Ns. Waters et al., EFFECTS OF CORTICAL ECTOPIAS ON SPATIAL DELAYED-MATCHING-TO-SAMPLE PERFORMANCE IN BXSB MICE, Behavioural brain research, 84(1-2), 1997, pp. 23-29
BXSB mice have small neocortical anomalies (ectopic collections of neu
rons in layer I), with an incidence of about 40-60%. Previous studies
have found that ectopic mice from this strain are faster than non-ecto
pics in learning the Morris water maze (reference memory), but have po
orer working memory for spatial learning. The current study continues
the investigation of working memory by testing ectopic and non-ectopic
BXSB mice on a spatial delayed-matching-to-sample test (S-DMTS; also
called spatial learning sets or 'working memory' water maze). In this
test, the mice must find a submerged platform in a pool of water. The
platform changes location with every problem, or block of four trials.
The subject has 'matched to sample' if it locates the platform in les
s time on the second trial of each problem than it did on the first. O
f 33 subjects, 8 had cortical ectopias, one had a small neuron-free gl
iotic area, and 24 were normal. The normal subjects showed a decrease
in time to escape over the first 2 trials of the first 5 problems, whi
le the ectopic subjects did not show a decrease until the third trial,
indicating that ectopic mice required more trials to put the platform
location into working memory. The site of the ectopias is prefrontal/
motor cortex, and we hypothesize that is the cause of the poorer worki
ng memory.