The effects of nitrous oxide on P300 and reaction time.

This experiment investigated the effects of 3 concentrations (15%, 25% and 35%) of nitrous oxide (N2O) on reaction time (RT) and P300 latency and amplitude. Ten subjects responded to visually presented male or female names in an oddball paradigm with accuracy controlled at a high level. The results were analysed on a single-trial basis. Nitrous oxide increased both RT and P300 latency in a dose-related manner and these variables showed a strong between-dose correlation (r = 0.67). Nitrous oxide also decreased P300 amplitude but only up to the 25% dose. The between-dose correlation for P300 amplitude and RT was negligible (r = -0.14). These results suggest that P300 latency is an index of N2O narcosis and are interpreted as indicating that narcosis involves the slowing of stimulus evaluation processes.