RESPONSE (RE-)PROGRAMMING IN AGING - A KINEMATIC ANALYSIS

Background. Age-related motor slowing may reflect either motor program ming deficits, poorer movement execution, or mere strategic preference s for online guidance of movement. We controlled such preferences, lim iting the extent to which movements could be programmed. Methods. Twen ty-four young and 24 older adults performed a line drawing task that a llowed movements to he prepared in advance in one case (i.e., cue init ially available indicating target location) and not in another (i.e., no cue initially available as to target location). Participants connec ted large or small targets illuminated by light-emitting diodes upon a graphics tablet that sampled pen tip position at 200 Hz. Results. Old er adults had a disproportionate difficulty initiating movement when p revented from programming in advance. Older adults produced slower, le ss efficient movements, particularly when prevented from programming u nder greater precision requirements. Conclusions. The slower movements of older adults do not simply reflect a preference for online control , as older adults have less efficient movements when forced to reprogr am their movements. Age-related motor slowing kinematically resembles that seen in patients with cerebellar dysfunction.