Behavioral effects of sequential and one-stage ablations of orbital prefrontal cortex in the monkey.

The purpose of this investigation was to determine whether sequential (i.e., serial) ablation of the monkey’s orbital prefrontal cortex would lead to a reduction in the severity of the behavioral impairment usually associated with one-stage bilateral removal of this tissue. The lateral orbital cortex was ablated in four operations spaced 3 weeks apart or in a one-stage procedure. The monkeys were examined on a visual go-no go differentiation task, spatial delayed-alternation, and object reversal learning. The results reveal no differences between the effects of sequential and one-stage ablations. These findings differ from previous experiments that demonstrated a degree of functional recovery after the sequential removal of a sector of the dorsolateral prefrontal cortex. Since lesion studies with infant monkeys have also demonstrated that functional recovery occurs after early ablation of dorsolateral cortex but not after early removal of orbital frontal cortex, recovery of behavioral functions after infant and sequential lesions may involve similar neural mechanisms.