Functional Hand Movements Research Articles

Identifying alterations in hand movement coordination from chronic stroke survivors using a wearable high-density EMG sleeve

Objective.Non-invasive, high-density electromyography (HD-EMG) has emerged as a useful tool to collect a range of neurophysiological motor information. Recent studies have demonstrated changes in EMG features that occur after stroke, which correlate with functional ability, highlighting their potential use as biomarkers. However, previous studies have largely explored these EMG features in isolation with individual electrodes to assess gross movements, limiting their potential clinical utility. This study aims to predict hand function of stroke survivors by combining interpretable features extracted from a wearable HD-EMG forearm sleeve.Approach.Here, able-bodied (N= 7) and chronic stroke subjects (N= 7) performed 12 functional hand and wrist movements while HD-EMG was recorded using a wearable sleeve. A variety of HD-EMG features, or views, were decomposed to assess alterations in motor coordination.Main Results.Stroke subjects, on average, had higher co-contraction and reduced muscle coupling when attempting to open their hand and actuate their thumb. Additionally, muscle synergies decomposed in the stroke population were relatively preserved, with a large spatial overlap in composition of matched synergies. Alterations in synergy composition demonstrated reduced coupling between digit extensors and muscles that actuate the thumb, as well as an increase in flexor activity in the stroke group. Average synergy activations during movements revealed differences in coordination, highlighting overactivation of antagonist muscles and compensatory strategies. When combining co-contraction and muscle synergy features, the first principal component was strongly correlated with upper-extremity Fugl Meyer hand sub-score of stroke participants (R2= 0.86). Principal component embeddings of individual features revealed interpretable measures of motor coordination and muscle coupling alterations.Significance.These results demonstrate the feasibility of predicting motor function through features decomposed from a wearable HD-EMG sleeve, which could be leveraged to improve stroke research and clinical care.

Decoding hand and wrist movement intention from chronic stroke survivors with hemiparesis using a user-friendly, wearable EMG-based neural interface

ObjectiveSeventy-five percent of stroke survivors, caregivers, and health care professionals (HCP) believe current therapy practices are insufficient, specifically calling out the upper extremity as an area where innovation is needed to develop highly usable prosthetics/orthotics for the stroke population. A promising method for controlling upper extremity technologies is to infer movement intention non-invasively from surface electromyography (EMG). However, existing technologies are often limited to research settings and struggle to meet user needs.ApproachTo address these limitations, we have developed the NeuroLife® EMG System, an investigational device which consists of a wearable forearm sleeve with 150 embedded electrodes and associated hardware and software to record and decode surface EMG. Here, we demonstrate accurate decoding of 12 functional hand, wrist, and forearm movements in chronic stroke survivors, including multiple types of grasps from participants with varying levels of impairment. We also collected usability data to assess how the system meets user needs to inform future design considerations.Main resultsOur decoding algorithm trained on historical- and within-session data produced an overall accuracy of 77.1 ± 5.6% across 12 movements and rest in stroke participants. For individuals with severe hand impairment, we demonstrate the ability to decode a subset of two fundamental movements and rest at 85.4 ± 6.4% accuracy. In online scenarios, two stroke survivors achieved 91.34 ± 1.53% across three movements and rest, highlighting the potential as a control mechanism for assistive technologies. Feedback from stroke survivors who tested the system indicates that the sleeve’s design meets various user needs, including being comfortable, portable, and lightweight. The sleeve is in a form factor such that it can be used at home without an expert technician and can be worn for multiple hours without discomfort.SignificanceThe NeuroLife EMG System represents a platform technology to record and decode high-resolution EMG for the real-time control of assistive devices in a form factor designed to meet user needs. The NeuroLife EMG System is currently limited by U.S. federal law to investigational use.

Design and fabrication of a custom molded splint for tetraplegics

BackgroundThe key rehabilitation goal for cervical cord injury is promoting functional hand movement. Patients with mid to low-level cervical spinal cord injury can achieve the useful tenodesis grasp with the assistance of upper extremity orthosis. In this study, a custom molded writing device was fabricated and applied on cervical cord injured patients with the aim of hand rehabilitation. MethodsA total of fourteen individuals with cervical spinal cord injury at C6–C7 level were recruited for the study. They were divided into two groups, where the experimental group was prescribed with the custom molded writing device and the standard-of-care group was prescribed with the traditionally available writing device. The performance of the devices was evaluated using the Quest 2.0 questionnaire and the quality of writing after an intervention time of 4 weeks. ResultThe group that used custom molded writing device performed comparatively better when compared to the conventional design. The data showed a significant difference with average QUEST scores of 4.47 ± 0.33 for the group using the wrist-driven writing device and 3.04 ± 0.70 for group using the conventional design. For better understanding of the device's performance, the writing with both the splints was also assessed. ConclusionA writing device using the tenodesis grasp was fabricated to rehabilitate the writing skills of individuals with cervical spinal cord injuries. The performance of the device provided a favorable result indicating to elaborate the study for future references.

Hand model with dependency constrained joints for applications in rehabilitation robotics

Aim: This work presents a method for developing a simplified but efficient model of the complex human hand kinematics with the aim of its implementation in rehabilitation robotics. Material and methods: The approach incorporates modularity by simplifying the available model comprising 24 degrees of freedom (DOFs) to 9 DOFs, with the introduction of additional joint coupling parameters specific to different grasp types. The effect of dependent joints to the ranges-of-motion (ROMs) of the model is investigated and compared to the anatomical one. The index, middle, ring and little finger solutions to forward and inverse kinematics problems are then acquired. The implementation of the model, based on the median male bones dimensions, is made available in the open-source Robot Operating System (ROS) framework. Results: By including additional four inclination angles per finger, the devised kinematic hand model encompasses also finger curvatures, resulting in significant positioning accuracy improvements compared to the conventional model. The used 3D spatial position improvement metrics are the mean absolute (MAE) and mean relative errors (MRE). The dependent joint position MAEs range from 0.22 to 0.34 cm, while MREs range from 2.8 and 3.5 %, whereas the highest absolute and relative errors during fingertip positioning can reach 0.5 cm and 10.5 %, respectively. Conclusion: The performed investigation allowed establishing that by modelling finger curvature and assuring the adaptability of the model to a variety of human hands and rehabilitation modalities through joint dependency, represents the best approach towards a relatively simple and applicable rehabilitation model with functional human-like hand movements.

Decomposition into dynamic features reveals a conserved temporal structure in hand kinematics

The human hand is a unique and highly complex effector. The ability to describe hand kinematics with a small number of features suggests that complex hand movements are composed of combinations of simpler movements. This would greatly simplify the neural control of hand movements. If such movement primitives exist, a dimensionality reduction approach designed to exploit these features should outperform existing methods. We developed a deep neural network to capture the temporal dynamics of movements and demonstrate that the features learned allow accurate representation of functional hand movements using lower-dimensional representations than previously reported. We show that these temporal features are highly conserved across individuals and can interpolate previously unseen movements, indicating that they capture the intrinsic structure of hand movements. These results indicate that functional hand movements are defined by a low-dimensional basis set of movement primitives with important temporal dynamics and that these features are common across individuals.

Activating effective functional hand movements in individuals with complete tetraplegia through neural stimulation

Individuals with complete cervical spinal cord injury suffer from a permanent paralysis of upper limbs which prevents them from achieving most of the activities of daily living. We developed a neuroprosthetic solution to restore hand motor function. Electrical stimulation of the radial and median nerves by means of two epineural electrodes enabled functional movements of paralyzed hands. We demonstrated in two participants with complete tetraplegia that selective stimulation of nerve fascicles by means of optimized spreading of the current over the active contacts of the multicontact epineural electrodes induced functional and powerful grasping movements which remained stable over the 28 days of implantation. We also showed that participants were able to trigger the activation of movements of their paralyzed limb using an intuitive interface controlled by voluntary actions and that they were able to perform useful functional movements such as holding a can and drinking through a straw.

Decoding hand and Wrist Movement Intention From Chronic Stroke Survivors With Hemiparesis Using A Wearable, User-Centric Neural Interface

<h3>Research Objectives</h3> To investigate the use of the NeuroLife® Sleeve to decode hand and wrist movements in chronic stroke survivors with hemiparesis for the eventual control of assistive devices. The NeuroLife Sleeve is a wearable garment worn on the forearm with 150 embedded electrodes spread across the forearm to record high-resolution surface electromyography (sEMG). <h3>Design</h3> Using the NeuroLife Sleeve, EMG activity was recorded while participants attempted 12 hand and wrist movements during three separate 2-hour sessions. <h3>Setting</h3> All studies were conducted at Battelle's laboratories. Participants were referred from therapists in the Columbus area or recruited from local support groups. <h3>Participants</h3> Six chronic stroke survivors (>6 months after stroke) with upper extremity motor impairment (Upper Extremity Fugl-Meyer: 7-38). <h3>Interventions</h3> Participants followed a series of hand and wrist movements on a computer monitor and performed the shown movement to the best of their ability. <h3>Main Outcome Measures</h3> EMG decoding accuracy to correctly predict movement intention from EMG data recorded from the NeuroLife Sleeve. <h3>Results</h3> We demonstrate that the NeuroLife Sleeve can accurately decode 12 functional hand and wrist movements, including multiple types of grasps with 75% average accuracy across subjects in simulated real-time situations. These results highlight the utility of the NeuroLife Sleeve and decoding algorithms as potential control systems for assistive devices. Collected feedback from stroke survivors who tested the system demonstrate the user-centric design of the NeuroLife Sleeve, including being simple to don and doff, comfortable, portable, and lightweight. <h3>Conclusions</h3> The NeuroLife Sleeve represents a user-centric, platform technology to record and decode high-definition electromyography for the eventual real-time control of assistive devices. <h3>Author(s) Disclosures</h3> None.

Personalized protocol and scoring scale for functional electrical stimulation of the hand: A pilot feasibility study.

Complex personalized Functional Electrical Stimulation (FES) protocols for calibrating parameters and electrode positioning have been proposed, most being time-consuming or technically cumbersome for clinical settings. Therefore, there is a need for new personalized FES protocols that generate comfortable, functional hand movements, while being feasible for clinical translation. To develop a personalized FES protocol, comprising electrode placement and parameter selection, to generate hand opening (HO), power grasp (PW) and precision grip (PG) movements, and compare in a pilot feasibility study its performance to a non-personalized protocol based on standard FES guidelines. Two FES protocols, one personalized (P1) and one non-personalized (P2), were used to produce hand movements in twenty-three healthy participants. FES-induced movements were assessed with a new scoring scale which comprises items for selectivity, functionality, and comfort. Higher FES-HSS scores were obtained with P1 for all movements: HO (p= 0.00013), PW (p= 0.00007), PG (p= 0.00460). Electrode placement time was significantly shorter for P2 (p= 0.00003). Comfort scores were similar for both protocols. The personalized protocol for electrode placement and parameter selection enabled functional FES-induced hand movements and presented advantages over a non-personalized protocol. This protocol warrants further investigation to confirm its suitability for developing upper-limb rehabilitation interventions with clinical translational potential.

Intrafascicular peripheral nerve stimulation produces fine functional hand movements in primates.

Restoring dexterous hand control is critical for people with paralysis. Approaches based on surface or intramuscular stimulation provide limited finger control, generate insufficient force to recover functional movements, and require numerous electrodes. Here, we show that intrafascicular peripheral electrodes could produce functional grasps and sustained forces in three monkeys. We designed an intrafascicular implantable electrode targeting the motor fibers of the median and radial nerves. Our interface selectively and reliably activated extrinsic and intrinsic hand muscles, generating multiple functional grips, hand opening, and sustained contraction forces for up to 2 months. We extended those results to a behaving monkey with transient hand paralysis and used intracortical signals to control simple stimulation protocols that enabled this animal to perform a functional grasping task. Our findings show that just two intrafascicular electrodes can generate a rich portfolio of dexterous and functional hand movements with important implications for clinical applicability.

Differences in the Level of Functional Fitness and Precise Hand Movements of People with and without Cognitive Disorders

ABSTRACT Objectives to assess and compare the gross and fine motor skills in people with identified cognitive impairment and in people from the control group. Method The research was conducted at the Center of Dementia-Related Diseases, involved participants with (n = 39) and without (n = 29) cognitive disorders. Fast, precise hand movements were measured via Vienna System Test. The up-and-go, chair-stand, 6-minute walk tests were used to assess functional fitness. The results for participants with and without cognitive disorders were compared. Results People from both groups do not differ significantly in terms of the level of condition-based functional fitness. Participants with cognitive disorders achieve worse results in hand coordination tests which are more complex and require both speed and accuracy of hand movements. Discussion The deterioration of precise hand movements with the correct functional efficiency may indicate degenerative changes in brain areas associated with complex thought processes, conceptual thinking, and may lead to dementia.

Action Imagery and Observation in Neurorehabilitation for Parkinson's Disease (ACTION-PD): Development of a User-Informed Home Training Intervention to Improve Functional Hand Movements.

Background Parkinson's disease (PD) causes difficulties with hand movements, which few studies have addressed therapeutically. Training with action observation (AO) and motor imagery (MI) improves performance in healthy individuals, particularly when the techniques are applied simultaneously (AO + MI). Both AO and MI have shown promising effects in people with PD, but previous studies have only used these separately. Objective This article describes the development and pilot testing of an intervention combining AO + MI and physical practice to improve functional manual actions in people with PD. Methods The home-based intervention, delivered using a tablet computer app, was iteratively designed by an interdisciplinary team, including people with PD, and further developed through focus groups and initial field testing. Preliminary data on feasibility were obtained via a six-week pilot randomised controlled trial (ISRCTN 11184024) of 10 participants with mild to moderate PD (6 intervention; 4 treatment as usual). Usage and adherence data were recorded during training, and semistructured interviews were conducted with participants. Exploratory outcome measures included dexterity and timed action performance. Results Usage and qualitative data provided preliminary evidence of acceptability and usability. Exploratory outcomes also suggested that subjective and objective performance of manual actions should be tested in a larger trial. The importance of personalisation, choice, and motivation was highlighted, as well as the need to facilitate engagement in motor imagery. Conclusions The results indicate that a larger RCT is warranted, and the findings also have broader relevance for the feasibility and development of AO + MI interventions for PD and other conditions.

Development and Application of a Motion Analysis Protocol for the Kinematic Evaluation of Basic and Functional Hand and Finger Movements Using Motion Capture in a Clinical Setting—A Repeatability Study

The purpose of this study was to develop a motion analysis protocol that allows the simultaneous assessment of all hand and finger joint movements. The objective was to demonstrate repeatability for future clinical applications in functional assessments. This study includes selection of marker positions, movement tasks, kinematic approaches and a comparison of the two most commonly used finger marker sets. By using a test–retest measurement of the range of motion in twenty healthy volunteers, the repeatability of the developed protocol was validated. Estimated errors of the presented method ranged from 1.2° to 6.4°. Finger joint angles derived from the marker set with two markers per segment showed better repeatability (3.7°) than with markers located on the joints (5.1°). Given the high repeatability found, the presented method appears to be suitable for clinical applications. For the fingers, measurement repeatability can be improved by using at least two markers per segment. Within this study, advanced kinematic approaches, such as functional determination of joint centers and axes, are applied to the analysis of hand movements. The provided standard values and estimate of the minimal detectable differences provide a valuable basis for meaningful data interpretation and may be used for future comparison with other protocols.

Determining grasp selection from arm trajectories via deep learning to enable functional hand movement in tetraplegia

BackgroundCervical spinal cord injury severely affects grasping ability of its survivors. Fortunately, many individuals with tetraplegia retain residual arm movements that allow them to reach for objects. We propose a wearable technology that utilizes arm movement trajectory information and deep learning methods to determine grasp selection. Furthermore, we combined this approach with neuromuscular stimulation to determine if self-driven functional hand movement could be enabled in spinal cord injury participants.MethodsTwo cervical SCI participants performed arbitrary and natural reaching movements toward target objects in three-dimensional space, which were recorded using an inertial sensor worn on their wrist. Time series classifiers were trained to recognize the trajectories using either a Dynamic Time Warping (DTW) algorithm or a Long Short-Term Memory (LSTM) recurrent neural network. As an initial proof-of-concept, we demonstrate real-time classification of the arbitrary movements using DTW only (due to its implementation simplicity), which when used in combination with a high density neuromuscular stimulation sleeve with textile electrodes, enabled participants to perform functional grasping.ResultsParticipants were able to consistently perform arbitrary two-dimensional and three-dimensional arm movements which could be classified with high accuracy. Furthermore, it was found that natural reaching trajectories for two different target objects (requiring two different grasp types) were distinct and also discriminable with high accuracy. In offline comparisons, LSTM (mean accuracies 99%) performed significantly better than DTW (mean accuracies 86 and 83%) for both arbitrary and natural reaching movements, respectively. Type I and II errors occurred more frequently for DTW (up to 60 and 15%, respectively), whereas it stayed under 5% for LSTM. Also, DTW achieved online accuracy of 79%.ConclusionsWe demonstrate the feasibility of utilizing arm trajectory information to determine grasp selection using a wearable inertial sensor along with DTW and deep learning methods. Importantly, this technology can be successfully used to control neuromuscular stimulation and restore functional independence to individuals living with paralysis.Trial registrationNCT, NCT03385005. Registered September 26, 2017

Fiber type composition of contiguous palmaris longus and abductor pollicis brevis muscles: Morphological evidence of a functional synergy.

The palmaris longus (PL) tendon is used in surgical opponensplasty to restore functional hand movements in thenar paralysis. Although successful PL autologous tendon transfer has been attributed to an established synergistic relationship between the PL and abductor pollicis brevis (APB) muscles in vivo, this functional relationship may be dependent on the quality of their spatial relationship and properties of their constituent muscle fibers. The purpose was to compare the proportion of type I and type II muscle fibers in the APB based on its contiguous morphological relationship with the PL tendon for indirect insight into their functional synergy, contractile capacity, and digastric arrangement. Twenty-four contiguous PL and APB specimens were harvested from the upper limbs (12 right and 12 left) of twelve formalin-embalmed cadavers (mean age: 74±10years). The fiber type composition of these muscles was determined by labeling serial cross sections with myosin heavy chain (MyHC) type I and type II monoclonal antibodies. The PL consisted of a relatively heterogeneous fiber type composition irrespective of the presence of a discrete (type I: 41±11%; type II: 55±12%; hybrid: 4±3%) or rudimentary (type I: 49±10%; type II: 45±9%; hybrid: 6±4%) tendinous connection with the APB. The APB fascicles arranged contiguously with the PL through a discrete tendon had significantly greater proportions of type II fibers (41±19%) compared to those with rudimentary PL connections (type II: 15±8%). Therefore, the APB fascicles arranged in a digastric relationship with the PL may have the capacity to produce more powerful contractions than those with rudimentary PL tendons based on the known contractile properties of type II muscle fibers. Knowledge of the spatial relationship between the PL and thenar musculature prior to PL autologous tendon transfer may be a useful indicator of the quality of established synergy in vivo.

Fiber Type Composition of Contiguous Palmaris Longus and Abductor Pollicis Brevis Muscles: Morphological Evidence of a Functional Synergy

IntroductionThe palmaris longus (PL) tendon can be transferred to the thumb for use in surgical opponensplasty to restore functional hand movements in patients with thenar paralysis. Successful opponensplasty outcomes using the PL tendon have been attributed to an intrinsic synergy of the PL with the abductor pollicis brevis (APB) such that no specific muscular retraining is needed upon tendon transfer. This synergy has been demonstrated electromyographically in which synchronous EMG signals were recorded from the PL and APB during functional thenar movements in healthy young individuals, in vivo. Thus, although an established synergistic relationship between these muscles has been demonstrated, this functional relationship may depend on their spatial relationship and properties of their constituent muscle fibers. The purpose of this study was to compare the proportions of type I and type II muscle fibers in the APB from cadaveric muscle based on its contiguous morphological relationship with the PL tendon for further insight into their functional synergy, contractile capacity and digastric arrangement.MethodsTwenty‐four contiguous PL and APB specimens were harvested from the upper limbs (12 right, 12 left) of twelve formalin‐embalmed cadavers (mean age: 74 ± 10 years). The 24 limbs were classified into two groups based on the following morphological criteria: (1) APB with discrete PL tendon connections, or (2) APB with non‐discrete, or rudimentary, PL tendon connections. Cadaveric specimens were obtained from the body bequeathal program at the University of Western Ontario and approved for research use by the Committee for Cadaver Use in Research (REF#21092016). The fiber type composition of the APB and PL muscles was determined by labeling serial cross‐sections with myosin heavy chain type I and type II monoclonal antibodies.ResultsThe APB fascicles from 11 hands (46%) were classified as discrete based on their continuity with the PL tendon. Conversely, the APB fascicles from 13 hands (54%) were classified as non‐discrete due to rudimentary or minimal connections with the PL tendon. The PL consisted of a relatively heterogeneous fiber type composition irrespective of the presence of a discrete (type I: 41 ± 11%, type II: 55 ± 12%, hybrid: 4 ± 3%), or rudimentary (type I: 49 ± 10%,type II: 45 ± 9%, hybrid: 6 ± 4%), tendinous connection with APB musculature. The APB fascicles arranged in a digastric manner with the PL tendon had significantly greater proportions of type II fibers (41 ± 19%) compared to those with rudimentary PL connections (type II: 15 ± 8%).ConclusionThe APB fascicles arranged in a digastric relationship with the PL may have the capacity to produce more powerful contractions than those with rudimentary PL tendons based on the known contractile properties of type II muscle fibers. Knowledge of the spatial relationship between the PL and thenar musculature prior to PL autologous tendon transfer may be a useful indicator of the quality of established synergy in vivo.Support or Funding InformationSupported by NSERC

Differentiating Variations in Thumb Position From Recordings of the Surface Electromyogram in Adults Performing Static Grips, a Proof of Concept Study.

Hand gesture and grip formations are produced by the muscle synergies arising between extrinsic and intrinsic hand muscles and many functional hand movements involve repositioning of the thumb relative to other digits. In this study we explored whether changes in thumb posture in able-body volunteers can be identified and classified from the modulation of forearm muscle surface-electromyography (sEMG) alone without reference to activity from the intrinsic musculature. In this proof-of-concept study, our goal was to determine if there is scope to develop prosthetic hand control systems that may incorporate myoelectric thumb-position control. Healthy volunteers performed a controlled-isometric grip task with their thumb held in four different opposing-postures. Grip force during task performance was maintained at 30% maximal-voluntary-force and sEMG signals from the forearm were recorded using 2D high-density sEMG (HD-sEMG arrays). Correlations between sEMG amplitude and root-mean squared estimates with variation in thumb-position were investigated using principal-component analysis and self-organizing feature maps. Results demonstrate that forearm muscle sEMG patterns possess classifiable parameters that correlate with variations in static thumb position (accuracy of 88.25 ± 0.5% anterior; 91.25 ± 2.5% posterior musculature of the forearm sites). Of importance, this suggests that in transradial amputees, despite the loss of access to the intrinsic muscles that control thumb action, an acceptable level of control over a thumb component within myoelectric devices may be achievable. Accordingly, further work exploring the potential to provide myoelectric control over the thumb within a prosthetic hand is warranted.

An sEMG-based Interface to give People with Severe Muscular Atrophy control over Assistive Devices.

Injuries, accidents, strokes, and other diseases can significantly degrade the capabilities to perform even the most simple activities in daily life. While assistive technology becomes more and more available to the people affected, there is still a big need for user interfaces suitable for people without functional hand movement. A large share of these cases involves neuromuscular diseases, which lead to severely reduced muscle function. However, even though affected people are no longer able to functionally move their limbs, residual muscle function can still be existent. Previous work has shown that this residual muscular activity can suffice, to create an EMG-based user interface, and e.g., allow for control of assistive devices. In this paper, we enhance this user interface with additional EMG-features and an improved training paradigm in order to increase information extraction from recordings of strongly atrophic muscles. The interface was tested and validated by subjects with severe spinal muscular atrophy. Results show that the used methods improve the decoding and thereby allow for a considerable increase in performance when controlling a robotic manipulator in a 3D reaching task.

Dexterous Control of Seven Functional Hand Movements Using Cortically-Controlled Transcutaneous Muscle Stimulation in a Person With Tetraplegia.

Individuals with tetraplegia identify restoration of hand function as a critical, unmet need to regain their independence and improve quality of life. Brain-Computer Interface (BCI)-controlled Functional Electrical Stimulation (FES) technology addresses this need by reconnecting the brain with paralyzed limbs to restore function. In this study, we quantified performance of an intuitive, cortically-controlled, transcutaneous FES system on standardized object manipulation tasks from the Grasp and Release Test (GRT). We found that a tetraplegic individual could use the system to control up to seven functional hand movements, each with >95% individual accuracy. He was able to select one movement from the possible seven movements available to him and use it to appropriately manipulate all GRT objects in real-time using naturalistic grasps. With the use of the system, the participant not only improved his GRT performance over his baseline, demonstrating an increase in number of transfers for all objects except the Block, but also significantly improved transfer times for the heaviest objects (videocassette (VHS), Can). Analysis of underlying motor cortex neural representations associated with the hand grasp states revealed an overlap or non-separability in neural activation patterns for similarly shaped objects that affected BCI-FES performance. These results suggest that motor cortex neural representations for functional grips are likely more related to hand shape and force required to hold objects, rather than to the objects themselves. These results, demonstrating multiple, naturalistic functional hand movements with the BCI-FES, constitute a further step toward translating BCI-FES technologies from research devices to clinical neuroprosthetics.

The Impact of Shoulder Abduction Loading on Volitional Hand Opening and Grasping in Chronic Hemiparetic Stroke

Background. Up to 60% of individuals with moderate to severe chronic hemiparetic stroke experience excessive involuntary wrist/finger flexion that constrains functional hand movements including hand opening. It’s not known how stroke-induced brain injury impacts volitional hand opening and grasping forces as a result of the expression of abnormal coupling between shoulder abduction and wrist/finger flexion or the flexion synergy. Objective. The goal of this study is to understand how shoulder abduction loading affects volitional hand opening and grasping forces in individuals with moderate to severe chronic hemiparetic stroke. Methods. Thirty-six individuals (stroke, 26; control, 10) were recruited for this study. Each participant was instructed to perform maximal hand opening and grasping forces while the arm was either fully supported or lifted with a weight equal to 25% or 50% of the participant’s maximal shoulder abduction torque. Hand pentagon area, defined as the area formed by the tips of thumb and fingers, was calculated during hand opening. Forces were recorded during grasping. Results. In individuals with moderate stroke, increasing shoulder abduction loading reduced the ability to maximally open the hand. In individuals with severe stroke, who were not able to open the hand, grasping forces were generated and increased with shoulder abduction loading. Stroke individuals also showed a reduced ability to control volitional grasping forces due to the enhanced expression of flexion synergy. Conclusions. Shoulder abduction loading reduced the ability to volitionally open the hand and control grasping forces after stroke. Neural mechanisms and clinical implications of these findings are discussed.

SCRIPT passive orthosis: design of interactive hand and wrist exoskeleton for rehabilitation at home after stroke

Recovery of functional hand movements after stroke is directly linked to rehabilitation duration and intensity. Continued therapy at home has the potential to increase both. For many patients this requires a device that helps them overcome the hyperflexion of wrist and fingers that is limiting their ability to open and use their hand. We developed an interactive hand and wrist orthosis for post-stroke rehabilitation that provides compliant and adaptable extension assistance at the wrist and fingers, interfaces with motivational games based on activities of daily living, is integrated with an off-the-shelf mobile arm support and includes novel wrist and finger actuation mechanisms. During the iterative development, multiple prototypes have been evaluated by therapists in clinical settings and used intensively and independently by 33 patients at home. This paper details the final design of the SCRIPT passive orthosis resulting from these efforts.