P300 and traffic scenes: the effect of temazepam.

The present research investigated the effects of a minor tranquillizer (temazepam) on P300 in a paradigm that may be relevant for traffic behaviour. Because accident scenes have not been used previously in P300 research, Experiment 1 (n = 8) examined whether the P300 elicited by safe traffic scenes and scenes of imminent road accidents were sensitive to the probability of occurrence. Event-related potentials were recorded from C3, Cz, C4, P3, Pz and P4 within an oddball paradigm. The type of stimulus to which subjects responded (pictures of imminent accidents or safe road scenes) was crossed with the probability (0.1 or 0.5) of the relevant (to which a response was required) event. The results indicated that P300 amplitude increased with decreasing probability of the relevant stimulus and that P300 was most pronounced at Pz. Experiment 2 (n = 12) employed a drug treatment (10 mg temazepam) and a placebo treatment (100 mg Vitamin E). An oddball paradigm with a probability of the relevant stimulus of 0.1 was used and P300 was recorded from Cz, C3, C4, Pz, P3 and P4. Generally, the ingestion of temazepam decreased P300 amplitude and increased P300 latency at all sites. Reaction time, on the other hand, was not influenced by drug administration. The data demonstrate the clear effect of minor tranquillizers on the psychological processes associated with P300.