Immediate and long-lasting cognitive consequences of adolescent chronic sleep restriction.

Abstract

Adolescence is a critical developmental period. An important change that occurs in adolescence is the neurological maturation for adult-type cognitive abilities. Research has linked adequate sleep quantity to successful learning and memory capabilities. However, due to a shift in sleep timing drive in adolescence, in combination with early awakening for school, the adolescent population is experiencing chronic sleep restriction (CSR). What repercussions to long-term memory capabilities could CSR in adolescence have immediately and are the consequences longlasting? The present study modeled human adolescent CSR in rats through four hours of sleep deprivation for five days, followed by two days of unrestricted sleep, and five more days of four hours of sleep deprivation; thus the rats were exposed to CSR throughout the two-week rat adolescent period. Long-term hippocampal dependent and non-hippocampal dependent memory were tested through the object location task and the object recognition task, respectively. Testing occurred in adolescence and after a four-week delay during which the rats slept freely and matured to adulthood. The results showed that, given the appropriate conditions for successful long-term memory, the rats exposed to CSR in adolescence showed impaired hippocampal dependent memory in adolescence and this impairment was also evident in adulthood. These findings were not the case for non-hippocampal dependent memory, for which a significant effect of sleep was not found. Given the findings of the hippocampal dependent task, these results suggest that CSR in adolescence may influence less than optimal memory performance among adolescents. Further, the pattern in adulthood suggests that even after undisturbed sleep in the period from adolescence to adult maturation, the consequences of adolescent CSR are relentless. The findings in this study inform the research as the first rodent model of adolescent CSR and indicate practical implications for the health of adolescents.

Cognitive Reserve in Model Systems for Mechanistic Discovery: The Importance of Longitudinal Studies

“…Central for studies of brain maintenance and brain reserve, is the idea that early life events may influence the onset of age-related cognitive decline (Jagust, 2016;Hohman and Kaczorowski, 2020). Therefore, it is important to consider the phases of life in which a behavior is measured or experimental manipulation applied (e.g., Asiminas et al, 2019;Howard and Hunter, 2019). What is considered young or old may vary by animal model and strain.…”

Deepened sleep makes hippocampal spatial memory more persistent

“…Using a classical object-place recognition (OPR) task in rats, the present study confirms that sleep, in comparison with post-encoding wakefulness, enhances the consolidation of hippocampus-dependent memory. Previous studies demonstrated a beneficial effect of sleep for OPR memory tested up to 24 h after learning (Bett et al, 2013;Binder et al, 2012;Howard & Hunter, 2019;Ishikawa, Yamada, Pavlides, & Ichitani, 2014;Oyanedel et al, 2014;Ozawa, Yamada, & Ichitani, 2011). By systematically varying the duration and depth of post-encoding sleep, the present study goes beyond those previous findings indicating that sleep can strengthen OPR memory such that it is even maintained over one week.…”

Sleep Deprivation Aggravates Cognitive Impairment by the Alteration of Hippocampal Neuronal Activity and the Density of Dendritic Spine in Isoflurane-Exposed Mice

“…These results reveal that SD could deteriorate cognitive function in isoflurane-exposed mice by interfering with dCA1 neuronal activity and plasticity of dendritic spines. Available evidence have shown that both isoflurane exposure (Lin and Zuo, 2011;Liu et al, 2020) and SD (Howard and Hunter, 2019;Rajizadeh et al, 2020) can impair subsequent learning and short-time memory in adult rodents. Using the Y maze, we found that both isoflurane exposure and 24-h SD affected short-term memory in adult animals, which were in agreement with previous observations, and there was no significant difference between the two treatments.…”