Poster #4 - Declarative Memory in Toddlers: A Bedtime Story

• In Event: Poster Session 03

Abstract

Sleep is known to benefit learning and memory in infants (9-15 mos) and preschool-aged children (33-60 mos). However, very little research has examined sleep and learning in toddlers (16-31 mos), despite this being a period of significant and relevant neurodevelopmental changes, such as development of critical regions of the hippocampus (Gómez & Edgin, 2016). Furthermore, while much research has focused on the function of naps in early childhood, the contribution of overnight sleep on learning – when more rapid eye movement (REM) sleep occurs – is understudied. As such, we aim to assess the extent to which overnight sleep supports declarative memory in toddlers.
To achieve this, children are enrolled at either 16 or 21 months, as part of a larger longitudinal study on changes in sleep across toddlerhood. Toddlers are presented with an associative learning task (based on Prabhakar & Ghetti, 2019) where they learn different character-location pairings and are later asked to recreate the correct pairings. They encode one version of pairings in the morning, complete an immediate recall phase, and then complete a delayed recall phase in the early evening (wake condition). Toddlers then encode a second version of novel character-location pairings in the evening, complete immediate recall prior to sleep and recall the pairings again the following morning (sleep condition). Polysomnography is recorded during overnight sleep. Conditions and character-location presentations are counterbalanced across participants.
We hypothesize that toddlers will display superior memory performance following a period of overnight sleep relative to wake. With enough participants in both age groups, we hypothesize that 21-month-old toddlers will display less forgetting across the wake period as their hippocampus and other memory-related brain structures are likely more developed. Lastly, we hypothesize that more time spent in slow wave sleep and greater occurrences of related sleep microstructures (i.e., spindles) will be associated with better memory for the character-location pairings following overnight sleep. An alternative hypothesis, however, is that time spent in REM may be associated with better memory across the sleep condition, as REM sleep may play more of a role in memory consolidation at this age (Cao et al., 2020).
To test these hypotheses, differences in task performance between sleep and wake conditions will be compared using a repeated measures ANOVA. With sufficient power in each age group, a 2 (Condition: Sleep vs. Wake) x 2 (Group: 16 vs. 21 month) repeated measures ANOVA will be used to compare changes in task performance between groups. Pearson’s correlations will be used to assess relations between memory change across the sleep interval and sleep staging/microstructures.

Authors

• Jennifer F Holmes, University of Massachusetts Amherst
  Presenting Author

• Rebecca Spencer, University of Massachusetts, Amherst