Wrist Extension Movements Research Articles

Closed-Loop Multi-Amplitude Control for Robust and Dexterous Performance of Myoelectric Prosthesis.

In the case of a hand amputation, the affected person can use a myoelectric prosthesis to substitute the missing limb and regain motor functions. Unfortunately, commercial methods for myoelectric control, although robust and simple, are unintuitive and cognitively taxing when applied to an advanced multi-functional prosthesis. The state-of-the-art methods developed in academia are based on machine learning and therefore require long training and suffer from a lack of robustness. This work presents a novel closed-loop multi-level amplitude controller (CMAC), which aims at overcoming these drawbacks. The CMAC implements three degrees-of-freedom (DoF) control by thresholding the muscle contraction intensity during wrist flexion and extension movements. Unique features of the controller are the vibrotactile feedback that communicates the state of the controller to the user and a scheme for proportional control. These components allow exploiting the full dexterity of the prosthesis using a simple two-channel myoelectric interface. The CMAC was compared to a commonly implemented pattern-recognition method (linear discriminant analysis - LDA) using clinically relevant tests in 12 able-bodied and 2 amputee subjects. The experimental assessment demonstrated that CMAC was similarly fast as LDA in dexterous tests (clothespin and cube manipulation), while it was somewhat slower than LDA during a simple, single DoF task (box and blocks). In addition, in all the tasks, LDA and CMAC resulted in a similarly low error rate. On the other hand, to an amputee that could not generate six distinguishable classes using LDA, the CMAC still enabled the control of all the prosthesis DoFs. Importantly, the overall setup and training time in CMAC were significantly lower compared to LDA. In conclusion, the novel method is convenient for clinical applications, and allows substantially higher control dexterity compared to what can be normally achieved using conventional two channel EMG. Therefore, CMAC provides performance comparable to advanced machine-learning algorithms and the robustness and ease of use that is characteristic for the simple two-channel myoelectric interface.

Neural gain induced by startling acoustic stimuli is additive to preparatory activation.

Loud acoustic stimuli presented during movement preparation can shorten reaction time and increase response forcefulness. We examined how efferent connectivity of an agonist muscle to reticulospinal and corticospinal pathways, and the level of prepared movement force, affect reaction time and movement execution when the motor response is triggered by an intense acoustic stimulus. In Experiment 1, participants executed ballistic wrist flexion and extension movements of low and high force in response to visual stimuli. A loud acoustic stimulus (LAS; 105dBa) was presented simultaneously with the visual imperative stimulus in probe trials. In Experiment 2, participants executed ballistic wrist flexion movements ranging from 10%-50% of maximum voluntary contraction with a LAS presented in probe trials. The shortening of response initiation was not affected by movement type (flexion or extension) or prepared movement force. Enhancement of response magnitude, however, was proportionally greater for low force movements and for the flexor muscle. Changes in peak force induced by the intense acoustic stimulus indicated that the neural activity introduced to motor program circuits by acoustic stimulation is additive to the voluntary neural activity that occurs due to movement preparation, rather than multiplicative.

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.

Elicited Finger and Wrist Extension Through Transcutaneous Radial Nerve Stimulation.

Individuals with neurological disorders, such as stroke or spinal cord injury, often have weakness and/or spasticity in their hand and wrist muscles, which can lead to impaired ability to extend their fingers and wrists. Functional electrical stimulation can help to restore these motor functions. However, the conventional stimulation method can lead to fast muscle fatigue and limited movements due to a non-physiological recruitment of motor units and a limited recruitment of deep muscles. In this paper, we investigated the feasibility of eliciting various hand opening and wrist extension movement patterns through a transcutaneous electrical stimulation array, which targeted the proximal segment of the radial nerve bundle proximal to the elbow. The wrist and finger joint kinematics were used to classify the different movement patterns through a cluster analysis, and electromyogram signals from the wrist and finger extensors were recorded to investigate the muscle activation patterns. The results showed that the finger and wrist motions can be elicited both independently and in a coordinated manner, by changing the stimulation intensity and stimulation location. H-reflex activity was also observed, which demonstrated the potential of recruiting motor units in a physiological order. Our approach could be further developed into a rehabilitative/assistive tool for individuals with impaired hand opening and/or wrist extension.

Changes in mu and beta amplitude of the EEG during upper limb movement correlate with motor impairment and structural damage in subacute stroke

ObjectiveMu and beta EEG oscillations show typical desynchronization patterns during movement. The aim of the current study was to assess whether in sub-acute stroke patients the magnitude of movement-related desynchronization reflects the extent of residual motor ability in the paretic upper limb. MethodsEEG and EMG data were recorded from 14 first-event stroke patients during repeated wrist extension movements of the paretic upper limb. Residual motor ability was assessed by the Fugl Meyer and Box and Blocks standardized clinical tests. Normalized lesion data was analyzed using the MEDx software. ResultsThe magnitude of event-related de-synchronization (ERD) of the high-mu and low-beta bands of the EEG, measured over the affected hemisphere, correlated significantly with (a) residual motor function in the paretic upper limb as measured by standard clinical tests; (b) the magnitude of EMG recorded from the paretic upper limb during wrist extension; and (c) the total hemispheric volume loss (negative correlation). ConclusionThe magnitude of high-mu and low-beta ERD recorded from the lesioned hemisphere of subacute stroke patients correlates with residual motor ability in the paretic upper limb. SignificanceMeasures derived from quantitative EEG analysis may play an important role in neurorehabilitation clinical practice.

Muscle fatigue assessment during robot-mediated movements

BackgroundSeveral neuromuscular disorders present muscle fatigue as a typical symptom. Therefore, a reliable method of fatigue assessment may be crucial for understanding how specific disease features evolve over time and for developing effective rehabilitation strategies. Unfortunately, despite its importance, a standardized, reliable and objective method for fatigue measurement is lacking in clinical practice and this work investigates a practical solution.Methods40 healthy young adults performed a haptic reaching task, while holding a robotic manipulandum. Subjects were required to perform wrist flexion and extension movements in a resistive visco-elastic force field, as many times as possible, until the measured muscles (mainly flexor and extensor carpi radialis) exhibited signs of fatigue. In order to analyze the behavior and the characteristics of the two muscles, subjects were divided into two groups: in the first group, the resistive force was applied by the robot only during flexion movements, whereas, in the second group, the force was applied only during extension movements. Surface electromyographic signals (sEMG) of both flexor and extensor carpi radialis were acquired. A novel indicator to define the Onset of Fatigue (OF) was proposed and evaluated from the Mean Frequency of the sEMG signal. Furthermore, as measure of the subjects’ effort throughout the task, the energy consumption was estimated.ResultsFrom the beginning to the end of the task, as expected, all the subjects showed a decrement in Mean Frequency of the muscle involved in movements resisting the force. For the OF indicator, subjects were consistent in terms of timing of fatigue; moreover, extensor and flexor muscles presented similar OF times. The metabolic analysis showed a very low level of energy consumption and, from the behavioral point of view, the test was well tolerated by the subjects.ConclusionThe robot-aided assessment test proposed in this study, proved to be an easy to administer, fast and reliable method for objectively measuring muscular fatigue in a healthy population. This work developed a framework for an evaluation that can be deployed in a clinical practice with patients presenting neuromuscular disorders. Considering the low metabolic demand, the requested effort would likely be well tolerated by clinical populations.

A Timeline of Motor Preparatory State Prior to Response Initiation: Evidence from Startle

Response preparation in simple reaction time (RT) tasks has been modeled as an increase in neural activation to a sub-threshold level, which is maintained until the go-signal. However, the amount of time required for response preparation following a warning signal (WS) is currently unclear, as experiments typically employ long foreperiods to ensure maximal preparation. The purpose of the present experiments was to examine the time course of motor preparation in a simple RT task when given a limited amount of time to engage in preparatory processing. In Experiment 1, participants completed wrist extension movements in a simple RT paradigm with a short (500 ms) fixed foreperiod, and a long (8.5–10.5 s) inter-trial interval. To probe response preparation, a startling acoustic stimulus (SAS), which involuntarily triggers the release of sufficiently prepared responses, was randomly presented during the foreperiod at one of six equally spaced time points between 0 and 500 ms prior to the go-signal. Results showed that the long inter-trial interval was not always effective at preventing participants from engaging in preparatory processing between trials; thus, in Experiment 2 participants performed wrist flexion or extension movements in an instructed delay paradigm, where the required movement was cued by the WS. Results showed that the proportion of startle trials where the intended response was elicited by the SAS at short latency significantly increased until 100 ms prior to the go-signal, indicating response preparation can take up to 300–400 ms following the WS in a simple RT task with a short fixed foreperiod.

Neurophysiological effects of mirror visual feedback in stroke patients with unilateral hemispheric damage

Background and ObjectiveMirror visual feedback (MVF; the illusory perception of movement in one hand upon viewing the moving opposite hand in a midsagittal mirror) is thought to facilitate restoration of mal-adaptive neurophysiological processes underlying conditions like complex regional pain syndrome and phantom limb pain, and to have a positive effect on brain plasticity processes underlying motor recovery after stroke. However, its exact mode of action remains unclear. The aim of the current study was to explore the immediate neurophysiological effects of MVF in patients with stroke-related hemiparesis. We also investigated how these effects relate to lesion location and extent. MethodEEG and EMG data were obtained from 14 first-event sub-acute stroke patients (8 with right-, 6 with left-hemiparesis) during repeated wrist extension movements of the Non-paretic Upper-Limb (NUL), without (NUL/M-) and with (NUL/M+) a midsagittal mirror, as well as during bilateral movements with a mirror (Bil/M+). EEG data was correlated with normalized lesion data obtained from follow-up CT scans. ResultsNUL movement was accompanied by an asymmetric event-related de-synchronization (ERD) of low-beta EEG oscillations, with a more conspicuous ERD in the non-affected hemisphere. In the mirror condition, ERD magnitude was attenuated in both hemispheres. Stronger attenuation in the non-affected hemisphere abolished the hemispheric asymmetry. ERD attenuation by the mirror was affected by lesion side, the severity of hemiparesis and by lesion location and extent. ConclusionFollowing hemispheric stroke, the magnitude of low-beta ERD accompanying unilateral movement of the non-involved upper limb, and its hemispheric asymmetry, are both reduced by MVF. Low-beta ERD dynamics may serve as a marker of neurophysiological response to MVF in research aimed to elucidate the factors influencing patients’ clinical gain from this treatment.

T151. Visuospatial processing load enhance the brain activity associated with motor preparation

Introduction A cortical region showing an event-related desynchronization (ERD) in the electroencephalographic (EEG) alpha power indicates that it is activated in preparation for voluntary movements. The aim of this study is to search for visual and spatial condition that degree and distribution of alpha band ERD by loading greater spatial attention with movement. Methods We measured movement-related ERD of scalp EEG over central to occipital areas. Just like Libet’s Clock paradigm, subjects were seated in front of a computer screen that displayed a clock rotating at 3 s per cycle. They were instructed to register in mind the onset time of the self-paced movement. After the movement, they reported the position of the clock when the movement took place. [Measurement 1] Two types of movement tasks were executed while the clock rotating direction is clockwise. In reaching trials, subjects reached the center of the screen with their right hand. In control trials, subjects performed a simple right wrist extension on the chair armrest. [Measurement 2] A wrist extension movement with right and left hand was performed in each of two kinds of rotating directions (clockwise and counterclockwise) of clock. Data analysis: We analyzed the effect of clock position, clock rotating direction, electrode position, side of hand, and type of movement to the EEG activity before the movement onset. The time-frequency representation of the EEG power was calculated using short-time Fourier transformation. Results [Measurement 1] In wrist extension, alpha band ERD was significantly greater in bilateral parieto-occipital area when clock position was in the left visual field (LVF) (while the clock is moving up) compared with the right visual field (RVF) (while the clock is moving down). Reaching trials showed the significant alpha band ERD in bilateral parieto-occipital area in both trials of LVF and RVF. [Measurement 2] There was a significant interaction between clock rotating direction and clock position that showed alpha band ERD in bilateral parieto-occipital area when the clock is moving up was significantly greater than that when the clock is moving down. This modulation is in common for the both left hand right hand movement. The common finding in measurement 1 and 2 is that alpha band ERD in the posterior area was greater in ipsilateral hemisphere to attended visual hemi-field compared with contralateral hemisphere. Conclusion We showed that alpha band power at motor preparation stage was significantly altered in posterior cortex by applying an appropriate spatial load in peripheral visual field without changing the movement itself.

Convergent Spinal Circuits Facilitating Human Wrist Flexors.

Noninvasive assessment of spinal circuitry in humans is limited, especially for Ib pathways in the upper limb. We developed a protocol in which we evoke the H-reflex in flexor carpi radialis (FCR) by median nerve stimulation and condition it with electrical stimulation above motor threshold over the extensor carpi radialis (ECR) muscle belly. Eighteen healthy adults (8 male, 10 female) took part in the study. There was a clear reflex facilitation at a 30 ms interstimulus interval (ISI) and suppression at a 70 ms ISI, which was highly consistent across subjects. We investigated the following two hypotheses of the possible source of the facilitation: (1) ECR Ib afferents from Golgi tendon organs, activated by the twitch following ECR stimulation; and (2) FCR afferents, from spindles and/or Golgi tendon organs, activated by the wrist extension movement that follows ECR stimulation. Several human and monkey experiments indicated a role for both of these sets of afferents. Our results provide evidence for a spinal circuit in which flexor motoneurons receive convergent excitatory input from flexor afferents as well as from extensor Ib afferents; this circuit can be straightforwardly assessed noninvasively in humans.SIGNIFICANCE STATEMENT Here we described a novel spinal circuit, which is easy to assess noninvasively in humans. Understanding this circuit in more detail could be beneficial for the design of clinical tests in neurological conditions.

Physical impairments predict hand dexterity function after distal radius fractures: A 2-year prospective cohort study

Introduction The overall aim of this study was to determine whether physical impairments – loss of range of motion and grip strength – could be used to predict hand dexterity functions in patients at 1 and 2 years after distal radius fracture. Methods This was a prospective cohort study. Hand dexterity was assessed at three different levels using the NK hand dexterity test. We used a manual goniometer to measure the active range of motion in the affected hand for wrist flexion and extension movements, and a J-Tech grip strength device to measure patients’ hand grip strength levels. Assessments were performed at 1- and 2-year follow-ups. Separate multivariable regression analyses were performed to determine if range of motion predicts hand dexterity functions at 1 and 2 years after distal radius fracture. Results A total of 160 patients with distal radius fracture were included in this study. Range of motion (flexion and extension) and grip strength were both statistically significant (p < 0.05) independent variables in predicting hand dexterity functions at all three levels among patients after distal radius fracture at 1-year follow-up. Range of motion and strength levels accounted for 31%, 33% and 22% of the variance in patients’ large, medium and small hand dexterity functions, respectively. At 2 years, grip strength remained the only statistically significant (p < 0.001) independent variable in predicting hand dexterity functions at all three levels. Conclusions Physical impairments (loss of range of motion and grip strength) have higher predictive values for large and medium hand dexterity functions, than small hand dexterity functions, in patients after distal radius fracture, at both 1- and 2-year follow-up periods.

Innovative STRoke Interactive Virtual thErapy (STRIVE) online platform for community-dwelling stroke survivors: a randomised controlled trial protocol

IntroductionThe STRoke Interactive Virtual thErapy (STRIVE) intervention provides community-dwelling stroke survivors access to individualised, remotely supervised progressive exercise training via an online platform. This trial aims to determine the clinical...

Functional near-infrared spectroscopy to probe sensorimotor region activation during electrical stimulation-evoked movement.

In eight healthy male volunteers, fNIRS was used to measure relative changes in oxyhaemoglobin (O2 Hb) and deoxyhaemoglobin (HHb) concentrations from a cortical sensorimotor region of interest in the left (LH) and right (RH) hemispheres during NMES-evoked and VOL wrist extension movements of the right arm. NMES-evoked movements induced significantly greater activation (increase in O2 Hb and concomitant decrease in HHb) in the contralateral LH than in the ipsilateral RH (O2 Hb: 0·44±0·16μM and 0·25±0·22μM, P=0·017; HHb: -0·19±0·10μM and -0·12±0·09μM, P=0·036, respectively) as did VOL movements (0·51±0·24 μΜ and 0·34±0·21μM, P=0·031; HHb: -0·18±0·07 μΜ and -0·12±0·04 μΜ, P=0·05, respectively). There was no significant difference between conditions for O2 Hb (P=0·144) and HHb (P=0·958). fNIRS neuroimaging enables quantification of bilateral sensorimotor regional activation profiles during voluntary and NMES-evoked wrist extension movements.

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.

Control of wrist movement in deafferented man: evidence for a mixed strategy of position and amplitude control

There is a continuing debate about control of voluntary movement, with conflicted evidence about the balance between control of movement vectors (amplitude control) that implies knowledge of the starting position for accuracy, and equilibrium point or final position control, that is independent of the starting conditions. We tested wrist flexion and extension movements in a man with a chronic peripheral neuronopathy that deprived him of proprioceptive knowledge of his wrist angles. In a series of experiments, we demonstrate that he could scale the amplitude of his wrist movements in flexion/extension, even without visual feedback, and appeared to adopt a strategy of moving via a central wrist position when asked to reach target angles from unknown start locations. When examining the relationship between positional error at the start and end of each movement in long sequences of movements, we report that he appears to have three canonical positions that he can reach relatively successfully, in flexion, in extension and in the centre. These are consistent with end-point or position control. Other positions were reached with errors that suggest amplitude control. Recording wrist flexor and extensor EMG confirmed that the flexion and extension canonical positions were reached by strong flexor and extensor activity, without antagonist activity, and other positions were reached with graded muscle activation levels. The central canonical position does not appear to be reached by either maximal co-contraction or by complete relaxation, but may have been reached by matched low-level co-contraction.

Effects of monoaminergic drugs on training-induced motor cortex plasticity in older adults

Primary motor cortex (M1) plasticity is involved in motor learning and stroke motor recovery, and enhanced by increasing monoaminergic transmission. Age impacts these processes but there is a paucity of systematic studies on the effects of monoaminergic drugs in older adults. Here, in ten older adults (age 61+4years, 4 males), we determine the effects of a single oral dose of carbidopa/levodopa (DOPA), d-amphetamine (AMPH), methylphenidate (MEPH) and placebo (PLAC) on M1 excitability and motor training-induced M1 plasticity. M1 plasticity is defined as training related long lasting changes in M1 excitability and kinematics of the trained movement. At peak plasma level of the drugs, subjects trained wrist extension movements for 30min. Outcome measures were motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation at increasing intensity (stimulus response curve, SRC) and peak acceleration of the trained wrist extension movements. Measures were obtained before and after completion of training. The curve parameters plateau (MEPmax), inflection point, and slope were extracted from SRC. At baseline drugs had a differential effect on curve parameters, while kinematics remained unchanged. Training alone (PLAC) increased MEPmax but did not improve kinematics. Drugs affected training-related changes of the curve parameters differently, but did not enhance them or kinematics when compared to PLAC. The results demonstrate that in the older adults, MEPH, DOPA, or AMPH have differential effects on baseline M1 excitability and training-related M1 plasticity but fail to enhance them above the naïve level.

Evolution of Surface Motor Activation Zones in Hemiplegic Patients During 20 Sessions of FES Therapy with Multi-pad Electrodes.

The purpose of this study was to examine surface motor activation zones for wrist, fingers and thumb extension movements and their temporal change during 20 therapy sessions using advanced multi-pad functional electrical stimulation system. Results from four hemiplegic patients indicate that certain zones have higher probability of eliciting each of the target movements. However, mutual overlap and variations of the zones are present not just between the subjects, but also on the intrasubject level, reflected through these session to session transformations of the selected virtual electrodes. The obtained results could be used as a priori knowledge for semi-automated optimization algorithm and could shorten the time required for calibration of the multi-pad electrode.

Kinematic analysis of the drag flick in field hockey

Attaining high speed of the stick head and consequently of the ball is essential for successful performance of the drag flick in field hockey, but the coordination pattern used to maximise stick head speed is unknown. The kinematics of the drag flick was studied in ten elite hockey players who performed twenty shots each towards a target located 1.5 m high. A 150 Hz active marker motion analysis system was used, alongside two force plates to detect foot touchdown. Angular velocity and contribution to stick endpoint speed of upper body joints were analysed. Repeated measures ANOVA was used to compare timing of onset and peak angular velocities between joints. Participants used a kinematic pattern that was close to a proximal-to-distal sequence. Trunk axial rotation and lateral rotation towards the target, right wrist flexion and left wrist extension were the main contributors to stick endpoint speed. Coaches should emphasise trunk rotations and wrist flexion and extension movements for maximising stick head speed. Given the high level of the participants in this study, the coordination of joints motions, as reported here, can serve as a guideline for drag flick training.

Effects of Increasing Neuromuscular Electrical Stimulation Current Intensity on Cortical Sensorimotor Network Activation: A Time Domain fNIRS Study.

Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements activate regions of the cortical sensorimotor network, including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), and secondary somatosensory area (S2), as well as regions of the prefrontal cortex (PFC) known to be involved in pain processing. The aim of this study, on nine healthy subjects, was to compare the cortical network activation profile and pain ratings during NMES of the right forearm wrist extensor muscles at increasing current intensities up to and slightly over the individual maximal tolerated intensity (MTI), and with reference to voluntary (VOL) wrist extension movements. By exploiting the capability of the multi-channel time domain functional near-infrared spectroscopy technique to relate depth information to the photon time-of-flight, the cortical and superficial oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations were estimated. The O2Hb and HHb maps obtained using the General Linear Model (NIRS-SPM) analysis method, showed that the VOL and NMES-evoked movements significantly increased activation (i.e., increase in O2Hb and corresponding decrease in HHb) in the cortical layer of the contralateral sensorimotor network (SMC, PMC/SMA, and S2). However, the level and area of contralateral sensorimotor network (including PFC) activation was significantly greater for NMES than VOL. Furthermore, there was greater bilateral sensorimotor network activation with the high NMES current intensities which corresponded with increased pain ratings. In conclusion, our findings suggest that greater bilateral sensorimotor network activation profile with high NMES current intensities could be in part attributable to increased attentional/pain processing and to increased bilateral sensorimotor integration in these cortical regions.

Electrophysiological manifestations of mirror visual feedback during manual movement

ObjectiveTo investigate the neurophysiological manifestations of the mechanism underlying the effects of Mirror Visual Feedback (MVF) during manual movement. MethodThirteen healthy right handed individuals were assessed while performing repeated unilateral wrist extension movements with and without MVF. The effect of MVF on EEG oscillations was studied in 3 distinct frequency ranges (low mu, high mu, low beta). ResultsAnalysis of the low beta range showed that MVF reduces the magnitude of event-related de-synchronization (ERD) in the hemisphere contra-lateral to the moving hand. This effect reached significance when the moving hand was the dominant hand. In the analysis of the low mu range, bi-hemispheric amplification of ERD by the mirror pointed to an added effect of neural recruitment. This effect reached significance when the moving hand was the non-dominant hand. ConclusionsMVF applied during unilateral manual movement (a) attenuates hemispheric activation asymmetry, and (b) is likely to involve recruitment of the mirror neuron system. SignificanceAs each of the above two effects reached significance only in one hand (dominant and non-dominant, respectively), clinical application of MVF might show a different level of efficacy in the treatment of right and left hemiparesis.