title: The parahippocampal gyrus links the default-mode cortical network with the medial temporal lobe memory system.
abstract: The default-mode network (DMN) is a distributed functional-anatomic network implicated in supporting memory. Current resting-state functional connectivity studies in humans remain divided on the exact involvement of medial temporal lobe (MTL) in this network at rest. Notably, it is unclear to what extent the MTL regions involved in successful memory encoding are connected to the cortical nodes of the DMN during resting state. Our findings using functional connectivity MRI analyses of resting-state data indicate that the parahippocampal gyrus (PHG) is the primary hub of the DMN in the MTL during resting state. Also, connectivity of the PHG is distinct from connectivity of hippocampal regions identified by an associative memory-encoding task. We confirmed that several hippocampal encoding regions lack significant functional connectivity with cortical DMN nodes during resting state. Additionally, a mediation analysis showed that resting-state connectivity between the hippocampus and posterior cingulate cortex--a major hub of the DMN--is indirect and mediated by the PHG. Our findings support the hypothesis that the MTL memory system represents a functional subnetwork that relates to the cortical nodes of the DMN through parahippocampal functional connections.
authors: Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts.
authors: Andrew M
authors: AM
authors: Ward
authors: Aaron P
authors: AP
authors: Schultz
authors: Willem
authors: W
authors: Huijbers
authors: Koene R A
authors: KR
authors: Van Dijk
authors: Trey
authors: T
authors: Hedden
authors: Reisa A
authors: RA
authors: Sperling
mesh_terms: D000293:Adolescent; D000328:Adult; D063132:Connectome / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D020534:Parahippocampal Gyrus / Q000502:physiology*; D012146:Rest / Q000502:physiology; D013647:Task Performance and Analysis; D013702:Temporal Lobe / Q000502:physiology*; D055815:Young Adult
keywords: MTL; Magnetic Resonance Imaging; Mediation; brain mapping; brain networks; functional connectivity; human; physiology; resting state; young adult
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