AGE-RELATED DIFFERENCES IN WHITE MATTER MICROSTRUCTURE ARE STABLE ACROSS 3 WEEKS OF BIMANUAL MOTOR TRAINING

Age-related structural changes in cortical myelin (CM) and white matter microstructure have been widely reported, yet whether these differences influence training-induced plasticity and skill improvement remains incompletely understood. In particular, it is unclear if the potential for training-induced plasticity in task-relevant motor areas is reduced in older adults. The present study investigated age-related differences in CM, and whether white matter microstructural integrity is modulated in an age-dependent manner by three weeks of bimanual skill training. Additionally, we explored whether individual motor improvements can be associated with white matter structural properties. Structural MRI data were acquired in 27 healthy younger (aged 22–27) and 27 healthy older adults (aged 65–70) at baseline and after 3 weeks of bimanual pinch force training in a visually guided motor task. CM-sensitive measures were derived from MP2RAGE-derived T1 maps, and white matter microstructure (FA, MD) was assessed from diffusion-weighted imaging. Significant baseline differences in callosal tracts connecting M1-M1 and SMA-SMA were observed, with younger adults showing higher FA and lower MD compared to older adults, but no significant changes in CM were detected following three weeks of bimanual motor training. These findings demonstrate robust age-related differences in interhemispheric white matter microstructure, while suggesting relative structural stability of primary motor cortical regions across age and limited sensitivity of cortical structure to three weeks of bimanual motor training. Ongoing analyses will clarify whether baseline structural properties are associated with individual motor performance.