Multichannel Electrical Stimulation Research Articles

Assessment of the effect of pulsed currents and vibration therapy on the quality of life in patients with lumbosacral dorsopathy

Constant pain in the back leads to chronicity of the process and disability of the population. This work intends to develop and scientifically substantiate comprehensive treatment of lumbosacral dorsopathy patients with radicular syndrome in the subacute stage of the disease, including drug therapy, multichannel electrical stimulation with bipolar pulsed currents (MES BPC), and vibration massage, as well as to evaluate the impact of this treatment on the overall indicator of quality of life in patients. Results. Before treatment, the patients with lumbosacral dorsopathy and radicular syndrome in the subacute stage of the disease in the 1st (control) and 2nd (study) groups had significantly lower QOL indicators than normative ones, which reflected a decrease in quality of life. Complex treatment, including drug therapy, MES BPC, and vibration massage, contributed to a more pronounced and persistent improvement in the quality of life indicator in the patients of the 2nd (study) group throughout all periods of observation, compared with standard drug therapy in the 1st (control) group of the patients.

Energy-Efficient Fast-Transient Dynamic Reconfigurable Charge Pump for Multi-Channel Electrical Stimulation

An energy-efficient fast-transient dynamic reconfigurable charge pump (CP) is presented for multi-channel electrical stimulation applications. It includes a proposed dynamic reconfigurable CP to improve the overall power saving of the current-controlled stimulator (CCS) system, where individual or integrated controls of multiple CPs are selected by monitoring the CCS channels. For further energy-efficient operation, the stimulation mode-adaptive power on-off scheme is augmented by adopting a low-power two-dimensional frequency modulation (TFM) control and an initial pre-charging diode (IPD) circuit in the CP cores for fast settling performance. A CP prototype is fabricated in a 180-nm CMOS process, and its proposed operations were experimentally verified, achieving an overall more than 80% power-saving effect with maximum 69.8% general power efficiency and fast recovery performance.

Resembled Tactile Feedback for Object Recognition Using a Prosthetic Hand

Tactile feedback in the hand is essential for interaction with objects. Here, we evaluated how artificial tactile sensation affected the recognition of object properties using a myoelectrically controlled prosthetic hand. Electromyogram signals from the flexor and extensor finger muscles were used to continuously control either prosthetic joint velocity or position. Participants grasped objects of varying shape or size using the prosthetic hand. Tactile feedback was evoked by transcutaneous nerve stimulation along the participant's upper arm and modulated based on the prosthetic-object contact force. Multi-channel electrical stimulation targeted the median and ulnar nerve bundles to produce resembled tactile sensations at distinct hand regions. The results showed that participants could gauge the onset timing of tactile feedback to discern object shape and size. We also found that the position-controller led to a greater recognition accuracy of object size compared with velocity-control, potentially due to supplemental joint position information from muscle activation level. Our findings demonstrate that non-invasive tactile feedback can enable effective object shape and size recognition during prosthetic control. The evaluation of tactile feedback across myoelectric controllers can help understand the interplay between sensory and motor pathways involved in the control of assistive devices.

Energy efficiency of pulse shaping in electrical stimulation: the interdependence of biophysical effects and circuit design losses

Power efficiency in electrical stimulator circuits is crucial for developing large-scale multichannel applications like bidirectional brain-computer interfaces and neuroprosthetic devices. Many state-of-the-art papers have suggested that some non-rectangular pulse shapes are more energy-efficient for exciting neural excitation than the conventional rectangular shape. However, additional losses in the stimulator circuit, which arise from employing such pulses, were not considered. In this work, we analyze the total energy efficiency of a stimulation system featuring non-rectangular stimuli, taking into account the losses in the stimulator circuit. To this end, activation current thresholds for different pulse shapes and durations in cortical neurons are modeled, and the energy required to generate the pulses from a constant voltage supply is calculated. The proposed calculation reveals an energy increase of 14%–51% for non-rectangular pulses compared to the conventional rectangular stimuli, instead of the decrease claimed in previous literature. This result indicates that a rectangular stimulation pulse is more power-efficient than the tested alternative shapes in large-scale multichannel electrical stimulation systems.

Restoration of gait by combined treadmill training and multichannel electrical stimulation in non-ambulatory hemiparetic patients.

Functional electrical stimulation and treadmill training with partial body weight support through suspension by a parachute harness were combined for gait restoration in 11 chronic non-ambulatory hemiparetic patients. Individually adjusted multichannel stimulation of the trunk and of upper and lower limb muscles, as well as a motor driven treadmill, induced functional gait within 3 to 6 weeks. The improvement of gait ability was assessed by the Functional Ambulation Category test. Other motor functions were rated by the Rivermead Motor Score. The leg muscle strength, stride length, cadence, gait velocity and gait pattern were recorded. In seven of the patients, we did a single case research A-B-A study that showed that this combined approach had advantages, in regard to gait restoration and walking velocity (p

The effect of multichannel electrostimulation of neck nervous structures on the brain connectivity of patients with depressive disorders

To study neurophysiological processes during multichannel electrostimulation in patients with depressive disorder. The study involved 6 patients with depressive disorder (F33). The technology noninvasive multichannel stimulation of neck neural struct SYMPATHOKOR-01 device. Clinical and psychometric methods, functional neuroimaging (fMRTP) and multichannel electroencephalography (EEG) were used to assess treatment effect. In all patients, fMRTP and EEG results show the disturbances of brain connectivity, which are correlated with the clinical state of the disease, before treatment. After five stimulation procedures, there is an increase in functional connection of the medial prefrontal cortex (according to rs-fMRI results) and an increase in the synchronization of various parts of the cortex (EEG results). The results demonstrate the possibilities of multichannel electrical stimulation of the neck nervous structures to restore the intracerebral connections disturbed during depression due to the activation of neuroplasticity.

Microstructured thin-film electrode technology enables proof of concept of scalable, soft auditory brainstem implants.

Auditory brainstem implants (ABIs) provide sound awareness to deaf individuals who are not candidates for the cochlear implant. The ABI electrode array rests on the surface of the cochlear nucleus (CN) in the brainstem and delivers multichannel electrical stimulation. The complex anatomy and physiology of the CN, together with poor spatial selectivity of electrical stimulation and inherent stiffness of contemporary multichannel arrays, leads to only modest auditory outcomes among ABI users. Here, we hypothesized that a soft ABI could enhance biomechanical compatibility with the curved CN surface. We developed implantable ABIs that are compatible with surgical handling, conform to the curvature of the CN after placement, and deliver efficient electrical stimulation. The soft ABI array design relies on precise microstructuring of plastic-metal-plastic multilayers to enable mechanical compliance, patterning, and electrical function. We fabricated soft ABIs to the scale of mouse and human CN and validated them in vitro. Experiments in mice demonstrated that these implants reliably evoked auditory neural activity over 1 month in vivo. Evaluation in human cadaveric models confirmed compatibility after insertion using an endoscopic-assisted craniotomy surgery, ease of array positioning, and robustness and reliability of the soft electrodes. This neurotechnology offers an opportunity to treat deafness in patients who are not candidates for the cochlear implant, and the design and manufacturing principles are broadly applicable to implantable soft bioelectronics throughout the central and peripheral nervous system.

Effect of Multi-channel Functional Electrical Stimulation on Cognitive Function of Bedridden Elderl

Effect of Multi-channel Functional Electrical Stimulation on Cognitive Function of Bedridden Elderl

The influence of surface EMG-triggered multichannel electrical stimulation on sensomotoric recovery in patients with lumbar disc herniation: study protocol for a randomized controlled trial (RECO)

BackgroundIntervertebral disc degeneration is one of the most common reasons for chronic low back pain and sensomotoric deficits, often treated by lumbar sequestrectomy. Nevertheless, the prognostic factors relevant for time and quality of recovery, of the surgical procedure, relative to conservative treatment, remain controversial and require further investigation. Surface electrical stimulation (SES) may be an influential intervention, already showing positive impact on motor and sensory recovery in different patient groups. Since mechanisms of SES still remain unclear, further inquiry is needed.Methods/DesignThis is a prospective, monocentric, randomized, controlled clinical trial. A total of 80 adult patients suffering from a lumbar disc herniation (LDH; 40 treated surgically, 40 conservatively) are allocated in a ratio of 1:1. Patients in the treatment group will receive surface electromyography (EMG)-triggered electrical stimulation for eight weeks, whereas patients in the control group will not obtain any additional treatment. The primary outcome parameter is defined as the cold detection threshold (CDT), determined by quantitative sensory testing (QST), 24 months after intervention. Secondary outcome parameters include the inquiry of sensory nerve function by two-point discrimination and QST, the assessment of motor nerve function by manual muscle testing, and validated scales and scores. These include: the Oswestry Disability Index (ODI) and the Core Outcome Measures Index (COMI) assessing the domains pain, back-specific function, work disability, and patient satisfaction; the EQ-5D investigating the patient’s generic health status; the painDETECT questionnaire (PD-Q) to identify neuropathic pain components; and the Beck Depression Inventory (BDI) to assess severity of depression. Moreover, neurological status, pain medication usage, and blood samples (CRP, TNFα, IL-1β, IL-6) will be evaluated. Study data generation (study site) and data storage, processing, and statistical analysis are clearly separated.DiscussionThe results of the RECO study will detect the effect of EMG-triggered multichannel SES on the improvement of mechanical and thermal sensitivity and the effect on motor recovery and pain, associated with clinical and laboratory parameters. Furthermore, data comparing surgical and conservative treatment can be collected. This will hopefully allow treatment recommendations for patients with LDH accompanied by a sensomotoric deficit.Trial registrationISRCTN, ISRCTN12741173. Registered on 15 January 2017.

Mechanomyography-Based Wearable Monitor of Quasi-Isometric Muscle Fatigue for Motor Neural Prostheses.

A motor neural prosthesis based on surface functional electrical stimulation (sFES) can restore functional movement (e.g., standing, walking) in patients with a spinal cord injury (SCI). sFES generates muscle contractions in antigravity muscles and allows balance-assisted standing. This induced standing has several benefits, such as improved cardiovascular function, decreased incidence of urinary infections, reduced joint contractures, and muscle atrophy. The duration of sFES assisted standing is limited due to the quick onset of muscle fatigue. Currently, there is no method available to reliably estimate real-time muscle fatigue during sFES. Simply monitoring the M-wave changes is not suitable due to the high signal disturbances that arise during multi-channel electrical stimulation. Mechanomyography (MMG) is immune to electrical stimulation artifacts and can be used to detect subtle vibrations on the surface of the skin related to activation of the underlying muscle's motor units (MU). The aim of this study was to develop a method for detecting muscle fatigue brought on by sFES. The method was tested in three different heads of the quadriceps muscle in SCI patients during electrically elicited quasi-isometric contraction. Six spinal cord-injured male volunteers, with no voluntary control of the quadriceps muscle participated in the study. Electrical bursts of voltage-controlled monophasic square pulses at frequencies of 1 kHz (50% duty cycle) at 50 Hz (15% duty cycle) were used to generate thigh muscle contractions that controlled the knee joint in the sagittal plane. The pulse amplitudes were set to position the knee joint at a 5° angle from the horizontal plane and when the knee angle dropped to 20° (e.g., the quadriceps were unable to hold the lower leg in the desired position), the test was terminated. Two data segments lasting 10 s each, at the beginning and end of each test, were analyzed. The muscle contraction was assessed by MMG sensors positioned on the rectus femoris, vastus lateralis, and vastus medialis muscles. Data segments were decomposed into 11 frequency bands using a Cauchy wavelet transform. In the initial time interval (non-fatigued muscle), the power peak was concentrated in the 11.31 Hz frequency band. In the final interval (muscle fatigued) this peak shifted to lower frequencies (2 and 6 Hz frequency bands). The decreased frequency was most prominent during the last 4 s of the recordings. It was shown that MMG could be used as a real-time indicator of muscle fatigue during FES-induced isometric contraction of quadriceps; hence, MMG could be used in closed-loop control as a fatigue detector. Subsequent studies for non-isometric contractions could possibly lead to prediction of muscle fatigue before contractile failure during functional use of the muscle.

A wireless wearable surface functional electrical stimulator

ABSTRACTIn this paper, a wireless wearable functional electrical stimulator controlled by Android phone with real-time-varying stimulation parameters for multichannel surface functional electrical stimulation application has been developed. It can help post-stroke patients using more conveniently. This study focuses on the prototype design, including the specific wristband concept, circuits and stimulation pulse-generation algorithm. A novel stimulator circuit with a driving stage using a complementary current source technique is proposed to achieve a high-voltage compliance, a large output impedance and an accurate linear voltage-to-current conversion. The size of the prototype has been significantly decreased to 17 × 7.5 × 1 cm3. The performance of the prototype has been tested with a loaded resistor and wrist extension/flexion movement of three hemiplegic patients. According to the experiments, the stimulator can generate four-channel charge-balanced biphasic stimulation with a voltage amplitude up to 60 V, and the pulse frequency and width can be adjusted in real time with a range of 100–600 μs and 20–80 Hz, respectively.

Sensory Barrage Stimulation in the Treatment of Elbow Spasticity: A Crossover Double Blind Randomized Pilot Trial.

To assess the feasibility of using a novel form of multichannel electrical stimulation, termed Sensory Barrage Stimulation (SBS) for the treatment of spasticity affecting the elbow flexor muscles and to compare this with conventional single-channel TENS stimulation. Altogether ten participants with spasticity of the flexor muscles of the elbow of Grade 2 or above on the Modified Ashworth Scale (MAS) were recruited to this crossover double blind randomized trial. The participants received two intervention sessions (SBS and TENS), one week apart in a randomized order. Both interventions were applied over the triceps brachii on the affected arm for a duration of 60 minutes. Spasticity was measured using the MAS. Secondary outcome measures were self-reported change in spasticity, measured on a visual analog scale (VAS, 0-100), and therapist-rated strength of elbow extension and strength of elbow flexion. Measurements were taken immediately before each intervention was applied, immediately after the intervention, and one hour after the intervention. Immediately after stimulation spasticity showed a significant reduction for both TENS and SBS groups assessed by MAS -0.9 ± 0.2 vs. -1.1 ± 0.2 and by VAS -15 ± 3 vs. -31 ± 8. For SBS this improvement in MAS was still present at one hour after the stimulation, but not for TENS. Altogether seven SBS responders and four TENS responders were identified. This study demonstrates the feasibility and practicality of applying the new concept of SBS. Promising results indicate it causes a reduction in spasticity.

The influence of electrical stimulation on the peripheral immune system under the experimental and clinical conditions

The authors for the first time provide the scientifically-grounded substantiation for the application of electrical stimulation with bipolar pulsed currents for the combined treatment of the patents presenting with acne vulgaris. Experiments on the rabbits have demonstrated the influence of bipolar pulsed currents on the cellular composition of lymph nodes and thereby facilitated the better understanding of certain theoretical aspects of the application of electrical stimulation at large. The clinical study on the application of multi-channel electrical stimulation and microcurrent therapy showed that these physical factors may cause remodeling of immunogenesis in the patents presenting with acne vulgaris manifested as the normalization of the cellular composition of peripheral blood (leukocyte, lymphocyte, T- and B-lymphocyte counts and immunoglobulin levels). These findings confirm the effectiveness of the proposed integrated treatment responsible for the enhancement of the overall resistance of the patents with acne vulgaris. Moreover, this therapeutic modality proved to exert the immunocorrective action and promote the restoration of the adaptive capacity at large. As a result, 80.9% of the patients presenting with acne vulgaris enjoyed prolonged remission of the disease.

Perception of Mandarin Chinese with cochlear implants using enhanced temporal pitch cues

A cochlear implant (CI) signal processing strategy named F0 modulation (F0mod) was compared with the advanced combination encoder (ACE) strategy in a group of four post-lingually deafened Mandarin Chinese speaking CI listeners. F0 provides an enhanced temporal pitch cue by amplitude modulating the multichannel electrical stimulation pattern at the fundamental frequency (F0) of the incoming speech signal. Word and sentence recognition tests were carried out in quiet and in noise. The responses for the word-recognition test were further segmented into phoneme and tone scores. Off-line implementations of ACE and F0mod were used, and electrical stimulation patterns were directly streamed to the CI subject's implant. To focus on the feasibility of enhanced temporal cues for tonal language perception, idealized F0 information that was extracted from speech tokens in quiet was used in the F0mod processing of speech-in-noise mixtures. The results indicated significantly better lexical tone perception with the F0mod strategy than with ACE for the male voice (p<0.05). No significant differences in sentence recognition were found between F0mod and ACE.

Memory encoding in hippocampal ensembles is negatively influenced by cannabinoid CB1 receptors

It has previously been demonstrated that the detrimental effect on the performance of a delayed nonmatch to sample (DNMS) memory task by exogenously administered cannabinoid (CB1) receptor agonist, WIN 55212-2 (WIN), is reversed by the receptor antagonist rimonabant. In addition, rimonabant administered alone elevates DNMS performance, presumably through the suppression of negative modulation by released endocannabinoids during normal task performance. Other investigations have shown that rimonabant enhances encoding of DNMS task-relevant information on a trial-by-trial, delay-dependent basis. In this study, these reciprocal pharmacological actions were completely characterized by long-term, chronic intrahippocampal infusion of both agents (WIN and rimonabant) in successive 2-week intervals. Such long-term exposure allowed extraction and confirmation of task-related firing patterns, in which rimonabant reversed the effects of CB1 agonists. This information was then utilized to artificially impose the facilitatory effects of rimonabant and to reverse the effects of WIN on DNMS performance, by delivering multichannel electrical stimulation in the same firing patterns to the same hippocampal regions. Direct comparison of normal and WIN-injected subjects, in which rimonabant injections and ensemble firing facilitated performance, verified reversal of the modulation of hippocampal memory processes by CB1 receptor agonists, including released endocannabinoids.

Electrical stimulation for the suppression of pathological tremor

Pathological tremor is manifested as an involuntary oscillation of one or more body parts. Tremor greatly decreases the quality of life and often prevents the patient from performing daily activities. We hypothesized that sensors-driven multichannel electrical stimulation could stabilize affected joints by activating the antagonistic muscles during involuntary activation of agonist muscles and vice versa (out-of-phase stimulation). Here, we present the new system (hardware and software) and the testing of its operation. The hardware consists of a multichannel stimulator and inertial sensors for feedback. The software implements adaptive sensors-driven control for the out-of-phase stimulation. The system was initially applied to healthy persons at the wrist and elbow joints to test the efficiency of the hardware and software solutions. Predefined rhythmic stimulation resulted in tremulous movement, which subjects could not prevent; yet, they were still able to functionally use their hand. The system was then applied to seven patients with Parkinson's disease and essential tremor for minimization of the wrist joint tremor. In six patients, the adaptive out-of-phase stimulation resulted in a significant decrease in the amplitude of tremor (67 ± 13%). In one patient, the stimulation did not result in the expected reduction of tremor.

Methods to improve constraint-induced movement therapy

In global terms, cerebrovascular stroke is the leading cause of long-term disability. Despite improved acute phase management of stroke, the majority of survivors are disabled and many require effective rehabilitation. Constraint-induced movement therapy (CIMT) is one of the recently emerging therapies for subjects with stroke. The effects of two-week long CIMT on behavioural, neurophysiologic and neuroimaging measures in subjects with chronic stroke were studied. Furthermore, the effects of combined upper limb exercise and peripheral preprogrammed multichannel electrical stimulation, i.e. functional electrical therapy (FET), were evaluated. Behavioral gains were obtained in hand function and functional MRI activations, and, in addition, TMS responses appeared more laterally and/or bilaterally in the affected hemisphere in the subjects after CIMT. Neurophysiologic and functional imaging results were supportive evidence for the benefits of use-dependent plasticity in subjects with chronic stroke.

Current-level discrimination and spectral profile analysis in multi-channel electrical stimulation

In experiment 1, six cochlear-implant (CI) listeners discriminated a stimulation pattern eliciting equal loudness for each electrode from a stimulation pattern in which the stimulation at one or more electrodes was increased (peak) or decreased (notch). Three cochlear locations and three bandwidths were tested, without and with level roving. Listeners could always detect peaks but not always notches. Increasing the bandwidth beyond two electrodes produced no improvement in just-noticeable differences (JNDs). JNDs for the basal location were higher than for the apical and middle locations, although listeners had highly individual tendencies. In experiment 2, listeners discriminated changes in the peak heights and notch depths. JNDs for higher peaks were better while JNDs for deeper notches were worse than for experiment 1. In experiment 3, listeners discriminated the electrode position of peaks or notches. JNDs were approximately one electrode. In experiment 4, the first three experiments were repeated with large amounts of level roving. There was no evidence that CI listeners performed an across-channel comparison in these tasks.

Effects of a 2-, 3- and 4-electrode stimulator design on current dispersion on the surface and into the limb during electrical stimulation in controls and patients with wounds

Electrical stimulation is a widely used modality in the field of physical therapy and exercise physiology. The most common method for the application of electrical stimulation is a two-electrode system where one electrode is the source and the other is a reference. However, recent studies report that a more effective delivery system can be achieved if more than two electrodes are used. In the present investigation, the circuitry to deliver electrical stimulation through a 2-, 3- or 4-electrode delivery system was designed. The system was evaluated by its ability to deliver current on the surface of the skin as well as deep into the quadriceps muscle in six control subjects and in and around wounds in six other subjects. The results of the experiments showed that much better depth of penetration was achieved in a 4-electrode system (one electrode was on the opposite side of the limb and three electrodes were on top of the limb) than in either a 2- or a 3-electrode delivery system. In non-wounded skin, given the same current from the stimulator, the current in the quadriceps muscle was found to be double with a 4-electrode versus a 2-electrode system. In wounds, this same finding was seen. Here, blood flow, an indicator of the effectiveness of electrical stimulation in wounds, was three times higher if a multi-channel stimulator was used versus a 2-channel stimulator. Thus a multi-channel electrical stimulation system is more effective than a 2-electrode system.

Neural prostheses for walking restoration

We review the state of the art of multi-channel electrical stimulation (ES) systems with surface electrodes for assistance in the standing and walking of paraplegics and hemiplegics. For the group of complete paraplegics, walking achieved with available ES systems is below their expectations, especially since these systems cannot compete with mobility provided to them by a wheelchair. However, standing and walking with ES systems are beneficial because they contribute to the improvement of physiological functions. For individuals who can stand with some arm support (e.g., paraplegics with incomplete injury and hemiplegics), the current ES systems are an effective augmentation of walking. We suggest that an ES system for walking of incomplete paraplegics and hemiplegics will be better accepted if the stimulation is regulated by a rule-based control, that is, a preprogrammed, sensor-triggered activation of several muscles resulting in normal walking. We present a method to obtain muscle activity profiles from simulation of a customized model of the patient that can be used for the synthesis of rules for control.