Effects of bromazepam on single-trial event-related potentials in a visual vigilance task

Thirty females performed a visual vigilance task under the influence of bromazepam (6 and 12 mg) in a placebo-controlled, double blind, experiment. Measures employed were percentage of hits, percentage of false alarms, response latency (RT), A' (sensitivity), B" (cautiousness), and RI (responsivity), as well as signal- and non-signal event-related potentials (ERPs). Bromazepam did not aggravate the normally occurring decrement in performance in vigilance tasks, but had an effect on overall level of performance: accuracy was reduced under the influence of the drug, but speed improved. A Drug x Period interaction for cautiousness (B") indicated increasingly less cautiousness with bromazepam, which probably contributed to faster motor responses (and more errors) than in the placebo group. The ERP data suggest that the effects of bromazepam are already manifest in the early stages of information processing (attention-detection) as mirrored by a drug effect on N1 amplitude. Deterioration at this early stage may affect later processing stages (P2-N2 amplitudes). As a result, subjects under the influence of the drug probably accumulate less signal evidence for their final evaluation.