The Journal of Neuroscience, June 1, 2001, 21(11):3986-4001
Temporary Inactivation of the Retrosplenial Cortex Causes a
Transient Reorganization of Spatial Coding in the Hippocampus
Brenton G.
Cooper and
Sheri
J. Y.
Mizumori
Department of Psychology, University of Utah, Salt Lake City, Utah
84112
The ability to navigate accurately is dependent on the integration
of visual and movement-related cues. Navigation based on metrics
derived from movement is referred to as path integration. Recent
theories of navigation have suggested that posterior cortical areas,
the retrosplenial and posterior parietal cortex, are involved in path
integration during navigation. In support of this hypothesis, we have
found previously that temporary inactivation of retrosplenial cortex
results in dark-selective impairments on the radial maze (Cooper and
Mizumori, 1999). To understand further the role of the retrosplenial
cortex in navigation, we combined temporary inactivation of
retrosplenial cortex with recording of complex spike cells in the
hippocampus. Thus, behavioral performance during spatial memory testing
could be compared with place-field responses before, and during,
inactivation of retrosplenial cortex. In the first experiment,
behavioral results confirmed that inactivation of retrosplenial cortex
only impairs radial maze performance in darkness when animals are at
asymptote levels of performance. A second experiment revealed that
retrosplenial cortex inactivation impaired spatial learning during
initial light training. In both experiments, the normal location of
hippocampal "place fields" was changed by temporary inactivation of
retrosplenial cortex, whereas other electrophysiological properties of
the cells were not affected. The changes in place coding occurred in
the presence, and absence, of behavioral impairments. We suggest that
the retrosplenial cortex provides mnemonic spatial information for
updating location codes in the hippocampus, thereby facilitating
accurate path integration. In this way, the retrosplenial cortex and
hippocampus may be part of an interactive neural system that mediates navigation.
Key words:
navigation; place cells; path integration; spatial
memory; head direction; posterior cingulate cortex
Copyright © 2001 Society for Neuroscience 0270-6474/01/21113986-16$05.00/0
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