Sleep modulates word-pair learning but not motor sequence learning in healthy older adults

Sleep benefits memory across a range of tasks for young adults. However, remarkably little is known of the role of sleep on memory for healthy older adults. We used 2 tasks, 1 assaying motor skill learning and the other assaying nonmotor/declarative learning, to examine off-line changes in performance in young (20-34 years), middle-aged (35-50 years), and older (51-70 years) adults without disordered sleep. During an initial session, conducted either in the morning or evening, participants learned a motor sequence and a list of word pairs. Memory tests were given twice, 12 and 24 hours after training, allowing us to analyze off-line consolidation after a break that included sleep or normal wake. Sleep-dependent performance changes were reduced in older adults on the motor sequence learning task. In contrast, sleep-dependent performance changes were similar for all 3 age groups on the word pair learning task. Age-related changes in sleep or networks activated during encoding or during sleep may contribute to age-related declines in motor sequence consolidation. Interestingly, these changes do not affect declarative memory.