title: Depressive mood modulates the anterior lateral CA1 and DG/CA3 during a pattern separation task in cognitively intact individuals: a functional MRI study.
abstract: Although patients with major depressive disorder typically have a reduced hippocampal volume, particularly in the cornu ammonis 1 (CA1), animal studies suggest that depressive mood is related to the dentate gyrus (DG). In this study, our objective was to clarify which hippocampal subregions are functionally associated with depressive mood in humans. We conducted a functional MRI (fMRI) study on 27 cognitively intact volunteers. Subjects performed a modified version of a delayed matching-to-sample task in an MRI scanner to investigate pattern separation-related activity during each phase of encoding, delay, and retrieval. In each trial, subjects learned a pair of sample cues. Functional MR images were acquired at a high spatial resolution, focusing on the hippocampus. Subjects also completed the Beck Depression Inventory (BDI), a questionnaire about depressive mood. Depending on the similarity between sample cues, activity in the DG/CA3 and medial CA1 in the anterior hippocampus changed only during encoding. Furthermore, the DG/CA3 region was more active during successful encoding trials compared to false trials. Activity in the DG/CA3 and lateral CA1 was negatively correlated with BDI scores. These results suggest that the DG/CA3 is the core region for pattern separation during the encoding phase and interacts with the medial CA1, depending on the similarity of the stimuli, to achieve effective encoding. Impaired activity in the DG/CA3, as well as in the lateral CA1, was found to be associated with depressive symptoms, even at a subclinical level.
authors.affiliation: Research Center for Child Mental Development, University of Fukui, Yoshida-gun, Fukui Prefecture, Japan; Biomedical Imaging Research Center, University of Fukui, Yoshida-gun, Fukui Prefecture, Japan; Research and Education Program for Life Science, University of Fukui, Yoshida-gun, Fukui Prefecture, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fujii
authors.forename: Daisuke N
authors.initials: DN
authors.lastname: Saito
authors.forename: Hisakazu T
authors.initials: HT
authors.lastname: Yanaka
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Kosaka
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Okazawa
mesh_terms: D000339:Affect / Q000502:physiology*; D000704:Analysis of Variance; D001244:Association; D056547:CA1 Region, Hippocampal / Q000098:blood supply*; D056654:CA3 Region, Hippocampal / Q000098:blood supply*; D018891:Dentate Gyrus / Q000098:blood supply*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D011939:Mental Recall; D009483:Neuropsychological Tests; D010100:Oxygen; D010775:Photic Stimulation; D011930:Reaction Time; D064232:Visual Analog Scale; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: delayed matching-to-sample task; dentate gyrus; depression; hippocampal subregions; similarity; subclinical depressive mood