Contingent negative variation, extraversion, reaction time and drug effects

The effect of caffeine and chlordiazepoxide on contingent negative variation (CNV) and on reaction time (RT) was investigated in 44 healthy naive volunteers, in relation to various psychological tests. Early CNV is characterised by a significant interaction between drug effects and extraversion, boredom susceptibility, disinhibition and strength of excitation. Caffeine increased early CNV amplitude for those with high scores and decreased it at low scores. Chlordiazepoxide had the opposite effect. Placebo effect was negligible. At modal scores there was no appreciable difference between either drug and placebo. In consecutive sessions early CNV decreased. Early CNV was not correlated with RT. In contrast, there were no significant drug effects on late CNV or on RT, either with or without an interaction with extraversion. Late CNV showed a strong negative correlation with RT but early CNV had a positive effect on this relationship. RT was also negatively correlated with extraversion. Late CNV was stable over sessions. Only for early CNV the results support the hypothesis that simulation by caffeine would cause a CNV decrease at low scores and an increase at high scores, whereas inhibition by chlordiazepoxide would have the opposite effect.