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Biomedical subjects

G M Heyman

Publications and source records attributed to G M Heyman.

24 records · Page 2Linked to original sources
PubMed1983

A parametric evaluation of the hedonic and motoric effects of drugs: pimozide and amphetamine.

This study uses a curve-fitting approach to evaluate the effects of drugs on reinforced responding in rats. The subjects obtained reinforcement according to a series of five different variable-interval schedules (a five-component multiple schedule). For each rat, pimozide, a neuroleptic, decreased response rate, and the decrease was associated with (1) a decrease in the estimated asymptotic response rate and (2) an increase in the rate of reinforcement necessary for half-asymptotic responding. That is, pimozide decreased the proportion of responding maintained by a given rate of reinforcement. In contrast, intermediate doses of amphetamine increased response rate and increased the proportion of responding maintained by a given rate of reinforcement. It was proposed that the response rate asymptote indexes motor capacity, and the rate of reinforcement necessary for half-asymptotic responding indexes reinforcement efficacy; accordingly, pimozide decreased motor capacity and reinforcement strength and amphetamine increased reinforcement strength.

Animals↗
PubMed1980

Context dependent changes in the reinforcing strength of schedule-induced drinking.

Previous experiments show that the opportunity to engage in schedule-induced responding is reinforcing. In this experiment, the reinforcing strength of schedule-induced drinking was measured. Four rats were trained on a concurrent-chain schedule. The two terminal links provided food pellets on identical fixed-time schedules. In addition, one terminal link also provided the opportunity to press a button that operated a water dipper. In this link, the rats showed polydipsic drinking. Button-pressing rate for polydipsic drinking was a bitonic function of pellet rate, and it was possible to describe the relationship with a slightly modified version of the matching equation for primary reinforcement. This equation also closely fit the data from other studies. Initial-link response rates, however, did not appear to be influenced by the availability of water in the terminal links. Control conditions suggested that the reinforcing strength of polydipsia was strongly bound to the context provided by periodic food reinforcement.

Animals↗
PubMed1979

Is matching compatible with reinforcement maximization on concurrent variable interval variable ratio?

Four pigeons on concurrent variable interval, variable ratio approximated the matching relationship with biases toward the variable interval when time spent responding was the measure of behavior and toward the variable ratio when frequency of pecking was the measure of behavior. The local rates of responding were consistently higher on the variable ratio, even when there was overall preference for the variable interval. Matching on concurrent variable interval, variable ratio was shown to be incompatible with maximization of total reinforcement, given the observed local rates of responding and rates of alternation between the schedules. Furthermore, it was shown that the subjects were losing reinforcements at a rate of about 60 per hour by matching rather than maximizing.

Journal Article↗
PubMed1979

A Markov model description of changeover probabilities on concurrent variable-interval schedules.

The primary data were peck-by-peck sequential records of four pigeons responding on several different concurrent variable-interval schedules. According to the hypothesis that the subject chooses the alternative with the highest probability of reinforcement at the moment, response-by-response performance in concurrent schedules should show sequential dependencies. However, such dependencies were not found, and it was possible to describe molecular-level performance with simple Markov chain models. The Markov model description implies that the momentary changeover probabilities were proportional to the overall relative reinforcement frequencies, and that changeover probabilities did not change as a function of previous responding. A second finding was that although a changeover-delay procedure was omitted, relative response frequencies closely approximated relative reinforcement frequencies.

Journal Article↗
PubMedDate not supplied

Chronic morphine consumption decreases wheel running and wheel running-reinforced behavior in rats.

The purpose of this experiment was to evaluate the effects of morphine self-administration on wheel running and wheel running-reinforced lever pressing in rats. The home cage was equipped with a bottle that contained either water, a saccharin-flavored 0.5-mg/ml morphine solution, or saccharin (0.25%). The bottle was available for either 1 or 3 h. The bottle was then removed, and 20-22 h after removal, the rats were moved to an operant chamber in which lever presses earned 15 s access to a running wheel (according to a variable interval (VI) 40-s schedule). The morphine condition was in effect for 69 days, and consumption gradually increased to a level of 67 mg/kg/day. During the morphine condition, wheel running and lever pressing decreased. Following the removal of morphine, (so that the home-cage bottles provided a 0.25% saccharin solution), the two instrumental behaviors increased to the pre-morphine (water) levels. However, the increases were not immediate, and in the first post-morphine session, lever pressing and wheel turning remained at the depressed morphine level. The post-morphine increase in lever pressing was substantially larger than the increase in wheel running. The results support the hypothesis that chronic opiate consumption reduces the frequency of some nondrug-related behaviors, and that this, in turn, increases preference for the opiate.

Animals↗