Crystal L. Massie

Does Provision of Extrinsic Feedback Result in Improved Motor Learning in the Upper Limb Poststroke? A Systematic Review of the Evidence

Background. Recovery of the upper limb (UL) after a stroke occurs well into the chronic stage. Stroke survivors can benefit from adaptive plasticity to improve UL movement through motor relearning. The provision of feedback has been shown to decrease the use of compensatory UL movement patterns. However, the effectiveness of feedback in improving UL motor recovery after a stroke has not yet been systematically reviewed. Objective.The objective of this review was to systematically examine the role of extrinsic feedback on implicit motor learning after stroke, focusing on UL movement and functional recovery. Results. The authors retrieved 9 studies that examined the role of feedback on UL motor recovery. Of these, 6 were randomized controlled trials (RCTs), 1 was a single-subject design, 1 was a pre—post design, and 1 was a cohort study. The studies were rated on the basis of Sackett’s levels of evidence and PEDro (Physiotherapy Evidence Database) scores for RCTs. Levels of evidence were limited (level 2b) for UL motor learning of the less-affected extremity and strong (level 1a) for the more-affected extremity. Discussion and conclusions. The results suggest that people with stroke may be capable of using extrinsic feedback for implicit motor learning and improving UL motor recovery. Emergent questions regarding the advantages of using different media for feedback delivery and the optimal type and schedule of feedback to enhance motor learning in patient populations still need to be addressed.

Rhythmic auditory-motor entrainment improves hemiparetic arm kinematics during reaching movements: a pilot study.

Abstract Purpose: Recovery of skilled upper limb movement remains a critical focus of rehabilitation in individuals post stroke. Conventional treatments, however, have demonstrated limited capability to produce substantial improvements in poststroke quality of movement. Recently, rhythmic auditory stimulation (RAS) has emerged as efficacious in improving and normalizing limb movements in neurologically impaired populations. This pilot study examined changes in pre- to post-RAS reach kinematics and functional outcomes in survivors of stroke. Method: Five individuals in the chronic poststroke phase participated in a 2-week program of RAS training. Kinematic reaching variables were trunk, shoulder, and elbow segment contribution; movement time; and reach velocity. Functional outcomes were the Wolf Motor Function Test, Motor Activity Log, and Fugl-Meyer Assessment. Results: Post-RAS assessment of reaching kinematics revealed a significant (p < .05) decrease in compensatory trunk movement, increase in shoulder flexion, and a slight increase in elbow extension. Movement time and velocity significantly improved post RAS. Significant gains were observed on all functional assessments. Conclusions: Post RAS, participants demonstrated substantial decreases in compensatory reaching movements. These changes in motor control strategy were paralleled by gains in functional abilities, suggesting that reduced reliance on compensatory movements may translate to improved performance of daily activities.

Functional repetitive transcranial magnetic stimulation increases motor cortex excitability in survivors of stroke.

OBJECTIVE To determine if repetitive transcranial magnetic stimulation (rTMS) applied to the motor cortex with simultaneous voluntary muscle activation, termed functional-rTMS, will promote greater neuronal excitability changes and neural plasticity than passive-rTMS in survivors of stroke. METHODS Eighteen stroke survivors were randomized into functional-rTMS (EMG-triggered rTMS) or passive-rTMS (rTMS only; control) conditions. Measures of short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), force steadiness (coefficient of variation, CV) at 10% of maximum voluntary contraction, and pinch task muscle activity were assessed before and after rTMS. Functional-rTMS required subjects to exceed a muscle activation threshold to trigger each rTMS train; the passive-rTMS group received rTMS while relaxed. RESULTS Significant interactions (time × condition) were observed in abductor pollicis brevis (APB) SICI, APB ICF, CV of force, and APB muscle activity. Functional-rTMS decreased APB SICI (p < 0.05) and increased ICF (p < 0.05) after stimulation, whereas passive-rTMS decreased APB muscle activity (p < 0.01) and decreased CV of force (p < 0.05). No changes were observed in FDI measures (EMG, ICF, SICI). CONCLUSION(S) Functional-rTMS increased motor cortex excitability, i.e., less SICI and more ICF for the APB muscle. Passive stimulation significantly reduced APB muscle activity and improved steadiness. SIGNIFICANCE Functional-rTMS promoted greater excitability changes and selectively modulated agonist muscle activity.

Repetitive transcranial magnetic stimulation interrupts phase synchronization during rhythmic motor entrainment

Rhythmic stimuli delivered through the auditory system can facilitate improved motor control following a motor impairment. The synchronization of movement to rhythmic auditory cues is characterized by quick, stable coupling of motor responses to rhythmic auditory cues. The exact neural sites responsible for this transformation of auditory input into timed rhythmic motor output are not clear. Neuroimaging studies have identified left ventral premotor cortex (vPMC) and left superior temporal-parietal (STP) activation during rhythmic auditory-motor synchronization. To investigate brain areas necessary for different types of rhythmic auditory-motor synchronization, we delivered repetitive transcranial magnetic stimulation (rTMS) to 15 healthy individuals prior to a rhythmic-auditory tapping task. Subthreshold rTMS was administered separately to the left vPMC and STP at a frequency of 0.9Hz for 15 min. Phase synchronization error (difference between auditory stimulus and response onsets) significantly increased after rTMS to STP as compared to baseline. Synchronization error also increased after rTMS to vPMC as compared to baseline, but not significantly. Absolute period error, (absolute difference between metronome interval and response interval) was not affected by rTMS. The significant effect of rTMS at the STP expands upon previous imaging research, suggesting that this area is part of the network responsible for rhythmic auditory-motor synchronization. The effect of rTMS on phase synchronization, but not period synchronization suggests these are separate neural processes controlled by different neural networks.

Elbow Extension Predicts Motor Impairment and Performance after Stroke

Background and Purpose. Kinematic motion analysis has helped to characterize poststroke reaching strategies with the hemiparetic arm. However, the relationships between reaching strategy and performance on common functional outcome measures remain unclear. Methods. Thirty-five participants were tested for motor performance and motor impairment using the Wolf Motor Function Test (time and functional ability measure) and Fugl-Meyer assessment, respectively. Kinematic motion analysis of a forward reaching paradigm provided potential predictors of reaching strategy including shoulder flexion, elbow extension, and trunk displacement. A stepwise linear regression model with three potential predictors was used in addition to Pearson-product moment correlations. Results. Kinematic analysis of elbow extension predicted performance on both the Wolf Motor Function Test and Fugl-Meyer assessment. Shoulder flexion and trunk displacement did not significantly predict functional or reaching time outcomes. The Wolf Motor Function Test and the Fugl-Meyer assessment were highly correlated. Conclusions. The ability to incorporate elbow extension during reach is a significant predictor of motor performance and hemiparetic arm motor capacity after stroke.

Timing of motor cortical stimulation during planar robotic training differentially impacts neuroplasticity in older adults

OBJECTIVE The objective was to determine how stimulation timing applied during reaching influenced neuroplasticity related to practice. Older adult participants were studied to increase relevance for stroke rehabilitation and aging. METHODS Sixteen participants completed 3 sessions of a reaching intervention with 480 planar robotic movement trials. Sub-threshold, single-pulse transcranial magnetic stimulations (TMS) were delivered during the late reaction time (LRT) period, when muscle activity exceeded a threshold (EMG-triggered), or randomly. Assessments included motor evoked potentials (MEP), amplitude, and direction of supra-threshold TMS-evoked movements and were calculated as change scores from baseline. RESULTS The direction of TMS-evoked movements significantly changed after reaching practice (p<0.05), but was not significantly different between conditions. Movement amplitude changes were significantly different between conditions (p<0.05), with significant increases following the LRT and random conditions. MEP for elbow extensors and flexors, and the shoulder muscle that opposed the practice movement were significantly different between conditions with positive changes following LRT, negative changes following EMG-triggered, and no changes following the random condition. Motor performance including movement time and peak velocity significantly improved following the training but did not differ between conditions. CONCLUSIONS The responsiveness of the motor cortex to stimulation was affected positively by stimulation during the late motor response period and negatively during the early movement period, when stimulation was combined with robotic reach practice. SIGNIFICANCE The sensitivity of the activated motor cortex to additional stimulation is highly dynamic.

Kinematic Motion Analysis and Muscle Activation Patterns of Continuous Reaching in Survivors of Stroke

ABSTRACT Coordinated reaching requires continuous interaction between the efferent motor output and afferent feedback; this interaction may be significantly compromised following a stroke. The authors sought to characterize how survivors of stroke generate continuous, goal-directed reaching. Sixteen survivors of stroke completed functional testing of the stroke-affected side and a continuous reaching task between 2 targets with both sides. Motion analysis and electromyography data were collected to determine segmental contributions to reach (e.g., amount of compensatory trunk), spatiotemporal parameters (e.g., peak velocities), and muscle activation patterns (MAP). Repeated measures analyses of variance compared how survivors of stroke reach with the stroke-affected versus less affected sides. Correlations were determined between kinematic outcomes and functional ability. Participants used significantly more trunk movement and less shoulder flexion and elbow extension when reaching with the stroke-affected side. This corresponded with less muscle activity in the proximal musculature including the anterior, middle, and posterior deltoid on the stroke-affected side. There were significant correlations between the segmental contributions to reach, functional ability, and MAPs. Survivors of stroke generate reduced MAPs in the stroke-affected side corresponding to altered segmental kinematics and function ability. These findings suggest that impairments in the ability to generate sufficient MAPs may contribute to the difficulty in generating continuous reaching motions.

Instructions emphasizing speed improves hemiparetic arm kinematics during reaching in stroke.

BACKGROUND Stroke severely compromises the capacity for skilled motor control including the ability to reach with the stroke-affected upper-extremity. Research incorporating intensive motor therapies has broadly demonstrated the ability to improve hemiparetic reaching post-stroke, yet the role of specific task parameters has received less attention. These task parameters, such as speed-of-performance, may be important to the structure and delivery of motor rehabilitation. The objective of the study was to determine the influence of task pacing demands on hemiparetic reaching strategies in survivors of stroke. METHODS Kinematic motion analysis was used to examine upper-extremity reaching patterns in 11 survivors of stroke. Participants were instructed to reach between two targets at a self-selected pace and as fast as possible. Outcome measures included maximal movement speed, accuracy, movement smoothness, and reaching strategies (anterior trunk flexion, elbow extension, and shoulder flexion). RESULTS Participants reached significantly faster and smoother during the task that emphasized speed while maintaining target accuracy. Participants used significantly less anterior trunk displacement during the fast condition, yet no change in shoulder flexion. CONCLUSION Task parameters that emphasize speed positively influence reaching strategies with the more-affected upper-extremity. Survivors of stroke were able to respond to changes in pacing demands while significantly reducing reliance on compensatory trunk movement. This outcome highlights the need to further understand the impact of task parameters during intensive motor therapies.

Repeated sessions of functional repetitive transcranial magnetic stimulation increases motor cortex excitability and motor control in survivors of stroke.

OBJECTIVE To determine the impact of a single-session of repetitive transcranial magnetic stimulation (rTMS) and an rTMS intervention on neurophysiology and motor control in survivors of stroke. METHODS Twelve stroke survivors were randomized into functional-rTMS or passive-rTMS conditions. Measures of short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), and force steadiness (coefficient of variation, CV) at 10 and 20% of maximum voluntary contraction were assessed at baseline and after a single-session of rTMS (post single-session), and again following an intervention of 8 rTMS sessions (2 sessions per day; post-intervention). Functional-rTMS required subjects to exceed a muscle activation threshold assessed by surface electromyography to trigger each rTMS train; the passive-rTMS group received rTMS while relaxed. RESULTS ICF scores significantly increased following the single-session of functional-rTMS compared to the decrease following passive-rTMS. The increase in APB SICI and ICF scores following the intervention was significantly greater for the functional-rTMS group compared to the decreases following passive-rTMS. The groups were significantly different in the CV of force (20%) following the single-session of rTMS, and in the 10 and 20% tasks following the intervention. The functional-rTMS group increased steadiness overtime, whereas the passive group demonstrated a return to baseline following the intervention session. No differences were observed in first dorsal interosseus (FDI) measures (SICI and ICF) between groups. CONCLUSIONS The functional-rTMS protocol enhanced cortical excitability following a single-session and after repeated sessions and improved steadiness, whereas the passive stimulation protocol tended to decrease excitation and no improvements in steadiness were observed.

A Clinically Relevant Method of Analyzing Continuous Change in Robotic Upper Extremity Chronic Stroke Rehabilitation.

Background. Robots designed for rehabilitation of the upper extremity after stroke facilitate high rates of repetition during practice of movements and record precise kinematic data, providing a method to investigate motor recovery profiles over time. Objective. To determine how motor recovery profiles during robotic interventions provide insight into improving clinical gains. Methods. A convenience sample (n = 22), from a larger randomized control trial, was taken of chronic stroke participants completing 12 sessions of arm therapy. One group received 60 minutes of robotic therapy (Robot only) and the other group received 45 minutes on the robot plus 15 minutes of translation-to-task practice (Robot + TTT). Movement time was assessed using the robot without powered assistance. Analyses (ANOVA, random coefficient modeling [RCM] with 2-term exponential function) were completed to investigate changes across the intervention, between sessions, and within a session. Results. Significant improvement (P < .05) in movement time across the intervention (pre vs post) was similar between the groups but there were group differences for changes between and within sessions (P < .05). The 2-term exponential function revealed a fast and slow component of learning that described performance across consecutive blocks. The RCM identified individuals who were above or below the marginal model. Conclusions. The expanded analyses indicated that changes across time can occur in different ways but achieve similar goals and may be influenced by individual factors such as initial movement time. These findings will guide decisions regarding treatment planning based on rates of motor relearning during upper extremity stroke robotic interventions.