title: Dissociated signals in human dentate gyrus and CA3 predict different facets of recognition memory.
abstract: A wealth of evidence has implicated the hippocampus and surrounding medial temporal lobe cortices in support of recognition memory. However, the roles of the various subfields of the hippocampus are poorly understood. In this study, we concurrently varied stimulus familiarization and repetition to engage different facets of recognition memory. Using high-resolution fMRI (1.5 mm isotropic), we observed distinct familiarity and repetition-related recognition signal profiles in the dentate gyrus (DG)/CA3 subfield in human subjects. The DG/CA3 demonstrated robust response suppression with repetition and familiarity-related facilitation. Both of these discrete responses were predictive of different aspects of behavioral performance. Consistent with previous work, we observed novelty responses in CA1 consistent with "match/mismatch detection," as well as mixed recognition signaling distributed across medial temporal lobe cortices. Additional analyses indicated that the repetition and familiarity-related signals in the DG/CA3 were strikingly dissociated along the hippocampal longitudinal axis and that activity in the posterior hippocampus was strongly correlated with the retrosplenial cortex. These data provide novel insight into the roles of hippocampal subfields in support of recognition memory and further provide evidence of a functional heterogeneity in the human DG/CA3, particularly along the longitudinal axis.
authors.affiliation: Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders, and Center for Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, and.
authors.forename: Zachariah M
authors.initials: ZM
authors.lastname: Reagh
authors.affiliation: Department of Psychiatry, University of Iowa, Iowa City, Iowa 52242.
authors.forename: Joseph
authors.initials: J
authors.lastname: Watabe
authors.affiliation: Department of Psychiatry, University of Iowa, Iowa City, Iowa 52242.
authors.forename: Maria
authors.initials: M
authors.lastname: Ly
authors.affiliation: Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders, and Center for Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, and.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Murray
authors.affiliation: Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders, and Center for Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, and myassa@uci.edu.
authors.forename: Michael A
authors.identifier: http://orcid.org/0000-0002-8635-1498
authors.initials: MA
authors.lastname: Yassa
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D056654:CA3 Region, Hippocampal / Q000098:blood supply / Q000502:physiology*; D018891:Dentate Gyrus / Q000098:blood supply / Q000502:physiology*; D005145:Face; D005260:Female; D007839:Functional Laterality; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: CA3; dentate; fMRI; hippocampus; memory; recognition