Spatial learning, discrimination learning, paw preference and neocortical ectopias in two autoimmune strains of mice.

NZB and BXSB mice were given a battery of behavioral tests including paw preference, water escape, Lashley III maze, and discrimination learning. Their brains were then evaluated for cortical ectopias. The incidence of ectopias was 40.5% in NZBs and 48.5% in BXSBs. In the NZB strain left-pawed ectopic mice (both male and female) had the fastest swimming time in the water escape test, while right-pawed ectopics were the slowest. The same findings were obtained for left- and right-pawed ectopic BXSB males, but not for the females. However, on discrimination learning the BXSB males had the exact opposite pattern: right-pawed ectopics were the best learners while left-pawed ectopics were the worst. Male BXSBs and both male and female NZBs were manifesting autoimmune disease at the time of testing, while female BXSBs were not, suggesting that autoimmunity is a necessary background condition for the differential expression of ectopias and paw preference upon learning processes. The finding that the left-pawed ectopic BXSB mice, who were the poorest learners in the non-spatial discrimination learning test, learned best in the spatial water escape test is in agreement with the Geschwind hypothesis that pathological events during brain development may, in some instances, produce superiority of function.