A surprising and highly novel finding was the diverse impact of these structural changes on the different types of OLGs in response to motor PD–a mild demyelinating phenotype in motor tract WM with evidence of OLG replenishment by activated precursors that correlate with αSyn accumulation in axon segments, and a hypermyelinating phenotype in the overlying motor cortex in response to increased cortical NFL. This evidence concerns the gene NEFL and Parkinson disease.