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

Objective: To 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.

Methods: Resting 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.

Results: Left 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.

Conclusions: Our findings suggested that left and right mTLE exhibit different neural reorganization patterns of anterior and posterior hippocampal networks associated with verbal memory.

Significance: The findings may facilitate the characterization of mTLE associated with memory deficit.