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Sleep loss disrupts the neural signature of successful learning.
Guttesen, AÁV, Gaskell, MG, Madden, EV, Appleby, G, Cross, ZR, Cairney, SA
Cerebral cortex (New York, N.Y. : 1991). 2023;33(5):1610-1625
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Understanding how sleep disturbances impair learning and memory is increasingly important in modern society, where many people fail to regularly obtain an adequate amount of sleep. The aim of this study was to investigate the relationship between sleep-associated consolidation and next-day learning and how suppressing slow-wave activity (SWA) [during slow-wave sleep, electrical activity in the brain changes while the body relaxes into deep and restorative rest] contributes to this relationship. This study was a within-subjects (n = 30), crossover design which showed that sleep improved both memory retention and next-day learning however, there was no evidence of a relationship between these measures or with SWA. Furthermore, an absence of sleep disrupts the neural operations underpinning memory encoding, leading to suboptimal performance. Authors conclude that an extended lack of sleep might disrupt the ability to draw upon semantic knowledge when encoding novel associations, necessitating the use of more surface-based and ultimately suboptimal routes to learning.
Abstract
Sleep supports memory consolidation as well as next-day learning. The influential "Active Systems" account of offline consolidation suggests that sleep-associated memory processing paves the way for new learning, but empirical evidence in support of this idea is scarce. Using a within-subjects (n = 30), crossover design, we assessed behavioral and electrophysiological indices of episodic encoding after a night of sleep or total sleep deprivation in healthy adults (aged 18-25 years) and investigated whether behavioral performance was predicted by the overnight consolidation of episodic associations from the previous day. Sleep supported memory consolidation and next-day learning as compared to sleep deprivation. However, the magnitude of this sleep-associated consolidation benefit did not significantly predict the ability to form novel memories after sleep. Interestingly, sleep deprivation prompted a qualitative change in the neural signature of encoding: Whereas 12-20 Hz beta desynchronization-an established marker of successful encoding-was observed after sleep, sleep deprivation disrupted beta desynchrony during successful learning. Taken together, these findings suggest that effective learning depends on sleep but not necessarily on sleep-associated consolidation.
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Partial sleep restriction-induced changes in stress, quality of life, and lipid metabolism in relation to cold hypersensitivity: A before-and-after intervention study.
Baek, Y, Jung, K, Kim, H, Lee, S
Medicine. 2022;101(46):e31933
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Inadequate sleep has been associated with an increased risk of cardiovascular disease and has an adverse impact on quality of life (QOL), metabolism and the immune system. Furthermore, sleep is associated with the body’s thermoregulation ability, which is closely associated with distal and proximal skin temperature, as well as core body temperature. The hypothesis of this study was that the physiological and psychological changes caused by insufficient sleep will differ according to cold hypersensitivity (CH). This study was an uncontrolled, before-and-after study with 3 days of 4-hour sleep restriction (SR) as intervention. A total of 130 participants completed the study. Results showed that less-than-optimal sleep duration leads to worsened stress and QOL and reduced low-density lipoprotein cholesterol levels. These changes were significant in the CH group compared to the non-CH group. Authors conclude that their findings provide additional information for evaluating the clinical risks posed by sleep disturbances and assessing the usual sleep patterns according to CH.
Abstract
Sleep disturbances are associated with cold hypersensitivity (CH) and characterized by excessive cold sensation in specific body parts and cold thermal discomfort. This study investigated the effects of short-term sleep restriction followed by a recovery phase on subjective health status, inflammation, and lipid metabolism in different types of CH. A total of 118 healthy adults aged 35 to 44 years without sleep disturbances were enrolled. Participants underwent 4-hour sleep restrictions per day for 3 days at a hospital and then returned to their daily lives for 4 days of rest. CH was assessed using a structured questionnaire with eight characteristic symptoms. A questionnaire and blood tests were administered baseline, after sleep restriction, and follow-up to assess cortisol, lipid profiles, and self-reported stress and quality of life (QOL). Participants were divided into CH (44.1%) and non-CH (55.9%) groups. The CH group showed increased stress, impaired QOL, and decreased low-density lipoprotein-cholesterol (LDL-C) levels compared to the non-CH group after sleep restriction. The variance for QOL (effect size = 0.07), subjective stress (effect size = 0.053), and LDL-C (effect size = 0.029) among time points depended on the group. Short-term sleep restriction was associated with deterioration of subjective health and reduced lipid metabolism; such changes were more evident in the CH group. Our findings suggest the need to consider an individual's CH status to assess the clinical risk associated with insufficient sleep.