Hand Muscle Activity Research Articles

Negative motor responses to direct electrical stimulation: Behavioral assessment hides different effects on muscles

A negative motor response (NMR) is defined as the inability to continue voluntary movements without losing consciousness when direct electrical stimulation (DES) is applied during awake neurosurgery. While visual inspection is most commonly used to define an NMR, the actual effect of stimulation on muscle activity has been neglected by recent neurosurgical literature.We show that behavioral assessment of NMRs hides different site-dependent effects on muscles as revealed by electromyography (EMG), describing ten cases of brain tumor patients undergoing awake neurosurgery while performing a hand-object manipulation task. DES-induced NMRs were assessed behaviorally and related to the underlying electromyographic recording. Quantitative analysis of motor unit recruitment and regularity between phasic muscle contractions was computed. We show that similar NMRs classified based on behavioral criteria can be associated with suppression, increased recruitment or mixed effects on ongoing hand muscles. In some cases, suppression of hand muscle activity is associated with involuntary recruitment of muscles not involved in the task. Interestingly, stimulation of behaviorally defined “negative areas” across the frontal and parietal lobes elicits different electromyographic patterns, depending on the stimulation site. This study provides novel preliminary background as to the heterogeneous profile of muscle activity during NMRs. In fact, EMG monitoring paired with behavioral assessment can distinguish between NMRs that, despite similarity on behavioral inspection, are different in their related EMG, possibly underlying different neural substrates. The identification of different circuits hidden in similar NMRs may become relevant when planning the extension of resection.

Effective Multi-Mode Grasping Assistance Control of a Soft Hand Exoskeleton Using Force Myography.

Human intention detection is fundamental to the control of robotic devices in order to assist humans according to their needs. This paper presents a novel approach for detecting hand motion intention, i.e., rest, open, close, and grasp, and grasping force estimation using force myography (FMG). The output is further used to control a soft hand exoskeleton called an SEM Glove. In this method, two sensor bands constructed using force sensing resistor (FSR) sensors are utilized to detect hand motion states and muscle activities. Upon placing both bands on an arm, the sensors can measure normal forces caused by muscle contraction/relaxation. Afterwards, the sensor data is processed, and hand motions are identified through a threshold-based classification method. The developed method has been tested on human subjects for object-grasping tasks. The results show that the developed method can detect hand motions accurately and to provide assistance w.r.t to the task requirement.

Neck Injury-Motor Vehicle Accident

HISTORY: A 57-year-old male was involved in a motorcycle accident, landing on his right side. Injuries included a flaccid right arm and hand, laceration of his right thigh, and a fracture of the 3rd metatarsal of his right foot. Patient’s chief complaint was pain in right shoulder and neck and an inability to complete ADLs. PHYSICAL EXAMINATION: Patient demonstrated flaccid right upper extremity with very little finger movement. Patient was able to achieve some finger flexion of all 5 digits and thumb opposition to index finger, although could not achieve pad to pad contact. All PROM of joints was preserved. Sensation was grossly intact. Patient tolerated initial examination well with mild discomfort during objective measures. No red flags arose during medical screening/systems review. DIFFERENTIAL DIAGNOSIS: 1. Cerebrovascular accident 2. Brachial plexus stretch injury 3. Brachial plexus avulsion injury TESTS AND RESULTS: MRI of cervical spine without contrast – small disc herniation, MRI of brachial plexus with and without contrast - edema involving right scalene and adjacent fascial planes extending into brachial plexus as well as into right C6/C7 and C7/T1 neural foramen to confirm nerve root sleeve tears, CTA of neck – negative for artery involvement, EMG study showed that the brachial plexus was not avulsed, but not currently sending EMG signals to hand. FINAL/WORKING DIAGNOSIS: Brachial plexus stretch injury TREATMENT AND OUTCOMES: 1. Therapeutic exercises (ROM, strength, endurance, stability), 2. Therapeutic activity (work specific, ADL specific), 3. Neuromuscular rehabilitation (muscle re-education, sequencing, coordination, neurodynamics), 4. Patient education (home exercise program, home safety). Patient has been responding well to a treatment plan combining aspects of the above mentioned interventions. Has been showing greater activation of right hand and forearm muscles with ability to complete weak grip at this stage. Right upper extremity remains supported in sling.

Neural noise and cortical inhibition in schizophrenia

BackgroundNeural information processing is subject to noise and this leads to variability in neural firing and behavior. Schizophrenia has been associated with both more variable motor control and impaired cortical inhibition, which is crucial for excitatory/inhibitory balance in neural commands. HypothesisIn this study, we hypothesized that impaired intracortical inhibition in motor cortex would contribute to task-related motor noise in schizophrenia. MethodsWe measured variability of force and of electromyographic (EMG) activity in upper limb and hand muscles during a visuomotor grip force-tracking paradigm in patients with schizophrenia (N = 25), in unaffected siblings (N = 17) and in healthy control participants (N = 25). Task-dependent primary motor cortex (M1) excitability and inhibition were assessed using transcranial magnetic stimulation (TMS). ResultsDuring force maintenance patients with schizophrenia showed increased variability in force and EMG, despite similar mean force and EMG magnitudes. Compared to healthy controls, patients with schizophrenia also showed increased M1 excitability and reduced cortical inhibition during grip-force tracking. EMG variability and force variability correlated negatively to cortical inhibition in patients with schizophrenia. EMG variability also correlated positively to negative symptoms. Siblings had similar variability and cortical inhibition compared to controls. Increased EMG and force variability indicate enhanced motor noise in schizophrenia, which relates to reduced motor cortex inhibition. ConclusionThe findings suggest that excessive motor noise in schizophrenia may arise from an imbalance of M1 excitation/inhibition of GABAergic origin. Thus, higher motor noise may provide a useful marker of impaired cortical inhibition in schizophrenia.

Investigating the performance of an amplitude-independent algorithm for detecting the hand muscle activity of stroke survivors

To make robotic hand devices controlled by surface electromyography (sEMG) signals feasible and practical tools for assisting patients with hand impairments, the problems that prevent these devices from being widely used have to be overcome. The most significant problem is the involuntary amplitude variation of the sEMG signals due to the movement of electrodes during forearm motion. Moreover, for patients who have had a stroke or another neurological disease, the muscle activity of the impaired hand is weak and has a low signal-to-noise ratio (SNR). Thus, muscle activity detection methods intended for controlling robotic hand devices should not depend mainly on the amplitude characteristics of the sEMG signal in the detection process, and they need to be more reliable for sEMG signals that have a low SNR. Since amplitude-independent muscle activity detection methods meet these requirements, this paper investigates the performance of such a method on people who have had a stroke in terms of the detection of weak muscle activity and resistance to false alarms caused by the involuntary amplitude variation of sEMG signals; these two parameters are very important for achieving the reliable control of robotic hand devices intended for people with disabilities. A comparison between the performance of an amplitude-independent muscle activity detection algorithm and three amplitude-dependent algorithms was conducted by using sEMG signals recorded from six hemiparesis stroke survivors and from six healthy subjects. The results showed that the amplitude-independent algorithm performed better in terms of detecting weak muscle activity and resisting false alarms.

The immediate effect of whole body vibration training on the electromyographic activity of contralateral hand muscles; a randomized controlled trial

Whole Body Vibration (WBV) has been used as a useful adjunct to improve the neuromuscular function of the upper limb. Cross-transfer of strength plays an important role in rehabilitation of unilateral injuries. The present research intended to evaluate the acute effect of low frequency WBV training on cross-transfer of electromyographic activity and hand muscles strength when the measurement was performed on the contralateral limb. This was a randomized crossover trial conducted in a clinical biomechanics laboratory. Twenty-eight healthy participants aging between 20 and 35 years were included who were involved in two sessions with two weeks of rest. The participants were randomly assigned in two groups as follows: 1) active WBV/sham WBV; 2) sham WBV/active WBV. The participants were asked to stand on the vibrating plate and pull its belt in a vibrating mode using their dominant hand. Then, after a two-week rest, they performed the same task in the vibrating mode (35 Hz). Grip strength and electromyography (root mean square) in flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), and extensor carpi ulnaris (ECU) muscles of the contralateral limb were measured before and after exercise in both phases. No significant change was observed in the electrical activity of FDP, FDS, ECR, ECU muscles, and hands' grip strength of the contralateral limb (P > 0.05). WBV (35 Hz) was not able to augment cross-transfer in electromyographic activity and neuromuscular performance of the upper limb. Further studies would help to explore these results for several sessions of WBV on cross-transfer of training.

A calibrated database of kinematics and EMG of the forearm and hand during activities of daily living

Linking hand kinematics and forearm muscle activity is a challenging and crucial problem for several domains, such as prosthetics, 3D modelling or rehabilitation. To advance in this relationship between hand kinematics and muscle activity, synchronised and well-defined data are needed. However, currently available datasets are scarce, and the presented tasks and data are often limited. This paper presents the KIN-MUS UJI Dataset that contains 572 recordings with anatomical angles and forearm muscle activity of 22 subjects while performing 26 representative activities of daily living. This dataset is, to our knowledge, the biggest currently available hand kinematics and muscle activity dataset to focus on goal-oriented actions. Data were recorded using a CyberGlove instrumented glove and surface EMG electrodes, both properly synchronised. Eighteen hand anatomical angles were obtained from the glove sensors by a validated calibration procedure. Surface EMG activity was recorded from seven representative forearm areas. The statistics verified that data were not affected by the experimental procedures and were similar to the data acquired under real-life conditions.

Direct Electrical Stimulation of Premotor Areas: Different Effects on Hand Muscle Activity during Object Manipulation.

Dorsal and ventral premotor (dPM and vPM) areas are crucial in control of hand muscles during object manipulation, although their respective role in humans is still debated. In patients undergoing awake surgery for brain tumors, we studied the effect of direct electrical stimulation (DES) of the premotor cortex on the execution of a hand manipulation task (HMt). A quantitative analysis of the activity of extrinsic and intrinsic hand muscles recorded during and in absence of DES was performed. Results showed that DES applied to premotor areas significantly impaired HMt execution, affecting task-related muscle activity with specific features related to the stimulated area. Stimulation of dorsal vPM induced both a complete task arrest and clumsy task execution, characterized by general muscle suppression. Stimulation of ventrocaudal dPM evoked a complete task arrest mainly due to a dysfunctional recruitment of hand muscles engaged in task execution. These results suggest that vPM and dPM contribute differently to the control of hand muscles during object manipulation. Stimulation of both areas showed a significant impact on motor output, although the different effects suggest a stronger relationship of dPM with the corticomotoneuronal circuit promoting muscle recruitment and a role for vPM in supporting sensorimotor integration.

Role of Interhemispheric Cortical Interactions in Poststroke Motor Function

Background/Objective. We investigated interhemispheric interactions in stroke survivors by measuring transcranial magnetic stimulation (TMS)–evoked cortical coherence. We tested the effect of TMS on interhemispheric coherence during rest and active muscle contraction and compared coherence in stroke and older adults. We evaluated the relationships between interhemispheric coherence, paretic motor function, and the ipsilateral cortical silent period (iSP). Methods. Participants with (n = 19) and without (n = 14) chronic stroke either rested or maintained a contraction of the ipsilateral hand muscle during simultaneous recordings of evoked responses to TMS of the ipsilesional/nondominant (i/ndM1) and contralesional/dominant (c/dM1) primary motor cortex with EEG and in the hand muscle with EMG. We calculated pre- and post-TMS interhemispheric beta coherence (15-30 Hz) between motor areas in both conditions and the iSP duration during the active condition. Results. During active i/ndM1 TMS, interhemispheric coherence increased immediately following TMS in controls but not in stroke. Coherence during active cM1 TMS was greater than iM1 TMS in the stroke group. Coherence during active iM1 TMS was less in stroke participants and was negatively associated with measures of paretic arm motor function. Paretic iSP was longer compared with controls and negatively associated with clinical measures of manual dexterity. There was no relationship between coherence and. iSP for either group. No within- or between-group differences in coherence were observed at rest. Conclusions. TMS-evoked cortical coherence during hand muscle activation can index interhemispheric interactions associated with poststroke motor function and potentially offer new insights into neural mechanisms influencing functional recovery.

A dynamic model of hand movements for proportional myoelectric control of a hand prosthesis.

In myo-controlled prosthetic hands, surface electromyographic signals are used to operate the hand actuators. A pre-requisite for effective control is that the intended movement is decoded from muscle activity. Simpler approaches use pattern recognition techniques, which assume a finite set of possible actions. However, this leads to unnatural, discontinuous control. Proportional controllers do not require a finite set of actions to be specified in advance but are difficult to use, particularly with dexterous multi-fingered hands. Here we discuss a control module which continuously predicts the intended movements from recorded multi-channel electromyographic activity. The module can be seen as a (simplified) forward model of the dynamics of the intact hand. We describe a procedure for estimating model parameters from hand movement and muscle activity data, and discuss its application to the proportional myoelectric control of a prosthetic hand.

P69-S Cutaneous silent period behavior in different motor neuron diseases phenotypes

Background The cutaneous silent period (CSP) corresponds to a reduced electric activity of a contracting muscle, after electrical stimulation of sensory fibers. The afferent volley causes a presynaptic inhibition of spinal motor neurons (LMN) modulated by complex spinal circuits. CSP behavior in different motor neuron diseases (MND) phenotypes is unknown. Materials and methods We included 20 MND patients and 15 controls. CSP was obtained by applying electrical stimulation of the 5th finger. Surface EMG recordings were obtained from ADM muscle. CSP duration was defined by the time between a drop of rectified averaged EMG below 80%, and the final return above 80%, of baseline EMG. The mean duration was obtained from 10 consecutive curves obtained before and during co-contraction of the contralateral ADM muscle. Results MND patients had a median age of 59 years. 12 were diagnosed as amyotrophic lateral sclerosis (ALS), 6 as progressive muscular atrophy (PMA), 2 as primary lateral sclerosis (PLS). Median CSP duration was similar between controls and patients. During contralateral ADM contraction, CSP duration did not change in controls, patients with ALS and PMA, but decreased by 28% in PLS patients. Conclusions We present preliminary results suggesting that CSP behavior is not homogenous in different phenotypes of MND. We previously observed that reflex contralateral activation of the homonymous contralateral hand muscles is frequent in patients with PLS, indicating spinal cord hyperexcitability. Our CSP results suggest that this method can contribute to dissect the mechanisms underlying abnormal LMN excitability in patients with corticospinal tract lesion.

Logistic regression analysis of multiple interosseous hand-muscle activities using surface electromyography during finger-oriented tasks

Intrinsic hand muscles are densely located in the hand, and the myoelectric observation from the surface is sometimes unreliable because of some outside influences that may interfere with the signals. In the present study, we evaluated the activities of multiple interosseous hand-muscles which densely located in the hand, through analyzing the surface electromyographic signals during finger-oriented tasks using univariate and multivariate logistic regression models. Ten healthy subjects participated in our experiment, and isometrically exercised each finger one by one in flexed form. The result of a univariate analysis with the power and amplitude domain predictor variables of the surface electromyographic signals showed significant consistency between the activated finger and the inserted finger of the dorsal interosseous muscles to the proximal phalanx (P < 0.001). Meanwhile, the results of a multivariate analysis showed a higher correlation of the regression model of the fourth dorsal interosseous muscle during the action of the ring finger using frequency-domain variables (the Nagelkerke R2 = 0.716 when the median frequency was used), compared to the model without the frequency-domain variables (the Nagelkerke R2 = 0.583). Our result showed that the logistic regression models have a particular possibility for the analysis of the surface electromyographic signals of densely located hand-muscle activities related to the finger-oriented tasks.

Priming of grasping muscles when viewing a safety handle is diminished with age

Merely viewing objects within reachable space can activate motor cortical networks and potentiate movement. This holds potential value for smooth interaction with objects in our surroundings, and could offer an advantage for quickly generating targeted hand movements (e.g. grasping a support rail to maintain stability). The present study investigated if viewing a wall-mounted safety handle resulted in automatic activation of motor cortical networks, and if this effect changes with age. Twenty-five young adults (18–30 years) and seventeen older adults (65+ years) were included in this study. Single-pulse, transcranial magnetic stimulation was applied over the motor cortical hand representation of young and older adults shortly after they viewed a safety handle within reaching distance. Between trials, vision was occluded and the environment was unpredictably altered to reveal either a safety handle, or no handle (i.e. covered). Modulation of intrinsic hand muscle activity was evident in young adults when viewing a handle, and this was selective in terms of both the muscles activated and the time at which it emerged. By contrast, older adults failed to show any changes when viewing the safety handle. Specifically, the presence of a handle increased corticospinal activity in hand muscles of young adults when TMS was applied 120 ms after opening the goggles (p = .014), but not in the older adults (p > .954). The fact that the visual priming observed in younger adults was absent in older adults suggests that aging may diminish the ability to quickly put our visual world into automatic motor terms.

Effects of High-intensity Robot-assisted Hand Training on Upper Limb Recovery and Muscle Activity in Individuals With Multiple Sclerosis: A Randomized, Controlled, Single-Blinded Trial.

Background : Integration of robotics and upper limb rehabilitation in people with multiple sclerosis (PwMS) has rarely been investigated.Objective: To compare the effects of robot-assisted hand training against non-robotic hand training on upper limb activity in PwMS. To compare the training effects on hand dexterity, muscle activity, and upper limb dysfunction as measured with the International Classification of Functioning.Methods: This single-blind, randomized, controlled trial involved 44 PwMS (Expanded Disability Status Scale:1.5–8) and hand dexterity deficits. The experimental group (n = 23) received robot-assisted hand training; the control group (n = 21) received non-robotic hand training. Training protocols lasted for 5 weeks (50 min/session, 2 sessions/week). Before (T0), after (T1), and at 1 month follow-up (T2), a blinded rater evaluated patients using a comprehensive test battery. Primary outcome: Action Research Arm Test. Secondary outcomes: Nine Holes Peg Test; Fugl-Meyer Assessment Scale–upper extremity section; Motricity Index; Motor Activity Log; Multiple Sclerosis (MS) Quality of Life−54; Life Habits assessment—general short form and surface electromyography.Results: There were no significant between-group differences in primary and secondary outcomes. Electromyography showed relevant changes providing evidence increased activity in the extensor carpi at T1 and T2.Conclusion: The training effects on upper limb activity and function were comparable between the two groups. However, robot-assisted training demonstrated remarkable effects on upper limb use and muscle activity. https://clinicaltrials.gov NCT03561155.

Using Inertial Measurement Units and Electromyography to Quantify Movement during Action Research Arm Test Execution.

In patients after stroke, ability of the upper limb is commonly assessed with standardised clinical tests that provide a complete upper limb assessment. This paper presents quantification of upper limb movement during the execution of Action research arm test (ARAT) using a wearable system of inertial measurement units (IMU) for kinematic quantification and electromyography (EMG) sensors for muscle activity analysis. The test was executed with each arm by a group of healthy subjects and a group of patients after stroke allocated into subgroups based on their clinical scores. Tasks were segmented into movement and manipulation phases. Each movement phase was quantified with a set of five parameters: movement time, movement smoothness, hand trajectory similarity, trunk stability, and muscle activity for grasping. Parameters vary between subject groups, between tasks, and between task phases. Statistically significant differences were observed between patient groups that obtained different clinical scores, between healthy subjects and patients, and between the unaffected and the affected arm unless the affected arm shows normal performance. Movement quantification enables differentiation between different subject groups within movement phases as well as for the complete task. Spearman’s rank correlation coefficient shows strong correlations between patient’s ARAT scores and movement time as well as movement smoothness. Weak to moderate correlations were observed for parameters that describe hand trajectory similarity and trunk stability. Muscle activity correlates well with grasping activity and the level of grasping force in all groups.

The interaction effect of working postures on muscle activity and subjective discomfort during static working postures and its correlation with OWAS

Methods assessing exposure to workload calculate risk scores of individual body segments which are added up to calculate an overall risk score for the whole body. However, these methods ignore interaction effects of body segments. This may lead to inaccurate assessment of risk scores of workload. The aim of the study was to examine interaction effects of shoulder flexion angle and back angle on rating of perceived exertion (RPE) and muscle activity, and to investigate the correlation between corresponding Ovako Working Posture Analysing System (OWAS) risk scores on the one hand and RPE and muscle activity on the other. The study revealed that there is a significant interaction effect of back angle and shoulder angle on muscle activity and RPE. Furthermore, OWAS seems to correlate only with back muscle activity. Thus, integration of interaction effects to ergonomic assessment methods seems to provide a higher accuracy of risk scores. Relevance to industryThis article introduces the relevance of interaction effects of body segments to the assessment of workload. The study revealed that isolated assessment of working postures ignores interaction effects. A consideration of interaction effects leads to a higher accuracy of risk scores quantifying exposure to workload.

Temporal exploration in sequential movements shapes efficient neuromuscular control.

The interaction of early and deliberate practice with genetic predisposition endows experts with virtuosic motor performance. However, it has not been known whether ways of practicing shape motor virtuosity. Here, we addressed this issue by comparing the effects of rhythmic variation in motor practice on neuromuscular control of the finger movements in pianists. With the use of a novel electromyography system with miniature active electrodes, we recorded the activity of the intrinsic hand muscles of 27 pianists while they played the piano and analyzed it by using a nonnegative matrix factorization algorithm and cluster analysis. The result demonstrated that practicing a target movement sequence with various rhythms reduced muscular activity, whereas neither practicing a sequence with a single rhythm nor taking a rest without practicing changed the activity. In addition, practice with rhythmic variation changed the patterns of simultaneous activations across muscles. This alteration of muscular coordination was associated with decreased activation of muscles not only relevant to, but also irrelevant to the task performance. In contrast, piano practice improved the maximum speed of the performance, the amount of which was independent of whether rhythmic variation was present. These results suggest that temporal variation in movement sequences during practice co-optimizes both movement speed and neuromuscular efficiency, which emphasizes the significance of ways of practice in the acquisition of motor virtuosity. NEW & NOTEWORTHY A key question in motor neuroscience is whether "ways of practicing" contribute to shaping motor virtuosity. We found both attenuation of activities and alteration of coordination of the intrinsic hand muscles of pianists, specifically through practicing a movement sequence with various rhythms. The maximum speed of the finger movements was also enhanced following the practice. These results emphasize the importance of ways of practicing in facilitating multiple skills: efficiency and speed.

The Comparison of Electromyographic Activity of Selected Shoulder Girdle Muscles in Elite Table Tennis Players with and without Shoulder Impingement Syndrome during Forehand Topspin

Introduction: Shoulder injuries are very common in sports such as table tennis in which the athletes’ upper limb operates higher than shoulder level. On the other hand, weak or inappropriate shoulder muscle activity can be related to incidence of an injury. The purpose of this study was to compare the activation of selected scapulohumeral muscles in table tennis athletes between healthy and shoulder impingement syndrome group during a strike of forehand topspin. Materials and Methods: Thirty national-level male table tennis players aged 20 to 28 years were selected purposefully and divided into shoulder impingement syndrome (n = 15), and healthy (n = 15) groups. The surface electromyographic activity of selected muscles from scapulothoracic and glenohumeral joints was recorded during the strike of forehand topspin . Results: The level of the activity of the serratus anterior muscle (P = 0.007) and supraspinatus muscle (P = 0.001) in the shoulder impingement syndrome group was significantly lower and the level of upper trapezius muscle activation in the shoulder impingement syndrome subjects was significantly higher (P = 0.009) in shoulder impingement syndrome group compared to the healthy group. However, no significant differences were observed in the activation level of lower trapezius (P = 0.301), anterior deltoid (P = 0.314), and biceps brachii (P = 0.291) muscles. Conclusion: The results of this study showed that patients with impingement syndrome demonstrated unnatural and changed levels of muscle activity in scapulohumeral articulation during the forehand topspin strike. The findings confirm the theories that shoulder impingement may be related to changes in the activity level of scapulothoracic and glenohumeral muscles.

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OBJECTIVES/SPECIFIC AIMS: Upper-extremity (UE) impairment affects 88% of stroke survivors due to dysfunctional shoulder-hand coordination. Patients may be able to grasp with the arm at rest, but unable to grasp in a functional context (eg, from a high shelf) because shoulder use elicits involuntary hand muscle activity. Further, much rehabilitation research is directed at unsuccessful stroke recovery (patients with persistent UE impairment) but very little towards patients who show successful clinical recovery (such as those with mild UE impairment) even though these patients have attained the desired rehabilitation outcome. We examined the neurophysiological trajectory of successful compared to unsuccessful post-stroke recovery in the context of functional UE movements to clearly identify what factors are necessary for successful recovery of functional UE movements after stroke. METHODS/STUDY POPULATION: We studied 3 populations: (1) mildly-impaired patients, early (at &lt;17 d, 30 d, 90 d, and 180 d) after stroke as a model of successful post-stroke recovery, (2) moderately-impaired, chronic patients (&gt;6-months post stroke) with persistent hand function impairment, as a model of incomplete post-stroke recovery (unsuccessful recovery), and (3) Healthy age-range matched controls. We used transcranial magnetic stimulation (TMS) in all 3 groups at the given time points to measure corticomotor excitability (motor evoked potentials, recruitment curve), corticomotor inhibition (short-interval intracortical inhibition, long-interval intracortical inhibition), and intracortical facilitation of hand muscles with the shoulder positioned in different degrees of flexion or abduction (these shoulder positions are known to elicit involuntary, undesired hand muscle activation, which leads to UE dysfunction and impairment in individuals with stroke). RESULTS/ANTICIPATED RESULTS: Data collection are in process and will be presented. Preliminary data from controls shows that corticomotor excitability of selected hand muscles is affected by changes in shoulder position. Preliminary findings in controls are consistent with clinical findings in stroke that certain shoulder positions elicit involuntary and undesired hand muscle activation, leading to UE dysfunction and disability. Findings from the stroke groups will be presented. DISCUSSION/SIGNIFICANCE OF IMPACT: We hypothesize that this centrally-facilitated coupling between shoulder and hand muscles is disrupted after stroke, which may play a central role in the inability of patients to perform functional UE movements. By comparing the TMS metrics in mildly-impaired Versus moderately-impaired chronic patients, we will be able to identify the longitudinal change in neurophysiology underlying shoulder-hand coordination that is associated with successful or unsuccessful clinical recovery of UE function after stroke. Thus, these findings will help us distinguish between the neurophysiology underlying successful from unsuccessful UE recovery leading to more mechanism-based interventions for UE dysfunction post stroke in the future.

Gaussian Process Autoregression for Simultaneous Proportional Multi-Modal Prosthetic Control With Natural Hand Kinematics.

Matching the dexterity, versatility, and robustness of the human hand is still an unachieved goal in bionics, robotics, and neural engineering. A major limitation for hand prosthetics lies in the challenges of reliably decoding user intention from muscle signals when controlling complex robotic hands. Most of the commercially available prosthetic hands use muscle-related signals to decode a finite number of predefined motions and some offer proportional control of open/close movements of the whole hand. Here, in contrast, we aim to offer users flexible control of individual joints of their artificial hand. We propose a novel framework for decoding neural information that enables a user to independently control 11 joints of the hand in a continuous manner-much like we control our natural hands. Toward this end, we instructed six able-bodied subjects to perform everyday object manipulation tasks combining both dynamic, free movements (e.g., grasping) and isometric force tasks (e.g., squeezing). We recorded the electromyographic and mechanomyographic activities of five extrinsic muscles of the hand in the forearm, while simultaneously monitoring 11 joints of hand and fingers using a sensorized data glove that tracked the joints of the hand. Instead of learning just a direct mapping from current muscle activity to intended hand movement, we formulated a novel autoregressive approach that combines the context of previous hand movements with instantaneous muscle activity to predict future hand movements. Specifically, we evaluated a linear vector autoregressive moving average model with exogenous inputs and a novel Gaussian process ( ) autoregressive framework to learn the continuous mapping from hand joint dynamics and muscle activity to decode intended hand movement. Our approach achieves high levels of performance (RMSE of 8°/s and ). Crucially, we use a small set of sensors that allows us to control a larger set of independently actuated degrees of freedom of a hand. This novel undersensored control is enabled through the combination of nonlinear autoregressive continuous mapping between muscle activity and joint angles. The system evaluates the muscle signals in the context of previous natural hand movements. This enables us to resolve ambiguities in situations, where muscle signals alone cannot determine the correct action as we evaluate the muscle signals in their context of natural hand movements. autoregression is a particularly powerful approach which makes not only a prediction based on the context but also represents the associated uncertainty of its predictions, thus enabling the novel notion of risk-based control in neuroprosthetics. Our results suggest that autoregressive approaches with exogenous inputs lend themselves for natural, intuitive, and continuous control in neurotechnology, with the particular focus on prosthetic restoration of natural limb function, where high dexterity is required for complex movements.