The objective of this study was to examine age differences in procedural learning and performance in conjunction with differential aging of central nervous system (CNS) structures. Sixty-eight healthy volunteers (age 22-80) performed a pursuit rotor task (four blocks of 20 15-second trials each). Volumes of the cerebellar hemispheres, neostriatum, prefrontal cortex, and hippocampus were measured from Magnetic Resonance (MR) images. Improvement in pursuit rotor performance was indexed by increase in time on target (TOT). A general improvement trend was evident across the blocks of trials. Overall, younger participants showed significantly longer TOT. The rate of improvement was age-invariant during the initial stages of skill acquisition but became greater in middle-aged participants as the practice progressed. When the influences of regional brain volumes were taken into account, the direct age effect on mean TOT measured during the first day of practice disappeared. Instead, reduced volumes of the cerebellar hemispheres and the putamen and poorer performance on nonverbal working memory tasks predicted shorter TOT. In contrast, neither the volume of the caudate and the hippocampus, nor verbal working memory showed association with motor performance. Pursuit rotor performance at the later stages of practice was unrelated to the reduction in putamen volume and was affected directly by age, cerebellar volume, and nonverbal working memory proficiency. We conclude that in a healthy population showing no clinical signs of extrapyramidal disease, age-related declines in procedural learning are associated with reduced volume of the cerebellar hemispheres and lower nonverbal working memory scores. During initial stages of skill acquisition, reduced volume of the putamen is also predictive of poorer performance.
Copyright 2000 Wiley-Liss, Inc.