Effects of the Amazonian Psychoactive BeverageAyahuascaon Binocular Rivalry: Interhemispheric Switching or Interhemispheric Fusion?

Ingesting the South American hallucinogenic beverage ayahuasca reduced the rate of perceptual alternations in a binocular rivalry task, increased the duration of one percept, and produced evidence of phenomenal fusion. These findings align with brain activation studies showing right cortical activation under hallucinogens and support the concept of interhemispheric fusion in altered states of consciousness, rather than the earlier theory of changes in hemispheric integration.

Study at a glance

Abstract

An early theoretical analysis supposed changes in hemispheric integration as the basis of altered state of consciousness induced by psychoactive drugs. Brain imaging studies revealed right cortical activation after administration of hallucinogens. Recent studies on binocular rivalry suggest that interhemispheric switching is the neural substrate of the perceptual oscillations observed during dichoptic stimulus presentation. The current study tested perceptual alternation in ceremonial participants, who ingested the South American hallucinogenic beverage ayahuasca, to examine the claim that there might be changes in interhemispheric function under the influence of hallucinogens. Ingestion of ayahuasca resulted in a decrease of rivalry alternation rates, increased length of one percept and there was evidence of phenomenal fusion. The findings are in line with results of brain activation studies and support the concept of interhemispheric fusion in altered states of consciousness.