Neurophysiological mechanisms underlying motor skill learning in young and older adults.

The ability to acquire and retain novel motor skills is preserved with advancing age. However, the neurophysiological mechanisms underlying skill acquisition in older adults have received little systematic investigation. The aim of the present study was to assess the modulation of primary motor cortex excitability and inhibition after skill acquisition in young and older adults. Sixteen young and sixteen older adults trained on a sequential visual isometric wrist extension task. Anodal or sham transcranial direct current stimulation was applied during training in a pseudorandomized crossover design. Skill was quantified before, immediately after, 24 h and 7 days post-training. Transcranial magnetic stimulation protocols were used to examine corticomotor excitability and intracortical inhibition pre- and post-training. Corticomotor excitability increased and intracortical inhibition decreased after skill acquisition in both age groups. Anodal transcranial direct current stimulation did not enhance skill acquisition or the modulation of neurophysiological variables. These findings indicate potential neurophysiological mechanisms relevant for motor learning in neurorehabilitation contexts involving older adults, such as after stroke.