Reorganization of anterior and posterior hippocampal networks associated with memory performance in mesial temporal lobe epilepsy

•Functional connectivity based on resting-state fMRI was analyzed in mesial temporal lobe epilepsy (mTLE) patients with unilateral hippocampal sclerosis.•Left and right mTLE have differential organization of anterior and posterior hippocampal networks.•The alterations of functional connectivity in mTLE were related to verbal memory performance.

ObjectiveTo investigate the pattern of functional demarcation of hippocampal network and its relationship with memory performance in mesial temporal lobe epilepsy (mTLE) with unilateral hippocampal sclerosis.MethodsResting state fMRI data were acquired from fifteen left mTLE patients, fourteen right mTLE patients and twenty healthy subjects. We explore the hippocampal-cortical alterations and corresponding inter-hemispheric functional connectivity (FC) across anterior and posterior hippocampal networks. The association between FC and memory performance was assessed.ResultsLeft mTLE showed increased intra-hemispheric FC in anterior hippocampal networks, including left anterior hippocampal-entorhinal cortex and right anterior hippocampal-orbitofrontal cortex, and decreased inter-hemispheric FC between anterior hippocampus, entorhinal cortex and posterior cingulate cortex. Right mTLE was associated with extensive reduction in inter-hemispheric FC along the areas of anterior and posterior hippocampal networks. Intra-hemispheric FC between left anterior hippocampus and entorhinal cortex was positively correlated with verbal memory in left mTLE. Inter-hemispheric FC between posterior parahippocampal gyrus was negatively correlated with verbal memory in right mTLE.ConclusionsOur findings suggested that left and right mTLE exhibit different neural reorganization patterns of anterior and posterior hippocampal networks associated with verbal memory.SignificanceThe findings may facilitate the characterization of mTLE associated with memory deficit.