The uterine environment enhances cognitive competence

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.

Evolution proposes and ontogeny disposes

Genes, the basic building blocks of evolution, are highly conserved. For example, the mouse and human have approximately the same number of genes, and around 94% are identical in the two species. Since species differ on multiple dimensions (e.g., anatomy, physiology, and behavior), it follows that identical genes may subserve different functions in different species. Two reasons for this are gene-gene interaction and gene-environment interaction (and it is the presence of these interactions which prevents one from making deterministic statements about genetics, thus rendering obsolete the nature-nurture controversy). Behavioral examples of both types of interactions are presented, including studies showing that (1) the uterine environment enhances later cognitive competence, (2) early postnatal experiences affect learning and emotionality and can extend into future generations, (3) maternal behavior changes the offspring's later behavior and physiology, and (4) knocking out one gene results in an animal less competent in one learning process but more competent in a complementary learning process.

Effects of the non-pseudoautosomal region of the Y-chromosome on behavior in female offspring of two congenic strains of mice

The learning behavior of female offspring of two strains of mice congenic for the Y-chromosome, BXSX/MpJ-Yaa and BXSB/MpJ-Yaa+, was examined. Significant differences were found in the Morris water maze and the Lashley III maze, demonstrating that the fathers' Y-chromosome can indirectly affect their daughters' behavior. Approximately half the mice had neocortical ectopias, and females from the two paternal groups reacted differently to the presence or absence of ectopias. Since females do not have a Y-chromosome, these effects must be through non-genetic mechanisms. Prenatal factors that could have played a role include possible differences in gonadal growth and the presence of different H-Y antigens. Postnatally, the sires and male siblings of the two strains may not have behaved the same toward the female offspring and/or the dams, creating differences in behavior. In summary, the behavior of female offspring of two groups of males, genetically the same except for their Y-chromosomes, was examined. Since females do not receive a Y-chromosome from their fathers, in theory their behavior should not differ. Significant differences were found, indicating that the Y-chromosome, through some indirect mechanism, can affect females of the next generation.