The Journal of Neuroscience, January 15, 1998, 18(2):804-810
Memory for Spatial Location: Role of the Hippocampus in Mediating
Spatial Pattern Separation
Paul E.
Gilbert,
Raymond P.
Kesner, and
William E.
DeCoteau
University of Utah, Salt Lake City, Utah 84112
A paradigm based on measuring short-term memory for spatial
location information as a function of spatial similarity between distal
cues was developed to examine the role of pattern separation in the
modulation of short-term memory for spatial information. A
delayed-match-to-sample for spatial location task using a dryland version of the Morris water maze was used to assess spatial pattern separation in male Long-Evans rats. In the sample phase, animals were
trained to displace an object that covered a baited food well in one of
15 spatial locations along a row of food wells perpendicular to a start
box. In the ensuing choice phase, the animal was allowed to choose
between two objects identical to the sample phase object. One covered
the same baited food well as did the object in the study phase (correct
choice), and another foil object (incorrect choice) covered a different
unbaited food well along the row of wells. Five spatial separations
were randomly used to separate the correct object from the foil object.
After reaching a criterion before the operation, animals were given either hippocampal or cortical control lesions. In trials after the
operation, control animals matched their performance before the
operation across all spatial separations. In contrast,
hippocampal-lesioned animals displayed impairments across all spatial
separations with the exception of the longest (105 cm) spatial
separation. The results suggest that the hippocampus may serve to
separate incoming spatial information by temporarily storing one place
separate from another. It is proposed that hippocampal lesions decrease efficiency in pattern separation, resulting in impairments in trials
with increased spatial similarity among working-memory representations.
Key words:
hippocampus; pattern separation; spatial memory; spatial
location; working memory; dentate gyrus
Copyright © 1998 Society for Neuroscience 0270-6474/98/182804-07$05.00/0
