Developmental Trajectories of Amygdala and Hippocampus from Infancy to Early Adulthood in Healthy Individuals

TLDR

Understanding amygdala and hippocampus development, particularly sex differences and laterality, is essential for linking brain volume to function, yet few studies have examined these regions during infancy. The study aimed to chart typical volumetric trajectories of the amygdala and hippocampus from infancy to early adulthood, focusing on sexual dimorphism and laterality. A cross‑sectional morphometric MRI study of 109 healthy participants aged 1 month to 25 years was conducted to assess amygdala and hippocampal growth. The results revealed nonlinear volume changes with peaks in preadolescence (9–11 y), earlier and faster growth in females, right‑lateralized hippocampal volumes in both sexes, male‑specific amygdalar laterality, and robust infant growth, suggesting that sex hormones and functional laterality influence amygdala and hippocampal development.

Abstract

Knowledge of amygdalar and hippocampal development as they pertain to sex differences and laterality would help to understand not only brain development but also the relationship between brain volume and brain functions. However, few studies investigated development of these two regions, especially during infancy. The purpose of this study was to examine typical volumetric trajectories of amygdala and hippocampus from infancy to early adulthood by predicting sexual dimorphism and laterality. We performed a cross-sectional morphometric MRI study of amygdalar and hippocampal growth from 1 month to 25 years old, using 109 healthy individuals. The findings indicated significant non-linear age-related volume changes, especially during the first few years of life, in both the amygdala and hippocampus regardless of sex. The peak ages of amygdalar and hippocampal volumes came at the timing of preadolescence (9–11 years old). The female amygdala reached its peak age about one year and a half earlier than the male amygdala did. In addition, its rate of growth change decreased earlier in the females. Furthermore, both females and males displayed rightward laterality in the hippocampus, but only the males in the amygdala. The robust growth of the amygdala and hippocampus during infancy highlight the importance of this period for neural and functional development. The sex differences and laterality during development of these two regions suggest that sex-related factors such as sex hormones and functional laterality might affect brain development.