Peripheral Electrical Stimulation Research Articles

Influence of sensory retraining on cortical reorganization in peripheral neuropathy: A systematic review.

This study systematically reviewed the literature about sensory retraining effect in comparison to other rehabilitative techniques on cortical reorganization in patients with peripheral neuropathic pain. TYPE: Systematic review. After performing an electronic search of PubMed, Web of Science, and Embase, risk of bias was assessed using the revised Cochrane risk of bias tool for randomized controlled trials and the risk of bias in non-randomized studies-of interventions for non-randomized studies of intervention. The strength of conclusion was determined using the evidence-based guideline development approach. Limited evidence indicates a higher increase in cortical inhibition and a higher reduction in cortical activation during a motor task of the affected hemisphere after graded motor imagery compared to wait-list. Higher reductions in map volume (total excitability of the cortical representation) of the affected hemisphere after peripheral electrical stimulation (PES) were observed when compared to transcranial direct current stimulation (tDCS) or to sham treatment with limited evidence. No other differences in cortical excitability and representation of the affected and non-affected hemisphere were observed when comparing mirror therapy with sham therapy or tDCS, PES with sham therapy or tDCS, and graded motor imagery with wait-list. Graded motor imagery and PES result in higher cortical excitability reductions of the affected hemisphere compared to wait-list, tDCS and sham treatment, respectively.

Continuous peripheral electrical nerve stimulation improves cardiac function via autonomic nerve regulation in MI rats

BackgroundPeripheral electrical nerve stimulation (PENS) reportedly improves cardiac function after myocardial ischemia (MI) by rebalancing the cardiac autonomic nervous system. The dynamic and continuous influence of PENS on autonomic and cardiac functioning based on cardiac self-repair is not well understood. ObjectivesThis study aimed to explore the relationship between autonomic nervous balance and functional cardiac repair after MI and to clarify the optimal acupoint selection and time course for PENS. MethodsThe activities of the superior cervical cardiac sympathetic nerve and vagus nerve were recorded to reflect the autonomic tone directly. The Millar pressure-volume loop system was used for left ventricular diastolic and systolic function. Noninvasive continuous electrocardiography and echocardiography were performed to analyze heart rate, heart rate variability, and left ventricular function. The effect of continuous PENS (cPENS) or instant PENS (iPENS) on autonomic and cardiac indications was tested. ResultsSympathetic nerve activity and vagus nerve activity increased as compensatory self-regulation on days 7 and 14 post-MI, followed by an imbalance of autonomic tone and cardiac dysfunction on day 28. cPENS-PC6 maintained autonomic hyperexcitability, improved myocardial systolic and diastolic abilities, and reduced myocardial fibrosis on day 28 post-MI, whereas cPENS-ST36 had a limited effect. Both iPENS-PC6 and iPENS-ST36 improved the autonomic and cardiac function of rats in the cPENS groups. ConclusionRats showed autonomic fluctuations and cardiac dysfunction 28 days post-MI. cPENS produced sympathomimetic action to sustain cardiac self-compensation, but with acupoint specificity. On the basis of cPENS, iPENS evoked autonomic regulation and cardiac benefits without acupoint differentiation.

Attentional state-synchronous peripheral electrical stimulation during action observation induced distinct modulation of corticospinal plasticity after stroke.

Brain computer interface-based action observation (BCI-AO) is a promising technique in detecting the user's cortical state of visual attention and providing feedback to assist rehabilitation. Peripheral nerve electrical stimulation (PES) is a conventional method used to enhance outcomes in upper extremity function by increasing activation in the motor cortex. In this study, we examined the effects of different pairings of peripheral nerve electrical stimulation (PES) during BCI-AO tasks and their impact on corticospinal plasticity. Our innovative BCI-AO interventions decoded user's attentive watching during task completion. This process involved providing rewarding visual cues while simultaneously activating afferent pathways through PES. Fifteen stroke patients were included in the analysis. All patients underwent a 15 min BCI-AO program under four different experimental conditions: BCI-AO without PES, BCI-AO with continuous PES, BCI-AO with triggered PES, and BCI-AO with reverse PES application. PES was applied at the ulnar nerve of the wrist at an intensity equivalent to 120% of the sensory threshold and a frequency of 50 Hz. The experiment was conducted randomly at least 3 days apart. To assess corticospinal and peripheral nerve excitability, we compared pre and post-task (post 0, post 20 min) parameters of motor evoked potential and F waves under the four conditions in the muscle of the affected hand. The findings indicated that corticospinal excitability in the affected hemisphere was higher when PES was synchronously applied with AO training, using BCI during a state of attentive watching. In contrast, there was no effect on corticospinal activation when PES was applied continuously or in the reverse manner. This paradigm promoted corticospinal plasticity for up to 20 min after task completion. Importantly, the effect was more evident in patients over 65 years of age. The results showed that task-driven corticospinal plasticity was higher when PES was applied synchronously with a highly attentive brain state during the action observation task, compared to continuous or asynchronous application. This study provides insight into how optimized BCI technologies dependent on brain state used in conjunction with other rehabilitation training could enhance treatment-induced neural plasticity.

Spinal cord electrical stimulation with neurophysiological monitoring for treatment of high-risk diabetic foot

To evaluate the clinical efficacy of a single-session implantation of spinal cord electrical stimulation with neurophysiological monitoring a spinal cord electrical stimulator under general anesthesia with neurophysiological monitoring for the treatment of high-risk diabetic foot. The clinical data of seven patients with high-risk diabetic foot who underwent spinal cord electrical stimulation in neurosurgery ward nine of Tianjin Huanhu Hospital from May 2022 to May 2023 were collected. The operation was performed under general anesthesia with the "C" arm X ray machine guidance and neurophysiological monitoring. The arterial diameter and peak flow rate of lower extremity, lower extremity skin temperature (calf skin temperature, foot skin temperature), visual analog scale (VAS), continuous distance of movement, blood glucose level and toe wound were compared between patients before and after surgery. A total of seven patients with high-risk diabetic foot were included. The diameters and peak flow rates of femoral artery, popliteal artery, anterior tibial artery, posterior tibial artery and dorsal foot artery in both lower limbs were significantly improved after surgery. All patients had different degrees of lower limb pain before operation. After operation, VAS score decreased significantly (1.1±0.9 vs. 6.8±3.4), the pain was significantly relieved, and the calf skin temperature and foot skin temperature were significantly higher than those before surgery [calf skin temperature (centigrade): 33.3±0.9 vs. 30.9±0.7, foot skin temperature (centigrade): 31.4±0.8 vs. 29.1±0.6], fasting blood glucose and postprandial blood glucose were significantly lower than those before surgery [fasting blood glucose (mmol/L): 7.6±1.4 vs. 10.5±1.2, postprandial blood glucose (mmol/L): 9.3±2.3 vs. 13.5±1.1], the differences were statistically significant (all P < 0.01). The lower limb movement of all seven patients was significantly improved after surgery, including one patient who needed wheelchair travel before surgery, and one patient who had intermittent claudication before surgery. Among them, one patient needed wheelchair travel and one patient had intermittent claudication before surgery. All patients could walk normally at 2 weeks after operation. Among the seven patients, two patients had the diabetic foot wound ulceration before surgery, which could not heal for a long time. One month after surgery, blood flow around the foot wound recovered and the healing was accelerated. The wound was dry and crusted around the wound, and the wound healed well. For diabetic high-risk foot patients who are intolerant to diabetic peripheral neuralgia and local anesthesia spinal cord electrical stimulation test, one-time implantation of spinal cord electrical stimulator under general anesthesia under neurophysiological monitoring can effectively alleviate peripheral neuralgia and other diabetic foot related symptoms, improve lower limb blood supply, and reduce the risk of toe amputation. Clinical practice has proved the effectiveness of this technique, especially for the early treatment of diabetic high-risk foot patients.

Long-interval afferent inhibition measurement using two different methods: Normative values, repeatability and reliability

BackgroundThe mechanism of Short-Latency Afferent Inhibition (SAI) is relatively well understood. In contrast, Long-Latency Afferent Inhibition (LAI) has not been as extensively studied as SAI, and its underlying mechanism remains unclear. Objective/HypothesisThis study had two primary objectives: first, to determine the optimal ISIs for LAI measured by amplitude changes (A-LAI) using high-resolution ISI ranges; and second, to compare measurements of LAI by threshold-tracking (T-LAI). MethodsTwenty-eight healthy volunteers (12 males aged 24- 45 years) participated in the study. Paired peripheral electrical and transcranial magnetic stimulation (TMS) stimuli (TS1mv) were applied at varying (ISIs)- 100, 200, 250, 300, 350, 400, 450, 500, 550, 600, 700, 800, 900, 1000 ms. ResultsBoth A-LAI and T-LAI showed that LAI decreased progressively from a peak at 200 or 250 ms to 1000 ms. Using the A-LAI method, pronounced inhibition was observed at three specific ISIs: 100 ms, 250 ms and 450 ms. When A-LAI values were converted to equivalent threshold changes, they did not differ significantly from T-LAI. Reliability at distinguishing individuals, as indicated by intraclass correlation coefficient (ICC) was greater for A-LAI, with a peak value of 0.82 at 250 ms. Conclusion(s)The study demonstrates that ISIs of 100 ms and 250 ms can be reliably used in amplitude measurement LAI. The study demonstrates that both LAI measurements record a similar decline of inhibition with increasing ISI.

A commentary on 'Efficacy of peripheral electrical nerve stimulation on improvements of urodynamics and voiding diary in patients with neurogenic lower urinary tract dysfunction: a systematic review and meta-analysis'.

A commentary on 'Efficacy of peripheral electrical nerve stimulation on improvements of urodynamics and voiding diary in patients with neurogenic lower urinary tract dysfunction: a systematic review and meta-analysis'.

Research advances in neuromodulation techniques for blood glucose regulation and diabetes intervention

Diabetes and its complications that seriously threaten the health and life of human, has become a public health problem of global concern. Glycemic control remains a major focus in the treatment and management of patients with diabetes. The traditional lifestyle interventions, drug therapies, and surgeries have benefited many patients with diabetes. However, due to problems such as poor patient compliance, drug side effects, and limited surgical indications, there are still patients who fail to effectively control their blood glucose levels. With the development of bioelectronic medicine, neuromodulation techniques have shown great potential in the field of glycemic control and diabetes intervention with its unique advantages. This paper mainly reviewed the research advances and latest achievements of neuromodulation technologies such as peripheral nerve electrical stimulation, ultrasound neuromodulation, and optogenetics in blood glucose regulation and diabetes intervention, analyzed the existing problems and presented prospects for the future development trend to promote clinical research and application of neuromodulation technologies in the treatment of diabetes.

Mapping the hotspots and future trends of electrical stimulation for peripheral nerve injury: A bibliometric analysis from 2002 to 2023.

Peripheral nerve injuries often result in severe personal and social burden, and even with surgical treatment, patients continue to have poor clinical outcomes. Over the past two decades, electrical stimulation has been shown to promote axonal regeneration and alleviate refractory neuropathic pain. The aim of this study was to analyse this field using a bibliometric approach. Literature was searched through Web of Science Core Collection (WOSCC) for the years 2002-2023. Literature analysis included: (1) Describing publication trends in the field. (2) Exploring collaborative network relationships. (3) Finding research advances and research hotspots in the field. (4) Summarizing research trends in the field. With the number of studies in this field still increasing, a total of 693 publications were included in the analysis. This field of research is interdisciplinary in nature. Research hotspots include peripheral nerve regeneration, the treatment of neuropathic pain, materials for nerve injury repair, and the restoration of sensory function in patients with peripheral nerve injury. Correspondingly, the development of nerve conduits and systems for peripheral nerve electrical stimulation, clinical trials of peripheral nerve electrical stimulation, and tactile recovery and movement for amputees have shown significant promise as future research trends in this field.

Repetitive sensorimotor mu-alpha phase-targeted afferent stimulation produces no phase-dependent plasticity related changes in somatosensory evoked potentials or sensory thresholds.

Phase-dependent plasticity has been proposed as a neurobiological mechanism by which oscillatory phase-amplitude cross-frequency coupling mediates memory process in the brain. Mimicking this mechanism, real-time EEG oscillatory phase-triggered transcranial magnetic stimulation (TMS) has successfully induced LTP-like changes in corticospinal excitability in the human motor cortex. Here we asked whether EEG phase-triggered afferent stimulation alone, if repetitively applied to the peaks, troughs, or random phases of the sensorimotor mu-alpha rhythm, would be sufficient to modulate the strength of thalamocortical synapses as assessed by changes in somatosensory evoked potential (SEP) N20 and P25 amplitudes and sensory thresholds (ST). Specifically, we applied 100 Hz triplets of peripheral electrical stimulation (PES) to the thumb, middle, and little finger of the right hand in pseudorandomized trials, with the afferent input from each finger repetitively and consistently arriving either during the cortical mu-alpha trough or peak or at random phases. No significant changes in SEP amplitudes or ST were observed across the phase-dependent PES intervention. We discuss potential limitations of the study and argue that suboptimal stimulation parameter choices rather than a general lack of phase-dependent plasticity in thalamocortical synapses are responsible for this null finding. Future studies should further explore the possibility of phase-dependent sensory stimulation.

Top-down and bottom-up stimulation techniques combined with action observation treatment in stroke rehabilitation: a perspective.

Stroke is a central nervous system disease that causes structural lesions and functional impairments of the brain, resulting in varying types, and degrees of dysfunction. The bimodal balance-recovery model (interhemispheric competition model and vicariation model) has been proposed as the mechanism of functional recovery after a stroke. We analyzed how combinations of motor observation treatment approaches, transcranial electrical (TES) or magnetic (TMS) stimulation and peripheral electrical (PES) or magnetic (PMS) stimulation techniques can be taken as accessorial physical therapy methods on symptom reduction of stroke patients. We suggest that top-down and bottom-up stimulation techniques combined with action observation treatment synergistically might develop into valuable physical therapy strategies in neurorehabilitation after stroke. We explored how TES or TMS intervention over the contralesional hemisphere or the lesioned hemisphere combined with PES or PMS of the paretic limbs during motor observation followed by action execution have super-additive effects to potentiate the effect of conventional treatment in stroke patients. The proposed paradigm could be an innovative and adjunctive approach to potentiate the effect of conventional rehabilitation treatment, especially for those patients with severe motor deficits.

Investigating the influence of functional electrical stimulation on motor imagery related μ-rhythm suppression.

Motor Imagery (MI) is a well-known cognitive technique that utilizes the same neural circuits as voluntary movements. Therefore, MI practice is widely used in sport training and post-stroke rehabilitation. The suppression of the μ-rhythm in electroencephalogram (EEG) is a conventional marker of sensorimotor cortical activation during motor imagery. However, the role of somatosensory afferentation in mental imagery processes is not yet clear. In this study, we investigated the impact of functional electrical stimulation (FES) on μ-rhythm suppression during motor imagery. Thirteen healthy experienced participants were asked to imagine their right hand grasping, while a 30-channel EEG was recorded. FES was used to influence sensorimotor activation during motor imagery of the same hand. We evaluated cortical activation by estimating the μ-rhythm suppression index, which was assessed in three experimental conditions: MI, MI + FES, and FES. Our findings shows that motor imagery enhanced by FES leads to a more prominent μ-rhythm suppression. Obtained results suggest a direct effect of peripheral electrical stimulation on cortical activation, especially when combined with motor imagery. This research sheds light on the potential benefits of integrating FES into motor imagery-based interventions to enhance cortical activation and holds promise for applications in neurorehabilitation.

Efficacy of peripheral electrical nerve stimulation on improvements of urodynamics and voiding diary in patients with neurogenic lower urinary tract dysfunction: a systematic review and meta-analysis.

Peripheral electrical nerve stimulation is a routinely recommended treatment for non-neurogenic overactive bladder but has not been approved for patients with neurogenic lower urinary tract dysfunction (NLUTD). This systematic review and meta-analysis was to elucidate the efficacy and safety of electrostimulation and thus provide firm evidence for treating NLUTD. We systematically performed the literature search through PubMed, Web of Science, and Cochrane Library databases in March 2022. The eligible studies were identified across the inclusion criteria and the data on urodynamic outcomes, voiding diary parameters, and safety was collected to quantitatively synthesize the pooled mean differences (MDs) with 95% CIs. Subgroup analyses and sensitivity analyses were subsequently used to investigate the possible heterogeneity. This report was achieved in accordance with the preferred reporting items for systematic reviews and meta-analyses statement. A total of 10 studies involving 464 subjects and 8 studies with 400 patients were included for systematic review and meta-analysis, respectively. The pooled effect estimates indicated that electrostimulation could significantly improve urodynamic outcomes, including maximum cystometric capacity (MD=55.72, 95% CI 15.73, 95.72), maximum flow rate (MD=4.71, 95% CI 1.78, 7.65), maximal detrusor pressure (MD=-10.59, 95% CI -11.45, -9.73), voided volume (MD=58.14, 95% CI 42.97, 73.31), and post-void residual (MD=-32.46, 95% CI -46.63, -18.29); for voiding diary parameters, patients undergoing electrostimulation showed lower MDs of incontinence episodes per 24h (MD=-2.45, 95% CI -4.69, -0.20) and overactive bladder symptom score (MD=-4.46, 95% CI -6.00, -2.91). In addition to surface redness and swelling, no stimulation-related severe adverse events were reported else. The current evidence demonstrated that peripheral electrical nerve stimulation might be effective and safe for managing NLUTD, whereas more reliable data from large-scale randomized controlled trials are necessary to strengthen this concept.

Attentional State-Dependent Peripheral Electrical Stimulation During Action Observation Enhances Cortical Activations in Stroke Patients.

Brain-computer interface (BCI) is a promising technique that enables patients' interaction with computers or machines by analyzing specific brain signal patterns and provides patients with brain state-dependent feedback to assist in their rehabilitation. Action observation (AO) and peripheral electrical stimulation (PES) are conventional methods used to enhance rehabilitation outcomes by promoting neural plasticity. In this study, we assessed the effects of attentional state-dependent feedback in the combined application of BCI-AO with PES on sensorimotor cortical activation in patients after stroke. Our approach involved showing the participants a video with repetitive grasping actions under four different tasks. A mu band suppression (8-13 Hz) corresponding to each task was computed. A topographical representation showed that mu suppression of the dominant (healthy) and affected hemispheres (stroke) gradually became prominent during the tasks. There were significant differences in mu suppression in the affected motor and frontal cortices of the stroke patients. The involvement of both frontal and motor cortices became prominent in the BCI-AO+triggered PES task, in which feedback was given to the patients according to their attentive watching. Our findings suggest that synchronous stimulation according to patient attention is important for neurorehabilitation of stroke patients, which can be achieved with the combination of BCI-AO feedback with PES. BCI-AO feedback combined with PES could be effective in facilitating sensorimotor cortical activation in the affected hemispheres of stroke patients.

Addition of tDCS and TENS to an education and exercise program in subjects with knee osteoarthritis: A study protocol.

Knee osteoarthritis often leads to chronic pain that frequently becomes disabling.Osteoarthritis has been linked to maladaptive plasticity in the brain, which can contribute to chronic pain. Therapies including neuromodulation and peripheral electrical stimulation are used to counteract the maladaptive plasticity of the brain. To determine the efficacy of the addition of tDCS and TENS to an education and exercise program in reducing pain. Over a 2-week study period, 60 participants will complete an exercise and educational intervention. Eligible participants accepting to participate will be subsequently randomized into one of the three treatment groups: 1) Active Transcranial Direct Current Stimulation (tDCS) and active Transcutaneous Electrical Nerve Stimulation (TENS); 2) Active tDCS and sham TENS; 3) Sham tDCS and sham TENS. The primary outcome will be subjective pain intensity. quality of life, physical function, central sensitization, and pain adjuvants (uncertainty, catastrophizing kinesiophobia, adverse events). This clinical trial will provide data on the effect that the addition of tDCS and/or TENS to an education and exercise program may have to counteract maladaptive plastic changes and improve the benefits of exercises, and whether the combination of both neuromodulator techniques may have a higher magnitude of effect.

The main non-invasive neuromodulatory techniques: an infographic

INTRODUCTION: This infographic aims to present the main non-invasive neuromodulatory techniques that can be used to assess and/or modulate central nervous system excitability. Single- and paired-pulse transcranial magnetic stimulation (TMS) can be used to assess brain excitability through the delivery of magnetic pulses over the cerebral cortex. The motor evoked potential is an indirect measure of motor cortex excitability and is the most used cortical measure of excitability. RESULTS: Neuromodulation may be achieved through several techniques, which may be used to promote top-down or bottom-up effects. Among the top-down techniques is direct current stimulation (DCS) which can change its nomenclature according to the stimulation target, for example, transcranial (tDCS), or cerebellar (ctDCS). In addition, also can be included in top-down techniques the transcranial random noise stimulation (tRNS), transcranial alternate current stimulation (tACS), and repetitive TMS (rTMS). On other hand, the bottom-up techniques include the peripheral electrical stimulation (PES), transcutaneous auricular vagus nerve stimulation (taVNS), transcutaneous spinal direct current stimulation (tsDCS), and repetitive peripheral magnetic stimulation (rPMS). CONCLUSION: The neuromodulatory effects are dependent on several parameters that can be specific to physical principles (electrical or magnetic). For example, in repetitive P/TMS the frequency, type and angular orientation of coil, distance between the coil and the brain, pulse waveform, and pattern of stimulation are presented as important parameters able to interfere with the quality of stimulation. The same can be observed in tDCS, ctDCS, and tsDCS with the polarity and shape and montage of electrode, intensity, site and duration of stimulation, and current density.

Effects of Paired Associative Stimulation on Cortical Plasticity in Agonist–Antagonist Muscle Representations

Paired associative stimulation (PAS) increases and decreases cortical excitability in primary motor cortex (M1) neurons, depending on the spike timing-dependent plasticity, i.e., long-term potentiation (LTP)- and long-term depression (LTD)-like plasticity, respectively. However, how PAS affects the cortical circuits for the agonist and antagonist muscles of M1 is unclear. Here, we investigated the changes in the LTP- and LTD-like plasticity for agonist and antagonist muscles during PAS: 200 pairs of 0.25-Hz peripheral electric stimulation of the right median nerve at the wrist, followed by a transcranial magnetic stimulation of the left M1 with an interstimulus interval of 25 ms (PAS-25 ms) and 10 ms (PAS-10 ms). The unconditioned motor evoked potential amplitudes of the agonist muscles were larger after PAS-25 ms than after PAS-10 ms, while those of the antagonist muscles were smaller after PAS-25 ms than after PAS-10 ms. The γ-aminobutyric acid A (GABAA)- and GABAB-mediated cortical inhibition for the agonist and antagonist muscles were higher after PAS-25 ms than after PAS-10 ms. The cortical excitability for the agonist and antagonist muscles reciprocally and topographically increased and decreased after PAS, respectively; however, GABAA and GABAB-mediated cortical inhibitory functions for the agonist and antagonist muscles were less topographically decreased after PAS-10 ms. Thus, PAS-25 ms and PAS-10 ms differentially affect the LTP- and LTD-like plasticity in agonist and antagonist muscles.

Pay attention to the clinical application of radiofrequency ablation in the treatment of neuropathic pain

Neuropathic pain is the pain triggered or caused by primary damage and dysfunction of the nervous system. Its pathogenesis is complex, involving changes in ion channel function, abnormal action potential generation and expansion, and central and peripheral sensitization. Therefore, it has always been the most intractable problem in clinical pain diagnosis and treatment, and there are many kinds of treatment methods. In addition to various oral drugs, nerve block, pulsed radiofrequency, radiofrequency ablation, central nerve electrical stimulation, peripheral nerve electrical stimulation, intra-thecal infusion system, craniotomy nerve decompression or carding, the dorsal root entry zone disfigurement, etc. various methods have mixed efficacy. So far, radiofrequency ablation of peripheral nerves is still the most simple and effective means for the treatment of neuropathic pain. In this paper, the definition, clinical manifestations, pathological mechanism and the treatment methods of radiofrequency ablation of neuropathic pain were expounded, in order to provide reference for related clinicians in radiofrequency ablation.

Multimodal integration and modulation of visual and somatosensory inputs on the corticospinal excitability

ObjectiveCorticospinal excitability may be affected by various sensory inputs under physiological conditions. In this study, we aimed to investigate the corticospinal excitability by using multimodal conditioning paradigms of combined somatosensory electrical and visual stimulation to understand the sensory-motor integration. MethodsWe examined motor evoked potentials (MEP) obtained by using transcranial magnetic stimulation (TMS) that were conditioned by using a single goggle–light-emitting diode (LED) stimulation, peripheral nerve electrical stimulation (short latency afferent inhibition protocol), or a combination of both (goggle-LED+electrical stimulation) at different interstimulus intervals (ISIs) in 14 healthy volunteers. ResultsWe found MEP inhibition at ISIs of 50–60 ms using the conditioned goggle-LED stimulation. The combined goggle-LED stimulation at a 60 ms ISI resulted in an additional inhibition to the electrical stimulation. ConclusionsVisual inputs cause significant modulatory effects on the corticospinal excitability. Combined visual and somatosensory stimuli integrate probably via different neural circuits and/or interneuron populations. To our knowledge, multimodal integration of visual and somatosensory inputs by using TMS-short latency inhibition protocol have been evaluated via electrophysiological methods for the first time in this study.

Modulation of spinal circuits following phase-dependent electrical stimulation of afferent pathways

Objective. Peripheral electrical stimulation (PES) of afferent pathways is a tool commonly used to induce neural adaptations in some neural disorders such as pathological tremor or stroke. However, the neuromodulatory effects of stimulation interventions synchronized with physiological activity (closed-loop strategies) have been scarcely researched in the upper-limb. Here, the short-term spinal effects of a 20-minute stimulation protocol where afferent pathways were stimulated with a closed-loop strategy named selective and adaptive timely stimulation (SATS) were explored in 11 healthy subjects. Approach. SATS was applied to the radial nerve in-phase (INP) or out-of-phase (OOP) with respect to the muscle activity of the extensor carpi radialis (ECR). The neural adaptations at the spinal cord level were assessed for the flexor carpi radialis (FCR) by measuring disynaptic Group I inhibition, Ia presynaptic inhibition, Ib facilitation from the H-reflex and estimation of the neural drive before, immediately after, and 30 minutes after the intervention. Main results. SATS strategy delivered electrical stimulation synchronized with the real-time muscle activity measured, with an average delay of 17 ± 8 ms. SATS-INP induced increased disynaptic Group I inhibition (77 ± 23% of baseline conditioned FCR H-reflex), while SATS-OOP elicited the opposite effect (125 ± 46% of baseline conditioned FCR H-reflex). Some of the subjects maintained the changes after 30 minutes. No other significant changes were found for the rest of measurements. Significance. These results suggest that the short-term modulatory effects of phase-dependent PES occur at specific targeted spinal pathways for the wrist muscles in healthy individuals. Importantly, timely recruitment of afferent pathways synchronized with specific muscle activity is a fundamental principle that shall be considered when tailoring PES protocols to modulate specific neural circuits. (NCT number 04501133).

Classification of Kinematic and Electromyographic Signals Associated with Pathological Tremor Using Machine and Deep Learning

Peripheral Electrical Stimulation (PES) of afferent pathways has received increased interest as a solution to reduce pathological tremors with minimal side effects. Closed-loop PES systems might present some advantages in reducing tremors, but further developments are required in order to reliably detect pathological tremors to accurately enable the stimulation only if a tremor is present. This study explores different machine learning (K-Nearest Neighbors, Random Forest and Support Vector Machines) and deep learning (Long Short-Term Memory neural networks) models in order to provide a binary (Tremor; No Tremor) classification of kinematic (angle displacement) and electromyography (EMG) signals recorded from patients diagnosed with essential tremors and healthy subjects. Three types of signal sequences without any feature extraction were used as inputs for the classifiers: kinematics (wrist flexion-extension angle), raw EMG and EMG envelopes from wrist flexor and extensor muscles. All the models showed high classification scores (Tremor vs. No Tremor) for the different input data modalities, ranging from 0.8 to 0.99 for the f1 score. The LSTM models achieved 0.98 f1 scores for the classification of raw EMG signals, showing high potential to detect tremors without any processed features or preliminary information. These models may be explored in real-time closed-loop PES strategies to detect tremors and enable stimulation with minimal signal processing steps.