Continuous Electrical Stimulation Research Articles

Highly conductive, stretchable and biocompatible Ag-Au core-sheath nanowire composite for wearable and implantable bioelectronics.

Wearable and implantable devices require conductive, stretchable and biocompatible materials. However, obtaining composites that simultaneously fulfil these requirements is challenging due to a trade-off between conductivity and stretchability. Here, we report on Ag-Au nanocomposites composed of ultralong gold-coated silver nanowires in an elastomeric block-copolymer matrix. Owing to the high aspect ratio and percolation network of the Ag-Au nanowires, the nanocomposites exhibit an optimized conductivity of 41,850 S cm-1 (maximum of 72,600 S cm-1). Phase separation in the Ag-Au nanocomposite during the solvent-drying process generates a microstructure that yields an optimized stretchability of 266% (maximum of 840%). The thick gold sheath deposited on the silver nanowire surface prevents oxidation and silver ion leaching, making the composite biocompatible and highly conductive. Using the nanocomposite, we successfully fabricate wearable and implantable soft bioelectronic devices that can be conformally integrated with human skin and swine heart for continuous electrophysiological recording, and electrical and thermal stimulation.

BDNF-TrkB Signaling Coupled to nPKCε and cPKCβI Modulate the Phosphorylation of the Exocytotic Protein Munc18-1 During Synaptic Activity at the Neuromuscular Junction.

Munc18-1, a neuron-specific member of the Sec1/Munc18 family, is involved in neurotransmitter release by binding tightly to syntaxin. Munc18-1 is phosphorylated by PKC on Ser-306 and Ser-313 in vitro which reduces the amount of Munc18-1 able to bind syntaxin. We have previously identified that PKC is involved in neurotransmitter release when continuous electrical stimulation imposes a moderate activity on the NMJ and that muscle contraction through TrkB has an important impact on presynaptic PKC isoforms levels, specifically cPKCβI and nPKCε. Therefore, the present study was designed to understand how Munc18-1 phosphorylation is affected by (1) synaptic activity at the neuromuscular junction, (2) nPKCε and cPKCβI isoforms activity, (3) muscle contraction per se, and (4) the BDNF/TrkB signaling in a neuromuscular activity-dependent manner. We performed immunohistochemistry and confocal techniques to evidence the presynaptic location of Munc18-1 in the rat diaphragm muscle. To study synaptic activity, we stimulated the phrenic nerve (1 Hz, 30 min) with or without contraction (abolished by μ-conotoxin GIIIB). Specific inhibitory reagents were used to block nPKCε and cPKCβI activity and to modulate the tropomyosin receptor kinase B (TrkB). Main results obtained from Western blot experiments showed that phosphorylation of Munc18-1 at Ser-313 increases in response to a signaling mechanism initiated by synaptic activity and directly mediated by nPKCε. Otherwise, cPKCβI and TrkB activities work together to prevent this synaptic activity–induced Munc18-1 phosphorylation by a negative regulation of cPKCβI over nPKCε. Therefore, a balance between the activities of these PKC isoforms could be a relevant cue in the regulation of the exocytotic apparatus. The results also demonstrate that muscle contraction prevents the synaptic activity–induced Munc18-1 phosphorylation through a mechanism that opposes the TrkB/cPKCβI/nPKCε signaling.

F05. Neurophysiological effects of chronic subthreshold cortical stimulation for focal epilepsy: Spike and spontaneous ECoG activity

Neurostimulation is a treatment option for drug-resistant focal epilepsy. Chronic subthreshold cortical stimulation (CSCS) is a novel, promising technique that directly targets the seizure onset zone (SOZ) with continuous electrical stimulation. Prior retrospective analyses have shown reduced seizure frequencies and improved quality of life. Here, we investigate underlying neurophysiological changes induced by CSCS in order to gain an insight into the mechanism underlying the clinical effect of chronic electrical stimulation in focal epilepsy. We examined intracranial EEG data from seven patients with drug-resistant focal epilepsy and SOZs located in eloquent cortex who underwent continuous stimulation during their hospitalization. Subdural grid electrodes were implanted, and after the SOZ was localized to eloquent cortex, 2 Hz electrical stimulation was applied to contacts targeting the SOZ. Ninety minutes of intracranial EEG from a 4 × 4 electrode grid was analyzed before and during stimulation. Electrophysiological parameters were estimated for both pre-stimulation and stimulation data. Power spectrum and coherence of background activity was analysed together with spiking activity characteristics including spike rate, spike amplitude, and spike duration. Cortical stimulation resulted in a marked reduction of the amplitudes of background activity across all channel types for frequencies 5–40 Hz, particularly over SOZ electrodes. During cortical stimulation there was increased coherence between all electrodes and a decrease in spike rate, greatest over SOZ (p < 0.001). Spike-rate coherence was greatest within and between SOZ for pre-stimulation recordings and showed a significant decrease with cortical stimulation for electrodes near SOZ (p < 0.001). No such effect was seen for the other electrodes. Analysis of spike amplitudes showed that cortical stimulation resulted in a clear reduction of spikes over SOZ electrodes (p < 0.001) and only minor reductions for other electrodes (p < 0.001). Moreover, stimulation onset resulted in minor changes in the distribution of spike durations over all electrodes (p < 0.001). Spike-rate and power of background activity showed a significant correlation (p < 0.01). These results show changes in cortical electrophysiology during CSCS over the SOZ where reduction in interictal spikes is correlated with an attenuation of background activity. This suggests a possible causal relationship between background activity and interictal spikes and with seizure frequency rate. With an improved understanding of chronic electrical stimulation better stimulation paradigms might be developed for improved suppression of seizure frequency.

Multifunctional 3D electrode platform for real-time in situ monitoring and stimulation of cardiac tissues

Cardiovascular diseases are a major cause of death around the world underlining the importance of efficient treatments including novel medication. In vitro models of cardiac tissues are highly desired for monitoring electrophysiological response to screen pharmaceutical compounds at an early stage. Here, we report a platinum based 3D pillar electrode platform with cell growth guiding channel, which allows integrated, continuous electrical stimulation and recording of the cardiac tissues. This platform was successfully used to culture beating cardiomyocytes over weeks. The Pt-PDMS pillar electrode showed an impedance of 2.5 ± 0.3 kΩ at 10 Hz that is stable for using in cell cultures at 37 °C. Electrically pacing the cells improved maturation of the cardiac tissues. Contraction activities of 3D cardiac tissues were monitored in real-time through the pillar electrodes to evaluate physiological parameters. Adding 100 nM Isoproterenol clearly increased the spontaneous beating rate and decreased the extracellular field potential duration of the microtissues observed with electrical recording through the pillar electrodes. Overall, this platform has a potential to be applied in drug screening for in situ monitoring the biophysical parameters of the heart tissue in real-time.

Protective Effect of Moderate Exogenous Electric Field Stimulation on Activating Netrin-1/DCC Expression Against Mechanical Stretch-Induced Injury in Spinal Cord Neurons

Nerve cells detect and respond to electric field stimulation and extrinsic chemical guidance cues during development and regeneration; therefore, the development and optimization of an approach for functional neuronal regeneration are necessary for a nerve injury. In this study, we proposed using electric field stimulation to repair a nerve injury triggered by serious mechanical stretch loading. A device that provides continuous mechanical stretch and constant electric field stimulation was designed. Primary dissociated spinal cord neurons were stimulated by mechanical stretch (tensile strain 2.5-10%) at different times (1, 4, 8, and 12h) to set up a moderate nerve injury model. Stimulated samples were evaluated with respect to cell viability, density, and axonal elongation by the MTT and immunofluorescence assays. The results indicated that mechanical stretch (S, 5% tensile strain, 4h) caused moderate axonal injury, resulting in significant loss of cell viability and a decrease in cell density. However, injured spinal cord neurons became viable after electric field stimulation (E, 33mA/m2, 4h) in the fluorescein diacetate assay. In addition, neuronal viability, density, and elongation increased significantly after electric field stimulation compared with those of stretch-injured neurons. Moreover, electric field stimulation significantly activated the axonal guidance cues Netrin-1 and deleted in colorectal cancer (DCC) receptor expression compared with the stretch-injury group. These results indicate that electric stimulation activates synergistic guidance cues of expression to improve axonal growth relevant to nerve injuries. Our study provides new insight into neuronal regeneration.

Placement of Stimulating Epidural Catheter for a Patient With Large Scapular Sarcoma: A Case Report.

We report the use of continuous electrical stimulation to assist with the preoperative placement of a thoracic epidural which was used to provide postoperative analgesia in a patient undergoing excision of a large scapular sarcoma. The size of the sarcoma and the surrounding area required to maintain a sterile surgical field necessitated that the epidural catheter be inserted several vertebral interspaces caudal to the level of desired catheter tip termination. The use of electrical stimulation allowed for sequential intercostal muscle stimulation during threading, which enabled the placement of the catheter tip at the appropriate spinal level to optimize analgesia.

Immediate effect of Repetitive Facilitative Exercise combined with continuous electrical stimulation, vibratory stimulation on gait of care recipients in nursing home health care facilities.

Immediate effect of Repetitive Facilitative Exercise combined with continuous electrical stimulation, vibratory stimulation on gait of care recipients in nursing home health care facilities.

Intermittent Stimulation of the Nucleus Basalis of Meynert Improves Working Memory in Adult Monkeys

Dysfunction in the brain's cholinergic systems results in working memory and executive function impairments. The source of acetylcholine for the neocortex is the Nucleus Basalis of Meynert. We tested whether electrical activation of this nucleus would improve executive function in young adult monkeys. Continuous stimulation led to consistent performance impairments. In contrast, intermittent stimulation led to supranormal working memory performance. Optimal performance was achieved with delivery of 200 microsecond biphasic pulses at a frequency of 60 pulses per second, for 20 seconds every minute. Effects onset and offset within three minutes. Pharmacological experiments suggested both intermittent and continuous stimulation effects depended on cholinergic activation. Donepezil, a cholinesterase inhibitor, improved performance to supranormal levels in animals already impaired by continuous electrical stimulation. The same treatment did not impact performance while animals received intermittent stimulation. Administration of either nicotinic or muscarinic acetylcholine receptor antagonists prevented intermittent stimulation from altering performance. In the months after stimulation testing began, animal performance, measured in sessions without stimulation, improved. Over these months, the working memory delay at which animals achieved 80% correct performance increased three to fivefold. Our results show that cholinergic activation by deep brain stimulation enhances working memory performance and is a candidate treatment for losses in executive function in aging and Alzheimer's Disease.

Evaluation of an artifact reduction strategy for electrically evoked auditory steady-state responses: Simulations and measurements

BackgroundElectrically evoked steady-state response (EASSR) recording is a measure of neuronal response strength after continuous electrical stimulation of the auditory system. In order to suppress the large electrical artifact generated by intracochlear electrical stimulation, a sophisticated artifact reduction processing strategy (“Hofmann procedure”) has been proposed (Hofmann and Wouters, 2010). So far, EASSR recordings with artifact reduction procedures were reported only in cochlear implant (CI) users implanted with Cochlear devices (Macquarie, Australia). New methodHere, we demonstrate the application of the Hofmann procedure in CI users implanted with MED-EL (Innsbruck, Austria) devices. To demonstrate potential limitations of the procedure, we calculated discrete time Fourier transformations (DTFT) of various pulse patterns which may be used for EASSR. ResultsEASSR recordings were obtained in three subjects and processed with the Hofmann procedure. Neural response amplitude growth functions and phase for modulated and unmodulated pulse trains at various stimulation rates could be assessed. Simulations of three different interpolation methods aimed to suppress the electrical artifact show that the interpolation of a sinusoidal signal in a temporal window between 0 and 1 ms has demonstrated negligible impact on the spectral amplitude of the signal with a superior performance of a spline interpolation. Comparison with existing methodThe Hofmann procedure, initially developed for recording EASSRs with CIs from the manufacturer Cochlear, was validated for MED-EL devices. ConclusionIt is feasible to record EASSRs with the described measurement setup and CIs from the manufacturer MED-EL.

Adaptive Deep Brain Stimulation (aDBS) for Tourette Syndrome.

Deep brain stimulation (DBS) has emerged as a novel therapy for the treatment of several movement and neuropsychiatric disorders, and may also be suitable for the treatment of Tourette syndrome (TS). The main DBS targets used to date in patients with TS are located within the basal ganglia-thalamo-cortical circuit involved in the pathophysiology of this syndrome. They include the ventralis oralis/centromedian-parafascicular (Vo/CM-Pf) nucleus of the thalamus and the nucleus accumbens. Current DBS treatments deliver continuous electrical stimulation and are not designed to adapt to the patient’s symptoms, thereby contributing to unwanted side effects. Moreover, continuous DBS can lead to rapid battery depletion, which necessitates frequent battery replacement surgeries. Adaptive deep brain stimulation (aDBS), which is controlled based on neurophysiological biomarkers, is considered one of the most promising approaches to optimize clinical benefits and to limit the side effects of DBS. aDBS consists of a closed-loop system designed to measure and analyse a control variable reflecting the patient’s clinical condition and to modify on-line stimulation settings to improve treatment efficacy. Local field potentials (LFPs), which are sums of pre- and post-synaptic activity arising from large neuronal populations, directly recorded from electrodes implanted for DBS can theoretically represent a reliable correlate of clinical status in patients with TS. The well-established LFP-clinical correlations in patients with Parkinson’s disease reported in the last few years provide the rationale for developing and implementing new aDBS devices whose efficacies are under evaluation in humans. Only a few studies have investigated LFP activity recorded from DBS target structures and the relationship of this activity to clinical symptoms in TS. Here, we review the available literature supporting the feasibility of an LFP-based aDBS approach in patients with TS. In addition, to increase such knowledge, we report explorative findings regarding LFP data recently acquired and analysed in patients with TS after DBS electrode implantation at rest, during voluntary and involuntary movements (tics), and during ongoing DBS. Data available up to now suggest that patients with TS have oscillatory patterns specifically associated with the part of the brain they are recorded from, and thereby with clinical manifestations. The Vo/CM-Pf nucleus of the thalamus is involved in movement execution and the pathophysiology of TS. Moreover, the oscillatory patterns in TS are specifically modulated by DBS treatment, as reflected by improvements in TS symptoms. These findings suggest that LFPs recorded from DBS targets may be used to control new aDBS devices capable of adaptive stimulation responsive to the symptoms of TS.

Low-power transcutaneous current stimulator for wearable applications

BackgroundPeripheral neuropathic desensitization associated with aging, diabetes, alcoholism and HIV/AIDS, affects tens of millions of people worldwide, and there is little or no treatment available to improve sensory function. Recent studies that apply imperceptible continuous vibration or electrical stimulation have shown promise in improving sensitivity in both diseased and healthy participants. This class of interventions only has an effect during application, necessitating the design of a wearable device for everyday use. We present a circuit that allows for a low-power, low-cost and small form factor implementation of a current stimulator for the continuous application of subthreshold currents.ResultsThis circuit acts as a voltage-to-current converter and has been tested to drive + 1 to − 1 mA into a 60 kOmega load from DC to 1 kHz. Driving a 60 kOmega load with a 2 mA peak-to-peak 1 kHz sinusoid, the circuit draws less than 21 mA from a 9 V source. The minimum operating current of the circuit is less than 12 mA. Voltage compliance is ± 60 V with just 1.02 mA drawn by the high voltage current drive circuitry. The circuit was implemented as a compact 46 mm × 21 mm two-layer PCB highlighting its potential for use in a body-worn device.ConclusionsNo design to the best of our knowledge presents comparably low quiescent power with such high voltage compliance. This makes the design uniquely appropriate for low-power transcutaneous current stimulation in wearable applications. Further development of driving and instrumentation circuitry is recommended.

Intraoperative 1-Hour Electrical Nerve Stimulation Enhances Outcomes of Nerve-Muscle-Endplate Band Grafting Technique for Muscle Reinnervation.

Background Increasing evidence suggests that 1-hour electrical nerve stimulation during surgery improves nerve regeneration and functional recovery. However, it remains unknown if this approach has beneficial effects on the outcomes of our recently developed nerve–muscle-endplate band grafting-native motor zone (NMEG-NMZ) technique for muscle reinnervation. Methods In this study, NMEG-NMZ transplantation was performed in a rat model. The right sternomastoid muscle was experimentally denervated and immediately reinnervated by implanting a NMEG harvested from the ipsilateral sternohyoid (SH) muscle into the NMZ of the target muscle. Before implantation of the NMEG, the SH nerve branch innervating the NMEG was subjected to intraoperative 1-hour continuous electrical stimulation (20 Hz). Three months after surgery, the degree of functional recovery was evaluated with muscle force measurement and the extent of nerve regeneration and endplate reinnervation was examined using histological and immunohistochemical methods. Results A combination of NMEG-NMZ with electrical nerve stimulation resulted in a greater degree of functional recovery than the NMEG-NMZ alone. The mean muscle force of the treated muscles was 90% of the contralateral control. The muscle mass was recovered up to 90% of the control. The mean number and percentage of area of the regenerated axons in the treated muscles was computed to be 81 and 84% of the control muscles, respectively. On average, 83% of the denervated endplates in the treated muscles were reinnervated by regenerated axons. Conclusion Intraoperative brief nerve stimulation promotes nerve regeneration, endplate reinnervation, and functional recovery of the muscles reinnervated with NMEG-NMZ technique.

Deep brain stimulation and dystonia: About 10 new pediatric cases and a new DBS center in Paris

Objective: Deep Brain Stimulation (DBS) is a surgical technique used for dystonic patients during which a continuous electrical stimulation is delivered to the Globus Pallidum. Technical improvements render this procedure possible for young children. However, predictive factors for good responders remain poorly understood. We opened a new DBS pediatric center in 2015. We present our first results and the organization of our multidisciplinary care system. Methods: We report a series of 10 children seen in consultation for DBS during 2015–2016. In the absence of radiological or etiologic contraindications, the files are reviewed and the indications for implantation are validated in multidisciplinary consultation (neuropediatricians, neurologists, neurosurgeons, rehabilitation physicians). Once included, children are evaluated pre- and post-operatively by the “dystonia referents” team within the hospital (psychologist, physiotherapist, nurse, anesthetist, resuscitator, ENT, photographer for documentation of symptoms) conjointly with the neuropediatrician and neurosurgeon. Results: 5 children were implanted (2 DYT1 mutations, 1 PKAN, 1 severe dyskinetic dystonia, 1 generalized dystonia), 3 were finally excluded and 2 refused intervention. All implanted patients improved (video), between 30 to 95% (patient DYT1). The decreased dyskinesias has also uncovered learning abilities in the dyskinetic patient. Conclusion: DBS of the GPi has a well-known efficacy in DYT1, however recent studies as ours show that other primary or secondary dystonias may benefit as well from such interventions. Implantation in young children, however, poses a problem concerning the cumbersomeness long-term follow-up and need for regular re- interventions. The indications for implantation require in our opinion a multidisciplinary decision and to obtain the perfect adhesion of the family. A protocoled and rigorous follow-up of this population will improve both the selection criteria and suggest predictive parameters for better responders.

Chronic subthreshold cortical stimulation: a therapeutic and potentially restorative therapy for focal epilepsy

ABSTRACTIntroduction: Approximately one third of patients with focal epilepsy continue to have ongoing seizures despite adequate trials of anti-seizure medications. Surgery to remove the epileptogenic zone remains the most efficacious treatment option for focal drug-resistant epilepsy. However, when cortical areas are eloquent or there are multiple epileptogenic zones, surgical resection is not an ideal approach. Cortical stimulation provides an attractive alternative.Area covered: Here, the authors describe Chronic Subthreshold Cortical Stimulation (CSCS), which uses continuous intracranial electrical stimulation applied near the epileptogenic zone to lower seizure probability. The authors review literature related to CSCS. One challenge is finding the most efficacious set of stimulation parameters for each patient.Expert commentary: Data supporting CSCS are limited but promising for the treatment of patients with focal drug resistant epilepsy who are not surgical candidates. Additional electrophysiological biomarkers to estimate cortical excitability are needed.

Antiepileptic Drugs Impair Shortening of Isolated Cardiomyocytes.

Most antiepileptic drugs (AEDs) inhibit seizure generation by acting on voltage-dependent ion channels. Voltage-dependent sodium and calcium channels are commonly expressed in brain and heart, suggesting that AEDs may have considerable cardiodepressive effects, thereby facilitating sudden cardiac death as a potential cause of sudden unexpected death in epilepsy. Here, we investigated the effects of carbamazepine (CBZ), lamotrigine (LTG), and levetiracetam (LEV) alone and in combination on the shortening properties of isolated ventricular cardiomyocytes of wild-type mice. Properties of murine cardiomyocytes were determined by recording the sarcomere shortening with a video imaging system before, during, and after administration of AEDs in different concentrations and combinations. We assessed (i) the number of successful shortenings during continuous electrical stimulation (electromechanical coupling) and (ii) the shortening amplitude as well as other shortening-related properties upon repetitive electrical stimulation at 4 Hz. Data are given as mean ± SEM. At 100 μM, CBZ (10 cells), LTG (11 cells), and LEV (11 cells) alone had no effect on the electromechanical coupling but reversibly reduced shortening amplitudes by 15 ± 4, 24 ± 3, and 11 ± 3%, respectively. Increasing the LTG concentration to 250 (21 cells) and 500 μM (4 cells) reversibly inhibited the electromechanical coupling in 62 and 100% of the experiments. Importantly, simultaneous application of CBZ, LTG, and LEV at 100 μM also impaired the electromechanical coupling in 8 of 19 cardiomyocytes (42%) and reduced the shortening amplitude by 21 ± 4%. Our data show that AEDs reversibly impair cardiac excitation and contraction. Importantly, the blocking effect on electromechanical coupling appears to be additive when different AEDs are simultaneously applied. The translational value of these experimental findings into clinical practice is limited. Our results, however, suggest that rationale AED therapy may be important with respect to cardiac side effects and potential facilitation of serious cardiac dysfunction especially when AEDs are used in combination or at very high doses.

Recovery of supraspinal control of leg movement in a chronic complete flaccid paraplegic man after continuous low-frequency pelvic nerve stimulation and FES-assisted training.

More than 30 years ago, functional electrical stimulation (FES) was developed as an orthotic system to be used for rehabilitation for SCI patients. In the present case report, FES-assisted training was combined with continuous low-frequency stimulation of the pelvic somatic nerves in a SCI patient. We report on unexpected findings in a 41-year-old man with chronic complete flaccid paraplegia, since he was 18 years old, who underwent spinal stem cell therapy and a laparoscopic implantation of neuroprosthesis (LION procedure) in the pelvic lumbosacral nerves. The patient had complete flaccid sensomotoric paraplegia T12 as a result of a motor vehicle accident in 1998. In June 2011, he underwent a laparoscopic implantation of stimulation electrodes to the sciatic and femoral nerves for continuous low-frequency electrical stimulation and functional electrical stimulation of the pelvic nerves. Neither intraoperative direct stimulation of the pelvic nerves nor postoperative stimulation induced any sensation or muscle reactions. After 2 years of passive continuous low-frequency stimulation, the patient developed progressive recovery of electrically assisted voluntary motor functions below the lesions: he was first able to extend the right knee and 6 months later, the left. He is currently capable of voluntary weight-bearing standing and walking (with voluntary knee movements) about 50 m with open cuff crutches and drop foot braces. Our findings suggest that continuous low-frequency pelvic nerve stimulation in combination with FES-assisted training might induce changes that affect both the upper and the lower motor neuron and allow supra- and infra-spinal inputs to engage residual spinal and peripheral pathways.

Auditory steady state responses and cochlear implants: Modeling the artifact-response mixture in the perspective of denoising.

Auditory steady state responses (ASSRs) in cochlear implant (CI) patients are contaminated by the spread of a continuous CI electrical stimulation artifact. The aim of this work was to model the electrophysiological mixture of the CI artifact and the corresponding evoked potentials on scalp electrodes in order to evaluate the performance of denoising algorithms in eliminating the CI artifact in a controlled environment. The basis of the proposed computational framework is a neural mass model representing the nodes of the auditory pathways. Six main contributors to auditory evoked potentials from the cochlear level and up to the auditory cortex were taken into consideration. The simulated dynamics were then projected into a 3-layer realistic head model. 32-channel scalp recordings of the CI artifact-response were then generated by solving the electromagnetic forward problem. As an application, the framework’s simulated 32-channel datasets were used to compare the performance of 4 commonly used Independent Component Analysis (ICA) algorithms: infomax, extended infomax, jade and fastICA in eliminating the CI artifact. As expected, two major components were detectable in the simulated datasets, a low frequency component at the modulation frequency and a pulsatile high frequency component related to the stimulation frequency. The first can be attributed to the phase-locked ASSR and the second to the stimulation artifact. Among the ICA algorithms tested, simulations showed that infomax was the most efficient and reliable in denoising the CI artifact-response mixture. Denoising algorithms can induce undesirable deformation of the signal of interest in real CI patient recordings. The proposed framework is a valuable tool for evaluating these algorithms in a controllable environment ahead of experimental or clinical applications.

電気刺激と促通反復療法の併用効果

促通反復療法は，促通手技による意図した運動の実現とその集中反復により運動性下行路の再建，強化を目指した新たな運動療法で，主に軽度から中程度の片麻痺に対して良好な治療成績が得られている．一方，重度麻痺や痙縮などのために麻痺肢の随意性が低い場合，促通反復療法と他の治療法との併用療法が重要となる．われわれは低振幅の持続的低周波電気刺激と促通反復療法との同時併用，すなわち，わずかに筋収縮を生じる程度の神経筋電気刺激下に促通反復療法を行う方法を考案し，特に中重度の片麻痺に対して応用している．本法は患者の麻痺の程度や回復段階に応じて電気刺激強度を調整することで促通反復療法の適応を広げることが可能と考えられる．

Functional electrical stimulation to the abdominal wall muscles synchronized with the expiratory flow does not induce muscle fatigue.

[Purpose] Continuous electrical stimulation of abdominal wall muscles is known to induce mild muscle fatigue. However, it is not clear whether this is also true for functional electrical stimulation delivered only during the expiratory phase of breathing. This study aimed to examine whether or not intermittent electrical stimulation delivered to abdominal wall muscles induces muscle fatigue. [Subjects and Methods] The subjects were nine healthy adults. Abdominal electrical stimulation was applied for 1.5 seconds from the start of expiration and then turned off during inspiration. The electrodes were attached to both sides of the abdomen at the lower margin of the 12th rib. Abdominal electrical stimulation was delivered for 15 minutes with the subject in a seated position. Expiratory flow was measured during stimulus. Trunk flexor torque and electromyography activity were measured to evaluate abdominal muscle fatigue. [Results] The mean stimulation on/off ratio was 1:2.3. The declining rate of abdominal muscle torque was 61.1 ± 19.1% before stimulus and 56.5 ± 20.9% after stimulus, not significantly different. The declining rate of mean power frequency was 47.8 ± 11.7% before stimulus and 47.9 ± 10.2% after stimulus, not significantly different. [Conclusion] It was found that intermittent electrical stimulation to abdominal muscles synchronized with the expiratory would not induce muscle fatigue.

Vestibular control of standing balance is enhanced with increased cognitive load.

When cognitive load is elevated during a motor task, cortical inhibition and reaction time are increased; yet, standing balance control is often unchanged. This disconnect is likely explained by compensatory mechanisms within the balance system such as increased sensitivity of the vestibulomotor pathway. This study aimed to determine the effects of increased cognitive load on the vestibular control of standing balance. Participants stood blindfolded on a force plate with their head facing left and arms relaxed at their sides for two trials while exposed to continuous electrical vestibular stimulation (EVS). Participants either stood quietly or executed a cognitive task (double-digit arithmetic). Surface electromyography (EMG) and anterior-posterior ground-body forces (APF) were measured in order to evaluate vestibular-evoked balance responses in the frequency (coherence and gain) and time (cumulant density) domains. Total distance traveled for anterior-posterior center of pressure (COP) was assessed as a metric of balance variability. Despite similar distances traveled for COP, EVS-medial gastrocnemius (MG) EMG and EVS-APF coherence and EVS-TA EMG and EVS-MG EMG gain were elevated for multiple frequencies when standing with increased cognitive load. For the time domain, medium-latency peak amplitudes increased by 13-54% for EVS-APF and EVS-EMG relationships with the cognitive task compared to without. Peak short-latency amplitudes were unchanged. These results indicate that reliance on vestibular control of balance is enhanced when cognitive load is elevated. This augmented neural strategy may act to supplement divided cortical processing resources within the balance system and compensate for the acute neuromuscular modifications associated with increased cognitive demand.