Local contribution to the somatosensory evoked potentials in rat's thalamus.

Local Field Potential (LFP), despite its name, often reflects remote activity. Depending on the orientation and synchrony of their sources, both oscillations and more complex waves may passively spread in brain tissue over long distances and be falsely interpreted as local activity at such distant recording sites. Here we show that the whisker-evoked potentials in the thalamic nuclei are of local origin up to around 6 ms post stimulus, but the later (7-15 ms) wave is overshadowed by a negative component reaching from cortex. This component can be analytically removed and local thalamic LFP can be recovered reliably using Current Source Density analysis. We used model-based kernel CSD (kCSD) method which allowed us to study the contribution of local and distant currents to LFP from rat thalamic nuclei and barrel cortex recorded with multiple, non-linear and non-regular multichannel probes. Importantly, we verified that concurrent recordings from the cortex are not essential for reliable thalamic CSD estimation. The proposed framework can be used to analyze LFP from other brain areas and has consequences for general LFP interpretation and analysis.

Somatosensory evoked potentials recorded from DBS electrodes: the origin of subcortical N18.

The different peaks of somatosensory-evoked potentials (SEP) originate from a variety of anatomical sites in the central nervous system. The origin of the median nerve subcortical N18 SEP has been studied under various conditions, but the exact site of its generation is still unclear. While it has been claimed to be located in the thalamic region, other studies indicated its possible origin below the pontomedullary junction. Here, we scrutinized and compared SEP recordings from median nerve stimulation through deep brain stimulation (DBS) electrodes implanted in various subcortical targets. We studied 24 patients with dystonia, Parkinson's disease, and chronic pain who underwent quadripolar electrode implantation for chronic DBS and recorded median nerve SEPs from globus pallidus internus (GPi), subthalamic nucleus (STN), thalamic ventral intermediate nucleus (Vim), and ventral posterolateral nucleus (VPL) and the centromedian-parafascicular complex (CM-Pf). The largest amplitude of the triphasic potential of the N18 complex was recorded in Vim. Bipolar recordings confirmed the origin to be close to Vim electrodes (and VPL/CM-Pf) and less close to STN electrodes. GPi recorded only far-field potentials in unipolar derivation. Recordings from DBS electrodes located in different subcortical areas allow determining the origin of certain subcortical SEP waves more precisely. The subcortical N18 of the median nerve SEP-to its largest extent-is generated ventral to the Vim in the region of the prelemniscal radiation/ zona incerta.

Anodal transcutaneous spinal direct current stimulation influences the amplitude of pain-related evoked potentials in healthy subjects.

It has already been described that transcutaneous spinal direct current stimulation (tsDCS) can selectively influence nociceptive evoked potentials. This study is the first aiming to prove an influence of tsDCS on pain-related evoked potentials (PREP) using concentric surface electrodes (CE), whose nociceptive specificity is still under discussion. 28 healthy subjects participated in this sham-controlled, double-blind cross-over study. All subjects underwent one session of anodal and one session of sham low-thoracic tsDCS. Before and after the intervention, PREP using CE, PREP-induced pain perception and somatosensory evoked potentials (SEP) were assessed on the right upper and lower limb. We found a decrease in PREP amplitude at the lower limb after sham stimulation, but not after anodal tsDCS, while SEP remained unchanged under all studied conditions. There was no difference between the effects of anodal tsDCS and sham stimulation on the studied parameters assessed at the upper limb. PREP-induced pain of the upper and lower limb increased after anodal tsDCS. The ability of influencing PREP using a CE at the spinal level in contrast to SEP suggests that PREP using CE follows the spinothalamic pathway and supports the assumption that it is specifically nociceptive. However, while mainly inhibitory effects on nociceptive stimuli have already been described, our results rather suggest that anodal tsDCS has a sensitizing effect. This may indicate that the mechanisms underlying the elicitation of PREP with CE are not the same as for the other nociceptive evoked potentials. The effects on the processing of different types of painful stimuli should be directly compared in future studies.

Diagnostic Value of Blink Reflex Combined with Trigeminal Somatosensory Evoked Potential in Trigeminal Neuralgia.

Objective: To explore the diagnostic value of blink reflex combined with trigeminal somatosensory evoked potential (TSEP) in trigeminal neuralgia. Methods: A total of 147 patients with trigeminal neuralgia were enrolled as the research objects between February 2022 and February 2023. After admission, all underwent blink reflex on affected/healthy sides and TSEP examinations. The diagnostic value of the blink reflex combined with TSEP was analyzed. Results: The latency of R1, R2, and R2' waves (refers to the different nerve signal waveforms that are recorded when a facial nerve conduction speed test is performed) on the affected side was significantly longer than that on the healthy side (t = 26.324, 18.391, 20.801,Ps < .001), and latency of W1, W2 and W3 waves was also significantly longer than that on the healthy side (t = 16.045, 10.814, 10.349, P < .001). The results of Pearson correlation analysis showed that the latency of R1, W1, W2, and W3 waves was positively correlated with the VAS score (r = 0.539, 0.611, 0.577, 0.586, P < .001). The results of receiver operating characteristic (ROC) curves analysis showed that area under the curve (AUC) values of R1, R2, R2', W1, W2, and W3 waves latency on the affected side in the diagnosis of trigeminal neuralgia were 0.753, 0.634, 0.651, 0.748, 0.756 and 0.736, respectively. The AUC of combined detection was 0.926, significantly greater than that of the single index (P < .001). Conclusion: Blink reflex combined with TSEP monitoring can improve the diagnostic value of trigeminal neuralgia, and the latency is related to pain.

Directional recordings of somatosensory evoked potentials from the sensory thalamus in chronic poststroke pain patients.

OBJECTIVE: The aim of this feasibility study was to investigate the properties of median nerve somatosensory evoked potential (SEPs) recorded from segmented Deep Brain Stimulation (DBS) leads in the sensory thalamus (VP) and how they relate to clinical and anatomical findings. METHODS: We analyzed four patients with central post-stroke pain and DBS electrodes placed in the VP. Median nerve SEPs were recorded with referential and bipolar montages. Electrode positions were correlated with thalamus anatomy and tractography-based medial lemniscus. Early postoperative clinical paresthesia mapping was performed by an independent pain nurse. Finally, we performed frequency and time-frequency analyses of the signals. RESULTS: We observed differences of SEP amplitudes recorded along different directions in the VP. SEP amplitudes did not clearly correlate to both atlas-based anatomical position and fiber-tracking results of the medial lemniscus. However, the contacts of highest SEP amplitude correlated with the contacts of lowest effect-threshold to induce paraesthesia. CONCLUSIONS: SEP recordings from directional DBS leads offer additional information about the neurophysiological (re)organization of the sensory thalamus. SIGNIFICANCE: Directional recordings of thalamic SEPs bear the potential to assist clinical decision-making in DBS for pain.

A C-shaped miniaturized coil for transcranial magnetic stimulation in rodents.

Objective.Transcranial magnetic stimulation (TMS) is a non-invasive technique widely used for neuromodulation. Animal models are essential for investigating the underlying mechanisms of TMS. However, the lack of miniaturized coils hinders the TMS studies in small animals, since most commercial coils are designed for humans and thus incapable of focal stimulation in small animals. Furthermore, it is difficult to perform electrophysiological recordings at the TMS focal point using conventional coils.Approach.We designed, fabricated, and tested a novel miniaturized TMS coil (4-by-7 mm) that consisted of a C-shaped iron powder core and insulated copper wires (30 turns). The resulting magnetic and electric fields were characterized with experimental measurements and finite element modeling. The efficacy of this coil in neuromodulation was validated with electrophysiological recordings of single-unit activities (SUAs), somatosensory evoked potentials (SSEPs), and motor evoked potentials (MEPs) in rats (n= 32) following repetitive TMS (rTMS; 3 min, 10 Hz).Main results.This coil could generate a maximum magnetic field of 460 mT and an electric field of 7.2 V m-1in the rat brain according to our simulations. With subthreshold rTMS focally delivered over the sensorimotor cortex, mean firing rates of primary somatosensory and motor cortical neurons significantly increased (154±5% and 160±9% from the baseline level, respectively); MEP and SSEP amplitude significantly increased (136±9%) and decreased (74±4%), respectively.Significance.This miniaturized C-shaped coil enabled focal TMS and concurrent electrophysiological recording/stimulation at the TMS focal point. It provided a useful tool to investigate the neural responses and underlying mechanisms of TMS in small animal models. Using this paradigm, we for the first time observed distinct modulatory effects on SUAs, SSEPs, and MEPs with the same rTMS protocol in anesthetized rats. These results suggested that multiple neurobiological mechanisms in the sensorimotor pathways were differentially modulated by rTMS.

Correlation of urodynamic studies and somatosensory evoked potential and their prognostic value in children with closed spinal dysraphism.

INTRODUCTION: Somatosensory evoked potential (SSEP) and urodynamic studies (UD) are valuable tools for assessing patients with closed spinal dysraphism (CSD) before neurosurgical intervention. No studies have correlated their findings in this cohort and our aim is to study their correlation and prognostic value in pediatric patients with closed spinal dysraphism. METHODS: Retrospective review of all patients referred to a multidisciplinary clinic in a tertiary pediatric surgical center over a 17 years period between April 2004 to September 2021 was performed. Inclusion criteria were <18 years old, diagnosed with CSD, with SSEP and UD done within 1 year of each other. Demographics data collected include age at presentation/at referral/at neurosurgical operation, gender, symptoms at presentation and intra-operative diagnoses. Pre-operative SSEP and UD findings were documented. Primary outcome was UD results in the group with normal and abnormal SSEP. Secondary outcome was urological and bowel function outcome in 4 groups of patients (Group A-both normal SSEP and UD, Group B- abnormal SSEP only, Group C - abnormal UD only and Group D-both abnormal SSEP and UD). RESULTS: A total of 45 patients were included for analysis. Mean follow up time was 118.9 months (24-216 months, SD 55.8 months). SSEP was normal in 20 patients and abnormal in 25 patients. Baseline demographics, preoperative symptoms and imaging were similar between 2 groups. Primary outcome Patients with abnormal SSEP were more likely to have abnormal UD results with a statistically significant difference (84% vs 40%, p < 0.05). They have a significantly higher end-fill detrusor pressure (12% vs 0%, p < 0.05), abnormal bladder compliance (20% vs 0%, p < 0.05), abnormal cystometric capacity (48% vs 10%, p < 0.05), poor emptying efficiency (24% vs 5%, p < 0.05) and sphincter incompetence (8% vs 0%, p < 0.05). Secondary outcome When compared to Groups A to C, patients in group D were more likely to be on anti-cholinergic (33.3% vs 4.3%, p < 0.05), required clean intermittent catheterization (42.9% vs 4.3%, p < 0.05) and had intravesical botulinum injection (19% vs 0%, p < 0.05). All the patients who had augmentation cystoplasty were in this group as well. Bowel function in terms of regular enema use was also statistically significantly higher in this group (33.4% p < 0.05). CONCLUSION: Pre-operative SSEP and UD results correlate well in patients with closed spinal dysraphism. Patients with abnormal SSEP and UD preoperatively have higher risk of urological deterioration over time. Close monitoring in this group is warranted.

Efficacy of functional electrical stimulation in rehabilitating patients with foot drop symptoms after stroke and its correlation with somatosensory evoked potentials-a crossover randomised controlled trial.

OBJECTIVE: The connectivity between somatosensory evoked potentials (SEPs) and cortical plasticity remains elusive due to a lack of supporting data. This study investigates changes in pathological latencies and amplitudes of SEPs caused by an acute stroke after 2 weeks of rehabilitation with functional electrical stimulation (FES). Furthermore, changes in SEPs and the efficacy of FES against foot drop (FD) stroke symptoms were correlated using the 10-m walk test and foot-ankle strength. METHODS: A randomised controlled two-period crossover design plus a control group (group C) was designed. Group A (n = 16) was directly treated with FES, while group B (n = 16) was treated after 2 weeks. The untreated control group of 20 healthy adults underwent repeated SEP measurements for evaluation only. RESULTS: The repeated-measures ANOVA showed a decrease in tibial nerve (TN) P40 and N50 latencies in group A after the intervention, followed by a decline in non-paretic TN SEP in latency N50 (p < 0.05). Moreover, compared to groups B and C from baseline to 4 weeks, group A showed a decrease in paretic TN latency P40 and N50 (p < 0.05). An increase in FD strength and a reduction in step cadence in group B (p < 0.05) and a positive tendency in FD strength (p = 0.12) and step cadence (p = 0.08) in group A were observed after the treatment time. The data showed a moderate (r = 0.50-0.70) correlation between non-paretic TN latency N50 and step cadence in groups A and B after the intervention time. CONCLUSION: The FES intervention modified the pathological gait in association with improved SEP afferent feedback. Registered on 25 February 2021 on ClinicalTrials.gov under identifier number: NCT04767360.

The relationships between motor behavior and sensory gating in the ball rotation task.

During voluntary muscle contraction, sensory information induced by electrostimulation of the nerves supplying the contracting muscle is inhibited and the amplitude of the corresponding somatosensory evoked potential (SEP) decreases. This phenomenon is called "gating." The reduction of the SEP amplitude is reportedly significantly larger when task performance is high. However, the relationship between dexterous movement skills and gating remains unclear. In this study, we investigated through a ball rotation (BR) task how dexterous movement skills affect the SEP amplitudes. Thirty healthy subjects performed the BR task comprising the rotation of two wooden balls as quickly as possible. We estimated the median number of ball rotations for each participant and classified the participants into two (fast and slow) groups based on the results. Moreover, we recorded SEPs, while the subjects performed BR tasks or rested. SEP amplitude reduction (P45) was significantly larger in the fast than in the slow group. We also observed that the P45 amplitude during the BR task was attenuated even more so in the case of the participants with better dexterous movement skills. Our results suggest that the participants with better dexterous movement skills might display stronger somatosensory information suppression because of increasing the motor cortex activity and the afferent input during the BR task.

[Effects of eye acupuncture on motor evoked potential and somatosensory evoked potential in patients with incomplete spinal cord injury based on neuroelectrophysiological technology].

OBJECTIVE: To observe the effects of eye acupuncture on motor evoked potential (MEP) and somatosensory evoked potential (SEP) in the patients with incomplete spinal cord injury so as to evaluate its clinical efficacy. METHODS: According to the random number table, 90 patients were divided into exercise therapy group, eye acupuncture group and eye acupuncture combined exercise therapy group (combined treatment group), 30 cases in each. In the exercise therapy group, patients were treated with the routine exercise and occupational therapy. Patients of the eye acupuncture group were treated with eye acupuncture at upper jiao region, lower jiao region, liver region and kidney region bilaterally. Patients of the combined treatment group were given the routine exercise and occupational therapy combined with eye acupuncture. All the treatments were conducted once daily, 7 days as one treatment course for 4 treatment courses. Before treatment and 4 weeks after treatment, the motor function, light touch sensation and pinprick sensation, injury grade and clinical efficacy were assessed separately, using the criteria developed by the American Spinal Injury Association. The modified Barthel index(MBI) was adopted to evaluate the activities of daily livings. By monitoring SEP and MEP, the neurophysiological conditions were assessed for spinal cord injury. RESULTS: The total effective rate was 56.7% (17/30), 66.7% (20/30) and 90.0% (27/30) in the exercise therapy group, the eye acupuncture group and the combined treatment group, respectively. The total effective rate in the combined treatment group was higher than those in the other two groups (P<0.05). Compared with those before treatment, the scores of motor function, light tough sensation and pinprick sensation were all increased after treatment in three groups (P<0.05), MBI score was increased in both the exercise therapy group and the combined treatment group (P<0.05), and the latency of SEP (N11, N20, N23, P38) and the Cortical (hand region), Csp, Cortical (leg region) and Lsp of MEP were all shortened in the three groups separately (P<0.05). After treatment, compared with the exercise therapy group, the score of motor function was increased (P<0.05), MBI score decreased (P<0.05) and MEP latency shortened (P<0.05) in the eye acupuncture group. After treatment, compared with the exercise therapy group and the eye acupuncture group, the scores of motor function, light touch sensation and pinprick sensation, as well as MBI score were all increased (P<0.05), and the latency of SEP (N11,N20,N23,P38) and MEP shortened (P<0.05) in the combined treatment group. CONCLUSION: In treatment of incomplete spinal cord injury, eye acupuncture combined with exercise therapy can significantly increase the excitability of sensory and motor nerve conduction in the spinal cord and cerebral cortex of patients, effectively promote the recovery of patients' motor and sensory function and improve the activities of daily living.

Effect of neuromorphic transcutaneous electrical nerve stimulation (nTENS) of cortical functional networks on tactile perceptions: an event-related electroencephalogram study.

Background.Transcutaneous electrical nerve stimulation (TENS) is generally applied for tactile feedback in the field of prosthetics. The distinct mechanisms of evoked tactile perception between stimulus patterns in conventional TENS (cTENS) and neuromorphic TENS (nTENS) are relatively unknown. This is the first study to investigate the neurobiological effect of nTENS for cortical functional mechanism in evoked tactile perception.Methods.Twenty-one healthy participants were recruited in this study. Electroencephalogram (EEG) was recorded while the participants underwent a tactile discrimination task. One cTENS pattern (square pattern) and two nTENS patterns (electromyography and single motor unit patterns) were applied to evoke tactile perception in four fingers, including the right and left index and little fingers. EEG was preprocessed and somatosensory-evoked potentials (SEPs) were determined. Then, source-level functional networks based on graph theory were evaluated, including clustering coefficient, path length, global efficiency, and local efficiency in six frequency bands.Main results.Behavioral results suggested that the single motor units (SMUs) pattern of nTENS was the most natural tactile perception. SEPs results revealed that SMU pattern exhibited significant shorter latency in P1 and N1 components than the other patterns, while nTENS patterns have significantly longer latency in P3 component than cTENS pattern. Cortical functional networks showed that the SMU pattern had the lowest short path and highest efficiency in beta and gamma bands.Conclusion.This study highlighted that distinct TENS patterns could affect brain activities. The new characteristics in tactile manifestation of nTENS would provide insights for the application of tactile perception restoration.

Involvement of central sensory pathways in subjects with restless legs syndrome: A neurophysiological study.

In patients with restless legs syndrome (RLS) a motor cortical disinhibition has been reported in transcranial magnetic stimulation (TMS) studies, but the neuronal excitability in other cortical areas has been poorly explored. The aim of this study was the functional evaluation of thalamo-cortical circuits and inhibitory cortical responses in the sensory cortex in RLS. We assessed the high-frequency somatosensory evoked potentials (HF-SEP) in sixteen subjects suffering from RLS of different degrees of severity. In patients with severe or very severe RLS we found a significant desynchronization with amplitude reduction of both pre- and post-synaptic HF-SEP bursts, which suggest an impairment in the thalamo-cortical projections and in the cortical inhibitory interneurons activity, respectively. The assessment of the central sensory pathways by means of HF-SEP may shed light on the pathophysiological mechanisms of RLS.

STDP and the distribution of preferred phases in the whisker system.

Rats and mice use their whiskers to probe the environment. By rhythmically swiping their whiskers back and forth they can detect the existence of an object, locate it, and identify its texture. Localization can be accomplished by inferring the whisker's position. Rhythmic neurons that track the phase of the whisking cycle encode information about the azimuthal location of the whisker. These neurons are characterized by preferred phases of firing that are narrowly distributed. Consequently, pooling the rhythmic signal from several upstream neurons is expected to result in a much narrower distribution of preferred phases in the downstream population, which however has not been observed empirically. Here, we show how spike timing dependent plasticity (STDP) can provide a solution to this conundrum. We investigated the effect of STDP on the utility of a neural population to transmit rhythmic information downstream using the framework of a modeling study. We found that under a wide range of parameters, STDP facilitated the transfer of rhythmic information despite the fact that all the synaptic weights remained dynamic. As a result, the preferred phase of the downstream neuron was not fixed, but rather drifted in time at a drift velocity that depended on the preferred phase, thus inducing a distribution of preferred phases. We further analyzed how the STDP rule governs the distribution of preferred phases in the downstream population. This link between the STDP rule and the distribution of preferred phases constitutes a natural test for our theory.

The Gliopeptide ODN, a Ligand for the Benzodiazepine Site of GABAA Receptors, Boosts Functional Recovery after Stroke.

Following stroke, the survival of neurons and their ability to reestablish connections is critical to functional recovery. This is strongly influenced by the balance between neuronal excitation and inhibition. In the acute phase of experimental stroke, lethal hyperexcitability can be attenuated by positive allosteric modulation of GABAA receptors (GABAARs). Conversely, in the late phase, negative allosteric modulation of GABAAR can correct the suboptimal excitability and improves both sensory and motor recovery. Here, we hypothesized that octadecaneuropeptide (ODN), an endogenous allosteric modulator of the GABAAR synthesized by astrocytes, influences the outcome of ischemic brain tissue and subsequent functional recovery. We show that ODN boosts the excitability of cortical neurons, which makes it deleterious in the acute phase of stroke. However, if delivered after day 3, ODN is safe and improves motor recovery over the following month in two different paradigms of experimental stroke in mice. Furthermore, we bring evidence that, during the subacute period after stroke, the repairing cortex can be treated with ODN by means of a single hydrogel deposit into the stroke cavity.SIGNIFICANCE STATEMENT Stroke remains a devastating clinical challenge because there is no efficient therapy to either minimize neuronal death with neuroprotective drugs or to enhance spontaneous recovery with neurorepair drugs. Around the brain damage, the peri-infarct cortex can be viewed as a reservoir of plasticity. However, the potential of wiring new circuits in these areas is restrained by a chronic excess of GABAergic inhibition. Here we show that an astrocyte-derived peptide, can be used as a delayed treatment, to safely correct cortical excitability and facilitate sensorimotor recovery after stroke.

Intraoperative thalamocortical tract monitoring via direct cortical recordings during craniotomy.

OBJECTIVE: Neuromonitoring of primary motor regions allows preservation of motor strength and is frequently employed during cranial procedures. Less is known about protection of sensory function and ability to modulate movements, both of which rely on integrity of thalamocortical afferents (TCA) to fronto-parietal regions. We describe our experience with TCA monitoring and their cortical relays during brain tumor surgery. METHODOLOGY: To study its feasibility and usefulness, continuous somatosensory evoked potentials (SSEP) recording via a subdural electrode was attempted in 32 consecutive patients. RESULTS: Median and posterior tibial SSEP were successfully monitored in 31 and 17 patients respectively. SSEP improved lesion localization and prevented unnecessary cortical stimulation in 9 and 16 cases respectively. A threshold of ≥30% SSEP amplitude decrease influenced management in 10 patients while a decrement of ≥50 % had a sensitivity of 0.89 and specificity of 1 in detecting worsening of sensory function. Simultaneous motor evoked potentials (MEP) and SSEP monitoring were performed in 10 cases, 9 of which showed short-lived fluctuations of the former. CONCLUSION: Direct cortical SSEP monitoring is feasible, informs management and predicts outcome. SIGNIFICANCE: Early intervention prevents sensory deficit. Concomitant MEP fluctuations may reflect modulation of motor activity by TCA.

Inhibition of cortical somatosensory processing during and after low frequency peripheral nerve stimulation in humans.

OBJECTIVE: Transcutaneous low-frequency stimulation (LFS) elicits long-term depression-like effects on human pain perception. However, the neural mechanisms underlying LFS are poorly understood. We investigated cortical activation changes occurring during LFS and if changes were associated with reduced nociceptive processing and increased amplitude of spontaneous cortical oscillations post-treatment. METHODS: LFS was applied to the radial nerve of 25 healthy volunteers over two sessions using active (1 Hz) or sham (0.02 Hz) frequencies. Changes in resting electroencephalography (EEG) and laser-evoked potentials (LEPs) were investigated before and after LFS. Somatosensory-evoked potentials were recorded during LFS and source analysis was carried out. RESULTS: Ipsilateral midcingulate and operculo-insular cortex source activity declined linearly during LFS. Active LFS was associated with attenuated long-latency LEP amplitude in ipsilateral frontocentral electrodes and increased resting alpha (8-12 Hz) and beta (16-24 Hz) band power in electrodes overlying operculo-insular, sensorimotor and frontal cortical regions. Reduced ipsilateral operculo-insular cortex source activity during LFS correlated with a smaller post-treatment alpha-band power increase. CONCLUSIONS: LFS attenuated somatosensory processing both during and after stimulation. SIGNIFICANCE: Results further our understanding of the attenuation of somatosensory processing both during and after LFS.

Reducing False Triggering Caused by Irrelevant Mental Activities in Brain-Computer Interface Based on Motor Imagery.

In recent years, the brain-computer interface (BCI) based on motor imagery (MI) has been considered as a potential post-stroke rehabilitation technology. However, the recognition of MI relies on the event-related desynchronization (ERD) feature, which has poor task specificity. Further, there is the problem of false triggering (irrelevant mental activities recognized as the MI of the target limb). In this paper, we discuss the feasibility of reducing the false triggering rate using a novel paradigm, in which the steady-state somatosensory evoked potential (SSSEP) is combined with the MI (MI-SSSEP). Data from the target (right hand MI) and nontarget task (rest) were used to establish the recognition model, and three kinds of interference tasks were used to test the false triggering performance. In the MI-SSSEP paradigm, ERD and SSSEP features modulated by MI could be used for recognition, while in the MI paradigm, only ERD features could be used. The results showed that the false triggering rate of interference tasks with SSSEP features was reduced to 29.3%, which was far lower than the 55.5% seen under the MI paradigm with ERD features. Moreover, in the MI-SSSEP paradigm, the recognition rate of the target and nontarget task was also significantly improved. Further analysis showed that the specificity of SSSEP was significantly higher than that of ERD (p < 0.05), but the sensitivity was not significantly different. These results indicated that SSSEP modulated by MI could more specifically decode the target task MI, and thereby may have potential in achieving more accurate rehabilitation training.

Effects of the noncompetitive AMPA receptor antagonist perampanel on thalamo-cortical excitability: A study of high-frequency oscillations in somatosensory evoked potentials.

OBJECTIVE: Wedesignedalongitudinalcohortstudyon People with Epilepsy (PwE) with the aimofassessingthe effect of Perampanel (PER) oncortico-subcortical networks, as measured by high-frequency oscillations of somatosensory evoked potentials (SEP-HFOs). SEP-HFOs measure the excitability of both thalamo-corticalprojections(early HFOs) and intracortical GABAergic synapses (late HFOs), thus they could be used to study the anti-glutamatergic action of PER, a selective antagonist of the AMPA receptor. METHODS: 15 PwE eligible for PER add-on therapy, were enrolled prospectively. Subjects underwent SEPs recording from the dominant hand at two times: PwET0 (baseline, before PER titration) and PwET1 (therapeutic dose of 4 mg). HFOs were obtained by filtering N20 scalp response in the 400-800 Hz range. Patients were compared with a normative population of 15 healthy controls (HC) matched for age and sex. RESULTS: We found a significant reduction ofTotal HFOs and mostly early HFOs area between PwET0 and PwET1 (p = 0.05 and p = 0.045 respectively) and between HC and PwET1 (p = 0.01). Furthermore, we found a significant reduction of P24/N24 Amplitude between PwET0 and HC and between PwET0 and PwET1 (p = 0.006 and p = 0.032, respectively). CONCLUSIONS: Introduction of PER as add-on therapy reduced the area of total HFOs, acting mainly on the early burst, related to thalamo-cortical pathways. Furthermore P24/N24 amplitude, which seems to reflect a form of cortico-subcortical integration, resulted increased in PwE at T0 and normalized at T1. SIGNIFICANCE: Our findings suggest that PER acts on cortico-subcortical excitability. This could explain the broad spectrum of PER and its success in forms of epilepsy characterized by thalamo-cortical hyperexcitability.

[Effect of electroacupuncture of Taichong (LR3) on somatosensory evoked cortical potentials in healthy volunteers].

OBJECTIVE: To explore the excitatory effect of the sensory cortex through somatic electroacupuncture (EA) stimulation at Taichong (LR3). METHODS: Ten healthy volunteer men ranging in age from 20 to 50 years were enrolled in this study. EA (2 Hz, a tolerable strength) was applied to the left LR3. Before and after EA, the somatosensory evoked potential (SEP) from the Cz' area of the scalp was recorded by electrical stimulation of the bilateral dorsal penile nerves and the indentation behind the medial malleolus of the foot, termed as the pudendal SEP (PSEP) and lower extremity SEP (LSEP), respectively. RESULTS: The amplitude of the left LSEP induced by stimulation of the left medial malleolus was significantly increased after EA (P < 0.05), but there were no significant changes in the latency of LSEP and PSEP, and the amplitude of right LSEP evoked by stimulation of the left medial malleolus, and that of the PSEP. CONCLUSION: EA at LR3 increases the excitability of the contralateral cerebral sensory cortex (lower extremity area), but has no effect on the adjacent sensory cortex (genital area).

An increase in dendritic plateau potentials is associated with experience-dependent cortical map reorganization.

The organization of sensory maps in the cerebral cortex depends on experience, which drives homeostatic and long-term synaptic plasticity of cortico-cortical circuits. In the mouse primary somatosensory cortex (S1) afferents from the higher-order, posterior medial thalamic nucleus (POm) gate synaptic plasticity in layer (L) 2/3 pyramidal neurons via disinhibition and the production of dendritic plateau potentials. Here we address whether these thalamocortically mediated responses play a role in whisker map plasticity in S1. We find that trimming all but two whiskers causes a partial fusion of the representations of the two spared whiskers, concomitantly with an increase in the occurrence of POm-driven N-methyl-D-aspartate receptor-dependent plateau potentials. Blocking the plateau potentials restores the archetypical organization of the sensory map. Our results reveal a mechanism for experience-dependent cortical map plasticity in which higher-order thalamocortically mediated plateau potentials facilitate the fusion of normally segregated cortical representations.