Susceptibility to auditory closed-loop stimulation of sleep slow oscillations changes with age

• Published in: Sleep (New York, N.Y.) Vol. 43; no. 12; p. 1
• Main Authors: Schneider, Jules, Lewis, Penelope A, Koester, Dominik, Born, Jan, Ngo, Hong-Viet V
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 01.12.2020
• Subjects: Acoustic Stimulation; Adult; Age; Cognitive, Affective and Behavioral Neuroscience of Sleep; Comparative analysis; Electroencephalography; Humans; Memory Consolidation; Middle Aged; Sleep; Sleep, Slow-Wave; United Kingdom; Germany; sleep; ageing; sleep spindles; auditory closed-loop stimulation; memory; slow oscillations
• ISSN: 0161-8105; 1550-9109; 1550-9109
• DOI: 10.1093/sleep/zsaa111

Abstract Study Objectives Cortical slow oscillations (SOs) and thalamocortical sleep spindles hallmark slow wave sleep and facilitate memory consolidation, both of which are reduced with age. Experiments utilizing auditory closed-loop stimulation to enhance these oscillations showed great potential in young and older subjects. However, the magnitude of responses has yet to be compared between these age groups. We examined the possibility of enhancing SOs and performance on different memory tasks in a healthy middle-aged population using this stimulation and contrast effects to younger adults. Methods In a within-subject design, 17 subjects (55.7 ± 1.0 years) received auditory stimulation in synchrony with SO up-states, which was compared to a no-stimulation sham condition. Overnight memory consolidation was assessed for declarative word-pairs and procedural finger-tapping skill. Post-sleep encoding capabilities were tested with a picture recognition task. Electrophysiological effects of stimulation were compared to a previous younger cohort (n = 11, 24.2 ± 0.9 years). Results Overnight retention and post-sleep encoding performance of the older cohort revealed no beneficial effect of stimulation, which contrasts with the enhancing effect the same stimulation protocol had in our younger cohort. Auditory stimulation prolonged endogenous SO trains and induced sleep spindles phase-locked to SO up-states in the older population. However, responses were markedly reduced compared to younger subjects. Additionally, the temporal dynamics of stimulation effects on SOs and spindles differed between age groups. Conclusions Our findings suggest that the susceptibility to auditory stimulation during sleep drastically changes with age and reveal the difficulties of translating a functional protocol from younger to older populations.