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Abstract:
Past studies have shown that neonatal stimulation can enhance
performance in the Morris Water Maze Task (Meany et al 1987). In
this study, we examined how rats that were briefly exposed to a
novel environment during early life differed from controls in their
mental representation employed during spatial navigation. Animals
could use a map-based representation (allocentric memory) or a
route-based representation (egocentric memory)(McNaughton et
al.1991). From postnatal day 1 to 21, experimental pups (n=28) were
exposed to a novel environment for 3 minutes daily while control
pups (n=29) remained in the home cage. Starting at 23 days of age,
the pups were tested for 7 days in a moving platform version of the
Morris Water Maze Task. Egocentric and allocentric learning was
determined by comparing the rats' actual swim paths with predicted
ego or allocentric swim paths. We found that egocentric learning
scores did not differ significantly between the experimental and
control rats (p=0.405). In contrast allocentric learning scores in
experimental rats were significantly greater than the control rats
(p=0.032). The superior allo-centric learning among the
experimental rats suggests that neonatal stimulation may facilitate
the development of a map-based representation.
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