Decortication of rats in infancy or adulthood produced comparable functional losses on learned and species-typical behaviors.

Rats with complete ablation of the neocortex at 1--8 days of age were compared behaviorally with rats with similar excisions at 120 days of age. Decortication at both ages produced (a) chronic deficits in feeding behaviors indicated by chronic reduction in body weight, chronic deficits in pattern of food ingestion, and abolition of food-hoarding behavior; (b) increased general activity as measured in running wheels; (c) several chronic abnormalities in grooming behavior; (d) chronic abnormalities in paddling during swimming; (e) abolition of male sexual behavior; (f) elimination of defensive burying of a shock prod; and (g) severe impairments in the acquisition of a spatial reversal task. In sum, complete removal of the neocortex in infancy does not allow convincing sparing of function, a result demonstrating that subcortical structures are unable to take over functions of the neocortex. Thus, sparing of function reported following subtotal decortication requires neocortical circuitry, either alone or in combination with subcortical structures.