title: Hippocampal activity patterns carry information about objects in temporal context.
abstract: The hippocampus is critical for human episodic memory, but its role remains controversial. One fundamental question concerns whether the hippocampus represents specific objects or assigns context-dependent representations to objects. Here, we used multivoxel pattern similarity analysis of fMRI data during retrieval of learned object sequences to systematically investigate hippocampal coding of object and temporal context information. Hippocampal activity patterns carried information about the temporal positions of objects in learned sequences, but not about objects or temporal positions in random sequences. Hippocampal activity patterns differentiated between overlapping object sequences and between temporally adjacent objects that belonged to distinct sequence contexts. Parahippocampal and perirhinal cortex showed different pattern information profiles consistent with coding of temporal position and object information, respectively. These findings are consistent with models proposing that the hippocampus represents objects within specific temporal contexts, a capability that might explain its critical role in episodic memory.
authors.affiliation: Center for Neuroscience, University of California at Davis, Davis, CA 95616, USA; Department of Psychology, University of California at Davis, Davis, CA 95616, USA. Electronic address: lthsieh@ucdavis.edu.
authors.forename: Liang-Tien
authors.initials: LT
authors.lastname: Hsieh
authors.affiliation: Center for Neuroscience, University of California at Davis, Davis, CA 95616, USA.
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Gruber
authors.affiliation: Center for Neuroscience, University of California at Davis, Davis, CA 95616, USA; Department of Psychology, University of California at Davis, Davis, CA 95616, USA.
authors.forename: Lucas J
authors.initials: LJ
authors.lastname: Jenkins
authors.affiliation: Center for Neuroscience, University of California at Davis, Davis, CA 95616, USA; Department of Psychology, University of California at Davis, Davis, CA 95616, USA.
authors.forename: Charan
authors.initials: C
authors.lastname: Ranganath
mesh_terms: D002540:Cerebral Cortex / Q000502:physiology; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D007858:Learning / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D061212:Memory, Episodic; D020534:Parahippocampal Gyrus / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012660:Semantics; D013028:Space Perception / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*