Retention of delayed-alternation: effect of selective lesions of sulcus principalis.

Monkeys with bilateral lesions of the anterior, miiddle, or posterior thirds of the principal sulcus, of the periarcuate prefrontal region, or of the inferior parietal lobule were tested for retention of spatial delayed-alternation. Lesions limited to the middle third of sulcus principalis resulted in failure to relearn delayedalternation within 1000 trials; lesions elsewhere had little effect.