Lateralization of spatial preference in the female rat

Female rat pups were either left undisturbed in infancy and raised in lab cages or were handled in infancy and raised in enriched environments. In adulthood, animals underwent brain surgery consisting of: 1) a right neocortical ablation, 2) a left neocortical ablation, 3) a sham operation, or 4) no surgery. After recovering, they were tested for the initial direction of movement (left or right) in the open field. Nonhandled intact females were biased to move leftward indicating an asymmetrical brain organization. The intact handled-enriched group was unbiased. The right and left lesions caused the animals to move ipsilateral to the lesion, but there was no difference in the magnitude or response in either early experience group. Thus, early experience in the female rat has a different effect then in the male, and the nature of the brain organization in the two sexes is markedly different.