Repeated Acquisition Task Research Articles

Intravenous diazepam in humans: Effects on acquisition and performance of response chains

A technique based upon an individual-subject design was used to investigate the effects of intravenous diazepam on the acquisition and performance of response chains in humans. In each of two conditions subjects were required to emit a different sequence of ten responses in a predetermined order on three levers. The conditions alternated within each session under a multiple schedule. In the performance condition the sequence of responses was the same each session. The second condition was a repeated-acquisition task. In this condition subjects were required to learn a different sequence of responses each session. Diazepam produced dose-dependent decreases in the overall rate of responding in each subject under both conditions. In two of the three subjects tested, errors were increased in the learning condition at doses lower than those required to disrupt accuracy in the performace condition. In one subject, accuracy in both the learning and performance conditions was equisensitive to the disruptive effects of diazepam. These data are consistent with the effects of the benzodiazepines in analogous animal procedures. Furthermore, the data suggest that the behavioral effects of intravenous diazepam may exhibit marked variations across subjects at clinically relevant doses (5–10 mg).

Phencyclidine in combination with pentobarbital: Supra-additive effects on complex operant behavior in pigeons

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. The response chain was maintained by food presentation under afixed ration schedule. Errors produced a brief timeout but did not reset the chain. When phencyclidine was administered alone, the overall response rate decreased and the percent errors increased with increasing doses. Similar effects were found with a high dose of pentobarbital alone. When phencyclidine was administered in combination with pentobarbital dose-effect curves for rate and accuracy shifted to the left as the dose of pentrobarbital was increased. Cobinations of phencyclidine with a high dose of pentobarbital produced supra-additive effects;i.e., the effects on rate and accuracy were greater than expected from simple addition of the effects of each drug given alone. These results extend the generality of previous findings in patas monkeys in a similar repeated-acquisition task.

Effects of Dextroamphetamine Sulfate on Repeated Acquisition Behavior and Mood in Humans: A Preliminary Report

The specific aim of the present investigation was the systematic assessment of the effects of nontoxic doses of orally administered dextroamphetamine sulfate on the learning behavior maintained by the repeated acquisition task in humans. Subjects were four healthy male humans ranging in age from 23 to 29 years. The participants reported to the experimental setting at a specified time for the duration of the experiment. Following assessment of physiologic parameters, subjects received either anhydrous dextrose placebo or 5, 10, or 15 milligrams (mg) dextroamphetamine sulfate. Two hours after drug administration participants returned to the experimental area where they completed two repeated acquisition sequences and two self-report scales—49 items from the Addiction Research Center Inventory and the 72-item Profile of Mood States. The 2-hour interval between drug administration and subsequent behavioral testing was necessary for assessment of peak drug effect. Learning of the behavioral chains of the repeated acquisition task, using light position as a discriminative stimulus, was characterized by a decrease in errors and an increase in response rate which was maximal at a dose of 10 mg drug. Subjective measure of drug effect on four mood clusters of the Profile of Mood States and five subscales of the Addiction Research Center Inventory demonstrated primarily a dose-related function.

Effects of phencyclidine, pentobarbital, and d-amphetamine on the acquisition and performance of conditional discriminations in monkeys.

In each of two components of a multiple schedule, monkeys were required to respond on a right or left lever depending upon the stimulus combination (a color and a geometric form) presented. Reinforcement of a response in the presence of one stimulus (the form) was therefore conditioned upon the other stimulus (the color). The completion of a two-member chain of discriminations produced a food pellet. Errors produced a brief timeout. One composition of the multiple schedule was a repeated-acquisition task where the discriminative stimuli for left- or right-lever responses changed each session (learning). In the other component, the discriminative stimuli for left- or right-lever responses were the same each session (performance). Phencyclidine, pentobarbital, and d-amphetamine each produced dose-related decreases in the overall rate of responding in both components of the multiple schedule. At high doses each drug increased the percent errors in each component. At lower doses, however, the three drugs produced selective effects on accuracy. Errors were increased in the learning component at lower doses than those required to disrupt the discrimination in the performance component. A signal detection analysis of the data revealed that none of the drugs tested increased errors by selectively affecting either discriminability or bias.

Effects of d-amphetamine, cocaine, and phencyclidine on the acquisition of response sequences with and without stimulus fading.

In each of three components of a multiple schedule, monkeys were required to emit a different sequence of four responses in a predetermined order on four levers. Sequence completions produced food on a fixed-ratio schedule. Errors produced a brief timeout. One component of the multiple schedule was a repeated-acquisition task where the four-response sequence changed each session (learning). The second component of the multiple schedule was also a repeated-acquisition task, but acquisition was supported through the use of a stimulus-fading procedure (faded learning). In a third component of the multiple schedule, the sequence of responses remained the same from session to session (performance). At higher doses, d-amphetamine, cocaine, and phencyclidine decreased the overall rate of responding and increased the percent errors in all three components. At lower doses, however, the three drugs produced selective effects on errors. Errors were increased in the learning component at lower doses than those required to disrupt the behavior in the faded-learning component. The performance component tended to be the least sensitive to disruptive drug effects. The data are consistent with the view that stimulus fading can modulate the effects of drugs on acquisition.

Effects of d-amphetamine and cocaine on strained ratio behavior in a repeated-acquisition task.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. When the fixed-ratio requirement for food presentation was five completions of the chain, d-amphetamine and cocaine disrupted the behavior. As the dose of each drug was increased, the overall response rate decreased, the overall accuracy was impaired (i,e., percent errors increased), and there was less within-session error reduction (acquisition). In contrast, when the fixed-ratio requirement was either 20 or 50 completions of the chain, certain doses of both drugs produced large increases in the overall response rate by eliminating the extended pausing (ratio strain) that was characteristic of the control sessions. These rate-increasing effects were accompanied by error-decreasing effects, both during acquisition and after the response chain had been acquired. Taken together, the results show that the effects of d-amphetamine and cocaine on behavior in a repeated-acquisition task can be modulated by manipulating the value of the fixed-ratio schedule maintaining the behavior.