Sex differences in the effects of early experience on the development of behavioral and brain asymmetries in rats.

The influence of early experience (preweaning handling) on the development of several postural/motor asymmetries (side bias in an open field, turn preference in a T-maze, amphetamine-induced rotational behavior, tail pinch-induced asymmetries) and the lateralization of brain dopamine was studied in adult male and female rats. In many cases the adult patterns of behavioral and brain asymmetries were modified by early handling in a sexually dimorphic manner. In addition, the direction of postural/motor asymmetries was very much task-dependent, especially in females. We conclude that: early experience may modify the development of behavioral and brain asymmetries; sex differences in asymmetries are very common; early handling may affect males and females differently; and different measures of postural/motor asymmetries may reflect different and multiple brain asymmetries.