Finger Extension Movements Research Articles

Development of an Electromyography Signal Acquisition Prototype and Statistical Validation Against a Commercial Device.

Electromyography (EMG) stands out as an accessible and inexpensive method for identifying muscle contractions on the surface and within deeper muscle tissues. Using specialized electronic circuits for amplification and filtering can help develop simple but effective systems for detecting and analyzing these signals. However, EMG devices developed by research teams frequently lack rigorous methodologies for validating the quality of the signals they record compared to those obtained by commercial systems that have undergone extensive testing and regulatory approval for market release. This underscores the critical need for standardized validation techniques to reliably assess the performance of experimental devices relative to established commercial equipment. Hence, this study introduces a methodology for the development and statistical validation of a laboratory EMG circuit compared with a professional device available on the market. The experiment simultaneously recorded the muscle electrical activity of 18 volunteers using two biosignal acquisition devices-a prototype EMG and a commercial system-both applied in parallel at the same recording site. Volunteers performed a series of finger and wrist extension movements to elicit myoelectric activity in these forearm muscles. To achieve this, it was necessary to develop not only the EMG signal conditioning board, but also two additional interface boards: one for enabling parallel recording on both devices and another for synchronizing the devices with the task programmatically controlled in Python that the volunteers were required to perform. The EMG signals generated during these tasks were recorded simultaneously by both devices. Subsequently, 22 feature indices commonly used for classifying muscular activity patterns were calculated from two-second temporal windows of the recordings to extract detailed temporal and spatial characteristics. Finally, the Mean Absolute Percentage Error (MAPE) was computed to compare the indices from the prototype with those from the commercial device, using this method as a validation system to assess the quality of the signals recorded by the prototype relative to the commercial equipment. A concordance of 87.6% was observed between the feature indices calculated from the recordings of both devices, suggesting high effectiveness and reliability of the EMG signals recorded by the prototype compared to the commercial device. These results validate the efficacy of our EMG prototype device and provide a solid foundation for the future evaluation of similar devices, ensuring their reliability, accuracy, and suitability for research or clinical applications.

Whole-Head Noninvasive Brain Signal Measurement System with High Temporal and Spatial Resolution Using Static Magnetic Field Bias to the Brain.

Noninvasive brain signal measurement techniques are crucial for understanding human brain function and brain-machine interface applications. Conventionally, noninvasive brain signal measurement techniques, such as electroencephalography, magnetoencephalography, functional magnetic resonance imaging, and near-infrared spectroscopy, have been developed. However, currently, there is no practical noninvasive technique to measure brain function with high temporal and spatial resolution using one instrument. We developed a novel noninvasive brain signal measurement technique with high temporal and spatial resolution by biasing a static magnetic field emitted from a coil on the head to the brain. In this study, we applied this technique to develop a groundbreaking system for noninvasive whole-head brain function measurement with high spatiotemporal resolution across the entire head. We validated this system by measuring movement-related brain signals evoked by a right index finger extension movement and demonstrated that the proposed system can measure the dynamic activity of brain regions involved in finger movement with high spatiotemporal accuracy over the whole brain.

A case of hemiplegia with a cerebrovascular accident in which motor imagery of finger extension on the affected side with finger extension on the unaffected side was effective - A study using F-waves

We investigated the effect of exercise therapy by simultaneously using motor imagery of thumb or all finger extension on the affected side and thumb or all finger extension exercise on the unaffected side by using the F-wave, which is used to measure the excitability of anterior horn cells to devise an appropriate exercise therapy using motor imagery for patients with increased muscle tone of the thumb muscles on the affected side. Tasks 1, 2, 3, and 4 involved motor imagery of thumb extension on the affected side, motor imagery of finger extension on the affected side, motor imagery of thumb extension on the affected side based on thumb extension on the unaffected side, and finger extension on the affected side based on finger extension on the unaffected side, respectively; conducted in three trials, with one week or more between each trial. Each task was performed for one minute, with a five-minute interval between tasks. The F-waves from the thenar muscles were recorded with median nerve stimulation on the affected side before and during the tasks. The relative values of the F-wave data of the task and the F-wave data before (resting state) and during the tasks were calculated. In results, the relative data of the F/M amplitude ratio in task 4 was lower than that in the other tasks in three trials. In conclusion, motor imagery of finger extension on the affected side with finger extension movement on the unaffected side was effective for improving the muscle tone of the thenar muscles on the affected side.

Effect of SaeboTM Orthosis Along with Functional Electrical Stimulation on Hand Function in Patients with Subacute Stroke: A Randomized Controlled Trial

Background: In stroke, there is loss of basic hand function like straightening of the fingers, grip strength andgrasping of the item which make dependent for their basic activity of daily living. The Saebo-FlexTM orthoticis a mechanical device, which enables an individual to open hand, pick up the objects and release during tasksorientedexercises. It facilitating thumb and finger extension movements by recruiting voluntary thumb and fingerflexor movement.Objectives: To determine the effect of FES along with Saebo-FlexTM device on Fugl Meyer assessment score forupper extremity, on Grip Strength, on Pinch Strength and on Hand Dexterity.Methodology: 20 participants were randomly divided into experimental (Saebo-FlexTM hand orthosis + FES +Conventional physiotherapy) and control (FES + conventional physiotherapy) group. Intervention was given for45min/session, 5 session/ week for 6 weeks. Assessment was done using Fugl Meyer assessment-upper extremity,Chedock hand inventory programme, Nine-hole peg test, Hand dynamometer and Pinch gauge on Day 0,Day 12 and Day 42 of the intervention period.Results: The results were found to be non-significant (p>0.05) for all outcome measures. Statistically significantresults were obtained for FMA-UE (p=0.018) on comparison of mean difference scores at Day 0, and Day 42,CAHAI scores (p=0.011) on comparison of mean difference scores at Day 0 and Day 42.Conclusion: According to finding, the integrated intervention of Saebo-FlexTM device along with FunctionalElectrical Stimulation can be used effectively to improve the upper extremity motor functions in sub acute strokesurvivors.

Influence of Visual Stimulation-Induced Passive Reproduction of Motor Images in the Brain on Motor Paralysis After Stroke.

Finger flexor spasticity, which is commonly observed among patients with stroke, disrupts finger extension movement, consequently influencing not only upper limb function in daily life but also the outcomes of upper limb therapeutic exercise. Kinesthetic illusion induced by visual stimulation (KINVIS) has been proposed as a potential treatment for spasticity in patients with stroke. However, it remains unclear whether KINVIS intervention alone could improve finger flexor spasticity and finger extension movements without other intervention modalities. Therefore, the current study investigated the effects of a single KINVIS session on finger flexor spasticity, including its underlying neurophysiological mechanisms, and finger extension movements. To this end, 14 patients who experienced their first episode of stroke participated in this study. A computer screen placed over the patient’s forearm displayed a pre-recorded mirror image video of the patient’s non-paretic hand performing flexion–extension movements during KINVIS. The position and size of the artificial hand were adjusted appropriately to create a perception that the artificial hand was the patient’s own. Before and after the 20-min intervention, Modified Ashworth Scale (MAS) scores and active range of finger extension movements of the paretic hand were determined. Accordingly, MAS scores and active metacarpophalangeal joint extension range of motion improved significantly after the intervention. Moreover, additional experimentation was performed using F-waves on eight patients whose spasticity was reduced by KINVIS to determine whether the same intervention also decreased spinal excitability. Our results showed no change in F-wave amplitude and persistence after the intervention. These results demonstrate the potential clinical significance of KINVIS as a novel intervention for improving finger flexor spasticity and extension movements, one of the most significant impairments among patients with stroke. The decrease in finger flexor spasticity following KINVIS may be attributed to neurophysiological changes not detectable by the F-wave, such as changes in presynaptic inhibition of Ia afferents. Further studies are certainly needed to determine the long-term effects of KINVIS on finger spasticity, as well as the neurophysiological mechanisms explaining the reduction in spasticity.

Functional synergy recruitment index as a reliable biomarker of motor function and recovery in chronic stroke patients

Objective. Stroke affects the expression of muscle synergies underlying motor control, most notably in patients with poorer motor function. The majority of studies on muscle synergies have conventionally approached this analysis by assuming alterations in the inner structures of synergies after stroke. Although different synergy-based features based on this assumption have to some extent described pathological mechanisms in post-stroke neuromuscular control, a biomarker that reliably reflects motor function and recovery is still missing. Approach. Based on the theory of muscle synergies, we alternatively hypothesize that functional synergy structures are physically preserved and measure the temporal correlation between the recruitment profiles of healthy modules by paretic and healthy muscles, a feature hereafter reported as the FSRI. We measured clinical scores and extracted the muscle synergies of both ULs of 18 chronic stroke survivors from the electromyographic activity of 8 muscles during bilateral movements before and after 4 weeks of non-invasive BMI controlled robot therapy and physiotherapy. We computed the FSRI as well as features quantifying inter-limb structural differences and evaluated the correlation of these synergy-based measures with clinical scores. Main results. Correlation analysis revealed weak relationships between conventional features describing inter-limb synergy structural differences and motor function. In contrast, FSRI values during specific or combined movement data significantly correlated with UL motor function and recovery scores. Additionally, we observed that BMI-based training with contingent positive proprioceptive feedback led to improved FSRI values during the specific trained finger extension movement. Significance. We demonstrated that FSRI can be used as a reliable physiological biomarker of motor function and recovery in stroke, which can be targeted via BMI-based proprioceptive therapies and adjuvant physiotherapy to boost effective rehabilitation.

Structure of Population Activity in Primary Motor Cortex for Single Finger Flexion and Extension.

How is the primary motor cortex (M1) organized to control fine finger movements? We investigated the population activity in M1 for single finger flexion and extension, using 7T functional magnetic resonance imaging (fMRI) in female and male human participants and compared these results to the neural spiking patterns recorded in two male monkeys performing the identical task. fMRI activity patterns were distinct for movements of different fingers, but were quite similar for flexion and extension of the same finger. In contrast, spiking patterns in monkeys were quite distinct for both fingers and directions, which is similar to what was found for muscular activity patterns. The discrepancy between fMRI and electrophysiological measurements can be explained by two (non-mutually exclusive) characteristics of the organization of finger flexion and extension movements. Given that fMRI reflects predominantly input and recurrent activity, the results can be explained by an architecture in which neural populations that control flexion or extension of the same finger produce distinct outputs, but interact tightly with each other and receive similar inputs. Additionally, neurons tuned to different movement directions for the same finger (or combination of fingers) may cluster closely together, while neurons that control different finger combinations may be more spatially separated. When measuring this organization with fMRI at a coarse spatial scale, the activity patterns for flexion and extension of the same finger would appear very similar. Overall, we suggest that the discrepancy between fMRI and electrophysiological measurements provides new insights into the general organization of fine finger movements in M1.SIGNIFICANCE STATEMENT The primary motor cortex (M1) is important for producing individuated finger movements. Recent evidence shows that movements that commonly co-occur are associated with more similar activity patterns in M1. Flexion and extension of the same finger, which never co-occur, should therefore be associated with distinct representations. However, using carefully controlled experiments and multivariate analyses, we demonstrate that human fMRI activity patterns for flexion or extension of the same finger are highly similar. In contrast, spiking patterns measured in monkey M1 are clearly distinct. This suggests that populations controlling opposite movements of the same finger, while producing distinct outputs, may cluster together and share inputs and local processing. These results provide testable hypotheses about the organization of hand control in M1.

Lesion Topography Impact on Shoulder Abduction and Finger Extension Following Left and Right Hemispheric Stroke.

The existence of shoulder abduction and finger extension movement capacity shortly after stroke onset is an important prognostic factor, indicating favorable functional outcomes for the hemiparetic upper limb (HUL). Here, we asked whether variation in lesion topography affects these two movements similarly or distinctly and whether lesion impact is similar or distinct for left and right hemisphere damage. Shoulder abduction and finger extension movements were examined in 77 chronic post-stroke patients using relevant items of the Fugl-Meyer test. Lesion effects were analyzed separately for left and right hemispheric damage patient groups, using voxel-based lesion-symptom mapping. In the left hemispheric damage group, shoulder abduction and finger extension were affected only by damage to the corticospinal tract in its passage through the corona radiata. In contrast, following the right hemispheric damage, these two movements were affected not only by corticospinal tract damage but also by damage to white matter association tracts, the putamen, and the insular cortex. In both groups, voxel clusters have been found where damage affected shoulder abduction and also finger extension, along with voxels where damage affected only one of the two movements. The capacity to execute shoulder abduction and finger extension movements following stroke is affected significantly by damage to shared and distinct voxels in the corticospinal tract in left-hemispheric damage patients and by damage to shared and distinct voxels in a larger array of cortical and subcortical regions in right hemispheric damage patients.

Closed-loop neuromuscular electrical stimulation using feedforward-feedback control and textile electrodes to regulate grasp force in quadriplegia

BackgroundTranscutaneous neuromuscular electrical stimulation is routinely used in physical rehabilitation and more recently in brain-computer interface applications for restoring movement in paralyzed limbs. Due to variable muscle responses to repeated or sustained stimulation, grasp force levels can change significantly over time. Here we develop and assess closed-loop methods to regulate individual finger forces to facilitate functional movement. We combined this approach with custom textile-based electrodes to form a light-weight, wearable device and evaluated in paralyzed study participants.MethodsA textile-based electrode sleeve was developed by the study team and Myant, Corp. (Toronto, ON, Canada) and evaluated in a study involving three able-body participants and two participants with quadriplegia. A feedforward-feedback control structure was designed and implemented to accurately maintain finger force levels in a quadriplegic study participant.ResultsIndividual finger flexion and extension movements, along with functional grasping, were evoked during neuromuscular electrical stimulation. Closed-loop control methods allowed accurate steady state performance (< 15% error) with a settling time of 0.67 s (SD = 0.42 s) for individual finger contact force in a participant with quadriplegia.ConclusionsTextile-based electrodes were identified to be a feasible alternative to conventional electrodes and facilitated individual finger movement and functional grasping. Furthermore, closed-loop methods demonstrated accurate control of individual finger flexion force. This approach may be a viable solution for enabling grasp force regulation in quadriplegia.Trial registrationNCT, NCT03385005. Registered Dec. 28, 2017

Reflections of mirror therapy on the functional recovery after stroke

Introduction Motor function after stroke is improved after mirror therapy. During mirror therapy, a mirror is placed in the mid-sagittal plane thus reflecting movements of non-paretic side as if it were the affected side. Objectives To evaluate the effectiveness of mirror therapy on upper extremity motor recovery and hand related functioning of patients with sub-acute stroke. Method A total of 60 patients with stroke were randomly selected, all within 6 months post stroke, with 30 patients in each, experimental and control group. Each day, 30 min of mirror therapy was given to patients in experimental group consisting of wrist and finger flexion and extension movements in addition to conventional stroke rehabilitation program, 6 days a week, 1 h a day for 4 weeks, while those in control group didn't receive mirror therapy program. Main Outcome Measures- The Brunnstrom stages of motor recovery & Hand- related functioning (Self-care items of FIM instrument) Results Mean age of the patients was 55 years. The scores of the Brunnstrom stages for hand and upper extremity and FIM self - care score improved more in experimental group than in control group after 4 weeks of treatment (by 0.81, 0.86 and 4.1 respectively; all P Conclusion Hand functioning improved more after mirror therapy compared with control group after 4 weeks of treatment and at 6 month follow up.

Finger Joint Angle Estimation Based on Motoneuron Discharge Activities.

Estimation of joint kinematics plays an important role in intuitive human-machine interactions. However, continuous and reliable estimation of small (e.g., the finger) joint angles is still a challenge. The objective of this study was to continuously estimate finger joint angles using populational motoneuron firing activities. Multi-channel surface electromyogram (sEMG) signals were obtained from the extensor digitorum communis muscles, while the subjects performed individual finger oscillatory extension movements at two different speeds. The individual finger movement was first classified based on the EMG signals. The discharge timings of individual motor units were extracted through high-density EMG decomposition, and were then pooled as a composite discharge train. The firing frequency of the populational motor unit firing events was used to represent the descending neural drive to the motor unit pool. A second-order polynomial regression was then performed to predict the measured metacarpophalangeal extension angle using the derived neural drive based on the neuronal firings. Our results showed that individual finger extension movement can be classified with >96% accuracy based on multi-channel EMG. The extension angles of individual fingers can be predicted continuously by the derived neural drive with R2 values >0.8. The performance of the neural-drive-based approach was superior to the conventional EMG-amplitude-based approach, especially during fast movements. These findings indicated that the neural-drive-based interface was a promising approach to reliably predict individual finger kinematics.

Estimation of Finger Joint Angle Based on Neural Drive Extracted from High-Density Electromyography.

Robust human-machine interactions require accurate and intuitive interfaces. Neural signals associated with muscle activities are widely used as the interface signals. This preliminary study evaluated the feasibility of a novel neural-drive-based interface in estimating the individual finger joint angles. The motor unit pool discharge probability was used to predict the neural drive associated with the fine control of the finger joint angle during individual finger extension movement. To obtain the neural drive information, individual motor unit discharge events were extracted from the decomposition of high-density surface electromyogram (sEMG) signals, and discharge events from different motor units were pooled to from a composite discharge event train. The neural-drive-based estimate was obtained by calculating the probability (normalized frequency) of the populational motor unit discharge. The global EMG signal (root-mean-squared value) was also used to estimate the joint angles as a control condition. Our preliminary results showed that the accuracy and stability of the neural-drive-based approach outperformed the classic EMG-based method. Our findings suggest that the novel neural-drive-based interface could be used as a promising control input for intuitive dynamic control of a robotic hand.

Temporal and Spatial Variability of Surface Motor Activation Zones in Hemiplegic Patients During Functional Electrical Stimulation Therapy Sessions.

The goal of this study was to investigate surface motor activation zones and their temporal variability using an advanced multi-pad functional electrical stimulation system. With this system motor responses are elicited through concurrent activation of electrode matrix pads collectively termed "virtual electrodes" (VEs) with appropriate stimulation parameters. We observed VEs used to produce selective wrist, finger, and thumb extension movements in 20 therapy sessions of 12 hemiplegic stroke patients. The VEs which produce these three selective movements were created manually on the ergonomic multi-pad electrode by experienced clinicians based on visual inspection of the muscle responses. Individual results indicated that changes in VE configuration were required each session for all patients and that overlap in joint movements was evident between some VEs. However, by analyzing group data, we defined the probability distribution over the electrode surface for the three VEs of interest. Furthermore, through Bayesian logic we obtained preferred stimulation zones that are in accordance with our previously reported heuristically obtained results. We have also analyzed the number of active pads and stimulation amplitudes for these three VEs. Presented results provide a basis for an automated electrode calibration algorithm built on a priori knowledge or the starting point for manual selection of stimulation points.

Magnetic resonance imaging combined with diffusion tensor tractography can improve prognosis after ischemic stroke

Objective To explore the pattern of functional reorganization in the cortex after corticospinal tract (CST) injury and its relationship with the recovery of upper limb motor function. Methods Fifteen patients with complete paralysis on one side after acute cerebral infarction were studied. Within 1 week after the onset, functional magnetic resonance imaging (fMRI ) and diffusion tensor tractography (DTT) were performed in parallel with timed finger flexion and extension movements in all subjects. The number of nerve fibers in corticospinal tract (CST) in the affected and healthy sides was measured by using Dtv.Ⅱ.R2 software.One and three months later, fMRI was performed while the affected fingers were flexed and extended passively and any cortical activation was observed. In addition, Fugl-Meyer arm motor function scores were assessed one week, one month and three months after the stroke. Results According to the reconstructed nerve fiber number in CST on the affected side, the patients were classified into three types. Type I: the number of newly-built CST nerve fibers is more than 2/3 of that on the healthy side; type II: the ratio is between 1/3 and 2/3; and type III: the ratio is less than 1/3. For typeⅠpatients, blood oxygenation level-dependent fMRI (bold-fMRI) showed initial activation of the bilateral sensorimotor cortex (SMC) and the supplementary motor area (SMA) on the affected side. That was followed by a gradual decrease in the activity in the healthy SMC and an increase in the affected SMC at 1 and 3 months. Among the type II patients bold-fMRI indicated activation of the SMC and SMA on the affected side initially, significant activation of the bilateral SMC and SMA one month later and then stronger activation in the SMC on the healthy side and a weakening of activation in the SMC on the affected side. For type Ⅲ patients, initially the SMA and the posterior parietal cortex were found to be slightly activated. One month later SM1 on the unaffected side was slightly activated, and 3 months later neither the SMC nor the SMA on either side was activated. One week after the onset, the average upper extremity FM scores of the three types of subjects were not significantly different. After one month the three groups′ averages were all significantly different from one another. But after three months the averages for types I and II were again not significantly different, but significantly better than the average of the type III patients. Conclusion Different CST injuries induce different modes of cortical reorganization. The reorganization is a dynamic process, and different activation patterns are closely correlated with clinical prognosis. Key words: Stroke; Functional magnetic resonance imaging; Tractography; Brain reorganization

Principles of tendon transfers

Tendon transfers are carried out to restore functional deficits by rerouting the remaining intact muscles. Transfers are highly attractive in the context of hand surgery because of the possibility of restoring the patient's ability to grip. In palsy cases, tendon transfers are only used when a neurological procedure is contraindicated or has failed. The strategy used to restore function follows a common set of principles, no matter the nature of the deficit. The first step is to clearly distinguish between deficient muscles and muscles that could be transferred. Next, the type of palsy will dictate the scope of the program and the complexity of the gripping movements that can be restored. Based on this reasoning, a surgical strategy that matches the means (transferable muscles) with the objectives (functions to restore) will be established and clearly explained to the patient. Every paralyzed hand can be described using three parameters. 1) Deficient segments: wrist, thumb and long fingers; 2) mechanical performance of muscles groups being revived: high energy–wrist extension and finger flexion that require strong transfers with long excursion; low energy–wrist flexion and finger extension movements that are less demanding mechanically, because they can be accomplished through gravity alone in some cases; 3) condition of the two primary motors in the hand: extrinsics (flexors and extensors) and intrinsics (facilitator). No matter the type of palsy, the transfer surgery follows the same technical principles: exposure, release, fixation, tensioning and rehabilitation. By performing an in-depth analysis of each case and by following strict technical principles, tendon transfer surgery leads to reproducible results; this allows the surgeon to establish clear objectives for the patient preoperatively.

Phantom hand and wrist movements in upper limb amputees are slow but naturally controlled movements

After limb amputation, patients often wake up with a vivid perception of the presence of the missing limb, called “phantom limb”. Phantom limbs have mostly been studied with respect to pain sensation. But patients can experience many other phantom sensations, including voluntary movements. The goal of the present study was to quantify phantom movement kinematics and relate these to intact limb kinematics and to the time elapsed since amputation. Six upper arm and two forearm amputees with various delays since amputation (6months to 32years) performed phantom finger, hand and wrist movements at self-chosen comfortable velocities. The kinematics of the phantom movements was indirectly obtained via the intact limb that synchronously mimicked the phantom limb movements, using a Cyberglove® for measuring finger movements and an inertial measurement unit for wrist movements. Results show that the execution of phantom movements is perceived as “natural” but effortful. The types of phantom movements that can be performed are variable between the patients but they could all perform thumb flexion/extension and global hand opening/closure. Finger extension movements appeared to be 24% faster than finger flexion movements. Neither the number of types of phantom movements that can be executed nor the kinematic characteristics were related to the elapsed time since amputation, highlighting the persistence of post-amputation neural adaptation. We hypothesize that the perceived slowness of phantom movements is related to altered proprioceptive feedback that cannot be recalibrated by lack of visual feedback during phantom movement execution.

Brain functional plasticity at rest and during action in multiple sclerosis patients

We aimed to demonstrate that basal functional connectivity reorganization observed in a specific network at rest using resting state functional MRI (rs-fMRI) could be associated with functional cortical reorganization in such network during action (ta-fMRI) in a population of early multiple sclerosis (MS) patients. Altered basal functional connectivity has been previously reported in patients with MS but relationships with cortical reorganization during action have not been explored. Thirteen patients with early relapsing-remitting MS and 14 matched healthy controls were explored on a 3T MRI scanner at rest and during a motor task (conjugate finger flexion and extension movements of each hand). Hand motor networks were extracted from rs-fMRI data using group spatial independent component analysis. For the non-dominant motor network, patients presented a higher basal functional connectivity at rest and recruited a supplementary prefrontal cortical area during action compared to the controls. The levels of hyperconnectivity at rest and of activation in the recruited area during action were significantly correlated. No differences were demonstrated for the dominant motor network at rest and during action. The present study, combining rs-fMRI and ta-fMRI in non-disabled patients with early MS, revealed for the first time a direct association between functional reorganization depicted at rest and during action within the same system.

Continuous and simultaneous estimation of finger kinematics using inputs from an EMG-to-muscle activation model.

BackgroundSurface electromyography (EMG) signals are often used in many robot and rehabilitation applications because these reflect motor intentions of users very well. However, very few studies have focused on the accurate and proportional control of the human hand using EMG signals. Many have focused on discrete gesture classification and some have encountered inherent problems such as electro-mechanical delays (EMD). Here, we present a new method for estimating simultaneous and multiple finger kinematics from multi-channel surface EMG signals.MethodIn this study, surface EMG signals from the forearm and finger kinematic data were extracted from ten able-bodied subjects while they were tasked to do individual and simultaneous multiple finger flexion and extension movements in free space. Instead of using traditional time-domain features of EMG, an EMG-to-Muscle Activation model that parameterizes EMD was used and shown to give better estimation performance. A fast feed forward artificial neural network (ANN) and a nonparametric Gaussian Process (GP) regressor were both used and evaluated to estimate complex finger kinematics, with the latter rarely used in the other related literature.ResultsThe estimation accuracies, in terms of mean correlation coefficient, were 0.85±0.07, 0.78±0.06 and 0.73±0.04 for the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and the distal interphalangeal (DIP) finger joint DOFs, respectively. The mean root-mean-square error in each individual DOF ranged from 5 to 15%. We show that estimation improved using the proposed muscle activation inputs compared to other features, and that using GP regression gave better estimation results when using fewer training samples.ConclusionThe proposed method provides a viable means of capturing the general trend of finger movements and shows a good way of estimating finger joint kinematics using a muscle activation model that parameterizes EMD. The results from this study demonstrates a potential control strategy based on EMG that can be applied for simultaneous and continuous control of multiple DOF(s) devices such as robotic hand/finger prostheses or exoskeletons.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-122) contains supplementary material, which is available to authorized users.

Multimodal sensory feedback associated with motor attempts alters BOLD responses to paralyzed hand movement in chronic stroke patients.

Electroencephalogram-based brain-computer interfaces (BCI) have been used as a potential tool for training volitional regulation of corticomuscular drive in patients who have severe hemiplegia due to stroke. However, it is unclear whether ERD observed while attempting motor execution can be regarded as a neural marker that represents M1 excitability in survivors of severe stroke. Therefore we investigated the association between ERD and the blood-oxygen-level-dependent (BOLD) fMRI signal during attempted movement of a paralyzed finger in stroke patients. Nine chronic stroke patients received BCI training for finger extension movement 1h daily for a duration of 1month. The sensorimotor rhythm was recorded from the sensorimotor area of the damaged hemisphere, and ongoing amplitude variations were monitored using a BCI system. Either a visual alert or the action of a motor-driven orthosis was triggered in response to ERD of the sensorimotor rhythm while patients attempted extension movements of the paralyzed fingers. Inter-subject covariance between ERD and the BOLD response in the sensorimotor areas was calculated. After BCI training, an increased ERD over the damaged hemisphere was confirmed in all participants while they attempted extension of the affected finger and this increase was associated with a BOLD response in primary sensorimotor area. Whole-brain MRI revealed that the primary sensorimotor area and supplementary motor area were activated in the damaged hemisphere after 1month of BCI training. ERD reflects the BOLD responses of the primary motor areas in either hemisphere while patients who have severe chronic hemiplegia due to a stroke attempt an extension movement of the paralyzed fingers. One month of BCI can alter motor-related brain area activation. Combining BCI with other methods to facilitate such changes may help to implement BCI for motor rehabilitation after stroke.

Node Accessibility in Cortical Networks During Motor Tasks

Recent findings suggest that the preparation and execution of voluntary self-paced movements are accompanied by the coordination of the oscillatory activities of distributed brain regions. Here, we use electroencephalographic source imaging methods to estimate the cortical movement-related oscillatory activity during finger extension movements. Then, we apply network theory to investigate changes (expressed as differences from the baseline) in the connectivity structure of cortical networks related to the preparation and execution of the movement. We compute the topological accessibility of different cortical areas, measuring how well an area can be reached by the rest of the network. Analysis of cortical networks reveals specific agglomerates of cortical sources that become less accessible during the preparation and the execution of the finger movements. The observed changes neither could be explained by other measures based on geodesics or on multiple paths, nor by power changes in the cortical oscillations.