The influence of sleep/wake states on procedural memory consolidation in older adults depends on performance level during initial learning: A neuroimaging investigation

Although sleep facilitates procedural memory consolidation in young adults, such beneficial effects are diminished with aging. Although the source of this impairment is likely multifaceted, the lack of sleep-related consolidation in older adults may be at least partially attributed to the lower performance levels obtained by older adults during initial encoding. Indeed, research in both children and young adults has indicated that sleep / wake states and online performance on a motor sequence learning (MSL) task interact to influence offline memory consolidation. We thus employed a functional MRI protocol to investigate whether performance levels obtained by older adults (mean age = 62 yrs) during an initial MSL session differentially influenced subsequent memory consolidation across sleep and wake retention intervals. Following completion of an initial MSL session at 11am in the scanner, participants were either afforded a 90-minute nap opportunity (n=28) or were asked to remain awake (n=28). Participants returned to the scanner to complete a MSL retest 5-8 hours after initial training. Results demonstrated no differences in consolidation after a nap or wake interval if participants reached relatively lower levels of performance during initial learning. However, in those who obtained higher performance levels during training, a nap significantly minimized the performance deterioration that was evident across a wake interval. In these higher performing individuals, increased activation in the striatum, cerebellum and parietal cortex during initial learning was beneficial for subsequent offline consolidation if participants were afforded a nap after training but was detrimental in those who remained awake. Collectively, our results indicate that sleep / wake states influence offline motor memory consolidation in older adults only if sufficient performance levels are reached during training and this effect appears to be mediated by recruitment of a striato-cerebello-cortical network during the initial learning phase.status: publishe