Dissociable hippocampal representations of environmental size and complexity during active spatial navigation
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1
The University of Queensland, Queensland Brain Institute, Australia
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2
The University of Queensland, Queensland Brain Institute & School of Psychology, Australia
Several lines of evidence suggest that the hippocampus underlies the storage of cognitive maps. However, it is not yet completely understood which properties of the physical world form part of these mental representations. Here we used functional magnetic resonance imaging (fMRI) to investigate whether and how the physical size and complexity of an environment affects the neural signatures of its mental representation. The experiment consisted of two phases: a “learning phase,” in which participants actively navigated three different virtual mazes; and a “test phase,” in which participants viewed images from these virtual environments while undergoing fMRI. The three mazes varied systematically in size (defined as the summarised distance between landmarks) and complexity (defined as the average number of possible pathways between two landmarks), allowing us to assess the influence of these two factors independently. Critically, the number of discrete landmarks per maze and their categorical arrangement were held constant. We found that posterior hippocampal activity scaled with the maze size, whereas anterior hippocampal activity scaled with maze complexity. The enhanced posterior hippocampal signal complements earlier anatomical studies, which have suggested a relationship between the size of a learned environment and the volume of this brain structure. The finding that environmental complexity is encoded in the anterior hippocampus suggests a role for this region in path planning and spatial decision-making. Taken together, the current findings suggest that the hippocampus is involved in the incidental encoding and storage of an information-rich representation of the external environment during active spatial navigation.
Acknowledgements
This work was supported by the Australian Research Council (FL110100103, TS0669699 to J.B.M. and DE120100535 to O.B.)
Keywords:
cognitive map,
Hippocampus,
spatial memory,
navigation,
parahippocampal cortex
Conference:
ACNS-2012 Australasian Cognitive Neuroscience Conference, Brisbane, Australia, 29 Nov - 2 Dec, 2012.
Presentation Type:
Oral Presentation
Topic:
Memory
Citation:
Baumann
O and
Mattingley
JB
(2012). Dissociable hippocampal representations of environmental size and complexity during active spatial navigation.
Conference Abstract:
ACNS-2012 Australasian Cognitive Neuroscience Conference.
doi: 10.3389/conf.fnhum.2012.208.00017
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Received:
25 Oct 2012;
Published Online:
07 Nov 2012.
*
Correspondence:
Dr. Oliver Baumann, The University of Queensland, Queensland Brain Institute, St Lucia, Queensland, 4072, Australia, obaumann@bond.edu.au