In the present study we addressed the question whether, within the isocortex, the prefrontal area of the rat is uniquely involved in mediation of delayed alternation. In one group of rats the dorsolateral isocortex, from the dorsomedial shoulder to the dorsal lip of the rhinal sulcus was removed bilaterally in a single surgical session. In these rats delayed alternation in a T-maze was significantly less impaired than in rats with one stage bilateral removal of the medial prefrontal cortex. The prefrontal cortex seems not to depend crucially on isocortical input for its medication of delayed alternation.