Abstract
White matter (WM) plasticity during adulthood is a recently described phenomenon by which experience can shape brain structure. It has been observed in humans using diffusion tensor imaging (DTI) and myelination has been suggested as a possible mechanism. Here, we set out to identify molecular and cellular changes associated with WM plasticity measured by DTI. We combined DTI, immunohistochemistry and mRNA expression analysis and examined the effects of somatosensory experience in adult rats. First, we observed experience-induced DTI differences in WM and in grey matter structure. C-Fos mRNA expression, a marker of cortical activity, in the barrel cortex correlated with the MRI WM metrics, indicating that molecular correlates of cortical activity relate to macroscale measures of WM structure. Analysis of myelin-related genes revealed higher myelin basic protein (MBP) mRNA expression. Higher MBP protein expression was also found via immunohistochemistry in WM. Finally, unbiased RNA sequencing analysis identified 134 differentially expressed genes encoding proteins involved in functions related to cell proliferation and differentiation, regulation of myelination and neuronal activity modulation. In conclusion, macroscale measures of WM plasticity are supported by both molecular and cellular evidence and confirm that myelination is one of the underlying mechanisms.
Highlights
STATEMENT White matter plasticity is a recently described mechanism by which experience shapes brain structure and function during adulthood
To assess effects of experience on White matter (WM) microstructure we jointly analyzed structural measures calculated from post-mortem diffusion tensor imaging (DTI) scans of left hemispheres from texture detection task (TDT) (n=28) and passive control (PC, n=20) animals
We have demonstrated that somatosensory experience results in structural white matter plasticity and identify some molecular correlates that provide candidate mechanisms underlying these findings, such as myelin formation and/or remodelling
Summary
STATEMENT White matter plasticity is a recently described mechanism by which experience shapes brain structure and function during adulthood. We report structural changes in white matter detected with DTI after novel somatosensory experience in rats We further support these findings with mRNA evidence of differentially expressed genes involved in functions compatible with regulation of cell proliferation, myelin thickness and neuronal modulation. These putative molecular mechanisms offer insights about the underlying DTI correlates of experience-dependent WM plasticity and provide further evidence for myelin plasticity in adulthoo
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