Differential effects of age on sequence learning and sensorimotor adaptation.

Although many studies have documented declines in the ability of the elderly to learn new manual motor skills, studies have not directly compared the capacity of older adults to learn sequences versus adapt to sensorimotor perturbations within the context of the same task paradigm, despite differences in the underlying neural mechanisms and strategic processes supporting the two types of learning. The purpose of the current study was to exploit these task differences in an effort to determine whether aging results in a generalized or more specific skill learning deficit. Groups of young and older adult subjects learned to make a sequence of actions, adapted to one of two visuomotor rotations, or adapted to an altered gain of display, all while performing the same basic manual joystick aiming task. While the older adults exhibited normal sequence learning in comparison to the young adults, they exhibited impairments in all three of the adaptation tasks. These deficits in adaptation for the older adults were associated with hypometric movements and reduced velocity modulation in comparison to that seen in the younger adults. These data suggest that older adults may have greater difficulty with learning cerebellar-mediated motor skills.