Sex differences in functional connectivity of episodic memory networks using naturalistic stimuli

Abstract

Males and females exhibit differences in episodic memory, both behaviourally and neurally. Previous research suggests that females have a general episodic memory advantage, however the neural correlates underlying this advantage remain unclear. There are significant advantages to using naturalistic stimuli for uncovering memory networks, however, there remains a gap in the literature examining recognition related network differences between older males and females using such stimuli. In the present study, 35 older adults (age 55-75 years, 17 females) encoded six narrative-driven, naturalistic scenes. Seven days later, all participants completed a delayed recognition task during functional magnetic resonance imaging (fMRI), in which they viewed three previously encoded and three novel scenes. To identify differences in functional connectivity during recognition, we used functional connectivity multivariate pattern analysis (fc-MVPA) followed by post-hoc seed-based correlations (SBC). Fc-MVPA revealed eight clusters exhibiting significant differences in functional connectivity between females and males, including the left postcentral gyrus, bilateral precuneus/posterior cingulate cortex, left hippocampus, left parietal operculum cortex, left cerebellum 4 5, right posterior middle temporal gyrus, left paracingulate gyrus, left superior frontal gyrus. SBC from these clusters showed widespread differences in whole brain memory networks between males and females. Notably, the left hippocampal region of interest showed significantly greater connectivity with the default mode network (DMN) in males than females. These findings suggest older females and males exhibit distinct patterns of functional connectivity during recognition of naturalistic stimuli despite comparable recall performance. More broadly, we provide evidence for different episodic memory network architecture between older females and males that may help inform more global episodic memory systems.