Psychoactive drug-induced changes of interhemispheric EEG amplitude relationships

Analyses of the EEG amplitude levels (integrative method) in the right (R) and left (L) occipital areas of human subjects reveal that there exists in most subjects a R/L difference, and that certain psychoactive drugs can change the relationships which prevail under normal conditions (lateralization). Stimulants tend to decrease interhemispheric differences while, on the contrary, following drug-induced euphoria, these differences are increased. Hallucinogens can reverse lateralization; neuroleptics produce a decrease in the variability of amplitude ratios. Sedatives, minor tranquillizers and placebo are without effect. With hallucinogenic drugs, changes similar to those occurring in man have also been obtained in rabbits.A preliminary communication of these results was presented at the Fifth International Congress of Pharmacology (San Francisco, USA, July 1972).