Effects of the uterine environment and neocortical ectopias upon behavior of BXSB-Yaa+ mice.

Between 40-60% of BXSB-Yaa+mice have neocortical ectopias, a genetically based brain anomaly. The presence of ectopias is known to affect several cognitive measures. A second way to affect cognition is by transferring embryos into foreign uteri. These variables were jointly investigated in three experiments. BXSB-Yaa+mouse embryos were transferred into same-strain uteri, or into uteri of hybrid mice. At birth, pups were cross-fostered to hybrid mothers or were reared by their birth mothers. When adult, the mice were given a series of behavioral tests with primary emphasis upon cognitive competence. Across all three studies, mice transferred into hybrid uteri were superior in the Morris maze and the Lashley III maze, and performed more effectively in shuttlebox avoidance learning. They were less effective in the simple water escape task, and the uterus groups did not differ in discrimination learning. Thus, development within a foreign uterus enhanced spatial learning and fear-based conditioning. Ectopic mice were superior to non-ectopics in learning the Morris maze, a finding consistent with prior research using the congenic BXSB-Yaa strain. There were Uterus x Ectopia interactions on a few measures, indicating that, under certain condition, whether the presence of ectopias is beneficial or detrimental is contingent upon the uterine environment within which the organism develops.