Relations Between Hippocampal Volume and Story Recall in Early Childhood

Research in adults and children suggest the hippocampus plays an important role in verbal memory (Ezzati et al., 2015; Gold & Trauner, 2014). However, links between verbal memory and the hippocampus in younger children remain relatively under investigated. This relation is important to study during early childhood (i.e., before 6 years) for at least two reasons. First, memory changes rapidly during this time and second, research in children suggests that age- related differences exist between memory and hippocampal subregion volumes (e.g. Riggins et al., 2015; Allard, Canada, & Riggins, March 2019). The current study addresses a gap in the literature by investigating the potential relation between hippocampal subregion volumes and verbal memory in early childhood. A total of 200 children, aged 4-8 years old (mean age=6.21 years, SD=0.11), were enrolled in a larger study on hippocampal memory development. Of these, 177 provided usable behavioral and MRI data. To assess verbal memory performance in these children, the stories subtest of the Children's Memory Scale was administered (Cohen, 1997). In the task, participants heard two stories read aloud by a researcher and were then asked to recall those stories immediately after hearing them, again one hour later, and again one week later. For the current study, analyses focused on the hour-delay performance in order to assess long term memory without the additional prompting that happened before the week-delay performance. Performance on the task was determined by the number of remembered verbatim story units. The maximum number of stories units to be remembered was 57 for both stories heard. Approximately one week following the verbal memory task, a T1-weighted structural MRI scan (0.9 mm3) was obtained. Hippocampal volumes were estimated via Freesurfer v5.1 (Fischl, 2012) and refined using ASAT (Wang et al., 2011). Hippocampal volumes were then divided into subregions (head, body, tail) using standard anatomical landmarks (Weiss, Dewitt, Goff, Ditman, & Heckers, 2005; Watson et al., 1992). Initial analyses examining hippocampal volume and verbal memory performance was non- significant. However, when a median age split was conducted, preliminary findings assessing relations between recall and hippocampal volumes revealed that younger (4- 6.13 years), but not older children (6.14-9 years) showed a significant positive relation between number of story units recalled and volume of the left hippocampal body (r=0.244, n=79, p=0.028). These findings are consistent with previous research that suggests developmental differences exist in brain-behavior relations during early childhood. It also supports the notion that a mature hippocampus is not necessarily larger in size (Riggins et al., 2015). These results reinforce an emerging body of work that propose age-related differences in associations between memory and hippocampal subregion volumes during development. Specifically, these results are consistent with previous findings that showed age-related differences between hippocampal body and performance on a visual spatial memory task and source memory in younger but not older children (Allard, Canada, & Riggins, March 2019; Riggins et al., 2015).Neurocognitive Development Lab and NIH Grant RO1 5205310 (TR)

Emotion regulation and reactivity are associated with cortical thickness in early to mid-childhood

This study explored the neural correlates of emotion regulation and emotional reactivity in early to mid-childhood. A sample of 96 children (70% White, mid-to-high socioeconomic status) aged 3–8 years provided structural neuroimaging data and caregivers reported on emotion regulation and emotional reactivity. The amygdala, insula, inferior frontal gyrus, anterior cingulate cortex, and medial orbitofrontal cortex were explored as a priori regions of interest (ROIs). ROI analyses revealed that emotion regulation was positively associated with cortical thickness in the insula, whereas emotional reactivity was negatively associated with cortical thickness in the inferior frontal gyrus. Exploratory whole-brain analyses suggested positive associations between emotion regulation and both left superior temporal thickness and right inferior temporal thickness, as well as negative associations between emotional reactivity and left superior temporal thickness. There were no significant associations between emotional regulation or reactivity and amygdala volume or cortical surface area. These findings support the notion that surface area and cortical thickness are distinct measures of brain maturation. In sum, these findings suggest that children may rely on a wider set of neural regions for emotion regulation and reactivity than adults, which is consistent with theories of interactive specialization across the life span.https://doi.org/10.1002/dev.2241