Functional connectivity analysis of parahippocampal-hippocampal networks in resting human brain state

Abstract

Resting-state functional magnetic resonance imaging (rs-fMRI) is a powerful tool for investigating the intrinsic functional organization of the brain in the absence of explicit tasks. Functional connectivity analyses show that spatially coherent networks exhibit synchronized spontaneous blood-oxygen-level dependent signal fluctuations. This study characterizes the resting-state intra-regional functional connectivity within the left and right hippocampus, and the parahippocampal gyrus to understand within-network connectivity across the medial temporal lobe (MTL). Resting-state fMRI data from a healthy participant were analyzed using pairwise voxel correlation matrices calculated through Pearson, Spearman and Kendall correlations to characterize the coherence and variability of intra-regional BOLD signal time series in each region of interest. Positive correlations predominated across all MTL subregions, confirming broad intra-regional functional coherence at rest. The left hippocampus exhibited greater synchrony than the right, consistent with functional lateralization. The posterior parahippocampal gyrus displayed higher and more concentrated coherence compared to the anterior subdivision, which showed a broader and more variable correlation structure. These findings can provide a baseline for future studies into how neurodegenerative diseases disrupt these functional architecture.