title: Linking major depression and the neural substrates of associative processing.
abstract: It has been proposed that mood correlates with the breadth of associative thinking. Here we set this hypothesis to the test in healthy and depressed individuals. Generating contextual associations engages a network of cortical regions including the parahippocampal cortex (PHC), retrosplenial complex, and medial prefrontal cortex. The link between mood, associative processing, and its underlying cortical infrastructure provides a promising avenue for elucidating the mechanisms underlying the cognitive impairments in major depressive disorder (MDD). The participants included 15 nonmedicated individuals with acute major depressive episodes and 15 healthy matched controls. In an fMRI experiment, participants viewed images of objects that were either strongly or weakly associated with a specific context (e.g., a beach chair vs. a water bottle) while rating the commonality of each object. Analyses were performed to examine the brain activation and structural differences between the groups. Consistent with our hypothesis, controls showed greater activation of the contextual associations network than did depressed participants. In addition, PHC structural volume was correlated with ruminative tendencies, and the volumes of the hippocampal subfields were significantly smaller in depressed participants. Surprisingly, depressed participants showed increased activity in the entorhinal cortex (ERC), as compared with controls. We integrated these findings within a mechanistic account linking mood and associative thinking and suggest directions for the future.
authors.affiliation: Beer Yaakov Mental Health Center affiliated with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. eiranharel@gmail.com.
authors.forename: Eiran Vadim
authors.initials: EV
authors.lastname: Harel
authors.affiliation: Department of Anthropology, University of Washington, Seattle, WA, USA.|Center for Studies of Demography and Ecology, University of Washington, Seattle, WA, USA.
authors.forename: Robert Langley
authors.initials: RL
authors.lastname: Tennyson
authors.affiliation: Division of Clinical Research, Massachusetts General Hospital Research Institute, Boston, MA, USA.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Fava
authors.affiliation: Gonda Center for Brain Research, Bar-Ilan University, Ramat Gan, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Bar
mesh_terms: D000328:Adult; D001244:Association; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001931:Brain Mapping; D003865:Major Depressive Disorder / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D007406:Interview, Psychological; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000503:physiopathology; D009483:Neuropsychological Tests; D009929:Organ Size; D011569:Psychiatric Status Rating Scales; D057566:Self Report; D014796:Visual Perception / Q000502:physiology
keywords: Associations; Context; Depression; Entorhinal; Parahippocampus; Rumination