Females exhibit smaller volumes of brain activation and lower inter-subject variability during motor tasks

Abstract

Past work has shown that brain structure and function differ between females and males. Males have larger cortical and sub-cortical volume and surface area (both total and subregional), while females have greater cortical thickness in most brain regions. Functional differences are also reported in the literature, yet to date little work has systematically considered whether patterns of brain activity indexed with functional magnetic resonance imaging (fMRI) differ between females and males. Recently, an attempt to modernize and improve our understanding of the homunculus, a somatotopic representation of the human body within the brain, was made. Still, in the decades since it was introduced, no research has considered sex differences in the somatotopic representation. The current study sought to remediate this issue by employing brain somatotopic motor mapping from a previously published and openly available dataset. We tested differences in patterns of functional brain activity associated with 12 voluntary movement patterns in females versus males. Results suggest that females exhibited smaller volumes of brain activation across all 12 movement tasks, and lower patterns of variability in 10 of the 12 movements. We also observed that females had greater cortical thickness, which is in alignment with previous analyses of structural differences. Overall, these findings provide a basis for considering biological sex in future fMRI research and provide a foundation of understanding differences in how neurological pathologies present in females vs males.