Poster #4 - Hippocampal Subfield Volumes in Preschool-Aged Habitual Nappers and Non-Nappers

• In Event: Poster Session 05

Abstract

Early childhood is a developmental period marked by important changes in sleep habits (e.g., the cessation of napping; Kurdziel et al., 2013). During this same period, the hippocampus undergoes protracted development. Specifically, previous work has shown longitudinal changes in hippocampal subfield volume along the longitudinal axis from early to mid-childhood (e.g., Canada et al., 2021). Moreover, hippocampal subfield volumes have been shown to vary as a function of nap status in 4-6-year-old children, with habitual nappers having larger CA1 volume in the body than non-nappers (Riggins & Spencer, 2020). Our study aims to expand on these findings by investigating potential differences in hippocampal subfield volumes in a younger sample of 3- to 5-year-old children.
For this investigation, we utilized a cross-sectional sample of 26 subjects from a larger longitudinal study (Mage = 4.26 ± 0.61 years): 14 habitual nappers (children napping ≥ 5 days/week) and 12 non-nappers (children napping ≤ 2 days/week). Nap status was derived from Actigraphy data and sleep diaries collected over a two-week period prior to the MRI. During the MRI, a T1-weighted scan was collected and used to derive hippocampal subfield volumes and ICV via Freesurfer 6.0 (surfer.nmr.mgh.harvard.edu; Fischl, 2012).
Preliminary analyses of covariance (ANCOVAs) controlling for age and sex revealed significant differences between habitual nappers and non-nappers in CA2-4/DG (F(1,22) = 6.217, p = .0207). Specifically,habitual nappers demonstrated smaller volumes than non-nappers. This finding became marginal when adjusting for ICV (p = .0785). When breaking down this region into CA3 head and body and CA4/DG head and body, we found the following: a significant difference between nappers and non-nappers in CA3 head (F(1,22) = 4.92, p = .0373) and CA4/DG head (F(1,22) = 5.584, p = .02738), with nappers having smaller volumes than non-nappers for all regions. These findings became marginal when controlling for ICV (ps = .0670 - .0955). There were also marginal differences between habitual nappers and non-nappers in CA1 body (F(1,22) = 3.13, p = .0867) with nappers demonstrating smaller volumes than non-nappers. This became nonsignificant when controlling for ICV.
These findings suggest that young children who are habitual nappers have smaller hippocampi volume than their non-napping counterparts. Given the importance of the hippocampus for memory and the relations between memory and sleep, these findings contribute new knowledge regarding specific neural mechanisms underlying these associations during this developmental period . Future work in the lab aims to 1) increase our sample size within this young age range and 2) consider how hippocampal volume in intermediate nappers (those that nap 3-4 times per week) compare to the other groups.

Authors

• Jade Dunstan, University of Maryland - College Park
  Presenting Author

• Tamara Lynn Allard, University of Maryland - College Park

• Sanna Lokhandwala, University of Massachusetts Amherst

• Rebecca Spencer, University of Massachusetts, Amherst

• Tracy Riggins, University of Maryland - College Park