Chlorpromazine and the lateralisation of the perception of emotion.

In a double-blind design, sixteen volunteer students were administered 50 mg of chlorpromazine or a placebo in tablet form on separate occasions, two hours prior to testing. The test was a lexical decision paradigm involving unilateral presentation of pairs of neutral, positive and negative emotional words and nonwords to the left or right visual fields. Reaction time to identify words and nonwords was recorded. Neutral stimuli were processed faster in the left hemisphere, while negative stimuli were processed faster in the right hemisphere. Chlorpromazine improved speed of response for neutral stimuli presented to the right hemisphere and for affective stimuli presented to the left hemisphere. Thus chlorpromazine seems to benefit right hemisphere processing of nonaffective stimuli and benefit left hemisphere processing of affective stimuli. Chlorpromazine appeared to have a different impact on neutral and affective words, and on the right and the left hemispheres. The general effect of chlorpromazine was to reduce lateralisation. It was suggested that this occurred because chlorpromazine blocked dopamine and possibly other neurotransmitters.