Psychedelic drugs and perception: a narrative review of the first era of research
Aday, J. S., Bloesch, E. K., Davoli, C. C., Wood, J. R.
This historic review (2021) examines a series of studies conducted in the first and second eras of psychedelic research which examine the perceptual effects of psychedelic drugs and highlights certain commonalities, such as a shared interest in the perception of music. While most studies investigated how psychedelics affect vision across every level of visual processing (e.g., retinal, cortical, subcortical, low-level visual processing, complex visual imagery), other studies investigated its effect on auditory discrimination, the neural correlates of auditory processing, and auditory hallucinations restricted to a subset of participants. Some studies also demonstrated that psychedelics can distort representations of body schema, time perception, taste, olfaction, and synesthesia, but these areas still remain understudied.
Abstract
Psychedelic drugs are well-known for transiently altering perception, and in particular, for their visual effects. Although scientific interest into the substances' effects on perception increased during the first era of psychedelic research during the early to mid-20th century, there is currently no source where these findings have been synthesized. In addressing this gap, the current narrative review found that psychedelics were examined for their influences across all levels of the visual system (e.g., retinal, cortical, subcortical, simple visual processing, complex imagery, hallucinations). Psychedelics were also shown to affect auditory discrimination/generalization, neural correlates of auditory processing, and led to auditory hallucinations in subsets of participants. Several studies demonstrated that psychedelics can distort representations of body schema and time perception. Concerns regarding methodological standards of this era are a limitation to the findings and are discussed. Collectively, this review preserves and increases the accessibility of the work done by pioneering psychedelic/perception researchers, synthesizes findings, and critically analyzes areas of discrepancy to inform future studies.