Age and sex related variations of MRI parameters of hippocampus and amygdala in healthy humans: A cross sectional study using a small cohort

Abstract

Introduction and Aim: Aging alters limbic structure, sex and hemispheric variations with anterior-posterior dominances of which are still obscure in relation to cognition in humans. Methodology: The present study included MRI coronal images for measurements of volumes [hippocampal volume (HV), amygdala volume (AV)], shapes [hippocampal angle (HA), medial distance ratio (MDR), parahippocampal angle (PHA)] and their hemispheric asymmetry indices (AI) in male and female healthy individuals of young and aged groups. The best-fitted formulae of 'volume index' (VI) and 'shape index' (SI) were evaluated for better interpretation. Results: In young, males showed larger bi-hemispheric volumes and AV/HV-ratios, greater HA and MDR values with distinct hemispheric dominances and greater VI with different SI values, compared to females. Aged subjects showed lesser VI and bi-hemispheric volumes compared to young counterparts where the decrement of volumes were more in aged males resulting in same volumes and AV/HV-ratios in both aged sexes. Only aged females exhibited greater HA and MDR values with altered SI compared to young counterparts retaining the sex-specific such differences with their altered AIs. The parametric changes showed significant correlations in respective cases. PHA remained unaltered in all cases. Conclusion: Sex-specific volume differences in young and volume reduction in age might associate with distinct alterations of hippocampal shapes viz. shifting of the (a) head (anterior portion) vertically compared to its horizontal position and (b) body (posterior portion) laterally toward temporal cortex, in both hemispheres. The recent findings claim further studies to unveil the cognitive variations corroborated with such limbic structural/shape alterations among sexes and ages.