Blood flow and cerebral laterality in the mescaline model of psychosis.

The psychological, neuropsychological, and neurometabolic effects of the hallucinogenic agent mescaline were investigated in 12 normal male volunteers. Between 3 1/2 and 4 hours after drug intake, mescaline produced an acute psychotomimetic state, as measured by the BPRS and PDS-P. The APZ questionnaire revealed the specific effects of mescaline in the visual system. Neuropsychological effects were studied with a face/non-face decision task with known right hemisphere advantage, in which mescaline induced a decrease in functioning of the right hemisphere. In functional brain imaging using SPECT, mescaline produced a "hyperfrontal" pattern with an emphasis on the right hemisphere, which was correlated with mescaline-induced psychotomimetic psychopathology. Our findings question the validity of the concept of hypofrontality as an explanation for acute psychotic symptomatology.