Electrically elicited behavior in the rat : sources of reinforcement

The eating, drinking and gnawing behavior induced by electrical stimulation of the lateral hypothalamus (ESLH) in rats was studied in order to assess the role of reinforcement in controlling the behavior. In the first study, an attempt was made to modify the initial stimulus-bound behavior to emerge by giving the animal previous experience with the drinking response in the presence of ESLH. The results showed that a contiguous relationship between a 30-second train of ESLH and the performance of a drinking response was not sufficient to modify the type of stimulus-bound behavior to initially emerge . A second set of experiments examined the role of ESLH as a reinforcer in stimulus-bound behavior by allowing animals in a shuttle apparatus to choose between various stimulation conditions and no stimulation. The results indicated that most animals had a slight preference for long durations of ESLH. In the final experiment stimulus-bound animals were trained to bar press for 3 second trains of ESLH that would elicit the stimulus-bound response. The bar press rate was then measured with the appropriate goal object present where the animal could perform the consummatory response and in a situation without the goal object present whare the animal could not make the response. Stimulus -bound gnawers, as well as eaters and drinkers, all bar pressed more when they could perform the consummatory response, hence supporting the notion that the performance of the response is reinforcing in electrically induced behavior. This research supported an interpretation which suggests that the behaviors elicited by ESLH are maintained by reinforcement arising from the incentive qualities of the goal object, the ESLH itself, and the performance of the response. It was suggested that future research should explore the ESLH as a reinforcer in stimulus -bound animals under conditions that maximize the strength of the reinforcement (ie. where the animals regulate the rate and duration of the stimulation) .