Journal of NeuroEngineering and Rehabilitation

There are many alternative methods to joystick control for control of Electric Powered Wheelchairs for users with neuromuscular disabilities, such as muscular dystrophy, and spinal cord injuries, such as tetraplegia. However, these methods- which include the sip-and-puff method, head and neck movement, blinking, or tongue movement- hinder social interaction, and are therefore detrimental to user independence. In recent years, research has explored the use of Electromyography (EMG) signals from alternative muscles to control a powered wheelchair, consequently increasing the quality of life of these users. The Auricular Muscles (AM) may be suitable, as they are controlled separately from the facial nerve and are vestigial in humans, making them advantageous for powered wheelchair control for users with tetraplegia. Additionally, they are located around the ear, adding a level of cosmesis when designing wearable sensors and prosthesis. This paper extracts and implements two control strategies from current literature and, for the first time, compares them directly, demonstrating viable implementation approaches for an online EMG-based powered-wheelchair control system. A Support Vector Machine (SVM) was developed and various window lengths were compared, with the most accuracy and real-time effectiveness found at 300ms. A study with three participants demonstrates the feasibility of these methods of control as well as experimental results to guide the potential AM use.

AO_SCPLOWBSTRACTC_SCPLOWIn severely impaired stroke patients, implementing EMG-driven robot-assisted therapy requires the presence of sufficient residual EMG and a patient-specific detector for accurate and low-latency EMG detection. However, identifying such a detector is challenging, especially when the level of residual EMG in a given patient is unknown . This paper proposes an unsupervised approach to distinguish between EMG data when the patient is relaxed versus attempting a movement - the maximally separating detector. We investigated six different detector types and separation measures using EMG data from a previous randomized controlled trial. The results indicate that the approximate generalized likelihood ratio detector, along with the modified Hodges and modified Lidierth detectors, achieved the best separation. Using a subset of clinician annotated data to evaluate the detection performance, the modified Hodges detector employing the probability difference-sum ratio measure had the best detection performance in terms of detection accuracy and latency. Using the data from 30 participants, we propose a probability difference-sum ratio threshold of 0.7 for the modified Hodges detector to identify patients with sufficient residual EMG to trigger robotic assistance. From the results, we propose the use of modified Hodges detector along with a probability difference-sum ratio measure to learn the maximally separating detector for a given patient, which will screen the patient for sufficient residual EMG and provide a detector to trigger robotic assistance if sufficient EMG is present. The validation of this approach using a large dataset and investigating the quality of the human-machine interaction implemented with such a detector is warranted.

IntroductionDynamic modulation of grip occurs mainly within the major structures of the brain stem, in parallel with cortical control. This basic, but fundamental level of the brain, is robust to ill-formed feedback and to be useful, it may not require all the perceptual information of feedback we are consciously aware. This makes it viable candidate for using peripheral nerve stimulation (PNS), a form of tactile feedback that conveys intensity and location information of touch well but does not currently reproduce other qualities of natural touch. Previous studies indicate that PNS can integrate with the basic levels of the motor system at a pre-perceptual level and can be processed optimally in multisensory integration, but there is little evidence if PNS is used effectively for motor corrections. MethodsWe performed a study with an individual with a mid-radial upper limb difference who has cuff electrodes on his peripheral nerves to give him the sense of touch to perform an object movement over a barrier task. During this task we measured how the participant moved the object with a prosthetic hand in space, how they varied their grip force on the object, and how their muscle signals varied as force changed. We tested this with four different conditions: with and without stimulated tactile sensation combined with the user having control over force on an object or velocity of hand movement. ResultsGiven direct control of force, the participants output force significantly correlated with the pucks displacement up to the apex of the movement, but did not correlate afterwards. This indicated a trend of increasing force when lifting the puck, but no decrease when lowering it. In comparison, when the participant moved the puck with the intact hand, they had a small but significant increase in force when lifting the puck in half the cases, but always had a significantly decrease in force when lowering the puck. When the participant used a force controller with stimulation, the puck slipped or dropped significantly more times (p < 0.05) compared to the velocity controller with stimulated feedback. This result implied that when the participant intended to loosen their grip, the prosthesis opened instead, which would explain the lack of force reduction in the initial results. The analysis of intent decoded from EMG during use of the force controller shows that the participant intended to lower their grip force with or without stimulation when using a high shatter threshold, but when using a lower threshold, the stimulation gave the participant a better sense of where the shatter threshold was. With a low shatter force, the participant tended to modulate their muscle contractions to a constant level if they were given stimulation (no significant correlation with movement) or they generally increased their intended force towards the shatter force threshold without stimulated feedback. With a moderate shatter force, the participant kept a relatively constant contractile force with or without stimulation. In contrast the EMG analysis with the velocity controller has a mixed trend of increasing and decreasing muscle indicating no global desire to change their grip force in one direction or the other. Finally, analysis of the puck movement showed that the participants moved the puck higher above the barrier with the force controller compared to movements with the velocity controller (p < 0.001), but the addition of stimulation with either controller lowered the participants movements significantly closer to the barrier (p < 0.001). Stimulation may cause an instantaneous increase in confidence with a controller or create better positional awareness with either controller. DiscussionWhile the participant of this study did not show any significant output grip force changes during the object movement tasks, their decoded intent combined with the higher number of loosening events when using the force controller and with stimulation indicates they may have been trying to reduce their grip force during the task. This behavior matches with the force output of the participants intact hand. In order convert the participants intent into the correct output force, there needs to be changes to the overall design of modern prosthetic devices to allow for smaller grip force changes and changes to force within a static grip. Furthermore, improvements to the stimulation that amplify small changes in force and estimate the any slip forces on the fingertips will provide more useful signals to the participant.

Transradial amputation is the most common level of major upper limb amputation. Despite the growing availability of multifunctional prosthetic hands, users control of these hands and overall functional abilities remain limited. The combination of pattern recognition control and targeted muscle reinnervation (TMR) surgery, an innovative technique where amputated nerves are transferred to reinnervate new muscle targets in the residual limb, has been used to improve prosthesis control of individuals with more proximal upper limb amputation levels (i.e., shoulder disarticulation and transhumeral amputation). The goal of this study was to determine if similar prosthesis control improvements could be seen for individuals with amputations at the transradial level. Participants controlled 3-5 grips with a multi-articulating hand prosthesis under myoelectric pattern recognition control for at least 8 weeks at home pre- and post-TMR surgery. Users gained some significant functional control benefits using a multi-articulating hand prosthesis with pattern recognition at 9-12 months post-TMR surgery. Additionally, a majority of subjects noted an improvement in their residual limb and phantom limb sensations post-TMR. An additional offline EMG analysis showed a decrease in grip classification error post-TMR surgery compared to pre-TMR surgery.

When people talk, they move their hands to enhance meaning. Here we ask whether people spontaneously use their artificial limbs (prostheses) to gesture, and whether prosthesis gesture behaviour relates to everyday prosthesis use and perceived embodiment. One-handed participants with congenital and acquired hand loss and two-handed controls participated in gesture-facilitating tasks, measured using acceleration monitors and further validated with offline video coding. Everyday functional prosthesis use and perceived prosthesis embodiment were assessed using questionnaires. Perhaps surprisingly, one- and two-handed participants did not differ in the amount of gestures they produced. However, they did differ in their gesture profile. One-handers performed more, and bigger, movements with their intact hand while gesturing relative to their prosthesis, whereas two-handers produced more equal movements across hands. Importantly, one-handers who incorporated their prosthesis more into gesturing, that is -- produced gestures that were more similar to their two-handed counterparts -- also showed more frequent prosthesis use in day-to-day life. Although as a group, one-handers only marginally agreed that their prosthesis feels like a body-part, people reporting positive embodiment also showed great prosthesis habits, both for communication and daily function. We propose that measuring gesture behaviour in prosthesis-users can be used as an implicit and objective clinical tool to monitor and assess successful prosthesis adoption.

Providing user-focused, objective, and quantified metrics for prosthesis usability may help reduce the high (up to 50%) abandonment rates and accelerate the clinical adoption and cost reimbursement for new and improved prosthetic systems. We comparatively evaluated several physiological, behavioral, and subjective cognitive workload measures applied to upper-limb neuroprosthesis use. Users controlled a virtual prosthetic arm via surface electromyography (sEMG) and completed a virtual target control task at easy and hard levels of difficulty (with large and small targets, respectively). As indices of cognitive workload, we took behavioral (Detection Response Task; DRT) and electroencephalographic (EEG; parietal alpha and frontal theta power, and the P3 event-related potential) measures for one group (n = 1 amputee participant, n = 10 non-amputee participants), and electrocardiographic (ECG; low/high frequency heart-rate variability ratio) and pupillometric (task-evoked pupillary response) measures for another group (n = 1 amputee participant, n = 10 non-amputee participants), because all measures could not reasonably be recorded simultaneously. Participants of both groups also completed the subjective NASA Task-Load Index (TLX) survey. Ease of use, setup, piloting, and analysis complexity varied among measures. The DRT required minimal piloting, was simple to set up, and used straightforward analyses. ECG measures required moderate piloting, were simple to set up, and had somewhat complex analyses. Pupillometric measures required extensive piloting but were simple to set up and relatively simple to analyze. EEG measures required extensive piloting, extensive setup and equipment, careful monitoring, and moderately complex analyses. Across subjects, the DRT, low/high frequency heart-rate variability ratio, task-evoked pupillary response, and NASA TLX significantly differentiated between the easy and hard tasks, whereas EEG measures (alpha power, theta power, and P3 event-related potential) did not. Aside from the NASA TLX, the DRT was the easiest to use and most sensitive to cognitive load across and within subjects. Among physiological measures, we recommend ECG, pupillometry, and EEG/ERPs, in that order. This study provides the first evaluation of multiple objective and quantified cognitive workload measures during the same task with prosthesis use. User-focused cognitive workload assessments may increase our understanding of human interactions with advanced upper-limb neuroprostheses and facilitate their improvements and translation to real-world use. Significance StatementThe human arm is dexterous and able to sense objects it contacts. Restoring sensory and motor function to a person with limb loss presents multiple challenges and requires improvements in robotics, biological interfaces, decoding biological signals for prosthesis movement, and sensory restoration. The scientific and engineering communities have made progress toward restoring arm function through advanced neuroprostheses. However, most studies focus solely on task performance, and they typically employ artificial experimental paradigms in which the user can devote full attention to the task, which is often unrealistic for use in everyday activities. To develop neuroprostheses capable of restoring intuitive arm function, engineers and scientists must also consider the difficulty of use, or cognitive burden, of using the neuroprosthesis. Although many measures of cognitive workload have been developed, few studies directly interrogate cognitive workload during neuroprosthesis use. An engineer or scientist seeking to employ cognitive workload measures during neuroprosthesis use will likely wonder, as we did, which measures are most suitable for their needs. To address this question, we empirically assess the practical and functional merits and limitations of several physiological, behavioral, and subjective techniques to measure cognitive workload during use of an advanced prosthesis. We anticipate that these findings may influence other medical and consumer areas of human-computer interaction, such as virtual reality or exoskeleton use.

BackgroundHand rehabilitation is core to helping stroke survivors regain activities of daily living. Recent studies have suggested that the use of electroencephalography-based brain-computer interfaces (BCI) can promote this process. Here, we report the first systematic examination of the literature on the use of BCI-robot systems for the rehabilitation of fine motor skills associated with hand movement and profile these systems from a technical and clinical perspective. MethodsA search for January 2010-October 2019 articles using Ovid MEDLINE, Embase, PEDro, PsycINFO, IEEE Xplore and Cochrane Library databases was performed. The selection criteria included BCI-hand robotic systems for rehabilitation at different stages of development involving tests on healthy participants or people who have had a stroke. Data fields include those related to study design, participant characteristics, technical specifications of the system, and clinical outcome measures. Results30 studies were identified as eligible for qualitative review and among these, 11 studies involved testing a BCI-hand robot on chronic and subacute stroke patients. Statistically significant improvements in motor assessment scores relative to controls were observed for three BCI-hand robot interventions. The degree of robot control for the majority of studies was limited to triggering the device to perform grasping or pinching movements using motor imagery. Most employed a combination of kinaesthetic and visual response via the robotic device and display screen, respectively, to match feedback to motor imagery. Conclusion19 out of 30 studies on BCI-robotic systems for hand rehabilitation report systems at prototype or pre-clinical stages of development. Three studies report statistically significant improvements in functional recovery after stroke, but there is a need to develop a standard protocol for assessing technical and clinical outcomes so that the necessary evidence base on efficiency and efficacy can be developed.

OBJECTIVEReaching training with error augmentation (EA) has recently shown great promise for enhancing bimanual therapeutic training, using both robotic forces feedback (haptics) and a visually distorted display elements (graphics) to amplify motor learning. METHODSHere in a two-arm, randomized controlled trial we explored the effect of visual EA alone by visually shifting the paretic limbs cursor in the direction of error. We invited 38 chronic (> 8 months post injury) stroke survivors to practice bimanual reaching for approximately 40 minutes, 3 days per week, for three weeks. RESULTSArm motor section of the Fugl-Meyer (AMFM; maximum score 66 points) increased an average of 2.2 and retained to a follow-up evaluation 7-9 weeks (about 2 months) later (average 1.5). Clinically meaningful increase for AMFM for chronic stroke survivors is 5.2 points. No superiority was detected due to the EA treatment, but other measures on the composite abilities (range of motion, bimanual symmetry, and movement time) showed improvements favoring EA. CONCLUSIONSWhile removing robot forces led to smaller gains than previous work, such touch-free bimanual therapy may still prove to be an effective inexpensive automated rehabilitation tool for wider accessibility in therapy interventions. This study was registered at ClinicalTrials.gov (ID#NCT03300141).

Vibrotactile feedback is mechanical stimulation produced using actuators in contact with the body. The stimulation parameters (frequency, amplitude, location, duration) can be adjusted to produce a variety of sensations. By characterizing how users respond to different settings, interaction designers can create more usable and enjoyable haptic interfaces. This form of haptic feedback is being used widely for alerts, gaming, and simulation; however, emerging technologies in the fields of brain health and physical therapy are introducing new users to this stimulation. For applications using vibrotactile stimulation to advance, researchers are studying perceived sensations and affective response. However, these studies often focus on healthy, younger users. It is well known that older adults and those with acquired brain injury have different physiology and different perception than young adults. Here we present a set of vibrotactile signals to adults over 40 years old with and without history of stroke and query affective impression and experienced sensations. Signals on the palm and those with a changing stimulus location were associated with higher valence ratings, while low-amplitude signals showed lowest arousal. Users preferred stimulation that they could perceive, and they could not perceive most signals applied to the forearm. Reported sensations include tickle, tingling, and numbness. CCS ConceptsHuman-centered computing [-&gt;] User studies; Haptic devices; Ubiquitous and mobile devices.

BackgroundDyskinetic cerebral palsy (DCP) is dominated by dystonia and choreoathetosis, two movement disorders that are often simultaneously present and challenging to evaluate. Wearable technology shows potential for monitoring motor dysfunctions at high temporal resolution while expanding our understanding of DCP movement disorders. ObjectivesThis study aimed (i) to develop a methodology for automatic classification of dystonia and choreoathetosis combining inertial measurement units (IMUs) and random forests (RFs) during powered wheelchair driving in participants with DCP, (ii) to determine signature features for dystonia and choreoathetosis, and (iii) to optimise placement of body-worn IMUs in function of dystonia and choreoathetosis classification performance. MethodsUnconstrained movements of the arms and head during powered mobility (n = 5 DCP participants) were analysed to extract 111 time- and frequency-domain features in 5-second windows. RFs were then used to rank, select optimal features and classify dystonia and choreoathetosis, based on expert-annotated videos. ResultsClassification of dystonia and choreoathetosis for the neck, proximal and distal arm regions ranged within 67.8% - 80.7% accuracy. Reduced feature sets included between 19 - 73 features, as time-domain features were selected more prevalently in classifying both dystonia and choreoathetosis. IMUs on the distal arms predicted forehead dystonia and choreoathetosis with similar accuracy (74.5% - 81.2%) as using the forehead IMU. ConclusionsThis study increases insights into DCP by relating distinct IMU features to dystonia and choreoathetosis and by leveraging distal arm-placed IMUs to assess movement disorders in multiple body parts: distal arm, proximal arm and neck region.

ObjectiveA major challenge for controlling a prosthetic arm is communication between the device and the users phantom limb. We show the ability to enhance amputees phantom limb perception and improve movement decoding through targeted transcutaneous electrical nerve stimulation (tTENS). ApproachTranscutaneous nerve stimulation experiments were performed with four amputee participants to map phantom limb perception. We measured myoelectric signals during phantom hand movements before and after amputees received sensory stimulation. Using electroencephalogram (EEG) monitoring, we measure the neural activity in sensorimotor regions during phantom movements and stimulation. In one participant, we also tracked sensory mapping over 2 years and movement decoding performance over 1 year. Main resultsResults show improvements in the amputees ability to perceive and move the phantom hand as a result of sensory stimulation, which leads to improved movement decoding. In the extended study with one amputee, we found that sensory mapping remains stable over 2 years. Remarkably, sensory stimulation improves within-day movement decoding while performance remains stable over 1 year. From the EEG, we observed cortical correlates of sensorimotor integration and increased motor-related neural activity as a result of enhanced phantom limb perception. SignificanceThis work demonstrates that phantom limb perception influences prosthesis control and can benefit from targeted nerve stimulation. These findings have implications for improving prosthesis usability and function due to a heightened sense of the phantom hand.

Conventional therapy after stroke focuses on reducing physical impairments. However, the decisions that guide peoples movements may have far-reaching consequences towards recovery. We lack the tools to characterize these decisions. Recently, researchers have created a quantitative behavioral assessment of effort-based decision-making and applied it to some clinical populations. The purpose of this paper is to examine the feasibility of evaluating effort-based decision-making during walking after stroke. We recruited five neurotypical participants in an initial study. We conducted a subjective effort valuation on the neurotypical individuals with and without a knee immobilizer to simulate the biomechanics of reduced knee flexion during post-stroke gait. Participants cleared obstacles of varying heights during overground walking, followed by rating their perceived effort and then completing an effort choice paradigm to calculate subjective effort value. In a second experiment, we recruited five individuals with stroke to perform a similar protocol without an immobilizer during harnessed treadmill walking. We found that rated perceived effort increased monotonically with obstacle height across groups, that individuals could recall obstacle heights without cues, and that subjective effort value increased with knee immobilization in the control group as expected. We conclude that adapting an effort-based decision-making assessment to a walking context in people with stroke is feasible.

Existing prosthetic technologies for people with upper limb amputation are being adopted at moderate rates and unfortunately these devices are often abandoned. The aims of this study were to: 1) understand the current state of satisfaction with upper extremity prostheses, 2) solicit feedback about prosthetic technology and important device design criteria from amputees, clinicians, and device regulators, and 3) compare and contrast these perspectives to identify common or divergent priorities. Twenty-one adults with upper limb loss, 35 clinicians, and 3 regulators completed a survey on existing prosthetic technologies and a conceptual sensorimotor prosthesis driven by implanted myoelectric electrodes with sensory feedback provided via stimulation of dorsal root ganglion. User and clinician ratings of satisfaction with existing prosthetic devices were similar. While amputees, clinicians, and regulators were similarly accepting of technology in general, amputees were most accepting of the proposed implantable sensorimotor prosthesis. Overall, stakeholders valued user-centred outcomes such as individualized task goals, improved quality of life, device reliability, and user safety; a large emphasis was put on these last two outcomes by regulators. The results of this study provide insight into the priorities of amputees, clinicians, and regulators that will inform future upper-limb prosthetic design and clinical trial protocol development.

This study aimed to develop a novel rehabilitative approach for post-stroke hand movement using a simple detached robotic hand and synergistic torso muscle activities for reaching and to perform a pilot test on its functionality and feasibility. In reference to a mental practice that does not activate hand muscles, enhanced cognitive engagement would be achieved without hand activation using the externally present, visible, and audible robotic hand by activating the non-hand muscles associated with hand function. A simple and low-cost robotic hand was developed and placed distal to the hidden resting hand as if it were a functional extended hand. The opening and closing motions of the detached robotic hand were controlled by electromyogram of the anterior and posterior torso muscles associated with reaching and retrieving while providing visual and auditory feedback. The functionality of the developed system was confirmed on the repeatability of the range of duration, excursion, and response time with low variability within an acceptable range. An able-bodied adult and five mildly impaired stroke survivors embodied the detached robotic hand by successfully controlling it with or without concurrent testing of their biological finger. In the concurrent finger tests, increased reactive force and hand muscle activity were observed in most participants. These observations confirmed that the developed approach that controls a detached robotic hand with reaching-associated torso muscles is functional and applicable to stroke survivors with and without involving the biological human hand. The robotic hand system detached from the user and controlled by the voluntary effort of their reaching-associated torso muscles has enabled future studies to examine the efficacy of synergistic muscle-robot interaction as a potential rehabilitation tool.

ObjectiveStartReact elicits faster, larger, and more appropriate muscle activation in stroke survivors but has been only cursorily studied to date during multi-jointed reaching. Our objective was to evaluate StartReact on unrestricted, two-dimensional point-to-point reaching tasks post-stroke. MethodData from 23 individuals with stroke was collected during point-to-point reaching. Voluntary and StartReact trials were compared between mild, severe/moderate, and the unimpaired arm. ResultsStartReact showed an increase in probability of muscle activity, larger muscle activity amplitude and faster muscle activity onset. Despite changes in muscle activity, metrics of movement (distance, final error, linear deviation) were largely the same between StartReact and Voluntary trials except in severe/moderate stroke who had larger reaching distances during StartReact. ConclusionWhile StartReact impacted many metrics of muscle activity, the most profound effect was on probability of muscle activity increasing 34% compared to Voluntary which allowed severe/moderate subjects to increase reaching distance but did not translate to decrease in final error suggesting that the additional movement was not always directed towards the appropriate target. SignificanceThese results indicate that SR has the capacity to activate paralyzed muscle in severe/moderate patients, but future studies are needed to explore the possible use of SR in the rehabilitation.

BackgroundFunctional electrical stimulation (FES) has been recognized for decades as a method to retrain the motor system after stroke. Benefits of FES rehabilitation can be enhanced by combining task-oriented therapy, dubbed FES therapy (FEST). Furthermore, by synchronizing FES with the users volitional motor intention and incorporating multiple trained tasks FES can be better integrated into common task-oriented rehabilitation practice. Using wearable FES technology, we tested therapy incorporating these elements in two chronic stroke survivors. MethodsOur group has developed the NeuroLife(R) Sleeve, a wearable forearm sleeve that contains a high-density grid of embedded FES electrodes, that may be controlled by an operator or by the wearers own electromyographic (EMG) signals. During eight weeks of FEST, intention-driven FES enabling multiple movements was delivered via operator control twice weekly and EMG control once weekly. ResultsAt the end of the therapy period, subjects A and B had both improved their scores: Box and Blocks Test (A: +5, B: +7), the Action Arm Research Test (A: +7, B: +12), the Fugl Meyer Upper Extremity section (A: +11, B: +9), and the 9-Hole Peg Test (A: 158 sec, B: 54 sec, both previously unable). All score improvements persisted over the 10-week follow-up period despite greatly reduced (>80%) effective dose of FES. ConclusionsThis case series provides additional evidence that intention-driven FEST drives long-lasting motor recovery in chronic stroke survivors. The NeuroLife Sleeve enabled this therapy through the easily donned wearable sleeve interface, control schemes for pairing FES with motor intention, and efficient transitions between tasks with programmable FES placement and parameters.

The use of immersive virtual reality (VR) is gaining traction among the scientific community as it opens great opportunities in the field of rehabilitation. By making use of video game mechanics and Brain computer interface (BCI) that is based on electroencephalography (EEG) signals, patients undergoing neurorehabilitation can be more engaged in rehabilitation training. This paper reviews the available literature which uses BCI and VR in game rehabilitation and analyses the gaming elements and brain machine interfaces (BMI) used in each study. Four databases (IEEE Xplore, PubMed, Web of Science, Scopus) from inception until October 2023 were queried using a comprehensive searching strategy and then screened by two independent reviewers. A total of 18 articles were found eligible for qualitative synthesis. These are the main findings: (1) A diverse participant demographic spanned age and health conditions; (2) Oculus Rift has gained prominence as a VR device, replacing older CAVE systems; (3) All surveyed studies unanimously relied on the Motor Imagery (MI) paradigm, reflecting its importance in neuro motor rehabilitation and neuroplasticity; (4) Rehabilitation games displayed varied characteristics, emphasizing scoring, embodiment, and customization. Notably, the lack of gamification elements in some games suggests an area for potential enhancement and future research.

Recent reports have revealed that downward gazing enhances postural control. The mechanism underlying this phenomenon is currently unknown, yet there are several plausible explanations. In this study, we attempt to provide evidence to support the hypothesis that this effect is primarily derived from altered visual flow caused by gazing down. To this end, we quantified standing postural sway of 20 healthy participants and 20 people with stroke who were instructed to stand as still as possible under different conditions: while gazing forward and gazing down, with their eyes open and eyes closed. Both the horizontal gaze angle and the lack of visual input had a negative effect on participants ability to attenuate their body sway. Yet, the effect of gaze angle was constant regardless of the presence or absence of visual input. Also, people with stroke swayed more than their healthy counterparts and were more sensitive to the effect of gaze angle, but not to that of visual input. The results of this study indicate that downward gazing enhances postural control even in the absence of visual input and do not support our main hypothesis. Also, it seems that the effect of downward gazing on postural control is greater in unstable people (people with stroke) than that observed in healthy adults, which might explain less stable individuals tendency to gaze down while walking. Furthermore, these results might suggest that downward gazing behavior does not necessarily indicate an attempt to acquire visual information of any kind but instead serves to modulate some other sensory input helpful for postural control.

PurposeStroke is a leading cause of disability worldwide with improved treatments leading to higher survival rates and a greater demand for post-stroke rehabilitation. Technological rehabilitation solutions show promise to meet this growing need, but for maximum impact they must be accessible and affordable. To inform the development of low-cost virtual reality (VR) rehabilitation systems, here we assess the feasibility of motor amplification, an effective stroke treatment solution, on a low-cost controller-free system. DesignWe developed the REVIVE system, a VR stroke rehabilitation system operating on the standalone Meta Quest line of Head Mounted Displays which are wireless, low cost, and require no external hardware. Hand tracking, voice recognition and an automated motor amplification algorithm enable accessible engagement for users with a range of physical and cognitive abilities. An animated coach in the virtual environment guides users through gamified exercises which simulate activities of daily living and functional movements. We tested the system with 60 healthy young adults in a simulated stroke rehabilitation session, with a primary goal of validating the feasibility of the controller-free amplification feature. FindingsUsers reported minimal visually induced motion sickness even when experiencing the visuomotor perturbation generated by amplification, and more positive attitudes toward VR technology after the experience. Additionally, we provide a normative dataset for several REVIVE tasks to serve as a healthy baseline for future clinical applications. ValueOur findings suggest that this affordable consumer-grade system, suitable for home or clinical use, has considerable potential to improve access to post-stroke rehabilitation services.

BackgroundSpinal cord injuries significantly impair patients ability to perform daily activities independently. While cortically implanted brain-computer interfaces (BCIs) offer high communication bandwidth to assist and rehabilitate these patients, their invasiveness and long-term stability limit broader adoption. MethodsWe developed a minimally invasive BCI with 8 chronic epidural electrodes above primary sensorimotor cortex to restore hand functions of tetraplegia patients. With wireless powering and neural data transmission, this system enables real-time BCI control of hand movements and hand function rehabilitation in home use. A complete spinal cord injury (SCI) patient with paralyzed hand functions was recruited in this study. ResultsOver a 9-month period of home use, the patient achieved an average grasping detection F1-score of 0.91, and a 100% success rate in object transfer tests, with this minimally invasive BCI and a wearable exoskeleton hand. This system allowed the patient to perform eating, drinking and other daily tasks involving hand functions. Additionally, the patient showed substantial neurological recovery through consecutive BCI training, regaining the ability to hold objects without BCI. The patient exhibited a 5-point improvement in upper limb motor scores and a 27-point increase in the action research arm test (ARAT). A maximal increase of 12.7 V was observed in the peak of somatosensory evoked potential (SEP), which points to a considerable recovery in impaired spinal cord connections. Moreover, a high-frequency component (200-300 Hz) in SEP that was initially undetectable gradually emerged and became significant, indicating notable reorganization of the underlying neural circuits. ConclusionsIn a tetraplegia patient with complete spinal cord injury, an epidural minimally invasive BCI assisted the patients hand grasping to perform daily tasks, and 9-month consecutive BCI use significantly improved the hand functions.