SLEEP AND HIPPOCAMPAL DEVELOPMENT IN EARLY CHILDHOOD

Abstract Introduction With sleep, memories are consolidated, leaving them less susceptible to interference. This process is believed to reflect transfer of memories from the hippocampus to the cortex. Research has established that naps benefit memory in typically napping children. This nap-benefit has been associated with sleep spindles during nREM2 sleep. Although research has separately related memory development to the hippocampus and to sleep, the association between hippocampal development and sleep physiology is not understood. The purpose of this investigation is to assess relations between sleep physiology and the hippocampus in early childhood. Methods Subjects are part of an ongoing longitudinal investigation. Preliminary analyses included 24 participants (Mage= 3.96 years, 14 females). Children participated in three consecutive visits, one week apart. During the first two visits, they completed a visuospatial memory task before and after a wake or nap period (order counterbalanced). Sleep physiology was assessed via polysomnography and hippocampal volumes were obtained via Freesurfer v5.1 using T1-weighted scans (.9 mm3). Results Preliminary results showed that total hippocampal volume was positively related to minutes spent in nREM2 sleep when controlling for age and gender (B=14.7, p=0.03). Further analysis showed that this relation held for left but not right hippocampus (B=10.1, p=0.01). Results also indicate a positive relation between sleep spindle count and left but not right hippocampal volume when controlling for age and gender (B=16.1, p=0.02). Conclusion Results show that greater time spent in nREM2 and greater sleep spindles across nREM2 are both related to a larger hippocampus in early childhood. These findings demonstrate an association between sleep physiology and the hippocampus during an important period of memory development, early childhood. Future analyses will assess differences in hippocampal volume between typical nappers and non-nappers at the second wave of data collection. Support Support was provided by NIH (HD094758) and NSF (BCS 1749280).