Effects of neocortical ectopias and environmental enrichment on Hebb-Williams maze learning in BXSB mice

Approximately 40-60% of BXSB mice have neocortical ectopias, a developmenta l anomaly characterized by migration of neurons into the neuron-sparse laye r I of cortex. Previous studies have shown that ectopic BXSB mice have supe rior reference, but inferior working, memory on spatial tasks. Female BXSB mice were housed either in an enriched environment or in standard cages at weaning. Subsequently, these animals were tested on four of the Hebb-Willia ms mazes in a water-based version of this maze. Theoretically, two of the m aze configurations placed greater emphasis on reference memory to find the goal, whereas the other two favored working memory. Ectopics reared in stan dard housing conditions were better than nonectopics on mazes that favored the use of reference memory, but poorer on mazes that favored working memor y. In contrast, subjects raised in the enriched environment showed no ectop ia differences. A comparison of enriched and standard housing conditions fo und that the enriched animals had better reference memory but poorer workin g memory. The latter effect may be because the enriched environment, althou gh more stimulating, did not change in time or space; and other researchers have shown that daily replacement of stimuli in complex environments is co rrelated with better working memory, (C) 2001 Academic Press.