Motor Learning and Physical Exercise in Adaptive Myelination and Remyelination

Abstract

The idea that myelination is driven by both intrinsic and extrinsic cues has gained much traction in recent years. Studies have demonstrated that myelination occurs in an intrinsic manner during early development and continues through adulthood in an activity-dependent manner called adaptive myelination. Motor learning, the gradual acquisition of a specific novel motor skill, promotes adaptive myelination in both the healthy and demyelinated central nervous system (CNS). On the other hand, exercise, a physical activity that involves planned, structured and repetitive bodily movements that expend energy and benefits one's fitness, promotes remyelination in pathology, but it is less clear whether it promotes adaptive myelination in healthy subjects. Studies on these topics have also investigated whether the timing of motor learning or physical exercise is important for successful addition of myelin. Here we review our current understanding of the relationship of motor skill learning and physical exercise on myelination.

Overview of myelin, major myelin lipids, and myelin-associated proteins

“…This perspective allows one to appreciate the system’s plasticity–how functional and structural changes occur in response to changes in the living organism. An example of how this shift in focus yields new insights into myelin biology is the newly described concept of ‘adaptive myelination’ ( Bechler et al, 2018 ; Bloom et al, 2022 ). It is clear that the investigation will not end at this stage of cellular plasticity but will proceed to the next level of organizational complexity: the neuroplasticity of the organ level–that of the brain and nervous tissue.…”

Aerobic Exercise Improves Cortical Inhibitory Function After Stroke: A Preliminary Investigation

“…Given the absence of group-level changes in cortical N2 responses (Figures 2C and D), it is possible that other neural signals interfering with the role of cortical inhibition in mediating cognitive control were dampened with aerobic exercise training, for example, by improvements in neural dedifferentiation across multiple cortical regions observed in aging populations 61. Higher levels of physical activity have been linked to greater myelination within the poststroke brain62 and can occur on timescales of 2 to 6 weeks (for review, see the study by Bloom et al63), consistent with the temporal cortical N2 component (ie, N2 latency) association with behavior following exercise training in the present study (Figure 3C). Future studies employing multimodal neuroimaging approaches (eg, functional magnetic resonance imaging used synergistically with EEG) could provide spatial insight into the neural substrates underpinning behaviorally salient markers of cortical inhibition and may inform the development of targeted synergistic treatment approaches (eg, noninvasive brain stimulation)64 with aerobic exercise training.…”

Physical activity and the brain myelin content in humans

“…Animal studies provide a quite complex scheme with regard to myelination and remyelination. There are two terms that have been coined to describe the underlying mechanisms behind myelination physiology and pathophysiology: adaptive myelination and remyelination ( Bloom et al, 2022 ). Adaptive myelination refers to the expansion of already existing myelin sheaths or the addition of supplementary myelin to myelinated brain regions.…”

“…Adaptive myelination refers to the expansion of already existing myelin sheaths or the addition of supplementary myelin to myelinated brain regions. Remyelination is understood as the covering of demyelinated axons with a new myelin ( Bloom et al, 2022 ). Adaptive myelination is triggered by novel learning experiences—for example, when an animal acquires a novel motor task ( McKenzie et al, 2014 ; Zhou et al, 2016 ).…”

“…Adaptive myelination is triggered by novel learning experiences—for example, when an animal acquires a novel motor task ( McKenzie et al, 2014 ; Zhou et al, 2016 ). It is believed that the first 24 h following exposure to novel motor tasks are critical and actually define the opportunity window for adaptive myelination ( Bloom et al, 2022 ). It remains unclear if, in animals, voluntary exercise not associated with novel learning may result in adaptive myelination.…”