Memory improvement via slow-oscillatory stimulation during sleep in older adults

• Published in: Neurobiology of aging Vol. 36; no. 9; pp. 2577 - 2586
• Main Authors: Westerberg, Carmen E., Florczak, Susan M., Weintraub, Sandra, Mesulam, M. -Marsel, Marshall, Lisa, Zee, Phyllis C., Paller, Ken A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2015
• Subjects: Aged; Aged, 80 and over; Aging; Analysis of Variance; Association Learning; Biophysics; Cross-Over Studies; Declarative memory; Double-Blind Method; Electrical stimulation; Electroencephalography; Face; Female; Humans; Internal Medicine; Male; Memory Disorders - therapy; Neurology; Neuropsychological Tests; Polysomnography; Recognition, Psychology; Sleep - physiology; Slow-wave sleep; Transcranial Direct Current Stimulation; Aging; Electrical stimulation; Slow-wave sleep; Declarative memory
• ISSN: 0197-4580; 1558-1497; 1558-1497
• DOI: 10.1016/j.neurobiolaging.2015.05.014

We examined the intriguing but controversial idea that disrupted sleep-dependent consolidation contributes to age-related memory decline. Slow-wave activity during sleep may help strengthen neural connections and provide memories with long-term stability, in which case decreased slow-wave activity in older adults could contribute to their weaker memories. One prediction from this account is that age-related memory deficits should be reduced by artificially enhancing slow-wave activity. In young adults, applying transcranial current oscillating at a slow frequency (0.75 Hz) during sleep improves memory. Here, we tested whether this procedure can improve memory in older adults. In 2 sessions separated by 1 week, we applied either slow-oscillatory stimulation or sham stimulation during an afternoon nap in a double-blind, crossover design. Memory tests were administered before and after sleep. A larger improvement in word-pair recall and higher slow-wave activity was observed with slow-oscillatory stimulation than with sham stimulation. This is the first demonstration that this procedure can improve memory in older adults, suggesting that declarative memory performance in older adults is partly dependent on slow-wave activity during sleep.