without prior ON suggested this was a subclinical affection. The data indicate heterogenous patterns in NMO, warranting further investigation.
This study examined the effect of sedation with xylazine on the brainstem auditory evoked potentials (BAEP) of cattle to determine whether sedation causes differences in waveform configuration, peak latencies, interpeak latencies, measurement time of the average count (2000 responses), and clinical signs. There were no significant differences between the sedation and no-sedation groups in peak latency of any stimulus intensities. In the sedation group, the baselines of waveforms were comparatively stabilized. Those in the no-sedation group were unstable, however, because the measurement can be influenced by excessive muscle movement. The present findings suggest that clinically, it is useful to use a sedative when measuring BAEP in cattle to control excessive movement of the cattle without influencing the peak latencies. PMID:18505193
Anlar, Omer; Akdeniz, Necmettin; Tombul, Temel; Calka, Omer; Bilgili, Serap G
Behçet's disease (BD) is a chronic, recurrent multisystem inflammatory disorder firstly described by Turkish dermatologist Dr. Hulusi Behçet in 1937. The classic triad consists of recurrent oral and genital ulcerations and uveitis. The article presents the value of visual evoked potential findings of a series of 44 patients with BD without neurological manifestations seen at the Medical Hospital in Neurology and Dermatology clinics over the past 8 years. The mean latency value of positive peak P100 in BD patients was significantly delayed compared to that of control subjects (patients's mean: 105.6 ms in right eye and 107.7 ms in left eye; control subject's mean: 101.4 ms in right eye and 101.7 ms in left eye).
Benvenuto, James; Jin, Yi; Casale, Malcolm; Lynch, Gary; Granger, Richard
Evoked response potentials (ERPs) to brief flashes of light were analyzed for constituent features that could be used to distinguish individuals with Alzheimer's disease (AD, n = 15) from matched control subjects (n = 17). Statistical k nearest-neighbor methods distinguished AD from control with a maximum sensitivity of 29% and false alarm rate of 12%. The comparable sensitivity/false-alarm values for a statistical projection pursuit method and an extended projection pursuit method, which selectively identify discriminative features for classification, were 75%/18% and 100%/6%, respectively. The results demonstrate that combinations of selected ERP time segments across different electrodes contain signal features that discriminate AD from control subjects with high sensitivity and specificity.
Plant, G T
Transient visually evoked potentials (VEPs) to sinusoidal gratings over a range of spatial frequencies have been recorded in cases of optic neuritis. The use of the response to pattern onset in addition to the response to pattern reversal extended the range to higher spatial frequencies by up to two octaves. There was an increase in VEP delay and a greater degree of discrimination from a control group at higher spatial frequencies. This finding is discussed in the light of previous reports of luminance and checkerboard VEPs in demyelinating optic nerve disease. An attempt is made to relate amplitude changes in various VEP components to contrast sensitivity measurements in this group of patients. PMID:6663312
de Tommaso, Marina
Using neurophysiological methods to explore nociceptive pathways may improve knowledge of the functional changes subtending pain processing in the different forms of headache and facial pain. Laser-evoked potentials (LEPs) are a reliable neurophysiological assay for the clinical assessment of pain syndromes. Reduced amplitude of LEPs seems to characterize trigeminal neuralgia and painful temporomandibular disorders, suggesting the neuropathic origin of pain. In tension-type headache, as well as in fibromyalgia, enhanced pericranial LEP amplitude suggests the psychogenic origin of pain. In migraine, a normal amplitude of basal LEPs with reduced habituation and altered attentive modulation seems to express a general dysfunction of cortical pain processing, which may also contribute, other than to predispose, to the persistence of migraine. LEPs may be employed in the clinical evaluation of the neurophysiological and psychophysiological aspects of pain in the different forms of headaches and facial pain to improve the therapeutic approach and provide an objective measure of treatment efficacy.
Van Voorhis, S.; Hillyard, S. A.
Visual evoked potentials (VEPs) were recorded to sequences of flashes delivered to the right and left visual fields while subjects responded promptly to designated stimuli in one field at a time (focused attention), in both fields at once (divided attention), or to neither field (passive). Three stimulus schedules were used: the first was a replication of a previous study (Eason, Harter, and White, 1969) where left- and right-field flashes were delivered quasi-independently, while in the other two the flashes were delivered to the two fields in random order (Bernoulli sequence). VEPs to attended-field stimuli were enhanced at both occipital (O2) and central (Cz) recording sites under all stimulus sequences, but different components were affected at the two scalp sites. It was suggested that the VEP at O2 may reflect modality-specific processing events, while the response at Cz, like its auditory homologue, may index more general aspects of selective attention.
Schürmann, Martin; Kolev, Vasil; Menzel, Kristina; Yordanova, Juliana
The time course of interaction between concurrently applied visual and somatosensory stimulation with respect to evoked potentials (EPs) was studied. Visual stimuli, either in the left or right hemifield, and electric stimuli to the left wrist were delivered either alone or simultaneously. Visual and somatosensory EPs were summed and compared to bimodal EPs (BiEP, response to actual combination of both modalities). Temporal coincidence of stimuli lead to sub-additive or over-additive amplitudes in BiEPs in several time windows between 75 and 275 ms. Additional effects of spatial coincidence (left wrist with left hemifield) were found between 75 and 300 ms and beyond 450 ms. These interaction effects hint at a temporo-spatial pattern of multiple brain areas participating in the process of multimodal integration.
Paulraj, M. P; Subramaniam, Kamalraj; Yaccob, Sazali Bin; Adom, Abdul H. Bin; Hema, C. R
Hypoacusis is the most prevalent sensory disability in the world and consequently, it can lead to impede speech in human beings. One best approach to tackle this issue is to conduct early and effective hearing screening test using Electroencephalogram (EEG). EEG based hearing threshold level determination is most suitable for persons who lack verbal communication and behavioral response to sound stimulation. Auditory evoked potential (AEP) is a type of EEG signal emanated from the brain scalp by an acoustical stimulus. The goal of this review is to assess the current state of knowledge in estimating the hearing threshold levels based on AEP response. AEP response reflects the auditory ability level of an individual. An intelligent hearing perception level system enables to examine and determine the functional integrity of the auditory system. Systematic evaluation of EEG based hearing perception level system predicting the hearing loss in newborns, infants and multiple handicaps will be a priority of interest for future research. PMID:25893012
Mitchell, K. W.; Wood, C. M.; Howe, J. W.; Church, W. H.; Smith, G. T.; Spencer, S. R.
Visual evoked potentials (VEPs) were elicited from 29 patients who had experienced a previous attack of acute primary angle closure glaucoma. The VEPs were shown to be abnormal in at least one of the measures (latency, amplitude, contrast threshold, or slope) in 72.4% of affected eyes, whereas only 41.4% indicated obvious optic nerve damage. It is notable that 48.1% of fellow eyes with no (known) history of acute pressure rise also showed some form of VEP abnormality. The possible pathophysiological mechanisms operating in both affected and fellow eyes are discussed. It is concluded that, despite the presence of possible artefactual influences, the results probably reflect the presence of primary angle closure glaucoma. PMID:2751978
Giffroy, Xavier; Maes, Nathalie; Albert, Adelin; Maquet, Pierre; Crielaard, Jean-Michel; Dive, Dominique
The clinical variability and complexity of multiple sclerosis (MS) challenges the individual clinical course prognostication. This study aimed to find out whether multimodal evoked potentials (EP) correlate with the motor components of multiple sclerosis functional composite (MSFCm) and predict clinically relevant motor functional deterioration. One hundred MS patients were assessed at baseline (T 0) and about 7.5 years later (T 1), with visual, somatosensory and motor EP and rated on the Expanded Disability Status Scale (EDSS) and the MSFCm, including the 9 Hole Peg Test and the Timed 25 Foot Walk (T25FW). The Spearman correlation coefficient (r S) was used to evaluate the cross-sectional and longitudinal relationship between EP Z scores and clinical findings. The predictive value of baseline electrophysiological data for clinical worsening (EDSS, 9-HPT, T25FW, MSFCm) during follow-up was assessed by logistic regression analysis. Unlike longitudinal correlations, cross-sectional correlations between EP Z scores and clinical outcomes were all significant and ranged between 0.22 and 0.67 (p < 0.05). The global EP Z score was systematically predictive of EDSS and MSFCm worsening over time (all p < 0.05). EP latency was a better predictor than amplitude, although weaker than latency and amplitude aggregation in the global EP Z score. The study demonstrates that EP numerical scores can be used for motor function monitoring and outcome prediction in patients with MS.
Srivastava, Dharmendra Kumar; Singh, Deepak; Tiwari, Bhuwan Chandra; Awasthi, Namarata; Hussain, Nuzhat
We report a rare case of benign thoracic dumb-bell tumor in the upper posterior mediastinum, which was successfully removed by posterolateral thoracotomy and foraminotomy, using intraoperative monitoring of spinal motor-evoked potentials. This technique has many advantages including minimal morbidity and mortality, a single incision, one-step complete resection with adequate exposure, spinal stabilization, avoidance of laminectomy, nerve root identification, and good predicted postoperative function.
Matsukawa, Kanji; Ishii, Kei; Kadowaki, Akito; Ishida, Tomoko; Idesako, Mitsuhiro; Liang, Nan
Our laboratory has demonstrated that the cardiomotor component of aortic baroreflex is temporarily inhibited at the onset of spontaneous motor activity in decerebrate cats, without altering carotid sinus baroreflex. A reason for this dissociation may be attributed to a difference in the responses between aortic nerve activity (AoNA) and carotid sinus nerve activity (CsNA) during spontaneous motor activity. The stimulus-response curves of AoNA and CsNA against mean arterial blood pressure (MAP) were compared between the pressor interventions evoked by spontaneous motor activity and by intravenous administration of phenylephrine or norepinephrine, in which the responses in heart rate (HR) were opposite (i.e., tachycardia vs. baroreflex bradycardia), despite the identical increase in MAP of 34-40 mmHg. In parallel to the pressor response, mean AoNA and CsNA increased similarly by 78-81 and by 88 % of the baseline control, respectively, irrespective of whether the pressor response was evoked by spontaneous motor activity or by a pharmacological intervention. The slope of the stimulus-response curve of the mean AoNA became greater (P < 0.05) during spontaneous motor activity as compared to the pharmacological intervention. On the other hand, the stimulus-response curve of the mean CsNA and its slope were equal (P > 0.05) between the two pressor interventions. Furthermore, the slopes of the stimulus-response curves of both diastolic AoNA and CsNA (defined as the minimal value within a beat) exhibited a greater increase during spontaneous motor activity. All differences in the slopes of the stimulus-response curves were abolished by restraining HR at the intrinsic cardiac frequency. In conclusion, mean mass activities of both aortic and carotid sinus baroreceptors are able to encode the beat-by-beat changes in MAP not only at rest but also during spontaneous motor activity and spontaneous motor activity-related reduction of aortic baroreceptor activity is denied
Arrubla, Jorge; Neuner, Irene; Hahn, David; Boers, Frank; Shah, N Jon
Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone. The feasibility of recording EEG at ultra-high static magnetic field up to 9.4 T was recently demonstrated and promises to be implemented soon in fMRI studies at ultra high magnetic fields. Recording visual evoked potentials are expected to be amongst the most simple for simultaneous EEG/fMRI at ultra-high magnetic field due to the easy assessment of the visual cortex. Auditory evoked P300 measurements are of interest since it is believed that they represent the earliest stage of cognitive processing. In this study, we investigate the feasibility of recording visual evoked potentials and auditory evoked P300 in a 9.4 T static magnetic field. For this purpose, EEG data were recorded from 26 healthy volunteers inside a 9.4 T MR scanner using a 32-channel MR compatible EEG system. Visual stimulation and auditory oddball paradigm were presented in order to elicit evoked related potentials (ERP). Recordings made outside the scanner were performed using the same stimuli and EEG system for comparison purposes. We were able to retrieve visual P100 and auditory P300 evoked potentials at 9.4 T static magnetic field after correction of the ballistocardiogram artefact using independent component analysis. The latencies of the ERPs recorded at 9.4 T were not different from those recorded at 0 T. The amplitudes of ERPs were higher at 9.4 T when compared to recordings at 0 T. Nevertheless, it seems that the increased amplitudes of the ERPs are due to the effect of the ultra-high field on the EEG recording system rather than alteration in the intrinsic processes that generate the electrophysiological responses.
Keller, Corey J; Honey, Christopher J; Mégevand, Pierre; Entz, Laszlo; Ulbert, Istvan; Mehta, Ashesh D
The cerebral cortex forms a sheet of neurons organized into a network of interconnected modules that is highly expanded in humans and presumably enables our most refined sensory and cognitive abilities. The links of this network form a fundamental aspect of its organization, and a great deal of research is focusing on understanding how information flows within and between different regions. However, an often-overlooked element of this connectivity regards a causal, hierarchical structure of regions, whereby certain nodes of the cortical network may exert greater influence over the others. While this is difficult to ascertain non-invasively, patients undergoing invasive electrode monitoring for epilepsy provide a unique window into this aspect of cortical organization. In this review, we highlight the potential for cortico-cortical evoked potential (CCEP) mapping to directly measure neuronal propagation across large-scale brain networks with spatio-temporal resolution that is superior to traditional neuroimaging methods. We first introduce effective connectivity and discuss the mechanisms underlying CCEP generation. Next, we highlight how CCEP mapping has begun to provide insight into the neural basis of non-invasive imaging signals. Finally, we present a novel approach to perturbing and measuring brain network function during cognitive processing. The direct measurement of CCEPs in response to electrical stimulation represents a potentially powerful clinical and basic science tool for probing the large-scale networks of the human cerebral cortex.
Keller, Corey J.; Honey, Christopher J.; Mégevand, Pierre; Entz, Laszlo; Ulbert, Istvan; Mehta, Ashesh D.
The cerebral cortex forms a sheet of neurons organized into a network of interconnected modules that is highly expanded in humans and presumably enables our most refined sensory and cognitive abilities. The links of this network form a fundamental aspect of its organization, and a great deal of research is focusing on understanding how information flows within and between different regions. However, an often-overlooked element of this connectivity regards a causal, hierarchical structure of regions, whereby certain nodes of the cortical network may exert greater influence over the others. While this is difficult to ascertain non-invasively, patients undergoing invasive electrode monitoring for epilepsy provide a unique window into this aspect of cortical organization. In this review, we highlight the potential for cortico-cortical evoked potential (CCEP) mapping to directly measure neuronal propagation across large-scale brain networks with spatio-temporal resolution that is superior to traditional neuroimaging methods. We first introduce effective connectivity and discuss the mechanisms underlying CCEP generation. Next, we highlight how CCEP mapping has begun to provide insight into the neural basis of non-invasive imaging signals. Finally, we present a novel approach to perturbing and measuring brain network function during cognitive processing. The direct measurement of CCEPs in response to electrical stimulation represents a potentially powerful clinical and basic science tool for probing the large-scale networks of the human cerebral cortex. PMID:25180306
Yorifuji, Takashi; Murata, Katsuyuki; Bjerve, Kristian S.; Choi, Anna L; Weihe, Pal; Grandjean, Philippe
Prenatal exposure to methylmercury can cause both neurobehavioral deficits and neurophysiological changes. However, evidence of neurotoxic effects within the visual nervous system is inconsistent, possibly due to incomplete statistical adjustment for beneficial nutritional factors. We evaluated the effect of prenatal methylmercury exposure on visual evoked potential (VEP) latencies in Faroese children with elevated prenatal methylmercury exposure. A cohort of 182 singleton term births was assembled in the Faroe Islands during 1994–1995. At age 7 years, VEP tracings were obtained from 139 cohort subjects after exclusion of subjects with abnormal vision conditions. We used multiple regression analysis to evaluate the association of mercury concentrations in cord blood and maternal hair at parturition with VEP latencies after adjustment for potential confounders that included the cord-serum phospholipid concentration of n-3 polyunsaturated fatty acids (PUFAs) and the duration of breastfeeding. Unadjusted correlations between mercury exposure and VEP latencies were equivocal. Multiple regression models showed that increased mercury concentrations, especially in maternal hair, were associated with delayed latencies for VEP peak N145. After covariate adjustment, a delay of 2.22 ms (p=0.02) was seen for each doubling of the mercury concentration in maternal hair. In agreement with neuropsychological findings, the present study suggests that prenatal methylmercury exposure may have an adverse effect on VEP findings despite the absence of clinical toxicity to the visual system. However, this association was apparent only after adjustment for n-3 PUFA status. PMID:23548974
de Tommaso, Marina; Franco, Giovanni; Ricci, Katia; Montemurno, Anna; Sciruicchio, Vittorio
Pain was rarely studied in Huntington's disease (HD). We presently aimed to extend our previous study on pain pathways functions by laser evoked potentials (LEPs) to a larger cohort of early unmedicated HD patients and a small group of presymptomatic HD (PHD) subjects. Forty-two early HD patients, 10 PHD patients, and 64 controls were submitted to LEPs by right-hand stimulation. Two series of 30 laser stimuli were delivered, and artifact-free responses were averaged. The N1, N2, and P2 latencies were significantly increased and the N2P2 amplitude significantly reduced in HD patients compared to controls. In the HD group, the LEPs abnormalities correlated with functional decline. PHD subjects showed a slight and insignificant increase in LEPs latencies, which was inversely correlated with the possible age of HD clinical onset. Data of the present study seem to suggest that the functional state of nociceptive pathways as assessed by LEPs may be a potential biomarker of disease onset and progression. The assessment of pain symptoms in premanifest and manifest HD may also open a new scenario in terms of subtle disturbances of pain processing, which may have a role in the global burden of the disease. PMID:27087746
An, Shuming; Kilb, Werner; Luhmann, Heiko J
Self-generated neuronal activity originating from subcortical regions drives early spontaneous motor activity, which is a hallmark of the developing sensorimotor system. However, the neural activity patterns and role of primary motor cortex (M1) in these early movements are still unknown. Combining voltage-sensitive dye imaging (VSDI) with simultaneous extracellular multielectrode recordings in postnatal day 3 (P3)-P5 rat primary somatosensory cortex (S1) and M1 in vivo, we observed that tactile forepaw stimulation induced spindle bursts in S1 and gamma and spindle bursts in M1. Approximately 40% of the spontaneous gamma and spindle bursts in M1 were driven by early motor activity, whereas 23.7% of the M1 bursts triggered forepaw movements. Approximately 35% of the M1 bursts were uncorrelated to movements and these bursts had significantly fewer spikes and shorter burst duration. Focal electrical stimulation of layer V neurons in M1 mimicking physiologically relevant 40 Hz gamma or 10 Hz spindle burst activity reliably elicited forepaw movements. We conclude that M1 is already involved in somatosensory information processing during early development. M1 is mainly activated by tactile stimuli triggered by preceding spontaneous movements, which reach M1 via S1. Only a fraction of M1 activity transients trigger motor responses directly. We suggest that both spontaneously occurring and sensory-evoked gamma and spindle bursts in M1 contribute to the maturation of corticospinal and sensorimotor networks required for the refinement of sensorimotor coordination.
Gürses, Nadide; Temuçin, Cağri Mesut; Lay Ergün, Eser; Ertuğrul, Aygün; Ozer, Suzan; Demir, Başaran
Conversion disorder is defined as the presence of functional impairment in motor, sensory or neurovegetative systems which cannot be explained by a general medical condition. Although the diagnostic systems emphasize the absence of an organic basis for the dysfunction in conversion disorder, there has been a growing interest in the specific functional brain correlates of conversion symptoms in recent years, particularly by examining neuroimaging and neurophysiological measures. In this case report, regional cerebral blood flow changes and evoked potentials of a patient with conversion symptoms are presented. Somatosensory evoked potentials (SEP) of this patient with conversion disorder who had signs of movement disorder revealed that the latency to N20, P 25 waves were in normal limits while the amplitudes of the P25 and N33 components were extremely high (giant SEP). Regional cerebral blood flow assessment revealed hypoperfusion in the left parietal and temporal lobes of the brain. Three months after the first assessment, the control scans showed that the left parietal hypoperfusion disappeared while the left temporal hypoperfusion was still present. The following SEP evaluations which were repeated twice in three months intervals after the initial recordings, showed the persistence of the abnormalities in somatosensorial measures. The neurophysiological and neuroimaging findings in conversion disorder were reviewed and the results of the evaluations of this case were discussed in this article.
Theta burst stimulation (TBS) of the cerebellum, a potential therapy for neurological disease, can modulate corticospinal excitability via the dentato-thalamo-cortical pathway, but it is uncertain whether its effects are mediated via inhibitory or facilitatory networks. The aim of this study was to investigate the effects of 30Hz cerebellar TBS on the N100 waveform of the TMS-evoked potential (TEP), a marker of intracortical GABAB-mediated inhibition. 16 healthy participants (aged 18–30 years; 13 right handed and 3 left handed) received 30Hz intermittent TBS (iTBS), continuous TBS (cTBS) or sham stimulation over the right cerebellum, in three separate sessions. The first 8 participants received TBS at a stimulus intensity of 80% of active motor threshold (AMT), while the remainder received 90% of AMT. Motor evoked potentials (MEP) and TEP were recorded before and after each treatment, by stimulating the first dorsal interosseus area of the left motor cortex. Analysis of the 13 right handed participants showed that iTBS at 90% of AMT increased the N100 amplitude compared to sham and cTBS, without significantly altering MEP amplitude. cTBS at 80% of active motor threshold decreased the N100 amplitude and cTBS overall reduced resting MEP amplitude. The study demonstrates effects of 30Hz cerebellar TBS on inhibitory cortical networks that may be useful for treatment of neurological conditions associated with dysfunctional intracortical inhibition. PMID:26529225
Fan, Bi; Li, Han-Xiong; Hu, Yong
Somatosensory evoked potential (SEP) is a useful, noninvasive technique widely used for spinal cord monitoring during surgery. One of the main indicators of a spinal cord injury is the drop in amplitude of the SEP signal in comparison to the nominal baseline that is assumed to be constant during the surgery. However, in practice, the real-time baseline is not constant and may vary during the operation due to nonsurgical factors, such as blood pressure, anaesthesia, etc. Thus, a false warning is often generated if the nominal baseline is used for SEP monitoring. In current practice, human experts must be used to prevent this false warning. However, these well-trained human experts are expensive and may not be reliable and consistent due to various reasons like fatigue and emotion. In this paper, an intelligent decision system is proposed to improve SEP monitoring. First, the least squares support vector regression and multi-support vector regression models are trained to construct the dynamic baseline from historical data. Then a control chart is applied to detect abnormalities during surgery. The effectiveness of the intelligent decision system is evaluated by comparing its performance against the nominal baseline model by using the real experimental datasets derived from clinical conditions.
Nachtigall, Paul E; Supin, Alexander Y; Amundin, Mats; Röken, Bengt; Møller, Thorsten; Mooney, T Aran; Taylor, Kristen A; Yuen, Michelle
While there has been recent concern about the effects of sound on marine mammals, including polar bears, there are no data available measuring the hearing of any bear. The in-air hearing of three polar bears was measured using evoked auditory potentials obtained while tone pips were played to three individually anaesthetized bears at the Kolmården Djurpark. Hearing was tested in half-octave steps from 1 to 22.5 kHz. Measurements were not obtainable at 1 kHz and best sensitivity was found in the range from 11.2-22.5 kHz. Considering the tone pips were short and background noise measurements were available, absolute measurements were estimated based on an assumed mammalian integration time of 300 ms. These data show sensitive hearing in the polar bear over a wide frequency range and should cause those concerned with the introduction of anthropogenic noise into the polar bear's environment to operate with caution.
Georgiadis, Stefanos D.; Ranta-aho, Perttu O.; Tarvainen, Mika P.; Karjalainen, Pasi A.
It is a challenge in evoked potential (EP) analysis to incorporate prior physiological knowledge for estimation. In this paper, we address the problem of single-channel trial-to-trial EP characteristics estimation. Prior information about phase-locked properties of the EPs is assesed by means of estimated signal subspace and eigenvalue decomposition. Then for those situations that dynamic fluctuations from stimulus-to-stimulus could be expected, prior information can be exploited by means of state-space modeling and recursive Bayesian mean square estimation methods (Kalman filtering and smoothing). We demonstrate that a few dominant eigenvectors of the data correlation matrix are able to model trend-like changes of some component of the EPs, and that Kalman smoother algorithm is to be preferred in terms of better tracking capabilities and mean square error reduction. We also demonstrate the effect of strong artifacts, particularly eye blinks, on the quality of the signal subspace and EP estimates by means of independent component analysis applied as a prepossessing step on the multichannel measurements. PMID:18288257
Snyder, E.; Hillyard, S. A.
Occasional shifts of loudness in a repetitive train of clicks elicited a late-positive wave (P3a) in nonattending subjects which peaked at a mean latency of 258 msec and had a frontocentral scalp distribution; P3a was typically preceded by an 'N2' component at 196 msec. The P3a wave was distinguishable from the longer-latency (378 msec) parietocentrally distributed 'P3b' wave that was evoked by the same stimulus in an actively attending subject, thus confirming the findings of Squires et al. (1975). Infrequently presented single sounds did not produce large or consistent N2-P3a components; the critical condition for the generation of an N2-P3a wave seemed to be that the infrequent sounds represent a deviation (intensity increment or decrement) from a repetitive background. Furthermore, increasing the repetition rate of the background clicks drastically reduced N1-P2 amplitude but had little effect on the amplitude of N2-P3a. This suggests that N2-P3a is not simply a delayed N1-P2 'vertex potential', but rather reflects the operation of a 'mismatch' detector, which registers deviations from an ongoing auditory background.
McGlone, L; Mactier, H; Hamilton, R; Bradnam, M S; Boulton, R; Borland, W; Hepburn, M; McCulloch, D L
We investigated the effects of maternal drug misuse on neonatal visual evoked potentials (VEPs). Flash VEPs were recorded within 4 days of birth from 21 term infants of mothers misusing drugs and prescribed substitute methadone and 20 controls. Waveforms were classified as typical, atypical, immature or non-detectable, and amplitude and latencies were measured. VEPs from drug-exposed infants were less likely to be of typical waveform and more likely to be immature or non-detectable (p<0.01) than those of control infants. They were also smaller in amplitude (median 10.8 vs 24.4 microV, p<0.001). VEPs of drug-exposed infants had matured after 1 week but remained of lower amplitude than VEPs of newborn controls (p<0.01) and were non-detectable in 15%. Flash VEPs differ between maternal drug-exposed and non-drug-exposed newborns. Future research should address the specific effects of maternal methadone and/or other illicit drug misuse on infant VEPs, and associations between neonatal VEPs and subsequent visual development.
Hayashi, Hironobu; Kawaguchi, Masahiko
In neurosurgical procedures that may cause visual impairment in the intraoperative period, the monitoring of flash visual evoked potential (VEP) is clinically used to evaluate visual function. Patients are unconscious during surgery under general anesthesia, making flash VEP monitoring useful as it can objectively evaluate visual function. The flash stimulus input to the retina is transmitted to the optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiation (geniculocalcarine tract), and visual cortical area, and the VEP waveform is recorded from the occipital region. Intraoperative flash VEP monitoring allows detection of dysfunction arising anywhere in the optic pathway, from the retina to the visual cortex. Particularly important steps to obtain reproducible intraoperative flash VEP waveforms under general anesthesia are total intravenous anesthesia with propofol, use of retinal flash stimulation devices using high-intensity light-emitting diodes, and a combination of electroretinography to confirm that the flash stimulus has reached the retina. Relatively major postoperative visual impairment can be detected by intraoperative decreases in the flash VEP amplitude.
Korres, Stavros; Gkoritsa, Eleni; Giannakakou-Razelou, Dimitra; Yiotakis, Ioannis; Riga, Maria; Nikolpoulos, Thomas P.
Summary Background The probable cause of Benign Paroxysmal Positional Vertigo (BPPV) is a degeneration of the oto lithic organs (utricle and saccule). The aim of the study is to find possible alterations in Vestibular Evoked Myogenic Potentials (VEMP) recordings in BPPV patients, because the saccule is part of the VEMP pathway. Material/Methods 27 BPPV patients (24 unilateral and 3 bilateral) aged 20 to 70 years and 30 healthy age matched controls. BPPV was diagnosed by the upbeating geotropic nystagmus found in the supine position with the head overextended towards one side. The subjects were investigated with pure tone audiometry, bi-thermal caloric test with electronystagmographic (ENG) recording, and VEMP recording. Results P1 latency and N1 latency did not present any statistical difference between control ears and affected ears of the BPPV population. The percentage of abnormal VEMP in the BPPV population was statistically higher than in the control ears (p<0.005). No significant relationship could be shown between the occurrence of Canal Paresis and abnormal VEMP. No relationship was found between the side (right or left ear) where BPPV appeared clinically and the side where abnormal VEMP was registered. Conclusions BPPV is a clinical entity associated with increased occurrence of abnormal VEMP recordings, possibly due to degeneration of the saccular macula, which is part of the neural VEMP pathway. PMID:21169909
Biaggi, Fabio; Di Ianni, Francesco; Dodi, Pier Luigi; Quintavalla, Fausto
The objective of this pilot study was to evaluate the feasibility of Flash Visual Evoked Potentials (FVEPs) testing in birds of prey in a clinical setting and to describe the protocol and the baseline data for normal vision in this species. FVEP recordings were obtained from 6 normal adult birds of prey: n. 2 Harris’s Hawks (Parabuteo unicinctus), n. 1 Lanner Falcon (Falco biarmicus), n. 2 Gyrfalcons (Falco rusticolus) and n. 1 Saker Falcon (Falco cherrug). Before carrying out VEP tests, all animals underwent neurologic and ophthalmic routine examination. Waveforms were analysed to identify reproducible peaks from random variation of baseline. At least three positive and negative peaks were highlighted in all tracks with elevated repeatability. Measurements consisted of the absolute and relative latencies of these peaks (P1, N1, P2, N2, P3, and N3) and their peak-to-peak amplitudes. Both the peak latency and wave morphology achieved from normal animals were similar to those obtained previously in other animal species. This test can be easily and safely performed in a clinical setting in birds of prey and could be useful for an objective assessment of visual function. PMID:27547536
Sungur, Gulten; Yakin, Mehmet; Unlu, Nurten; Balta, Oyku Bezen; Ornek, Firdevs
Purpose. To assess the different check sizes of pattern visual evoked potential (PVEP) in diabetic patients without retinopathy according to HbA1c levels and diabetes duration. Methods. Fifty-eight eligible patients with type 2 diabetes mellitus and 26 age- and sex-matched healthy controls were included in the study. Only the right eye of each patient was analyzed. All of the patients underwent a comprehensive ophthalmic examination, and the PVEPs were recorded. Results. There was a statistically significant difference in P100 latency in 1-degree check size and in N135 latency in 2-degree check size between controls and patient groups which have different HbA1c levels. There were statistically significant, positive, and weak correlations with diabetes duration and P100 latency in 7-minute and 15-minute check sizes and N135 latency in 15-minute check size. Conclusions. It was showed that there were prolongations in P100 latency only in 1-degree check size and in N135 only in 2-degree check size in diabetic patients without retinopathy. There was statistically significant correlation between diabetes duration and P100 and N135 latencies in different check sizes. PMID:28392940
Hobday, David I; Hobson, Anthony R; Sarkar, Sanchoy; Furlong, Paul L; Thompson, David G; Aziz, Qasim
The rectum has a unique physiological role as a sensory organ and differs in its afferent innervation from other gut organs that do not normally mediate conscious sensation. We compared the central processing of human esophageal, duodenal, and rectal sensation using cortical evoked potentials (CEP) in 10 healthy volunteers (age range 21-34 yr). Esophageal and duodenal CEP had similar morphology in all subjects, whereas rectal CEP had two different but reproducible morphologies. The rectal CEP latency to the first component P1 (69 ms) was shorter than both duodenal (123 ms; P = 0.008) and esophageal CEP latencies (106 ms; P = 0.004). The duodenal CEP amplitude of the P1-N1 component (5.0 microV) was smaller than that of the corresponding esophageal component (5.7 microV; P = 0.04) but similar to that of the corresponding rectal component (6.5 microV; P = 0.25). This suggests that rectal sensation is either mediated by faster-conducting afferent pathways or that there is a difference in the orientation or volume of cortical neurons representing the different gut organs. In conclusion, the physiological and anatomic differences between gut organs are reflected in differences in the characteristics of their afferent pathways and cortical processing.
In neurosurgical procedures that may cause visual impairment in the intraoperative period, the monitoring of flash visual evoked potential (VEP) is clinically used to evaluate visual function. Patients are unconscious during surgery under general anesthesia, making flash VEP monitoring useful as it can objectively evaluate visual function. The flash stimulus input to the retina is transmitted to the optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiation (geniculocalcarine tract), and visual cortical area, and the VEP waveform is recorded from the occipital region. Intraoperative flash VEP monitoring allows detection of dysfunction arising anywhere in the optic pathway, from the retina to the visual cortex. Particularly important steps to obtain reproducible intraoperative flash VEP waveforms under general anesthesia are total intravenous anesthesia with propofol, use of retinal flash stimulation devices using high-intensity light-emitting diodes, and a combination of electroretinography to confirm that the flash stimulus has reached the retina. Relatively major postoperative visual impairment can be detected by intraoperative decreases in the flash VEP amplitude. PMID:28367282
Ladich, Friedrich; Wysocki, Lidia Eva
The auditory evoked potential (AEP) recording technique has proved to be a very versatile and successful approach in studying auditory sensitivities in fishes. The AEP protocol introduced by Kenyon, Ladich and Yan in 1998 using an air speaker with the fish positioned at the water surface gave auditory thresholds in goldfish very close to behavioural values published before. This approach was subsequently modified by several laboratories, raising the question whether speaker choice (air vs. underwater) or the position of subjects affect auditory threshold determination. To answer these questions, the hearing specialist Carassius auratus was measured using an air speaker, an underwater speaker and alternately positioning the fish directly at or 5cm below the water surface. Mean hearing thresholds obtained using these 4 different setups varied by 5.6dB, 3.7dB and 4dB at 200Hz, 500Hz and 1000Hz, respectively. Accordingly, pronounced differences in AEP thresholds in goldfish measured in different laboratories reflect other factors than speaker used and depth of the test subjects, namely variations in threshold definition, background noise, population differences, or calibration errors.
Harland, Malte M.; Marshall, Arvle E.; Belknap, Ellen B.
Abstract Deafness was confirmed in a blue-eyed, 3-year-old, overo paint horse by brainstem auditory evoked potential. Congenital inherited deafness associated with lack of facial pigmentation was suspected. Assessment of hearing should be considered, especially in paint horses, at the time of pre-purchase examination. Brainstem auditory evoked potential assessment is well tolerated and accurate. PMID:16579041
Polo, A; Dossi, M; Fiaschi, A; Zanette, G; Rizzuto, N
Objectives: To investigate the origin of juvenile muscle atrophy of the upper limbs (Hirayama's disease, a type of cervical myelopathy of unknown origin). Subjects: Eight male patients were studied; data from 10 normal men were used as control. Methods: Median and ulnar nerve somatosensory evoked potentials (SEP) were recorded. Brachial plexus potentials at Erb's point (EP), dorsal horn responses (N13), and subcortical (P14) and cortical potentials (N20) were evaluated. Tibial nerve SEP and motor evoked potentials (MEP) were also recorded from scalp and spinal sites to assess posterior column and pyramidal tract conduction, respectively. Results: The most important SEP findings were: a very substantial attenuation of both the EP potentials and the N13 spinal responses; normal amplitude of the scalp N20; and normal latency of the individual peaks (EP-N9-N13-P14-N20). Although both nerves were involved, abnormalities in response to median nerve stimulation were more significant than those in response to ulnar nerve stimulation. There was little correlation between the degree of alterations observed and the clinical state. Latencies of both spinal and cortical potentials were normal following tibial nerve stimulation. The mean latency of cervical MEP and the central conduction time from the thenar eminence were slightly but significantly longer in patients than in controls. Conclusions: The findings support the hypothesis that this disease, which is clinically defined as a focal spinal muscle atrophy of the upper limb, may also involve the sensory system; if traumatic injury caused by stretching plays a role in the pathogenesis, the damage cannot be confined to the anterior horn of the spinal cord. PMID:12700306
Laird, James H; Parker, John L
Electrical stimulation of the spinal cord is used for pain relief, and is in use for hundreds of thousands of cases of chronic neuropathic pain. In spinal cord stimulation (SCS), an array of electrodes is implanted in the epidural space of the cord, and electrical currents are used to stimulate nearby nerve fibers, believed to be in the dorsal columns of the cord. Despite the long history of SCS for pain, stretching over 30 years, its underlying mechanisms are poorly understood, and the therapy has evolved very little in this time. Recent work has resulted in the ability to record complex compound action potential waveforms during therapy. These waveforms reflect the neural activity evoked by the therapeutic stimulation, and reveal information about the underlying physiological processes. We aim to simulate these processes to the point of reproducing these recordings. We establish a hybrid model of SCS, composed of a three dimensional electrical model and a neural model. The 3D model describes the geometry of the spinal regions under consideration, and the electric fields that result from any flow of current within them. The neural model simulates the behaviour of spinal nerve fibers, which are the target tissues of the therapy. The combination of these two models is used to predict which fibers may be recruited by a given stimulus, as well as to predict the ensuing recorded waveforms. The model is shown to reproduce major features of spinal compound action potentials, such as threshold and propagation behaviour, which have been observed in experiments. The model's coverage of processes from stimulation to recording allows it to be compared side-by-side with actual experimental data, and will permit its refinement to a substantial level of accuracy.
Westhofen, M; Herberhold, C; Thayssen, G; Jend, H H
This is the first report to be published on olfactory evoked potentials in patients with well-defined lesions of the central nervous system and the trigeminal nerve. Absence of olfactory evoked potentials is seen in post-central and parietotemporal lesions. The first peak of the so-called olfactory evoked twin potential is absent in lesions of the basal nuclei and sectioning of the trigeminal or ophthalmic nerve, whereas there is no second peak in subcortico-frontal and cortico-temporal lesions. Tumours of the corpus callosum and sectioning of the maxillary and mandibular nerves do not disturb the olfactory evoked potentials. The anatomically different localisation and the functional synergism of the olfactory and trigeminal systems in the perception of odours and the processing of olfactory evoked potentials are pointed out.
Silinsky, E M; Watanabe, M; Redman, R S; Qiu, R; Hirsh, J K; Hunt, J M; Solsona, C S; Alford, S; MacDonald, R C
1. The requirement for extracellular Ca2+ in the process of evoked acetylcholine (ACh) release by nerve impulses was tested at endplates in frog skeletal muscle. Ca(2+)-containing lipid vesicles (Ca2+ liposomes) were used to elevate cytoplasmic Ca2+ concentrations under conditions in which Ca2+ entry from the extracellular fluid was prevented. 2. In an extracellular solution containing no added Ca2+ and 1 mM Mg2+ ('Ca(2+)-free' solution), Ca2+ liposomes promoted the synchronous release of ACh quanta, reflected electrophysiologically as endplate potentials (EPPs), in response to temporally isolated nerve impulses. 3. Motor nerve stimulation generated EPPs during superfusion with Ca2+ liposomes in Ca(2+)-free solutions containing the Ca2+ channel blocker Co2+ (1 mM), and the Ca2+ chelator EGTA (2 mM). As a physiological control for Ca2+ leakage from the liposomes to the extracellular fluid, the effect of Ca2+ liposomes on asynchronous evoked ACh release mediated by Ba2+ was examined. In contrast to the effects of 0.2-0.3 mM extracellular Ca2+, which generated EPPs but antagonized Ba(2+)-mediated asynchronous ACh release, Ca2+ liposomes generated EPPs but did not reduce asynchronous release mediated by Ba2+. The effects of Ca2+ liposomes were thus not due to leakage of Ca2+ from the liposome to the extracellular fluid. 4. Morphological studies using fluorescently labelled liposomes in conjunction with a confocal microscope demonstrate that lipid is transferred from the liposomes to nerve endings and liposomal contents are delivered to the nerve terminal cytoplasm. 5. The results suggest that when intracellular Ca2+ is elevated using liposomes as a vehicle, evoked ACh release can occur in the absence of Ca2+ entry via Ca2+ channels. Images Figure 5 Figure 6 PMID:7738845
Storozhuk, V M; Stezhka, V V; Ivanova, S F
In chronic experiments on cats the influence of iontophoretic application of adrenomimetic ephedrin and beta-adrenoblocker obsidan (propranolol) on motor cortex neuron reactions following conditional stimuli was investigated under instrumental placing reaction. It was shown for a majority of neurons that the background impulse activity and reactions following conditional stimulation were suppressed by the influence of ephedrin and on the contrary were increased by obsidan application. It is concluded that there exists a consistent tonic suppressing influence of the noradrenergic system on background and evoked cortical neurons impulse activity in the natural state. It is supposed that noradrenergic influence temporal increase may serve as an important link in mechanisms of external inhibition during stress situations, aversive effects, and distractive external excitations.
Anzellotti, Francesca; Onofrj, Marco; Bonanni, Laura; Saracino, Antonio; Franciotti, Raffaella
Enlarged cortical components of somatosensory evoked potentials (giant SEPs) recorded by electroencephalography (EEG) and abnormal somatosensory evoked magnetic fields (SEFs) recorded by magnetoencephalography (MEG) are observed in the majority of patients with cortical myoclonus (CM). Studies on simultaneous recordings of SEPs and SEFs showed that generator mechanism of giant SEPs involves both primary sensory and motor cortices. However the generator sources of giant SEPs have not been fully understood as only one report describes clearly giant SEPs following lower limb stimulation. In our study we performed a combined EEG-MEG recording on responses elicited by electric median and tibial nerve stimulation in a patient who developed consequently to methyl bromide intoxication CM with giant SEPs to median and tibial nerve stimuli. SEPs wave shapes were identified on the basis of polarity-latency components (e.g. P15-N20-P25) as defined by earlier studies and guidelines. At EEG recording, the SEP giant component did not appear in the latency range of the first cortical component for median nerve SEP (N20), but appeared instead in the range of the P37 tibial nerve SEP, which is currently identified as the first cortical component elicited by tibial nerve stimuli. Our MEG and EEG SEPs recordings also showed that components in the latency range of P37 were preceded by other cortical components. These findings suggest that lower limb P37 does not correspond to upper limb N20. MEG results confirmed that giant SEFs are the second component from both tibial (N43m-P43m) and median (N27m-P27m) nerve stimulation. MEG dipolar sources of these giant components were located in the primary sensory and motor area.
Sagara, Yoshiko; Fuse, Nobuo; Seimiya, Motohiko; Yokokura, Syunji; Watanabe, Kei; Nakazawa, Toru; Kurusu, Masayuki; Seki, Takashi; Tamai, Makoto
Visual evoked potential (VEP) testing is used frequently and is an important ophthalmologic physiological test to examine visual functions objectively. The VEP is a complicated waveform consisting of negative waveform named N75 and N135, and positive waveform named P100. Delayed P100 latency and greatly attenuated amplitude on VEP are known characteristics for diagnosing optic nerve disease. Acupuncture has been used to treat wide clinical symptoms with minimal side effects. The confirmation of the efficacy of acupuncture generally relies on subjective symptoms. There is not much scientific evidence supporting the acupuncture treatments for eye diseases up to today. However, the VEP test can evaluate objectively and numerically the efficacy of the treatment by the acupuncture. We analyzed 19 healthy subjects (38 eyes). The P100 latencies in the group of less than 101.7 msec (total average) before acupuncture stimulations were not different than those after treatment (98.2 +/- 3.0 msec, 98.2 +/- 4.0 msec, respectively, p = 0.88, n = 17), but the latencies in those subjects with longer or equal to 101.7 msec were statistically different after acupuncture (104.6 +/- 2.8 msec, 101.9 +/- 3.7 msec, respectively, p = 0.006, n = 21). These results show that the acupuncture stimulation contributes to the P100 latencies of pattern reversal (PR)-VEP to some subjects who have delayed latencies, and this electrophysiological method is a valuable technique in monitoring the effectiveness of acupuncture therapy in the improvements of visual functions. The purpose of this study is to evaluate the physiological effects by acupuncture stimulations using PR-VEP in normal subjects.
Billings, Curtis J; McMillan, Garnett P; Penman, Tina M; Gille, Sun Mi
Speech perception in background noise is a common challenge across individuals and health conditions (e.g., hearing impairment, aging, etc.). Both behavioral and physiological measures have been used to understand the important factors that contribute to perception-in-noise abilities. The addition of a physiological measure provides additional information about signal-in-noise encoding in the auditory system and may be useful in clarifying some of the variability in perception-in-noise abilities across individuals. Fifteen young normal-hearing individuals were tested using both electrophysiology and behavioral methods as a means to determine (1) the effects of signal-to-noise ratio (SNR) and signal level and (2) how well cortical auditory evoked potentials (CAEPs) can predict perception in noise. Three correlation/regression approaches were used to determine how well CAEPs predicted behavior. Main effects of SNR were found for both electrophysiology and speech perception measures, while signal level effects were found generally only for speech testing. These results demonstrate that when signals are presented in noise, sensitivity to SNR cues obscures any encoding of signal level cues. Electrophysiology and behavioral measures were strongly correlated. The best physiological predictors (e.g., latency, amplitude, and area of CAEP waves) of behavior (SNR at which 50 % of the sentence is understood) were N1 latency and N1 amplitude measures. In addition, behavior was best predicted by the 70-dB signal/5-dB SNR CAEP condition. It will be important in future studies to determine the relationship of electrophysiology and behavior in populations who experience difficulty understanding speech in noise such as those with hearing impairment or age-related deficits.
Di Stefano, G; La Cesa, S; Leone, C; Pepe, A; Galosi, E; Fiorelli, M; Valeriani, M; Lacerenza, M; Pergolini, M; Biasiotta, A; Cruccu, G; Truini, A
Although the most widely agreed neurophysiological tool for investigating small fibre damage is laser evoked potential (LEP) recording, no study has documented its diagnostic accuracy. In this clinical, neurophysiological and skin biopsy study we collected age-corrected LEP normative ranges, verified the association of LEPs with pinprick sensory disturbances in the typical diabetic mixed-fibre polyneuropathy and assessed the sensitivity and specificity of LEPs in diabetic small-fibre neuropathy.From 288 LEP recordings from the face, hand and foot in 73 healthy subjects we collected age-corrected normative ranges for LEPs. We then selected 100 patients with mixed-fibre diabetic neuropathy and 25 patients with possible small-fibre diabetic neuropathy. In the 100 patients with mixed-fibre neuropathy we verified how LEP abnormalities were associated with clinically evident pinprick sensory disturbances. In the 25 patients with possible pure small-fibre neuropathy, using the skin biopsy for assessing the intraepidermal nerve fibre density, as a reference standard, we calculated LEP sensitivity and specificity.In healthy participants, age strongly influenced normative ranges for all LEP variables. By applying age-corrected normative ranges for LEPs, we found that LEPs were strongly associated with pinprick sensory disturbances. In relation to the skin biopsy findings, LEPs yielded 78% sensitivity and 81% specificity in the diagnosis of diabetic small-fibre neuropathy.Our study, providing age-corrected normative ranges for the main LEP data and their diagnostic accuracy, helps to make LEPs more reliable as a clinical diagnostic tool, and proposes this technique as a less invasive alternative to skin biopsy for diagnosing diabetic small-fibre neuropathy.
Taylor, Anna M; Enoka, Roger M
The study used a computational approach to identify combinations of synaptic input timing and strength superimposed on a variety of active dendritic conductances that could evoke similar levels of motor unit synchronization in model motor neurons. Two motor neurons with low recruitment thresholds but different passive properties were modeled using GENESIS software. The timing and strength of synaptic inputs and the density of dendritic ion channels were optimized with a genetic algorithm to produce a set of target discharge times. The target times were taken from experimental recordings made in a human subject and had the synchronization characteristics that are commonly observed in hand muscles. The main finding was that the two parameters with the highest association to output synchrony were the ratio of inward-to-outward ionic conductances (r = 0.344; P = 0.003) and the degree of correlation in inhibitory inputs (r = 0.306; P = 0.009). Variation in the amount of correlation in the excitatory input was not positively correlated with variation in output synchrony. Further, the variability in discharge rate of the model neurons was positively correlated with the density of N -type calcium channels in the dendritic compartments (r = 0.727; P < 0.001 and r = 0.533; P < 0.001 for the two cells). This result suggests that the experimentally observed correlation between discharge variability and synchronization is caused by an increase in fast inward ionic conductances in the dendrites. Given the moderate level of correlation between output synchrony and each of the model parameters, especially at moderate levels of synchrony (E < 0.09 and CIS < 1.0), the results suggest caution in ascribing mechanisms to observations of motor unit synchronization.
Neagu, Bogdan; Tsang, Eric; Mazzella, Filomena; Hamani, Clement; Moro, Elena; Hodaie, Mojgan; Lozano, Andres M; Chen, Robert
The effects of subthalamic nucleus (STN) stimulation on the pedunculopontine nucleus area (PPNR) evoked activities were examined in two patients with Parkinson's disease. The patients had previously undergone bilateral STN deep brain stimulation (DBS) and subsequently received unilateral DBS electrodes in the PPNR. Evoked potentials were recorded from the local field potentials (LFP) from the PPNR with STN stimulation at different frequencies and bipolar contacts. Ipsilateral and contralateral short latency (<2ms) PPNR responses were evoked from left but not from right STN stimulation. In both patients, STN stimulation evoked contralateral PPNR responses at medium latencies between 41 and 45ms. Cortical evoked potentials to single pulse STN stimulation were observed at latencies between 18 and 27ms. These results demonstrate a functional connection between the STN and the PPNR. It likely involves direct projections between the STN and PPNR or polysynaptic pathways with thalamic or cortical relays.
Kadoya, Tatsuo; Uehara, Hirofumi; Yamamoto, Toshinori; Shiraishi, Munehiro; Kinoshita, Yuki; Joyashiki, Takeshi; Enokida, Kengo
Previously, we reported a case of brainstem cavernous hemangioma showing false positive responses to electromyographic tracheal tube (EMG tube). We concluded that the cause was spontaneous respiration accompanied by vocal cord movement. We report a case of left vertebral artery aneurysm showing evoked potentials on bilateral electrodes by the left vagus nerve stimulation to EMG tube. An 82-year-old woman underwent clipping of a left unruptured vertebral artery-posterior inferior cerebellar artery aneurysm. General anesthesia was induced with remifentanil, propofol and suxamethonium, and was maintained with oxygen, air, remifentanil and propofol. We monitored somatosensory evoked potentials, motor evoked potentials, and electromyogram of the vocal cord. When the manipulation reached brainstem and the instrument touched the left vagus nerve, evoked potentials appeared on bilateral electrodes. EMG tube is equipped with two electrodes on both sides. We concluded that the left vagus nerve stimulation generated evoked potentials of the left laryngeal muscles, and they were simultaneously detected as potential difference between two electrodes on both sides. EMG tube is used to identify the vagus nerve. However, it is necessary to bear in mind that each vagus nerve stimulation inevitably generates evoked potentials on bilateral electrodes.
Szlavik, Robert B
The characterization of peripheral nerve fiber distributions, in terms of diameter or velocity, is of clinical significance because information associated with these distributions can be utilized in the differential diagnosis of peripheral neuropathies. Electro-diagnostic techniques can be applied to the investigation of peripheral neuropathies and can yield valuable diagnostic information while being minimally invasive. Nerve conduction velocity studies are single parameter tests that yield no detailed information regarding the characteristics of the population of nerve fibers that contribute to the compound-evoked potential. Decomposition of the compound-evoked potential, such that the velocity or diameter distribution of the contributing nerve fibers may be determined, is necessary if information regarding the population of contributing nerve fibers is to be ascertained from the electro-diagnostic study. In this work, a perturbation-based decomposition of compound-evoked potentials is proposed that facilitates determination of the fiber diameter distribution associated with the compound-evoked potential. The decomposition is based on representing the single fiber-evoked potential, associated with each diameter class, as being perturbed by contributions, of varying degree, from all the other diameter class single fiber-evoked potentials. The resultant estimator of the contributing nerve fiber diameter distribution is valid for relatively large separations in diameter classes. It is also useful in situations where the separation between diameter classes is small and the concomitant single fiber-evoked potentials are not orthogonal.
Ibitoye, Morufu Olusola; Estigoni, Eduardo H.; Hamzaid, Nur Azah; Wahab, Ahmad Khairi Abdul; Davis, Glen M.
The evoked electromyographic signal (eEMG) potential is the standard index used to monitor both electrical changes within the motor unit during muscular activity and the electrical patterns during evoked contraction. However, technical and physiological limitations often preclude the acquisition and analysis of the signal especially during functional electrical stimulation (FES)-evoked contractions. Hence, an accurate quantification of the relationship between the eEMG potential and FES-evoked muscle response remains elusive and continues to attract the attention of researchers due to its potential application in the fields of biomechanics, muscle physiology, and rehabilitation science. We conducted a systematic review to examine the effectiveness of eEMG potentials to assess muscle force and fatigue, particularly as a biofeedback descriptor of FES-evoked contractions in individuals with spinal cord injury. At the outset, 2867 citations were identified and, finally, fifty-nine trials met the inclusion criteria. Four hypotheses were proposed and evaluated to inform this review. The results showed that eEMG is effective at quantifying muscle force and fatigue during isometric contraction, but may not be effective during dynamic contractions including cycling and stepping. Positive correlation of up to r = 0.90 (p < 0.05) between the decline in the peak-to-peak amplitude of the eEMG and the decline in the force output during fatiguing isometric contractions has been reported. In the available prediction models, the performance index of the eEMG signal to estimate the generated muscle force ranged from 3.8% to 34% for 18 s to 70 s ahead of the actual muscle force generation. The strength and inherent limitations of the eEMG signal to assess muscle force and fatigue were evident from our findings with implications in clinical management of spinal cord injury (SCI) population. PMID:25025551
Yamashiro, Koya; Sato, Daisuke; Onishi, Hideaki; Yoshida, Takuya; Horiuchi, Yoko; Nakazawa, Sho; Maruyama, Atsuo
Athletic training is known to induce neuroplastic alterations in specific somatosensory circuits, which are reflected by changes in short-latency somatosensory-evoked potentials (SEPs). The aim of this study is to clarify whether specific training in athletes affects the long-latency SEPs related to information processing of stimulation. The long-latency SEPs P100 and N140 were recorded at midline cortical electrode positions (Fz, Cz, and Pz) in response to stimulation of the index finger of the dominant hand in fifteen baseball players (baseball group) and in fifteen athletes in sports such as swimming, track and field events, and soccer (sports group) that do not require fine somatosensory discrimination or motor control of the hand. The long-latency SEPs were measured under a passive condition (no response required) and a reaction time (RT) condition in which subjects were instructed to rapidly push a button in response to stimulus presentation. The peak P100 and peak N140 latencies and RT were significantly shorter in the baseball group than the sports group. Moreover, there were significant positive correlations between RT and both the peak P100 and the peak N140 latencies. Specific athletic training regimens that involve the hand may induce neuroplastic alterations in the cortical hand representation areas playing a vital role in rapid sensory processing and initiation of motor responses.
Jones, Matthew D.; Taylor, Janet L.; Booth, John; Barry, Benjamin K.
Exercise-induced hypoalgesia is well described, but the underlying mechanisms are unclear. The aim of this study was to examine the effect of exercise on somatosensory evoked potentials, laser evoked potentials, pressure pain thresholds and heat pain thresholds. These were recorded before and after 3-min of isometric elbow flexion exercise at 40% of the participant's maximal voluntary force, or an equivalent period of rest. Exercise-induced hypoalgesia was confirmed in two experiments (Experiment 1–SEPs; Experiment 2–LEPs) by increased pressure pain thresholds at biceps brachii (24.3 and 20.6% increase in Experiment 1 and 2, respectively; both d > 0.84 and p < 0.001) and first dorsal interosseous (18.8 and 21.5% increase in Experiment 1 and 2, respectively; both d > 0.57 and p < 0.001). In contrast, heat pain thresholds were not significantly different after exercise (forearm: 10.8% increase, d = 0.35, p = 0.10; hand: 3.6% increase, d = 0.06, p = 0.74). Contrasting effects of exercise on the amplitude of laser evoked potentials (14.6% decrease, d = −0.42, p = 0.004) and somatosensory evoked potentials (10.9% increase, d = −0.02, p = 1) were also observed, while an equivalent period of rest showed similar habituation (laser evoked potential: 7.3% decrease, d = −0.25, p = 0.14; somatosensory evoked potential: 20.7% decrease, d = −0.32, p = 0.006). The differential response of pressure pain thresholds and heat pain thresholds to exercise is consistent with relative insensitivity of thermal nociception to the acute hypoalgesic effects of exercise. Conflicting effects of exercise on somatosensory evoked potentials and laser evoked potentials were observed. This may reflect non-nociceptive contributions to the somatosensory evoked potential, but could also indicate that peripheral nociceptors contribute to exercise-induced hypoalgesia. PMID:27965587
Jones, Matthew D; Taylor, Janet L; Booth, John; Barry, Benjamin K
Exercise-induced hypoalgesia is well described, but the underlying mechanisms are unclear. The aim of this study was to examine the effect of exercise on somatosensory evoked potentials, laser evoked potentials, pressure pain thresholds and heat pain thresholds. These were recorded before and after 3-min of isometric elbow flexion exercise at 40% of the participant's maximal voluntary force, or an equivalent period of rest. Exercise-induced hypoalgesia was confirmed in two experiments (Experiment 1-SEPs; Experiment 2-LEPs) by increased pressure pain thresholds at biceps brachii (24.3 and 20.6% increase in Experiment 1 and 2, respectively; both d > 0.84 and p < 0.001) and first dorsal interosseous (18.8 and 21.5% increase in Experiment 1 and 2, respectively; both d > 0.57 and p < 0.001). In contrast, heat pain thresholds were not significantly different after exercise (forearm: 10.8% increase, d = 0.35, p = 0.10; hand: 3.6% increase, d = 0.06, p = 0.74). Contrasting effects of exercise on the amplitude of laser evoked potentials (14.6% decrease, d = -0.42, p = 0.004) and somatosensory evoked potentials (10.9% increase, d = -0.02, p = 1) were also observed, while an equivalent period of rest showed similar habituation (laser evoked potential: 7.3% decrease, d = -0.25, p = 0.14; somatosensory evoked potential: 20.7% decrease, d = -0.32, p = 0.006). The differential response of pressure pain thresholds and heat pain thresholds to exercise is consistent with relative insensitivity of thermal nociception to the acute hypoalgesic effects of exercise. Conflicting effects of exercise on somatosensory evoked potentials and laser evoked potentials were observed. This may reflect non-nociceptive contributions to the somatosensory evoked potential, but could also indicate that peripheral nociceptors contribute to exercise-induced hypoalgesia.
Provencher, David; Hennebelle, Marie; Cunnane, Stephen C.; Bérubé-Lauzière, Yves; Whittingstall, Kevin
Although electroencephalography (EEG) is a valuable tool to investigate neural activity in patients and controls, exactly how local anatomy impacts the measured signal remains unclear. Better characterizing this relationship is important to improve the understanding of how inter-subject differences in the EEG signal are related to neural activity. We hypothesized that cortical structure might affect event-related desynchronization (ERD) in EEG. Since aging is a well-documented cause of cortical thinning, we investigated the effects of cortical thickness (CT) and cortical depth (CD – the skull-to-cortex distance) on ERD using anatomical MRI and motor-evoked EEG in 17 healthy young adults and 20 healthy older persons. Results showed a significant negative correlation between ERD and CT, but no consistent relationship between ERD and CD. A thinner cortex was associated with a larger ERD in the α/β band and correcting for CT removed most of the inter-group difference in ERD. This indicates that differences in neural activity might not be the primary cause for the observed aging-related differences in ERD, at least in the motor cortex. Further, it emphasizes the importance of considering conditions affecting the EEG signal, such as cortical anatomical changes due to aging, when interpreting differences between healthy controls and/or patients. PMID:27064767
Rogowski, M; Michalska, B I
The technique of Brainstem Electric Response Audiometry (BERA) is a non-invasive electrophysiologic method used in comatose patients for localization of areas of neuronal and synaptic dysfunction not evident in clinical evaluation. This test has a diagnostic and prognostic value in detection of abnormalities and evaluation of comatose head-injured patients at a reversible clinical stage. In contrast to most clinical signs, brainstem auditory evoked potentials are independent of levels of consciousness, analgesics, sedatives. This test is aetiologically non-specific and must be carefully integrated into the clinical situation. Generators of brainstem auditory evoked potentials are located in the auditory nerve (waves I and II) and brainstem (waves III-V). Patients in acute posttraumatic coma are assessed by means of Glasgow Coma Score (GCS), which is reliable in forecasting a favourable outcome. Patients with a score 8 points have an unfavourable outcome in 16%. Brainstem auditory evoked potentials are reliable predictors of unfavourable outcome. Subsequent brainstem auditory evoked potential testing provides relevant prognostic information, since improvement of graded brainstem auditory evoked potentials indicates a favourable outcome. Progressive deterioration of brainstem auditory evoked potentials indicates irreversible damage and is associated with unfavourable outcome, whereas singular abnormal evoked potentials may result from reversible neuronal dysfunction. The absence of waves III-V associated with the end EEG activity is the proof of brain death. Serial BERA monitoring has been used to evaluate progressive clinical syndromes, such as "uncal herniation" and evolving brain death. The use of serial BERA recordings appeared to improve the outcome predictions in comparison with single BERA tests. A combination of brainstem auditory evoked potentials, somatosensory and visual evoked potentials (multimodality evoked potentials-MEP) provides more information for
De Dios, Y. E.; Gadd, N. E.; Kofman, I. S.; Peters, B. T.; Reschke, M.; Bloomberg, J. J.; Wood, S. J.; Noohibezanjani, F.; Kinnaird, C.; Seidler, R. D.; Mulavara, A. P.
Introduction: Over the last two decades, several studies have been published on the impact of long-duration (i.e., 22 days or longer) spaceflight on the central nervous system (CNS). In consideration of the health and performance of crewmembers in flight and post-flight, we are conducting a controlled prospective longitudinal study to investigate the effects of spaceflight on the extent, longevity and neural bases of sensorimotor, cognitive, and neural changes. Multiple studies have demonstrated the effects of spaceflight on the vestibular system. One of the supporting tests conducted in this protocol is the Vestibular Evoked Myogenic Potential (VEMP) test that provides a unilateral measure of otolith (saccule and utricle) function. A different approach was taken for ocular VEMP (oVEMP) testing using a head striker system (Wackym et al. 2012). The oVEMP is generally considered to be a measure of utricle function. The the otolithic input to the inferior oblique muscle is predominately from the utricular macula. Thus, quantitatively, oVEMP tests utricular function. Another practical extension of these relationships is that the oVEMP reflects the superior vestibular nerve function. Methods: Ground testing was administered on 16 control subjects and for 8 subjects over four repeated sessions spanning 70 days. The oVEMP was elicitied via a hand held striker by a vibrotactile pulse presented at the rate of 1 Hz for 24 seconds on the side of the head as subjects lay supine on a gurney. Subjects were directed to gaze approximately 25 degrees above straight ahead in semi-darkness. For the oVEMP electromyograms will be recorded with active bipolar electrodes (Delsys Inc., Boston, MA) on the infra-orbital ridge 1 cm below the eyelid with a reference electrode on the below the knee cap. The EMG potentials were amplified; band-pass filtered using a BagnoliTM Desktop EMG System (Delsys Inc., Boston, MA, USA). This EMG signal is sampled at 10 kHz and the data stimulus onset to
Kallmann, B A; Fackelmann, S; Toyka, K V; Rieckmann, P; Reiners, K
Evoked potentials (EP) have a role in making the diagnosis of multiple sclerosis (MS) but their implication for predicting the future disease course in MS is under debate. EP data of 94 MS patients examined at first presentation, and after five and ten years were retrospectively analysed. Patients were divided into two groups in relation to the prior duration of disease at the time point of first examination: group 1 patients (n=44) were first examined within two years after disease onset, and group 2 patients (n=50) at later time points. As primary measures sum scores were calculated for abnormalities of single and combined EP (visual (VEP), somatosensory (SEP), magnetic motor evoked potentials (MEP)). In patients examined early after disease onset (group 1), a significant predictive value for abnormal EP was found with MEP and SEP sum scores at first presentation correlating significantly with Expanded Disability Status Scale (EDSS) values after five years, while the VEP sum score was not. The cumulative number of abnormal MEP, SEP and VEP results also indicated higher degrees of disability (EDSS > or = 3.5) after five years. Combined pathological SEP and MEP findings at first presentation best predicted clinical disability (EDSS > or = 3.5) after five years (odds ratio 11.0). EP data and EDSS at first presentation were not significantly linked suggesting that EP abnormalities at least in part represented clinically silent lesions not mirrored by EDSS. For patients in later disease phases (group 2), no significant associations between EP data at first presentation and EDSS at five and ten years were detected. Together with clinical findings and MR imaging, combined EP data may help to identify patients at high risk of long-term clinical deterioration and guide decisions as to immunomodulatory treatment.
Ruscheweyh, Ruth; Bäumler, Maximilian; Feller, Moritz; Krafft, Stefanie; Sommer, Jens; Straube, Andreas
We have recently shown that subjects can learn to use cognitive-emotional strategies to suppress their spinal nociceptive flexor reflex (RIII reflex) under visual RIII feedback and proposed that this reflects learned activation of descending pain inhibition. Here, we investigated whether learned RIII suppression also affects supraspinal nociception and whether previous relaxation training increases success. Subjects were trained over 3 sessions to reduce their RIII size by self-selected cognitive-emotional strategies. Two groups received true RIII feedback (with or without previous relaxation training) and a sham group received false feedback (15 subjects per group). RIII reflexes, late somatosensory evoked potentials (SEPs), and F-waves were recorded and pain intensity ratings collected. Both true feedback groups achieved significant (P < 0.01) but similar RIII suppression (to 79% ± 21% and 70% ± 17% of control). Somatosensory evoked potential amplitude (100-150 milliseconds after stimulation) was reduced in parallel with the RIII size (r = 0.57, P < 0.01). In the sham group, neither RIII size nor SEP amplitude was significantly reduced during feedback training. Pain intensity was significantly reduced in all 3 groups and also correlated with RIII reduction (r = 0.44, P < 0.01). F-wave parameters were not affected during RIII suppression. The present results show that learned RIII suppression also affects supraspinal nociception as quantified by SEPs, although effects on pain ratings were less clear. Lower motor neuron excitability as quantified by F-waves was not affected. Previous relaxation training did not significantly improve RIII feedback training success.
Herr, David W; Chanda, Sushmita M; Graff, Jaimie E; Barone, Stanley S; Beliles, Robert P; Morgan, Daniel L
Mercury is known to alter neuronal function and has been shown to cross the placental barrier. These experiments were undertaken to examine if gestational exposure to mercury vapor (Hg(0)) would result in alterations in sensory neuronal function in adult offspring. Dams were exposed to 0 or 4 mg/m(3) Hg(0) for 2 h/day from gestational days 6-15. This exposure paradigm has been shown to approximate a maximal tolerated dose of Hg(0) for the dams. Between postnatal days 140-168, male and female offspring (one of each gender/dam) were examined using a battery of sensory evoked potentials. Peripheral nerve action potentials, nerve conduction velocity, somatosensory evoked responses (cortical and cerebellar), brainstem auditory evoked responses, pattern evoked potentials, and flash evoked potentials were quantified. Gestational exposure to 4 mg/m(3) Hg(0) did not significantly alter any of the evoked responses, although there was a suggestion of a decrease in compound nerve action potential (CNAP) amplitudes in male animals for the 3 mA stimulus condition. However, this possible change in CNAP amplitudes was not replicated in a second experiment. All evoked potentials exhibited predictable changes as the stimulus was modified. This shows conclusively that the evoked responses were under stimulus control, and that the study had sufficient statistical power to detect changes of these magnitudes. These results indicate that gestational exposure to 4 mg/m(3) Hg(0) did not result in changes in responses evoked from peripheral nerves, or the somatosensory, auditory, or visual modalities.
Disertori, B; Ducati, A; Piazza, M; Pavani, M
A case of spasmodic torticollis with thoracic outlet syndrome observed for over 18 months is presented and discussed. Maximal head rotation (determining backward gaze) was associated with compression of the brachial plexus between the scaleni muscles and motor, sensory and trophic troubles in the hand. This new syndrome is called after the diviner Manto, quoted by Dante Alighieri in his 'Divina Commedia' (Inferno, XX, 52-56). The etiology was ascribed to subacute toxic effects of methylparathion. Brainstem Auditory Evoked Potentials (BAEPs) demonstrated severe brainstem involvement, maximal in the mesencephalic structures. Clinical and neurophysiological data improved on treatment with L-5-hydroxytryptophan. Finally, BAEPs returned to normal.
Results of the studies on evoked potentials (EP) in neonates with hypoxic-ischaemic encephalopathy and their technical feasibility support extensive application in neonatal intensive care units. The combined application of visual evoked potentials (VEP) and somestesic evoked potentials (SEP) is the method of choice for neurodevelopmental prognostication in full-term neonate; especially useful in cases with moderate encephalopathy; in preterm neonates EP are complementary to head ultrasound scans, particularly early on when the findings are in the process of evolution. Brainstem auditory evoked potentials (BAEP) are the technique of choice for early identification of sensorineural hearing loss necessitating intervention. Long term prognosis on vision and audition is based on VEP and BAEP. Studies devoted to definition of the role of EP in selection of babies and monitoring neuroprotective intervention are warranted.
Babakhani, Babak; Schott, Martin; Hosseinitabatabaei, Narges; Jantzen, Jan-Peter
Perioperative neuropathy is a known complication of malpositioning during anaesthesia. Somatosensory evoked potentials are used for detecting such a complication in selected surgeries. Most reports of intraoperative nerve injuries due to malpositioning are limited to injuries to the peripheral nervous system, and there have been no previously reported cases of somatosensory evoked potential monitoring disturbance attributable to position-related cerebral ischemia in the park-bench position. We present the case of a patient with glioblastoma in the park-bench position whose somatosensory evoked potential waveforms disappeared after head and neck repositioning. A prompt diagnosis of this complication and elimination of the underlying cause led to the return of somatosensory evoked potential waveforms, and there was no relevant neurologic deficit at the end of the surgery.
Jones, S J
Peripheral, spinal and cortical somatosensory evoked potentials were recorded in 26 patients with unilateral traction injuries of the brachial plexus ganglia. Of 10 cases explored surgically the recordings correctly anticipated the major site of the lesion in eight. PMID:422958
Pompe, Manca Tekavčič; Brecelj, Jelka; Kranjc, Branka Stirn
The purpose of this study was to evaluate color vision in young patients with demyelinating disease both clinically and electrophysiologically. Thirty young patients (8-28 years, mean age 19 years) with demyelinating disease with or without a history of optic neuritis (ON) were investigated. Color vision was evaluated clinically with the Ishihara test and the Farnsworth-Munsell 100 hue (FM 100 hue) test and electrophysiologically with chromatic visual evoked potentials (cVEPs). Color deficiency axis and error score (ES) obtained with the FM 100 hue test were analyzed. cVEPs to isoluminant red-green (R-G) and blue-yellow (B-Y) stimuli were recorded. The stimulus was a 7 deg circle composed of horizontal sinusoidal gratings with a spatial frequency of 2 cycles/deg and 90% chromatic contrast. Onset-offset mode of stimulation (ON:OFF=300∶700 ms) was used. Since the majority of the patients were adults (>18 years), the negative wave (N wave) of the cVEP respones is the prominent part and therefore was analyzed. Sixty eyes were studied-22 with at least one episode of ON (ON group) and 38 without any clinically evident episode of ON (nON group). The average ES in the ON group was 179.18±171.8, whereas in the nON group it was 87.60±65.34. The average N-wave latency in the ON group was 144±44 ms for the R-G stimulus and 146±56 ms for the B-Y stimulus, whereas in the nON group, it was 117±13 ms for the R-G stimulus and 121±22 ms for the B-Y one. The average N-wave amplitude in the ON group was 9.3±7.1 μV for the R-G stimulus and 5.1±3.9 μV for the B-Y one, whereas in the nON group, it was 10.8±8.3 μV for the R-G stimulus and 6.4±4.3 μV for the B-Y one. A significant difference between the ON and the nON group was found: in the ON group, ES was higher (p=0.01) and N-wave latency was longer (p=0.01) compared with those in the nON group. The study showed that color vision is expectedly more affected in the ON
He, Fengsheng; Liu, Xibao; Yang, Shi; Zhang, Shoulin ); Xu, Guanghua; Fang, Guangchai; Pan, Xiaowen )
The median nerve somatosensory evoked potentials (SEP), pattern reversal visual evoked potentials (VEP), and brain stem auditory evoked potentials (BAEP) were studied in 109 healthy adults and in 88 patients with acute carbon monoxide (CO) poisoning. The upper limits for normal values of peak and interpeak latencies of multimodalities of evoked potentials in the reference group were established by a stepwise multiple regression analysis. SEP changes selectively affecting N32 and N60 were found in 78.8% of patients. There was prolonged PI00 latency of VEP in 58.2% of the cases examined. The prevalence of BAEP abnormalities in comatose patients (36%) was significantly higher than that (8.6%) in conscious patients. BAEP abnormalities were most frequently seen in comatose patients who had diminished brain stem reflexes (77.8%). It has been found that a consistent abnormality involving N2O and subsequent peaks in SEP, a remarkable prolongation of PI00 latency in VEP, or a prolongation of Ill-V interpeak latency in BAEP as well as the reoccurrence of evoked potential abnormalities after initial recovery all indicate unfavorable outcomes in patients with acute CO poisoning. The multimodality evoked potentials have proved to be sensitive indicators in the evaluation of brain dysfunction and in the prediction of prognosis of acute CO poisoning and the development of delayed encephalopathy. 16 refs., 4 figs., 6 tabs.
Schlundt, Carolyn E; Dear, Randall L; Houser, Dorian S; Bowles, Ann E; Reidarson, Tom; Finneran, James J
The hearing sensitivities of two short-finned pilot whales (Globicephala macrorhynchus) were investigated by measuring auditory evoked potentials generated in response to clicks and sinusoidal amplitude modulated (SAM) tones. The first whale tested, an adult female, was a long-time resident at SeaWorld San Diego with a known health history. Click-evoked responses in this animal were similar to those measured in other echolocating odontocetes. Auditory thresholds were comparable to dolphins of similar age determined with similar evoked potential methods. The region of best sensitivity was near 40 kHz and the upper limit of functional hearing was between 80 and 100 kHz. The second whale tested, a juvenile male, was recently stranded and deemed non-releasable. Click-evoked potentials were not detected in this animal and testing with SAM tones suggested severe hearing loss above 10 kHz.
Kirk, Ian J; McNair, Nicolas A; Hamm, Jeffrey P; Clapp, Wesley C; Mathalon, Daniel H; Cavus, Idil; Teyler, Timothy J
Long-term potentiation (LTP) is the principal candidate synaptic mechanism underlying learning and memory, and has been studied extensively at the cellular and molecular level in laboratory animals. Inquiry into the functional significance of LTP has been hindered by the absence of a human model as, until recently, LTP has only been directly demonstrated in humans in isolated cortical tissue obtained from patients undergoing surgery, where it displays properties identical to those seen in non-human preparations. In this brief review, we describe the results of paradigms recently developed in our laboratory for inducing LTP-like changes in visual-, and auditory-evoked potentials. We describe how rapid, repetitive presentation of sensory stimuli leads to a persistent enhancement of components of sensory-evoked potential in normal humans. Experiments to date, investigating the locus, stimulus specificity, and NMDA receptor dependence of these LTP-like changes suggest that they have the essential characteristics of LTP seen in experimental animals. The ability to elicit LTP from non-surgical patients will provide a human model system allowing the detailed examination of synaptic plasticity in normal subjects and may have future clinical applications in the assessment of cognitive disorders. Copyright © 2010 John Wiley & Sons, Ltd. For further resources related to this article, please visit the WIREs website.
Lega, Bradley; Dionisio, Sasha; Flanigan, Patrick; Bingaman, William; Najm, Imad; Nair, Dileep; Gonzalez-Martinez, Jorge
Cortico-cortical evoked potentials offer the possibility of understanding connectivity within seizure networks to improve diagnosis and more accurately identify candidates for seizure surgery. We sought to determine if cortico-cortical evoked potentials and post-stimulation oscillatory changes differ for sites of EARLY versus LATE ictal spread. 37 patients undergoing stereoelectroencephalography were tested using a cortico-cortical evoked potential paradigm. All electrodes were classified according to the speed of ictal spread. EARLY spread sites were matched to a LATE spread site equidistant from the onset zone. Root-mean-square was used to quantify evoked responses and post-stimulation gamma band power and coherence were extracted and compared. Sites of EARLY spread exhibited significantly greater evoked responses after stimulation across all patients (t(36)=2.973, p=0.004). Stimulation elicited enhanced gamma band activity at EARLY spread sites (t(36)=2.61, p=0.03, FDR corrected); this gamma band oscillation was highly coherent with the onset zone. Cortico-cortical evoked potentials and post-stimulation changes in gamma band activity differ between sites of EARLY versus LATE ictal spread. The oscillatory changes can help visualize connectivity within the seizure network.
Brunton, Emma K.; Winther-Jensen, Bjorn; Wang, Chun; Yan, Edwin B.; Hagh Gooie, Saman; Lowery, Arthur J.; Rajan, Ramesh
Electrodes for cortical stimulation need to deliver current to neural tissue effectively and safely. We have developed electrodes with a novel annular geometry for use in cortical visual prostheses. Here, we explore a critical question on the ideal annulus height to ensure electrical stimulation will be safe and effective. We implanted single electrodes into the motor cortex of anesthetized rats and measured the current required to evoke a motor response to stimulation, and the charge injection capacity (CIC) of the electrodes. We compared platinum iridium (PtIr) electrodes with different annulus heights, with and without a coating of porous titanium nitride (TiN). Threshold charge densities to evoke a motor response ranged from 12 to 36 μC.cm-2.ph-1. Electrodes with larger geometric surface areas (GSAs) required higher currents to evoke responses, but lower charge densities. The addition of a porous TiN coating did not significantly influence the current required to evoke a motor response. The CIC of both electrode types was significantly reduced in vivo compared with in vitro measurements. The measured CIC was 72 and 18 μC.cm-2.ph-1 for electrodes with and without a TiN coating, respectively. These results support the use of PtIr annular electrodes with annulus heights greater than 100 μm (GSA of 38, 000 μm2). However, if the electrodes are coated with porous TiN the annulus height can be reduced to 40 μm (GSA of 16,000 μm2). PMID:26029097
Brunton, Emma K.; Winther-Jensen, Bjorn; Wang, Chun; Yan, Edwin B.; Hagh Gooie, Saman; Lowery, Arthur J.; Rajan, Ramesh
Electrodes for cortical stimulation need to deliver current to neural tissue effectively and safely. We have developed electrodes with a novel annular geometry for use in cortical visual prostheses. Here, we explore a critical question on the ideal annulus height to ensure electrical stimulation will be safe and effective. We implanted single electrodes into the motor cortex of anesthetized rats and measured the current required to evoke a motor response to stimulation, and the charge injection capacity (CIC) of the electrodes. We compared platinum iridium (PtIr) electrodes with different annulus heights, with and without a coating of porous titanium nitride (TiN). Threshold charge densities to evoke a motor response ranged from 12 to 36 μC.cm-2.ph-1. Electrodes with larger geometric surface areas (GSAs) required higher currents to evoke responses, but lower charge densities. The addition of a porous TiN coating did not significantly influence the current required to evoke a motor response. The CIC of both electrode types was significantly reduced in vivo compared with in vitro measurements. The measured CIC was 72 and 18 μC.cm-2.ph-1 for electrodes with and without a TiN coating, respectively. These results support the use of PtIr annular electrodes with annulus heights greater than 100 μm (GSA of 38, 000 μm2). However, if the electrodes are coated with porous TiN the annulus height can be reduced to 40 μm (GSA of 16,000 μm2). PMID:26283905
Rodriguez, Rosendo A
Focal neurologic and intellectual deficits or memory problems are relatively frequent after cardiac surgery. These complications have been associated with cerebral hypoperfusion, embolization, and inflammation that occur during or after surgery. Auditory evoked potentials, a neurophysiologic technique that evaluates the function of neural structures from the auditory nerve to the cortex, provide useful information about the functional status of the brain during major cardiovascular procedures. Skepticism regarding the presence of artifacts or difficulty in their interpretation has outweighed considerations of its potential utility and noninvasiveness. This paper reviews the evidence of their potential applications in several aspects of the management of cardiac surgery patients. The sensitivity of auditory evoked potentials to the effects of changes in brain temperature makes them useful for monitoring cerebral hypothermia and rewarming during cardiopulmonary bypass. The close relationship between evoked potential waveforms and specific anatomic structures facilitates the assessment of the functional integrity of the central nervous system in cardiac surgery patients. This feature may also be relevant in the management of critical patients under sedation and coma or in the evaluation of their prognosis during critical care. Their objectivity, reproducibility, and relative insensitivity to learning effects make auditory evoked potentials attractive for the cognitive assessment of cardiac surgery patients. From a clinical perspective, auditory evoked potentials represent an additional window for the study of underlying cerebral processes in healthy and diseased patients. From a research standpoint, this technology offers opportunities for a better understanding of the particular cerebral deficits associated with patients who are undergoing major cardiovascular procedures.
Deslandes, Andréa Camaz; Veiga, Heloisa; Cagy, Maurício; Piedade, Roberto; Pompeu, Fernando; Ribeiro, Pedro
The stimulant effects of caffeine on cognitive performance have been widely investigated. The visual evoked potential, specially the P300 component, has been used in studies that explain the stimulant mechanisms of caffeine through neurophysiological methods. In this context, the present study aimed to investigate electrophysiological changes (P300 latency) and modification of cognitive and motor performance produced by caffeine. Fifteen healthy volunteers, 9 women and 6 men (26 +/- 5 years, 67 +/- 12.5 kg) were submitted three times to the following procedure: electroencefalographic recording, Word Color Stroop Test, and visual discrimination task. Subjects took a gelatin caffeine capsule (400 mg) or a placebo (P1 and P2), in a randomized, crossover, double-blind design. A one-factor ANOVA and Tukey post hoc test were used to compare dependent variables on the C, P1 and P2 moments. The statistical analyses indicated a non-significant decrease in reaction time, Stroop execution time and latency at Cz on the caffeine moment when compared to the others. Moreover, a non-significant increase in Stroop raw score and latency at Pz could be observed. The only significant result was found at Fz. These findings suggest that the positive tendency of caffeine to improve cognitive performance is probably associated with changes in the frontal cortex, a widely recognized attention area.
Schmid, U D; Hess, C W; Ludin, H P
Twenty eight patients with unilateral cervical radiculopathy were studied by somatosensory evoked potentials (SEPs) from nerve stimulation at the wrist and from skin stimulation at the first, third or fifth finger depending on the root involved. In order to evaluate the reliability of various "radicular SEP patterns" as described in the literature, absolute latencies and side-to-side differences of the brachial plexus component from the supraclavicular fossa (N9), the medullary component (N13) from the cervical vertebra Cv7, and the primary cortical component (N20, P25) were assessed. Side-to-side differences of the amplitudes of N20/P25 and of the conduction times across the intervertebral fossa (interval N9-N13) were analysed. After nerve stimulation, 68% of the patients had false negative findings on the symptomatic, while 36% had positive findings on the asymptomatic side. After segmental stimulation, 72% of the patients had false negative findings on the symptomatic, while 22% had positive findings on the asymptomatic side. It is concluded that SEPs following nerve and segmental stimulation do not reliably confirm clear-cut already established diagnoses of unilateral radiculopathy with sensory and motor deficit. Therefore, they will not be helpful in the electrophysiological investigation of cervicobrachialgias of unknown origin. PMID:2831303
Pratt, Hillel; Starr, Arnold; Michalewski, Henry J; Dimitrijevic, Andrew; Bleich, Naomi; Mittelman, Nomi
The purpose of this study was to compare cortical brain responses evoked by amplitude modulated acoustic beats of 3 and 6 Hz in tones of 250 and 1000 Hz with those evoked by their binaural beats counterparts in unmodulated tones to indicate whether the cortical processes involved differ. Event-related potentials (ERPs) were recorded to 3- and 6-Hz acoustic and binaural beats in 2000 ms duration 250 and 1000 Hz tones presented with approximately 1 s intervals. Latency, amplitude and source current density estimates of ERP components to beats-evoked oscillations were determined and compared across beat types, beat frequencies and base (carrier) frequencies. All stimuli evoked tone-onset components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude in response to acoustic than to binaural beats, to 250 than to 1000 Hz base frequency and to 3 Hz than to 6 Hz beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left temporal lobe areas. Differences between estimated sources of potentials to acoustic and binaural beats were not significant. The perceptions of binaural beats involve cortical activity that is not different than acoustic beats in distribution and in the effects of beat- and base frequency, indicating similar cortical processing.
Fischer, Catherine; Luauté, Jacques
For comatose patients in intensive care units, it is important to anticipate their functional outcome as soon and as reliably as possible. Among clinical variables the Glasgow Coma Score (GCS) and the patient's pupil reactivity are the strongest predictive variables. Evoked potentials help to assess objectively brain function. Over the past 20 years, numerous studies have assessed their prognostic utility in terms of awakening from coma. Fewer studies, however, have focused upon the utility of evoked potentials in predicting progression to the vegetative state. In this area evoked potentials appear to have a highly predictive value. In anoxic coma the abolition of somatosensory evoked potentials (SEPs) is related to a poor outcome, defined as death or survival in a vegetative state, with a 100% specificity. Following traumatic brain injury, the predictive value for unfavourable outcome is 98.5% when there are no focal injuries likely to abolish SEP cortical components. In contrast, the presence of event-related evoked potentials, and particularly mismatched negativity (MMN), is a strong predictor of awakening and precludes comatose patients from moving to a permanent vegetative state (PVS).
Reznik, Daniel; Ossmy, Ori; Mukamel, Roy
Accumulating evidence demonstrates that responses in auditory cortex to auditory consequences of self-generated actions are modified relative to the responses evoked by identical sounds generated by an external source. Such modifications have been suggested to occur through a corollary discharge sent from the motor system, although the exact neuroanatomical origin is unknown. Furthermore, since tactile input has also been shown to modify responses in auditory cortex, it is not even clear whether the source of such modifications is motor output or somatosensory feedback. We recorded functional magnetic resonance imaging (fMRI) data from healthy human subjects (n = 11) while manipulating the rate at which they performed sound-producing actions with their right hand. In addition, we manipulated the amount of tactile feedback to examine the relative roles of motor and somatosensory cortices in modifying evoked activity in auditory cortex (superior temporal gyrus). We found an enhanced fMRI signal in left auditory cortex during perception of self-generated sounds relative to passive listening to identical sounds. Moreover, the signal difference between active and passive conditions in left auditory cortex covaried with the rate of sound-producing actions and was invariant to the amount of tactile feedback. Together with functional connectivity analysis, our results suggest motor output from supplementary motor area and left primary motor cortex as the source of signal modification in auditory cortex during perception of self-generated sounds. Motor signals from these regions could represent a predictive signal of the expected auditory consequences of the performed action.
Xiao, W H; Zheng, H; Zheng, F Y; Nuydens, R; Meert, T F; Bennett, G J
The dose-limiting side effect of the anti-neoplastic agent, paclitaxel, is a chronic distal symmetrical peripheral neuropathy that produces sensory dysfunction (hypoesthesia and neuropathic pain) but little or no distal motor dysfunction. Similar peripheral neuropathies are seen with chemotherapeutics in the vinca alkaloid, platinum-complex, and proteasome inhibitor classes. Studies in rats suggest that the cause is a mitotoxic effect on axonal mitochondria. If so, then the absence of motor dysfunction may be due to mitotoxicity that affects sensory axons but spares motor axons. To investigate this, paclitaxel exposure levels in the dorsal root, ventral root, dorsal root ganglion, peripheral nerve, and spinal cord were measured, and the ultrastructure and the respiratory function of mitochondria in dorsal roots and ventral roots were compared. Sensory and motor axons in the roots and nerve had comparably low exposure to paclitaxel and exposure in the spinal cord was negligible. However, sensory neurons in the dorsal root ganglion had a very high and remarkably persistent (up to 10 days or more after the last injection) exposure to paclitaxel. Paclitaxel evoked a significant increase in the incidence of swollen and vacuolated mitochondria in the myelinated and unmyelinated sensory axons of the dorsal root (as seen previously in the peripheral nerve) but not in the motor axons of the ventral root. Stimulated mitochondrial respiration in the dorsal root was significantly depressed in paclitaxel-treated animals examined 2-4 weeks after the last injection, whereas respiration in the ventral root was normal. We conclude that the absence of motor dysfunction in paclitaxel-evoked peripheral neuropathy may be due to the absence of a mitotoxic effect in motor neuron axons, whereas the sensory dysfunction may be due to a mitotoxic effect resulting from the primary afferent neuron's cell body being exposed to high and persistent levels of paclitaxel.
Regan, D; Murray, T J; Silver, R
Seven multiple sclerosis patients were cooled and four heated, but evoked potential delay changed in only five out 11 experiments. Control limits were set by cooling eight and heating four control subjects. One patient gave anomalous results in that although heating degraded perceptual delay and visual acuity, and depressed the sine wave grating MTF, double-flash resolution was improved. An explanation is proposed in terms of the pattern of axonal demyelination. The medium frequency flicker evoked potential test seems to be a less reliable means of monitoring the progress of demyelination in multiple sclerosis patients than is double-flash campimetry or perceptual delay campimetry, although in some situations the objectivity of the evoked potential test would be advantageous. PMID:599356
Squires, K. C.; Squires, N. K.; Hillyard, S. A.
Vertex evoked potentials were recorded from human subjects performing in an auditory detection task with rating scale responses. Three values of a priori probability of signal presentation were tested. The amplitudes of the N1 and P3 components of the vertex potential associated with correct detections of the signal were found to be systematically related to the strictness of the response criterion and independent of variations in a priori signal probability. No similar evoked potential components were found associated with signal absent judgements (misses and correct rejections) regardless of the confidence level of the judgement or signal probability. These results strongly support the contention that the form of the vertex evoked response is closely correlated with the subject's psychophysical decision regarding the presence or absence of a threshold level signal.
Brugger, Dominik; Butovas, Sergejus; Bogdan, Martin; Schwarz, Cornelius
Cortical neuroprostheses that employ repeated electrical stimulation of cortical areas with fixed stimulus parameters, are faced with the problem of large trial-by-trial variability of evoked potentials. This variability is caused by the ongoing cortical signal processing, but it is an unwanted phenomenon if one aims at imprinting neural activity as precisely as possible. Here, we use local field potentials measured by one microelectrode, located at a distance of 200 microns from the stimulation site, to drive the electrically evoked potential toward a desired target potential by real-time adaptation of the stimulus intensity. The functional relationship between ongoing cortical activity, evoked potential, and stimulus intensity was estimated by standard machine learning techniques (support vector regression with problem-specific kernel function) from a set of stimulation trials with randomly varied stimulus intensities. The smallest deviation from the target potential was achieved for low stimulus intensities. Further, the observed precision effect proved time sensitive, since it was abolished by introducing a delay between data acquisition and stimulation. These results indicate that local field potentials contain sufficient information about ongoing local signal processing to stabilize electrically evoked potentials. We anticipate that adaptive low intensity microstimulation will play an important role in future cortical prosthetic devices that aim at restoring lost sensory functions.
Hofmann, Martin J.; And Others
Averaged evoked potential (AEP) is an event-related brain response obtained by averaging the scalp electrical potentials elicited by repeated presentations of the same event. It has proven to be an accurate measure of the activity of the mature human brain when involved in a wide variety of psychological tasks. Distinct psychological processes…
Capon, Marie; Boven, Michel Van; van Pesch, Vincent; Hantson, Philippe
Post-operative visual loss (POVL) is a rare, albeit potentially serious complication of general anaesthesia. This report describes the case of a 54-year-old woman who developed transient POVL after general anaesthesia following a left posterior parietal meningioma surgery in the prone position and discusses the usefulness of visual evoked potentials monitoring in such situations. PMID:27601743
Colebatch, J G
The properties of rectified averages were investigated using the VEMP (vestibular-evoked myogenic potential) as an example of an evoked-type response. Recordings were made of surface EMG from the sternocleidomastoid (SCM) muscles of six volunteers, unstimulated, at different levels of tonic activation and then in response to clicks of different intensities. The stochastic properties of the surface EMG recorded were shown to be well modelled using a zero mean normal distribution with a standard deviation equivalent to the mean RMS (root mean squared) value (mean residual error variance 0.87%). Assuming a normal distribution, equations were derived for the expected value of both the rectified and RMS average with the addition of constant waveforms of different sizes. A simulation using recorded EMG and added sine waves of different amplitudes demonstrated that the equations predicted the rectified averages accurately. It also confirmed the importance of the relative amplitude of the added signal in determining whether it was detected using rectified averages. The same equations were then applied to actual data consisting of VEMPs of different relative amplitudes recorded from the volunteers. Whilst the signal-to-noise ratio (measured by corrected amplitude) was a major determinant of the nature of the rectified average, consistent deviations were detected between the predicted and actual rectified averages. Deviations from predicted values indicated that the VEMP did not behave simply like a constant signal added to tonic background EMG. A more complicated model, which included temporal jitter as well as inhibition of background EMG during the VEMP, was required to fit the physiological recordings. Rectified averages are sensitive to physiological properties, which are not apparent when using unrectified averages alone. Awareness of the properties of rectified averages should improve their interpretation.
Mihajloski, Todor; Bohorquez, Jorge; Özdamar, Özcan
Binaural beat (BB) illusions are experienced as continuous central pulsations when two sounds with slightly different frequencies are delivered to each ear. It has been shown that steady-state auditory evoked potentials (AEPs) to BBs can be captured and investigated. The authors recently developed a new method of evoking transient AEPs to binaural beats using frequency modulated stimuli. This methodology was able to create single BBs in predetermined intervals with varying carrier frequencies. This study examines the effects of the BB duration and the frequency modulating component of the stimulus on the binaural beats and their evoked potentials. Normal hearing subjects were tested with a set of four durations (25, 50, 100, and 200 ms) with two stimulation configurations, binaural dichotic (binaural beats) and diotic (frequency modulation). The results obtained from the study showed that out of the given durations, the 100 ms beat, was capable of evoking the largest amplitude responses. The frequency modulation effect showed a decrease in peak amplitudes with increasing beat duration until their complete disappearance at 200 ms. Even though, at 200 ms, the frequency modulation effects were not present, the binaural beats were still perceived and captured as evoked potentials.
Schaap, Manon W. H.; van Oostrom, Hugo; Doornenbal, Arie; Baars, Annemarie M.; Arndt, Saskia S.; Hellebrekers, Ludo J.
Somatosensory-evoked potentials (SEPs) are used in humans and animals to increase knowledge about nociception and pain. Since the SEP in humans increases when noxious stimuli are administered unpredictably, predictability potentially influences the SEP in animals as well. To assess the effect of predictability on the SEP in animals, classical fear conditioning was applied to compare SEPs between rats receiving SEP-evoking electrical stimuli either predictably or unpredictably. As in humans, the rat’s SEP increased when SEP-evoking stimuli were administered unpredictably. These data support the hypothesis that the predictability of noxious stimuli plays a distinctive role in the processing of these stimuli in animals. The influence of predictability should be considered when studying nociception and pain in animals. Additionally, this finding suggests that animals confronted with (un)predictable noxious stimuli can be used to investigate the mechanisms underlying the influence of predictability on central processing of noxious stimuli. PMID:23613862
Huidobro, Nayeli; Silva, Mayte; Flores, Amira; Trenado, Carlos; Quintanar, Luis; Arias-Carrión, Oscar; Kristeva, Rumyana
The present investigation documents the electrophysiological occurrence of multisensory stochastic resonance in the human visual pathway elicited by tactile noise. We define multisensory stochastic resonance of brain evoked potentials as the phenomenon in which an intermediate level of input noise of one sensory modality enhances the brain evoked response of another sensory modality. Here we examined this phenomenon in visual evoked potentials (VEPs) modulated by the addition of tactile noise. Specifically, we examined whether a particular level of mechanical Gaussian noise applied to the index finger can improve the amplitude of the VEP. We compared the amplitude of the positive P100 VEP component between zero noise (ZN), optimal noise (ON), and high mechanical noise (HN). The data disclosed an inverted U-like graph for all the subjects, thus demonstrating the occurrence of a multisensory stochastic resonance in the P100 VEP. PMID:26156387
Méndez-Balbuena, Ignacio; Huidobro, Nayeli; Silva, Mayte; Flores, Amira; Trenado, Carlos; Quintanar, Luis; Arias-Carrión, Oscar; Kristeva, Rumyana; Manjarrez, Elias
The present investigation documents the electrophysiological occurrence of multisensory stochastic resonance in the human visual pathway elicited by tactile noise. We define multisensory stochastic resonance of brain evoked potentials as the phenomenon in which an intermediate level of input noise of one sensory modality enhances the brain evoked response of another sensory modality. Here we examined this phenomenon in visual evoked potentials (VEPs) modulated by the addition of tactile noise. Specifically, we examined whether a particular level of mechanical Gaussian noise applied to the index finger can improve the amplitude of the VEP. We compared the amplitude of the positive P100 VEP component between zero noise (ZN), optimal noise (ON), and high mechanical noise (HN). The data disclosed an inverted U-like graph for all the subjects, thus demonstrating the occurrence of a multisensory stochastic resonance in the P100 VEP.
Pockberger, H; Rappelsberger, P
This paper describes the analyses of evoked potentials recorded in different neocortical areas (Area precentralis 1 and 2, occipitalis 1 and 2) and elicited by different stimulation techniques (antidromic stimulation of the pyramidal tract, electrical stimulation of thalamic nuclei, the optic nerve and finally random dot stimulation of the retina). Field potentials were recorded intracortically with a 16-fold electrode. The analyses of field potentials with the current-source-density method yielded an estimation of the current source and sink density distributions within the six neocortical layers. Hence spatio-temporal patterns of layer specific activation processes (sinks and sources) can be described for the various evoked potentials. The results can be summarized as follows: every evoked potential shows a spatio-temporal pattern of sources and sinks which is independent of the neocortical area and the mode of stimulation. However, the late components of the evoked potentials show great variations in their generation mechanisms, thus indicating regional differences in neocortical architectonics. These observations are discussed with regard to morphology, electrical activity and functional properties of the studied neocortical areas.
Starr, A; McPherson, D; Patterson, J; Don, M; Luxford, W; Shannon, R; Sininger, Y; Tonakawa, L; Waring, M
An 11-yr-old girl had an absence of sensory components of auditory evoked potentials (brainstem, middle and long-latency) to click and tone burst stimuli that she could clearly hear. Psychoacoustic tests revealed a marked impairment of those auditory perceptions dependent on temporal cues, that is, lateralization of binaural clicks, change of binaural masked threshold with changes in signal phase, binaural beats, detection of paired monaural clicks, monaural detection of a silent gap in a sound, and monaural threshold elevation for short duration tones. In contrast, auditory functions reflecting intensity or frequency discriminations (difference limens) were only minimally impaired. Pure tone audiometry showed a moderate (50 dB) bilateral hearing loss with a disproportionate severe loss of word intelligibility. Those auditory evoked potentials that were preserved included (1) cochlear microphonics reflecting hair cell activity; (2) cortical sustained potentials reflecting processing of slowly changing signals; and (3) long-latency cognitive components (P300, processing negativity) reflecting endogenous auditory cognitive processes. Both the evoked potential and perceptual deficits are attributed to changes in temporal encoding of acoustic signals perhaps occurring at the synapse between hair cell and eighth nerve dendrites. The results from this patient are discussed in relation to previously published cases with absent auditory evoked potentials and preserved hearing.
Romstock, J; Fahlbusch, R; Ganslandt, O; Nimsky, C; Strauss, C
Objective: Intraoperative localisation of the sensorimotor cortex using the phase reversal of somatosensory evoked potentials (SEPs) is an essential tool for surgery in and around the perirolandic gyri, but unsuccessful and perplexing results have been reported. This study examines the effect of tumour masses on the waveform characteristics and feasibility of SEP compared with functional neuronavigation and electrical motor cortex mapping. Methods: In 230 patients with tumours of the sensorimotor region the SEP phase reversal of N20-P20 was recorded from the exposed cortex using a subdural grid or strip electrode. In one subgroup of 80 patients functional neuronavigation was performed with motor and sensory magnetic source imaging and in one subgroup of 40 patients the motor cortex hand area was localised by electrical stimulation mapping. Results: The intraoperative SEP method was successful in 92% of all patients, it could be shown that the success rate rather depended on the location of the lesion than on preoperative neurological deficits. In 13% of the patients with postcentral tumours no N20-P20 phase reversal was recorded but characteristic polyphasic and high amplitude waves at 25 ms and later made the identification of the postcentral gyrus possible nevertheless. Electrical mapping of the motor cortex took up to 30 minutes until a clear result was obtained. It was successful in 37 patients, but failed in three patients with precentral and central lesions. Functional neuronavigation indicating the tumour margins and the motor and sensory evoked fields was possible in all patients. Conclusion: The SEP phase reversal of N20-P20 is a simple and reliable technique, but the success rate is much lower in large central and postcentral tumours. With the use of polyphasic late waveforms the sensorimotor cortex may be localised. By contrast with motor electrical mapping it is less time consuming. Functional neuronavigation is a desirable tool for both preoperative
Di Lazzaro, Vincenzo; Rothwell, John C
A number of methods have been developed recently that stimulate the human brain non-invasively through the intact scalp. The most common are transcranial magnetic stimulation (TMS), transcranial electric stimulation (TES) and transcranial direct current stimulation (TDCS). They are widely used to probe function and connectivity of brain areas as well as therapeutically in a variety of conditions such as depression or stroke. They are much less focal than conventional invasive methods which use small electrodes placed on or in the brain and are often thought to activate all classes of neurones in the stimulated area. However, this is not true. A large body of evidence from experiments on the motor cortex shows that non-invasive methods of brain stimulation can be surprisingly selective and that adjusting the intensity and direction of stimulation can activate different classes of inhibitory and excitatory inputs to the corticospinal output cells. Here we review data that have elucidated the action of TMS and TES, concentrating mainly on the most direct evidence available from spinal epidural recordings of the descending corticospinal volleys. The results show that it is potentially possible to test and condition specific neural circuits in motor cortex that could be affected differentially by disease, or be used in different forms of natural behaviour. However, there is substantial interindividual variability in the specificity of these protocols. Perhaps in the future it will be possible, with the advances currently being made to model the electrical fields induced in individual brains, to develop forms of stimulation that can reliably target more specific populations of neurones, and open up the internal circuitry of the motor cortex for study in behaving humans.
Wang, Bo-Chen; Liang, Yong; Liu, Xiao-Long; Zhao, Jing; Liu, You-Li; Li, Yan-Fei; Zhang, Wei; Li, Qi
The current study explored differences among cervical vestibular evoked myogenic potentials (cVEMP) that were evoked by CE-chirp and click and tone pip in healthy controls, and tried to explain the differences of cVEMP between the three of them. Thirty normal volunteers were used as subjects for CE-chirp and click and tone-pip (Blackman pip) stimuli. The latency of P1, N1, peak-to-peak P1-N1 amplitude, and cVEMP interaural difference were obtained and analyzed. The response rates of cVEMP were 93 % for click and 100 % for both Blackman pip and CE-chirp, respectively. The P1 and N1 latencies of cVEMP evoked by CE-chirp were the shortest, followed by click, with Blackman pip the longest (F = 6,686.852, P < 0.001). All indices of cVEMP evoked by the three stimuli showed no significant difference between the left and right ears or between genders. cVEMP responses were significantly different between the three stimuli. Compared with the currently used stimulus, CE-chirp can evoke cVEMP with shorter latencies and demonstrates increased speed and reliability.
Instrumentation Data Sheet .......................... 10 Figure 8. Human Physiology Screen One ....................................... 1I1 Figure 9. Human ... Physiology Screen Two...................................... 12 Figure 10. Human Physiology Screen Three ..................................... 12 Figure...Short-Latency Somatosensory Evoked Potentials in Impact Acceleration Research ***** HUMAN PHYSIOLOGY SCREEN***** Please Read First To move from one
Pohl, Daniela; Rostasy, Kevin; Treiber-Held, Stephanie; Brockmann, Knut; Gärtner, Jutta; Hanefeld, Folker
Pediatric patients with multiple sclerosis (MS) frequently do not meet MRI criteria for diagnosis because of lack of evidence of dissemination in space. We assessed the diagnostic utility of multimodal evoked potentials (EP). In 46% of 85 childhood patients with MS, spatial dissemination was detected by EP before the second clinical attack. EP may constitute an important tool for earlier diagnosis of pediatric MS.
Yanagihara, Masafumi; Sako, Akihito
This study investigates a negative component (N220) of visual evoked potential (VEP) which increases as certain cognitive processes are activated. Nine experimental conditions were designed by combining three stimulus and three task conditions. Letters were used as verbal stimuli, matrix patterns were used as nonverbal stimuli, and white light was…
Brown, Christopher; El-Deredy, Wael; Blanchette, Isabelle
In dot-probe tasks, threatening cues facilitate attention to targets and enhance the amplitude of the target P1 peak of the visual-evoked potential. While theories have suggested that evolutionarily relevant threats should obtain preferential neural processing, this has not been examined empirically. In this study we examined the effects of…
Bates, Tim; And Others
A study measuring average evoked potentials in 21 college students finds that intelligence test scores correlate significantly with the difference between string length in attended and nonattended conditions, a finding that suggests that previous inconsistencies in reporting string length-intelligence correlations may have resulted from confound…
Faldella, G; Govoni, M; Alessandroni, R; Marchiani, E; Salvioli, G P; Biagi, P L; Spano, C
The influence of dietary long chain polyunsaturated fatty acid (LCP) supply, and especially of docosahexaenoic acid (DHA), on evoked potential maturation, was studied in 58 healthy preterm infants using flash visual evoked potentials (VEPs), flash electroretinography (ERG), and brainstem acoustic evoked potentials (BAEPs) at 52 weeks of postconceptional age. At the same time, the fatty acid composition of red blood cell membranes was examined. The infants were fed on breast milk (n = 12), a preterm formula supplemented with LCP (PF-LCP) (n = 21), or a traditional preterm formula (PF) (n = 25). In the breast milk and PF-LCP groups the morphology and latencies of the waves that reflect the visual projecting system were similar; in the PF group the morphology was quite different and the wave latencies were significantly longer. This could mean that the maturation pattern of VEPs in preterm infants who did not receive LCP was slower. Moreover, a higher level of erythrocyte LCP, especially DHA, was found in breast milk and PF-LCP groups compared with the PF group. ERG and BAEP recordings were the same in all three groups. These results suggest that a well balanced LCP supplement in preterm formulas can positively influence the maturation of visual evoked potentials in preterm infants when breast milk is not available. PMID:8949693
Ellingson, Roger M; Oken, Barry
Report contains the design overview and key performance measurements demonstrating the feasibility of generating and recording ambulatory visual stimulus evoked potentials using the previously reported custom Complementary and Alternative Medicine physiologic data collection and monitoring system, CAMAS. The methods used to generate visual stimuli on a PDA device and the design of an optical coupling device to convert the display to an electrical waveform which is recorded by the CAMAS base unit are presented. The optical sensor signal, synchronized to the visual stimulus emulates the brain's synchronized EEG signal input to CAMAS normally reviewed for the evoked potential response. Most importantly, the PDA also sends a marker message over the wireless Bluetooth connection to the CAMAS base unit synchronized to the visual stimulus which is the critical averaging reference component to obtain VEP results. Results show the variance in the latency of the wireless marker messaging link is consistent enough to support the generation and recording of visual evoked potentials. The averaged sensor waveforms at multiple CPU speeds are presented and demonstrate suitability of the Bluetooth interface for portable ambulatory visual evoked potential implementation on our CAMAS platform.
Macpherson, Helen; Pipingas, Andrew; Silberstein, Richard
Old age is generally accompanied by a decline in memory performance. Specifically, neuroimaging and electrophysiological studies have revealed that there are age-related changes in the neural correlates of episodic and working memory. This study investigated age-associated changes in the steady state visually evoked potential (SSVEP) amplitude and…
Gomi, Hiroaki; Sakurada, Takeshi; Fukui, Takao
When stepping onto a stopped escalator, we often perceive an “odd sensation” that is never felt when stepping onto stairs. The sight of an escalator provides a strong contextual cue that, in expectation of the backward acceleration when stepping on, triggers an anticipatory forward postural adjustment driven by a habitual and implicit motor process. Here we contrast two theories about why this postural change leads to an odd sensation. The first theory links the odd sensation to a lack of sensorimotor prediction from all low-level implicit motor processes. The second theory links the odd sensation to the high-level conflict between the conscious awareness that the escalator is stopped and the implicit perception that evokes an endogenous motor program specific to a moving escalator. We show very similar postural changes can also arise from reflexive responses to visual stimuli, such as contracting/expanding optic flow fields, and that these reflexive responses produce similar odd sensations to the stopped escalator. We conclude that the high-level conflict is not necessary for such sensations. In contrast, the implicitly driven behavioral change itself essentially leads to the odd sensation in motor perception since the unintentional change may be less attributable to self-generated action because of a lack of motor predictions. PMID:24688460
Cabo, A; Handy, C; Bessis, D
The uniqueness of a surface density of sources localized inside a spatial region R and producing a given electric potential distribution in its boundary B0 is revisited. The situation in which R is filled with various subregions, each one having a definite constant value for the electric conductivity is considered. It is argued that the knowledge of the potential in all B0 fully determines the surface-located sources for a general class of surfaces supporting them and also a wide type of those sources. The class of surfaces can be defined as a union of an arbitrary but finite number of open or closed surfaces. The only restriction upon them is that no one of the closed surfaces contains inside it another (nesting) of the closed or open ones. The types of sources are surface charge densities and double layer (dipolar) densities for the open surfaces and more restrictively, only surface charge densities for the closed ones. A two-dimensional analytically solvable example illustrating the drastic appearance of uniqueness after arbitrarily small holes are opened in nested surfaces is discussed.
Babiloni, Claudio; Del Percio, Claudio; Brancucci, Alfredo; Capotosto, Paolo; Le Pera, Domenica; Marzano, Nicola; Valeriani, Massimiliano; Romani, Gian Luca; Arendt-Nielsen, Lars; Rossini, Paolo Maria
It is well known that scalp potentials evoked by nonpainful visual and auditory stimuli are enhanced in amplitude when preceded by pre-stimulus low-amplitude alpha rhythms. This study tested the hypothesis that the same holds for the amplitude of vertex N2-P2 potentials evoked by brief noxious laser stimuli, an issue of interest for clinical perspective. EEG data were recorded in 10 subjects from 30 electrodes during laser noxious stimulation. The artifact-free vertex N2-P2 complex was spatially enhanced by surface Laplacian transformation. Pre-stimulus alpha power was computed at three alpha sub-bands according to subject's individual alpha frequency peak (i.e. about 6-8Hz for alpha 1, 8-10Hz for alpha 2 and 10-12Hz for alpha 3 sub-band). Individual EEG single trials were divided in two sub-groups. The strong-alpha sub-group (high band power) included halfway of all EEG single trials, namely those having the highest pre-stimulus alpha power. Weak-alpha sub-group (low band power) included the remaining trials. Averaging procedure provided laser evoked potentials for both trial sub-groups. No significant effect was found for alpha 1 and alpha 2 sub-bands. Conversely, compared to strong-alpha 3 sub-group, weak-alpha 3 sub-group showed vertex N2-P2 potentials having significantly higher amplitude (p<0.05). These results extend to the later phases of pain processing systems the notion that generation mechanisms of pre-stimulus alpha rhythms and (laser) evoked potentials are intrinsically related and subjected to fluctuating "noise". That "noise" could explain the trial-by-trial variability of laser evoked potentials and perception.
Didoné, Dayane Domeneghini; Garcia, Michele Vargas; Oppitz, Sheila Jacques; da Silva, Thalisson Francisco Finamôr; dos Santos, Sinéia Neujahr; Bruno, Rúbia Soares; Filha, Valdete Alves Valentins dos Santos; Cóser, Pedro Luis
ABSTRACT Objective To establish reference intervals for cognitive potential P300 latency using tone burst stimuli. Methods This study involved 28 participants aged between 18 and 59 years. P300 recordings were performed using a two-channel device (Masbe, Contronic). Electrode placement was as follows: Fpz (ground electrode), Cz (active electrode), M1 and M2 (reference electrodes). Intensity corresponded to 80 dB HL and frequent and rare stimulus frequencies to 1,000Hz and 2,000Hz, respectively. Stimuli were delivered binaurally. Results Mean age of participants was 35 years. Average P300 latency was 305ms. Conclusion Maximum acceptable P300 latency values of 362.5ms (305 + 2SD 28.75) were determined for adults aged 18 to 59 years using the protocol described. PMID:27462895
Attention is an ambiguous concept, difficult to direct implementation in neurophysiological studies. The paper presents application of the Continuous Attention Test (CAT) items as stimuli in event related potential (ERP) studies on attention. Stimuli with high demand of attention result in enlarged N1 component in occipital derivations. Spatial analysis revealed increased positivity in frontal derivations. Three-dimensional image of cortical current density by means of Low Resolution Electromagnetic Tomography (LORETA) revealed sources of N1 component in occipital, parietal and postero-temporal derivations with the maximal current value at 17 Brodmann area. After target stimuli increase of current density in frontal derivations was observed, with the maximal value in the left 9 Brodmann area.
Lim, Louis J Z; Dennis, Danielle L; Govender, Sendhil; Colebatch, James G
We investigated the changes in cervical (cVEMP) and ocular (oVEMP) vestibular evoked myogenic potentials in response to differing stimulus durations. cVEMPs (n = 12 subjects) and oVEMPs (n = 13 subjects) were recorded using air-conducted (AC: 500 Hz) and bone-conducted (BC: 500 Hz) tone burst stimuli with durations varying from 2 to 10 ms. BC stimulation was applied both frontally and to the mastoid. AC cVEMPs showed an increase in amplitude with stimuli up to 6-ms duration associated with a prolonged latency, as previously reported. In contrast, AC oVEMP amplitude decreased with increasing stimulus duration. BC stimuli showed no significant increase in amplitude with increasing stimulus duration for either reflex using either location of stimulation. BC cVEMPS following forehead stimulation showed a significant decrease as duration increased, and BC oVEMPs to mastoid stimulation were largest at 2 ms and decreased thereafter. We conclude that an increase in amplitude with increasing stimulus duration, using 500 Hz stimuli, only occurs for AC cVEMPs. There is no definite benefit in using longer stimuli than 2 ms for BC or oVEMP studies. Shorter stimuli also minimise subject exposure to sound and vibration.
Kudoh, A; Matsuki, A
We investigated whether total intravenous anesthesia with ketamine, fentanyl and droperidol would affect middle latency auditory evoked potentials and explicit memory, and whether dreams during the anesthesia are related to plasma concentrations of fentanyl and the infusion technique. A total number of 40 patients were the subjects for this study. Twenty patients (group A) were maintained with intravenous ketamine 2 mg kg-1 hr-1 and fentanyl 5 micrograms kg-1 hr-1 for the first 60 min and 3 micrograms kg-1 hr-1 for the next 90 min, and droperidol 0.1 mg kg-1. The remaining 20 patients (group B) were maintained with intravenous ketamine 2 mg kg-1 hr-1, droperidol 0.1 mg kg-1 and fentanyl 50-100 micrograms in a bolus intermittently as needed by vital signs such as increases in heart rate and arterial blood pressure. Middle latency auditory evoked potentials, plasma fentanyl and ketamine levels were measured; explicit memory and dreams were also estimated. There were no patients who recollected explicit memories of intraoperative events in both groups. The middle latency auditory evoked potentials were not significantly changed during the anesthesia in both groups. We could find no significant differences in latencies and amplitudes of the middle latency auditory evoked potentials between the both groups. Plasma fentanyl levels of group B patients were significantly lower than those of group A patients and the incidence of the dreams was significantly higher in group B patients. We conclude that the anesthesia with ketamine, fentanyl and droperidol is not associated with the explicit memories, though the middle latency auditory evoked potentials were not significantly changed as compared with those in the waking state. In addition, dreams during the anesthesia may correlate with plasma fentanyl concentrations or the infusion technique.
Junker, A. M.; Kenner, K. M.; Kleinman, D. L.; Mcclurg, T. D.
To better describe the linear-dynamic properties of the human visual-cortical response system, transient and steady state Visual Evoked Response Potentials (VERP) were observed. The stimulus presentation device provided both the evoking stimulus (flickering or pulsing lights) and a video task display. The steady state stimulus was modulated by a complex, ten frequency, sum-of-sines, wave. The transient VERP was the time-locked average of the EEG to a series of narrow light pulses (pulse width of 10 msec). The Fourier transform of the averaged pulses had properties that approximate band limited white noise, i.e., a flat spectrum over the frequency region spanned by the 10 summed sines. The Fourier transform of both the steady state and the transient evoked potentials resulted in transfer that are equivalent and therefore comparable. To investigate the effects of task loading on evoked potentials, a grammatical reasoning task was provided. Results support the relevancy of continued application of a systems engineering approach for describing neurosensory functioning.
Stolarz, Maria; Dziubińska, Halina; Krupa, Maciej; Buda, Agnieszka; Trebacz, Kazimierz; Zawadzki, Tadeusz
The relationship between evoked electrical activity and stem movements in three-week old sunflowers was demonstrated. Electrical potential changes (recorded by Ag/AgCl extracellular electrodes) and time-lapse images (from a top view camera) were recorded and analyzed. A heat stimulus applied to the tip of one of the second pair of leaves evoked a variation potential, transmitted basipetally along one side of the stem. After stimulation, disturbances of circumnutations occurred. They included: changes in the period, disorders in the elliptical shape, and, in some cases, reversion of direction (of movement). We suggest that asymmetrically propagated variation potential induces asymmetric stem shrinking and bending, which strongly disturbs circumnutations. Our results confirm the involvement of electrical potential changes in the mechanism of stem nutations.
Courchesne, E.; Hillyard, S. A.; Galambos, R.
The effect of task relevance on P3 (waveform of human evoked potential) waves and the methodologies used to deal with them are outlined. Visual evoked potentials (VEPs) were recorded from normal adult subjects performing in a visual discrimination task. Subjects counted the number of presentations of the numeral 4 which was interposed rarely and randomly within a sequence of tachistoscopically flashed background stimuli. Intrusive, task-irrelevant (not counted) stimuli were also interspersed rarely and randomly in the sequence of 2s; these stimuli were of two types: simples, which were easily recognizable, and novels, which were completely unrecognizable. It was found that the simples and the counted 4s evoked posteriorly distributed P3 waves while the irrelevant novels evoked large, frontally distributed P3 waves. These large, frontal P3 waves to novels were also found to be preceded by large N2 waves. These findings indicate that the P3 wave is not a unitary phenomenon but should be considered in terms of a family of waves, differing in their brain generators and in their psychological correlates.
Pardillo-Díaz, R; Carrascal, L; Ayala, A; Nunez-Abades, P
Oxidative stress and the production of reactive oxygen radicals play a key role in neuronal cell damage. This paper describes an in vitro study that explores the neuronal responses to oxidative stress focusing on changes in neuronal excitability and functional membrane properties. This study was carried out in pyramidal cells of the motor cortex by applying whole-cell patch-clamp techniques on brain slices from young adult rats. Oxygen-derived free radical formation was induced by bath application of 10μM cumene hydroperoxide (CH) for 30min. CH produced marked changes in the electrophysiological properties of neurons (n=30). Resting membrane potential became progressively depolarized, as well as depolarization voltage, with no variations in voltage threshold. Membrane resistance showed a biphasic behavior, increasing after 5min of drug exposure and then it started to decrease, even under control values, after 15 and 30min. At the same time, changes in membrane resistance produced compensatory variations in the rheobase. The amplitude of the action potentials diminished and the duration increased progressively over time. Some of the neurons under study also lost their ability to discharge action potentials in a repetitive way. Most of the neurons, however, kept their repetitive discharge even though their maximum frequency and gain decreased. Furthermore, cancelation of the repetitive firing discharge took place at intensities that decreased with time of exposure to CH, which resulted in a narrower working range. We can conclude that oxidative stress compromises both neuronal excitability and the capability of generating action potentials, and so this type of neuronal functional failure could precede the neuronal death characteristics of many neurodegenerative diseases.
Randolph, D.I.; Lund, D.J.; Van Sice, C.W.; Esgandarian, G.E.
A system was designed to permit simultaneous viewing of the ocular fundus of the rhesus monkey (Macaca mulatta), the accurate placement of laser radiation on the retina, and the stimulation of the site to produce a grating visual evoked cortical potential (VECP). A fundus camera was modified to incorporate a grating whose image was projected onto the retina at specific locations. The evoked potential could thus be obtained for any rate of alternation before, during, and after the exposure of the fovea to any one of many laser sources. An example is shown of the use of this system to monitor the grating VECP before and after exposure of the animal's fundus to a 900 nm gallium arsenide laser source for 60 sec. In this case, changes were observed in the variability of the latency of components of the VECP when compared to the prelaser exposure potentials.
Randolph, D I; Lund, D J; Van Sice, C W; Esgandarian, G E
A system was designed to permit simultaneous viewing of the ocular fundus of the rhesus monkey (Macaca mulatta), the accurate placement of laser radiation on the retina, and the stimulation of the site to produce a grating visual evoked cortical potential (VECP). A fundus camera was modified to incorporate a grating whose image was projected onto the retina at specific locations. The evoked potential could thus be obtained for any rate of alternation before, during, and after the exposure of the fovea to any one of many laser sources. An example is shown of the use of this system to monitor the grating VECP before and after exposure of the animal's fundus to a 900 nm gallium arsenide laser source for 60 sec. In this case, changes were observed in the variability of the latency of components of the VECP when compared to the prelaser exposure potentials.
Cerutti, S; Baselli, G; Liberati, D; Pavesi, G
An original method is presented for the single sweep analysis of visual evoked potentials (VEP's). The introduced algorithm bases upon an AutoRegressive with eXogenous input (ARX) modeling. A Least Squares procedure estimates the coefficients of the model and allows to obtain a complete black-box description of the signal generation mechanism, besides providing a filtered version of the single sweep potential. The performance of the algorithm is verified on proper simulation tests and the experimental results put into evidence the noticeable improvement of signal-to-noise ratio with a consequent better recognition of the classical parameters of the peaks (latencies and amplitudes). The possibility of measuring these parameters on a single sweep basis enables to evaluate the dynamics of the Central Nervous System response during the entire course of the examination. A classification of the estimated evoked potentials in a small number of subsets, on the basis of their morphology, is also possible.
Junker, Andrew M.; Schnurer, John H.; Ingle, David F.; Downey, Craig W.
The use of the human steady-state evoked potential (SSEP) as a possible measure of mental-state estimation is explored. A method for evoking a visual response to a sum-of-ten sine waves is presented. This approach provides simultaneous multiple frequency measurements of the human EEG to the evoking stimulus in terms of describing functions (gain and phase) and remnant spectra. Ways in which these quantities vary with the addition of performance tasks (manual tracking, grammatical reasoning, and decision making) are presented. Models of the describing function measures can be formulated using systems engineering technology. Relationships between model parameters and performance scores during manual tracking are discussed. Problems of unresponsiveness and lack of repeatability of subject responses are addressed in terms of a need for loop closure of the SSEP. A technique to achieve loop closure using a lock-in amplifier approach is presented. Results of a study designed to test the effectiveness of using feedback to consciously connect humans to their evoked response are presented. Findings indicate that conscious control of EEG is possible. Implications of these results in terms of secondary tasks for mental-state estimation and brain actuated control are addressed.
Popov, Vladimir V; Nechaev, Dmitry I; Sysueva, Evgenia V; Rozhnov, Viatcheslav V; Supin, Alexander Ya
Temporary threshold shift (TTS) and the discrimination of spectrum patterns after fatiguing noise exposure (170 dB re 1 μPa, 10 min duration) was investigated in a beluga whale, Delphinapterus leucas, using the evoked potential technique. Thresholds were measured using rhythmic (1000/s) pip trains of varying levels and recording the rhythmic evoked responses. Discrimination of spectrum patterns was investigated using rippled-spectrum test stimuli of various levels and ripple densities, recording the rhythmic evoked responses to ripple phase reversals. Before noise exposure, the greatest responses to rippled-spectrum probes were evoked by stimuli with a low ripple density with a decrease in the response magnitude occurring with an increasing ripple density. After noise exposure, both a TTS and a reduction of the responses to rippled-spectrum probes appeared and recovered in parallel. The reduction of the responses to rippled-spectrum probes was maximal for high-magnitude responses at low ripple densities and was negligible for low-magnitude responses at high ripple densities. It is hypothesized that the impacts of fatiguing sounds are not limited by increased thresholds and decreased sensitivity results in reduced ability to discriminate fine spectral content with the greatest impact on the discrimination of spectrum content that may carry the most obvious information about stimulus properties.
Debnath, Ranjan; Franz, Elizabeth A
We investigated whether perception of hand movement via mirror reflection evokes activation in the motor cortex (M1) contralateral to the non-moving hand (the M1 ipsilateral to the moving hand). Continuous electroencephalography (EEG) was recorded from 14 participants while they performed unimanual extension-flexion hand movements in direct view and mirror view conditions. We measured the lateralized readiness potential (LRP) as a marker of M1 activation in both conditions. Both the direct and mirror view conditions produced LRPs, with the mirror view conditions revealing clear activation in M1 contralateral to the non-moving hand (ipsilateral to the moving hand) during both flexion and extension phases. This unambiguous demonstration of M1 activation in association with a non-moving hand (which is visually-perceived as moving), suggests that perception of movement can directly lead to M1 activation.
Pollock, V E; Schneider, L S; Chui, H C; Henderson, V; Zemansky, M; Sloane, R B
A meta-analytic review of flash and pattern reversal visual evoked potential research indicates that elderly demented patients have longer P100 latencies than age-matched control subjects. In the present empirical research, patients with research diagnoses of probable Alzheimer's disease were compared with sex- and age-matched control subjects using P100 latencies of visual evoked potentials (VEP) elicited by flash and pattern reversal. As compared to control subjects, Alzheimer's disease patients showed significantly longer P100 latencies of the VEP elicited by pattern reversal; the flash P100 only marginally distinguished them. These findings are discussed within the context of VEP recording practices, patient selection, sex and age matching of control subjects, and the visual system.
Pazzaglia, Costanza; Valeriani, Massimiliano
Neuropathic pain is a complex subject, not completely understood yet, and it is quite common in clinical practice, even outside of a neurological context. Neuropathic pain, often being a chronic process, alters and profoundly affects the quality of life. Therefore, the management of neuropathic pain involves a multidimensional approach, as physicians have to take care not only of the objective aspects of the problem, but also of the subjective experiences of pain. This explains why the attainment of a diagnosis becomes so important, as it allows clinicians to treat the patients with the best therapeutic approach. Several studies report the use of brain-evoked potentials for studying patients suffering from neuropathic pain. In particular, laser- and contact heat-evoked potentials have proved useful for the diagnosis of clinical conditions characterized by neuropathic pain. However, although these tools are reliable and safe instruments to assess function of the nociceptive system, their use is still largely confined to research purposes.
Norcia, Anthony M.; Appelbaum, L. Gregory; Ales, Justin M.; Cottereau, Benoit R.; Rossion, Bruno
Periodic visual stimulation and analysis of the resulting steady-state visual evoked potentials were first introduced over 80 years ago as a means to study visual sensation and perception. From the first single-channel recording of responses to modulated light to the present use of sophisticated digital displays composed of complex visual stimuli and high-density recording arrays, steady-state methods have been applied in a broad range of scientific and applied settings.The purpose of this article is to describe the fundamental stimulation paradigms for steady-state visual evoked potentials and to illustrate these principles through research findings across a range of applications in vision science. PMID:26024451
Zhang, Jian-Hua; Böhme, Johann F
In this paper we report an adaptive regularization network (ARN) approach to realizing fast blind separation of cerebral evoked potentials (EPs) from background electroencephalogram (EEG) activity with no need to make any explicit assumption on the statistical (or deterministic) signal model. The ARNs are proposed to construct nonlinear EEG and EP signal models. A novel adaptive regularization training (ART) algorithm is proposed to improve the generalization performance of the ARN. Two adaptive neural modeling methods based on the ARN are developed and their implementation and performance analysis are also presented. The computer experiments using simulated and measured visual evoked potential (VEP) data have shown that the proposed ARN modeling paradigm yields computationally efficient and more accurate VEP signal estimation owing to its intrinsic model-free and nonlinear processing characteristics.
Anlar, Omer; Kisli, Mesude; Tombul, Temel; Ozbek, Hanefi
Magnetic resonance imaging (MRI) is important in the diagnosis of and follow-up for the treatment of multiple sclerosis (MS); evoked potentials may be important if MRI is normal or cannot be performed. We assessed serial visual evoked potentials (VEPs) and cranial MRI in a group of clinically relapsing-remitting multiple sclerosis (N = 15) treated with interferon beta-lb (INFB-1b) and in normal subjects (N = 15). The investigations were done 1 week before INFB-lb therapy, 1 year later (N = 15), and 2 years later (N = 10). VEPs were abnormal in most of the patients; MRIs were abnormal in all patients. We used P100 latency as an electrophysiological index for the progress of illness. There were significant differences in VEPs between the beginning and ending of the interferon treatment. We concluded that VEPs would be a reliable index for following up the progress of MS under interferon therapy.
Lopez-Soto, Teresa; Postigo-Madueno, Amparo; Nunez-Abades, Pedro
In centrally related hearing loss, there is no apparent damage in the auditory system, but the patient is unable to hear sounds. In patients with cortical hearing loss (and in the absence of communication deficit, either total or partial, as in agnosia or aphasia), some attention-related or language-based disorders may lead to a wrong diagnosis of hearing impairment. The authors present two patients (8 and 11 years old) with no anatomical damage to the ear, the absence of neurological damage or trauma, but immature cortical auditory evoked potentials. Both patients presented a clinical history of multiple diagnoses over several years. Because the most visible symptom was moderate hearing loss, the patients were recurrently referred to audiological testing, with no improvement. This report describes the use of long-latency evoked potentials to determine cases of cortical hearing loss, where hearing impairment is a consequence of underdevelopment at the central nervous system. PMID:27006780
Boido, Davide; Kapetis, Dimos; Gnatkovsky, Vadym; Pastori, Chiara; Galbardi, Barbara; Sartori, Ivana; Tassi, Laura; Cardinale, Francesco; Francione, Stefano; de Curtis, Marco
Presurgical monitoring with intracerebral electrodes in patients with drug-resistant focal epilepsy represents a standard invasive procedure to localize the sites of seizures origin, defined as the epileptogenic zone (EZ). During presurgical evaluation, intracerebral single-pulse electrical stimulation (SPES) is performed to define the boundaries of eloquent areas and to evoke seizure-associated symptoms. Extensive intracranial exploration and stimulation generate a large dataset on brain connectivity that can be used to improve EZ detection and to understand the organization of the human epileptic brain. We developed a protocol to analyse field responses evoked by intracranial stimulation. Intracerebral recordings were performed with 105-162 recording sites positioned in fronto-temporal regions in 12 patients with pharmacoresistant focal epilepsy. Recording sites were used for bipolar SPES at 1 Hz. Reproducible early and late phases (<60 ms and 60-500 ms from stimulus artefact, respectively) were identified on averaged evoked responses. Phase 1 and 2 responses recorded at all and each recording sites were plotted on a 3D brain reconstructions. Based on connectivity properties, electrode contacts were primarily identified as receivers, mainly activators or bidirectional. We used connectivity patterns to construct networks and applied cluster partitioning to study the proprieties between potentials evoked/stimulated in different regions. We demonstrate that bidirectional connectivity during phase 1 is a prevalent feature that characterize contacts included in the EZ. This study shows that the application of an analytical protocol on intracerebral stimulus-evoked recordings provides useful information that may contribute to EZ detection and to the management of surgical-remediable epilepsies.
Garcia-Larrea, L; Frot, M; Valeriani, M
In this work we review data on cortical generators of laser-evoked potentials (LEPs) in humans, as inferred from dipolar modelling of scalp EEG/MEG results, as well as from intracranial data recorded with subdural grids or intracortical electrodes. The cortical regions most consistently tagged as sources of scalp LERs are the suprasylvian region (parietal operculum, SII) and the anterior cingulate cortex (ACC). Variability in opercular sources across studies appear mainly in the anterior-posterior direction, where sources tend to follow the axis of the Sylvian fissure. As compared with parasylvian activation described in functional pain imaging studies, LEP opercular sources tended to cluster at more superior sites and not to involve the insula. The existence of suprasylvian opercular LEPs has been confirmed by both epicortical (subdural) and intracortical recordings. In dipole-modelling studies, these sources appear to become active less than 150 ms post-stimulus, and remain in action for longer than opercular responses recorded intracortically, thus suggesting that modelled opercular dipoles reflect a "lumped" activation of several sources in the suprasylvian region, including both the operculum and the insula. Participation of SI sources to explain LEP scalp distribution remains controversial, but evidence is emerging that both SI and opercular sources may be concomitantly activated by laser pulses, with very similar time courses. Should these data be confirmed, it would suggest that a parallel processing in SI and SII has remained functional in humans for noxious inputs, whereas hierarchical processing from SI toward SII has emerged for other somatosensory sub-modalities. The ACC has been described as a source of LEPs by virtually all EEG studies so far, with activation times roughly corresponding to scalp P2. Activation is generally confined to area 24 in the caudal ACC, and has been confirmed by subdural and intracortical recordings. The inability of most MEG
Rothstein, Ted Laurence
The loss of the N20 component on testing median somatosensory evoked potentials (SSEP) has been established as the most reliable indicator of unfavorable prognosis in post-cardiopulmonary arrest patients. With the intervention of therapeutic hypothermia in the management of patients who remain comatose following cardiopulmonary arrest that association is now in dispute. Abandoning SSEP as a key prognostic indicator of neurologic outcome would be a serious loss and cannot be justified.
Lessard, Anne-Marie I; Gilchrist, James; Schaefer, Leah; Dupuy, Damian E
Palliation of recurrent Ewing sarcoma can be difficult to treat due to tumor resistance to chemotherapy and previously received maximum dose radiotherapy. We report the successful use of cryoablation for pain palliation in a patient with recurrent pelvic Ewing sarcoma. Tumor location necessitated use of somatosensory-evoked potentials to prevent nerve damage to the S1 nerve root. Clinical and imaging aspects of the case are discussed.
Schwent, V. L.; Hillyard, S. A.
Ten subjects were presented with random, rapid sequences of four auditory tones which were separated in pitch and apparent spatial position. The N1 component of the auditory vertex evoked potential (EP) measured relative to a baseline was observed to increase with attention. It was concluded that the N1 enhancement reflects a finely tuned selective attention to one stimulus channel among several concurrent, competing channels. This EP enhancement probably increases with increased information load on the subject.
12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited 13. SUPPLEMENTARY NOTES The original document contains...the Beach testing the hearing of a stranded dolphin RESULTS This ruggedized device for measuring the hearing of stranded cetaceans allows us to...and Echolocation Mechanisms of Marine Mammals: Measured Auditory Evoked Potential and Behavioral Experiments: Award Number: N00014-08-1-1160. Self
Mueller, S.H.; Hotz, M. )
Recently significant changes of human brainstem auditory evoked potentials (BAEP) after exposure to static magnetic fields were reported. We recorded BAEPs of 11 subjects before and after a routine MRI examination at 1.5 T. In addition the BAEP of a healthy volunteer was measured in five different static magnetic fields (0-2.0 T). Our results indicate that routine MRI investigations do not significantly alter the interpeak latencies of the BAEPs.
Wilson, G F; Fullenkamp, P; Davis, I
Brain evoked potentials were successfully recorded from F-4 pilots during air-to-ground training missions. They were recorded during two flight segments. During one the pilot was flying, and during the other, the weapon systems officer was flying the aircraft. The P2 component of the brain-evoked potential evidenced reduced amplitude during the pilot-flying segment, while the N1 component was reduced during both flight tasks compared to ground-based tasks. These data indicate that the P2 amplitude is sensitive to the level of pilot workload. These results were further substantiated using simultaneously recorded physiological data and subjective workload measures. For example, cardiac inter-beat intervals decreased during flight segments relative to those recorded when performing a tracking task, and further reduced for the pilot-flying vs. the weapon systems officer-flying segment. Eye blink measures were sensitive to the visual demands of the various tasks. These data show that evoked potentials can be recorded during flight, and that, together with cardiac and eye blink data, they provide a composite picture of operator state.
Rothstein, Ted L
The early recognition of comatose patients with a hopeless prognosis--regardless of how aggressively they are managed--is of utmost importance. Median somatosensory evoked potentials (SSEP) supplement and enhance neurological examination findings in anoxic-ischemic coma and are useful as an early guide in predicting outcome. The key finding is that bilateral absence of cortical evoked potentials reliably predicts unfavorable outcome in comatose patients after cardiac arrest. The author studied 50 comatose patients with preserved brainstem function after cardiac arrest. All 23 patients with bilateral absence of cortical evoked potentials died without awakening. Neuropathological study in seven patients disclosed widespread ischemic changes or frank cortical laminar necrosis. The remaining 27 patients with normal or delayed central conduction times had an uncertain prognosis because some died without awakening or entered a persistent vegetative state. The majority of patients with normal central conduction times had a good outcome, whereas a delay in central conduction times increased the likelihood of neurological deficit or death. Greater use of SSEP in anoxic-ischemic coma would identify those patients unlikely to recover and would avoid costly medical care that is to no avail.
Buonfiglio, Marzia; Toscano, M; Puledda, F; Avanzini, G; Di Clemente, L; Di Sabato, F; Di Piero, V
Habituation is considered one of the most basic mechanisms of learning. Habituation deficit to several sensory stimulations has been defined as a trait of migraine brain and also observed in other disorders. On the other hand, analytic information processing style is characterized by the habit of continually evaluating stimuli and it has been associated with migraine. We investigated a possible correlation between lack of habituation of evoked visual potentials and analytic cognitive style in healthy subjects. According to Sternberg-Wagner self-assessment inventory, 15 healthy volunteers (HV) with high analytic score and 15 HV with high global score were recruited. Both groups underwent visual evoked potentials recordings after psychological evaluation. We observed significant lack of habituation in analytical individuals compared to global group. In conclusion, a reduced habituation of visual evoked potentials has been observed in analytic subjects. Our results suggest that further research should be undertaken regarding the relationship between analytic cognitive style and lack of habituation in both physiological and pathophysiological conditions.
Cuypers, M H; Thijssen, J M
Ensemble averaging is generally used for the estimation of Evoked Potentials. This paper deals with the assessment of correction procedures for the time variability of the ensemble components, this time variability reduces the improvement of the signal-to-noise ratio (SNR) by averaging. Evoked potentials were estimated by ensemble averaging, synchronized to a periodic stimulus. It is assumed that VEP-instability is partly caused by time-variability of the evoked potentials. Two time-variate models were used, from which procedures were derived to correct the single VEP-responses prior to ensemble averaging. The models are: (1) variation in response delay (jitter), (2) variable compression/expansion of the time scale of the response (wow). The Spectral Phase Difference method was applied to estimate both the delay time jitter and the wow factor of single responses with respect to a template (conventional ensemble average). The effects of the devised correction on the average VEP waveform and on the SNR of the ensemble were investigated by using data from realistic simulations and from experiments (n = 23) with a number of healthy human volunteers (n = 17). Jitter- and wow-corrections were effective on simulations with time variability due to delay time jitter and time scale distortion (wow), respectively. Both wow- and jitter correction of the single responses improved the SNR of the VEP measurements significantly and to the same amount. A combined wow-jitter approach resulted in significantly better results than the exclusive application of jitter- or wow correction.
Di Stefano, G.; Stubbs, M. T.; Djeugam, B.; Liang, M.
Abstract Feature selection has been extensively studied in the context of goal-directed behavior, where it is heavily driven by top-down factors. A more primitive version of this function is the detection of bottom-up changes in stimulus features in the environment. Indeed, the nervous system is tuned to detect fast-rising, intense stimuli that are likely to reflect threats, such as nociceptive somatosensory stimuli. These stimuli elicit large brain potentials maximal at the scalp vertex. When elicited by nociceptive laser stimuli, these responses are labeled laser-evoked potentials (LEPs). Although it has been shown that changes in stimulus modality and increases in stimulus intensity evoke large LEPs, it has yet to be determined whether stimulus displacements affect the amplitude of the main LEP waves (N1, N2, and P2). Here, in three experiments, we identified a set of rules that the human nervous system obeys to identify changes in the spatial location of a nociceptive stimulus. We showed that the N2 wave is sensitive to: (1) large displacements between consecutive stimuli in egocentric, but not somatotopic coordinates; and (2) displacements that entail a behaviorally relevant change in the stimulus location. These findings indicate that nociceptive-evoked vertex potentials are sensitive to behaviorally relevant changes in the location of a nociceptive stimulus with respect to the body, and that the hand is a particularly behaviorally important site. PMID:27419217
Voss, Logan J; Sleigh, James W
Despite their ubiquitous use for rendering patients unconscious for surgery, our understanding of how general anesthetics cause hypnosis remains rudimentary at best. Recent years have seen increased interest in "top-down" cortico-centric theories of anesthetic action. The aim of this study was to explore this by investigating direct cortical effects of anesthetics on cerebrocortical evoked potentials in isolated mouse brain slices. Evoked potentials were elicited in cortical layer IV by electrical stimulation of the underlying white matter. The effects of three anesthetics (ketamine, etomidate, and isoflurane) on the amplitude, latency, and slope of short-latency evoked potentials were quantified. The N2/P3/N4 potentials–which represent the early cortical response–were enhanced by etomidate (increased P3-N4 slope, P <0.01), maintained by ketamine, and reduced by isoflurane (lower N2/P3 amplitude, P <0.01). These effects closely resemble those seen in vivo for the same drugs and point to a cortical mechanism independent of effects on subcortical structures such as the thalamus.
Todd, Neil P M; McLean, Aisha; Paillard, Aurore; Kluk, Karolina; Colebatch, James G
We report the results of a study to record vestibular evoked potentials (VsEPs) of cortical origin produced by impulsive acceleration (IA). In a sample of 12 healthy participants, evoked potentials recorded by 70 channel electroencephalography were obtained by IA stimulation at the nasion and compared with evoked potentials from the same stimulus applied to the forefingers. The nasion stimulation gave rise to a series of positive and negative deflections in the latency range of 26-72 ms, which were dependent on the polarity of the applied IA. In contrast, evoked potentials from the fingers were characterised by a single N50/P50 deflection at about 50 ms and were polarity invariant. Source analysis confirmed that the finger evoked potentials were somatosensory in origin, i.e. were somatosensory evoked potentials, and suggested that the nasion evoked potentials plausibly included vestibular midline and frontal sources, as well as contributions from the eyes, and thus were likely VsEPs. These results show considerable promise as a new method for assessment of the central vestibular system by means of VsEPs produced by IA applied to the head.
Chen, Jason A.; Coutin-Churchman, Pedro E.; Nuwer, Marc R.; Lazareff, Jorge A.
Background: Management of Chiari I is controversial, in part because there is no widely used quantitative measurement of decompression. It has been demonstrated that brainstem auditory evoked responses (BAER) and somatosensory evoked potentials (SSEP) have decreased conduction latencies after wide craniectomy. We analyzed these parameters in a suboccipital craniectomy/craniotomy procedure. Methods: Thirteen consecutive patients underwent suboccipital decompression for treatment of symptomatic Chiari I. Craniectomy was restricted to the inferior aspect of the nuchal line, and in most cases the bone flap was replaced. Neuronal conduction was monitored continuously with median nerve somatosensory evoked potentials (M-SEP), posterior tibial nerve somatosensory evoked potentials (T-SEP), BAER, or a combination. The M-SEP N20, T-SEP P37, and BAER V latencies were recorded at four milestones – preoperatively, following craniotomy, following durotomy, and following closure. Results: Five males and eight females, with average age of 9 years, were studied. Clinical improvement was noted in all 13 patients. M-SEP N20 latency decreased from a mean of 18.55 at baseline to 17.75 ms after craniotomy (P = 0.01); to 17.06 ms after durotomy (P = 0.01); and to 16.68 ms after closing (P = 0.02). T-SEP P37 latency did not change significantly. BAER V latency decreased from a mean of 6.25 ms at baseline to 6.14 ms after craniotomy (P = 0.04); to 5.98 ms after durotomy (P = 0.01); and to 5.95 ms after closing (P = 0.45). Conclusion: Significant improvements in conduction followed both craniectomy and durotomy. Bone replacement did not affect these results. PMID:23372981
Vialatte, François-Benoît; Maurice, Monique; Dauwels, Justin; Cichocki, Andrzej
After 40 years of investigation, steady-state visually evoked potentials (SSVEPs) have been shown to be useful for many paradigms in cognitive (visual attention, binocular rivalry, working memory, and brain rhythms) and clinical neuroscience (aging, neurodegenerative disorders, schizophrenia, ophthalmic pathologies, migraine, autism, depression, anxiety, stress, and epilepsy). Recently, in engineering, SSVEPs found a novel application for SSVEP-driven brain-computer interface (BCI) systems. Although some SSVEP properties are well documented, many questions are still hotly debated. We provide an overview of recent SSVEP studies in neuroscience (using implanted and scalp EEG, fMRI, or PET), with the perspective of modern theories about the visual pathway. We investigate the steady-state evoked activity, its properties, and the mechanisms behind SSVEP generation. Next, we describe the SSVEP-BCI paradigm and review recently developed SSVEP-based BCI systems. Lastly, we outline future research directions related to basic and applied aspects of SSVEPs.
Kemp, Jennifer; Després, Olivier; Pebayle, Thierry; Dufour, André
Aging is associated with changes in thermosensitivity and decreases in the functionality of the autonomic thermoregulation. The underlying mechanisms are, however, not fully understood. Elderly subjects may undergo functional changes in the integration process of the thermal sensory system, especially in their thermal adaptation capacities. To verify this hypothesis, we compared thermal evoked responses in younger and older subjects exposed to thermoneutral (27 °C) and warm (30 °C) environments. In the warm environment, the amplitudes of thermal evoked potentials (EPs) were significantly lower in older than in younger subjects, whereas in the thermoneutral environment, the EP amplitudes were similar in both groups. These findings suggest that thermal adaptation capacities are reduced in elderly individuals, due to a dysfunction of C-fibers with aging, particularly expressed by lowered adaptation capacities to temperature variations.
Hooper, D. C.; Martin, S. M.; Horowitz, J. M.
1. Neural activity was recorded in hippocampal slices from euthermic chipmunks, hamsters and rats. 2. While recording the evoked potentials, the temperature of the Ringer's solution bathing the slice was varied by controlling the temperature of an outer chamber jacketing the recording chamber. 3. The temperature just below that at which a population spike could be evoked, Tt, was 10.4 +/- 0.3 degrees C (mean +/- SEM) for chipmunk slices, 14.1 +/- 0.4 degrees C for rat slices and 14.8 +/- 0.4 degrees C for hamster slices. Tt was significantly lower in the chipmunk slices (P<0.01) than in the rat and hamster slices. 4. Data were interpreted as consistent with the hypothesis that chipmunk hippocampal neurons are intrinsically cold resistant.
Ryu, Shingo; Higashi, Hiroshi; Tanaka, Toshihisa; Nakauchi, Shigeki; Minami, Tetsuto
Brain computer interface (BCI) is a system for communication between people and computers via brain activity. Steady-state visual evoked potentials (SSVEPs), a brain response observed in EEG, are evoked by flickering stimuli. SSVEP is one of the promising paradigms for BCI. Canonical correlation analysis (CCA) is widely used for EEG signal processing in SSVEP-based BCIs. However, the classification accuracy of CCA with short signal length is low. In order to solve the problem, we propose a regularization which works in such a way that the CCA spatial filter becomes spatially smooth to give robustness in short signal length condition. The spatial filter is designed in a parameter space spanned by a spatially smooth basis which are given by a graph Fourier transform of three dimensional electrode coordinates. We compared the classification accuracy of the proposed regularized CCA with the standard CCA. The result shows that the proposed CCA outperforms the standard CCA in short signal length condition.
Sindou, M; Fobe, J L; Berthier, E; Vial, C
In Sweet's description of RF-thermocoagulation for trigeminal neuralgia, the trigeminal nerve was stimulated at 50 c/s to evoke paraesthesias, in order to check the electrode location before the thermolesion is made. In 1979, we changed the frequency to 5 c/s, so as to produce in addition twitches in the masticatory muscles (in stead of the less detectable tetanization produced by 50 c/s stimulation). Since then, we started to observe, also, twitches in the muscles innervated by the facial nerve. These twitches were not always in the Orbicularis oculi (which corresponds to the classical blink reflex), but also in the lower facial muscles. Such clinically observable evoked motor responses (EMR)-which had not been reported before--were noticed in 44% of the 459 procedures performed from 1979 to 1988. When EMR were present, the threshold to evoke paraesthesias before thermolesion, and the duration of the thermolesion for obtaining a marked hypoaesthesia covering the entire painful territory, were significantly lower, respectively p < 0.01 and p < 0.001, than when EMR were absent. This indicates that the electrode was closer to the nerve when EMR were present. As a probable consequence, recurrence of pain was significantly lower in the EMR (+) group: 1.4%, than in the EMR (-) group: 5.8% (p < 0.05). The twitches corresponded to the territory of the evoked paraesthesias in 95%, and to the hypoaesthetic area created by the thermolesion in 96%. So, getting EMR in the territory of the pain can be a helpful indicator for an accurate location of the electrode in the trigeminal root, according to its somatotopic organization. These EMR are hypothesized to be due to a trigemino-facial reflex. A preliminary intra-operative EMG study clearly shows that for EMR in the upper part of the face we are dealing with blink-like reflexes, whilst for EMR in the lower face, mechanisms still remain unclear and need further study to be understood.
Alvarenga, Kátia F.; Morata, Thais C.; Lopes, Andréa Cintra; Feniman, Mariza Ribeiro; Corteletti, Lilian Cássia Bórnia Jacob
Introduction Earlier studies have demonstrated an auditory effect of lead exposure in children,but information on the effects of low chronic exposures needs to be further elucidated. Objective To investigate the effect of low chronic exposures of the auditory system in childrenwith a history of low blood lead levels, using an auditory electrophysiological test. Methods Contemporary cross-sectional cohort. Study participants underwent tympanometry, pure tone and speech audiometry, transient evoked otoacoustic emissions, and brainstem auditory evoked potentials, with blood lead monitoring over a period of 35.5 months. The study included 130 children, with ages ranging from 18 months to 14 years, 5 months (mean age 6years, 8 months ± 3 years, 2 months). Results The mean time-integrated cumulative blood lead index was 12 g/dL (SD ± 5.7, range:2.433). All participants had hearing thresholds equal to or below 20 dBHL and normal amplitudes of transient evoked otoacoustic emissions. No association was found between the absolute latencies of waves I, III, and V, the interpeak latencies I---III, III---V, and I---V, and the cumulative lead values. Conclusion No evidence of toxic effects from chronic low lead exposures was observed on the auditory function of children living in a lead contaminated area. PMID:25458254
Helmich, Rick C; Bloem, Bastiaan R; Toni, Ivan
Parkinson's disease (PD) is surprisingly heterogeneous: some patients have a prominent resting tremor, while others never develop this symptom. Here we investigate whether the functional organization of the voluntary motor system differs between PD patients with and without resting tremor, and whether these differences relate to the cerebral circuit producing tremor. We compared 18 PD patients with marked tremor, 20 PD patients without tremor, and 19 healthy controls. Subjects performed a controlled motor imagery task during fMRI scanning. We quantified imagery-related cerebral activity by contrasting imagery of biomechanically difficult and easy movements. Tremor-related activity was identified by relating cerebral activity to fluctuations in tremor amplitude, using electromyography during scanning. PD patients with tremor had better behavioral performance than PD patients without tremor. Furthermore, tremulous PD patients showed increased imagery-related activity in somatosensory area 3a, as compared with both healthy controls and to nontremor PD patients. This effect was independent from tremor-related activity, which was localized to the motor cortex, cerebellum, and thalamic ventral intermediate nucleus (VIM). The VIM, with known projections to area 3a, was unique in showing both tremor- and imagery-related responses. We conclude that parkinsonian tremor influences motor imagery by modulating central somatosensory processing through the VIM. This mechanism may explain clinical differences between PD patients with and without tremor.
Schrafl-Altermatt, Miriam; Dietz, Volker
Task-specific neural coupling during cooperative hand movements has been described in healthy volunteers, manifested by bilateral reflex electromyographic responses in forearm muscles following unilateral ulnar nerve stimulation and by task-specific activation of secondary somatosensory cortical areas (S2) in functional MRI. The aim of this study was to investigate the role of sensory input to the ipsilateral and contralateral cortex during a cooperative task. Somatosensory evoked potentials from the ulnar nerve were recorded over the ipsilateral and contralateral cortex during resting and during cooperative and noncooperative hand movements. Ipsilateral potentials with smaller amplitude were present under all conditions in almost all participants. In relation to the resting condition, the amplitudes of both the ipsilateral and the contralateral potential were reduced during the cooperative and the noncooperative tasks. Nevertheless, the reduction in amplitude was similar for the ipsilateral and the contralateral potentials in the noncooperative task, but less on the ipsilateral compared with the contralateral side during the cooperative task. The ratio of ipsilateral/contralateral somatosensory evoked potential amplitude was thus significantly larger during the cooperative task compared with the control task and the resting condition. This indicates a functional role of ipsilateral pathways connecting the cervical spinal cord with the cortex during the cooperative task. These observations favor the idea of a task-specific mediation of sensory input from both hands to the ipsilateral and contralateral hemispheres as the basis of neuronal coupling.
Patrick, G; Straumanis, J J; Struve, F A; Fitz-Gerald, M J; Manno, J E
The use of evoked potentials to study CNS effects of marihuana (THC) have produced inconsistent findings. Our previous pilot studies suggested that auditory P300 latencies and amplitudes, auditory P50 and somatosensory P30 amplitudes and brainstem auditory evoked potential latencies were altered in THC users. Because these findings were flawed by uncontrolled psychiatric diagnostic and medication variables, we undertook a controlled investigation of screened medically and psychiatrically normal THC users and controls. When age effects were controlled, THC related alterations of brain stem and both auditory and visual P300 responses could not be seen. This report extends our analyses to other auditory, somatosensory and visual evoked potentials. With the possible exception of an elevated auditory P50 amplitude, significant evoked potential correlates to daily THC use were not seen when normals were studied and age effects controlled.
Langford, Ted L.; Patterson, James H., Jr.
Several statistical procedures have been proposed as objective methods for determining evoked-potential thresholds. Data have been presented to support each of the methods, but there have not been direct comparisons using the same data. The goal of the present study was to evaluate correlation and variance ratio statistics using common data. A secondary goal was to evaluate the utility of a derived potential for determining thresholds. Chronic, bipolar electrodes were stereotaxically implanted in the inferior colliculi of six chinchillas. Evoked potentials were obtained at 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 kHz using 12-ms tone bursts and 12-ms tone bursts superimposed on 120-ms pedestal tones which were of the same frequency as the bursts, but lower in amplitude by 15 dB. Alternate responses were averaged in blocks of 200 to 4000 depending on the size of the response. Correlations were calculated for the pairs of averages. A response was deemed present if the correlation coefficient reached the 0.05 level of significance in 4000 or fewer averages. Threshold was defined as the mean of the level at which the correlation was significant and a level 5 dB below that at which it was not. Variance ratios were calculated as described by Elberling and Don (1984) using the same data. Averaged tone burst and tone burst-plus pedestal data were differenced and the resulting waveforms subjected to the same statistical analyses described above. All analyses yielded thresholds which were essentially the same as those obtained using behavioral methods. When the difference between stimulus durations is taken into account, however, evoked-potential methods produced lower thresholds than behavioral methods.
Tschentscher, Nadja; Hauk, Olaf; Fischer, Martin H.; Pulvermüller, Friedemann
The embodied cognition framework suggests that neural systems for perception and action are engaged during higher cognitive processes. In an event-related fMRI study, we tested this claim for the abstract domain of numerical symbol processing: is the human cortical motor system part of the representation of numbers, and is organization of numerical knowledge influenced by individual finger counting habits? Developmental studies suggest a link between numerals and finger counting habits due to the acquisition of numerical skills through finger counting in childhood. In the present study, digits 1 to 9 and the corresponding number words were presented visually to adults with different finger counting habits, i.e. left- and right-starters who reported that they usually start counting small numbers with their left and right hand, respectively. Despite the absence of overt hand movements, the hemisphere contralateral to the hand used for counting small numbers was activated when small numbers were presented. The correspondence between finger counting habits and hemispheric motor activation is consistent with an intrinsic functional link between finger counting and number processing. PMID:22133748
Stout, Erik E; Sirota, Mikhail G; Beloozerova, Irina N
During navigation through complex natural environments, people and animals must adapt their movements when the environment changes. The neural mechanisms of such adaptations are poorly understood, especially with respect to constraints that are unexpected and must be adapted to quickly. In this study, we recorded forelimb-related kinematics, muscle activity, and the activity of motor cortical neurons in cats walking along a raised horizontal ladder, a complex locomotion task requiring accurate limb placement. One of the crosspieces was motorized, and displaced before the cat stepped on the ladder or at different points along the cat's progression over the ladder, either towards or away from the cat. We found that, when the crosspiece was displaced before the cat stepped onto the ladder, the kinematic modifications were complex and involved all forelimb joints. When the crosspiece displaced unexpectedly while the cat was on the ladder, the kinematic modifications were minimalistic and primarily involved distal joints. The activity of M. triceps and M. extensor digitorum communis differed based on the direction of displacement. Out of 151 neurons tested, 69% responded to at least one condition; however, neurons were significantly more likely to respond when crosspiece displacement was unexpected. Most often they responded during the swing phase. These results suggest that different neural mechanisms and motor control strategies are used to overcome constraints for locomotor movements depending on whether they are known or emerge unexpectedly.
Polat, Zahra; Ataş, Ahmet
Background: In the literature, music education has been shown to enhance auditory perception for children and young adults. When compared to young adult non-musicians, young adult musicians demonstrate increased auditory processing, and enhanced sensitivity to acoustic changes. The evoked response potentials associated with the interpretation of sound are enhanced in musicians. Studies show that training also changes sound perception and cortical responses. The earlier training appears to lead to larger changes in the auditory cortex. Aims: Most cortical studies in the literature have used pure tones or musical instrument sounds as stimuli signals. The aim of those studies was to investigate whether musical education would enhance auditory cortical responses when speech signals were used. In this study, the speech sounds extracted from running speech were used as sound stimuli. Study Design: Non-randomized controlled study. Methods: The experimental group consists of young adults up to 21 years-old, all with a minimum of 4 years of musical education. The control group was selected from young adults of the same age without any musical education. The experiments were conducted by using a cortical evoked potential analyser and /m/, /t/ /g/ sound stimulation at the level of 65 dB SPL. In this study, P1 / N1 / P2 amplitude and latency values were measured. Results: Significant differences were found in the amplitude values of P1 and P2 (p<0.05). The differences among the latencies were not found to be significantly important (p>0.05). Conclusion: The results obtained in our study indicate that musical experience has an effect on the nervous system and this can be seen in cortical auditory evoked potentials recorded when the subjects hear speech. PMID:25667787
Shaw, N A
Many methods are employed in order to define more precisely the generators of an evoked potential (EP) waveform. One technique is to compare the timing of an EP whose origin is well established with that of one whose origin is less certain. In the present article, the latency of the primary cortical auditory evoked potential (PCAEP) was compared to each of the seven subcomponents which compose the brainstem auditory evoked potential (BAEP). The data for this comparison was derived from a retrospective analysis of previous recordings of the PCAEP and BAEP. Central auditory conduction time (CACT) was calculated by subtracting the latency of the cochlear nucleus BAEP component (wave III) from that of the PCAEP. It was found that CACT in humans is 12 msec which is more than double that of central somatosensory conduction time. The interpeak latencies between BAEP waves V, VI, and VII and the PCAEP were also calculated. It was deduced that all three waves must have an origin rather more caudally within the central auditory system than is commonly supposed. In addition, it is demonstrated that the early components of the middle latency AEP (No and Na) largely reside within the time domain between the termination of the BAEP components and the PCAEP which would be consistent with their being far field reflections of midbrain and subcortical auditory activity. It is concluded that as the afferent volley ascends the central auditory pathways, it generates not a sequence of high frequency BAEP responses but rather a succession of slower post-synaptic waves. The only means of reconciling the timing of the BAEP waves with that of the PCAEP is to assume that the generation of all the BAEP components must be largely restricted to a quite confined region within the auditory nerve and the lower half of the pons.
Despite its great success, the current functional magnetic resonance imaging (MRI) technique relies on changes in cerebral hemodynamic parameters to infer the underlying neural activities, and as a result is limited in its spatial and temporal resolutions. In this dissertation, we discuss the feasibility of neuronal current MRI (nc-MRI), a novel technique in which the small magnetic field changes caused by neuronal electrical activities are directly measured by MRI. Two studies are described. In the first study, we investigated the feasibility of detecting the magnetic field produced by sensory evoked potentials. To eliminate the blood-oxygen-level-dependent (BOLD) effect on the MRI signal, which confounded most previous studies, an octopus visual system model was developed, which, for the first time, allowed for an in vivo investigation of nc-MRI in a BOLD-free environment. Electrophysiological responses were measured in the octopus retina and optical lobe to guide the nc-MRI acquisition. Our results indicated that no nc-MRI signal change related to neuronal activation could be detected at 0.2°/0.2% threshold for signal phase/magnitude respectively, while robust electrophysiological responses were recorded. In the second study, we discuss the feasibility of detecting neural oscillations with MRI, Based on previous studies, a novel approach was proposed in which an external oscillatory field was exploited as the excitation pulse under a spin-locked condition. This approach has the advantages of increased sensitivity and lowered physiological noise. Successful detection of sub-nanotesla field was demonstrated in phantom. Our results suggest that evoked potentials are too weak for nc-MRI detection with the current hardware, and that previous positive findings were likely due to hemodynamic confounders. On the other hand, oscillatory magnetic field can be efficiently detected in phantom. Given the stronger equivalent current dipoles produced by neural oscillations
Ambrosini, Anna; Coppola, Gianluca; Gérardy, Pierre-Yves; Pierelli, Francesco; Schoenen, Jean
Migraine patients show interictally a strong intensity dependence of auditory evoked cortical potentials (IDAP) and a lack of habituation of evoked potentials. Photic drive on high-frequency flash stimulation is another well-known interictal feature in migraineurs, associated with alpha-rhythm hyper-synchronisation. We compared therefore the influence of light stimulation on IDAP in healthy volunteers (HV) and migraine patients. A continuous flash stimulation was delivered during the recording of auditory evoked potentials at suprathreshold increasing stimulation intensities. IDAP was measured as the amplitude/stimulus intensity function (ASF) slope. In HV, the ASF slope decreased during flash stimulation, whereas, on average, there was no significant change in migraineurs. A closer analysis of migraineurs disclosed two subgroups of patients with no detectable clinical differences: one, the largest, in which the ASF slope was normal at baseline, but increased during light stimulation, the other with an increased ASF slope at rest and a decrease during light interference. Visual sensory overload is able to increase IDAP in the majority of migraineurs, which contrasts with HV. We hypothesise that this could be due to hyper-synchronisation of the alpha rhythm because of photic drive and possibly thalamo-cortical dysfunction. A minority of migraineurs have, like HV, an IDAP reduction during light interference. They are, however, characterised, unlike most HV, by a high IDAP at baseline. Besides underscoring the pathophysiological heterogeneity of migraine, these results suggest that light interference might improve the phenotyping of migraine patients who have a normal IDAP in the resting condition.
Hu, Marian Y; Yan, Hong Young; Chung, Wen-Sung; Shiao, Jen-Chieh; Hwang, Pung-Pung
It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So far there is no proof for the detection of underwater sound above 400 Hz via a physiological approach. The controversy of whether cephalopods have a sound detection ability above 400 Hz was tested using the auditory brainstem response (ABR) approach, which has been successfully applied in fish, crustaceans, amphibians, reptiles and birds. Using ABR we found that auditory evoked potentials can be obtained in the frequency range 400 to 1500 Hz (Sepiotheutis lessoniana) and 400 to 1000 Hz (Octopus vulgaris), respectively. The thresholds of S. lessoniana were generally lower than those of O. vulgaris.
BP, a negative-going * ."" near-field wave originating in the brachial plexus, the A and B waves of Chiappa , et a]. (1980), and the NI, N2, and P2...1981) and by Chiappa , et al. (1980). Table 2 shows the baseline means and standard deviations of the SSEP peaks for all five Ss, derived from the loose...Head and Spine. Charles Thomas, Springfield, 1982, 324-378. Chiappa , K.H., Choi, S.K. and Young, R.R. Short latency somatosensory evoked potentials
Kane, Nick; Oware, Agyepong
Cardiopulmonary resuscitation, basic life support and early defibrillation are leading to more survivors of out-of-hospital cardiac arrest reaching hospital. Once stabilised on an intensive care unit, it can be difficult to predict the neurological outcome using clinical criteria alone, particularly with modern management using sedation, neuromuscular blockade and hypothermia. If we are to prevent ongoing futile life support, it is important to try to identify the majority of patients who, despite best efforts, will not make a meaningful recovery. Somatosensory evoked potentials are widely available electrophysiological tests that can provide an objective biomarker of a poor neurological outcome and assist in predicting the prognosis.
Wang, Lingling; He, Chong; Liu, Yueguang; Zhu, Lili
Under the auditory evoked brain stem potential (ABP) examination, the latent period of V wave and the intermittent periods of III-V peak and I-V peak were significantly shortened in Parkinson's disease patients of the treatment group (N = 29) after acupuncture treatment. The difference of cumulative scores in Webster's scale was also decreased in correlation analysis. The increase of dopamine in the brain and the excitability of the dopamine neurons may contribute to the therapeutic effects, in TCM terms, of subduing the pathogenic wind and tranquilizing the mind.
Christiansen, Emily F; Piniak, Wendy E D; Lester, Lori A; Harms, Craig A
Investigations into the biology of aquatic and semiaquatic species, including those involving sensory specialization, often require creative solutions to novel questions. We developed a technique for safely anesthetizing a semiaquatic chelonian species, the diamondback terrapin (Malaclemys terrapin), for measurement of auditory evoked potentials while animals were completely submerged in water. Custom-modified endotracheal tubes were used to obtain a watertight seal on both sides of the glottis and prevent aspiration of water during testing. No adverse effects were seen after the procedures, and assessment of venous blood-gas partial pressures and lactate concentrations indicated that sufficient gas exchange was maintained under anesthesia through manual ventilation. PMID:24351768
Christiansen, Emily F; Piniak, Wendy E D; Lester, Lori A; Harms, Craig A
Investigations into the biology of aquatic and semiaquatic species, including those involving sensory specialization, often require creative solutions to novel questions. We developed a technique for safely anesthetizing a semiaquatic chelonian species, the diamondback terrapin (Malaclemys terrapin), for measurement of auditory evoked potentials while animals were completely submerged in water. Custom-modified endotracheal tubes were used to obtain a watertight seal on both sides of the glottis and prevent aspiration of water during testing. No adverse effects were seen after the procedures, and assessment of venous blood-gas partial pressures and lactate concentrations indicated that sufficient gas exchange was maintained under anesthesia through manual ventilation.
Peck, C. K.; Lindsley, D. B.
Average evoked potentials (AEPs) were recorded from the optic tract, lateral geniculate nucleus, and visual cortex of cats trained to discriminate between two successive flashes of light at various interflash intervals (IFI) and a single flash. The percent of correct responses to two-flash stimuli decreased sharply as IFI decreased from 100 to 20 msec. This behavioral response decrement was paralleled by a progressive overlapping of the AEPs to the two flashes and at 20 msec the AEPs resembled those to a single flash at all levels of the visual pathways. Implications for the coding of the information relevant to the discrimination of two flashes are discussed.
Pietrowsky, R; Fehm, H L; Er, A; Bathelt, B; Born, J
Two experiments are reported, investigating the effects of the cholecystokinin analog ceruletide on central nervous activation in man. In experiment I, 0.55 micrograms/h ceruletide was infused at a constant rate during the night to study its effects on spontaneous EEG activity during sleep. In experiment II, we examined the effects of a bolus injection of ceruletide (0.5 micrograms) on components of the auditory evoked potential reflecting exogenously provoked central nervous arousal. While ceruletide had no effect on sleep, it attenuated stimulus-induced cortical arousal.
Henson, O. W., Jr.; Henson, M. M.
An analysis is made of pulse and echo orientation cries of the Mustache Bat. That bat's cries are characterized by a long, 60 to 30 msec, pure tone component and brief beginning and terminal FM sweeps. In addition to obvious echo overlap and middle ear muscle contractions, the following are examined: (1) characteristics of pulse- and echo-evoked potential under various conditions, (2) evidence of changes in hearing sensitivity during and after pulse emission, and (3) the role of the middle ear muscles in bringing about these changes.
Frizzo, Ana C F
The information presented in this paper demonstrates the author's experience in previews cross-sectional studies conducted in Brazil, in comparison with the current literature. Over the last 10 years, auditory evoked potential (AEP) has been used in children with learning disabilities. This method is critical to analyze the quality of the processing in time and indicates the specific neural demands and circuits of the sensorial and cognitive process in this clinical population. Some studies with children with dyslexia and learning disabilities were shown here to illustrate the use of AEP in this population.
Tempel, Tobias; Kubik, Veit
We investigated effects of retrieving body movements from memory on subsequent re-encoding of these movements (i.e., test-potentiated learning). In Experiment 1, participants first learned to perform 12 sequential finger movements as responses to letter stimuli. Eight of these movements then had to be recalled in response to their stimuli (initial test). Subsequently, learning trials were repeated for four of the previously to-be-retrieved movements as well as the previously not-to-be-retrieved movements. Restudy benefited from prior retrieval. In a final test, again requiring motoric recall in response to letter stimuli, performance was better for restudied items that were previously cued for retrieval as compared to items that had been restudied without prior retrieval. However, no such indirect testing benefit occurred when initial and final testing formats were incongruent, that is, when participants had to recall the stimuli in response to movements as cues at the final test. In Experiment 2, we replicated the finding of test-potentiated learning with a different design, manipulating initial-testing status between participants.
Li, Wei; Li, Mengfan; Zhao, Jing
This paper investigates controlling humanoid robot behavior via motion-onset specific N200 potentials. In this study, N200 potentials are induced by moving a blue bar through robot images intuitively representing robot behaviors to be controlled with mind. We present the individual impact of each subject on N200 potentials and discuss how to deal with individuality to obtain a high accuracy. The study results document the off-line average accuracy of 93% for hitting targets across over five subjects, so we use this major component of the motion-onset visual evoked potential (mVEP) to code people's mental activities and to perform two types of on-line operation tasks: navigating a humanoid robot in an office environment with an obstacle and picking-up an object. We discuss the factors that affect the on-line control success rate and the total time for completing an on-line operation task. PMID:25620918
Li, Wei; Li, Mengfan; Zhao, Jing
This paper investigates controlling humanoid robot behavior via motion-onset specific N200 potentials. In this study, N200 potentials are induced by moving a blue bar through robot images intuitively representing robot behaviors to be controlled with mind. We present the individual impact of each subject on N200 potentials and discuss how to deal with individuality to obtain a high accuracy. The study results document the off-line average accuracy of 93% for hitting targets across over five subjects, so we use this major component of the motion-onset visual evoked potential (mVEP) to code people's mental activities and to perform two types of on-line operation tasks: navigating a humanoid robot in an office environment with an obstacle and picking-up an object. We discuss the factors that affect the on-line control success rate and the total time for completing an on-line operation task.
Han, Chengcheng; Zhang, Sicong; Luo, Ailing; Chen, Chaoyang
Steady-state visual evoked potential (SSVEP) is one of the typical stimulation paradigms of brain-computer interface (BCI). It has become a research approach to improve the performance of human-computer interaction, because of its advantages including multiple objectives, less recording electrodes for electroencephalogram (EEG) signals, and strong anti-interference capacity. Traditional SSVEP using light flicker stimulation may cause visual fatigue with a consequent reduction of recognition accuracy. To avoid the negative impacts on the brain response caused by prolonged strong visual stimulation for SSVEP, steady-state motion visual evoked potential (SSMVEP) stimulation method was used in this study by an equal-luminance colored ring-shaped checkerboard paradigm. The movement patterns of the checkerboard included contraction and expansion, which produced less discomfort to subjects. Feature recognition algorithms based on power spectrum density (PSD) peak was used to identify the peak frequency on PSD in response to visual stimuli. Results demonstrated that the equal-luminance red-green stimulating paradigm within the low frequency spectrum (lower than 15 Hz) produced higher power of SSMVEP and recognition accuracy than black-white stimulating paradigm. PSD-based SSMVEP recognition accuracy was 88.15±6.56%. There was no statistical difference between canonical correlation analysis (CCA) (86.57±5.37%) and PSD on recognition accuracy. This study demonstrated that equal-luminance colored ring-shaped checkerboard visual stimulation evoked SSMVEP with better SNR on low frequency spectrum of power density and improved the interactive performance of BCI. PMID:28060906
Johnston, Jamie; Postlethwaite, Michael; Forsythe, Ian D
Most current clamp studies trigger action potentials (APs) by step current injection through the recording electrode and assume that the resulting APs are essentially identical to those triggered by orthodromic synaptic inputs. However this assumption is not always valid, particularly when the synaptic conductance is of large magnitude and of close proximity to the axon initial segment. We addressed this question of similarity using the Calyx of Held/MNTB synapse; we compared APs evoked by long duration step current injections, short step current injections and orthodromic synaptic stimuli. Neither injected current protocol evoked APs that matched the evoked orthodromic AP waveform, showing differences in AP height, half-width and after-hyperpolarization. We postulated that this 'error' could arise from changes in the instantaneous conductance during the combined synaptic and AP waveforms, since the driving forces for the respective ionic currents are integrating and continually evolving over this time-course. We demonstrate that a simple Ohm's law manipulation of the EPSC waveform, which accounts for the evolving driving force on the synaptic conductance during the AP, produces waveforms that closely mimic those generated by physiological synaptic stimulation. This stimulation paradigm allows supra-threshold physiological stimulation (single stimuli or trains) without the variability caused by quantal fluctuation in transmitter release, and can be implemented without a specialised dynamic clamp system. Combined with pharmacological tools this method provides a reliable means to assess the physiological roles of postsynaptic ion channels without confounding affects from the presynaptic input.
Guérit, J M
Three-modality evoked potentials (TMEPs) have been used for several years in association with the EEG as a diagnostic and prognostic tool in acute anoxic or traumatic coma. Cognitive EPs have been recently introduced. EEG and cognitive EPs provide functional assessment of the cerebral cortex. TMEP parameters can be described by two indices: the index of global cortical function (IGCF) and the index of brainstem conduction (IBSC). Although it remains a unique tool for epilepsy assessment, the value of EEG is largely limited by its high sensitivity to the electrical environmental noise, its dependence on sedative drugs, and its inability to test the brainstem. Major TMEP alterations (absence of cortical activities more than 24 hours after the onset of post-anoxic coma, major pontine involvement in head trauma) are associated in all cases with an ominous prognosis (death or vegetative state). However, even if mild TMEP changes are associated with a good prognosis in 65% (post-anoxic coma) to 90% (head trauma) of cases, some patients never recover despite exogenous TMEPs that are only mildly altered in the acute stage. Thus, cognitive EPs can usefully complement exogenous EPs as a prognostic tool in coma. Indeed, even if the absence of cognitive EPs in comatose patients does not have any prognostic value, their presence implies a very high (more than 90%) probability of consciousness recovery. The major technical challenge for the future will be the development of reliable tools for continuous EEG and TMEP monitoring.
Vrca, A; Bozicević, D; Bozikov, V; Fuchs, R; Malinar, M
In 49 printing-press workers occupationally exposed to toluene for approximately 21.6 years, the values of BEAP and VEP parameters were examined in relation to the length of exposure. With the exception of P2 wave, there was a significant increase in the latencies of all the BEAP waves examined as well as in the interpeak latency (IPL) P3-P4, whereas IPL P4-P5 decreased significantly with the length of exposure. The amplitude of all the VEP examined decreased significantly with the length of exposure. Toluene exposure was evaluated by measuring the concentration of toluene in peripheral blood and of hippuric acid in urine on Wednesday morning prior to the workshift, and of hippuric acid in urine after the workshift on the same day. According to the average concentration of hippuric acid in urine after the workshift, the levels of toluene exposure were estimated to range from 40-60 ppm. Evoked potentials were determined on Mondays 10-12 hours after a nonworking weekend.
Beyaert, C A; Haouzi, P; Marchal, F
The effect of mechanical and electrical stimulation of cervical cutaneous afferents was analysed on both the centrally induced tonic and rhythmic activities in hindlimb antagonist muscle nerves of 16 decerebrate paralysed cats. Electrical stimulation of dorsal midbrain evoked in the nerve to the tibialis anterior muscle (TAn) either rhythmic discharges (n=14), associated with tonic discharges in ten cats, or only tonic discharges (n=4). Centrally induced activity in the ipsilateral nerve to gastrocnemius medialis (GMn) occurred in fewer cats (n=12) and displayed similar patterns as in TAn. Manual traction of the scruff of the neck reduced the TAn tonic and rhythmic discharges (n=6) by 73% (P<0.05) and 71% (P<0.05), respectively, and reduced only the tonic component of GMn discharges (by 41%, n=3). Electrical stimulation (impulses 0.1-0.5 ms, 50 Hz) of cervical nerves belonging to C5 or C6 dermatomes, the intensity (0.4-4 mA) of which induced minimal inhibition of both TAn and GMn discharges, reduced significantly the tonic component of TAn discharges (by 39%, n=4). At higher intensities of electrical cervical nerve stimulation (2-6 mA) inducing maximal inhibitory effect, both tonic and rhythmic activities in TAn and GMn were both significantly reduced by, respectively, 81% and 94% in TAn (n=7), and by 49% and 43% in GMn (n=7). Electrical cervical nerve stimulation consistently reduced the isolated tonic discharge in TAn by 66% (n=4, P<0.05) and in GMn by 23% (n=3) when present. Thus the tonic component was more sensitive to inhibition than the rhythmic component of hindlimb muscle nerve activity.
de Tommaso, Marina; Difruscolo, Olimpia; Sardaro, Michele; Libro, Giuseppe; Pecoraro, Carla; Serpino, Claudia; Lamberti, Paolo; Livrea, Paolo
The present study aimed to evaluate heat pain thresholds and evoked potentials following CO(2) laser thermal stimulation (laser-evoked potentials, LEPs), during remote application of capsaicin, in migraine patients vs. non-migraine healthy controls. Twelve outpatients suffering from migraine without aura were compared with 10 healthy controls. The LEPs were recorded by 6 scalp electrodes, stimulating the dorsum of the right hand and the right supraorbital zone in basal condition, during the application of 3% capsaicin on the dorsum of the left hand and after capsaicin removal. In normal subjects, the laser pain and the N2-P2 vertex complex obtained by the hand and face stimulation were significantly reduced during remote capsaicin application, with respect to pre-and post-capsaicin conditions, while in migraine LEPs and laser pain were not significantly modified during remote painful stimulation. In migraine a defective brainstem inhibiting control may coexist with cognitive factors of focalised attention to facial pain, less sensitive to distraction by a second pain.
Kim, Soyeon; Banaschewski, Tobias; Tannock, Rosemary
Background Individuals with attention-deficit/hyperactivity disorder (ADHD) are reported to manifest visual problems (including ophthalmological and color perception, particularly for blue–yellow stimuli), but findings are inconsistent. Accordingly, this study investigated visual function and color perception in adolescents with ADHD using color Visual Evoked Potentials (cVEP), which provides an objective measure of color perception. Method Thirty-one adolescents (aged 13–18), 16 with a confirmed diagnosis of ADHD, and 15 healthy peers, matched for age, gender, and IQ participated in the study. All underwent an ophthalmological exam, as well as electrophysiological testing color Visual Evoked Potentials (cVEP), which measured the latency and amplitude of the neural P1 response to chromatic (blue–yellow, red–green) and achromatic stimuli. Result No intergroup differences were found in the ophthalmological exam. However, significantly larger P1 amplitude was found for blue and yellow stimuli, but not red/green or achromatic stimuli, in the ADHD group (particularly in the medicated group) compared to controls. Conclusion Larger amplitude in the P1 component for blue–yellow in the ADHD group compared to controls may account for the lack of difference in color perception tasks. We speculate that the larger amplitude for blue–yellow stimuli in early sensory processing (P1) might reflect a compensatory strategy for underlying problems including compromised retinal input of s-cones due to hypo-dopaminergic tone. PMID:25435188
Feuerecker, M S; Daunderer, M; Pape, N-B; Kuhnle, G E H
Intraoperative wakefulness is not only limited to adults and can also be found at a similar percentage (0.8%) in paediatric anaesthesia. For prevention of awareness neurophysiologic methods like auditory evoked potentials might be helpful. We report a case of a 2-year-old boy receiving balanced anaesthesia with sevoflurane and alfentanil. Midlatency auditory evoked potentials (MLAEPs) were recorded continuously before, during and after the surgical procedure. During the surgical procedure sevoflurane was withdrawn unintentionally. After a short period of time the boy started coughing and moved his legs, which was interpreted as insufficient analgesia. Several boli of alfentanil did not lead to the expected clinical effect on the depth of anaesthesia. After a recheck of the anaesthetic ventilator the error was determined and delivery of the volatile anaesthetic restored. The postoperative evaluation of the MLAEPs revealed the inadequate suppression of auditory processing during this incident with latencies comparable to the awake state. After reapplication of sevoflurane the MLAEPs were almost completely suppressed demonstrating adequate anesthetic depth. Exemplarily this case suggests that MLAEPs could be used to detect intraoperative awareness also in paediatric anaesthesia. Investigations to prove the validity and reproducibility of MLAEPs in children will be necessary.
Horn, Janneke; Tjepkema-Cloostermans, Marleen C
Predicting the future of patients with hypoxic-ischemic encephalopathy after successful cardiopulmonary resuscitation is often difficult. Registration of the median nerve somatosensory evoked potential (SSEP) can assist in the neurologic evaluation in these patients. In this article, the authors discuss the principles, applications, and limitations of SSEP registration in the intensive care unit, with a focus on prognostication. Registration of the SSEP is a very reliable and reproducible method, if it is performed and interpreted correctly. During SSEP recordings, great care should be taken to improve the signal-to-noise ratio. If the noise level is too high, the peripheral responses are abnormal or the response is not reproducible in a second set of stimuli; therefore, interpretation of the SSEPs cannot be done reliably. A bilaterally absent cortical SSEP response is a very reliable predictor of poor neurologic outcome in patients with HIE. It has a high specificity, but a low sensitivity, indicating that present cortical responses are a weak predictor of a good recovery. Further research is being done to increase the sensitivity. Somatosensory evoked potentials can be used in a multimodal approach for prognostication of outcome.
Schröder, Arjan; van Diepen, Rosanne; Mazaheri, Ali; Petropoulos-Petalas, Diamantis; Soto de Amesti, Vicente; Vulink, Nienke; Denys, Damiaan
Misophonia (hatred of sound) is a newly defined psychiatric condition in which ordinary human sounds, such as breathing and eating, trigger impulsive aggression. In the current study, we investigated if a dysfunction in the brain's early auditory processing system could be present in misophonia. We screened 20 patients with misophonia with the diagnostic criteria for misophonia, and 14 matched healthy controls without misophonia, and investigated any potential deficits in auditory processing of misophonia patients using auditory event-related potentials (ERPs) during an oddball task. Subjects watched a neutral silent movie while being presented a regular frequency of beep sounds in which oddball tones of 250 and 4000 Hz were randomly embedded in a stream of repeated 1000 Hz standard tones. We examined the P1, N1, and P2 components locked to the onset of the tones. For misophonia patients, the N1 peak evoked by the oddball tones had smaller mean peak amplitude than the control group. However, no significant differences were found in P1 and P2 components evoked by the oddball tones. There were no significant differences between the misophonia patients and their controls in any of the ERP components to the standard tones. The diminished N1 component to oddball tones in misophonia patients suggests an underlying neurobiological deficit in misophonia patients. This reduction might reflect a basic impairment in auditory processing in misophonia patients.
Thirumala, Parthasarathy D; Krishnaiah, Balaji; Habeych, Miguel E; Balzer, Jeffrey R; Crammond, Donald J
The primary aim of this paper is to study the pre-operative characteristics, intra-operative changes and post-operative hearing outcomes in patients after complete loss of wave V of the brainstem auditory evoked potential. We retrospectively analyzed the brainstem auditory evoked potential data of 94 patients who underwent microvascular decompression for hemifacial spasm at our institute. Patients were divided into two groups - those with and those without loss of wave V. The differences between the two groups and outcomes were assessed using t-test and chi-squared tests. In our study 23 (24%) patients out of 94 had a complete loss of wave V, with 11 (48%) patients experiencing transient loss and 12 (52%) patients experiencing permanent loss. The incidence of hearing loss in patients with no loss of wave V was 5.7% and 26% in patients who did experience wave V loss. The incidence of hearing change in patients with no loss of wave V was 12.6% and 30.43% in patients who did experience wave V loss. Loss of wave V during the procedure or at the end of procedure significantly increases the odds of hearing loss. Hearing change is a significant under-reported clinical condition after microvascular decompression in patients who have loss of wave V.
Zou, Ling; Zhang, Yingchun; Yang, Laurence T; Zhou, Renlai
The authors have developed a new approach by combining the wavelet denoising and principal component analysis methods to reduce the number of required trials for efficient extraction of brain evoked-related potentials (ERPs). Evoked-related potentials were initially extracted using wavelet denoising to enhance the signal-to-noise ratio of raw EEG measurements. Principal components of ERPs accounting for 80% of the total variance were extracted as part of the subspace of the ERPs. Finally, the ERPs were reconstructed from the selected principal components. Computer simulation results showed that the combined approach provided estimations with higher signal-to-noise ratio and lower root mean squared error than each of them alone. The authors further tested this proposed approach in single-trial ERPs extraction during an emotional process and brain responses analysis to emotional stimuli. The experimental results also demonstrated the effectiveness of this combined approach in ERPs extraction and further supported the view that emotional stimuli are processed more intensely.
Mandonnet, E; Dadoun, Y; Poisson, I; Madadaki, C; Froelich, S; Lozeron, P
Awake surgery is currently considered the best method to tailor intraparenchymatous resections according to functional boundaries. However, the exact mechanisms by which electrical stimulation disturbs behavior remain largely unknown. In this case report, we describe a new method to explore the propagation toward cortical sites of a brief pulse applied to an eloquent white matter pathway. We present a patient, operated on in awake condition for removal of a cavernoma of the left ventral premotor cortex. At the end of the resection, the application of 60Hz stimulation in the white matter of the operculum induced anomia. Stimulating the same site at a frequency of 1Hz during 70seconds allowed to record responses on electrodes put over Broca's area and around the inferior part of central sulcus. Axono-cortical evoked potentials were then obtained by averaging unitary responses, time-locked to the stimulus. We then discuss the origin of these evoked axono-cortical potentials and the likely pathway connecting the stimulation site to the recorded cortical sites.
Varcin, Kandice J; Nelson, Charles A; Ko, Jordan; Sahin, Mustafa; Wu, Joyce Y; Jeste, Shafali Spurling
Tuberous sclerosis complex is an autosomal dominant genetic disorder that confers a high risk for neurodevelopmental disorders, such as autism spectrum disorder and intellectual disability. Studies have demonstrated specific delays in visual reception skills that may predict the development of autism spectrum disorder and intellectual disability. Based on evidence for alterations in the retinogeniculate pathway in animal models of tuberous sclerosis complex, we asked whether children with tuberous sclerosis complex demonstrate alterations in early visual processing that may undermine the development of higher-level visual behaviors. Pattern-reversal visual evoked potentials were recorded in infants with tuberous sclerosis complex (n = 16) and typically developing infants (n = 18) at 12 months of age. Infants with tuberous sclerosis complex demonstrated remarkably intact visual evoked potentials even within the context of intellectual disability and epilepsy. Infants with tuberous sclerosis complex show intact visual cortical processing, suggesting that delays in visually mediated behaviors in tuberous sclerosis complex may not be rooted in early visual processing deficits.
Braverman, Eric R.; Blum, Kenneth; Damle, Uma J.; Kerner, Mallory; Dushaj, Kristina; Oscar-Berman, Marlene
Fluorodeoxyglucose (FDG) Positron Emission Topography (PET) brain hypometabolism (HM) correlates with diminished cognitive capacity and risk of developing dementia. However, because clinical utility of PET is limited by cost, we sought to determine whether a less costly electrophysiological measure, the P300 evoked potential, in combination with neuropsychological test performance, would validate PET HM in neuropsychiatric patients. We found that patients with amnestic and non-amnestic cognitive impairment and HM (n = 43) evidenced significantly reduced P300 amplitudes, delayed latencies, and neuropsychological deficits, compared to patients with normal brain metabolism (NM; n = 187). Data from patients with missing cognitive test scores (n = 57) were removed from the final sample, and logistic regression modeling was performed on the modified sample (n = 173, p = .000004). The logistic regression modeling, based on P300 and neuropsychological measures, was used to validate membership in the HM vs. NM groups. It showed classification validation in 13/25 HM subjects (52.0%) and in 125/148 NM subjects (84.5%), correlating with total classification accuracy of 79.8%. In this paper, abnormal P300 evoked potentials coupled with cognitive test impairment validates brain metabolism and mild/moderate cognitive impairment (MCI). To this end, we cautiously propose incorporating electrophysiological and neuropsychological assessments as cost-effective brain metabolism and MCI indicators in primary care. Final interpretation of these results must await required additional studies confirming these interesting results. PMID:23526928
Wang, Shou-Jen; Jaw, Fu-Shan; Young, Yi-Ho
This study combined bone-conducted vibration (BCV) stimulation with triaxial accelerometry to correlate the acceleration magnitudes of BCV stimuli with ocular vestibular-evoked myogenic potential (oVEMP) test results. Fourteen healthy volunteers underwent oVEMP test using BCV stimuli with simultaneous monitoring the triaxial acceleration. All (100%) subjects exhibited clear oVEMPs in response to BCV stimuli from a vibrator. The lowest acceleration magnitudes for eliciting oVEMPs along the x-, y- and z-axes were 0.05±0.01 g, 0.16±0.08 g, and 0.04±0.01 g, respectively, exhibiting significantly higher acceleration magnitude along the y-axis than those along the x- and z-axes. In addition, significantly positive correlations were noted between the acceleration magnitude along each axis and the oVEMP amplitude. In conclusion, measuring the acceleration magnitude throughout oVEMP testing revealed a significant correlation between linear acceleration and oVEMP responses. Restated, increasing acceleration magnitude may have more synchronization of firing of vestibular afferents, resulting in more synchronized evoked potentials and greater oVEMP amplitude.
Subramanian, Senthil Kumar; Gaur, Giriwar Singh; Narayan, Sunil K
Visual Evoked Potentials (VEPs) are evoked potentials generated in response to visual stimuli. The flash VEP (FVEP) is used less frequently than pattern-reversal VEP (PR-VEP) because; it shows great variations in both latency and amplitude in normal subjects. The advantage of FVEP is its feasibility in non-cooperative subjects, which circumvents the major limitation of PR-VEP. The present study was undertaken to assess the effect of change of color of flashlight on variability of FVEP latencies. Healthy subjects in the age group of 18-30 years underwent the standard stimulus using white light, followed by altered stimuli done with red and blue light. 2 trials were given for each eye, for each type of stimulus. The same set of studies was repeated at the same clock time the following day. The inter-individual and intra-individual variability in the peak latency of P2 and N2 waveforms was assessed using coefficient of variation (COV). Both inter-individual and intra-individual variability was less when monochromatic light was used. Between red and blue FVEP, inter-individual variability was less in blue FVEP and the results of intra-individual variability was inconclusive. Monochromatic stimulation preferably with blue light reduced both inter-individual and intra-individual variability seen in latency of P2 and N2 waveforms in FVEP and hence recommended in preference to standard white stimulus for FVEP recording.
Hill, Randy J.; Mann, David A.
Auditory evoked potentials (AEPs) have become commonly used to measure hearing thresholds in fish. However, it is uncertain how well AEP thresholds match behavioral hearing thresholds and what effect variability in electrode placement has on AEPs. In the first experiment, the effect of electrode placement on AEPs was determined by simultaneously recording AEPs from four locations on each of 12 goldfish, Carassius auratus. In the second experiment, the hearing sensitivity of 12 goldfish was measured using both classical conditioning and AEP's in the same setup. For behavioral conditioning, the fish were trained to reduce their respiration rate in response to a 5 s sound presentation paired with a brief shock. A modified staircase method was used in which 20 reversals were completed for each frequency, and threshold levels were determined by averaging the last 12 reversals. Once the behavioral audiogram was completed, the AEP measurements were made without moving the fish. The recording electrode was located subdermally over the medulla, and was inserted prior to classical conditioning to minimize handling of animal. The same sound stimuli (pulsed tones) were presented and the resultant evoked potentials were recorded for 1000-6000 averages. AEP input-output functions were then compared to the behavioral audiogram to compare techniques for estimating behavioral thresholds from AEP data.
Trenado, Carlos; Haab, Lars; Strauss, Daniel J
Auditory evoked cortical potentials (AECP) are well established as diagnostic tool in audiology and gain more and more impact in experimental neuropsychology, neuro-science, and psychiatry, e.g., for the attention deficit disorder, schizophrenia, or for studying the tinnitus decompensation. The modulation of AECP due to exogenous and endogenous attention plays a major role in many clinical applications and has experimentally been studied in neuropsychology. However the relation of corticothalamic feedback dynamics to focal and non-focal attention and its large-scale effect reflected in AECPs is far from being understood. In this paper, we model neural correlates of auditory attention reflected in AECPs using corticothalamic feedback dynamics. We present a mapping of a recently developed multiscale model of evoked potentials to the hearing path and discuss for the first time its neurofunctionality in terms of corticothalamic feedback loops related to focal and non-focal attention. Our model reinforced recent experimental results related to online attention monitoring using AECPs with application as objective tinnitus decompensation measure. It is concluded that our model presents a promising approach to gain a deeper understanding of the neurodynamics of auditory attention and might be use as an efficient forward model to reinforce hypotheses that are obtained from experimental paradigms involving AECPs.
Jeon, Eun Kyung; Chiou, Li-Kuei; Kirby, Benjamin; Karsten, Sue; Turner, Christopher; Abbas, Paul
Objective Nucleus Hybrid CI users hear low-frequency sounds via acoustic stimulation and high frequency sounds via electrical stimulation. This within-subject study compares three different methods of coordinating programming of the acoustic and electrical components of the Hybrid device. Speech perception and cortical auditory evoked potentials (CAEP) were used to assess differences in outcome. The goals of this study were to determine (1) if the evoked potential measures could predict which programming strategy resulted either in better outcome on the speech perception task or was preferred by the listener, and (2) whether CAEPs could be used to predict which subjects benefitted most from having access to the electrical signal provided by the Hybrid implant. Design CAEPs were recorded from 10 Nucleus Hybrid CI users. Study participants were tested using three different experimental MAPs that differed in terms of how much overlap there was between the range of frequencies processed by the acoustic component of the Hybrid device and range of frequencies processed by the electrical component. The study design included allowing participants to acclimatize for a period of up to 4 weeks with each experimental program prior to speech perception and evoked potential testing. Performance using the experimental MAPs was assessed using both a closed-set consonant recognition task and an adaptive test that measured the signal to noise ratio that resulted in 50% correct identification of a set of 12 spondees presented in background noise (SNR-50). Long-duration, synthetic vowels were used to record both the cortical P1-N1-P2 “onset” response and the auditory “change” or ACC response. Correlations between the evoked potential measures and performance on the speech perception tasks are reported. Results Differences in performance using the three programming strategies were not large. Peak-to-peak amplitude of the AAC response was not found to be sensitive enough to
Roman, Robert; Brázdil, Milan; Chládek, Jan; Rektor, Ivan; Jurák, Pavel; Světlák, Miroslav; Damborská, Alena; Shaw, Daniel J; Kukleta, Miloslav
A hippocampal-prominent event-related potential (ERP) with a peak latency at around 450 ms is consistently observed as a correlate of hippocampal activity during various cognitive tasks. Some intracranial EEG studies demonstrated that the amplitude of this hippocampal potential was greater in response to stimuli requiring an overt motor response, in comparison with stimuli for which no motor response is required. These findings could indicate that hippocampal-evoked activity is related to movement execution as well as stimulus evaluation and associated memory processes. The aim of the present study was to investigate the temporal relationship between the hippocampal negative potential latency and motor responses. We analyzed ERPs recorded with 22 depth electrodes implanted into the hippocampi of 11 epileptic patients. Subjects were instructed to press a button after the presentation of a tone. All investigated hippocampi generated a prominent negative ERP peaking at ~420 ms. In 16 from 22 cases, we found that the ERP latency did not correlate with the reaction time; in different subjects, this potential could either precede or follow the motor response. Our results indicate that the hippocampal negative ERP occurs independently of motor execution. We suggest that hippocampal-evoked activity, recorded in a simple sensorimotor task, is related to the evaluation of stimulus meaning within the context of situation.
Puta, Christian; Franz, Marcel; Blume, Kathrin R.; Gabriel, Holger H. W.; Miltner, Wolfgang H. R.; Weiss, Thomas
Chronic low back pain (CLBP) was shown to be associated with longer reflex response latencies of trunk muscles during external upper limb perturbations. One theoretical, but rarely investigated possibility for longer reflex latencies might be related to modulated somatosensory information processing. Therefore, the present study investigated somatosensory evoked potentials (SEPs) to median nerve stimulation in CLBP patients and healthy controls (HC). Latencies of the peripheral N9 SEP component were used as the primary outcome. In addition, latencies and amplitudes of the central N20 SEP component, sensory thresholds, motor thresholds and nerve conduction velocity were also analyzed in CLBP patients and HC. There is a trend for the CLBP patients to exhibit longer N9 latencies at the ipsilateral Erb’s point compared to HC. This trend is substantiated by significantly longer N9 latencies in CLBP patients compared to normative data. None of the other parameters showed any significant difference between CLBP patients and HC. Overall, our data indicate small differences of the peripheral N9 SEP component; however, these differences cannot explain the reflex delay observed in CLBP patients. While it was important to rule out the contribution of early somatosensory processing and to elucidate its contribution to the delayed reflex responses in CLBP patients, further research is needed to find the primary source(s) of time-delayed reflexes in CLBP. PMID:27799904
Zhang, Wenjuan; Zhou, Renlai; Wang, Qingguo; Zhao, Yan; Liu, Yanfeng
The present event-related potentials (ERPs) study set out to investigate the effect of neuroticism on emotion evaluation during the menstrual cycle, with high and low neuroticism females viewing and evaluating valence and arousal of emotional pictures in the menstruation, late follicular and luteal phases. Behavioral results revealed no group or phase effect. ERPs data showed modulations of the menstrual cycle and neuroticism on the late positive potential (LPP), with the larger LPP (300-1000 ms post-stimulus) during the late follicular phase than that during the luteal phase and larger LPP (1000-3000 ms post-stimulus) in the high neuroticism group than that in the low neuroticism group. Furthermore, significant positive correlations between the LPP amplitudes and valence and arousal evaluations were observed mainly in the high neuroticism group. The present study provides electrophysiological evidences that the LPP evoked by emotional pictures are modulated both by the menstrual cycle and neuroticism.
Matthews, W B; Read, D J; Pountney, E
The effects of raising body temperature on the visual (VEP) and somatosensory (SEP) evoked potentials were observed in normal subjects and in patients with multiple sclerosis. The amplitude of the VEP was significantly reduced to the same degree after heating in normal subjects and in patients with multiple sclerosis but there was no effect on the latency of the potential. Changes in amplitude could not be related to reduction in acuity. In contrast, the cervical SEP was greatly disorganised after heating in many patients with multiple sclerosis while the only effect in normal subjects was to reduce the latency by increasing peripheral conduction velocity. These results suggest that heat caused conduction block in demyelinated axons in the sensory pathways of the cervical spinal cord. PMID:438834
Todd, N P M; Govender, S; Colebatch, J G
Todd et al. (2014ab) have recently demonstrated the presence of vestibular-dependent contributions to auditory evoked potentials (AEPs) when passing through the vestibular threshold as determined by vestibular evoked myogenic potentials (VEMPs), including a particular deflection labeled as an N42/P52 prior to the long-latency AEPs N1 and P2. In this paper we report the results of an experiment to determine the effect of inter-stimulus interval (ISI) and regularity on potentials recorded above and below VEMP threshold. Five healthy, right-handed subjects were recruited and evoked potentials were recorded to binaurally presented sound stimulation, above and below vestibular threshold, at seven stimulus rates with ISIs of 212, 300, 424, 600, 848, 1200 and 1696 ms. The inner five intervals, i.e. 300, 424, 600, 848, 1200 ms, were presented twice in both regular and irregular conditions. ANOVA on the global field power (GFP) were conducted for each of four waves, N42, P52, N1 and P2 with factors of intensity, ISI and regularity. Both N42 and P52 waves showed significant ANOVA effects of intensity but no other main effects or interactions. In contrast both N1 and P2 showed additional effects of ISI, as well as intensity, and evidence of non-linear interactions between ISI and intensity. A source analysis was carried out consistent with prior work suggesting that when above vestibular threshold, in addition to bilateral superior temporal cortex, ocular, cerebellar and cingulate sources are recruited. Further statistical analysis of the source currents indicated that the origin of the interactions with intensity may be the ISI sensitivity of the vestibular-dependent sources. This in turn may reflect a specific vestibular preference for stimulus rates associated with locomotion, i.e. rates close to 2 Hz, or ISIs close to 500 ms, where saccular afferents show increased gain and the corresponding reflexes are most sensitive.
Billings, Curtis J; Tremblay, Kelly L; Souza, Pamela E; Binns, Malcolm A
Hearing aid amplification can be used as a model for studying the effects of auditory stimulation on the central auditory system (CAS). We examined the effects of stimulus presentation level on the physiological detection of sound in unaided and aided conditions. P1, N1, P2, and N2 cortical evoked potentials were recorded in sound field from 13 normal-hearing young adults in response to a 1000-Hz tone presented at seven stimulus intensity levels. As expected, peak amplitudes increased and peak latencies decreased with increasing intensity for unaided and aided conditions. However, there was no significant effect of amplification on latencies or amplitudes. Taken together, these results demonstrate that 20 dB of hearing aid gain affects neural responses differently than 20 dB of stimulus intensity change. Hearing aid signal processing is discussed as a possible contributor to these results. This study demonstrates (1) the importance of controlling for stimulus intensity when evoking responses in aided conditions, and (2) the need to better understand the interaction between the hearing aid and the CAS.
Stone, James L; Calderon-Arnulphi, Mateo; Watson, Karriem S; Patel, Ketan; Mander, Navneet S; Suss, Nichole; Fino, John; Hughes, John R
The authors review the brainstem auditory evoked potential (BAEP), and present studies on 40 healthy subjects. In addition to the conventional click evoked BAEP, three modified BAEP examinations were performed. The modified BAEP tests include a 1,000 Hz tone-burst BAEP, and more rapid rate binaural click and 1,000 Hz tone-burst BAEPs-each of the last two studies performed at four diminishing moderate intensities. In addition to the usual parameters, the authors examined the Wave V to Vn interpeak latency, and stimulus intensity versus Wave V latency and amplitude functions in the rapid rate binaural studies. Studies were also repeated on healthy subjects in a dependant head position in an attempt to increase intracranial pressure. Discussion centers on the BAEP, its current utility in medicine, unique neurophysiology, and literature support that the above modifications could increase the practicality of the test in patients at risk with intracranial lesions and perhaps improve the feasibility for real-time continuous or frequent monitoring in the future.
Guo, Fei; Hong, Bo; Gao, Xiaorong; Gao, Shangkai
This paper presents a novel brain-computer interface (BCI) based on motion-onset visual evoked potentials (mVEPs). mVEP has never been used in BCI research, but has been widely studied in basic research. For the BCI application, the brief motion of objects embedded into onscreen virtual buttons is used to evoke mVEP that is time locked to the onset of motion. EEG data registered from 15 subjects are used to investigate the spatio-temporal pattern of mVEP in this paradigm. N2 and P2 components, with distinct temporo-occipital and parietal topography, respectively, are selected as the salient features of the brain response to the attended target that the subject selects by gazing at it. The computer determines the attended target by finding which button elicited prominent N2/P2 components. Besides a simple feature extraction of N2/P2 area calculation, the stepwise linear discriminant analysis is adopted to assess the target detection accuracy of a five-class BCI. A mean accuracy of 98% is achieved when ten trials data are averaged. Even with only three trials, the accuracy remains above 90%, suggesting that the proposed mVEP-based BCI could achieve a high information transfer rate in online implementation.
Atwood, H L; Parnas, H; Parnas, I; Wojtowicz, J M
1. Quantal transmitter release was examined at nerve terminals of the excitatory motor axon of the crayfish opener muscle. The magnitude of synaptic currents, recorded with macro-patch electrodes at a nerve terminal, served as a measure of quantal size. Transmitter release was initiated by pulses of depolarizing current applied intracellularly to the axonal terminals after application of tetrodotoxin. Quantal release was altered by a variety of methods and the resulting quantal output and quantal size were measured. 2. Amplitude distributions of quantal events were obtained during experimental manipulations which altered the rate of quantal release by up to 25-fold. These manipulations consisted of: varying pulse amplitude or pulse duration; facilitating the release by prolonged depolarization; and application of a potassium channel blocker, 4-aminopyridine. 3. The amplitude of quantal events is impervious to marked changes in presynaptic depolarization and is not affected by experimental procedures which promote accumulation of calcium ions in the terminals. The vesicular mechanism of release, in which transmitter substance is prepackaged in vesicles which individually undergo exocytosis at a release zone, could account for the observed results. PMID:2888878
Buchner, H; Ferbert, A
Principally, in the fourth update of the rules for the procedure to finally determine the irreversible cessation of function of the cerebrum, the cerebellum and the brainstem, the importance of an electroencephalogram (EEG), somatosensory evoked potentials (SEP) and brainstem auditory evoked potentials (BAEP) are confirmed. This paper presents the reliability and validity of the electrophysiological diagnosis, discusses the amendments in the fourth version of the guidelines and introduces the practical application, problems and sources of error.An EEG is the best established supplementary diagnostic method for determining the irreversibility of clinical brain death syndrome. It should be noted that residual brain activity can often persist for many hours after the onset of brain death syndrome, particularly in patients with primary brainstem lesions. The derivation and analysis of an EEG requires a high level of expertise to be able to safely distinguish artefacts from primary brain activity. The registration of EEGs to demonstrate the irreversibility of clinical brain death syndrome is extremely time consuming.The BAEPs can only be used to confirm the irreversibility of brain death syndrome in serial examinations or in the rare cases of a sustained wave I or sustained waves I and II. Very often, an investigation cannot be reliably performed because of existing sound conduction disturbances or failure of all potentials even before the onset of clinical brain death syndrome. This explains why BAEPs are only used in exceptional cases.The SEPs of the median nerve can be very reliably derived, are technically simple and with few sources of error. A serial investigation is not required and the time needed for examination is short. For these reasons SEPs are given preference over EEGs and BAEPs for establishing the irreversibility of clinical brain death syndrome.
Kitzmiller, Joseph P; Hansford, Derek J; Fortin, Linda D; Obrietan, Karl H; Bergdall, Valerie K; Beversdorf, David Q
A sub-dural surface microelectrode array designed to detect micro-field evoked potentials has been developed. The device is comprised of an array of 350-microm square gold contacts, with bidirectional spacing of 150 microm, contained within a polyimide Kapton material. Cytotoxicity testing suggests that the device is suitable for use with animal and human patients. Implementation of the device in animal studies revealed that reliable evoked potentials could be acquired. Further work will be needed to determine how these micro-field potentials, which demonstrate selectivity for one eye, relate to the distribution of the ocular dominance columns of the occipital cortex.
Tandonnet, Christophe; Garry, Michael I; Summers, Jeffery J
To make a decision may rely on accumulating evidence in favor of one alternative until a threshold is reached. Sequential-sampling models differ by the way of accumulating evidence and the link with action implementation. Here, we tested a model's prediction of an early action implementation specific to potential actions. We assessed the dynamics of action implementation in go/no-go and between-hand choice tasks by transcranial magnetic stimulation of the motor cortex (single- or paired-pulse TMS; 3-ms interstimulus interval). Prior to implementation of the selected action, the amplitude of the motor evoked potential first increased whatever the visual stimulus but only for the hand potentially involved in the to-be-produced action. These findings suggest that visual stimuli can trigger an early motor activation specific to potential actions, consistent with race-like models with continuous transmission between decision making and action implementation.
Xie, Jun; Xu, Guanghua; Wang, Jing; Zhang, Sicong; Zhang, Feng; Li, Yeping; Han, Chengcheng; Li, Lili
Although noise has a proven beneficial role in brain functions, there have not been any attempts on the dedication of stochastic resonance effect in neural engineering applications, especially in researches of brain-computer interfaces (BCIs). In our study, a steady-state motion visual evoked potential (SSMVEP)-based BCI with periodic visual stimulation plus moderate spatiotemporal noise can achieve better offline and online performance due to enhancement of periodic components in brain responses, which was accompanied by suppression of high harmonics. Offline results behaved with a bell-shaped resonance-like functionality and 7–36% online performance improvements can be achieved when identical visual noise was adopted for different stimulation frequencies. Using neural encoding modeling, these phenomena can be explained as noise-induced input-output synchronization in human sensory systems which commonly possess a low-pass property. Our work demonstrated that noise could boost BCIs in addressing human needs. PMID:24828128
Background Bilaterally absent N20 components of the sensory evoked potentials (SEP) from the median nerve are regarded as accurately predicting poor outcome after cardiac arrest. Case presentation We are reporting on a patient, who regained consciousness despite this ominous finding. Early after cardiac arrest, MRI showed signal alterations in diffusion weighted imaging (DWI) bilaterally in the primary visual and sensorimotor cortex and in the basal ganglia. SEP were repeatedly absent. The patient survived shut out form sensory and visual experience and locked in for voluntary movements, but kept her verbal competence in several languages. Conclusion SEP inform about integrity only of a narrow cortical strip. It is unguarded, but common practice, to conclude from absent SEP, that a patient has suffered diffuse cortical damage after cardiac arrest. Cerebral MRI with DWI helps to avoid this prognostic error and furthers understanding of the sometimes very peculiar state of mind after cardiac arrest. PMID:24720818
Liavas, A P; Moustakides, G V; Henning, G; Psarakis, E Z; Husar, P
The task of objective perimetry is to scan the visual field and find an answer about the function of the visual system. Flicker-burst stimulation--a physiological sensible combination of transient and steady-state stimulation--is used to generate deterministic sinusoidal responses or visually evoked potentials (VEP's) at the visual cortex, which are derived from the electroencephalogram by a suitable electrode array. In this paper we develop a new method for the detection of VEP's. Based on the periodogram of a time-series, we test the data for the presence of hidden periodic components, which correspond to steady-state VEP's. The method is applied successfully to real data.
Moore, U J; Marsh, V R; Ashton, C H; Seymour, R A
1. The effects of aspirin 1000 mg, paracetamol 1000 mg, codeine 60 mg on somatosensory evoked potentials (SEPs) were measured in a four-way cross-over study. 2. SEPs were elicited by electrical stimulation of the skin overlying the digital nerve at intensities close to pain threshold. 3. Amplitudes and latencies of both early and late SEPs were recorded, as well as first sensory threshold and subjective pain threshold. 4. None of the study medications affected the amplitude or latency of the late SEP components (100-250 ms post-stimulus). The amplitude of early components (15-30 ms post-stimulus) was also unaffected, but aspirin shortened the latency 30 min after ingestion. 5. Sensory detection and pain threshold to electrical skin stimulation were also unaffected by any of the study medications despite subjective central effects with codeine. PMID:8562292
Supin, A Ia
Focal evoked potentials were elicited in the rabbit visual cortex by punctiform light stimuli and analyzed by the current source density technique. They contained two main components. The first component was generated by local sink at depths form 0.6 to 1.0 mm (layer IV) with 30 ms latency and peak time about 50 ms. The second one was generated by less local sink at depths form 0.2-0.3 to 1.3-1.5 mm (layers III-VI) with peak time 90-100 ms. These two sinks are considered as active and indicating the localization of depolarizing synapses. Passive sources are dissipated around the zone of the active sinks.
Chan, Hsiao-Lung; Hsu, Wen-Chun; Meng, Ling-Fu; Sun, Mu-Hui
The Alzheimer's disease (AD) has a wide spectrum of symptoms, ranging from cognition dysfunction to behavior disturbances and functional impairment. The evoked cerebral potentials by specific paradigms are useful for disclosing neuropsychological activities. The evolution of AD is accompanied by progressive cognitive impairment which may result in a difficulty to recognize or comprehend gestures. In the present study, a visual tool-using gesture paradigm was employed to assess the cognitive functions of 16 probable AD patients, 17 subjects mild cognitive impairment (MCI), and 17 age-matched control subjects. Each subject was conducted by visual stimuli by a series of pictures, each displaying randomly a gesture with correctly or incorrectly using a tool. The P300 amplitude was further used as a parameter to build classifiers based on support vector machine.
Norcia, Anthony M
Linking propositions have played an important role in refining our understanding of the relationship between neural activity and perception. Over the last 40 years, visual evoked potentials (VEPs) have been used in many different ways to address questions of the relationship between neural activity and perception. This review organizes and discusses this research within the linking proposition framework developed by Davida Teller, and her colleagues. A series of examples from the VEP literature illustrates each of the five classes of linking propositions originally proposed by Davida Teller. The related concept of the bridge locus-the site at which neural activity can be said to first be proscriptive of perception-is discussed and a suggestion is made that the concept be expanded to include an evolution over time and cortical area.
Rusina, Robert; Barek, Stephane; Vaculin, Simon; Azérad, Jean; Rokyta, Richard
While the effect of cortex stimulation on pain control is widely accepted, its physiological basis remains poorly understood. We chose an animal model of pain to study the influence of sensorimotor cortex stimulation on tooth pulp stimulation evoked potentials (TPEPs). Fifteen awake rats implanted with tooth pulp, cerebral cortex, and digastric muscle electrodes were divided into three groups, receiving 60 Hz, 40 Hz and no cortical stimulation, respectively. TPEPs were recorded before, one, three and five hours after continuous stimulation. We observed an inverse relationship between TPEP amplitude and latency with increasing tooth pulp stimulation. The amplitudes of the early components of TPEPs increased and their latency decreased with increasing tooth pulp stimulation intensity. Cortical stimulation decreased the amplitude of TPEPs; however, neither the latencies of TPEPs nor the jaw-opening reflex were changed after cortical stimulation. The decrease in amplitude of TPEPs after cortical stimulation may reflect its anti-nociceptive effect.
Genna, C; Artoni, F; Fanciullacci, C; Chisari, C; Oddo, C M; Micera, S
Perception of tactile stimuli elicits Somatosensory Evoked Potentials (SEPs) that can be recorded via non-invasive electroencephalography (EEG). However, it is not yet clear how SEPs localization, shape and latency are modulated by different stimuli during mechanical tactile stimulation of fingertips. The aim of this work is thus to characterize SEPs generated by the tactile perception of gratings during dynamic passive stimulation of the dominant fingertip by means of a mechatronic platform. Results show that a random sequence of stimuli elicited SEPs with two long-latency components: (i) a negative deflection around 140 ms located in the frontal-central-parietal side in the contralateral hemisphere; (ii) a positive deflection around 250 ms located in the frontal-central midline. Time-frequency analysis revealed significant continuous bilateral desynchronization in the alpha band throughout the passive stimulation. These results are a fundamental step towards building a model of brain responses during perception of tactile stimuli for future benchmarking studies.
Weber, Konrad P; Rosengren, Sally M
Over the last years, vestibular-evoked myogenic potentials (VEMPs) have been established as clinical tests of otolith function. Complementary to the cervical VEMPs, which assess mainly saccular function, ocular VEMPs (oVEMPs) test predominantly utricular otolith function. oVEMPs are elicited either with air-conducted (AC) sound or bone-conducted (BC) skull vibration and are recorded from beneath the eyes during up-gaze. They assess the vestibulo-ocular reflex and are a crossed excitatory response originating from the inferior oblique eye muscle. Enlarged oVEMPs have proven to be sensitive for screening of superior canal dehiscence, while absent oVEMPs indicate a loss of superior vestibular nerve otolith function, often seen in vestibular neuritis (VN) or vestibular Schwannoma.
Kumar, Kaushlendra; Bhat, Jayashree S; Sequeira, Nimalka Maria; Bhojwani, Kiran M
One of the recent diagnostic tests to assess the function of otolithic organs is through vestibular evoked myogenic potential (VEMP) testing. There are equivocal findings on effect of aging on ocular VEMP (oVEMP) parameters with reference to latencies. Hence this study was taken up to investigate the age related changes in oVEMP parameters. This present study considered 30 participants in each age group i.e., young adults, middle-aged adults and older adults. oVEMP were recorded using insert earphone at 100dBnHL at 500hZ short duration tone burst. The results showed in older adult significant difference in response rate, latencies and amplitude as compared to young and middle adult. Hence age should be taken into consideration when interpreting oVEMP results.
Pearce, Wendy; Golding, Maryanne; Dillon, Harvey
Infants with auditory neuropathy and possible hearing impairment are being identified at very young ages through the implementation of hearing screening programs. The diagnosis is commonly based on evidence of normal cochlear function but abnormal brainstem function. This lack of normal brainstem function is highly problematic when prescribing amplification in young infants because prescriptive formulae require the input of hearing thresholds that are normally estimated from auditory brainstem responses to tonal stimuli. Without this information, there is great uncertainty surrounding the final fitting. Cortical auditory evoked potentials may, however, still be evident and reliably recorded to speech stimuli presented at conversational levels. The case studies of two infants are presented that demonstrate how these higher order electrophysiological responses may be utilized in the audiological management of some infants with auditory neuropathy.
Golding, Maryanne; Pearce, Wendy; Seymour, John; Cooper, Alison; Ching, Teresa; Dillon, Harvey
Finding ways to evaluate the success of hearing aid fittings in young infants has increased in importance with the implementation of hearing screening programs. Cortical auditory evoked potentials (CAEP) can be recorded in infants and provides evidence for speech detection at the cortical level. The validity of this technique as a tool of hearing aid evaluation needs, however, to be demonstrated. The present study examined the relationship between the presence/absence of CAEPs to speech stimuli and the outcomes of a parental questionnaire in young infants who were fitted with hearing aids. The presence/absence of responses was determined by an experienced examiner as well as by a statistical measure, Hotelling's T(2). A statistically significant correlation between CAEPs and questionnaire scores was found using the examiner's grading (rs = 0.45) and using the statistical grading (rs = 0.41), and there was reasonably good agreement between traditional response detection methods and the statistical analysis.
Molnár, M; Karmos, G; Csépe, V
In this article, intracortical evoked potentials (EPs) were recorded simultaneously from six different depths of the auditory cortex of freely moving cats. The effect of (a) different states of vigilance and that of atropine, (b) classical aversive conditioning, and (c) the effect of atropine during conditioning was studied on the intracortical EP profiles. Atropine induced EP changes that were similar to those seen in slow wave sleep. During classical aversive conditioning signal stimuli elicited a middle-latency negative EP component which was localized to the superficial cortical layers. Atropine (2 mg/kg body weight) did not abolish the appearance of this component but only increased its latency. It is proposed that the cholinergic part of the ascending activating system did not play an essential role in its generation.
Supin, Alexander Ya.; Nachtigall, Paul E.; Pawloski, Jeffrey; Au, Whitlow W. L.
Auditory brainstem responses (ABRs) were recorded in a false killer whale while the animal echolocated a target. The ABR collection was triggered by echolocation clicks of the animal. In these conditions, the recorded ABR pattern contained a duplicate set of waves. A comparison of ABR wave delays recorded during echolocation with those recorded during regular external stimulation with experimenter generated clicks showed that the first set of waves may be a response to the emitted click whereas the second one may be a response to the echo. Both responses, to the emitted click and to the echo, were of comparable amplitude in spite of the intensity difference of these two sounds that may differ by more than 40 dB near the animal's head. This finding indicates the presence of some mechanism of releasing responses to echoes from masking by loud emitted clicks. The evoked-potential method may be productive to investigate these mechanisms.
Vrca, A; Karacić, V; Bozicević, D; Bozikov, V; Malinar, M
Brainstem auditory evoked potentials (BAEPs) were examined in 49 workers employed in a printing press, who were occupationally exposed to low concentrations of toluene for an average of 20.3 years, and in 59 subjects in a control group. In the group of exposed workers, a significant decrease was found in all wave amplitudes examined, a significant prolongation of P1 wave latency, and an increased interval of interpeak latencies (P3-P5), indicating that the extramedullary and high medullary part of the auditory pathway are biologically most frequently affected by chronic exposure to low concentrations of toluene. The level of exposure to toluene in both groups was evaluated by defining the concentration of toluene in peripheral blood and the concentration of hippuric acid and ortho-cresol in urine.
Vrca, A; Karacić, V; Bozicević, D; Fuchs, R; Malinar, M
Cognitive evoked potentials VEP P300 were examined in 49 workers at printing press occupationally exposed to low concentrations of toluene for averagely 20 years, and in 59 control subjects. The exposure level of toluene was evaluated in randomly selected subgroups comprising 36 exposed and 27 control subjects. The concentrations of toluene were measured in peripheral blood on Wednesday morning before entering the work area, while the hippuric acid in urine was measured before and after entering the work area. The results show that the absolute number of exposed subjects displaying lower amplitude of cognitive wave VEP P300R and prolonged latency of the accompanying spontaneous wave VEP P300F was significantly greater than that of the controls.
Costa-Faidella, Jordi; Grimm, Sabine; Slabu, Lavinia; Díaz-Santaella, Francisco; Escera, Carles
Single neurons in the primary auditory cortex of the cat show faster adaptation time constants to short- than long-term stimulus history. This ability to encode the complex past auditory stimulation in multiple time scales would enable the auditory system to generate expectations of the incoming stimuli. Here, we tested whether large neural populations exhibit this ability as well, by recording human auditory evoked potentials (AEP) to pure tones in a sequence embedding short- and long-term aspects of stimulus history. Our results yielded dynamic amplitude modulations of the P2 AEP to stimulus repetition spanning from milliseconds to tens of seconds concurrently, as well as amplitude modulations of the mismatch negativity AEP to regularity violations. A simple linear model of expectancy accounting for both short- and long-term stimulus history described our results, paralleling the behavior of neurons in the primary auditory cortex.
Vanetsian, G L; Pavlova, I V
Averaged auditory evoked potentials (AEPs) were recorded in symmetric points of the frontal cortex and dorsal hippocampus of cats performing acquired conditioned food-procuring reaction reinforced in 100% cases, urgent transition to 30%-reinforcement, and return to 100%-reinforcement. Emotional stress estimated by a heart rate rise developed during increased food motivation of a cat as well as during change in ordinary food-procuring stereotype. The emotional stress was accompanied by a high positive correlation of cortical and hippocampal AEPs. Decrease in the stress level led to a drop between AEP correlations and appearance of their negative values. In emotional stress, the interactions between the frontal cortex and dorsal hippocampus were asymmetric: right-side correlations were higher.
ITO, Yosuke; MAEHARA, Seiya; ITOH, Yoshiki; MATSUI, Ai; HAYASHI, Miri; KUBO, Akira; UCHIDE, Tsuyoshi
The purpose of this study was to investigate the effects of refractive error on canine visual evoked potentials with pattern stimulation (P-VEP). Six normal beagle dogs were used. The refractive power of the recorded eyes was measured by skiascopy. The refractive power was corrected to −4 diopters (D) to +2 D using contact lens. P-VEP was recorded at each refractive power. The stimulus pattern size and distance were 50.3 arc-min and 50 cm. The P100 appeared at almost 100 msec at −2 D (at which the stimulus monitor was in focus). There was significant prolongation of the P100 implicit time at −4, −3, 0 and +1 D compared with −2 D, respectively. We concluded that the refractive power of the eye affected the P100 implicit time in canine P-VEP recording. PMID:26655769
Chen, Zhe; Ohara, Shinji; Cao, Jianting; Vialatte, François; Lenz, Fred A; Cichocki, Andrzej
This article is devoted to statistical modeling and analysis of electrocorticogram (ECoG) signals induced by painful cutaneous laser stimuli, which were recorded from implanted electrodes in awake humans. Specifically, with statistical tools of factor analysis and independent component analysis, the pain-induced laser-evoked potentials (LEPs) were extracted and investigated under different controlled conditions. With the help of wavelet analysis, quantitative and qualitative analyses were conducted regarding the LEPs' attributes of power, amplitude, and latency, in both averaging and single-trial experiments. Statistical hypothesis tests were also applied in various experimental setups. Experimental results reported herein also confirm previous findings in the neurophysiology literature. In addition, single-trial analysis has also revealed many new observations that might be interesting to the neuroscientists or clinical neurophysiologists. These promising results show convincing validation that advanced signal processing and statistical analysis may open new avenues for future studies of such ECoG or other relevant biomedical recordings.
Wu, Zhenghua; Yao, Dezhong
Due to the relative noise and artifact insensitivity, steady-state visual evoked potential (SSVEP) has been used increasingly in the study of a brain-computer interface (BCI). However, SSVEP is still influenced by the same frequency component in the spontaneous EEG, and it is meaningful to find a parameter that can avoid or decrease this influence to improve the transfer rate and the accuracy of the SSVEP-based BCI. In this work, with wavelet analysis, a new parameter named stability coefficient (SC) was defined to measure the stability of a frequency, and then the electrode with the highest stability was selected as the signal electrode for further analysis. After that, the SC method and the traditional power spectrum (PS) method were used comparatively to recognize the stimulus frequency from an analogous BCI data constructed from a real SSVEP data, and the results showed that the SC method is better for a short time window data.
Kumar, V; Tandon, O P
The effects of rubber factory environment on functional integrity of auditory pathway have been studied in forty rubber factory workers using Brainstem Auditory Evoked Potentials (BAEPs) technique to detect early subclinical impairments. Results indicate that 47 percent of the workers showed abnormalities in prolongations of either peak latencies or interpeak latencies when compared with age and sex matched control subjects not exposed to rubber factory environment. The percent distribution of abnormalities (ears affected) were in the order of extrusion and calendering (75%) > vulcanising (41.66%) > mixing (28.57%) > loading and dispatch (23.07%) > tubing (18.75%) sections of the factory. This incidence of abnormalities may be attributed to solvents being used in these units of rubber factory. These findings suggest that rubber factory environment does affect auditory pathway in the brainstem.
Russo, A.; Tomarchio, S.; Pero, G.; Consoli, G.; Marina, R.; Rizzari, C.; Schiliro, G.
Visual-evoked potentials (VEPs) were studied in 55 asymptomatic children with leukemia or solid tumors in remission in order to detect subclinical demyelination of the optic pathway after CNS prophylaxis. In group I (11 patients with ALL studied prospectively), VEP latency was increased in ten after cranial radiation (CR) as compared with previous values. Group II (18 patients with ALL in maintenance) and group III (16 patients with ALL off therapy) were studied retrospectively and VEP latency was found above normal limits in 33 and 31%, respectively. In group IV (four patients with solid tumors and six with leukemia, all of whom received no CR), VEP latency was normal despite periodical intrathecal methotrexate administrations to five of them. The authors conclude that CR determines a slowing of conduction on VEP test, probably due to demyelination of the optic pathway, in a high proportion of patients. The future clinical significance of these findings must be established throughout a prolonged follow-up period.
Odonnell, Brian F.; Cohen, Ronald A.
The N2-P3 complex and other endogenous components of human evoked potential provide a set of tools for the investigation of human perceptual and cognitive processes. These multidimensional measures of central nervous system bioelectrical activity respond to a variety of environmental and internal factors which have been experimentally characterized. Their application to the analysis of human performance in naturalistic task environments is just beginning. Converging evidence suggests that the N2-P3 complex reflects processes of stimulus evaluation, perceptual resource allocation, and decision making that proceed in parallel, rather than in series, with response generation. Utilization of these EP components may provide insights into the central nervous system mechanisms modulating task performance unavailable from behavioral measures alone. The sensitivity of the N2-P3 complex to neuropathology, psychopathology, and pharmacological manipulation suggests that these components might provide sensitive markers for the effects of environmental stressors on the human central nervous system.
Kingma, C M; Wit, H P
Vestibular evoked myogenic potentials (VEMPs) were measured in 22 unilateral Menière patients with monaural and binaural stimulation with 250 and 500 Hz tone bursts. For all measurement situations significantly lower VEMP amplitudes were on average measured at the affected side compared to the unaffected side. Unilateral Menière patients have, in contrast to normal subjects, asymmetric VEMPs, indicating a permanently affected vestibular (most likely otolith) system at the side of hearing loss. The diagnostic value of VEMP amplitude asymmetry measurement in individual patients is low, because of the large overlap of the VEMP amplitude asymmetry range for unilateral Menière patients with that for normal subjects.
Xiong, Kai; Hou, Minxian; Ye, Guanrong
The equi-luminance of color stimulus in normal subjects is characterized by L-cone and M-cone activation in retina. For the protanopes and deuternopes, only the activations of one relevant remaining cone type should be considered. The equi-luminance turning curve was established for the recorded visual evoked potentials (VEPs) of the luminance changes of the red and green color stimulus, and the position of the equi-luminance was used to define the kind and degree of color vision deficiencies. In the test of 47 volunteers we got the VEP traces and the equi-luminance turning curves, which was in accordance with the judgment by the pseudoisochromatic plate used in clinic. The method fulfills the objective and quantitative requirements in color vision deficiencies test.
Zwierko, Teresa; Lubiński, Wojciech; Lesiakowski, Piotr; Steciuk, Hanna; Piasecki, Leszek; Krzepota, Justyna
This longitudinal study investigated visual evoked potentials (VEPs) in 11 young female volleyball players who participated in extensive training for 2 years. The control group consisted of 7 age-matched female students who were not involved in any regular sports activity. Recordings of VEPs were performed twice: baseline recording (i.e., before training began) and after 2 years of systematic, volleyball-specific athletic training. The effect of athletic training on visual signal conductivity was assessed by recording the latency of N75, P100 and N135 components of the VEPs waveform. Extensive experience with volleyball training reduced signal conductivity time through visual pathway. Specifically, the latency of P100 was reduced on average by 2.2 ms during binocular viewing. Moreover, athletes had reduced N75 latency (difference of 3.3 ms) for visual stimuli that generated greater response from peripheral retina. These results indicate that sport training can affect very early sensory processing in athletes.
Frederiksen, J L; Petrera, J
To establish the value of visual evoked potentials (VEPs) for monitoring disease evolution, we undertook a population-based study of 90 untreated patients 12 to 57 years of age (median, 32 years) at the onset of optic neuritis (ON) and after 2, 4, 12, and 52 weeks. Optic neuritis was monosymptomatic (AMON) in 58 patients and part of the clinically definite multiple sclerosis (CDMS) in 32 patients. The VEP was abnormal in eyes with acute ON in 69 (77%) of 90 patients at onset and in 80 (89%) of 90 patients at one or more of the follow-up sessions. In eyes with acute ON, normalization of an initially abnormal VEP was observed during 1-year follow-up in 13 (19%) of 69 patients. At onset of ON, VEP was abnormal in 35% of the clinically unaffected eyes. By parametric analysis of variance, the latencies (P = 0.0058), the amplitudes (P = 0.0298), and the combined VEP scores (P = 0.0345) in the eyes with acute ON were significantly associated with the time after onset. The latencies were influenced by the presence of CDMS (P = 0.0033), whereas the amplitudes were influenced by visual acuity (P = 0.0000). When visual acuity was included in a multifactor model, the time after onset was, however, not significantly associated with the amplitude (P = 0.8826). The mean latency of the VEPs in eyes with acute ON was significantly shorter in AMON than in ON as part of CDMS. This study provides evidence that VEP abnormality is often transitory, and that VEP often normalizes during follow-up. The diagnostic yield is increased by repeating VEP in the spontaneous course of acute ON. Visual evoked potential is a sensitive tool for revealing subclinical lesions.
Fisher, Jonathan A N; Huang, Stanley; Ye, Meijun; Nabili, Marjan; Wilent, W Bryan; Krauthamer, Victor; Myers, Matthew R; Welle, Cristin G
Rapid detection and diagnosis of a traumatic brain injury (TBI) can significantly improve the prognosis for recovery. Helmet-mounted sensors that detect impact severity based on measurements of acceleration or pressure show promise for aiding triage and transport decisions in active, field environments such as professional sports or military combat. The detected signals, however, report on the mechanics of an impact rather than directly indicating the presence and severity of an injury. We explored the use of cortical somatosensory evoked electroencephalographic potentials (SSEPs) to detect and track, in real-time, neural electrophysiological abnormalities within the first hour following head injury in an animal model. To study the immediate electrophysiological effects of injury in vivo, we developed an experimental paradigm involving focused ultrasound that permits continuous, real-time measurements and minimizes mechanical artifact. Injury was associated with a dramatic reduction of amplitude over the damaged hemisphere directly after the injury. The amplitude systematically improved over time but remained significantly decreased at one hour, compared with baseline. In contrast, at one hour there was a concomitant enhancement of the cortical SSEP amplitude evoked from the uninjured hemisphere. Analysis of the inter-trial electroencephalogram (EEG) also revealed significant changes in low-frequency components and an increase in EEG entropy up to 30 minutes after injury, likely reflecting altered EEG reactivity to somatosensory stimuli. Injury-induced alterations in SSEPs were also observed using noninvasive epidermal electrodes, demonstrating viability of practical implementation. These results suggest cortical SSEPs recorded at just a few locations by head-mounted sensors and associated multiparametric analyses could potentially be used to rapidly detect and monitor brain injury in settings that normally present significant levels of mechanical and electrical
Wang, Wei; Wang, Yehan; Fu, Xianming; Liu, Jianhui; He, Chengsen; Dong, Yi; Livesley, W John; Jang, Kerry L
Patients with personality disorders such as the histrionic type exaggerate their responses when receiving external social or environmental stimuli. We speculated that they might also show an augmenting pattern of the auditory evoked potential N1-P2 component in response to stimuli with increasing levels of intensity, a response pattern that is thought to be inversely correlated with cerebral serotonin (5-HT) activity. To test this hypothesis, we collected auditory evoked potentials in 191 patients with personality disorders (19 patients with the paranoid type, 12 schizoid, 14 schizotypal, 18 antisocial, 15 borderline, 13 histrionic, 17 narcissistic, 25 avoidant, 30 dependent and 28 obsessive-compulsive) and 26 healthy volunteers. Their personality traits were measured using the Dimensional Assessment of Personality Pathology-Basic Questionnaire (DAPP-BQ). Compared with healthy subjects and other patient groups, the histrionic group scored higher on the basic traits Affective Instability, Stimulus Seeking, Rejection and Narcissism, and on the higher traits Emotional Dysregulation and Dissocial, than the other groups, and the schizoid group scored lower on most of the DAPP-BQ basic and higher traits. In addition, the histrionic group showed steeper amplitude/stimulus intensity function (ASF) slopes at three midline scalp electrodes than the healthy controls or the other patient groups. The ASF slopes were not correlated with any DAPP-BQ traits in the total sample of 217 subjects. However, the DAPP-BQ basic trait Rejection was positively correlated with the ASF slopes at all three electrode sites in the histrionic group. The increased intensity dependence of the auditory N1-P2 component might indicate that cerebral 5-HT neuronal activity is, on average, weak in the histrionic patients.
Qu, Xuefeng; Yan, Jiaqing; Li, Xiaoli; Zhang, Peixun; Liu, Xianzeng
Purpose: Traditionally, the topography of somatosensory evoked potentials (SEPs) is generated based on amplitude and latency. However, this operation focuses on the physical morphology and field potential-power, so it suffers from difficulties in performing identification in an objective manner. In this study, measurement of the synchronization of SEPs is proposed as a method to explore brain functional networks as well as the plasticity after peripheral nerve injury. Method: SEPs elicited by unilateral sciatic nerve stimulation in twelve adult male Sprague-Dawley (SD) rats in the normal group were compared with SEPs evoked after unilateral sciatic nerve hemisection in four peripheral nerve injured SD rats. The characterization of synchronized networks from SEPs was conducted using equal-time correlation, correlation matrix analysis, and comparison to randomized surrogate data. Eigenvalues of the correlation matrix were used to identify the clusters of functionally synchronized neuronal activity, and the participation index (PI) was calculated to indicate the involvement of each channel in the cluster. The PI value at the knee point of the PI histogram was used as a threshold to demarcate the cortical boundary. Results: Ten out of the twelve normal rats showed only one synchronized brain network. The remaining two normal rats showed one strong and one weak network. In the peripheral nerve injured group, only one synchronized brain network was found in each rat. In the normal group, all network shapes appear regular and the network is largely contained in the posterior cortex. In the injured group, the network shapes appear irregular, the network extends anteriorly and posteriorly, and the network area is significantly larger. There are considerable individual variations in the shape and location of the network after peripheral nerve injury. Conclusion: The proposed method can detect functional brain networks. Compared to the results of the traditional SEP
Yassin, M.; Scholfield, C. N.
1. The role of glutamate in producing tissue damage during cerebral anoxia was investigated in brain slices using antagonists to the NMDA and AMPA receptor types. 2. Tissue function was assessed by field recordings of the synaptically evoked potentials elicited by stimulating the main afferent input to the olfactory cortex, the lateral olfactory tract. Anoxia was produced by bathing the slice in glucose-free solution equilibrated with 95% N2/5% CO2. 3. The amount of recovery of the evoked potential was inversely dependent on the period of anoxia and temperature: at 24 degrees C, 15 min of anoxia followed by reoxygenation produced a 14.6 +/- 4.1% recovery whereas there was no recovery at 35 degrees C. 4. Dizocilpine and ketamine had no effect on synaptic transmission in oxygenated media but following anoxia they produced an increased recovery of the responses: from 14.6 +/- 4.1% to 48.3 +/- 7.8% for dizocilpine (10 microM) and 21.6 +/- 7.7% to 87.2 +/- 7.1% for ketamine (200 microM); the tissue endurance to anoxia was increased by around 5 min. 5. Blockade of the AMPA receptors did not influence recovery in spite of the depressed synaptic transmission. A similar synaptic attenuation produced by lignocaine provided some increase in post-anoxic recovery. 6. The NMDA receptor antagonist, AP5, antagonized NMDA at 50 microM by 3.7 fold and at 200 microM by 15 fold but only 200 microM increased post-anoxic recovery. This suggests that a substantial degree of NMDA antagonist is required before anoxic tissue damage due to NMDA receptor activation can be nullified. The antagonist to the glycine binding site, 7-chlorokynurenic acid also increased recovery.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7913373
Raz, J; Biggins, C A; Turetsky, B; Fein, G
We describe a statistical frequency domain approach to localizing equivalent dipole generators of human brain evoked potentials. The frequency domain representation allows considerable data reduction, constrains the magnitude function of the dipoles to be smooth, and accounts for the statistical properties of the background EEG. A previous paper described a restrictive model in which the dipole orientations were assumed to be fixed over time, and only one dipole was allowed. In this paper, we consider the more general model in which the orientation can vary over time, and which includes multiple dipole generators. The varying orientation model has the practical advantage of being more nearly linear and more flexible than the fixed orientation model, which facilitates convergence of the iterative fitting algorithm. We suggest a measure of goodness-of-fit that compares the likelihood of the dipole model with the likelihoods of saturated and null models. We report the results of fitting the model to recorded auditory and visual evoked potentials. A single dipole with fixed orientation seems to be an adequate model of the auditory midlatency response, while two dipoles with varying orientation are needed to fit the later P200 component. Analysis of the visual P100 response to unilateral stimulation localized a generator in the contralateral occipital cortex, as expected from anatomical considerations. A two-dipole model fit the visual P100 response of bilateral stimulations, and the locations of the two dipoles were similar to the locations obtained by single-dipole fits to the responses to left and right unilateral stimuli.
Hernández, Oscar H; García-Martínez, Rolando; Monteón, Victor
In previous papers, we have shown that parameters of the omitted stimulus potential (OSP), which occurs at the end of a train of sensory stimuli, strongly depend on the modality. A train of stimuli also produces long-latency evoked potentials (LLEP) at the beginning of the train. This study is an extension of the OSP research, and it tested the relationship between parameters (ie, rate of rise, amplitude, and peak latency) of the P2 waves when trains of auditory, visual, or somatosensory stimuli were applied. The dynamics of the first 3 potentials in the train, related to habituation, were also studied. Twenty healthy young college volunteers participated in the study. As in the OSP, the P2 was faster and higher for auditory than for visual or somatosensory stimuli. The first P2 was swifter and higher than the second and the third potentials. The strength of habituation depends on the sensory modality and the parameter used. All these findings support the view that many long-latency brain potentials could share neural mechanisms related to wave generation.
dos Santos Filha, Valdete Alves Valentins; Samelli, Alessandra Giannella; Matas, Carla Gentile
Background Tinnitus is an important occupational health concern, but few studies have focused on the central auditory pathways of workers with a history of occupational noise exposure. Thus, we analyzed the central auditory pathways of workers with a history of occupational noise exposure who had normal hearing threshold, and compared middle latency auditory evoked potential in those with and without noise-induced tinnitus. Material/Methods Sixty individuals (30 with and 30 without tinnitus) underwent the following procedures: anamnesis, immittance measures, pure-tone air conduction thresholds at all frequencies between 0.25–8 kHz, and middle latency auditory evoked potentials. Results Quantitative analysis of latencies and amplitudes of middle latency auditory evoked potential showed no significant differences between the groups with and without tinnitus. In the qualitative analysis, we found that both groups showed increased middle latency auditory evoked potential latencies. The study group had more alterations of the “both” type regarding the Na-Pa amplitude, while the control group had more “electrode effect” alterations, but these alterations were not significantly different when compared to controls. Conclusions Individuals with normal hearing with or without tinnitus who are exposed to occupational noise have altered middle latency auditory evoked potential, suggesting impairment of the auditory pathways in cortical and subcortical regions. Although differences did not reach significance, individuals with tinnitus seemed to have more abnormalities in components of the middle latency auditory evoked potential when compared to individuals without tinnitus, suggesting alterations in the generation and transmission of neuroelectrical impulses along the auditory pathway. PMID:26358094
Sclar, G; Ohzawa, I; Freeman, R D
We have studied visual evoked potentials (VEP) in the cat using dichoptically presented sinusoidal gratings. Our goals were to determine if binocular disparity causes differential responses in the VEP, and to examine the effects of monocular deprivation and convergent or divergent strabismus on the degree of binocular summation. Binocular disparity in stimuli causes no regular alterations of visual evoked responses, except at very low spatial frequencies. However, this apparent selectivity is probably due to luminance modulation in the central retina at low frequencies. The insensitivity to binocular disparity establishes that binocular summation in the VEP may be estimated without regard to the relative phase of gratings presented to the two eyes. Binocular summation of the VEP was examined in normal animals. We found that the ratio of the binocularly evoked response to the largest monocular response (averaged across spatial frequency) ranged from 1.27 to 2.12 (4 animals) and had a mean of 1.48. These values fall within the range which has been reported for human subjects. The degree of summation might be expected to be greatly reduced in strabismic and monocularly deprived animals, in which the majority of the cells are functionally monocular. While summation was found to be reduced in 5 esotropic (convergent) animals (range = 1.13-1.24; mean = 1.18) it was approximately normal in three exotropic (divergent) animals (range = 1.29-2.12; mean = 1.61). However, single unit recordings carried out on the same animals show similar reductions of cells that can be driven through either eye for both groups of animals. Recordings from three monocularly deprived animals, on the other hand, show evidence of binocular interaction in the form of suppression. In this case, response amplitudes obtained using binocular stimulation were consistently and substantially smaller than those obtained from the normal eye alone (range = 0.76-0.85; mean = 0.80). We conclude that convergent
Ben David, Y; Tal, J; Podoshin, L; Fradis, M; Sharf, M; Pratt, H; Faraggi, D
To investigate the effect of ovarian steroids on the brain stem during changes of estrogen and progesterone blood levels, we recorded brain stem auditory evoked potentials with increased stimulus rates from 26 women treated for sterility by menotropins (Pergonal and Metrodin). These women were divided into three groups according to their estrogen and progesterone blood levels. The brain stem auditory evoked potential results revealed a significant delay of peak III only, with an increased stimulus rate in the group with the highest estrogen level. Estrogen may cause a brain stem synaptic impairment, presumably because of ischemic changes, and thus also may be responsible for a higher incidence of Bell's palsy during pregnancy.
Smith, Zachary M; Delgutte, Bertrand
Bilateral cochlear implantation seeks to restore the advantages of binaural hearing to the profoundly deaf by providing binaural cues normally important for accurate sound localization and speech reception in noise. Psychophysical observations suggest that a key issue for the implementation of a successful binaural prosthesis is the ability to match the cochlear positions of stimulation channels in each ear. We used a cat model of bilateral cochlear implants with eight-electrode arrays implanted in each cochlea to develop and test a noninvasive method based on evoked potentials for matching interaural electrodes. The arrays allowed the cochlear location of stimulation to be independently varied in each ear. The binaural interaction component (BIC) of the electrically evoked auditory brainstem response (EABR) was used as an assay of binaural processing. BIC amplitude peaked for interaural electrode pairs at the same relative cochlear position and dropped with increasing cochlear separation in either direction. To test the hypothesis that BIC amplitude peaks when electrodes from the two sides activate maximally overlapping neural populations, we measured multiunit neural activity along the tonotopic gradient of the inferior colliculus (IC) with 16-channel recording probes and determined the spatial pattern of IC activation for each stimulating electrode. We found that the interaural electrode pairings that produced the best aligned IC activation patterns were also those that yielded maximum BIC amplitude. These results suggest that EABR measurements may provide a method for assigning frequency-channel mappings in bilateral implant recipients, such as pediatric patients, for which psychophysical measures of pitch ranking or binaural fusion are unavailable.
Won, Dong-Ok; Hwang, Han-Jeong; Dähne, Sven; Müller, Klaus-Robert; Lee, Seong-Whan
Objective. Most existing brain-computer interface (BCI) designs based on steady-state visual evoked potentials (SSVEPs) primarily use low frequency visual stimuli (e.g., <20 Hz) to elicit relatively high SSVEP amplitudes. While low frequency stimuli could evoke photosensitivity-based epileptic seizures, high frequency stimuli generally show less visual fatigue and no stimulus-related seizures. The fundamental objective of this study was to investigate the effect of stimulation frequency and duty-cycle on the usability of an SSVEP-based BCI system. Approach. We developed an SSVEP-based BCI speller using multiple LEDs flickering with low frequencies (6-14.9 Hz) with a duty-cycle of 50%, or higher frequencies (26-34.7 Hz) with duty-cycles of 50%, 60%, and 70%. The four different experimental conditions were tested with 26 subjects in order to investigate the impact of stimulation frequency and duty-cycle on performance and visual fatigue, and evaluated with a questionnaire survey. Resting state alpha powers were utilized to interpret our results from the neurophysiological point of view. Main results. The stimulation method employing higher frequencies not only showed less visual fatigue, but it also showed higher and more stable classification performance compared to that employing relatively lower frequencies. Different duty-cycles in the higher frequency stimulation conditions did not significantly affect visual fatigue, but a duty-cycle of 50% was a better choice with respect to performance. The performance of the higher frequency stimulation method was also less susceptible to resting state alpha powers, while that of the lower frequency stimulation method was negatively correlated with alpha powers. Significance. These results suggest that the use of higher frequency visual stimuli is more beneficial for performance improvement and stability as time passes when developing practical SSVEP-based BCI applications.
Hosono, Yuki; Kitaoka, Kazuyoshi; Urushihara, Ryo; Séi, Hiroyoshi; Kinouchi, Yohsuke
It has been reported that negative emotional changes and conditions affect the visual faculties of humans at the neural level. On the other hand, the effects of emotion on color perception in particular, which are based on evoked potentials, are unknown. In the present study, we investigated whether different anxiety levels affect the color information processing for each of 3 wavelengths by using flash visual evoked potentials (FVEPs) and State-Trait Anxiety Inventory. In results, significant positive correlations were observed between FVEP amplitudes and state or trait anxiety scores in the long (sensed as red) and middle (sensed as green) wavelengths. On the other hand, short-wavelength-evoked FVEPs were not correlated with anxiety level. Our results suggest that negative emotional conditions may affect color sense processing in humans.
Myllymaa, Sami; Myllymaa, Katja; Korhonen, Hannu; Töyräs, Juha; Jääskeläinen, Juha E; Djupsund, Kaj; Tanila, Heikki; Lappalainen, Reijo
Modern microfabrication techniques make it possible to develop microelectrode arrays that may be utilized not only in neurophysiological research but also in the clinic, e.g. in neurosurgery and as elements of neural prostheses. The aim of this study was to test whether a flexible microelectrode array is suitable for recording cortical surface field potentials in rats. Polyimide-based microelectrode arrays were fabricated by utilizing microfabrication techniques e.g. photolithography and magnetron sputter deposition. The present microelectrode array consists of eight platinum microelectrodes (round-shaped, Ø: 200 microm), transmission lines and connector pads sandwiched between two thin layers of biocompatible polyimide. The microelectrode arrays were electrochemically characterized by impedance spectroscopy in physiological saline solution and successfully tested in vivo by conducting acute and chronic measurements of evoked potentials on the surface of rat cortex. The arrays proved excellent flexibility and mechanical strength during handling and implantation onto the surface of cortex. The excellent electrochemical characteristics and stable in vivo recordings with high spatiotemporal resolution highlight the potential of these arrays. The fabrication protocol described here allows implementation of several other neural interfaces with different layouts, material selections or target areas either for recording or stimulation purposes.
Rajna, Péter; Hidasi, Zoltán; Waldemar, Szelenberger
Considering the limits of the traditional EEG techniques the authors review the main methods and clinical importance of the event-related EEG investigations. According to methods, these can be classified into the spectral analysis of task-related, pre-task and post-task recordings as well as stimulus-controlled measurements based on evoked potential techniques. The main results of clinical studies on the event-related EEG methods are summarized according to chief disease groups (Alzheimer's disease, epilepsy, schizophrenia, Parkinson's disease, dyslexia, depression). The authors discuss the stimulus-dependent EEG discharges (P300, cognitive potential) in detail. They present the meta-analysis of 224 recent publications on human application of these methods. They analyze the involved scientific areas and the frequency by which these methods were applied in each. Following this, the results of 83 selected clinical studies are summarized. The frequency of the application of the various event-related EEG methods and the tested wave components and other parameters are listed. Finally a summary of the main clinical results is presented again by groups of diseases (schizophrenia, behavioral disorders, traumatic lesions, enuresis nocturna, depression, memory disturbance and dementia, drug effect). Finally, the potential perspectives and the limitations of the event-related EEG methods are briefly discussed.
Bergin, M J; Bird, P A; Vlajkovic, S M; Thorne, P R
Permanent high frequency (>4 kHz) sensorineural hearing loss following middle ear surgery occurs in up to 25% of patients. The aetiology of this loss is poorly understood and may involve transmission of supra-physiological forces down the ossicular chain to the cochlea. Investigating the mechanisms of this injury using animal models is challenging, as evaluating cochlear function with evoked potentials is confounded when ossicular manipulation disrupts the normal air conduction (AC) pathway. Bone conduction (BC) using clinical bone vibrators in small animals is limited by poor transducer output at high frequencies sensitive to trauma. The objectives of the present study were firstly to evaluate a novel high frequency bone conduction transducer with evoked auditory potentials in a guinea pig model, and secondly to use this model to investigate the impact of middle ear surgical manipulation on cochlear function. We modified a magnetostrictive device as a high frequency BC transducer and evaluated its performance by comparison with a calibrated AC transducer at frequencies up to 32 kHz using the auditory brainstem response (ABR), compound action potential (CAP) and summating potential (SP). To mimic a middle ear traumatising stimulus, a rotating bur was brought in to contact with the incudomalleal complex and the effect on evoked cochlear potentials was observed. BC-evoked potentials followed the same input-output function pattern as AC potentials for all ABR frequencies. Deterioration in CAP and SP thresholds was observed after ossicular manipulation. It is possible to use high frequency BC to evoke responses from the injury sensitive basal region of the cochlea and so not rely on AC with the potential confounder of conductive hearing loss. Ongoing research explores how these findings evolve over time, and ways in which injury may be reduced and the cochlea protected during middle ear surgery.
Wu, Shao-Wei; Wang, Yi-Chia; Hsieh, Paul-Chen; Tseng, Ming-Tsung; Chiang, Ming-Chang; Chu, Chih-Pang; Feng, Fang-Ping; Lin, Yea-Huey; Hsieh, Sung-Tsang; Chao, Chi-Chao
Contact heat-evoked potentials (CHEPs) have become an established method of assessing small-fiber sensory nerves; however, their potential as a physiological signature of neuropathic pain symptoms has not been fully explored. To investigate the diagnostic efficacy in examining small-fiber sensory nerve degeneration, the relationship with skin innervations, and clinical correlates with sensory symptoms, we recruited 188 patients (115 men) with length-dependent sensory symptoms and reduced intraepidermal nerve fiber (IENF) density at the distal leg to perform CHEP, quantitative sensory testing, and nerve conduction study. Fifty-seven age- and sex-matched controls were enrolled for comparison of CHEP and skin innervation. Among patients with neuropathy, 144 patients had neuropathic pain and 64 cases had evoked pain. Compared with quantitative sensory testing and nerve conduction study parameters, CHEP amplitudes showed the highest sensitivity for diagnosing small-fiber sensory nerve degeneration and exhibited the strongest correlation with IENF density in multiple linear regression. Contact heat-evoked potential amplitudes were strongly correlated with the degree of skin innervation in both patients with neuropathy and controls, and the slope of the regression line between CHEP amplitude and IENF density was higher in patients with neuropathy than in controls. Patients with evoked pain had higher CHEP amplitude than those without evoked pain, independent of IENF density. Receiver operating characteristic analysis showed that CHEP had better performance in diagnosing small-fiber sensory nerve degeneration than thermal thresholds. Furthermore, CHEPs showed superior classification accuracy with respect to evoked pain. In conclusion, CHEP is a sensitive tool to evaluate pathophysiology of small-fiber sensory nerve and serves as a physiological signature of neuropathic pain symptoms.
Moncho, Dulce; Poca, Maria A; Minoves, Teresa; Ferré, Alejandro; Cañas, Victoria; Sahuquillo, Juan
OBJECTIVE In this study, the authors describe the brainstem auditory evoked potential (BAEP) and somatosensory evoked potential (SSEP) alterations found in a large cohort of patients with Chiari malformation Type 1 (CM-1), the relationship between the BAEPs/SSEPs and the clinical findings, the abnormalities in patients with associated syringomyelia, and the clinical and neuroradiological risk factors that are associated with abnormal evoked potentials (EPs). METHODS A prospectively collected database containing 545 patients with CM-1 was queried to search for patients satisfying the following criteria: 1) an age of at least 14 years, 2) neuroradiological criteria of CM-1, 3) no prior Chiari-related surgeries, and 4) preoperative EP studies conducted at the authors' institution. The 200 patients included in this cohort were classified into CM-0, CM-1, and CM-1.5 subtypes. Linear, planimetric, and angular measurements of the posterior fossa were conducted, as well as syringomyelia measurements. Two separate multiple logistic regression models were used, one to predict the covariates associated with abnormal BAEPs, and a second model to explore the variables associated with an abnormal SSEP. In these models, the BAEPs and SSEPs were dichotomized as being normal or abnormal. RESULTS Headaches were the main symptom in 70.5% of the patients, and Valsalva-induced headaches were most frequent in patients with CM-1 and CM-1.5 compared with patients with CM-0 (p = 0.031). BAEPs were abnormal in 38.5% of patients, and abnormal SSEPs were found in 43.5% of the entire cohort. Syringomyelia was most frequent in patients with CM-0 (64.3%) and CM-1 (51.1%) compared with those with CM-1.5 (34.7%; p = 0.03). Age (OR 1.03, 95% CI 1.00-1.06), the degree of tonsillar herniation (OR 1.08, 95% CI 1.01-1.16), and lower cranial nerve dysfunction (OR 3.99, 95% CI 1.29-14.01) had a statistically significant correlation with abnormal BAEPs. Only age (OR 1.07, 95% CI 1.04-1.10) and the degree
Jehle, T; Ehlken, D; Wingert, K; Feuerstein, T J; Bach, M; Lagrèze, W A
Quantification of visual function is essential for the impact of disease models and their treatment. Recently, we introduced a chronic implant model to record visual evoked potentials (VEP) in awake Brown-Norway rats. Here, we investigated the hemispheric distribution of VEP after monocular stimulation, the chronic electrode implantation and the influence of commonly used anesthetics. Potentials were recorded by electrodes, implanted epidurally over the superior colliculus. The entire visual field of the rat was stimulated. Flicker stimuli were modulated in luminance with a modulation depth from 5 to 80% at 7.5 Hz and flashes with a modulation depth of >95% in a frequency range of 2.9-38 Hz. Recordings were constant over 9 days. When one eye was blinded, the potentials recorded from the contralateral side were not affected, while the potentials of the ipsilateral side were markedly reduced. Further, potentials of awake animals were compared with those receiving general anesthetics. For one group of rats (n = 8), we administered isoflurane by inhalation in five concentrations. Four different groups (n = 7-11) were given choralhydrate (200 and 400 mg/kg) and the combination of ketamine/xyaline (65/7 or 130/14 mg/kg, respectively) intraperitoneally. Isoflurane depressed the VEP in a concentration-dependent manner. Treatment with chloralhydrate and ketamine/xyaline increased the VEP at low concentrations and depressed it in high concentrations. The new VEP paradigm assesses distinct qualities of contrast vision in rats. All tested narcotics alter VEP amplitudes and can be avoided.
Castro, Ana; Amorim, Pedro; Nunes, Catarina S; de Almeida, Fernando Gomes
Somatosensory evoked potentials (SEPs) have been linked to noxious activation and stimulus intensity. In this exploratory study we investigated the impact of anaesthetic drugs on SEPs and pain ratings, to assess their applicability as an objective measure of the nociception/anti-nociception balance. Following institutional approval and written informed consent, 10 healthy adult volunteers were enrolled (29.5 ± 9.1 years, 63.0 ± 8.9 kg and 171.4 ± 7.2). Median nerve electrical stimulation was adjusted according to volunteers' sensitive, motor and painful thresholds (PT). Baseline SEPs were registered, and remifentanil and propofol administered using a stair scheme TCI. For each drug combination a 1.3×PT stimulus was administered, and volunteers evaluated pain intensity in a numerical rating scale (0-10). SEPs' amplitudes and latencies were normalized by the baseline values, reducing volunteers' intervariability. Stimulation currents varied between 6-52 mA (1.3×PT) and pain ratings between 0 and 9. Cortical SEPs latencies were decreased for higher stimulus intensities (P < 0.01), accompanied by increased pain ratings (P < 0.01). An individually adjusted/normalized ratio based on cortical SEPs amplitude and interpeak latency is proposed([Formula: see text]): [Formula: see text] and NSR were significantly correlated in three out of nine subjects, and [Formula: see text] and remifentanil Ce were significantly correlated in two (low number of evaluation points). [Formula: see text] was shown to decrease with increasing doses of propofol and remifentanil (P < 0.05). The proposed metric was depressed by anaesthetics and reflected pain evaluations. Further research is necessary to increase the number of volunteers and drugs' combination, to assess its applicability during surgically adequate anesthetic leves.
Bouwes, Aline; Binnekade, Jan M; Verbaan, Bart W; Zandbergen, Eveline G J; Koelman, Johannes H T M; Weinstein, Henry C; Hijdra, Albert; Horn, Janneke
Bilateral absence of cortical N20 responses of median nerve somatosensory evoked potentials (SEP) predicts poor neurological outcome in postanoxic coma after cardiopulmonary resuscitation (CPR). Although SEP is easy to perform and available in most hospitals, it is worthwhile to know how neurological signs are associated with SEP results. The aim of this study was to investigate whether specific clinical neurological signs are associated with either an absent or a present median nerve SEP in patients after CPR. Data from the previously published multicenter prospective cohort study PROPAC (prognosis in postanoxic coma, 2000-2003) were used. Neurological examination, consisting of Glasgow Coma Score (GCS) and brain stem reflexes, and SEP were performed 24, 48, and 72 h after CPR. Positive predictive values for predicting absent and present SEP, as well as diagnostic accuracy were calculated. Data of 407 patients were included. Of the 781 SEPs performed, N20 s were present in 401, bilaterally absent in 299, and 81 SEPs were technically undeterminable. The highest positive predictive values (0.63-0.91) for an absent SEP were found for absent pupillary light responses. The highest positive predictive values (0.71-0.83) for a present SEP were found for motor scores of withdrawal to painful stimuli or better. Multivariate analyses showed a fair diagnostic accuracy (0.78) for neurological examination in predicting an absent or present SEP at 48 or 72 h after CPR. This study shows that neurological examination cannot reliably predict absent or present cortical N20 responses in median nerve SEPs in patients after CPR.
Beveridge, R; Wilson, S; Coyle, D
A brain-computer interface (BCI) offers movement-free control of a computer application and is achieved by reading and translating the cortical activity of the brain into semantic control signals. Motion-onset visual evoked potentials (mVEP) are neural potentials employed in BCIs and occur when motion-related stimuli are attended visually. mVEP dynamics are correlated with the position and timing of the moving stimuli. To investigate the feasibility of utilizing the mVEP paradigm with video games of various graphical complexities including those of commercial quality, we conducted three studies over four separate sessions comparing the performance of classifying five mVEP responses with variations in graphical complexity and style, in-game distractions, and display parameters surrounding mVEP stimuli. To investigate the feasibility of utilizing contemporary presentation modalities in neurogaming, one of the studies compared mVEP classification performance when stimuli were presented using the oculus rift virtual reality headset. Results from 31 independent subjects were analyzed offline. The results show classification performances ranging up to 90% with variations in conditions in graphical complexity having limited effect on mVEP performance; thus, demonstrating the feasibility of using the mVEP paradigm within BCI-based neurogaming.
Luft, Caroline Di Bernardi; Bhattacharya, Joydeep
Recent studies showed that the visceral information is constantly processed by the brain, thereby potentially influencing cognition. One index of such process is the heartbeat evoked potential (HEP), an ERP component related to the cortical processing of the heartbeat. The HEP is sensitive to a number of factors such as motivation, attention, pain, which are associated with higher levels of arousal. However, the role of arousal and its associated brain oscillations on the HEP has not been characterized, yet it could underlie the previous findings. Here we analysed the effects of high- (HA) and low-arousal (LA) induction on the HEP. Further, we investigated the brain oscillations and their role in the HEP in response to HA and LA inductions. As compared to LA, HA was associated with a higher HEP and lower alpha oscillations. Interestingly, individual differences in the HEP modulation by arousal induction were correlated with alpha oscillations. In particular, participants with higher alpha power during the arousal inductions showed a larger HEP in response to HA compared to LA. In summary, we demonstrated that arousal induction affects the cortical processing of heartbeats; and that the alpha oscillations may modulate this effect. PMID:26503014
Popescu, M; Papadimitriou, S; Karamitsos, D; Bezerianos, A
This paper describes a wavelet-transform-based system for the V wave identification in brainstem auditory evoked potentials (BAEP). The system combines signal denoising and rule-based localization modules. The signal denoising module has the potential of effective noise reduction after signal averaging. It analyses adaptively the evolution of the wavelet transform maxima across scales. The singularities of the signal create wavelet maxima with different properties from those of the induced noise. A non-linear filtering process implemented with a neural network extracts out the noise-induced maxima. The filtered wavelet details are subsequently analysed by the rule-based localization module for the automatic identification of the V wave. In the first phase, it implements a set of statistical observations as well as heuristic criteria used by human experts in order to classify the IV-V complex. At the second phase, using a multiscale focusing algorithm, the IV and V waves are positioned on the BAEP signal. Our experiments revealed that the system provides accurate results even for signals exhibiting unclear IV-V complexes.
Kortelainen, Jukka; Vipin, Ashwati; Thow Xin Yuan; Mir, Hasan; Thakor, Nitish; Al-Nashash, Hasan; All, Angelo
Somatosensory evoked potentials (SEPs) are widely used in the clinic as well as research to study the functional integrity of the different parts of sensory pathways. However, most general anesthetics, such as isoflurane, are known to suppress SEPs, which might affect the interpretation of the signals. In animal studies, the usage of anesthetics during SEP measurements is inevitable due to which detailed effect of these drugs on the recordings should be known. In this paper, the effect of isoflurane on SEPs was studied in a rat model. Both time and frequency properties of the cortical recordings generated by stimulating the tibial nerve of rat's hindlimb were investigated at three different isoflurane levels. While the anesthetic agent is shown to generally suppress the amplitude of the SEP, the effect was found to be nonlinear influencing more substantially the latter part of waveform. This finding will potentially help us in future work aiming at separating the effects of anesthetics on SEP from those due to injury in the ascending neural pathways.
Gaines, G Christopher; Jones, Timothy A
The nonsteroidal antiinflammatory drug (NSAID) ketorolac is a candidate for use as a supplemental analgesic during major surgery in anesthetized rodents. The use of ketorolac during surgery is believed to reduce the anesthetic dose required to achieve and maintain an adequate surgical plane, thus improving the physiologic condition and survival of animals during long experimental procedures. Ketorolac has reported side effects that include dizziness, ear pain, hearing loss, tinnitus, and vertigo in humans, but ketorolac has not been reported to affect the vestibular system in animals. To investigate this possibility, we evaluated the acute effects of ketorolac on vestibular compound action potentials in C57BL/6 mice. Linear vestibular sensory-evoked potentials (VsEP) were recorded during the administration of ketorolac at doses 3 to 14 times the effective analgesic dose. VsEP results for ketorolac were compared with those from a control group maintained under anesthesia for the same period. Ketorolac did not significantly affect the temporal profiles of response latencies and amplitudes or the rate of change in response measures over time between controls and ketorolac-treated mice. These findings demonstrate that ketorolac can be used as an analgesic to supplement anesthesia in mice without concerns of modifying the amplitudes and latencies of the linear VsEP. PMID:23562034
Jutzeler, Catherine R.; Rosner, Jan; Rinert, Janosch; Kramer, John L. K.; Curt, Armin
Contact heat evoked potentials (CHEPs) represent a neurophysiological approach to assess conduction in the spinothalamic tract. The aim of this study was to establish normative values of CHEPs acquired from cervical dermatomes (C4, C6, C8) and examine the potential confounds of age, sex, and height. 101 (49 male) healthy subjects of three different age groups (18–40, 41–60, and 61–80 years) were recruited. Normal (NB, 35–52 °C) followed by increased (IB, 42–52 °C) baseline stimulation protocols were employed to record CHEPs. Multi-variate linear models were used to investigate the effect of age, sex, and height on the CHEPs parameters (i.e., N2 latency, N2P2 amplitude, rating of perceived intensity). Compared to NB, IB stimulation reduced latency jitter within subjects, yielding larger N2P2 amplitudes, and decreased inter-subject N2 latency variability. Age was associated with reduced N2P2 amplitude and prolonged N2 latency. After controlling for height, male subjects had significantly longer N2 latencies than females during IB stimulation. The study provides normative CHEPs data in a large cohort of healthy subjects from segmentally examined cervical dermatomes. Age and sex were identified as important factors contributing to N2 latency and N2P2 amplitude. The normative data will improve the diagnosis of spinal cord pathologies. PMID:27708413
Van Dun, Bram; Kania, Anna; Dillon, Harvey
Cortical auditory evoked potentials (CAEPs) are influenced by the characteristics of the stimulus, including level and hearing aid gain. Previous studies have measured CAEPs aided and unaided in individuals with normal hearing. There is a significant difference between providing amplification to a person with normal hearing and a person with hearing loss. This study investigated this difference and the effects of stimulus signal-to-noise ratio (SNR) and audibility on the CAEP amplitude in a population with hearing loss. Twelve normal-hearing participants and 12 participants with a hearing loss participated in this study. Three speech sounds—/m/, /g/, and /t/—were presented in the free field. Unaided stimuli were presented at 55, 65, and 75 dB sound pressure level (SPL) and aided stimuli at 55 dB SPL with three different gains in steps of 10 dB. CAEPs were recorded and their amplitudes analyzed. Stimulus SNRs and audibility were determined. No significant effect of stimulus level or hearing aid gain was found in normal hearers. Conversely, a significant effect was found in hearing-impaired individuals. Audibility of the signal, which in some cases is determined by the signal level relative to threshold and in other cases by the SNR, is the dominant factor explaining changes in CAEP amplitude. CAEPs can potentially be used to assess the effects of hearing aid gain in hearing-impaired users. PMID:27587919
Cloud, Beth A.; Ball, Bret G.; Chen, Bingkun; Knight, Andrew M.; Hakim, Jeffrey S.; Ortiz, Ana M.; Windebank, Anthony J.
Techniques used to produce partial spinal cord injuries in animal models have the potential for creating variability in lesions. The amount of tissue affected may influence the functional outcomes assessed in the animals. The recording of somatosensory evoked potentials (SSEPs) may be a valuable tool for assessing the extent of lesion applied in animal models of traumatic spinal cord injury (SCI). Intraoperative tibial SSEP recordings were assessed during surgically induced lateral thoracic hemisection SCI in Sprague-Dawley rats. The transmission of SSEPs, or lack thereof, was determined and compared against the integrity of the dosal funiculi on each side of the spinal cord upon histological sectioning. An association was found between the presence of an SSEP signal and presence of intact dorsal funiculus tissue. The relative risk is 4.50 (95% confidence interval: 1.83 to 11.08) for having an intact dorsal funiculus when the ipsilateral SSEP was present compared to when it was absent. Additionally, the amount of spared spinal cord tissue correlates with final functional assessments at nine weeks post injury: BBB (linear regression, R2 = 0.618, p <0.001) and treadmill test (linear regression, R2 = 0.369, p = 0.016). Therefore, we propose intraoperative SSEP monitoring as a valuable tool to assess extent of lesion and reduce variability between animals in experimental studies of SCI. PMID:22960163
Bosse, Sebastian; Acqualagna, Laura; Porbadnigk, Anne K.; Curio, Gabriel; Müller, Klaus-Robert; Blankertz, Benjamin; Wiegand, Thomas
An approach to the neural measurement of perceived image quality using electroencephalography (EEG) is presented. 6 different images were tested on 6 different distortion levels. The distortions were introduced by a hybrid video encoder. The presented study consists of two parts: In a first part, subjects were asked to evaluate the quality of the test stimuli behaviorally during a conventional psychophysical test using a degradation category rating procedure. In a second part, subjects were presented undistorted and distorted texture images in a periodically alternating fashion at a fixed frequency. This alternating presentation elicits so called steady-state visual evoked potentials (SSVEP) as a brain response that can be measured on the scalp. The amplitude of modulations in the brain signals is significantly and strongly negatively correlated with the magnitude of visual impairment reported by the subjects. This neurophysiological approach to image quality assessment may potentially lead to a more objective evaluation, as behavioral approaches suffer from drawbacks such as biases, inter-subject variances and limitations to test duration.
Sinha, Sujeet Kumar; Bohra, Vaishnavi; Sanju, Himanshu Kumar
The objective of the study was to assess the sacculocollic and otolith ocular pathway function using cervical vestibular evoked myogenic potentials (cVEMP) and ocular vestibular myogenic potentials (oVEMP) in dancers and non dancers. Total 16 subjects participated in the study. Out of 16 participants, 8 were trained in Indian classical form of dance (dancers) and other 8 participants who were not trained in any dance form (non dancers). cVEMP and oVEMP responses were recorded for all the subjects. Non Parametric Mann-Whitney U test revealed no significant difference between dancers and non dancers for the latency and amplitude parameter for cVEMP and oVEMP, i.e. P13, N23 latency and P13-N23 complex amplitude and N10, P14 latency, N10-P14 complex amplitude respectively. The vestibular system comprises of several structures. It is possible that the dance style practiced by the dancer’s group assessed in this study does not contribute towards improving the plasticity of the sacculocollic and otolith-ocular pathways. It can be concluded that not all forms of dance training brings about a change in the plasticity of the sacculocollic and otolithocular pathways. PMID:26557344
Crognale, Michael A.; Duncan, Chad S.; Shoenhard, Hannah; Peterson, Dwight J.; Berryhill, Marian E.
Color losses of central origin (cerebral achromatopsia and dyschromatopsia) can result from cortical damage and are most commonly associated with stroke. Such cases have the potential to provide useful information regarding the loci of the generation of the percept of color. One available tool to examine this issue is the chromatic visual evoked potential (cVEP). The cVEP has been used successfully to objectively quantify losses in color vision capacity in both congenital and acquired deficiencies of retinal origin but has not yet been applied to cases of color losses of cortical origin. In addition, it is not known with certainty which cortical sites are responsible for the generation of the cVEP waveform components. Here we report psychophysical and electrophysiological examination of a patient with color deficits resulting from a bilateral cerebral infarct in the ventral occipitotemporal region. Although this patient demonstrated pronounced color losses of a general nature, the waveform of the cVEP remains unaffected. Contrast response functions of the cVEP are also normal for this patient. The results suggest that the percept of color arises after the origin of the cVEP and that normal activity in those areas that give rise to the characteristic negative wave of the cVEP are not sufficient to provide for the normal sensation of color. PMID:23986535
Singh, Nilkamal; Telles, Shirley
Evoked potentials (EPs) are a relatively noninvasive method to assess the integrity of sensory pathways. As the neural generators for most of the components are relatively well worked out, EPs have been used to understand the changes occurring during meditation. Event-related potentials (ERPs) yield useful information about the response to tasks, usually assessing attention. A brief review of the literature yielded eleven studies on EPs and seventeen on ERPs from 1978 to 2014. The EP studies covered short, mid, and long latency EPs, using both auditory and visual modalities. ERP studies reported the effects of meditation on tasks such as the auditory oddball paradigm, the attentional blink task, mismatched negativity, and affective picture viewing among others. Both EP and ERPs were recorded in several meditations detailed in the review. Maximum changes occurred in mid latency (auditory) EPs suggesting that maximum changes occur in the corresponding neural generators in the thalamus, thalamic radiations, and primary auditory cortical areas. ERP studies showed meditation can increase attention and enhance efficiency of brain resource allocation with greater emotional control. PMID:26137479
Bulut, Mehmet; Dönmez, Barış Özgür; Öztürk, Nihal; Başaranlar, Göksun; Kencebay Manas, Ceren; Derin, Narin; Özdemir, Semir
AIM To evaluate the effect of sodium tungstate on visual evoked potentials (VEPs) in diabetic rats. METHODS Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin (50 mg/kg). Sodium tungstate [40 mg/(kg·d)] was administered for 12wk and then VEPs were recorded. Additionally, thiobarbituric acid reactive substance (TBARS) levels were measured in brain tissues. RESULTS The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group. CONCLUSION Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use. PMID:27275420
Cloud, Beth A; Ball, Bret G; Chen, Bingkun K; Knight, Andrew M; Hakim, Jeffrey S; Ortiz, Ana M; Windebank, Anthony J
Techniques used to produce partial spinal cord injuries in animal models have the potential for creating variability in lesions. The amount of tissue affected may influence the functional outcomes assessed in the animals. The recording of somatosensory evoked potentials (SSEPs) may be a valuable tool for assessing the extent of lesion applied in animal models of traumatic spinal cord injury (SCI). Intraoperative tibial SSEP recordings were assessed during surgically induced lateral thoracic hemisection SCI in Sprague-Dawley rats. The transmission of SSEPs, or lack thereof, was determined and compared against the integrity of the dorsal funiculi on each side of the spinal cord upon histological sectioning. An association was found between the presence of an SSEP signal and presence of intact dorsal funiculus tissue. The relative risk is 4.50 (95% confidence interval: 1.83-11.08) for having an intact dorsal funiculus when the ipsilateral SSEP was present compared to when it was absent. Additionally, the amount of spared spinal cord tissue correlates with final functional assessments at nine weeks post injury: BBB (linear regression, R²=0.618, p<0.001) and treadmill test (linear regression, R²=0.369, p=0.016). Therefore, we propose intraoperative SSEP monitoring as a valuable tool to assess extent of lesion and reduce variability between animals in experimental studies of SCI.
Gaines, G Christopher; Jones, Timothy A
The nonsteroidal antiinflammatory drug (NSAID) ketorolac is a candidate for use as a supplemental analgesic during major surgery in anesthetized rodents. The use of ketorolac during surgery is believed to reduce the anesthetic dose required to achieve and maintain an adequate surgical plane, thus improving the physiologic condition and survival of animals during long experimental procedures. Ketorolac has reported side effects that include dizziness, ear pain, hearing loss, tinnitus, and vertigo in humans, but ketorolac has not been reported to affect the vestibular system in animals. To investigate this possibility, we evaluated the acute effects of ketorolac on vestibular compound action potentials in C57BL/6 mice. Linear vestibular sensory-evoked potentials (VsEP) were recorded during the administration of ketorolac at doses 3 to 14 times the effective analgesic dose. VsEP results for ketorolac were compared with those from a control group maintained under anesthesia for the same period. Ketorolac did not significantly affect the temporal profiles of response latencies and amplitudes or the rate of change in response measures over time between controls and ketorolac-treated mice. These findings demonstrate that ketorolac can be used as an analgesic to supplement anesthesia in mice without concerns of modifying the amplitudes and latencies of the linear VsEP.
Nourski, Kirill V; Abbas, Paul J; Miller, Charles A; Robinson, Barbara K; Jeng, Fuh-Cherng
This study investigated the effects of acoustic noise on the auditory nerve compound action potentials in response to electric pulse trains. Subjects were adult guinea pigs, implanted with a minimally invasive electrode to preserve acoustic sensitivity. Electrically evoked compound action potentials (ECAP) were recorded from the auditory nerve trunk in response to electric pulse trains both during and after the presentation of acoustic white noise. Simultaneously presented acoustic noise produced a decrease in ECAP amplitude. The effect of the acoustic masker on the electric probe was greatest at the onset of the acoustic stimulus and it was followed by a partial recovery of the ECAP amplitude. Following cessation of the acoustic noise, ECAP amplitude recovered over a period of approximately 100-200 ms. The effects of the acoustic noise were more prominent at lower electric pulse rates (interpulse intervals of 3 ms and higher). At higher pulse rates, the ECAP adaptation to the electric pulse train alone was larger and the acoustic noise, when presented, produced little additional effect. The observed effects of noise on ECAP were the greatest at high electric stimulus levels and, for a particular electric stimulus level, at high acoustic noise levels.
Stufflebeam, S M; Levine, R A; Gardner, J C; Fullerton, B C; Furst, M; Rosen, B R
To develop an objective method for detecting multiple sclerosis (MS) brainstem lesions, magnetic resonance (MR) images (multiple planar, spin-echo, acquired in three planes of section) of sixteen MS patients and fourteen normal subjects were analyzed with an algorithm that detected regions with a relatively increased intensity on both a spin-echo image and a T2 image. To be considered a lesion, such regions had to overlap in at least two orthogonal planes. Using a digitized atlas of the human brainstem, the lesion locations were mapped with respect to the brainstem anatomy. This method was evaluated by comparing the location of MS lesions with the brainstem auditory evoked potentials obtained from these subjects. Brainstem lesions were detected in five MS patients; four had lesions impinging upon the auditory system and one did not. All four had abnormal evoked potentials. The fourteen normal subjects, the one MS patient with brainstem lesions outside the auditory pathway, and the eleven other MS patients with no brainstem lesions all had normal evoked potentials. The requirement that lesions be detected in at least two planes of section greatly improved the specificity of the algorithm. The consistency between the MR and brainstem auditory evoked potentials results supports the validity of this imaging analysis algorithm for objectively localizing brainstem lesions.
Alamusi; Matsuo, Toshihiko; Hosoya, Osamu; Uchida, Tetsuya
Photoelectric dye-coupled polyethylene film, designated Okayama University type-retinal prosthesis or OUReP™, generates light-evoked surface electric potentials and stimulates neurons. The dye-coupled films or plain films were implanted subretinally in both eyes of 10 Royal College of Surgeons rats with hereditary retinal dystrophy at the age of 6 weeks. Visual evoked potentials in response to monocular flashing light stimuli were recorded from cranially-fixed electrodes, 4 weeks and 8 weeks after the implantation. After the recording, subretinal film implantation was confirmed histologically in 7 eyes with dye-coupled films and 7 eyes with plain films. The recordings from these 7 eyes in each group were used for statistical analysis. The amplitudes of visual evoked potentials in the consecutive time points from 125 to 250 ms after flash were significantly larger in the 7 eyes with dye-coupled film implantation, compared to the 7 eyes with plain film implantation at 8 weeks after the implantation (P < 0.05, repeated-measure ANOVA). The photoelectric dye-coupled polyethylene film, as retinal prosthesis, gave rise to visual evoked potential in response to flashing light.
Raja, Vignesh; Kumar, Anupma; Durnian, Jon; Hagan, Richard; Buxton, Neil; Newman, William
We report a case of an occipital arachnoid cyst in an infant, managed on the basis of changes in visually evoked potentials (VEPs). A significant asymmetry of VEP responses prompted neurosurgical intervention, which improved visual behavior and electrical response to both pattern and flash stimuli.
Ohlrich, Elizabeth S.; And Others
This study examined individual patterns of the maturation of auditory evoked potential (AEP) in normal infants to determine whether longitudinal data show less variability than cross-sectional data, and to further assess the effect of stage of sleep on AEP. The AEPs for 10 children were examined by repeated testing between the ages of about two…
Frøbert, O; Arendt-Nielsen, L; Bak, P; Funch-Jensen, P; Bagger, J P
Sensory thresholds and brain evoked potentials were determined in 12 healthy volunteers using electrical stimulation of the oesophagus 28 and 38 cm from the nares. The peaks of the evoked potentials were designated N for negative deflections and P for positive. Continuous electrical stimulation (40 Hz) at the 38 cm position resembled heartburn (five of 12 subjects) while non-specific ('electrical') sensations were provoked at 28 cm (10 of 12). Thresholds of sensation and of pain were lower at the initial than the second determination, but did not differ with respect to stimulation site. The pain summation threshold to repeated stimuli (2 Hz, 5 stimuli) was determined for the first time in a viscus. This threshold was lower than the pain threshold to single stimuli at 38 cm (p < 0.02). Evoked potential latencies did not change significantly over a six month period while the N1/P2 amplitude was higher at the first measurement (p < 0.05). P1 and N1 latencies were significantly shorter 38 cm (medians 100 and 141 ms) than 28 cm from the nares (102 and 148 ms) (p = 0.04 and p = 0.008). Electrical stimulation of the oesophagus may serve as a human experimental model for visceral pain. Longer evoked potential latencies from the proximal compared with distal stimulations provide new information about the sensory pathways of the oesophagus. PMID:8549932
Fujita, Takako; Kamio, Yoko; Yamasaki, Takao; Yasumoto, Sawa; Hirose, Shinichi; Tobimatsu, Shozo
Individuals with autism spectrum disorders (ASDs) have different automatic responses to faces than typically developing (TD) individuals. We recorded visual evoked potentials (VEPs) in 10 individuals with high-functioning ASD (HFASD) and 10 TD individuals. Visual stimuli consisted of upright and inverted faces (fearful and neutral) and objects…
Fukuda, Miho; Nishida, Masaaki; Juhasz, Csaba; Muzik, Otto; Sood, Sandeep; Chugani, Harry T.; Asano, Eishi
Recent studies have suggested that cortical gamma-oscillations are tightly linked with various forms of physiological activity. In the present study, the dynamic changes of intracranially recorded median-nerve somatosensory-evoked potentials (SEPs) and somatosensory-induced gamma-oscillations were animated on a three-dimensional MR image, and the…
Carbaryl is a widely used N-methyl carbamate pesticide that acts by inhibiting cholinesterases (ChE), which may lead to cholinergic toxicity. Flash evoked potentials (FEPs) are a neurophysiological response often used to detect central nervous system (CNS) changes following expos...
Shucard, Janet L.; Shucard, David W.
Verbal and musical stimuli were presented to infants in a study of the relations of evoked potential left-right amplitude asymmetries to gender and hand preference. There was a relation between asymmetry and hand preference, and for girls, between asymmetry and stimulus condition. Results suggest a gender difference in cerebral hemisphere…
Houser, Dorian S; Crocker, Daniel E; Finneran, James J
Auditory evoked potential (AEP) hearing studies in marine mammals should consider an expected size-dependent reduction in AEP amplitude. This study is the first to measure the click-evoked response in a large marine mammal, the adult male elephant seal (Mirounga angustirostris). Click stimuli were presented at peak-peak equivalent sound pressure levels of 117-118 dB re: 20 microPa. Three positive peaks (P1-P3) and two negative peaks (N4 and N5) were observed in the AEP. Response latencies were longer than previously observed in a 1.8 yr old seal and the maximum peak-peak amplitude was comparatively reduced by more than 60%. The inverse relationship between size and AEP amplitude will likely require increased averaging with larger subjects and possibly modifications to electrode placement and design in order to increase the quality of recorded evoked responses.
Valeriani, M; de Tommaso, M; Restuccia, D; Le Pera, D; Guido, M; Iannetti, G D; Libro, G; Truini, A; Di Trapani, G; Puca, F; Tonali, P; Cruccu, G
The habituation to sensory stimuli of different modalities is reduced in migraine patients. However, the habituation to pain has never been evaluated. Our aim was to assess the nociceptive pathway function and the habituation to experimental pain in patients with migraine. Scalp potentials were evoked by CO(2) laser stimulation (laser evoked potentials, LEPs) of the hand and facial skin in 24 patients with migraine without aura (MO), 19 patients with chronic tension-type headache (CTTH), and 28 control subjects (CS). The habituation was studied by measuring the changes of LEP amplitudes across three consecutive repetitions of 30 trials each (the repetitions lasted 5 min and were separated by 5-min intervals). The slope of the regression line between LEP amplitude and number of repetitions was taken as an index of habituation. The LEPs consisted of middle-latency, low-amplitude responses (N1, contralateral temporal region, and P1, frontal region) followed by a late, high-amplitude, negative-positive complex (N2/P2, vertex). The latency and amplitude of these responses were similar in both patients and controls. While CS and CTTH patients showed a significant habituation of the N2/P2 response, in MO patients this LEP component did not develop any habituation at all after face stimulation and showed a significantly lower habituation than in CS after hand stimulation. The habituation index of the vertex N2/P2 complex exceeded the normal limits in 13 out of the 24 MO patients and in none of the 19 CTTH patients (P<0.0001; Fisher's exact test). Moreover, while the N1-P1 amplitude showed a significant habituation in CS after hand stimulation, it did not change across repetitions in MO patients. In conclusion, no functional impairment of the nociceptive pathways, including the trigeminal pathways, was found in either MO or CTTH patients. But patients with migraine had a reduced habituation, which probably reflects an abnormal excitability of the cortical areas involved in
Jackson, V M; Trout, S J; Brain, K L; Cunnane, T C
1. Action potential-evoked Ca(2+) transients in postganglionic sympathetic axon bundles in mouse vas deferens have been characterized using confocal microscopy and Ca(2+) imaging. 2. Axonal Ca(2+) transients were tetrodotoxin sensitive. The amplitude depended on both the frequency of stimulation and the number of stimuli in a train. 3. Removal of extracellular Ca(2+) abolished the Ca(2+) transient. Cd(2+)(100 microM) inhibited the Ca(2+) transient by 78 +/- 10 %. The N-type Ca(2+) channel blocker omega-conotoxin GVIA (0.1 microM) reduced the amplitude by -35 +/-4 %, whereas nifedipine (10 microM; L-type) and omega-conotoxin MVIIC (0.1 microM; P/Q type) were ineffective. 4. Caffeine (10 mM), ryanodine (10 microM), cyclopiazonic acid (30 microM) or CCCP (10 microM) had no detectable effects. 5. Blockade of large and small conductance Ca(2+)-dependent K+ channels with iberiotoxin (0.1 microM) and apamin (1 microM), respectively, or Ca(2+)-dependent Cl(-) channels by niflumic acid (100 microM) did not alter Ca(2+) transients. 6. In contrast, the non-specific K+ channel blockers tetraethylammonium (10 mM) and 4-aminopyridine (10 mM) markedly increased the amplitude of the Ca(2+) transient. Blockade of delayed rectifiers and A-like K+ channels, by tityustoxin-K (alpha) (0.1 microM) and pandinustoxin-K (alpha) (10 nM), respectively, also increased the Ca(2+) transient amplitude. 7. Thus, Ca(2+) transients are evoked by Na(+)-dependent action potentials in axons. These transients originate mainly from Ca(2+) entry through voltage-dependent Ca(2+) channels (80 % Cd(2+) sensitive of which 40 % was attributable to N-type). Twenty per cent of the Ca(2+) transient was not due to Ca(2+) entry through voltage-gated Ca(2+) channels. Intracellular stores and mitochondria were not involved in the generation of the transient. Ca(2+) transients are modulated by A-like K+ channels and delayed rectifiers (possibly K(V)1.2) but not by Ca(2+)-activated ion channels.
Gustafsson, B; McCrea, D
Shapes of post-synaptic potentials (p.s.p.s) in cat motoneurones were compared with the time course of correlated changes in firing probability during repetitive firing. Excitatory and inhibitory post-synaptic potentials (e.p.s.p.s. and i.p.s.p.s) were evoked by brief triangular stretches of the triceps surae-plantaris muscles. Depolarizing current was injected through the recording micro-electrode to evoke repetitive firing and the post-stimulus time histogram of motoneurone spikes was obtained. E.p.s.p.s (n = 80) of different sizes (30-1040 microV) and rise times (1.1-8.2 ms) were investigated in fifty-nine motoneurones. The majority of the e.p.s.p.s were recorded in triceps surae-plantaris motoneurones with high levels of synaptic noise (estimated peak-to-peak fluctuations of 1.5-3.5 mV). This noise was generated by keeping the triceps surae-plantaris muscles stretched to a near maximal degree. The remaining e.p.s.p.s were recorded in motoneurones to other hind-limb muscles with a low level of synaptic noise. The height of the primary peak of the correlogram with respect to base-line firing rate increased in proportion to both amplitude and rising slope of the e.p.s.p.s. Using normalization procedures or using e.p.s.p.s of constant amplitude but different slopes and vice versa, the relative peak height increased with e.p.s.p. peak derivative with a slope of around 6/mV per millisecond and with e.p.s.p peak amplitude with a slope of about 1/mV. The shape of the correlogram (peak and trough) seemed well described by a linear combination of the shape of the e.p.s.p. derivative and that of the e.p.s.p. itself. The relative e.p.s.p. contribution (e.p.s.p.:e.p.s.p. derivative ratio) varied with e.p.s.p. amplitude and noise level, being largest (mostly 0.25-1.0) for small e.p.s.p.s (100-300 microV) in high levels of synaptic noise and smaller (0-0.25) for larger e.p.s.p.s and for e.p.s.p.s in a low noise background. In conformity with the above finding, a leaky
Didoné, Dayane Domeneghini; Oppitz, Sheila Jacques; Folgearini, Jordana; Biaggio, Eliara Pinto Vieira; Garcia, Michele Vargas
Introduction Long Latency Auditory Evoked Potentials (LLAEP) with speech sounds has been the subject of research, as these stimuli would be ideal to check individualś detection and discrimination. Objective The objective of this study is to compare and describe the values of latency and amplitude of cortical potentials for speech stimuli in adults with normal hearing. Methods The sample population included 30 normal hearing individuals aged between 18 and 32 years old with ontological disease and auditory processing. All participants underwent LLAEP search using pairs of speech stimuli (/ba/ x /ga/, /ba/ x /da/, and /ba/ x /di/. The authors studied the LLAEP using binaural stimuli at an intensity of 75dBNPS. In total, they used 300 stimuli were used (∼60 rare and 240 frequent) to obtain the LLAEP. Individuals received guidance to count the rare stimuli. The authors analyzed latencies of potential P1, N1, P2, N2, and P300, as well as the ampleness of P300. Results The mean age of the group was approximately 23 years. The averages of cortical potentials vary according to different speech stimuli. The N2 latency was greater for /ba/ x /di/ and P300 latency was greater for /ba/ x /ga/. Considering the overall average amplitude, it ranged from 5.35 and 7.35uV for different speech stimuli. Conclusion It was possible to obtain the values of latency and amplitude for different speech stimuli. Furthermore, the N2 component showed higher latency with the / ba / x / di / stimulus and P300 for /ba/ x / ga /. PMID:27096012
Neurophysiological navigation in the trigeminal nerve: use of masticatory responses and facial motor responses evoked by electrical stimulationof the trigeminal rootlets for RF-thermorhizotomy guidance.
Sindou, M P
RF-thermorhizotomy of the trigeminal nerve is an effective and safe treatment of trigeminal neuralgia, provided lesioning of the sensory fibers is performed precisely. To control the accurate placement of the electrode tip, electrical stimulation testing, prior to thermal lesioning, is of prime importance. The clinical observation of direct masticatory responses (DMR) and facial evoked motor responses (EMR) produced by stimulation of the trigeminal rootlets (at 5 Hz) helps to place the electrode tip in the optimal location. The best location is the one where the threshold for eliciting DMR is high and the threshold for evoking facial EMR in the area corresponding to the trigger zone is low. EMR in orbicularis oculi indicates location in V1, levator labii EMR signifies V2 and orbicular oris EMR corresponds to V3.
Dong, Xuebao; Suo, Puxia; Yuan, Xin; Yao, Xuefeng
Auditory evoked potentials (AEPs) have been used as a measure of the depth of anesthesia during the intra-operative process. AEPs are classically divided, on the basis of their latency, into first, fast, middle, slow, and late components. The use of auditory evoked potential has been advocated for the assessment of Intra-operative awareness (IOA), but has not been considered seriously enough to universalize it. It is because we have not explored enough the impact of auditory perception and auditory processing on the IOA phenomena as well as on the subsequent psychological impact of IOA on the patient. More importantly, we have seldom tried to look at the phenomena of IOP from the perspective of consciousness itself. This perspective is especially important because many of IOA phenomena exist in the subconscious domain than they do in the conscious domain of explicit recall. Two important forms of these subconscious manifestations of IOA are the implicit recall phenomena and post-operative dreams related to the operation. Here, we present an integrated auditory consciousness-based model of IOA. We start with a brief description of auditory awareness and the factors affecting it. Further, we proceed to the evaluation of conscious and subconscious information processing by auditory modality and how they interact during and after intra-operative period. Further, we show that both conscious and subconscious auditory processing affect the IOA experience and both have serious psychological implications on the patient subsequently. These effects could be prevented by using auditory evoked potential during monitoring of anesthesia, especially the mid-latency auditory evoked potentials (MLAERs). To conclude our model with present hypothesis, we propose that the use of auditory evoked potential should be universal with general anesthesia use in order to prevent the occurrences of distressing outcomes resulting from both conscious and subconscious auditory processing during
Drexl, Markus; Faulstich, Michael; Von Stebut, Boris; Radtke-Schuller, Susanne; Kössl, Manfred
The hedgehog tenrec, Echinops telfairi, has certain basal mammalian features, like a cloaca and a sparsely differentiated brain with smooth cerebral hemispheres. The peripheral auditory capabilities of this species were investigated by means of distortion product otoacoustic emissions (DPOAE). For comparison, we determined auditory evoked potentials (AEP) in the inferior colliculus and the auditory cortex. Both methods show that the auditory range of E. telfairi extends well into ultrasonic frequencies, with a region of highest sensitivity at around 16 kHz. The total auditory range spans about 4 octaves at 40 dB SPL. The low-frequency limit of auditory processing is found at frequencies of about 2-3 kHz. The DPOAE and the AEP thresholds of E. telfairi do not run fully parallel in the high-frequency range. For a threshold value of 40 dB SPL, cochlear mechanical thresholds as measured with DPOAE extend up to 50 kHz, whereas neuronal thresholds reach the high-frequency limit at about 30 kHz. Frequency tuning, as assessed from DPOAE suppression tuning curves, was low to moderate with Q(10 dB) values ranging from 1.7 to 8. The lack of discontinuity in the group delay (derived from DPOAE measurements) reveals that cochlear frequency representation is tonotopic without any region of specialized mechanical tuning.
Kuroda, Ken; Fujiwara, Akinori; Takeda, Yasuhiro; Kamei, Chiaki
The side effects of narcotics, including morphine, on the visual system are still unclear; therefore, the present study was undertaken to examine the effects of narcotics on the visual system at each antinociceptive dose by using the evoked potential (VEP) in rats. Morphine (2 or 5 mg/kg) caused a significant increase in the amplitude of early and late VEP components (P(1)-N(1), N(1)-P(2), P(3)-N(3) and N(3)-P(4)). Fentanyl (0.02 mg/kg) also showed a significant increase in the amplitude of late VEP components (P(3)-N(3), N(3)-P(4)). The effects of morphine and fentanyl on VEP components were antagonized by naloxone (1 mg/kg). On the other hand, (+/-)-pentazocine (20 mg/kg) reduced the amplitude of the late VEP component (N(3)-P(4)), and this effect was not antagonized by naloxone. Butorphanol showed no significant changes in early and late VEP components. In conclusion, morphine stimulated the retino-geniculate-cortex pathway and the thalamus-cortical circuit through the opioid receptors, and fentanyl stimulated the thalamus-cortical circuit through the opioid receptors. It can therefore be assumed that VEP is a useful tool for examining the side effects of drugs, including narcotics, on the visual system.
Kwak, No-Sang; Müller, Klaus-Robert
The robust analysis of neural signals is a challenging problem. Here, we contribute a convolutional neural network (CNN) for the robust classification of a steady-state visual evoked potentials (SSVEPs) paradigm. We measure electroencephalogram (EEG)-based SSVEPs for a brain-controlled exoskeleton under ambulatory conditions in which numerous artifacts may deteriorate decoding. The proposed CNN is shown to achieve reliable performance under these challenging conditions. To validate the proposed method, we have acquired an SSVEP dataset under two conditions: 1) a static environment, in a standing position while fixated into a lower-limb exoskeleton and 2) an ambulatory environment, walking along a test course wearing the exoskeleton (here, artifacts are most challenging). The proposed CNN is compared to a standard neural network and other state-of-the-art methods for SSVEP decoding (i.e., a canonical correlation analysis (CCA)-based classifier, a multivariate synchronization index (MSI), a CCA combined with k-nearest neighbors (CCA-KNN) classifier) in an offline analysis. We found highly encouraging SSVEP decoding results for the CNN architecture, surpassing those of other methods with classification rates of 99.28% and 94.03% in the static and ambulatory conditions, respectively. A subsequent analysis inspects the representation found by the CNN at each layer and can thus contribute to a better understanding of the CNN’s robust, accurate decoding abilities. PMID:28225827
All, Angelo H.; Walczak, Piotr; Agrawal, Gracee; Gorelik, Michael; Lee, Christopher; Thakor, Nitish V.; Bulte, Jeff W.M.; Kerr, Douglas A.
Myelin oligodendrocyte glycoprotein (MOG) is commonly used as an immunogen to induce an immune response against endogenous myelin, thereby modeling multiple sclerosis in rodents. When MOG is combined with complete Freund’s adjuvant (CFA), multifocal, multiphasic disease ensues; whereas when MOG is combined with incomplete Freund’s adjuvant (IFA), clinical disease is usually absent. MOG-IFA immunized animals can be induced to have neurological disease after intraspinal injections of cytokines and ethidium bromide (EtBr). In this study, we investigated whether MOG-IFA immunized rats exhibited subclinical injury as defined by Somatosensory Evoked Potential (SEP) recordings. The titration of Anti-MOG-125 antibodies showed robust peripheral mounting of immune response against myelin in MOG-immunized rats. However the SEP measures showed no significant change over time. Upon injecting cytokine-EtBr in the spinal cord after MOG sensitization, the SEP recordings showed reduced amplitude and prolonged latency, suggestive of axonal injury and demyelination in the dorsal column, respectively. These findings were later confirmed using T2-weighted MRI and histological hematoxilin-eosin stain of the spinal cord. This report establishes that MOG-IFA immunization alone does not alter neuronal conduction in SEP-related neural-pathways and that longitudinal in-vivo SSEP recordings provide a sensitive read-out for focal myelitis (MOG-IFA & intraspinal cytokine-EtBr) in rats. PMID:19423134
All, Angelo H.; Walczak, Piotr; Agrawal, Gracee; Gorelik, Michael; Lee, Christopher; Thakor, Nitish V.; Bulte, Jeff W.M.; Kerr, Douglas A.
Myelin oligodendrocyte glycoprotein (MOG) is commonly used as an immunogen to induce an immune response against endogenous myelin, thereby modeling multiple sclerosis in rodents. When MOG is combined with complete Freund's adjuvant (CFA), multifocal, multiphasic disease ensues; whereas when MOG is combined with incomplete Freund's adjuvant (IFA), clinical disease is usually absent. MOG–IFA immunized animals can be induced to have neurological disease after intraspinal injections of cytokines and ethidium bromide (EtBr). In this study, we investigated whether MOG–IFA immunized rats exhibited subclinical injury as defined by somatosensory evoked potential (SEP) recordings. The titration of anti-MOG-125 antibodies showed robust peripheral mounting of immune response against myelin in MOG-immunized rats. However the SEP measures showed no significant change over time. Upon injecting cytokine–EtBr in the spinal cord after MOG sensitization, the SEP recordings showed reduced amplitude and prolonged latency, suggestive of axonal injury and demyelination in the dorsal column, respectively. These findings were later confirmed using T2-weighted MRI and histological hematoxylin–eosin stain of the spinal cord. This report establishes that MOG–IFA immunization alone does not alter neuronal conduction in SEP-related neural-pathways and that longitudinal in-vivo SEP recordings provide a sensitive read-out for focal myelitis (MOG–IFA and intraspinal cytokine–EtBr) in rats. PMID:20508959
Shiga, Y; Yamada, T; Ofuji, A; Fujita, Y; Kawamura, T; Inoue, K; Hada, Y; Yamazaki, H; Cheng, M H; Yeh, M H
We studied the effect of stimulus intensity on latencies of short-latency somatosensory evoked potentials (SSEP) by measuring both onset and peak latencies individually. The latencies of N9, N13, N20 and N9-N13 peripheral conduction time (PCT) of median nerve (MN) SSEP, and N8, N23, P37 and N8-N23 PCT of tibial nerve (TN) and sural nerve (SN) SSEP significantly shortened with increasing stimulus intensity by onset latency measurement. However, those latencies by peak latency measurement were less significantly shortened or had only a trend of latency shortening without statistical significance. In contrast to PCT, N13-N20 central conduction time (CCT) of MN-SSEP and N23-P37 CCT of TN- or SN-SSEP showed no latency changes with the increased stimulus intensity by both onset and peak latencies measurement. As peak latencies had greater interindividual variability than onset latencies shown by larger standard deviation, shortening of onset latencies were more consistent than that of peak latencies. We think shortening of onset latencies indicates the recruitment of faster conduction fiber along with increased stimulus intensity. As the degree of latency shortening was less if stimulus intensity was above 2.5 times sensory threshold, the stimulus intensity greater than 2.5 times the sensory threshold should be used for clinical application.
Popov, Vladimir V; Supin, Alexander Ya; Klishin, Vladimir O; Bulgakova, Tatyana N
Hearing thresholds as a function of sound-source azimuth were measured in bottlenose dolphins using an auditory evoked potential (AEP) technique. AEP recording from a region next to the ear allowed recording monaural responses. Thus, a monaural directivity diagram (a threshold-vs-azimuth function) was obtained. For comparison, binaural AEP components were recorded from the vertex to get standard binaural directivity diagrams. Both monaural and binaural diagrams were obtained at frequencies ranging from 8 to 128 kHz in quarter-octave steps. At all frequencies, the monaural diagram demonstrated asymmetry manifesting itself as: (1) lower thresholds at the ipsilateral azimuth as compared to the symmetrical contralateral azimuth and (2) ipsilateral shift of the lowest-threshold point. The directivity index increased with frequency: at the ipsilateral side it rose from 4.7 to 17.8 dB from 11.2 to 128 kHz, and from 10.5 to 15.6 dB at the contralateral side. The lowest-threshold azimuth shifted from 0 degrees at 90-128 kHz to 22.5 degrees at 8-11.2 kHz. The frequency-dependent variation of the lowest-threshold azimuth indicates the presence of two sound-receiving apertures at each head side: a high-frequency aperture with the axis directed frontally, and a low-frequency aperture with the axis directed laterally.
Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee
Auditory evoked potentials (AEPs) were recorded during echolocation in a false killer whale Pseudorca crassidens. An electronically synthesized and played-back ("phantom") echo was used. Each electronic echo was triggered by an emitted biosonar pulse. The echo had a spectrum similar to that of the emitted biosonar clicks, and its intensity was proportional to that of the emitted click. The attenuation of the echo relative to the emitted click and its delay was controlled by the experimenter. Four combinations of echo attenuation and delay were tested (-31 dB, 2 ms), (-40 dB, 4 ms), (-49 dB, 8 ms), and (-58 dB, 16 ms); thus, attenuation and delay were associated with a rate of 9 dB of increased attenuation per delay doubling. AEPs related to emitted clicks displayed a regular amplitude dependence on the click level. Echo-related AEPs did not feature amplitude dependence on echo attenuation or emitted click levels, except in a few combinations of the lowest values of these two variables. The results are explained by a hypothesis that partial forward masking of the echoes by the preceding emitted sonar pulses serves as a kind of automatic gain control in the auditory system of echolocating odontocetes.
Yuen, Michelle M L; Nachtigall, Paul E; Breese, Marlee; Supin, Alexander Ya
Behavioral and auditory evoked potential (AEP) audiograms of a false killer whale were measured using the same subject and experimental conditions. The objective was to compare and assess the correspondence of auditory thresholds collected by behavioral and electrophysiological techniques. Behavioral audiograms used 3-s pure-tone stimuli from 4 to 45 kHz, and were conducted with a go/no-go modified staircase procedure. AEP audiograms used 20-ms sinusoidally amplitude-modulated tone bursts from 4 to 45 kHz, and the electrophysiological responses were received through gold disc electrodes in rubber suction cups. The behavioral data were reliable and repeatable, with the region of best sensitivity between 16 and 24 kHz and peak sensitivity at 20 kHz. The AEP audiograms produced thresholds that were also consistent over time, with range of best sensitivity from 16 to 22.5 kHz and peak sensitivity at 22.5 kHz. Behavioral thresholds were always lower than AEP thresholds. However, AEP audiograms were completed in a shorter amount of time with minimum participation from the animal. These data indicated that behavioral and AEP techniques can be used successfully and interchangeably to measure cetacean hearing sensitivity.
Klinkenberg, Inge; Sambeth, Anke; Blokland, Arjan
As perturbations in auditory filtering appear to be a candidate trait marker of schizophrenia, there has been considerable interest in the development of translational rat models to elucidate the underlying neural and neurochemical mechanisms involved in sensory gating. This is the first study to investigate the effects of the non-selective muscarinic antagonist scopolamine, the muscarinic M1 antagonist biperiden and the cholinesterase inhibitor donepezil (also in combination with scopolamine and biperiden) on auditory evoked potentials (AEPs) and sensory gating. In the saline condition, only the N50 peak displayed sensory gating. Scopolamine and biperiden both disrupted sensory gating by increasing N50 amplitude for the S2 click. Donepezil was able to fully reverse the effects of biperiden on N50 sensory gating, but had residual effects when combined with scopolamine; i.e., it enhanced sensory gating by increasing N50 amplitude of the S1 stimulus. Donepezil by itself improved sensory gating by enhancing N50 amplitude of S1, and reducing N50 amplitude of the S2 click. In conclusion, due to its relatively more selective effects biperiden is to be preferred over scopolamine as a means for pharmacologically inducing cholinergic impairments in auditory processing in healthy rats. Changes in auditory processing and sensory gating induced by cholinergic drugs may serve as a translational model for aging instead of schizophrenia.
Lascano, Agustina M; Lalive, Patrice H; Hardmeier, Martin; Fuhr, Peter; Seeck, Margitta
Evoked potentials (EPs) are a powerful and cost-effective tool for evaluating the integrity and function of the central nervous system. Although imaging techniques, such as MRI, have recently become increasingly important in the diagnosis of neurological diseases, over the past 30 years, many neurologists have continued to employ EPs in specific clinical applications. This review presents an overview of the recent evolution of 'classical' clinical applications of EPs in terms of early diagnosis and disease monitoring and is an extension of a previous review published in this journal in 2005 by Walsh and collaborators. We also provide an update on emerging EPs based on gustatory, olfactory and pain stimulation that may be used as clinically relevant markers of neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease and cortical or peripheral impaired pain perception. EPs based on multichannel electroencephalography recordings, known as high-density EPs, help to better differentiate between healthy subjects and patients and, moreover, they provide valuable spatial information regarding the site of the lesion. EPs are reliable disease-progression biomarkers of several neurological diseases, such as multiple sclerosis and other demyelinating disorders. Overall, EPs are excellent neurophysiological tools that will expand standard clinical practice in modern neurology.
Zeyl, Jeffrey N; Johnston, Carol E
Animals exhibit unique hearing adaptations in relation to the habitat media in which they reside. This study was a comparative analysis of auditory specialization in relation to habitat medium in Testudines, a taxon that includes both highly aquatic and fully terrestrial members. Evoked potential audiograms were collected in four species groups representing diversity along the aquatic-terrestrial spectrum: terrestrial and fossorial Gopherus polyphemus, terrestrial Terrapene carolina carolina, and aquatic Trachemys scripta and Sternotherus (S. odoratus and S. minor). Additionally, underwater sensitivity was tested in T. c. carolina, T. scripta, and Sternotherus with tympana submerged just below the water surface. In aerial audiograms, T. c. carolina were most sensitive, with thresholds 18 dB lower than Sternotherus. At 100-300 Hz, thresholds in T. c. carolina, G. polyphemus, and T. scripta were similar to each other. At 400-800 Hz, G. polyphemus thresholds were elevated to 11 dB above T. c. carolina. The underwater audiograms of T. c. carolina, T. scripta, and Sternotherus were similar. The results suggest aerial hearing adaptations in emydids and high-frequency hearing loss associated with seismic vibration detection in G. polyphemus. The underwater audiogram of T. c. carolina could reflect retention of ancestral aquatic auditory function.
Lawrence, Carlie A; Barry, Robert J
The phasic evoked cardiac response (ECR) produced by innocuous stimuli requiring cognitive processing may be described as the sum of two independent response components. An initial heart rate (HR) deceleration (ECR1), and a slightly later HR acceleration (ECR2), have been hypothesised to reflect stimulus registration and cognitive processing load, respectively. This study investigated the effects of processing load in the ECR and the event-related potential, in an attempt to find similarities between measures found important in the autonomic orienting reflex context and ERP literature. We examined the effects of cognitive load within-subjects, using a long inter-stimulus interval (ISI) ANS-style paradigm. Subjects (N=40) were presented with 30-35 80dB, 1000Hz tones with a variable long ISI (7-9s), and required to silently count, or allowed to ignore, the tone in two counterbalanced stimulus blocks. The ECR showed a significant effect of counting, allowing separation of the two ECR components by subtracting the NoCount from the Count condition. The auditory ERP showed the expected obligatory processing effects in the N1, and substantial effects of cognitive load in the late positive complex (LPC). These data offer support for ANS-CNS connections worth pursuing further in future work.
Huang, Bowan; Liang, Feixue; Zhong, Lei; Lin, Minlin; Yang, Juan; Yan, Linqing; Xiao, Jinfan; Xiao, Zhongju
Auditory evoked potential (AEP) is an effective index for the effects of general anesthetics. However, it's unknown if AEP can differentiate the effects of general anesthetics on nerve fibers and synapses. Presently, we investigated AEP latency and amplitude changes to different acoustic intensities during pentobarbital anesthesia. Latency more regularly changed than amplitude during anesthesia. AEP Latency monotonically decreased with acoustic intensity increase (i.e., latency-intensity curve) and could be fitted to an exponential decay equation, which showed two components, the theoretical minimum latency and stimulus-dependent delay. From the latency-intensity curves, the changes of these two components (∆L and ∆I) were extracted during anesthesia. ∆L and ∆I monitored the effect of pentobarbital on nerve fibers and synapses. Pentobarbital can induce anesthesia, and two side effects, hypoxemia and hypothermia. The hypoxemia was not related with ∆L and ∆I. However, ∆L was changed by the hypothermia, whereas ∆I was changed by the hypothermia and anesthesia. Therefore, we conclude that, AEP latency is superior to amplitude for the effects of general anesthetics, ∆L monitors the effect of hypothermia on nerve fibers, and ∆I monitors a combined effect of anesthesia and hypothermia on synapses. When eliminating the temperature factor, ∆I monitors the anesthesia effect on synapses.
Walther, L E; Rogowski, M; Hörmann, K; Schaaf, H; Löhler, J
Cervical vestibular-evoked myogenic potential (cVEMP) and ocular VEMP (oVEMP) stimuli can be used to measure otolith function using air (AC) and bone conducted (BC) stimuli. Cervical VEMPs reflect saccular function and can be recorded using air conduction (AC), whereas oVEMPs reflect probably predominantly utricular function. Air- and bone-conducted vibration can be used, because AC oVEMP methodology seems to be fast and simple in clinical practice to measure otolith function. In this study we discuss the advantages and problems of AC oVEMP stimulation. AC oVEMP can be easily and quickly obtained within a few seconds. N10 (first negative peak) and p15 (first positive peak) latencies may be used as parameters for clinical interpretation but amplitude fluctuations are relatively large. For daily clinical use of VEMP visualization in a normogram seems feasible. Especially the AC oVEMP methodology (100 dB nHL, tone burst 500 Hz) is fast and efficient in clinical practice to measure otolith function, predominantly utricular function.
Mazinani, Babac A E; Waberski, Till D; van Ooyen, Andre; Walter, Peter
Purpose of this study was to introduce a mathematical model which allows the calculation of a source dipole as the origin of the evoked activity based on the data of three simultaneously recorded VEPs from different locations at the scalp surface to predict field potentials at any neighboring location and to validate this model by comparison with actual recordings. In 10 healthy subjects (25-38, mean 29 years) continuous VEPs were recorded via 96 channels. On the base of the recordings at the positions POz', O1' and O2', a source dipole vector was calculated for each time point of the recordings and VEP responses were back projected for any of the 96 electrode positions. Differences between the calculated and the actually recorded responses were quantified by coefficients of variation (CV). The prediction precision and response size depended on the distance between the electrode of the predicted response and the recording electrodes. After compensating this relationship using a polynomial function, the CV of the mean difference between calculated and recorded responses of the 10 subjects was 2.8 +/- 1.2%. In conclusion, the "Mini-Brainmapping" model can provide precise topographical information with minimal additional recording efforts with good reliability. The implementation of this method in a routine diagnostic setting as an "easy-to-do" procedure would allow to examine a large number of patients and normal subjects in a short time, and thus, a solid data base could be created to correlate well defined pathologies with topographical VEP changes.
Wang, Yijun; Nakanishi, Masaki; Wang, Yu-Te; Jung, Tzyy-Ping
Although the performance of steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs) has improved gradually in the past decades, it still does not meet the requirement of a high communication speed in many applications. A major challenge is the interference of spontaneous background EEG activities in discriminating SSVEPs. An SSVEP BCI using frequency coding typically does not have a calibration procedure since the frequency of SSVEPs can be recognized by power spectrum density analysis (PSDA). However, the detection rate can be deteriorated by the spontaneous EEG activities within the same frequency range because phase information of SSVEPs is ignored in frequency detection. To address this problem, this study proposed to incorporate individual SSVEP training data into canonical correlation analysis (CCA) to improve the frequency detection of SSVEPs. An eight-class SSVEP dataset recorded from 10 subjects in a simulated online BCI experiment was used for performance evaluation. Compared to the standard CCA method, the proposed method obtained significantly improved detection accuracy (95.2% vs. 88.4%, p<0.05) and information transfer rates (ITR) (104.6 bits/min vs. 89.1 bits/min, p<0.05). The results suggest that the employment of individual SSVEP training data can significantly improve the detection rate and thereby facilitate the implementation of a high-speed BCI.
Wang, Tao; Huang, Jiang-hua; Lin, Lin; Zhan, Chang'an A
To obtain reliable transient auditory evoked potentials (AEPs) from EEGs recorded using high stimulus rate (HSR) paradigm, it is critical to design the stimulus sequences of appropriate frequency properties. Traditionally, the individual stimulus events in a stimulus sequence occur only at discrete time points dependent on the sampling frequency of the recording system and the duration of stimulus sequence. This dependency likely causes the implementation of suboptimal stimulus sequences, sacrificing the reliability of resulting AEPs. In this paper, we explicate the use of continuous-time stimulus sequence for HSR paradigm, which is independent of the discrete electroencephalogram (EEG) recording system. We employ simulation studies to examine the applicability of the continuous-time stimulus sequences and the impacts of sampling frequency on AEPs in traditional studies using discrete-time design. Results from these studies show that the continuous-time sequences can offer better frequency properties and improve the reliability of recovered AEPs. Furthermore, we find that the errors in the recovered AEPs depend critically on the sampling frequencies of experimental systems, and their relationship can be fitted using a reciprocal function. As such, our study contributes to the literature by demonstrating the applicability and advantages of continuous-time stimulus sequences for HSR paradigm and by revealing the relationship between the reliability of AEPs and sampling frequencies of the experimental systems when discrete-time stimulus sequences are used in traditional manner for the HSR paradigm.
Calderón-Garcidueñas, Lilian; D’Angiulli, Amedeo; Kulesza, Randy J; Torres-Jardón, Ricardo; Osnaya, Norma; Romero, Lina; Keefe, Sheyla; Herritt, Lou; Brooks, Diane M; Avila-Ramirez, Jose; Delgado-Chávez, Ricardo; Medina-Cortina, Humberto; González-González, Luis Oscar
We assessed brainstem inflammation in children exposed to air pollutants by comparing brainstem auditory evoked potentials (BAEPs) and blood inflammatory markers in children age 96.3± 8.5 months from highly polluted (n=34) versus a low polluted city (n=17). The brainstems of nine children with accidental deaths were also examined. Children from the highly polluted environment had significant delays in wave III (t(50)=17.038; p<0.0001) and wave V (t(50)=19.730; p<0.0001) but no delay in wave I (p=0.548). They also had significantly longer latencies than controls for interwave intervals I–III, III–V, and I–V (all t(50)> 7.501; p<0.0001), consisting with delayed central conduction time of brainstem neural transmission. Highly exposed children showed significant evidence of inflammatory markers and their auditory and vestibular nuclei accumulated α synuclein and/or β amyloid 1–42. Medial superior olive neurons, critically involved in BAEPs, displayed significant pathology. Children’s exposure to urban air pollution increases their risk for auditory and vestibular impairment. PMID:21458557
KUNIEDA, Takeharu; YAMAO, Yukihiro; KIKUCHI, Takayuki; MATSUMOTO, Riki
There has been a paradigm shift in the understanding of brain function. The intrinsic architecture of neuronal connections forms a key component of the cortical organization in our brain. Many imaging studies, such as noninvasive magnetic resonance imaging (MRI) studies, have now enabled visualization of the white matter fiber tracts interconnecting the functional cortical areas in the living brain. Although such a structural connectome is essential for understanding of cortical function, the anatomical information alone is not sufficient. Practically, few techniques allow the investigation of the excitatory and inhibitory mechanisms of the cortex in vivo in humans. Several attempts have been made to track neuronal connectivity by applying direct electrical stimuli to the brain in order to stimulate subdural and/or depth electrodes and record responses from the functionally connected cortex