Patients with capsular infarct and Wallerian degeneration show persistent regional premotor cortex activation on functional magnetic resonance imaging

Brain-Computer Interface Training after Stroke Affects Patterns of Brain-Behavior Relationships in Corticospinal Motor Fibers

Background: Brain–computer interface (BCI) devices are being investigated for their application in stroke rehabilitation, but little is known about how structural changes in the motor system relate to behavioral measures with the use of these systems.

Objective: This study examined relationships among diffusion tensor imaging (DTI)-derived metrics and with behavioral changes in stroke patients with and without BCI training.

Methods: Stroke patients (n = 19) with upper extremity motor impairment were assessed using Stroke Impact Scale (SIS), Action Research Arm Test (ARAT), Nine-Hole Peg Test (9-HPT), and DTI scans. Ten subjects completed four assessments over a control period during which no training was administered. Seventeen subjects, including eight who completed the control period, completed four assessments over an experimental period during which subjects received interventional BCI training. Fractional anisotropy (FA) values were extracted from each corticospinal tract (CST) and transcallosal motor fibers for each scan.

Results: No significant group by time interactions were identified at the group level in DTI or behavioral measures. During the control period, increases in contralesional CST FA and in asymmetric FA (aFA) correlated with poorer scores on SIS and 9-HPT. During the experimental period (with BCI training), increases in contralesional CST FA were correlated with improvements in 9-HPT while increases in aFA correlated with improvements in ARAT but with worsening 9-HPT performance; changes in transcallosal motor fibers positively correlated with those in the contralesional CST. All correlations p < 0.05 corrected.

Conclusion: These findings suggest that the integrity of the contralesional CST may be used to track individual behavioral changes observed with BCI training after stroke.

Models to Tailor Brain Stimulation Therapies in Stroke

A great challenge facing stroke rehabilitation is the lack of information on how to derive targeted therapies. As such, techniques once considered promising, such as brain stimulation, have demonstrated mixed efficacy across heterogeneous samples in clinical studies. Here, we explain reasons, citing its one-type-suits-all approach as the primary cause of variable efficacy. We present evidence supporting the role of alternate substrates, which can be targeted instead in patients with greater damage and deficit. Building on this groundwork, this review will also discuss different frameworks on how to tailor brain stimulation therapies. To the best of our knowledge, our report is the first instance that enumerates and compares across theoretical models from upper limb recovery and conditions like aphasia and depression. Here, we explain how different models capture heterogeneity across patients and how they can be used to predict which patients would best respond to what treatments to develop targeted, individualized brain stimulation therapies. Our intent is to weigh pros and cons of testing each type of model so brain stimulation is successfully tailored to maximize upper limb recovery in stroke.

Reorganization of brain function during force production after stroke: a systematic review of the literature

BACKGROUND AND PURPOSE

Damage to motor areas of the brain caused by stroke can produce devastating motor deficits, including aberrant control of force. Reorganization of brain function is a fundamental mechanism involved in recovery of motor control after stroke, and recent advances in neuroimaging have enabled study of this reorganization. This review focuses on neuroimaging studies that have examined reorganization of brain function during force production and force modulation after stroke.

METHODS

The type and extent of reorganization after stroke were characterized by three factors: severity of injury, time after stroke, and impact of therapeutic interventions on brain activation during force production. Twenty-six studies meeting the inclusion criteria could be identified in MEDLINE (1980-2007).

RESULTS

Relevant characteristics of studies (lesion location, chronicity of stroke, and motor task) and mapping techniques varied. During force production, increased activation in secondary motor areas occurred in persons with more severe strokes. Reduced recruitment of secondary motor areas during force production was found as a function of increased time since stroke. During force modulation, increased activation in motor areas occurred with greater force generation. Persons with more severe stroke showed greater activation with increasing force compared with persons with less severe stroke. Alteration of brain activation during and after rehabilitative interventions was identified in some studies.

DISCUSSION AND CONCLUSION

This systematic review establishes that reorganization of brain function during force production and force modulation can occur after stroke. These findings imply that therapeutic strategies may target brain reorganization to improve force control and functional recovery after stroke.

A working model of stroke recovery from rehabilitation robotics practitioners

We reviewed some of our initial insights about the process of upper-limb behavioral recovery following stroke. Evidence to date indicates that intensity, task specificity, active engagement, and focusing training on motor coordination are key factors enabling efficacious recovery. On modeling, experience with over 400 stroke patients has suggested a working model of recovery similar to implicit motor learning. Ultimately, we plan to apply these insights in the development of customized training paradigms to enhance recovery.

Longitudinal Optical Imaging Study for Locomotor Recovery After Stroke

Background and Purpose— We sought to investigate cerebral mechanisms underlying locomotor recovery after stroke.

Methods— We measured cortical activities during hemiparetic gait on the treadmill before and after 2 months of inpatient rehabilitation in 8 patients with initial stroke (5 men, 3 women; 4 with right and 4 with left hemiparesis; aged 57 years; 3 months after stroke on average), using an optical imaging system.

Results— On the initial evaluation, hemiparetic gait was associated with increased oxygenated hemoglobin levels in the medial primary sensorimotor cortex (SMC) that were greater in the unaffected hemisphere than in the affected hemisphere as well as in the premotor cortex (PMC) and supplementary motor area. On the second examination, the asymmetry in SMC activation significantly improved, and there was enhanced PMC activation in the affected hemisphere. Improvement of the asymmetrical SMC activation significantly correlated with improvement of gait parameters.

Conclusions— Locomotor recovery after stroke may be associated with improvement of asymmetry in SMC activation and enhanced PMC activation in the affected hemisphere.

Robotics in the rehabilitation treatment of patients with stroke

Stroke is the leading cause of permanent disability despite continued advances in prevention and novel interventional treatments. Post-stroke neuro-rehabilitation programs teach compensatory strategies that alter the degree of permanent disability. Robotic devices are new tools for therapists to deliver enhanced sensorimotor training and concentrate on impairment reduction. Results from several groups have registered success in reducing impairment and increasing motor power with task-specific exercise delivered by the robotic devices. Enhancing the rehabilitation experience with task-specific repetitive exercise marks a different approach to the patient with stroke. The clinical challenge will be to streamline, adapt, and expand the robot protocols to accommodate healthcare economies, to determine which patients sustain the greatest benefit, and to explore the relationship between impairment reduction and disability level. With these new tools, therapists will measure aspects of outcome objectively and contribute to the emerging scientific basis of neuro-rehabilitation.