Influence of neonatal septal lesions on DRL performance in adulthood

Two experiments are reported describing the influence of neonatal septal lesions on responding of rats trained on a differential-reinforcement-of-low-rate (DRL) schedule in adulthood. Rats given septal lesions at 1 day or at 7 days after birth emitted a significantly higher number of responses and earned fewer reinforcements than did animals given control electrode insertions. Thus, the inefficient performance on the DRL schedule, often observed after septal lesions in adulthood, does not depend upon the age of the animal at the time of the lesion. Furthermore, operant training given at an early age (25-45 days) to animals with neonatal septal damage did not facilitate performance when the animals were retrained in adulthood. In short, septal lesions at any age lead to permanent impairments of performance on a DRL 20-sec reinforcement schedule.