The Journal of Neuroscience, June 1, 2001, 21(11):4016-4025
Instability in the Place Field Location of Hippocampal Place
Cells after Lesions Centered on the Perirhinal Cortex
Gary M.
Muir and
David K.
Bilkey
Department of Psychology, University of Otago, Dunedin, 9001, New
Zealand
The perirhinal cortex appears to play a key role in memory, and the
neighboring hippocampus is critically involved in spatial processing.
The possibility exists, therefore, that perirhinal-hippocampal interactions are important for spatial memory processes. The purpose of
the present study was to investigate the contribution of the perirhinal
cortex to the location-specific firing ("place field") of
hippocampal complex-spike ("place") cells. The firing
characteristics of dorsal CA1 place cells were examined in rats with
bilateral ibotenic acid lesions centered on the perirhinal cortex
(n = 4) or control surgeries (n = 5) as they foraged in a rectangular environment. The activity of
individual place cells was also monitored after a delay period of
either 2 min, or 1 or 24 hr, during which time the animal was removed
from the environment.
Although the perirhinal cortex lesion did not affect the place field
size or place cell firing characteristics during a recording session,
it was determined that the location of the place field shifted position
across the delay period in 36% (10 of 28) of the cells recorded from
lesioned animals. In contrast, none of the place cells (0 of 29)
recorded from control animals were unstable by this measure.
These data indicate that although the initial formation of place fields
in the hippocampus is not dependent on perirhinal cortex, the
maintenance of this stability over time is disrupted by perirhinal
lesions. This instability may represent an erroneous "re-mapping"
of the environment and suggests a role for the perirhinal cortex in
spatial memory processing.
Key words:
rhinal cortex; spatial memory; parahippocampal; cognitive
map; Alzheimer's disease; aging; navigation; dorsal hippocampus; rat; single unit recording
Copyright © 2001 Society for Neuroscience 0270-6474/01/21114016-10$05.00/0
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