New evidence for distinct patterns of brain organization in rats differentiated on the basis of inherent laterality.

The purpose of the present study was to search for possible relationships among diverse measures of behavioral laterality in a non-human species or to identify an index of laterality that was predictive of other non-lateralized functions. Several indices of behavioral laterality and open field activity were assessed in male and female rats before and after asymmetric neocortical ablations. Plasma adrenocorticotropin, corticosterone, and prolactin were measured following stress at sacrifice. Sex-dependent population-level lateral biases were observed preoperatively in the choice of arms in a T-maze and initial direction out of a corner of an open field. Unilateral left neocortical ablation induced a leftward bias in the T-maze in both male and female rats. The direction of rotation following the peripheral administration of amphetamine was correlated with: (a) the degree of sensitization to amphetamine; (b) preoperative open field activity in females; (c) the induction of hyperactivity following right neocortical ablation in males; (d) rotational responses to amphetamine in male rats sustaining bilateral ablations; and (e) the effect of left neocortical ablation on prolactin levels in males. We propose that these data provide new evidence for distinct patterns of brain organization in rats differentiated by a measure of inherent cerebral laterality.