High-level Spinal Cord Injury Research Articles

MUNDUS project: MUltimodal Neuroprosthesis for daily Upper limb Support

BackgroundMUNDUS is an assistive framework for recovering direct interaction capability of severely motor impaired people based on arm reaching and hand functions. It aims at achieving personalization, modularity and maximization of the user’s direct involvement in assistive systems. To this, MUNDUS exploits any residual control of the end-user and can be adapted to the level of severity or to the progression of the disease allowing the user to voluntarily interact with the environment. MUNDUS target pathologies are high-level spinal cord injury (SCI) and neurodegenerative and genetic neuromuscular diseases, such as amyotrophic lateral sclerosis, Friedreich ataxia, and multiple sclerosis (MS). The system can be alternatively driven by residual voluntary muscular activation, head/eye motion, and brain signals. MUNDUS modularly combines an antigravity lightweight and non-cumbersome exoskeleton, closed-loop controlled Neuromuscular Electrical Stimulation for arm and hand motion, and potentially a motorized hand orthosis, for grasping interactive objects.MethodsThe definition of the requirements and of the interaction tasks were designed by a focus group with experts and a questionnaire with 36 potential end-users.Five end-users (3 SCI and 2 MS) tested the system in the configuration suitable to their specific level of impairment. They performed two exemplary tasks: reaching different points in the working volume and drinking. Three experts evaluated over a 3-level score (from 0, unsuccessful, to 2, completely functional) the execution of each assisted sub-action.ResultsThe functionality of all modules has been successfully demonstrated. User’s intention was detected with a 100% success. Averaging all subjects and tasks, the minimum evaluation score obtained was 1.13 ± 0.99 for the release of the handle during the drinking task, whilst all the other sub-actions achieved a mean value above 1.6. All users, but one, subjectively perceived the usefulness of the assistance and could easily control the system. Donning time ranged from 6 to 65 minutes, scaled on the configuration complexity.ConclusionsThe MUNDUS platform provides functional assistance to daily life activities; the modules integration depends on the user’s need, the functionality of the system have been demonstrated for all the possible configurations, and preliminary assessment of usability and acceptance is promising.

Application of Digital Volume Pulse Analysis in Patients with Spinal Cord Injury

Orthostatic hypotension is a common complication following spinal cord injury (SCI). However, an easy method to quantify the degree of vasomotor impairment below the level of injury is lacking. We postulated that SCI patients with different sympathetic reserves exhibited different digital volume pulse contours. Thirty-one patients with high chronic SCI (above the T6 neurologic level) and 28 low-level SCI patients (below T6) were recruited. Thirty-two age- and BMI-matched healthy participants were enrolled in the control group. All participants were positioned on a tilting table for five minutes in each of the following: supine rest (SR), 60-degree head-up tilt (HUT), and recovery to supine position. Digital volume pulse (DVP), heart rate variability (HRV), and blood pressure were measured. The reflection index (RI) was calculated as the amplitude of reflection wave divided by directly-transmitted wave. The RI ratio is the RI value in the fifth minute during the HUT position divided by RI in SR. Low frequency to high frequency power ratio (LF/HF), high frequency power (HFP), normalized low frequency power (LFn) and high frequency power (HFn) were recorded in HRV analysis. Our results revealed that patients with a higher level of injury had a reduced reflection wave of DVP in SR and HUT. High-level SCI patients also had a smaller RI ratio. Additionally, the increase of LF/HF during the transition from SR to HUT was attenuated in high SCI patients. However, the decrease of HF power was normally preserved in high SCI patients. We concluded that posture change alters the contour of the pulse wave, which is related to the level of injury. The RI ratio could be used to quantify the degree of vasoconstriction impairment below the injury level in SCI patients.

Tongue drive: a wireless tongue- operated means for people with severe disabilities to communicate their intentions

Assistive technologies (ATs) can enable individuals with severe disabilities to communicate their intentions to other devices or individuals, particularly allowing them to control their environments via computers. In this article, we have introduced the basic concept and development of a new wireless tongue-operated AT, called Tongue Drive System (TDS), that can wirelessly detect users' tongue movements using an array of magnetic sensors and a small magnetic tracer secured on the tongue, and translate them into a set of user-defined commands in real time, which can then be used to communicate with target devices in the users' environments. Our goal is to provide users with an unobtrusive, minimally invasive, low-power, high-bandwidth, wireless, wearable, easy-to-use, and aesthetically appealing solution that is superior to other existing ATs for people with the most severe physical disabilities. The performance of the latest TDS prototype has been evaluated by both able-bodied subjects and patients with high-level spinal cord injuries. Results have demonstrated that the TDS can indeed offer its users much higher communication bandwidth compared to EEGbased brain computer interfaces.

Electrophrenic pacing and decannulation for high-level spinal cord injury: A case series

BackgroundIn 1997, guidelines were developed for the management of high-level ventilator-dependent patients with spinal cord injury who had little or no ventilator-free breathing ability (VFBA). This article describes the three categories of patients, the decannulation criteria, and the successful decannulation of four patients with no VFBA and electrophrenic/diaphragm pacing, using these criteria.MethodCase series.ConclusionLack of VFBA in patients with high-level spinal cord injury does not mandate tracheostomy or electrophrenic/diaphragm pacing.

Remote inflammatory response in liver is dependent on the segmental level of spinal cord injury

Traumatic spinal cord injury (SCI) triggers a systemic inflammatory response (SIR) that contributes to a high incidence of secondary organ complications, particularly after a cervical or high-level thoracic injury. Because liver plays a key role in initiating and propagating the SIR, the aim of this study was to assess the effects that SCI at differing segmental levels has on the intensity of the inflammatory response in the liver. Using male Wistar rats, clip compression SCI was performed at the 4th thoracic (T4 SCI; high-level SCI) or the 12th thoracic (T12 SCI; low-level SCI) spinal cord segment. Sham-injured rats had a partial laminectomy, but no SCI. Leukocyte recruitment to the liver, hepatic blood flow, and hepatocellular injury/death were assessed using intravital microscopy and histology. Chemokine and cytokine concentrations were assessed in the liver. Outcomes were measured at 1.5 hours, 12 hours, and 24 hours after SCI. At 12 hours after injury, T4 SCI caused a threefold increase in hepatic leukocyte recruitment compared with T12 SCI (p < 0.05). T4 SCI induced 50% more hepatocyte injury than T12 SCI at 12 hours (p < 0.05). Hepatic blood flow decreased after SCI, but not after sham injury, and stayed decreased only after T4 SCI at 24 hours after injury. The T4 SCI-induced changes were accompanied by increases in the hepatic concentrations of interleukin-1β, leptin, interleukin 10, and cytokine-induced neutrophil chemoattractant-1 at 1.5 hours. Our findings indicate that traumatic SCI triggers an acute SIR that contributes to hepatocellular injury. SCI-induced remote injury/dysfunction to the liver appears to be transient and is more robust after an upper thoracic SCI compared with a lower thoracic SCI.

Resolution of tracheostomy complications by decanulation and conversion to noninvasive management for a patient with high-level tetraplegia.

To report conversion from tracheostomy (TIV) to noninvasive intermittent positive pressure ventilation (NIV) for a continuously ventilator-dependent patient with high-level spinal cord injury (SCI) with no measurable vital capacity (VC = 0 mL) to resolve tracheostomy-associated complications. A case report of a 38-year-old female in a chronic care facility in Japan with a 10-year history of ventilator-dependent tetraplegia (C1 ASIA-A) presented for increasing difficulty vocalizing. She had been using a fenestrated cuffed tracheostomy tube to produce speech with the cuff deflated. Speech was increasingly hypophonic, because of tracheostoma enlargement, tube migration, and tracheal granulation. The NIV was provided via nasal and oral interfaces, the ostomy was surgically closed, and vocalization resumed. Airway secretions were expulsed using manually assisted coughing. The patient returned to the community. Conversion to NIV should be considered for ventilator-dependent patients with SCI who have adequate bulbar-innervated muscle function to permit effective speech and assisted coughing.

Diaphragmatic pacing stimulation in spinal cord injury: anesthetic and perioperative management

OBJECTIVE:The standard therapy for patients with high-level spinal cord injury is long-term mechanical ventilation through a tracheostomy. However, in some cases, this approach results in death or disability. The aim of this study is to highlight the anesthetics and perioperative aspects of patients undergoing insertion of a diaphragmatic pacemaker.METHODS:Five patients with quadriplegia following high cervical traumatic spinal cord injury and ventilator-dependent chronic respiratory failure were implanted with a laparoscopic diaphragmatic pacemaker after preoperative assessments of their phrenic nerve function and diaphragm contractility through transcutaneous nerve stimulation. ClinicalTrials.gov: NCT01385384.RESULTS:The diaphragmatic pacemaker placement was successful in all of the patients. Two patients presented with capnothorax during the perioperative period, which resolved without consequences. After six months, three patients achieved continuous use of the diaphragm pacing system, and one patient could be removed from mechanical ventilation for more than 4 hours per day.CONCLUSIONS:The implantation of a diaphragmatic phrenic system is a new and safe technique with potential to improve the quality of life of patients who are dependent on mechanical ventilation because of spinal cord injuries. Appropriate indication and adequate perioperative care are fundamental to achieving better results.

Phrenic motoneuron expression of serotonergic and glutamatergic receptors following upper cervical spinal cord injury

Following cervical spinal cord injury at C2 (SH hemisection model) there is progressive recovery of phrenic activity. Neuroplasticity in the postsynaptic expression of neurotransmitter receptors may contribute to functional recovery. Phrenic motoneurons express multiple serotonergic (5-HTR) and glutamatergic (GluR) receptors, but the timing and possible role of these different neurotransmitter receptor subtypes in the neuroplasticity following SH are not clear. The current study was designed to test the hypothesis that there is an increased expression of serotonergic and glutamatergic neurotransmitter receptors within phrenic motoneurons after SH. In adult male rats, phrenic motoneurons were labeled retrogradely by intrapleural injection of Alexa 488-conjugated cholera toxin B. In thin (10μm) frozen sections of the spinal cord, fluorescently-labeled phrenic motoneurons were visualized for laser capture microdissection (LCM). Using quantitative real-time RT-PCR in LCM samples, the time course of changes in 5-HTR and GluR mRNA expression was determined in phrenic motoneurons up to 21days post-SH. Expression of 5-HTR subtypes 1b, 2a and 2c and GluR subtypes AMPA, NMDA, mGluR1 and mGluR5 was evident in phrenic motoneurons from control and SH rats. Phrenic motoneuron expression of 5-HTR2a increased ~8-fold (relative to control) at 14days post-SH, whereas NMDA expression increased ~16-fold by 21-days post-SH. There were no other significant changes in receptor expression at any time post-SH. This is the first study to systematically document changes in motoneuron expression of multiple neurotransmitter receptors involved in regulation of motoneuron excitability. By providing information on the neuroplasticity of receptors expressed in a motoneuron pool that is inactivated by a higher-level spinal cord injury, appropriate pharmacological targets can be identified to alter motoneuron excitability.

Managing high-level cervical spinal cord injuries: intensivist's point of view

Managing high-level cervical spinal cord injuries: intensivist's point of view

077 Cerebrovascular autoregulation during orthostatic stress after spinal cord injury

077 Cerebrovascular autoregulation during orthostatic stress after spinal cord injury

Alternative communication systems for people with severe motor disabilities: a survey

We have now sufficient evidence that using electrical biosignals in the field of Alternative and Augmented Communication is feasible. Additionally, they are particularly suitable in the case of people with severe motor impairment, e.g. people with high-level spinal cord injury or with locked-up syndrome. Developing solutions for them implies that we find ways to use sensors that fit the user's needs and limitations, which in turn impacts the specifications of the system translating the user's intentions into commands. After devising solutions for a given user or profile, the system should be evaluated with an appropriate method, allowing a comparison with other solutions. This paper submits a review of the way three bioelectrical signals - electromyographic, electrooculographic and electroencephalographic - have been utilised in alternative communication with patients suffering severe motor restrictions. It also offers a comparative study of the various methods applied to measure the performance of AAC systems.

Concurrent respiratory resistance training and changes in respiratory muscle strength and sleep in an individual with spinal cord injury: case report

ContextQuality sleep possesses numerous benefits to normal nighttime and daytime functioning. High-level spinal cord injury (SCI) often impacts the respiratory muscles that can lead to poor respiratory function during sleep and negatively affect sleep quality. The impact of respiratory muscle training (RMT) on sleep quality, as assessed by overnight polysomnography (PSG), is yet to be determined among the spinal cord-injured population. This case report describes the effects of 10 weeks of RMT on the sleep quality of a 38-year-old male with cervical SCI.MethodsCase report.Findings/resultsThe subject completed overnight PSG, respiratory muscle strength assessment, and subjective sleepiness assessment before and after 10 weeks of RMT. The post-test results indicated improvements in sleep quality (e.g. fewer electroencephalographic (EEG) arousals during sleep) and daytime sleepiness scores following RMT.Conclusion/clinical relevanceRespiratory activity has been proven to impact EEG arousal activity during sleep. Arousals during sleep lead to a fragmented sleeping pattern and affect sleep quality and daytime function. Our subject presented with a typical sleep complaint of snoring and excessive sleepiness. The subject's pre-test PSG demonstrated a large number of arousals during sleep. It is important for all individuals complaining of problems during sleep or daytime problems associated with sleep (i.e. excessive daytime sleepiness) to seek medical attention and proper evaluation.

Autonomic function as a missing piece of the classification of Paralympic athletes with spinal cord injury

When someone suffers a spinal cord injury (SCI) many organs, including those of the cardiovascular (CV) system, cease to be controlled by the autonomic nervous system (ANS). Response to physical activity fails to meet the needs of the body and typically results in low blood pressure (BP), and in turn, reduced endurance and performance. This study examines the effect of SCI on the ANS of elite athletes and possible effect on their CV functions and ultimately their performance. The study also provides input on evidence of boosting and the current classification system. Finally, authors are exploring a possibility for future research in assessing whether consideration of ANS function would strengthen current Paralympic classification systems. MEDLINE, SportDiscus, Embase databases and the official Paralympic website were reviewed. In total, 60 manuscripts and five website documents were reviewed. Athletes with high-level SCI affecting the ANS have limited ability to regulate their heart rate and BP in response to exercise. According to current Paralympic classification systems, these athletes are grouped with competitors who have similar motor control but intact ANS, thereby potentially putting them at a disadvantage within their own classification category. High-level SCI athletes with ANS dysfunction are also the only athletes who experience episodes of autonomic dysreflexia (AD). Whereas AD is a state of uninhibited sympathetic discharge, it is called 'boosting' when intentionally induced during competition. Boosting has been shown to improve sporting performance but can also cause serious complications due to extreme rises in BP. Therefore, boosting has been banned by the International Paralympic Committee (IPC). Despite this ban some elite high-level SCI athletes continue to boost. The IPC recognizes that the current classification systems are not the gold standard and further work is needed to create a more evidence-based classification. Further research is needed to determine if the inclusion of ANS parameters contributes to strengthen classifications systems in Paralympic sports. This includes the development of a simple, valid and reliable bedside assessment of autonomic function that can be used to reliably compare athletes with or without ANS dysfunction thereby enabling further research into the isolated effect of ANS dysfunction on sporting performance. Researchers who are studying individuals with SCI, and who have CV parameters as their outcomes, should ensure a homogenous study group by the presence or absence of ANS function in addition to level of lesion so as to eliminate the potential for confounding variables that lead to inaccurate interpretation of results.

La stimulation phrénique implantée

The implanted phrenic nerve stimulation is a technique restoring the spontaneous breathing in patients with a failing respiratory command, which leads to a dependency on mechanical ventilation. This technique may particularly involve quadriplegic patients with a high-level spinal cord injury and patients with congenital central hypoventilation syndrome. The electrophysiological diaphragm investigations allow a better patient selection, assessing in one hand a definite problem with central respiratory command and on the other hand the integrity of phrenic nerves. To date, two different phrenic stimulation techniques are available in France: the quadripolar intra-thoracic stimulation and the bipolar intra-diaphragmatic stimulation. Both techniques allow patients to be weaned off their mechanical ventilator, improving dramatically their quality of life. In fact, one of the systems (phrenic intra-diaphragmatic stimulation) was granted reimbursement in France in 2009 and is now on the social security list of reimbursed products. In the future, the phrenic intra-diaphragmatic stimulation may find its place in the intensive care unit with temporal use following surgeries leading to specific respiratory complications as well as diaphragmatic atrophy induced by prolonged mechanical ventilation.

Functional reorganization of upper-body movement after spinal cord injury.

Survivors of spinal cord injury need to reorganize their residual body movements for interacting with assistive devices and performing activities that used to be easy and natural. To investigate movement reorganization, we asked subjects with high-level spinal cord injury (SCI) and unimpaired subjects to control a cursor on a screen by performing upper-body motions. While this task would be normally accomplished by operating a computer mouse, here shoulder motions were mapped into the cursor position. Both the control and the SCI subjects were rapidly able to reorganize their movements and to successfully control the cursor. The majority of the subjects in both groups were successful in reducing the movements that were not effective at producing cursor motions. This is inconsistent with the hypothesis that the control system is merely concerned with the accurate acquisition of the targets and is unconcerned with motions that are not relevant to this goal. In contrast, our findings suggest that subjects can learn to reorganize coordination so as to increase the correspondence between the subspace of their upper-body motions with the plane in which the controlled cursor moves. This is effectively equivalent to constructing an inverse internal model of the map from body motions to cursor motions, established by the experiment. These results are relevant to the development of interfaces for assistive devices that optimize the use of residual voluntary control and enhance the learning process in disabled users, searching for an easily learnable map between their body motor space and control space of the device.

Posterolateral Surface Electrical Stimulation of Abdominal Expiratory Muscles to Enhance Cough in Spinal Cord Injury

Background. Spinal cord injury (SCI) patients have respiratory complications because of abdominal muscle weakness and paralysis, which impair the ability to cough. Objective. This study aims to enhance cough in high-level SCI subjects (n = 11, SCI at or above T6) using surface electrical stimulation of the abdominal muscles via 2 pairs of posterolaterally placed electrodes. Methods. From total lung capacity, subjects performed maximum expiratory pressure (MEP) efforts against a closed airway and voluntary cough efforts. Both efforts were performed with and without superimposed trains of electrical stimulation (50 Hz, 1 second) at a submaximal intensity set to evoke a gastric pressure (P ga) of 40 cm H2O at functional residual capacity. Results. In the MEP effort, stimulation increased the maximal P ga (from 21.4 ± 7.0 to 59.0 ± 5.7 cm H2O) and esophageal pressure (P es; 47.2 ± 11.7 to 65.6 ± 13.6 cm H2O). During the cough efforts, stimulation increased P ga (19.5 ± 6.0 to 57.9 ± 7.0 cm H2O) and P es (31.2 ± 8.7 to 56.6 ± 10.5 cm H2O). The increased expiratory pressures during cough efforts with stimulation increased peak expiratory flow (PEF, by 36% ± 5%), mean expiratory flow (by 80% ± 8%), and expired lung volume (by 41% ± 16%). In every subject, superimposed electrical stimulation improved peak expiratory flow during cough efforts (by 0.99 ± 0.12 L/s; range, 0.41-1.80 L/s). Wearing an abdominal binder did not improve stimulated cough flows or pressures. Conclusions. The increases in P ga and PEF with electrical stimulation using the novel posterolateral electrode placement are 2 to 3 times greater than improvements reported in other studies. This suggests that posterolateral electrical stimulation of abdominal muscles is a simple noninvasive way to enhance cough in individuals with SCI.

Transurethral incision of the bladder neck to treat bladder neck dysfunction and voiding dysfunction in patients with high‐level spinal cord injuries

Detrusor-sphincter dyssynergia (DSD) and bladder neck dysfunction (BND) may cause voiding dysfunction in patients with spinal cord injury (SCI). We report the surgical outcomes in patients with high-level SCI who underwent transurethral incision of the bladder neck (TUI-BN). Twenty-two patients with SCI at or above the mid-thoracic level who presented with voiding dysfunction due to BND with different types of DSD received TUI-BN. Surgical outcome was determined by comparing preoperative with postoperative urodynamic parameters and clinical presentations. Satisfactory outcome was defined as having improvement of AUA/IPSS quality-of-life (QoL) index by >or=2. Among the patients, 19 (86.4%) were men and 3 (13.6%) were women. Thirteen patients had cervical and nine had thoracic SCI. Postoperatively, spontaneous voiding by abdominal triggering with an open urethral sphincter was noted in 19 patients (86%) and AD had resolved in 15 patients (88.2%). Detrusor pressure decreased significantly in 9 patients who had a high voiding pressure at baseline, and increased significantly in 13 patients who showed impaired detrusor contractility preoperatively. Eighteen patients (82%) reported satisfactory outcome, increased maximum flow rate (Q(max)), decrease in postvoid residual (PVR) postoperatively. In addition, 82% of the patients were catheter free or reported a decrease in the frequency of clean intermittent catheterization after TUI-BN. TUI-BN is effective in restoring spontaneous voiding, increasing Q(max), and decreasing PVR in high-level SCI patients. TUI-BN also leads to improvement in reducing bladder outlet resistance, reduction in occurrence of AD episodes, and improvement in QoL.

Evaluation of a wireless wearable tongue–computer interface by individuals with high-level spinal cord injuries

The tongue drive system (TDS) is an unobtrusive, minimally invasive, wearable and wireless tongue–computer interface (TCI), which can infer its users' intentions, represented in their volitional tongue movements, by detecting the position of a small permanent magnetic tracer attached to the users' tongues. Any specific tongue movements can be translated into user-defined commands and used to access and control various devices in the users' environments. The latest external TDS (eTDS) prototype is built on a wireless headphone and interfaced to a laptop PC and a powered wheelchair. Using customized sensor signal processing algorithms and graphical user interface, the eTDS performance was evaluated by 13 naive subjects with high-level spinal cord injuries (C2–C5) at the Shepherd Center in Atlanta, GA. Results of the human trial show that an average information transfer rate of 95 bits/min was achieved for computer access with 82% accuracy. This information transfer rate is about two times higher than the EEG-based BCIs that are tested on human subjects. It was also demonstrated that the subjects had immediate and full control over the powered wheelchair to the extent that they were able to perform complex wheelchair navigation tasks, such as driving through an obstacle course.

Compensatory mechanisms to maintain blood pressure in paraplegic rats: Implication of central tachykinin NK-1 and NK-3 receptors?

People with high level spinal cord injury (SCI) suffer from both hypotension and spontaneous hypertension due to loss of supraspinal control of spinal sympathetic outflow. Few reports have addressed whether any changes occur in central regulation of blood pressure (BP) and heart rat (HR) at the supraspinal level. Central tachykinin NK-1 and NK-3 receptors are located in many cardiovascular areas in the brain and are known to modulate BP and HR. This study examined the intracerebroventricular (i.c.v.) effects of the selective NK-1 receptor agonist [Sar(9), Met(O(2))(11)]SP (65pmol, n=6) and NK-3 receptor agonist senktide (650pmol, n=6) on mean arterial pressure (MAP) and HR before and after complete spinal cord transection at thoracic level 4 (T4). [Sar(9), Met(O(2))(11)]SP evoked increases in MAP and HR which were still present 4days after the T4 SCI. Further analysis using the beta(1)-adrenoceptor antagonist atenolol (10mgkg(-1)) revealed an increased contribution of HR in the MAP increase after SCI. For senktide, 2 and 5weeks after T4 SCI, the rise in MAP induced by senktide was significantly increased in magnitude and was similar to a normal response at 8weeks. These effects were accompanied by a bradycardia, which was still present and amplified at 8weeks. Our results reveal a transient potentiation of the senktide-mediated MAP effect and a greater contribution of the HR in MAP increase by [Sar(9), Met(O(2))(11)]SP in T4 transected rats. Although the significance of these changes remains to be established. This suggest a reorganization of supraspinal mechanisms regulating BP and HR after a high level SCI. Central NK-1 and NK-3 receptors might therefore contribute to the maintenance of MAP following high thoracic SCI.

Characterization of neural activity recorded from the descending tracts of the rat spinal cord

A multi-electrode array (MEA) was implanted in the dorsolateral funiculus of the cervical spinal cord to record descending information during behavior in freely moving rats. Neural signals were characterized in terms of frequency and information content. Frequency analysis revealed components both at the range of local field potentials and multi-unit activity. Coherence between channels decreased steadily with inter-contact distance and frequency suggesting greater spatial selectivity for multi-unit activity compared to local field potentials. Principal component analysis (PCA) extracted multiple channels of neural activity with patterns that correlated to the behavior, indicating multiple dimensionality of the signals. Two different behaviors involving the forelimbs, face cleaning and food reaching, generated neural signals through distinctly different combination of neural channels, which suggested that these two behaviors could readily be differentiated from recordings. This preliminary data demonstrated that descending spinal cord signals recorded with MEAs can be used to extract multiple channels of command control information and potentially be utilized as a means of communication in high level spinal cord injury subjects.