DISCRIMINATING THE EFFECTS OF TRIAZOLAM ON STIMULUS AND RESPONSE PROCESSING BY MEANS OF REACTION-TIME AND P300 LATENCY

The benzodiazepines slow information processing and the sites of this slowing were mapped using the Additive Factors Method in combination with the P300 component of the event-related brain potential. It was assumed that P300 largely reflects the time to evaluate a stimulus while reaction time (RT) reflects this time plus the time to select and execute a response. Twelve subjects were administered 0.25 mg triazolam in a repeated measures single-blind design. A visual 80-20% oddball task was used in which stimulus intensity and signal quality were manipulated with accuracy of responding held constant at a high level. RT and EEG data were collected simultaneously and the P300 elicited by the low probability stimuli was measured on a single trial basis. Triazolam slowed RT (172 ms, P<0.0003) more than P300 (88 ms, P<0.0007), but both measures exhibited a drug x stimulus intensity interaction. RT also exhibited a drug x signal quality interaction but P300 did not. These results suggest that triazolam has selective effects on perceptual processing by slowing an early preprocessing stage but not a later feature extraction stage. In addition, the drug appears to slow some aspect of response processing. This evidence is taken as support for a multiple process rather than general sedation view of benzodiazepine effects on stages of processing.