BACKGROUND:Intracortical microstimulation (ICMS) of the somatosensory cortex activates neurons around the stimulating electrodes and can elicit tactile sensations. OBJECTIVE:It is not clear how the direct activation of cortical neurons influences their ability to process additional tactile inputs originating from the skin. METHODS:In a human implanted with chronic microelectrode arrays in both left and right somatosensory cortices, we presented mechanical vibration to the skin while simultaneously delivering ICMS and quantified the effects of combined mechanical and electrical stimulation on tactile perception. RESULTS:We found that subthreshold ICMS enhanced sensitivity to touch on the skin, as evidenced by a reduction in vibrotactile detection thresholds (median: 1.5 dB), but subthreshold vibration did not systematically impact the detectability of ICMS. Suprathreshold vibration led to an increase in ICMS thresholds (median: 2.4 dB) but suprathreshold ICMS had little impact on vibrotactile thresholds. The ICMS-induced enhancement of vibrotactile sensitivity was location dependent with the effect size decreasing as the projected field of the stimulating electrode and the locus of vibratory stimulation became farther apart. CONCLUSION:These results demonstrate that targeted microstimulation of cortex alone can focally enhance tactile sensitivity, potentially enabling restoration or strengthening of retained tactile sensations after injury.

The clinical success of brain computer interfaces (BCI) depends on overcoming both biological and material challenges to ensure a long-term stable connection for neural recording and stimulation. This study systematically quantified damage that microelectrodes sustained during chronical implantation in three people with tetraplegia for 956–2130 days. Using scanning electron microscopy (SEM), we imaged 980 microelectrodes from eleven Neuroport arrays tipped with platinum (Pt, n = 8) and sputtered iridium oxide film (SIROF, n = 3). Arrays were implanted/explanted from posterior parietal, motor and somatosensory cortices across three clinical sites (Caltech/UCLA, Caltech/USC, APL/Johns Hopkins). From the electron micrographs, we quantified and correlated physical damage with functional outcomes measured in vivo, prior to explant (recording quality, noise, impedance and stimulation ability).Despite greater physical degradation, SIROF electrodes were twice as likely to record neural activity than Pt (measured by SNR). For SIROF, 1 kHz impedance significantly correlated with all physical damage metrics, recording metrics, and stimulation performance, suggesting a reliable measurement of in vivo degradation. We observed a new degradation type, primarily on stimulated electrodes (“pockmarked” vs “cracked”) electrodes; however, no significant degradation due to stimulation or amount of charge delivered. We hypothesize erosion of the silicon shank accelerates damage to the electrode / tissue interface, following damage to the tip metal.These findings link quantitative measurements to the microelectrodes’ physical condition and their capacity to record/stimulate. These data could lead to improved manufacturing processes or novel electrode designs to improve long-term performance of BCIs, making them vitally important as multi-year clinical trials of BCIs are becoming more common. Statement of significance Long-term performance stability of the electrode-tissue interface is essential for clinical viability of brain computer interface (BCI) devices; currently, materials degradation is a critical component for performance loss. Across three human participants, ten micro-electrode arrays (plus one control) were implanted for 956–2130 days. Using scanning electron microscopy (SEM), we analyzed degradation of 980 electrodes, comparing two types of commonly implanted electrode tip metals: Platinum (Pt) and Sputtered Iridium Oxide Film (SIROF). We correlated observed degradation with in vivo electrode performance: recording (signal-to-noise ratio, noise, impedance) and stimulation (evoked somatosensory percepts). We hypothesize penetration of the electrode tip by biotic processes leads to erosion of the supporting silicon core, which then accelerates further tip metal damage. These data could lead to improved manufacturing processes or novel electrode designs towards the goal of a stable BCI electrical interface, spanning a multi-decade participant lifetime.

Haptic feedback can play a useful role in rehabilitation and brain-computer interface applications by providing users with information about their system or performance. One challenge delivering tactile stimulation is not knowing how the haptic sensation is actually perceived, irrespective of the stimulation amplitude, during real-world use and beyond controlled psychophysical experiments. In a participant with chronically implanted electrocorticography arrays, we observed that perceived intensity of haptic vibration on the fingertips was represented in the high-gamma (HG) frequency band (70-170 Hz) in the somatosensory cortex. The five fingers of the participant's right hand were represented by distinct channels in the implanted array and modulated by the vibration amplitude at the fingertips. Although it reliably varied with the vibration amplitude, we found that HG activity had a stronger relationship with the actual perceived intensity of haptic stimulation (r s = 0.45, p < 10 -6). These results demonstrate that neural signals, specifically HG activity, in the somatosensory cortex can represent qualities of perceived haptic intensity regardless of the stimulation amplitude, which could enable a new way to passively quantify or ensure effective haptic feedback to a user.

Invasive brain-machine interfaces can help restore function through the control of external devices while the addition of intracortical microstimulation (ICMS) can elicit sensations of touch and help provide further benefits for individuals living with sensorimotor deficits. However, the extent of tactile information that can be conveyed through ICMS has not been fully explored. In a human participant with spinal cord injury and chronically implanted microelectrode arrays, we used ICMS to the somatosensory cortex to provide grip force feedback in the hands during grasping of objects with varying stiffness with a robotic arm. Using only ICMS-evoked touch sensations, the participant was able to identify between two and three objects with an accuracy of 92% and 67%, respectively. In a compliant grasping task with the goal of grasping a delicate object without crushing it, objects were deformed on average only 2.8 mm with ICMS-based touch feedback compared to 8.7 mm without. These results demonstrate that ICMS-evoked touch sensations to the hands can be used to provide force-based feedback for perceiving object properties and enable more precise grasping during closed-loop control of a robotic limb through a cortical interface.

ObjectiveTargeted transcutaneous electrical nerve stimulation (tTENS) is a non-invasive neural stimulation technique that involves activating sensory nerve fibers to elicit tactile sensations in a distal, or referred, location. Though tTENS is a promising approach for delivering haptic feedback in virtual reality or for use by those with somatosensory deficits, it was not known how the perception of tTENS might be influenced by changing wrist position during sensorimotor tasks.ApproachWe worked with 12 able-bodied individuals and delivered tTENS by placing electrodes on the wrist, thus targeting the ulnar, median, and radial nerves, and eliciting tactile sensations in the hand. We recorded perceptual data across three wrist postures: neutral, 45° extension, and 45° flexion. For each posture, the participants drew where they perceived the elicited percepts on a map of the hand. They verbally reported the quality of the percepts in their own words. We also varied the pulse amplitude and width of the stimulation to generate a strength-duration curve, from which we extracted the rheobase current and chronaxie time. Linear mixed models were run on the slope and intercept of the linear fit between pulse width and pulse amplitude to investigate effects of gender, posture, and electrode placement.Main resultsAs wrist posture changed, sensation quality was modulated for half of the participants, and percept location changed for 11/12 participants. The rheobase, chronaxie, and percept sizes were influenced by wrist posture, but the direction of these changes varied by participant and therefore the effect was not systematic. The statistical models indicated interactions between posture and electrode placement, as well as an effect of gender.SignificanceIf using tTENS with electrodes placed on the wrist to convey haptic feedback during sensorimotor tasks, in which wrist posture will likely change, it may be important to characterize perception on an individual basis.

Extended reality (XR) systems leverage multisensory feedback to convey environmental states to the user. Haptic feedback can improve immersivity and performance when operating in XR environments, but it is rarely used in commercial systems. We sought to investigate the usability of haptic feedback displaced to the forearm in a challenging XR manipulation task, in which participants grasped and transported breakable virtual eggs from one side of a virtual table to another. Several vibrotactile feedback conditions were tested, including variations in location (i.e., fingertips vs. forearm) and channel count. We found that introducing haptic feedback improved participants' accuracy, but most performed the task more slowly. There was not a significant difference in success rate or trial completion time between vibration locations. Increasing fingertip channel count improved success rate by 51% without hindering trial completion time. When participants were asked for their preferred feedback modality, 69% preferred fingertip vibration, while 31% preferred forearm vibration. In conditions with haptic feedback, 11 of the 16 participants performed the task more slowly when they received vibration in their preferred location. Overall, these results provide promise for haptic feedback delivery that is spatially removed from the hand and fingers in XR systems.

Multimodal sensory feedback from upper-limb prostheses can increase their function and usability. Here we show that intuitive thermal perceptions during cold-object grasping with a prosthesis can be restored in a phantom hand through targeted nerve stimulation via a wearable thin-film thermoelectric device with high cooling power density and speed. We found that specific regions of the residual limb, when thermally stimulated, elicited thermal sensations in the phantom hand that remained stable beyond 48 weeks. We also found stimulation sites that selectively elicited sensations of temperature, touch or both, depending on whether the stimulation was thermal or mechanical. In closed-loop functional tasks involving the identification of cold objects by amputees and by non-amputee participants, and compared with traditional bulk thermoelectric devices, the wearable thin-film device reliably elicited cooling sensations that were up to 8 times faster and up to 3 times greater in intensity while using half the energy and 1/600th the mass of active thermoelectric material. Wearable thin-film thermoelectric devices may allow for the non-invasive restoration of thermal perceptions during touch. Intuitive thermal perceptions during cold-object grasping with a prosthesis can be restored in a phantom hand through targeted nerve stimulation via a wearable thin-film thermoelectric device with high cooling power density and speed.

Objective: Targeted transcutaneous electrical nerve stimulation (TENS) is a non-invasive neural stimulation technique that involves activating sensory nerve fibers to elicit tactile sensations in a distal, or referred, location. Though TENS is a promising approach for delivering haptic feedback for those with somatosensory deficits, it was not known how the perception of TENS might be influenced by changing wrist position during sensorimotor tasks. Approach: We worked with 12 able-bodied individuals and delivered TENS by placing electrodes on the wrist, thus targeting the ulnar and median nerves, and eliciting tactile sensations in the hand. We recorded perceptual data across three wrist postures: neutral, 45{degrees} extension, and 45{degrees} flexion. For each posture, the participants drew where they perceived the elicited percepts on a map of the hand. They verbally reported the quality of the percepts in their own words. We also varied the pulse amplitude and width of the stimulation to generate a strength-duration curve, from which we extracted the rheobase current and chronaxie time. Linear mixed models were run on the slope and intercept of the linear fit between pulse width and pulse amplitude to investigate effects of gender, posture, and electrode placement. Main results: As wrist posture changed, sensation quality was modulated for half of the participants, and percept location changed for 11/12 participants. There were no major changes in the surface area of the elicited percepts. The rheobase and chronaxie values were influenced by wrist posture, but the direction of these changes varied by participant and therefore the effect was not systematic. The statistical models indicated interactions between posture and electrode placement, as well as an effect of gender. Significance: If using TENS to convey haptic feedback in sensorimotor tasks, in which wrist posture will likely change, it may be important to characterize resulting perceptual changes for individual users.

Complete sensorimotor integration and user acceptance of a neural prosthesis relies on system embodiment the incorporation of an external system into one's own body schema and representation. Embodiment of neural prostheses is an ambiguous concept with limited approaches for quantifying human and machine integration in a meaningful way. In an attempt to understand human sensory integration with external systems, we measured neural activity in the somatosensory cortex of a participant with chronically implanted microelectrode arrays during sensory events tied to either a virtual robotic hand touching an object or a virtual lamp lighting up. Sensory stimulation was delivered using either skin vibration or intracortical microstimulation (ICMS) and was mapped to the virtual systems. Through the brain-machine interface, we observed quantifiable cortical activity corresponding to tactile sensations perceived during the virtual tasks and even during instances when neural stimulation was expected but not delivered, demonstrating the presence of sensory-related neural activity even in the absence of tactile stimulation. Evoked sensory expectation signals were also observed in the motor cortex, although at reduced amplitudes. Evoked cortical activity corresponding to expectation of a sensory input could serve as objective cortical markers for better understanding sensorimotor integration and perceptual experiences when connecting humans with external systems.

Objective Intuitively providing touch feedback from artificial hands to users with sensory loss remains a challenge. Although localized fingertip sensations can be evoked via intracortical microstimulation (ICMS), feedback is generally optimized using psychometric tasks rather than mimicking the cortical response to touch. Approach We created an anatomically-informed and participant-specific model of the human somatosensory cortex (S1) region with an implanted microelectrode array (MEA). We performed simultaneous stimulation-and-recording from the study participant S1 region to characterize cortical responses elicited by single ICMS pulses. Pulses were delivered to a set of pre-selected electrodes mapped to tactile receptive fields. We next performed a 2D (i.e., in the plane of the MEA probe tips) current source density (CSD) analysis of recorded cortical responses to inform cortical network model parameters on how ICMS activates neurons and lateral synaptic connections in the area of the S1 sampled by MEA electrodes. Using information from planar CSD profiles obtained from ground truth data, we reconstructed lateral connections in the S1 model needed to produce the desired responses to single ICMS pulses. The effect of multiple ICMS was then simulated in the biologically realistic cortical model and the results were validated against ground truth cortical responses from the study participant. Main results A high-resolution cortical network model, calibrated to produce the known cortical responses to single ICMS pulses delivered to individual electrodes, predicted with a reasonable accuracy the cortical response to ICMS pulses delivered simultaneously to multiple electrodes. Significance These preliminary results suggest that high-resolution biologically realistic cortical network models can potentially be reliable predictors of cortical response to a given pattern of ICMS presentations and therefore useful in designing biomimetic stimulation patterns.

Objective. Validating the ability for advanced prostheses to improve function beyond the laboratory remains a critical step in enabling long-term benefits for prosthetic limb users. Approach. A nine week take-home case study was completed with a single participant with upper limb amputation and osseointegration to better understand how an advanced prosthesis is used during daily activities. The participant was already an expert prosthesis user and used the Modular Prosthetic Limb (MPL) at home during the study. The MPL was controlled using wireless electromyography (EMG) pattern recognition-based movement decoding. Clinical assessments were performed before and after the take-home portion of the study. Data was recorded using an onboard data log in order to measure daily prosthesis usage, sensor data, and EMG data. Main results. The participant’s continuous prosthesis usage steadily increased ( p = 0.04, max = 5.5 h) over time and over 30% of the total time was spent actively controlling the prosthesis. The duration of prosthesis usage after each pattern recognition training session also increased over time ( p = 0.04), resulting in up to 5.4 h of usage before retraining the movement decoding algorithm. Pattern recognition control accuracy improved (1.2% per week, p < 0.001) with a maximum number of ten classes trained at once and the transitions between different degrees of freedom increased as the study progressed, indicating smooth and efficient control of the advanced prosthesis. Variability of decoding accuracy also decreased with prosthesis usage ( p < 0.001) and 30% of the time was spent performing a prosthesis movement. During clinical evaluations, Box and Blocks and the Assessment of the Capacity for Myoelectric Control scores increased by 43% and 6.2%, respectively, demonstrating prosthesis functionality and the NASA Task Load Index scores decreased, on average, by 25% across assessments, indicating reduced cognitive workload while using the MPL, over the nine week study. Significance . In this case study, we demonstrate that an onboard system to monitor prosthesis usage enables better understanding of how prostheses are incorporated into daily life. That knowledge can support the long-term goal of completely restoring independence and quality of life to individuals living with upper limb amputation.

Background: Intracortical microstimulation (ICMS) of somatosensory cortex can partially restore the sense of touch. Though ICMS bypasses much of the neuraxis, prior studies have found that conscious detection of touch elicited by ICMS lags behind the detection of cutaneous vibration. These findings may have been influenced by mismatched stimulus intensities, which can impact temporal perception. Objective: Evaluate the relative latency at which intensity-matched vibration and ICMS are perceived by a human participant. Methods: One person implanted with microelectrode arrays in somatosensory cortex performed reaction time and temporal order judgment (TOJ) tasks. To measure reaction time, the participant reported when he perceived vibration or ICMS. In the TOJ task, vibration and ICMS were sequentially presented and the participant reported which stimulus occurred first. To verify that the participant could distinguish between stimuli, he also performed a modality discrimination task, in which he indicated if he felt vibration, ICMS, or both. Results: When vibration was matched in perceived intensity to high-amplitude ICMS, vibration was perceived, on average, 48 ms faster than ICMS. However, in the TOJ task, both sensations arose at comparable latencies, with points of subjective simultaneity not significantly different from zero. The participant could discriminate between tactile modalities above chance level but was more inclined to report feeling vibration than ICMS. Conclusions: The latencies of ICMS-evoked percepts are slower than their mechanical counterparts. However, differences in latencies are small, particularly when stimuli are matched for intensity, implying that ICMS-based somatosensory feedback is rapid enough to be effective in neuroprosthetic applications. (C) 2022 The Authors. Published by Elsevier Inc.

BACKGROUND AND OBJECTIVES:The restoration of touch to fingers and fingertips is critical to achieving dexterous neuroprosthetic control for individuals with sensorimotor dysfunction. However, localized fingertip sensations have not been evoked via intracortical microstimulation (ICMS).METHODS:Using a novel intraoperative mapping approach, we implanted electrode arrays in the finger areas of left and right somatosensory cortex and delivered ICMS over a 2-year period in a human participant with spinal cord injury.RESULTS:Stimulation evoked tactile sensations in 8 fingers, including fingertips, spanning both hands. Evoked percepts followed expected somatotopic arrangements. The subject was able to reliably identify up to 7 finger-specific sites spanning both hands in a finger discrimination task. The size of the evoked percepts was on average 33% larger than a finger pad, as assessed via manual markings of a hand image. The size of the evoked percepts increased modestly with increased stimulation intensity, growing 21% as pulse amplitude increased from 20 to 80 µA. Detection thresholds were estimated on a subset of electrodes, with estimates of 9.2 to 35 µA observed, roughly consistent with prior studies.DISCUSSION:These results suggest that ICMS can enable the delivery of consistent and localized fingertip sensations during object manipulation by neuroprostheses for individuals with somatosensory deficits.CLINICALTRIALSGOV IDENTIFIER:NCT03161067.

Advances in intelligent robotic systems and brain-machine interfaces (BMI) have helped restore functionality and independence to individuals living with sensorimotor deficits; however, tasks requiring bimanual coordination and fine manipulation continue to remain unsolved given the technical complexity of controlling multiple degrees of freedom (DOF) across multiple limbs in a coordinated way through a user input. To address this challenge, we implemented a collaborative shared control strategy to manipulate and coordinate two Modular Prosthetic Limbs (MPL) for performing a bimanual self-feeding task. A human participant with microelectrode arrays in sensorimotor brain regions provided commands to both MPLs to perform the self-feeding task, which included bimanual cutting. Motor commands were decoded from bilateral neural signals to control up to two DOFs on each MPL at a time. The shared control strategy enabled the participant to map his four-DOF control inputs, two per hand, to as many as 12 DOFs for specifying robot end effector position and orientation. Using neurally-driven shared control, the participant successfully and simultaneously controlled movements of both robotic limbs to cut and eat food in a complex bimanual self-feeding task. This demonstration of bimanual robotic system control via a BMI in collaboration with intelligent robot behavior has major implications for restoring complex movement behaviors for those living with sensorimotor deficits.

Touch-like phantom limb sensations can be elicited through targeted transcutaneous electrical nerve stimulation (tTENS) in individuals with upper limb amputation. The corresponding impact of sensory stimulation on cortical activity remains an open question. Brain network research shows that sensorimotor cortical activity is supported by dynamic changes in functional connections between relevant brain regions. These groups of interconnected regions are functional modules whose architecture enables specialized function and related neural processing supporting individual task needs. Using electroencephalographic (EEG) signals to analyze modular functional connectivity, we investigated changes in the modular architecture of cortical large-scale systems when participants with upper limb amputations performed phantom hand movements before, during, and after they received tTENS. We discovered that tTENS substantially decreased the flexibility of the default mode network (DMN). Furthermore, we found increased interconnectivity (measured by a graph theoretic integration metric) between the DMN, the somatomotor network (SMN) and the visual network (VN) in the individual with extensive tTENS experience. While for individuals with less tTENS experience, we found increased integration between DMN and the attention network. Our results provide insights into how sensory stimulation promotes cortical processing of combined somatosensory and visual inputs and help develop future tools to evaluate sensory combination for individuals with amputations.

Understanding the cortical representations of movements and their stability can shed light on improved brain-machine interface (BMI) approaches to decode these representations without frequent recalibration. Here, we characterize the spatial organization (somatotopy) and stability of the bilateral sensorimotor map of forearm muscles in an incomplete-high spinal-cord injury study participant implanted bilaterally in the primary motor and sensory cortices with Utah microelectrode arrays (MEAs). We built representation maps by recording bilateral multiunit activity (MUA) and surface electromyography (EMG) as the participant executed voluntary contractions of the extensor carpi radialis (ECR), and attempted motions in the flexor carpi radialis (FCR), which was paralytic. To assess stability, we repeatedly mapped and compared left- and right-wrist-extensor-related activity throughout several sessions, comparing somatotopy of active electrodes, as well as neural signals both at the within-electrode (multiunit) and cross-electrode (network) levels. Wrist motions showed significant activation in motor and sensory cortical electrodes. Within electrodes, firing strength stability diminished as the time increased between consecutive measurements (hours within a session, or days across sessions), with higher stability observed in sensory cortex than in motor, and in the contralateral hemisphere than in the ipsilateral. However, we observed no differences at network level, and no evidence of decoding instabilities for wrist EMG, either across timespans of hours or days, or across recording area. While map stability differs between brain area and hemisphere at multiunit/electrode level, these differences are nullified at ensemble level.

Sensory stimulation elicits sensations in the phantom hand of individuals with upper limb amputation. The reinstated sensory information is important to improve phantom limb perception and motor performance. In this work, we aimed to characterize the cortical impact of sensory stimulation on sensorimotor integration in upper limb amputees. To this goal, we investigated dynamic functional connectivity computed from electroencephalogram (EEG) recorded while amputees executed phantom hand movements with and without sensory stimulation. We focused on the dynamic functional connections to the somatosensory system and discovered that non-invasive sensory stimulation induced increased speed of information transfer, shown by decreased temporal distance, and increased number of connections from the motor, somatosensory, and multisensory processing systems. We show that the cortical impact of sensory stimulation is manifested not only through functional activities related to the primary somatosensory system, but also those involving the secondary somatosensory system.

16 Background : Electrically stimulating the somatosensory cortex can partially restore the 17 sense of touch. Though this technique bypasses much of the neuroaxis, prior studies with 18 non-human primates have found that conscious detection of touch elicited by intracortical 19 microstimulation (ICMS) lags behind the detection of vibration applied to the skin. These 20 findings may have been influenced by a mismatch in stimulus intensity; typically, vibration 21 is perceived as more intense than ICMS, which can significantly impact temporal 22 perception. 23 Objective : The goal of this study was to evaluate the relative latency at which intensity- 24 matched vibration and ICMS are perceived in a human subject. 25 Methods : A human participant implanted with microelectrode arrays in somatosensory 1 cortex performed a reaction time task and a temporal order judgment (TOJ) task. In the 2 reaction time task, the participant was presented with ICMS or vibration and verbal 3 response times were obtained. In the TOJ task, the participant was sequentially 4 presented with a pair of stimuli – ICMS followed by vibration or vice versa – and reported 5 which stimulus occurred first. 6 Results : When ICMS and vibration were matched in perceived intensity, the reaction time 7 to vibration was ~50 ms faster than ICMS. However, in the TOJ task, ICMS and vibratory 8 sensations arose at comparable latencies, with points of subjective simultaneity that were 9 not significantly different from zero. 10 Conclusions : Because the perception of ICMS is slower than that of intensity-matched 11 vibration, it may be necessary to stimulate at stronger ICMS intensities (thus decreasing 12 reaction time) when incorporating ICMS sensory feedback into neural prostheses.

Objective. Full restoration of arm function using a prosthesis remains a grand challenge; however, advances in robotic hardware, surgical interventions, and machine learning are bringing seamless human-machine interfacing closer to reality. Approach. Through extensive data logging over 1 year, we monitored at-home use of the dexterous Modular Prosthetic Limb controlled through pattern recognition of electromyography (EMG) by an individual with a transhumeral amputation, targeted muscle reinnervation, and osseointegration (OI). Main results. Throughout the study, continuous prosthesis usage increased (1% per week, p < 0.001) and functional metrics improved up to 26% on control assessments and 76% on perceived workload evaluations. We observed increases in torque loading on the OI implant (up to 12.5% every month, p < 0.001) and prosthesis control performance (0.5% every month, p < 0.005), indicating enhanced user integration, acceptance, and proficiency. More importantly, the EMG signal magnitude necessary for prosthesis control decreased, up to 34.7% (p < 0.001), over time without degrading performance, demonstrating improved control efficiency with a machine learning-based myoelectric pattern recognition algorithm. The participant controlled the prosthesis up to one month without updating the pattern recognition algorithm. The participant customized prosthesis movements to perform specific tasks, such as individual finger control for piano playing and hand gestures for communication, which likely contributed to continued usage. Significance. This work demonstrates, in a single participant, the functional benefit of unconstrained use of a highly anthropomorphic prosthetic limb over an extended period. While hurdles remain for widespread use, including device reliability, results replication, and technical maturity beyond a prototype, this study offers insight as an example of the impact of advanced prosthesis technology for rehabilitation outside the laboratory.

Almost 100 years ago experiments involving electrically stimulating and recording from the brain and the body launched new discoveries and debates on how electricity, movement, and thoughts are related. Decades later the development of brain-computer interface technology began, which now targets a wide range of applications. Potential uses include augmentative communication for locked-in patients and restoring sensorimotor function in those who are battling disease or have suffered traumatic injury. Technical and surgical challenges still surround the development of brain-computer technology, however, before it can be widely deployed. In this review we explore these challenges, historical perspectives, and the remarkable achievements of clinical study participants who have bravely forged new paths for future beneficiaries.