Unraveling the adolescent brain: the role of sleep in brain maturation and cognitive development.

Adolescence is a critical period of rapid growth and transformation, marked by significant biological, cognitive, psychological, and social changes that lay the foundation for adulthood. Cognitively, there is rapid development in both crystallized and fluid intelligence, accompanied by improvements in processing speed and robustness as individuals transition from childhood to adolescence. These changes appear alongside key markers of brain maturation, particularly decreases in synaptic density and cortical grey matter volumes, as well as reductions of slow-wave activity (SWA) during sleep - likely reflecting the complex neurological development that supports the increasing cognitive capabilities observed in older adolescents. In this talk, we first explore cross-sectionally how cortical thickness and sleep slow wave activity mediate age-related improvements in cognition using data from mid-late adolescents who had polysomnography-assessed sleep, cognitive test batteries (sustained attention, speed of processing and nonverbal intelligence), and structural brain measures. We then extend these findings to early adolescence by investigating the effect of non-adherence to 24h movement behaviors, i.e. insufficient sleep, excessive screen time use and physical inactivity, on cognition (crystallized and fluid intelligence) and brain structure in 10,574 participants of the Adolescent Brain and Cognitive Development (ABCD) study, at baseline (9-11yo) and 2 years later. These two studies underscore the importance of sleep not just as a marker of brain maturation but as a modulator of optimal brain development and cognitive function.