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 performance 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).