title: Dissociable representations of environmental size and complexity in the human hippocampus.
abstract: The hippocampus is widely assumed to play a central role in representing spatial layouts in the form of "cognitive maps." It remains unclear, however, which properties of the world are explicitly encoded in the hippocampus, and how these properties might contribute to the formation of cognitive maps. Here we investigated how physical size and complexity, two key properties of any environment, affect memory-related neural activity in the human hippocampus. We used functional magnetic resonance imaging and a virtual maze-learning task to examine retrieval-related activity for three previously learned virtual mazes that differed systematically in their physical size and complexity (here defined as the number of distinct paths within the maze). Before scanning, participants learned to navigate each of the three mazes; hippocampal activity was then measured during brief presentations of static images from within each maze. Activity within the posterior hippocampus scaled with maze size but not complexity, whereas activity in the anterior hippocampus scaled with maze complexity but not size. This double dissociation demonstrates that environmental size and complexity are explicitly represented in the human hippocampus, and reveals a functional specialization for these properties along its anterior-posterior axis.
authors.affiliation: Queensland Brain Institute, The University of Queensland, St. Lucia 4072, Queensland, Australia. o.baumann@uq.edu.au
authors.forename: Oliver
authors.initials: O
authors.lastname: Baumann
authors.forename: Jason B
authors.initials: JB
authors.lastname: Mattingley
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D003627:Data Interpretation, Statistical; D004777:Environment; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007858:Learning / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D018782:Maze Learning / Q000502:physiology; D011939:Mental Recall / Q000502:physiology; D010100:Oxygen / Q000097:blood; D011597:Psychomotor Performance / Q000502:physiology; D012858:Size Perception / Q000502:physiology*; D014584:User-Computer Interface; D055815:Young Adult
chemical_list: D010100:Oxygen