Organization of cortico-hippocampal networks in the human brain
Episodic memory depends on interactions between the hippocampus and the interconnected regions comprising default mode network (DMN). Here, using data-driven analyses of resting-state fMRI data, we identified the networks that interact with the hippocampus--the DMN and a "Medial Temporal Network" (MTN) that included regions in the medial temporal lobe and retrosplenial cortex. We observed that the MTN plays a critical role in connecting the visual network to the DMN and hippocampus. The DMN could be further divided into three subnetworks: a "Posterior-Medial" Subnetwork comprised of posterior cingulate, and lateral parietal cortices, an "Anterior-Temporal" Subnetwork comprised of regions in the temporopolar, and dorsomedial prefrontal cortex, and a "Medial-Prefrontal" Subnetwork comprised of regions primarily in the medial prefrontal cortex. These networks vary in their functional connectivity along the hippocampal long-axis and represent different kinds of information during memory-guided decision-making. Finally, a Neurosynth meta-analysis of fMRI studies suggests new hypotheses regarding the functions of the MTN and DMN subnetworks, providing a framework to guide future research on the neural architecture of episodic memory.