The effects of septal lesions on second-order schedules

Abstract

Seven Long-Evans albino rats with septal lesions and five control rats were trained on a fixed-interval 60-sec schedule of reinforcement for 25 sessions, followed by a second-order schedule of reinforcement. The second-order schedule consisted of a fixed-interval 60-sec component maintained by a variable-interval 180-sec schedule. Each fixed interval completed before the variable-interval schedule was satisfied produced a 0.3- or 8-sec brief stimulus, while each fixed interval completed after the variable-interval schedule was satisfied produced a brief stimulus that terminated with food. Septal and control rats exhibited the same response rates and patterning on the simple fixed-interval 60-sec schedule. Under the second-order schedule septal rats had the highest response rate under the 0.3-sec stimulus, and the best temporal patterning with the 8-sec stimulus. The data suggest that animals with septal lesions can inhibit responding as well as controls but tend to respond at a higher rate when inhibitory constraints are removed.