White matter neuroplasticity and motor learning

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The human brain is remarkably neuroplastic, yet most studies have focused nearly exclusively on neuroplasticity in the cortical gray matter. Until recently we thought that white matter structures in the brain had little potential for experience-dependent neuroplastic change. Recent work from rodent models suggests that this is incorrect; however, this question has not been considered in humans. The main hypothesis being tested in the proposed work is that white matter, specifically myelin, is neuroplastic and supports experience dependent change associated with motor learning in the human brain. White matter makes up 40% of brain tissue. Myelin is a critical structural component in the brain that allows rapid and effective information exchange, yet we know very little about how it supports motor learning. Recent advances in human neuroimaging have enabled the quantification of myelin in vivo in the human brain. Multi-component T2 relaxation imaging (MCRI) is a MRI based imaging approach that allows quantification of the thickness of myelin by mapping water in the lipid bilayers. Critically, MCRI has been histopathologically validated as a measure of myelin content in human brain. Recent work from my lab using MCRI showed that myelin thickness increases to support motor learning in young healthy people. Specifically, we discovered a relationship between increased myelin thickness in the intraparietal sulcus and the rate of skill acquisition associated with practice of a motor learning task (Lakhani et al, 2016). Given that ours was the first study to show a relationship between myelin plasticity and motor skill learning in humans numerous questions remain. These form the basis of the current proposal where we will investigate the relationships between myelin plasticity and: motor behaviour, skilled practice and grey matter plasticity. If as proposed here white matter, specifically myelin, is highly neuroplastic and responsive to varied behavioural manipulations in humans then theories of neuroplasticity will change. This fundamental knowledge will significantly advance the fields of neuroscience and motor learning, continuing the rapid expansion of knowledge of the dynamic nature of the brain. Taken together the data from this proposal will provide important new insights to our understanding of how structural neuroplasticity affects learning.