Satiation effects in continuous reinforcement and successive sensory discrimination situations

Abstract

Nine rats with forebrain and hypothalamic electrodes were trained on a sensory discrimination task with S-intervals ranging from 12 to 60 sec. Their performance during a 48-h discrimination session was compared to that during a 48-h CRF session. The response measures showed that forebrain Ss performed more poorly than hypothalamic Ss during the discrimination session, even though performance of forebrain animals was better in the discrimination session than in the CRF session when time until the fust 5-min pause was considered. In the CRF session, there was no difference in performance of forebrain and hypothalamic animals, except in terms of time till fust pause. The results are discussed in terms of cumulative effects of forebrain and hypothalamic ESB.Studies dealing with behavior reinforced by rewarding electrical stimulation of the brain (ESB) show differences in behavior as a function of electrode placement. For example, in an operant situation with the animals responding on a continuous reinforcement schedule (CRF), there are differences in the short-term response rate depending on whether the electrode is in the forebrain or in the lateral hypothalamus. Olds (1958), comparing the performance of hypothalamic and forebrain Ss over the course of a 48-h session with ESB available on a CRF schedule, found that animals with forebrain electrodes responded more slowly after 4 to 8 h, whereas hypothalamic Ss responded at.a high steady rate for longer periods of time, until overcome by "physical exhaustion." aids also found that hypothalamic Ss returned, during at least 1 h of the second day of the prolonged session, to their original high rates of responding, but that forebrain animals did not return to their initial rates. One possible explanation of the data on short-term rate is that the forebrain ESB differs from the hypothalamic ESB in that it more readily produces seizures or some other kind of interfering side effect. The satiation effect would need the additional assumption that the forebrain ESB produces a cumulative or long-term increase in the frequency of these side effects. It would follow from this analysis that if the frequency or intensity of the interfering side effects could be reduced by some experimental manipulation, then the differences between the forebrain and the hypothalamic animals could be reduced. With respect to the question of short-term rate, Reid, Gibson, Gledhill, and Porter (I964) found that the administration of an *This research was supported in part by a United States Mental Health grant to Dr. G. Frommer, Indiana University, Bloomington, Indiana, and a National Research Council of Canada grant to I. Lenzer. The authors are grateful to Dr. G. Frommer for financial assistance and for suggestions during the early stages of the experiment.anticonvulsant drug and the consequent elevation of the seizure threshold had the effect of increasing the response rate of animals responding for forebrain ESB, to levels more nearly comparable to those displayed by hypothalamic animals. With r...