Reward, performance, and the response strength method in self-stimulating rats: validation and neuroleptics

The response strength method consists of exposing the subject to a series of variable interval schedules of reinforcement at differing densities. Response rate is plotted against obtained reinforcement rate for each schedule. The data conform to a negatively accelerated curve that is fit well by an analytical representation which contains two parameters. The values of these parameters are obtained from the fitted curve, and are suggested to independently reflect reinforcement and performance functions. In a first experiment, two manipulations were conducted that validated these suggestions. First, lowering the frequency of brain stimulation pulses induced a relatively selective shift in the reinforcement parameter. Second, increasing the force required to press the lever primarily altered the performance parameter. In a second experiment, the effects of neuroleptic administration on these two parameters were noted and compared to the results of the first experiment. In general, neuroleptics were seen to produce both reward and motor/performance impairments in self-stimulating rats.