Kraeutner, S. N. | Search bioRxiv

bioRxiv2022

Experience-dependent learning and myelin plasticity in individuals with stroke

BackgroundInjury to brain myelin disrupts motor performance and learning, however it is not clear if myelination is modulated by skilled motor practice or by recovery after stroke. Multi-component relaxation imaging can be used to measure water trapped between myelin bilayers which is expressed as myelin water fraction. The purpose of this study was to examine the effect of experience-dependent learning on myelin plasticity using multi-component relaxation imaging in individuals with stroke. MethodsThirty-two individuals with chronic stroke (>6 months) and twenty-seven healthy controls completed 4 weeks of skilled motor practice using a complex, gamified reaching task. Multi-component relaxation imaging-derived myelin water fraction was obtained before and after training. Seven brain regions associated with motor learning and sensorimotor function were investigated. ResultsAll participants improved task-specific reaching movements after training. In individuals with stroke: 1) pre-training myelin water fraction was lower in motor brain regions but higher in the cingulum compared to controls, 2) pre-training myelin water fraction in motor and sensorimotor regions was positively associated with learning rate, and 3) myelin water fraction was increased in the ipsilesional (contralateral to the trained arm) superior longitudinal fasciculus following skilled motor practice. ConclusionsFindings indicate that after stroke, myelin water fraction is related to measures of motor learning and modulated by 4 weeks of skilled motor practice with the paretic limb. Myelin water fraction can be enhanced in the chronic stage of stroke and may be an important target for upper-limb motor recovery.

neuroscience↗

bioRxiv2021

Multiple bouts of high-intensity interval exercise reverse age-related functional connectivity disruptions without affecting motor learning in older adults

Exercise has emerged as an intervention that may mitigate age-related resting state functional connectivity and sensorimotor declines. Here, 42 healthy older adults rested or completed 3 sets of high-intensity interval exercise for a total of 23 minutes, then immediately practiced an implicit motor task with their non-dominant hand across five separate sessions. Participants completed resting stage functional MRI before the first and after the fifth day of practice; they also returned 24-hours and 35-days later to complete short- and long-term retention. Independent component analysis of resting state functional MRI revealed increased connectivity in the frontoparietal, the dorsal attentional, and cerebellar networks and group. seed-based analysis showed strengthened connectivity between the limbic system and right cerebellum, and between the right cerebellum and bilateral middle temporal gyri in the exercise group. There was no motor learning advantage for the exercise group. Our data suggest that exercise paired with an implicit motor learning task in older adults can augment resting state functional connectivity without enhancing behaviour beyond that stimulated by skilled motor practice. Impact statementFive separate bouts of exercise paired with skilled motor practice strengthens resting state networks in brain regions that are susceptible to declines in older adults without affecting motor acquisition or learning.

neuroscience↗