Poster #6 - Longitudinal investigation of hippocampal functional connectivity at rest and episodic memory in early childhood

• In Event: 3-053 - Poster Session 10
  In Poster Session: PS 10 Section - Attention, Learning, Memory

Integrative Statement

Hippocampus has been consistently reported to be an important neural substrate for memory in adults (e.g., Xue, 2018). Recently, researchers have started applying neuroimaging methods (e.g., functional and structural MRI) to studies focusing on young population. For example, by using functional MRI, our studies have indicated age- and memory-related differences in hippocampal functional connectivity during rest in early childhood (e.g., Riggins, Geng, Blankenship, & Redcay, 2016; Blankenship et al., 2016). These studies suggested that hippocampus might underlie the significant development of memory abilities between the age of 4 and 8 years. However, these investigations have used cross-sectional study design, which may involve confound variables hard to control. To overcome the shortcomings of this design, the current study would use longitudinal design to investigate the age- and memory-related differences in hippocampal functional connectivity during rest between the age of 4 and 8 years. We predict that both age- and memory-related differences in hippocampal functional connectivity at rest would be observed.
A total of 58 children provided both useable MRI and behavioral memory data. Among them, 30 children (4-year cohort) participated three scan sessions when they were at the age of 4 (Mean = 4.44 years, SD = 0.28), 5 (Mean = 5.46 years, SD = 0.28), and 6 years (Mean = 6.47 years, SD = 0.28); 28 children (6-year cohort) did these three sessions at the age of 6 (Mean = 6.47 years, SD = 0.27), 7 (Mean = 7.51 years, SD = 0.28), and 8 (Mean = 8.48 years, SD = 0.27) years old. Functional and structural MRI data were preprocessed using the Data Processing Assistant for Resting-state fMRI Advanced Edition (DPARSF-A, version 3.1) toolbox (Yan and Zang, 2010). All children had mean FD ≤ 0.4 and scan length ≥ 4.5 minutes. In addition, we scrubbed any volumes with the framewise displacement (FD) ≥ 0.3 mm as well as 1 back and 1 forward volumes. Memory ability was measured by episodic memory task adapted from previous studies (Drummey & Newcombe, 2002; Riggins, 2014). A mixed ANOVA model was used to analyze behavioral data. The 3dLME embedded in AFNI was used to analyze hippocampal functional connectivity. The 3dClustSim mixed model autocorrelation function (ACF) indicated that clusters with a minimum of 58 voxel size and puncorrected < .005 were viewed as significant with multiple comparison correction (pcorrected < .05).

Behavioral results indicated that for 4-year cohort, 6-year-old children showed better source memory ability than 4-year-old children (F (1, 29) = 30.72, p < .001). For 6-year cohort, 7-year-old children performed better than 6-year-old children did in source memory task (F (1, 27) = 5.60, p < .025), see Figure 1. Resting-state functional connectivity results indicated that age was positively related to the connectivity from hippocampus to left cerebellum, left anterior cingulate, and precuneus. In addition, memory was related to the connectivity from hippocampus to right fusiform gyrus, see Figure 2.
The findings of this longitudinal study support previous studies that there are age- and memory-related differences in hippocampal functional connectivity during rest in early childhood.

Authors

• Fengji Geng, Zhejiang University
  Presenting Author

• Tracy Riggins, University of Maryland
  Non-Presenting Author