Neurosci Lett. 2015 Oct 8;606:173-6.
Nap it or leave it in the elderly: A nap after practice relaxes age-related limitations in procedural memory consolidation
1Korman M., Ph.D, 2Dagan Y., Ph.D, MD, 2Karni A.,Ph.D, MD
1Dept. of Occupational Therapy, Faculty of Social Welfare & Health Sciences, University of Haifa, Haifa, Israel
2Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Israel
Using a training protocol that effectively induces procedural memory consolidation (PMC) in young adults, we show that older adults are good learners, robustly improving their motor performance during training. However, performance declined over the day, and overnight ‘offline’ consolidation phase performance gains were under-expressed. A post-training nap countered these deficits. PMC processes are preserved but under-engaged in the elderly; sleep can relax some of the age-related constraints on long-term plasticity.
Previous research has suggested that older adults don’t remember newly acquired motor skills as well as young adults do. Apparent deficits observed after training in older individuals may reflect sub-optimal engagement of procedural, ‘how to’ memory consolidation processes rather than a core deficit in procedural memory consolidation abilities per se. In young adults motor skill consolidation benefits from both night-time and day-time sleep [1,2]. One possible constraint that may be at work in older adults is an increased susceptibility to interference experiences during the waking hours after the training session, e.g., by everyday activities following training session for which the newly learned task is irrelevant. We hypothesized that by shortening the interval between learning and consolidation, the nap prevents intervening experiences from weakening the memory before it solidifies. Using a training protocol that engages complex sequence of finger and thumb movements on the non-dominant hand, we trained healthy elderly participants during morning hours. Half of them were afforded a 90 min nap after the training. All participants slept well during the post-training night. Memory for the trained task was assessed before and after the night sleep. Our findings showed that unless a post-training nap was afforded, performance tended to decline during the ensuing hours of waking, and overnight, consolidation phase (“offline”) gains are under-expressed. Post-training sleep compensated some of the age-dependent constraints on procedural memory consolidation, perhaps by limiting the time-window for unspecific interference experiences before sleep period and by increasing the overall sleep time during the day.
Our results suggest that motor skill acquisition is preserved in healthy elderly individuals, but procedural memory consolidation processes are under-engaged in conditions that suffice to trigger effective consolidation in younger adults. We conjecture that as we age, our neural system becomes more selective on what to retain in the long-term memory. Our results have a translational perspective for the development of new and potentially more effective teaching and learning strategies for older adults.
- Korman M, Doyon J, Doljansky J, Carrier J, Dagan Y, et al. (2007) Daytime sleep condenses the time course of motor memory consolidation. Nat Neurosci 10: 1206-1213.
- Korman M, Raz N, Flash T, Karni A (2003) Multiple shifts in the representation of a motor sequence during the acquisition of skilled performance. Proc Natl Acad Sci U S A 100: 12492-12497.