Early experience modifies the lateralization of emotionality in parietal lesioned rats

Male rats that were handled or not handled in infancy were given either unilateral parietal cortex lesions or unilateral parietal cortex lesions plus corpus callosum section as adults and tested on two independent measures of rodent emotionality, the Rodent Emotionality Rating scale and the open field. Lateralization of emotionality measured by open field ambulation and rearing only appeared in handled animals with right parietal cortex lesions plus transection of the corpus callosum. Notwithstanding, both the left and right parietal cortex were found to be involved in both aspects of emotionality when the corpus callosum was intact. It was the transection of the corpus callosum that brought out the interactive effects of the early experience manipulation and unilateral parietal lesion. Thus we have identified yet another role for the corpus callosum; one of mediating the effects of early experience in the lesioned brain.