Effect of septal lesions on behavioral contrast

Abstract

Rats with septal lesions and control animals were tested on a multiple schedule. When extinction was instituted in one component of the multiple schedule, septal-lesioned and control animals exhibited approximately equal amounts of positive contrast in the unaltered component. The results were discussed in terms of the situation specificity of the enhanced reaction to nonreward associated with septal damage.The response of the septal-Iesioned animal to withdrawal or omission of reinforcement has been the subject of a n!)mber of investigations (e.g., Butters & Rosvold , 1968;Caplan, 1970;Schwartzbaum, Kellicut, Spieth, & Thompson, 1964). It has generally been found that onusslon of reinforcement is followed by accelerated responding or increased perseveration in the septal-Iesioned animal above control levels. Caplan (1970) found, for example, that when scheduled reinforcement was omitted on a DRL schedule all subjects accelerated their response rates, but the increase was greatest for septal-Iesioned animals. Mabry and Peeler (1972) found, however, that animals with septal lesions and control animals did not differ in response to frustrative nonreward in a double-runway task. Both groups increased running speed and starting speed following omission of reinforcement, but there was no difference in the magnitude of alterations in running speed and starting latency for the two groups of animals.The present study attempted to determine whether the operant nature of the task or some other factor is critical to the observation of an exaggerated response to nonreinforcement in the septal-Iesioned rat. In two experiments, responses of septal-Iesioned and control animals were compared during the formation of a successive discrimination in an operant situation. All animals were initially placed on a multiple schedule in which different schedules of reinforcement were in effect for successive components. Each component was associated with a distinctive cue. After response rates stabilized on a multiple VI VI (MULT VI VI), extinction was instituted in one component (MULT VI EXT). Septal-Iesioned and control animals were compared on behavioral contrast-an increase in response rates in the unaltered VI component. EXPERIMENT I MethodAnimals. Ten Long-Evans male rats seIVed as subjects. Their ages ranged from 120 to ISO days at the beginning of the study. During the course of the study they were housed in individual cages.Apparatus. Training occurred in Lehigh Valley operant chambers placed in sound-atknuating cubicles. A white-noise generator minimized the extraneous sounds. Electromechanical programming and recording apparatus was located in an adjacent room. A 7-W houselight powered by 20-V ac served to differentiate multiple schedule component~ SUIgery and histology. Prior to any operant trai,ning, five animals received bilateral lesions of the septal region, three served as operated controls, and two served as unoperated controls. The operated animals were anesthetized with ~ ium pentobarbital (60 mg/kg) and positioned ,i...

Effects of intrahippocampal administration of colchicine on incentive contrast and on radial maze performance.

“…In addition to these studies on contrast in consummatory behavior, there have been a few studies of the effects of lesions on contrast obtained in instrumental tasks. The results obtained with damage to the septum are consistent with those obtained in the consummatory contrast paradigm; that is, septal lesions do not interfere with negative contrast obtained with decreases of food reward in runways (Hammond & Thomas, 1971), nor do they interfere with behavioral contrast obtained in operant tasks (Davison, Lowther, & Allen, 1975;Dickinson, 1972;Henke, 1976). The results obtained with amygdala damage are also consistent with the consummatory contrast data in that such lesions reduce the degree of behavioral contrast (Henke, 1972;Henke, Allen, & Davison, 1972) and, in general, reduce the animals' sensitivity to changes in reinforcement value (Schwartzbaum, 1960).…”