title: Associative encoding and retrieval are predicted by functional connectivity in distinct hippocampal area CA1 pathways.
abstract: Determining how the hippocampus supports the unique demands of memory encoding and retrieval is fundamental for understanding the biological basis of episodic memory. One possibility proposed by theoretical models is that the distinct computational demands of encoding and retrieval are accommodated by shifts in the functional interaction between the hippocampal CA1 subregion and its input structures. However, empirical tests of this hypothesis are lacking. To test this in humans, we used high-resolution fMRI to measure functional connectivity between hippocampal area CA1 and regions of the medial temporal lobe and midbrain during extended blocks of associative encoding and retrieval tasks. We found evidence for a double dissociation between the pathways supporting successful encoding and retrieval. Specifically, during the associative encoding task, but not the retrieval task, functional connectivity only between area CA1 and the ventral tegmental area predicted associative long-term memory. In contrast, connectivity between area CA1 and DG/CA3 was greater, on average, during the retrieval task compared with the encoding task, and, importantly, the strength of this connectivity significantly correlated with retrieval success. Together, these findings serve as an important first step toward understanding how the demands of fundamental memory processes may be met by changes in the relative strength of connectivity within hippocampal pathways.
authors.affiliation: Department of Psychology, Columbia University, New York, New York 10027 and.
authors.forename: Katherine
authors.initials: K
authors.lastname: Duncan
authors.affiliation: Department of Psychology and.
authors.forename: Alexa
authors.initials: A
authors.lastname: Tompary
authors.affiliation: Department of Psychology and Center for Neural Science, New York University, New York, New York 10003 lila.davachi@nyu.edu.
authors.forename: Lila
authors.initials: L
authors.lastname: Davachi
mesh_terms: D000328:Adult; D001245:Association Learning / Q000502:physiology*; D056547:CA1 Region, Hippocampal / Q000098:blood supply / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D057567:Memory, Long-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D009434:Neural Pathways / Q000098:blood supply / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D018709:Statistics, Nonparametric; D017557:Ventral Tegmental Area / Q000098:blood supply; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: CA1; CA3; VTA; functional connectivity; high-resolution fMRI; hippocampus