Motor practice in a force modulation task in young and middle-aged adults.

Learning new motor skills is important for everyday life and independent living in older age. While studies on motor sequence learning and motor adaptation revealed age differences that are mostly related to frontal decline with increasing age, data for fine finger force modulation are missing. Twelve young (YA, 18-28 years) and twelve middle-aged older (OA, 55-65 years) adults practiced a force modulation task in precision grip while lying in a 3T MR scanner. Participants followed a sine wave between 5 and 25% of their maximum voluntary contraction (MVC) at a frequency of 0.3 Hz. Ten trials of 30 s were performed to examine learning curves and related changes in Blood Oxygen Level Dependent (BOLD) responses were assessed with functional magnetic resonance imaging (fMRI). Training slopes were similar for YA and OA, with only a trend for differences in performance level. Both age groups revealed decreasing activations with practice in frontal and parietal regions as well as in the cerebellum. Particularly, the hippocampus was activated in initial trials, but activity immediately decreased with practice. Increase in activation during practice was found only for YA in occipital cortex, cingulate cortex, and thalamus. After practice, OA revealed a pattern similar to the one that YA showed before practice. Described differences between YA and OA in neural activation related to motor practice may indicate compensational mechanisms in OA to enable similar learning slopes as in YA.