Stimulating Electrodes Research Articles

Effect of electrode attachment location for transcutaneous electrical nerve stimulation for pain relief in lumbar vertebral body fractures.

[Purpose] This study aimed to investigate the effect of the location of electrode attachment in transcutaneous electrical nerve stimulation on pain relief in patients with lumbar vertebral body fractures. [Participants and Methods] This study included 59 patients with lumbar vertebral body fractures, who were randomly assigned to receive transcutaneous electrical nerve stimulation to the lumbar region, lower limbs, or upper limbs, or no treatment, over a 4-week period. Pain, activities of daily living, and pain catastrophizing were assessed. [Results] Compared with the control group, transcutaneous electrical nerve stimulation to the lumbar region or lower limbs significantly reduced pain levels in the first 2 weeks. Although, activities of daily living and pain catastrophizing improved over time, no significant differences were observed between the groups. [Conclusion] Transcutaneous electrical nerve stimulation provides pain relief to patients during the early stages of lumbar vertebral body fractures. However, it had no effect on the activities of daily living, pain catastrophizing, or long-term pain-relief. For lumbar vertebral body fracture pain relief, transcutaneous electrical nerve stimulation electrodes should be attached to the lumbar region or lower limbs.

Directionally non-rotating electric field therapy delivered through implanted electrodes as a glioblastoma treatment platform: A proof-of-principle study.

While directionally rotating tumor-treating fields (TTF) therapy has garnered considerable clinical interest in recent years, there has been comparatively less focus on directionally non-rotating electric field therapy (dnEFT). We explored dnEFT generated through customized electrodes as a glioblastoma therapy in in vitro and in vivo preclinical models. The effects of dnEFT on tumor apoptosis and microglia/macrophages in the tumor microenvironment were tested using flow-cytometric and qPCR assays. In vitro, dnEFT generated using a clinical-grade spinal cord stimulator showed antineoplastic activity against independent glioblastoma cell lines. In support of the results obtained using the clinical-grade electrode, dnEFT delivered through a customized, 2-electrode array induced glioblastoma apoptosis. To characterize this effect in vivo, a custom-designed 4-electrode array was fabricated such that tumor cells can be implanted into murine cerebrum through a center channel equidistant from the electrodes. After implantation with this array and luciferase-expressing murine GL261 glioblastoma cells, mice were randomized to dnEFT or placebo. Relative to placebo-treated mice, dnEFT reduced tumor growth (measured by bioluminescence) and prolonged survival (median survival gain of 6.5 days). Analysis of brain sections following dnEFT showed a notable increase in the accumulation of peritumoral macrophage/microglia with increased expression of M1 genes (IFNγ, TNFα, and IL-6) and decreased expression of M2 genes (CD206, Arg, and IL-10) relative to placebo-treated tumors. Our results suggest therapeutic potential in glioblastoma for dnEFT delivered through implanted electrodes, supporting the development of a proof-of-principle clinical trial using commercially available deep brain stimulator electrodes.

A workflow for predicting radiofrequency-induced heating around bilateral deep brain stimulation electrodes in MRI.

Heating around deep brain stimulation (DBS) in magnetic resonance imaging (MRI) occurs when the time-varying electromagnetic (EM) fields induce currents in the electrodes which can generate heat and potentially cause tissue damage. Predicting the heating around the electrode contacts is important to ensure the safety of patients with DBS implants undergoing an MRI scan. We previously proposed a workflow to predict heating around DBS contacts and introduced a parameter, equivalent transimpedance, that is independent of electrode trajectories, termination, and radiofrequency (RF) excitations. The workflow performance was validated in a unilateral DBS system. To predict RF heating around the contacts of bilateral (DBS) electrodes during an MRI scan in an anthropomorphic head phantom. Bilateral electrodes were fixed in a skull phantom filled with hydroxyethyl cellulose (HEC) gel. The electrode shafts were suspended extracranially, in a head and torso phantom filled with the same gel material. The current induced on the electrode shaft was experimentally measured using an MR-based technique 3cm above the tip. A transimpedance value determined in a previous offline calibration was used to scale the shaft current and calculate the contact voltage. The voltage was assigned as a boundary condition on the electrical contacts of the electrode in a quasi-static (EM) simulation. The resulting specific absorption rate (SAR) distribution became the input for a transient thermal simulation and was used to predict the heating around the contacts. RF heating experiments were performed for eight different lead trajectories using circularly polarized (CP) excitation and two linear excitations for one trajectory. The measured temperatures for all experiments were compared with the simulated temperatures and the root-mean-squared errors (RMSE) were calculated. The RF heating around the contacts of both bilateral electrodes was predicted with ≤ 0.29°C of RMSE for 20 heating scenarios. The workflow successfully predicted the heating for different bilateral DBS trajectories and excitation patterns in an anthropomorphic head phantom.

The impact of spinal cord stimulation on a chronic model of atrial fibrillation in a mini-pig experiment

Introduction: Despite the advancement interventional methods for treating atrial fibrillation, the effectiveness of catheter ablation remains poor, especially in patients with persistent and long-persistent atrial fibrillation. Thus, experts continue to explore new treatments for this arrhythmia. The issue of experimental studies investigating the association between spinal cord stimulation and atrial fibrillation is mainly attributed to the lack of optimal algorithms for spinal cord stimulation in animal experiments. Therefore, it is important to develop adequate algorithms for spinal cord stimulation in the chronic model of atrial fibrillation.Objective: To evaluate the impact of spinal cord stimulation on the model of atrial fibrillation in mini-pigs.Methods: In a series of experiments, 6 (100%) successful implantations of electrodes and pacemakers, and spinal cord stimulation electrodes were performed. The electrodes were used to stimulate the atria, creating a model of atrial fibrillation, while the spinal cord stimulation was carried out using an electrode implanted into the spinal canal. During the experiment, an electrophysiological study was performed using an implanted pacemaker. The inducibility of atrial fibrillation was assessed before and after the experiment using various spinal cord stimulation algorithms.Results: There were no complications associated with surgery or stimulation of the atria and spinal cord. Spinal stimulation had a modeling effect on the autonomic nervous system, significantly changing the average heart rate, Wenckebach point, and effective refractory period. When comparing spinal stimulation algorithms, algorithm 1 was found to significantly reduce the atrial fibrillation inducibility.Conclusion: Spinal cord stimulation had a modeling effect on the autonomic nervous system, significantly changing the average heart rate, Wenckebach point, and effective refractory period. Inducibility of atrial fibrillation decreases with changes in the spinal pacing algorithm. Received 15 September 2023. Revised 30 October 2023. Accepted 31 October 2023. Funding: The study was supported by Russian Science Foundation (project No. 22-25-00672). Conflict of interest: The authors declare no conflict of interest. Contribution of the authorsConception and study design: A.G. Filippenko, V.V. Shabanov, V.I. MurtazinData collection and analysis: A.G. Filippenko, T.U. Khalkhoghaev, V.V. BeloborodovStatistical analysis: A.G. Filippenko, V.V. ShabanovDrafting the article: A.G. Filippenko, V.V. BeloborodovCritical revision of the article: V.V. ShabanovFinal approval of the version to be published: V.V. Shabanov, A.G. Filippenko, V.V. Beloborodov, T.U. Khalkhoghaev, V.I. Murtazin

Transcranial Magnetic and Transcutaneous Spinal Cord Electrical Stimulation a Stroke-Patients Walking Correction: Blinded Clinical Randomised Study

INTRODUCTION. The impairment of motor system function due to stroke often leads to patients’ dependence on external assistance. The technique of rhythmic transcranial magnetic stimulation (rTMS) is now widely used in the restoration of impaired central nervous system (CNS) function. In recent years, there has been information about the use of transcutaneous electrical spinal cord stimulation (TSCS) in the correction of motor functions in CNS disorders of various genesis.
 AIM. To evaluate the possibilities of combined use of transcranial magnetic and transcutaneous electrical stimulation of the spinal cord in the correction of locomotor functions in patients after ischemic stroke.
 MATERIALS AND METHODS. The conducted blind clinical randomized study involved patients who had an ischemic stroke. Study participants were randomly divided into control (n = 12) and experimental (n = 9) groups. Patients in the control group received standardized neurorehabilitation techniques. The participants of the experimental group were offered standardized neurorehabilitation techniques combined with rTMS and TSCS. High-frequency rTMS was performed in the projection of the sensory-motor cortex on the side of the lesion, in the area of innervation of the lower limb. During TSCS, a stimulating electrode was placed between Th11–Th12, indifferent electrodes were placed in the region of the iliac crests, and the lumbar enlargement of the spinal cord was stimulated. The dynamics of neurological deficit was assessed using the rehabilitation routing scale, the Rivermead mobility index, the Berg balance scale, and a six-point scale for assessing muscle strength. The excitability of the neural networks of the spinal cord was determined using TSCS at the T11–T12 level, with electromyographic recording of the evoked motor responses of the muscles of the lower extremities.
 RESULTS AND DISCUSSION. The combined use of rTMS and TSCS in the rehabilitation of patients in the acute period after ischemic stroke leads to an increase in the excitability of neuronal networks of the lumbar thickening of the spinal cord, a decrease in the activation thresholds of the RF, BF, TA and GM muscles of the affected limb (by 7.7 ma, 18.3 ma, 24.8 ma and 14.2 ma, respectively). Inclusion of rTMS and TSCS in the rehabilitation course leads to a significant improvement in the rehabilitation routing scale (by 2 points), Rivermead mobility index (by 5.8 points), statokinetic control functions (balance-Berg by 12 points) and an increase in lower limb muscle strength (flexors by 5.1 points, extensors by 6.2 points).
 CONCLUSION. The use of rTMS and TSCS can be used as an additional effect within the framework of rehabilitation measures in the acute period after ischemic stroke.

Efficacy of Transcranial Direct Current Stimulation on Pain Level and Disability of Patients with Fibromyalgia: A Systematic Review of Randomized Controlled Trials with Parallel-Group Design.

Transcranial direct current stimulation (tDCS) has been increasingly applied in fibromyalgia (FM) to reduce pain and fatigue. While results are promising, observed effects are variable, and there are questions about optimal stimulation parameters such as target region (e.g., motor vs. prefrontal cortices). This systematic review aimed to provide the latest update on published randomized controlled trials with a parallel-group design to examine the specific effects of active tDCS in reducing pain and disability in FM patients. Using the PRISMA approach, a literature search identified 14 randomized controlled trials investigating the effects of tDCS on pain and fatigue in patients with FM. Assessment of biases shows an overall low-to-moderate risk of bias. tDCS was found effective in all included studies conducted in patients with FM, except one study, in which the improving effects of tDCS were due to placebo. We recommended tDCS over the motor and prefrontal cortices as "effective" and "probably effective" respectively, and also safe for reducing pain perception and fatigue in patients with FM, according to evidence-based guidelines. Stimulation polarity was anodal in all studies, and one single-session study also examined cathodal polarity. The stimulation intensity ranged from 1-mA (7.14% of studies) to 1.5-mA (7.14% of studies) and 2-mA (85.7% of studies). In all of the included studies, a significant improvement in at least one outcome variable (pain or fatigue reduction) was observed. Moreover, 92.8% (13 of 14) applied multi-session tDCS protocols in FM treatment and reported significant improvement in their outcome variables. While tDCS is therapeutically effective for FM, titration studies that systematically evaluate different stimulation intensities, durations, and electrode placement are needed.

Continuous intraoperative neuromonitoring of the facial nerve predicts postoperative facial palsy in parotid surgery: a prospective study.

Facial palsy (FP) is the most significant complication of parotidectomy. Currently, the use of intermittent intraoperative neuromonitoring (iIONM) in parotid surgery facilitates nerve detection, which is paramount to nerve protection. Continuous IONM (cIONM), as applied in thyroid surgery, enables real-time information on electrophysiological nerve status through continuous nerve stimulation, thereby allowing consequent amplitude analysis. To date, the application of cIONM in parotid surgery has not been noted in literature. We performed parotidectomies with anterograde facial nerve visualization using cIONM in 32 consecutive patients in a prospective study (German Register of clinical studies-DRKS 00011051) during the period October 2016 to January 2020. After the facial trunk had been exposed, an atraumatic stimulation electrode was placed and the nerve was stimulated at 3Hz, at a low threshold (0.62 ± 0.06mA), for the entire duration of the preparation. Selected electrophysiological parameters were collected and compared to postoperative facial nerve function, measured by the House-Brackmann grading system. In the post hoc analysis, a significant correlation between a drop in amplitude (< 50% of the "baseline" amplitude) and postoperative FP was recorded (p = 0.001). True positive prediction of FP was noted in 14 out of 16 patients and true negative in 10 out of 16. The sensitivity was 87.5% (AUC 0.75), with a high negative predictive value of 83.3%. cIONM has significant value in predicting postoperative FP in parotidectomy. Future development of an acoustic/optic warning system in IONM devices could prevent nerve injury in real time.

Could transcranial direct-current stimulation in the insular cortex increase exercise tolerance in patients with heart failure?

Although studies have shown that transcranial direct-current stimulation (tDCS) can improve physical performance, reduce fatigue, modulate the cardiac autonomic nervous system and increase tolerance to exercise by decreasing the rating of perceived exertion in healthy subjects, athletes, and non-athletes, it has not been examined in patients that have suffered from heart failure (HF). Despite the established benefits of physical exercise, our study investigates whether anodal electrode (a-tDCS) stimulation in the insular cortex, combined with aerobic exercise, enhances physical performance. We aim to assess its impact on inflammatory cytokines, subclinical parameters in cardiopulmonary tests, and quality of life in HFrEF patients compared to sham stimulations. To our knowledge, there are no reports in the literature of studies that have analyzed the effects of a-tDCS applied to the insular area on aerobic performance in patients with HFrEF; thus, our objective is unique and can have a great impact on cardiac rehabilitation. On the other hand, the hypothesis presented here should be approached with caution since there is a lack of clinical trials on this topic.

Neural activity of the subthalamic nucleus during voluntary movements in patients with Parkinson’s disease

Microelectrode recording (MER) during electrode implantation for deep brain stimulation (DBS) can determine the boundaries of the subthalamic nucleus (STN), and track neural activity during rest and voluntary movement in Parkinson’s disease (PD) patients. However, the functional role of STN in motor control remains unclear, despite its effectiveness in stimulation. Single unit activity of STN was recorded in 16 patients with PD during implantation of deep brain stimulation electrodes. Electromyograms of forearm muscles and a phonogram featuring verbal commands were simultaneously recorded with MER. The patients were instructed to perform motor tests involving clenching their hand into a fist. Out of the 560 neurons studied, 93 (16.6%) responded to motor tasks. The registered neurons were classified into three patterns using the hierarchical clustering method of histograms of interspike interval density — namely, tonic, burst, and pause patterns. Sensitive neurons were classified according to their responses, with activation (76.9%) and inhibition (23.1%) being the two identified types. In 90% of cases, neuron activation preceded movement. Of the responses, 53.8% were classified as tonic and 46.2% as phasic. Two thirds of inhibitory responses were advanced, occurring 0.2–0.3 seconds before movement onset. One third of neurons were activated after movement initiation with a delay of 0.05–0.2 seconds. 83.3% of the inhibitory neurons responded tonically, while the remaining 16.7% responded phasically. Notably, all phasic reactions occurred before the onset of movement. A comparison of the parameters of sensitive and non-sensitive neurons revealed several differences. The findings suggest a potential physiological distinction between the two neuron types. All three patterns of activity were present in both types of neurons, but sensitive neurons exhibited a wider representation of pause neurons (57.9% vs. 49.5%). Additionally, burst and pause neurons responded to movements that featured significantly lower variance of multiple activity parameters, such as firing rate, burst index, mean burst length, and oscillation scores in the 8–12 and 12–20 Hz range. The distribution of sensitive neurons along the electrode trajectory through the subthalamic nucleus was analyzed. Sensitive neurons were located significantly more dorsally compared to non-sensitive neurons, and no sensitive pause cells were observed in the ventral half of the STN. Based on our findings, it is presumed that the pause pattern plays a critical role in both motor control and its related disorders in Parkinson’s disease. A diverse range of neuronal responses suggests a high degree of heterogeneity among STN neurons implicated in motor control. The presence of both delayed and advanced neural responses suggests that STN involvement in motor control encompasses both the preparation and initiation of movement, as well as the regulation of ongoing movements via afferent feedback. The range of neural responses aligns with the dynamic model of basal ganglia, which suggests that STN can perform distinct functional roles during different stages of movement, including initiation, control, and completion.

Multifractal characteristics of neuronal activity of the &lt;i&gt; globus pallidus &lt;/i&gt; in patients with dystonia

Dystonia is a movement disorder characterized by involuntary muscle contractions resulting in anomalous postures, often accompanied by dystonic tremors. Among the indicative dystonic postures is an involuntary tonic tilt or rotation of the head. Currently, the etiology and pathogenesis of the disease remain theories. Currently, only low-frequency (theta-alpha) oscillations in the globus pallidus are regarded as the possible biomarker of pathological activity in dystonia. In many patients with dystonia, the absence of rhythmic neuronal activity in the basal ganglia renders this biomarker unusable for surgical treatment of the disease. Additionally, the mechanisms underlying the rearrangement of temporary patterns of neural activity that result in pathological symptoms remain unclear. We propose that the appearance of these pathological rhythms is associated with the reduction of dynamic complexity in the pattern of neural activity within the globus pallidus. We aim to use multifractal analysis in this study to evaluate changes in the globus pallidus neural activity pattern’s dynamic complexity and their correlation with the clinical manifestations of dystonia. The study examined the electrical activity of the globus pallidus in 23 patients receiving deep brain stimulation (DBS) treatment. We used the microelectrode registration technique and local field potential (LFP) registration during intraoperative neuron monitoring to precisely identify the specific locations of the external and internal segments of the globus pallidus (GPe and GPi). In four patients, an additional postoperative recording of local field potentials (LFP) was conducted while performing DBS and vibrational impact on the neck muscles. A neurologist evaluated the patients to determine the severity of the disease using the Burke-Fahn-Mardsen Dystonia Rating Scale (BFMDRS). The LEAD DBS software package was employed for postoperative reconstruction of the DBS stimulating electrode positions and for simulating the optimal stimulation zone, selected by the neurologist (i.e., volume of tissue activated, VTA). Subsequently, we identified the region that presented the most significant variation in multifractal spectrum parameters following DBS to understand its correlation with the optimal VTA. A total of 745 local potential records were analyzed, with 433 in GPe and 312 in GPi. The severity of dystonia was found to be correlated with the parameters of the multifractal spectrum (rho: –0.5630882, p=0.005149 for GPe and rho: –0.5180609, p=0.01133 for GPi). Moreover, as the dystonia severity increased along the BFMDRS scale, the multifractal spectrum became narrower and more asymmetric. In post-surgery recordings, we observed changes in the shape of the multifractal spectrum during DBS stimulation or vibration. In particular, when exposed, the multifractal spectrum significantly widened, and its symmetry was restored. We identified the region with the greatest alteration in the width of the multifractal spectrum following DBS and discovered that this region considerably intersected or fully matched the neurologist’s chosen zone for optimal DBS stimulation. We demonstrated that multifractal analysis can serve as an ancillary approach to evaluate the extent of proprioceptive feedback impairment and as a biomarker of dystonia. The noteworthy and substantial correlation with dystonia severity underscores the considerable potential of multifractal spectrum features as a biomarker of dystonia. Additionally, the overlapping areas with the most significant DBS impact and the widest variation in the multifractal spectrum in DBS can be used as a tool for identifying the most favorable region for DBS stimulation.

Electrochemical Performance of Biocompatible TiC Films Deposited through Nonreactive RF Magnetron Sputtering for Neural Interfacing.

The efficacy of neural electrode stimulation and recording hinges significantly on the choice of a neural electrode interface material. Transition metal carbides (TMCs), particularly titanium carbide (TiC), have demonstrated exceptional chemical stability and high electrical conductivity. Yet, the fabrication of TiC thin films and their potential application as neural electrode interfaces remains relatively unexplored. Herein, we present a systematic examination of TiC thin films synthesized through nonreactive radio frequency (RF) magnetron sputtering. TiC films were optimized toward high areal capacitance, low impedance, and stable electrochemical cyclability. We varied the RF power and deposition pressure to pinpoint the optimal properties, focusing on the deposition rate, surface roughness, crystallinity, and elemental composition to achieve high areal capacitance and low impedance. The best-performing TiC film showed an areal capacitance of 475 μF/cm2 with a capacitance retention of 93% after 5000 cycles. In addition, the electrochemical performance of the optimum film under varying scanning rates demonstrated a stable electrochemical performance even under dynamic and fast-changing stimulation conditions. Furthermore, the in vitro cell culture for 3 weeks revealed excellent biocompatibility, promoting cell growth compared with a control substrate. This work presents a novel contribution, highlighting the potential of sputtered TiC thin films as robust neural electrode interface materials.

Frameless and fiducial-less, O-arm assisted navigation for deep brain stimulation placement using the Nexframe®. A technical note

O-arm® assisted navigation for placement of deep brain stimulation (DBS) electrodes using the Nexframe® device is a relatively new method that has been in use at many centers in the United States. However, no reports have described this operative technique in detail. In this technical report we describe the surgical nuances of this method in a stepwise approach. We also review and discuss the accuracy of this method in comparison to other methods of placing DBS electrodes.

Review of the targeting accuracy of frameless and frame-based robot-assisted deep brain stimulation electrode implantation in pediatric patients using the Neurolocate module.

The Neurolocate module is a 3D frameless patient registration module that is designed for use with the Neuromate stereotactic robot. Long-term electrical stimulation of the globus pallidus internus (GPi) and subthalamic nucleus (STN) via deep brain electrode implantation is particularly successful in a select group of movement disorders in pediatric patients. This study aimed to review the targeting accuracy of deep brain stimulation (DBS) electrode implantation in a single center, comparing standard frame-based techniques to the frameless Neurolocate module. Twenty-four pediatric patients underwent implantation of bilateral DBS electrodes under general anesthesia during the period of August 2018-August 2022. All patients underwent robot-assisted stereotactic implantation of DBS electrodes using an intraoperative O-arm 3D scanner to confirm the final electrode position. These coordinates were compared with the planned entry and target, with attention to depth, radial, directional, and absolute errors, in addition to Euclidean distance (ED). The primary outcome evaluated the accuracy and safety of the Neurolocate frameless technology compared with standard frame-based techniques. Of the 24 bilateral DBS electrode implantations performed, 62.5% used Neurolocate technology: 87.5% were delivered to the GPi and the remaining 12.5% to the STN. The mean patient age was 11.0 (range 4-18) years and 70.8% were male. The median absolute errors in x-, y-, and z-axes were 0.35, 0.75, and 0.9 mm, respectively, using the Neurolocate module compared with 0.30, 0.95, and 1.1 mm using the standard frame-based technique. The median ED from the planned target to the actual electrode position with the Neurolocate module was 1.28 mm versus 1.69 mm using standard frame-based techniques. No major perioperative complications occurred. Stereotactic robot-assisted DBS implantation with the frameless Neurolocate module is safe for use in the pediatric population, showing good surgical accuracy and no inferiority to standard frame-based techniques. The Neurolocate module for robotic DBS surgery has the potential to improve surgical targeting accuracy, surgical time, patient comfort, and safety.

Muscle Fiber Conduction Velocity During Electrically Stimulated Contraction at Various Joint Angles, During Joint Movements, and During Voluntary Contractions.

Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction.

Distally-referred surface electrical nerve stimulation (DR-SENS) for haptic feedback

Objective. This study’s objective is to understand distally-referred surface electrical nerve stimulation (DR-SENS) and evaluates the effects of electrode placement, polarity, and stimulation intensity on the location of elicited sensations in non-disabled individuals. Approach. A two-phased human experiment was used to characterize DR-SENS. In Experiment One, we explored 182 electrode combinations to identify a subset of electrode position combinations that would be most likely to elicit distally-referred sensations isolated to the index finger without discomfort. In Experiment Two, we further examined this subset of electrode combinations to determine the effect of stimulation intensity and electrode position on perceived sensation location. Stimulation thresholds were evaluated using parameter estimation by sequential testing and sensation locations were characterized using psychometric intensity tests. Main Results. We found that electrode positions distal to the wrist can consistently evoke distally referred sensations with no significant polarity dependency. The finger-palm combination had the most occurrences of distal sensations, and the different variations of this combination did not have a significant effect on sensation location. Increasing stimulation intensity significantly expanded the area of the sensation, moved the most distal sensation distally, and moved the vertical centroid proximally. Also, a large anodic-leading electrode at the elbow mitigated all sensation at the anodic-leading electrode site while using symmetric stimulation waveforms. Furthermore, this study showed that the most intense sensation for a given percept can be distally referred. Lastly, for each participant, at least one of the finger-palm combinations evaluated in this study worked at both perception threshold and maximum comfortable stimulation intensities. Significance. These findings show that a non-invasive surface electrical stimulation charge modulated haptic interface can be used to elicit distally-referred sensations on non-disabled users. Furthermore, these results inform the design of novel haptic interfaces and other applications of surface electrical stimulation based haptic feedback on electrodes positioned distally from the wrist.

Towards an optimised deep brain stimulation using a large-scale computational network and realistic volume conductor model

Objective. Constructing a theoretical framework to improve deep brain stimulation (DBS) based on the neuronal spatiotemporal patterns of the stimulation-affected areas constitutes a primary target. Approach. We develop a large-scale biophysical network, paired with a realistic volume conductor model, to estimate theoretically efficacious stimulation protocols. Based on previously published anatomically defined structural connectivity, a biophysical basal ganglia-thalamo-cortical neuronal network is constructed using Hodgkin–Huxley dynamics. We define a new biomarker describing the thalamic spatiotemporal activity as a ratio of spiking vs. burst firing. The per cent activation of the different pathways is adapted in the simulation to minimise the differences of the biomarker with respect to its value under healthy conditions. Main results. This neuronal network reproduces spatiotemporal patterns that emerge in Parkinson’s disease. Simulations of the fibre per cent activation for the defined biomarker propose desensitisation of pallido-thalamic synaptic efficacy, induced by high-frequency signals, as one possible crucial mechanism for DBS action. Based on this activation, we define both an optimal electrode position and stimulation protocol using pathway activation modelling. Significance. A key advantage of this research is that it combines different approaches, i.e. the spatiotemporal pattern with the electric field and axonal response modelling, to compute the optimal DBS protocol. By correlating the inherent network dynamics with the activation of white matter fibres, we obtain new insights into the DBS therapeutic action.

Photovoltaic Stimulation Induces Overdrive Suppression in Embryonic Chicken Cardiomyocytes

Abstract In this study, we employed calcium imaging to investigate the dynamics of intracellular calcium levels in embryonic chicken cardiomyocytes upon extracellular, optoelectronic stimulation. A photovoltaic layer of donoracceptor pigments on a flexible PET substrate was used as a wireless stimulation electrode. Our findings revealed a distinct change in their spontaneous activity pattern in cardiac cells following asynchronous light stimulation. A short pause in cellular activity, indicative of overdrive suppression, was observed in recordings from several different cells. The pause in activity signifies a transient refractory period induced by stimulation of the photovoltaic device with red light. These findings suggest that photovoltaic electrodes can be used to effectively modulate the electrical activity of cardiac cells in a wireless, non-pharmacological manner. This opens new avenues for non-invasive and precise light-modulated control of cellular electrophysiology as well as potential therapeutic applications for cardiac rhythm disorders.

Exploration of sensations evoked during electrical stimulation of the median nerve at the wrist level

Objective. Nerve rehabilitation following nerve injury or surgery at the wrist level is a lengthy process during which not only peripheral nerves regrow towards receptors and muscles, but also the brain undergoes plastic changes. As a result, at the time when nerves reach their targets, the brain might have already allocated some of the areas within the somatosensory cortex that originally processed hand signals to some other regions of the body. The aim of this study is to show that it is possible to evoke a variety of somatotopic sensations related to the hand while stimulating proximally to the injury, therefore, providing the brain with the relevant inputs from the hand regions affected by the nerve damage. Approach. This study included electrical stimulation of 28 able-bodied participants where an electrode that acted as a cathode was placed above the Median nerve at the wrist level. The parameters of electrical stimulation, amplitude, frequency, and pulse shape, were modulated within predefined ranges to evaluate their influence on the evoked sensations. Main results. Using this methodology, the participants reported a wide variety of somatotopic sensations from the hand regions distal to the stimulation electrode. Significance. Furthermore, to propose an accelerated stimulation tuning procedure that could be implemented in a clinical protocol and/or standalone device for providing meaningful sensations to the somatosensory cortex during nerve regeneration, we trained machine-learning techniques using the gathered data to predict the location/area, naturalness, and sensation type of the evoked sensations following different stimulation patterns.

Reuse of sodium–doped iridium oxide nanoparticles as a bio–stimulating electrode by a chemical and electrochemical recovery process

A sequential chlorination and electrochemical reduction process is demonstrated to convert Na–doped iridium oxide nanoparticles into useful IrIIICl63−(aq) serving as the precursor for the fabrication of bio–stimulating electrode. The Na–doped iridium oxide nanoparticles are treated in 35 wt% hydrochloric acid at 70 °C for 18 h to form IrIVCl62−(aq) with pH of 0.3, so the latter could be readily reduced to IrIIICl63−(aq) at a potentiostatic mode of 0.6 V (vs. SCE). The oxidation state and the nature of complexing ligands for the regenerated IrIIICl63− and IrIVCl62−, as well as commercially available IrIIICl63− are validated by X–ray Absorption Spectroscopy. UV–Vis profiles of regenerated IrIVCl62−(aq) are recorded and the absorbance at 487 nm signal is benchmarked against that of standard IrIVCl62−(aq) to obtain the effective regeneration ratio of 68.6%. X–ray diffraction patterns of Na–doped iridium oxide nanoparticles before and after the annealing treatment indicate the amorphous structure facilitates the chlorination step. The regenerated IrIIICl63− is reused to synthesize Na–doped iridium oxide thin film serving as a bio–stimulating electrode for implantable bio–electronics. The regenerated Na–doped iridium oxide thin film reveals a charge-storage capacity of 0.32 mC/cm2-nm and impressive stability that are comparable to those of fresh Na–doped iridium oxide thin film derived from commercially available IrIIICl63−.

Wireless Battery‐Free Peripheral Nerve Stimulation Conch for Remote Muscle Activation

AbstractPeripheral nerve stimulators have emerged as a crucial instrument in the realm of neurological disease, capable of modulating nerve activity through precisely targeted electrical stimulation to specific sites within the nervous system. Herein, a new wireless battery‐free peripheral nerve stimulation device for remote muscle activation is developed. The device with conch‐inspired bionic design can be wirelessly powered and controlled by a mobile phone playing audio via the piezoelectric effect. The device consists of two parts: a conch‐like signal‐intensifying piezoelectric resonator for converting acoustic wave into electrostimulation signal; and a pedestal with stimulation electrodes for transmitting the electrostimulation signal to a peripheral nerve. For remote nerve intervention, a programmed audio tone from one mobile phone can be tele‐transmitted from other phones according to the desired stimulation protocols. In‐vivo experiments in stimulating the sciatic nerve in mice showed that the device can activate muscles (e.g., 1 Hz 920 mV for 26 degree of leg movement), and the neuron‐muscle interaction has been confirmed by electromyogram (EMG). The wireless peripheral nerve stimulation conch achieves feasible remote muscle activation without batteries, and can extend the scope of self‐powered techniques for telemedicine and limb/trunk rehabilitation.