Pattern-specific changes and discordant prognostic values of individual leg-muscle motor evoked potentials during spinal surgery

ObjectiveThe aim of the study is to evaluate the efficacy of muscle motor evoked potentials (mMEPs) in individual leg muscles for spinal surgery monitoring.MethodsData were obtained from 209 patients who underwent spine surgery with intra-operative mMEP monitoring in the tibialis anterior (TA) and abductor hallucis (AH) muscles. The mMEP generation, pattern-specific mMEP loss and recovery, and the accuracy of individual mMEP changes in predicting postoperative motor deficit were assessed.ResultsGeneration rate of mMEPs was higher in the AH than in the TA (p < 0.001). The mMEP in the TA was more sensitive in detecting mMEP loss than in the AH (p < 0.001); however, mMEP in the AH was more sensitive in detecting mMEP recovery (p < 0.001). The mMEPs in the TA had high sensitivity in predicting sustained postoperative motor deficits. By contrast, mMEPs in the AH showed a high positive predictive value.ConclusionsAlthough mMEPs were generated at a high rate in the AH, mMEP in the TA can play an important complementary role in intra-operative mMEP monitoring, because mMEP in the TA can be more sensitive to potential neural damage.SignificanceUsing a combination of muscles with individual sensitivities and clinical significances will improve intra-operative mMEP monitoring strategies.     

Need for head and neck repositioning to restore electrophysiological signal changes at positioning for cervical myelopathy surgery

ObjectiveTo evaluate the incidence of significant intraoperative electrophysiological signal changes during surgical positioning, and to assess the effectiveness of head and neck repositioning on the restoration of signals, among patients undergoing surgery for cervical myelopathy.Material and methodsWe used multimodal intraoperative monitoring (somatosensory [SEP] and motor evoked potentials [MEP] and spontaneous electromyography) before and after patients’ positioning in a consecutive cohort of 103 patients operated for symptomatic cervical myelopathy. Significant changes were defined as > 50% attenuation in amplitude or > 10% increase in latency of SEP, or abolishment or 50–80% attenuation of MEP.ResultsOut of 103 patients (34.9% female, median age 54.5 years) 88 underwent laminectomy (85.4%) and 15 (14.6%) anterior approach. At the time of positioning, signal alterations occurred in 44 patients (42.7%), yet only 11 patients (10.7%) showed alarming changes. Immediate neck repositioning of these resulted in complete (n = 6) or partial (n = 4) restoration of potentials, yielding no postoperative deficits. The patient in which signals could not be restored after repositioning resulted in added postoperative deficit. The accuracy (true positives plus true negatives) of monitoring to detect new neurological deficits was 99.0% (102/103) for the entire cohort, and 100% (11/11) for those showing significant changes at the moment of positioning. Overall, only 1 patient, with non-significant SEP attenuation, experienced a new postoperative deficit, yielding a 0.97% rate of false negatives.ConclusionAmong patients undergoing surgery for cervical myelopathy, 10.7% showed alarming electrophysiological signal changes at the time of positioning. Immediate repositioning of the neck resulted in near always restoration of potentials and avoidance of added neurological damage. Complete or partial restoration of potentials after repositioning yielded no postoperative deficits.     

Mirroring of a simple motor behavior in Disorders of Consciousness

ObjectiveIn patients suffering from Disorders of Consciousness (DOC) electrophysiological recordings at bedside could serve as a complimentary and economical tool to improve diagnosis. We utilized a motor observation and imagination paradigm to gain new insights on preserved cognitive processing in DOC.MethodsEEG brain oscillations were analyzed in 10 VS/UWS (Vegetative State/Unresponsive Wakefulness Syndrome) patients and 7 MCS (Minimally Conscious State) patients and 21 controls during observation and imagination of a grasping movement and group statistics were conducted.ResultsWhile control subjects showed a typical desynchronization at 8–15 Hz during observation of a movement, MCS patients presented an analogue response at 8–10 Hz, but exhibited a synchronization at 12–15 Hz. The VS group did not show a systematic response. Imagery-related activation was only sustained for 1500 ms even in control subjects, therefore, limiting conclusions regarding the ability to follow an instruction. Furthermore, a clinically diagnosed VS patient exhibited EEG responses indicative for MCS.ConclusionResults indicate that MCS patients are still able to process an observed motor behavior on a basic sensory and perhaps even pre-motoric level, but seem not to be capable of “mirroring” the movement like healthy participants.Significance“Real-world” tasks as presented here carry the potential to identify residual cognitive functioning in DOC patients and may ultimately help to lower misdiagnosis rates.     

Altered cortical excitability in patients with untreated obstructive sleep apnea syndrome

ObjectiveTo investigate cortical excitability in patients with obstructive sleep apnea syndrome (OSAS) during wakefulness.MethodsThe authors recruited 45 untreated severe OSAS (all males, mean age 47.2 years, mean apnea–hypopnea index = 44.6 h^?1) patients and 44 age-matched healthy male volunteers (mean apnea–hypopnea index = 3.4 h^?1). The TMS parameters measured were resting motor threshold (RMT), motor evoked potential (MEP) amplitude, cortical silent period (CSP), and short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). These parameters were measured in the morning (9–10 am) more than 2 h after arising and the parameters of patients and controls were compared. The Epworth Sleepiness Scale (ESS) and the Stanford Sleepiness Scale (SSS) were also measured before the TMS study.ResultsOSAS patients had a significantly higher RMT and a longer CSP duration (t-test, p < 0.001) compared to healthy volunteers. No significant difference was observed between MEP amplitudes at any stimulus intensity or between the SICI (2, 3, 5 ms) and ICF (10, 15, 20 ms) values of OSAS patients and healthy volunteers (p > 0.05).ConclusionsThis TMS-based study suggests that untreated severe OSAS patients have imbalanced cortical excitabilities that enhanced inhibition or decreased brain excitability when awake during the day.     

Motor cortex dysfunction in complex regional pain syndrome

ObjectiveMost patients with complex regional pain syndrome (CRPS) exhibit debilitating motor symptoms. The effect of continuous pain on motor system in CRPS, however, is not well known. We searched for signs of motor cortex dysfunction in chronic CRPS type 1 patients with motor impairment.MethodsWe recorded rhythmic brain activity with magnetoencephalography (MEG) during noxious thulium–laser stimulation of both hands in eight CRPS patients and eight control subjects. We measured excitability of the motor cortex by monitoring the reactivity of the ∼20-Hz motor cortex rhythm to laser stimuli. The reactivity was defined as a sum of the stimulus-induced suppression and the subsequent rebound of the ∼20-Hz rhythm.ResultsIn CRPS, the reactivity of the ∼20-Hz rhythm in the hemisphere contralateral to the painful hand was significantly weaker than in control subjects. The reactivity correlated with the mean level of the spontaneous pain (r = −0.64, P = 0.04). Suppression of the ∼20-Hz rhythm correlated with the grip strength in the painful hand (r = 0.66, P = 0.04).ConclusionContinuous pain in CRPS is associated with attenuated motor cortex reactivity.SignificanceAbnormal motor cortex reactivity may be linked with motor dysfunction of the affected hand in CRPS.     

The Wada test might predict postoperative fine finger motor deficit after hemispherotomy

IntroductionCerebral hemispherotomy is a surgical method with a high rate of seizure reduction in patients with intractable epilepsy. However, there is a probability of postoperative motor deficits. The objective of this study was to investigate whether the Wada test can help predict motor function outcomes after hemispherotomy and, therefore, may be useful in decision-making and patient selection.Patients and methodA total of 13 patients with hemispherical intractable epilepsy underwent hemispherical disconnection surgeries. Six of them underwent the Wada test to evaluate motor function and language function followed by peri-insula hemispherotomy. The patients’ age ranged from 11 to 45 years (mean 27 years).ResultsThree of six patients had reduced dexterity on the Wada test. The finger motor function in the other patients did not change on the Wada test. Postoperatively, all patients who had decreased fine motor movement on the Wada test showed postoperative clumsiness of their hands and fingers.ConclusionsThe Wada test might predict postoperative fine finger motor deficit after hemispherotomy. This study showed that gross motor function was compensated in the ipsilateral hemisphere, whereas fine finger motor movement function remained in the contralateral frontal cortex.     

Motor unit number index (MUNIX) versus motor unit number estimation (MUNE): a direct comparison in a longitudinal study of ALS patients

ObjectiveTo evaluate how the motor unit number index (MUNIX) is related to high-density motor unit number estimation (HD-MUNE) in healthy controls and patients with amyotrophic lateral sclerosis (ALS).MethodsBoth MUNIX and HD-MUNE were performed on the thenar muscles in 18 ALS patients and 24 healthy controls. Patients were measured at baseline, within 2 weeks, and after 4 and 8 months. Clinical evaluation included Medical Research Council (MRC) scale and the ALS functional rating scale (ALSFRS).ResultsThere was a significant positive correlation between MUNE and MUNIX values in ALS patients (r = 0.49 at baseline; r = 0.56 at 4 months; r = 0.56 at 8 months, all p < 0.05), but not in healthy controls. After 8 months, both MUNE and MUNIX values of the ALS patients decreased significantly more compared to MRC scale, ALS functional rating scale (ALSFRS) and compound muscle action potential (CMAP) (p < 0.05). There was no significant difference in relative decline of MUNIX and HD-MUNE values.ConclusionsIn ALS patients, MUNIX and HD-MUNE are significantly correlated. MUNIX has an almost equivalent potential in detecting motor neuron loss compared to HD-MUNE.SignificanceMUNIX could serve as a reliable and sensitive marker for monitoring disease progression in ALS.     

Validation of Chinese version of the Morisky Medication Adherence Scale in patients with epilepsy

PurposeThis study aimed to validate a Chinese version of the Morisky Medication Adherence Scale (MMAS-8) in patients with epilepsy. The relationships between adherence, seizure frequency, and adverse effects were assessed using this method.MethodsData from patients diagnosed with epilepsy at the Department of Neurology of Huashan Hospital were collected between January and June 2013. To validate the MMAS-8, internal consistency, test–retest reliability, and factor analysis were calculated. Relationships between adherence, seizure frequency, and adverse effects were assessed using Pearson's correlation.ResultsOne hundred and eleven patients were recruited. The MMAS-8 had moderate internal consistency (Cronbach's α = 0.556) and good test–retest reliability (intraclass correlation coefficient = 0.729). The MMAS-8 adherence rate was 79.2%. MMAS-8 adherence was negatively correlated with seizure frequency and adverse effects (r = –0.708, p < 0.001; r = –0.484, p < 0.001).ConclusionThe MMAS-8 scale can be used as a tool to assess medication adherence in Chinese patients with epilepsy. Better seizure control and lower rates of adverse effects were significantly correlated with higher adherence scores.     

The relationship of motor skills and adaptive behavior skills in young children with autism spectrum disorders

ObjectiveTo determine the relationship of motor skills and adaptive behavior skills in young children with autism.DesignA multiple regression analysis tested the relationship of motor skills on the adaptive behavior composite, daily living, adaptive social and adaptive communicative skills holding constant age, non-verbal problem solving, and calibrated autism severity.SettingMajority of the data collected took place in an autism clinic.ParticipantsA cohort of 233 young children with ASD (n = 172), PDD-NOS (n = 22) and non-ASD (developmental delay, n = 39) between the ages of 14–49 months were recruited from early intervention studies and clinical referrals. Children with non-ASD (developmental delay) were included in this study to provide a range of scores indicted through calibrated autism severity.InterventionsNot applicable.Main outcome measuresThe primary outcome measures in this study were adaptive behavior skills.ResultsFine motor skills significantly predicted all adaptive behavior skills (p < 0.01). Gross motor skills were predictive of daily living skills (p < 0.05). Children with weaker motor skills displayed greater deficits in adaptive behavior skills.ConclusionsThe fine and gross motor skills are significantly related to adaptive behavior skills in young children with autism spectrum disorder. There is more to focus on and new avenues to explore in the realm of discovering how to implement early intervention and rehabilitation for young children with autism and motor skills need to be a part of the discussion.     

Automatic detection and analysis of the EEG sharp wave-slow wave patterns evoked by fluorinated inhalation anesthetics

ObjectiveThe aim of this study was to develop a method for the automatic detection of sharp wave–slow wave (SWSW) patterns evoked in EEG by volatile anesthetics and to identify the patterns’ characteristics.MethodsThe proposed method consisted in the k-NN classification with a reference set obtained using expert knowledge, the morphology of the EEG patterns and the condition for their synchronization. The decision rules were constructed and evaluated using 24 h EEG records in ten patients.ResultsThe sensitivity, specificity and selectivity of the method were 0.88 ± 0.10, 0.81 ± 0.13 and 0.42 ± 0.16, respectively. SWSW patterns’ recruitment was strictly dependent on anesthetic concentration. SWSW patterns evoked by different types of anesthetics expressed different characteristics.ConclusionsSynchronization criterion and adequately selected morphological features of “slow wave” were sufficient to achieve the high sensitivity and specificity of the method.SignificanceThe monitoring of SWSW patterns is important in view of possible side effects of volatile anesthetics. The analysis of SWSW patterns’ recruitment and morphology could be helpful in the diagnosis of the anesthesia effects on the CNS.     

Gustatory and olfactory sensitivity in patients with anorexia and bulimia in the course of treatment

BackgroundThe majority of studies on taste and smell in eating disorders have revealed several alterations of olfactory or gustatory functions. Aim of this prospective study was to employ detailed olfactory and gustatory testing in female subjects of three homogenous groups – anorexia nervosa, bulimia nervosa and healthy controls – and to look at the effects of treatment on these measures.MethodsSixteen hospitalized female patients with anorexia (restricting type, mean age [M] = 24.5 years), 24 female patients with bulimia (purging type, M = 24.3 years) as well as 23 healthy controls (M = 24.5 years) received olfactory (“Sniffin’ Sticks”) and gustatory testing (“Taste Strips”). Group differences in olfactory and gustatory sensitivity, body mass index (BMI), the Beck depression inventory, the eating attitudes test (EAT), and the influence of therapy on gustatory and olfactory function were investigated.Results(1) Group differences were present for odor discrimination and overall olfactory function with anorexic patients having the lowest scores. (2) Regarding taste function, controls scored higher than patients with anorexia. (3) At admission small but significant correlations were found between overall olfactory function and body weight (r₆₃ = 0.35), BMI (r₆₃ = 0.37), and EAT score (r₆₃ = −0.27). Similarly, (4) the taste test score correlated significantly with body weight (r₆₃ = 0.48), and BMI (r₆₃ = 0.45). Finally, (5) at discharge overall olfactory and gustatory function were significantly higher compared to admission in anorexic patients.ConclusionsAs compared to healthy controls and bulimic patients our results show lowered olfactory and gustatory sensitivities in anorexic patients that improved with increasing BMI and decreasing eating pathology in the course of treatment.     

Acute effects of lithium on excitability of human motor cortex

ObjectiveLithium has been widely used to treat bipolar affective disorder for over 60 years. Still, its acute effects in human cerebral cortex are poorly understood. This study aimed at investigating the acute effects of lithium on motor cortex excitability as measured by transcranial magnetic stimulation (TMS).MethodsTen healthy young adults participated in a double-blind placebo-controlled randomized crossover study with four sessions, where a single oral dose of lithium carbonate (450 mg, 900 mg, or 1350 mg) or placebo was tested. Focal TMS of the hand area of left motor cortex was used to test resting and active motor thresholds, motor evoked potential input–output curve (MEP IO-curve), slope of the MEP IO-curve and paired-pulse measures of intracortical inhibition and facilitation before, and two and four hours after drug administration.ResultsTwo hours post drug administration, 450 mg of lithium carbonate increased the slope of the MEP IO-curve while 1350 mg tended to decrease it. Lithium had no effect on motor thresholds, or intracortical inhibition or facilitation.ConclusionsThe acute effects of lithium on MEP IO-curve, a marker of corticospinal excitability, are consistent with an inverted U-shaped dose–response relationship.SignificanceFindings are important for our understanding of the therapeutic and toxic effects of lithium on the human central nervous system.     

Outpatient cardiac telemetry detects a high rate of atrial fibrillation in cryptogenic stroke

BackgroundThe etiology of cerebral ischemia is undetermined in one-third of patients upon discharge. Occult paroxysmal atrial fibrillation (PAF) is considered a potential etiology. A high rate of PAF detection with 21-day mobile cardiac outpatient telemetry (MCOT) has been reported in two small studies. Optimal monitoring duration and factors predicting PAF have not been adequately defined.MethodsWe performed a retrospective analysis on patients evaluated by MCOT monitoring within 6 months of a cryptogenic stroke or TIA. Multivariate analysis with survival regression methods was performed using baseline characteristics to determine predictive risk factors for detection of PAF. Kaplan–Meier estimates were computed for 21-day PAF rates.ResultsWe analyzed 156 records; PAF occurred in 27 of 156 (17.3%) patients during MCOT monitoring of up to 30 days. The rate of PAF detection significantly increased from 3.9% in the initial 48 h, to 9.2% at 7 days, 15.1% at 14 days, and 19.5% by 21 days (p < 0.05). Female gender, premature atrial complex on ECG, increased left atrial diameter, reduced left ventricular ejection fraction and greater stroke severity were independent predictors of PAF detection on multivariate analysis with strongest correlation seen for premature atrial complex on ECG (HR 13.7, p = 0.001).ConclusionMCOT frequently detects PAF in patients with cryptogenic stroke and TIA. Length of monitoring is strongly associated with detection of PAF, with an optimal monitoring period of at least 21 days. Of the predictors of PAF detection, the presence of premature atrial complexes on ECG held the strongest correlation with PAF.     

Combined evoked potentials as markers and predictors of disability in early multiple sclerosis

ObjectiveTo prospectively assess combined evoked potentials (EP) as markers and predictors of the disease course of early MS over 3 years.MethodsFifty patients in the early phase of relapsing remitting MS prospectively received visual, somatosensory and motor EP and EDSS assessments at baseline (T1) and at 6 months intervals during 3 years. Spearman rank correlation was used to determine the relationship between z-transformed EP-latencies (z-EPL) and EDSS. Multivariable linear regression was performed to predict EDSS at year 3 (T7) in function of z-EPL_T1. Validity of the models was assessed using group cross-validation.ResultsAt each of the seven points in time, EDSS correlated with the sum of z-EPL (0.64 ? rho ? 0.79, p < 0.001). The change of the sum of z-EPL_T7–T1 correlated with the change of EDSS_T7–T1 (rho = 0.51, p = 0.001). EDSS_T7 as predicted by the sum of z-scores of EP latencies or by the number of pathological EP results at baseline correlated with the observed clinical values after 3 years (rho > 0.70, p < 0.001, for both measures).ConclusionsMultimodal EPs correlate well with clinical disability in cross-sectional and longitudinal comparison in early MS and allow prediction of disease evolution over 3 years.SignificanceEPs seem well suited as markers of the disease course in early MS in clinical trials and bear potential for supporting decision-finding in individual patients.     

Reliability of lower limb motor evoked potentials in stroke and healthy populations: How many responses are needed?

ObjectiveTo determine the intra- and inter-session reliability of motor evoked potential (MEP) size parameters in the lower limb of patients with stroke, focussing on the number of MEPs collected and the method of measuring MEP size.MethodsTranscranial magnetic stimulation was used to elicit MEPs in the soleus muscle of patients with stroke (n = 13) and age-matched healthy participants (n = 13) during low level muscle activation. Two sets of 10 responses were collected in the first session and a further 10 responses collected in a second session held 7 days later. Four MEP size measurements were made using 4, 6, 8, or all 10 of the MEPs collected. Intra- and inter-session reliability was examined using intraclass correlation coefficients (ICC) and typical percentage error.ResultsIntrasession ICC statistics using 6 or more MEPs were >0.85 in the stroke group but intersession values were all <0.5. Reliability was best when measuring parameters from individual MEPs rather than averaged responses.ConclusionsReliability of intrasession MEP size is excellent in the lower limb of patients with stroke using as few as 6 MEPs but intersession reliability is poor.SignificanceComparing MEP size measures across two or more sessions is questionable in the lower limb of patients with stroke.     

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

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

Zonisamide decreases cortical excitability in patients with idiopathic generalized epilepsy.

ObjectiveTo evaluate changes in cortical excitability after long-term zonisamide (ZNS) administration.MethodsFifteen drug-naïve idiopathic generalized epilepsy (IGE) patients (8 male, mean age 24.9 years) were enrolled. The transcranial magnetic stimulation (TMS) parameters obtained using two Magstim 200 stimulators were resting motor threshold (RMT), motor evoked potential (MEP) amplitudes, cortical silent period (CSP), intracortical inhibition (ICI), and intracortical facilitation (ICF). TMS parameters were compared before and after ZNS administration.ResultsAll patients were administered ZNS monotherapy (200 mg/day) for 8 weeks. No patient reported seizures during the study period. After ZNS treatment MEP amplitudes were significantly reduced in right (−34.2%) and left hemispheres (−37.0%) (Wilcoxon’s signed rank test after Bonferroni’s correction for multiple comparisons, P < 0.05). Mean RMT, CSP, and ICI/ICF were not changed by ZNS (P > 0.05).ConclusionsThese findings suggest that ZNS decreases cortical excitability in patients with IGE and a MEP amplitude is a useful TMS parameter for evaluating changes in cortical excitability induced by ZNS.SignificanceThe findings in this study are helpful to understand how ZNS affects the excitability of the motor cortex in patients with IGE.     

Triple stimulation technique findings in vascular Parkinsonism and Parkinson’s disease

ObjectiveOne of the predominant clinical features that differentiates vascular Parkinsonism (VP) from Parkinson’s disease (PD) is the pyramidal sign. The triple stimulation technique (TST) is one of the most sensitive methods for comparing upper motor neuron involvement in patients with VP and PD. This study aimed to evaluate the usefulness of the TST as a diagnostic tool for VP.MethodsThirteen VP patients, 18 PD patients and 10 age-matched healthy controls were enrolled in this study. We obtained basic participant demographic information and transcranial magnetic stimulation (TMS) parameters, including the TST amplitude ratio, from all participants. We compared the TMS parameters among the VP, PD and control groups.ResultsThe TST amplitude ratio was significantly lower in the VP group than in the PD and control groups (71.59 ± 11.86 vs. 96.42 ± 5.11 and 97.70 ± 3.82, respectively; p < 0.01). The TST amplitude ratio was positively correlated with scores obtained on the United Parkinson’s Disease Rating Scale-III, which reflects motor function.ConclusionsThe TST is an effective and easy technique that offers improved diagnostic sensitivity in patients with VP by assessing upper motor neuron involvement. The TST may also represent a useful monitoring tool for evaluating disease progression.SignificanceThis study is the first to assess pyramidal involvement in patients with VP using the collision technique.     

Bidirectional modulation of sensory cortical excitability by quadripulse transcranial magnetic stimulation (QPS) in humans

ObjectiveQuadripulse transcranial magnetic stimulation (QPS) is a newly designed patterned repetitive transcranial magnetic stimulation (TMS). Previous studies of QPS showed bidirectional effects on the primary motor cortex (M1), which depended on its inter-stimulus interval (ISI): motor evoked potentials (MEPs) were potentiated at short ISIs and depressed at long ISIs (homotopic effects). These physiological characters were compatible with synaptic plasticity. In this research, we studied effects of QPS on the primary sensory cortex (S1).MethodsOne burst consisted of four monophasic TMS pulses at an intensity of 90% active motor threshold. The ISI of four pulses was set at 5 ms (QPS-5) or at 50 ms (QPS-50). Same bursts were given every 5 s for 30 min. QPS-5 and QPS-50 were performed over three areas (M1, S1 and dorsal premotor cortex (dPMC)). One sham stimulation session was also performed. Excitability changes of S1 were evaluated by timeline of somatosensory evoked potentials (SEPs).ResultsQPS-5 over M1 or dPMC enhanced the P25–N33 component of SEP, and QPS-50 over M1 depressed it. By contrast, QPSs over S1 had no effects on SEPs.ConclusionsQPSs over motor cortices modulated the S1 cortical excitability (heterotopic effects). Mutual connections between dPMC or M1 and S1 might be responsible for these modulations.SignificanceQPSs induced heterotopic LTP or LTD-like cortical excitability changes.     

Perturbation-evoked electrodermal activity responds to instability,not just motor or sensory drives

ObjectiveTo determine whether electrodermal responses (EDRs) evoked by postural perturbations were sensitive to the context of compensatory balance control, or simply reflected sensory or motor components of the reaction.MethodsThirteen participants were perturbed backwards in an upright chair and (1) performed compensatory reach-to-grasp movements to a handhold to recover balance (COMP); (2) received the perturbation only and the chair stopped via mechanical support (SENS); and (3) performed rapid self-initiated reach-to-grasp movements without perturbation (MOT).ResultsEDRs were most frequent and largest in the COMP task, observed in 100% of trials (1.42 ± 0.16 μS), compared to 39% of SENS trials (0.31 ± 0.12 μS, p < 0.0001) and 85% of MOT trials (0.98 ± 0.25 μS, p = 0.073). EDRs in the MOT task followed two patterns across individuals, leading to post-hoc division of subjects into groups (smaller EDRs than COMP task, n = 7, versus equivalent EDRs to COMP task, n = 6). Motor patterns were equivalent in both groups, indicating that EDRs did not co vary with efferent drive.ConclusionsPerturbation-evoked EDRs are not a direct reflection of sensory input or motor drive.SignificanceThese findings suggest that evoked autonomic activity may play a functional role in compensatory postural control.