HIPPOCAMPAL DEVELOPMENT, SLOW WAVE ACTIVITY, AND NAP-DEPENDENT MEMORY CONSOLIDATION IN EARLY CHILDHOOD

Abstract Introduction Naps support memory consolidation in early childhood. In adults, nap-dependent declarative consolidation is associated with SWA. SWA increases from early childhood into adulthood, and the shift of SWA from occipital to frontal distribution (F/O-ratio) is a marker of brain maturation. Thus, we explored how electrophysiological and structural characteristics of brain development relate to nap-dependent declarative learning in early childhood. Methods Twelve preschool-age children (8 female, M=48 months, SD=0.44) have completed three sessions (~1wk apart) within a larger study. In the first two sessions, children completed a visuo-spatial task before and after a 2-hr nap or wake interval. During the third visit, children underwent MRI assessment. Using PSG, SWA was measured in the delta band over frontal and occipital regions for nREM2 and nREM3 sleep. Results While F/O-ratio of SWA does not currently predict the F/O-ratio of cortical thickness (r(12)=.383, p=.219), right parahippocampal thickness positively correlates with F/O-ratio of SWA in nREM2 (r(12)=.591, p=.043). Nonetheless, children’s performance change following the nap was not associated with either parahippocampal thickness or F/O-ratio of SWA in any sleep stage (all ps>.538). However, performance in children who showed a post-nap benefit (n=5) positively correlated with right parahippocampal thickness (r(5)=.915, p=.029). This was not the case for children who did not show a post-nap benefit (r(7)=-.199, p=.668). Conclusion Although the F/O-ratio of SWA did not predict a similar ratio of cortical thickness, the association between right parahippocampal thickness and F/O-ratio of SWA is evidence that development of SWA parallels cortical development. While there is no overall association between post-nap performance and brain development characteristics, the relation between performance and right parahippocampal thickness in children showing a nap benefit suggests that memory during this age may depend on structural (rather than electrophysiological) brain development changes. Support NIH R21 HD094758 & NSF BCS 1749280