Age differences in symbolic representations of motor sequence learning.

We recently reported that young adults (YA) preferentially recruit cerebellar lobule HVI for symbolic motor sequence learning [3]. Learning magnitude in the symbolic condition was correlated with activation level in lobule HVI. Here, we evaluated age differences in the symbolic representation of motor sequence learning. Fourteen YA and 14 older adults (OA) performed the alternating serial reaction time task (ASRT) under conditions in which the spatial processing component was selectively eliminated from stimulus presentation (spatial versus symbolic), response execution (manual versus vocal), or both. Results showed that OA had reduced learning magnitudes relative to YA. Using the cerebellum lobule HVI as a region-of-interest, we found that OA had significantly lower activation in this region than YA during the symbolic learning conditions (FWE, P<0.05). Similar to YA, OA also showed a significant correlation between learning magnitude and cerebellar activation in the symbolic conditions. These results suggest that although YA and OA recruit similar neural networks during implicit learning, OA under-recruit relevant brain areas which may partially explain their implicit sequence learning deficits.