Cortical Thinning and Sleep Slow Wave Activity Reductions Mediate Age-Related Improvements in Cognition During Mid-Late Adolescence

Abstract

STUDY OBJECTIVES

Gains in cognitive test performance that occur during adolescence are associated with brain maturation. Cortical thinning and reduced sleep slow wave activity (SWA) are markers of such developmental changes. Here we investigate whether they mediate age-related improvements in cognition.

METHODS

109 adolescents aged 15-19y (49 males) underwent magnetic resonance imaging, polysomnography (PSG) and a battery of cognitive tasks within a 2-month time window. Cognitive tasks assessed non-verbal intelligence, sustained attention, speed of processing and working memory and executive function. To minimize the effect of sleep history on SWA and cognitive performance, PSG and test batteries were administered only after at least 8 nights of 9-h time-in-bed (TIB) sleep opportunity.

RESULTS

Age-related improvements in speed of processing (r = 0.33, p = 0.001) and non-verbal intelligence (r = 0.24, p = 0.01) domains were observed. These cognitive changes were associated with reduced cortical thickness, particularly in bilateral temporoparietal regions (rs = -0.21 to -0.45, ps < 0.05), as well as SWA (r = -0.35, p < 0.001). Serial mediation models found that ROIs in the middle/superior temporal cortices, together with SWA mediated the age-related improvement observed on cognition.

CONCLUSIONS

During adolescence, age-related improvements in cognition are mediated by reductions in cortical thickness and sleep slow wave activity.