Dose-dependent modulation of visual imagery by Ayahuasca and dampening of visual processing away from external input: a placebo-controlled pharmacoimaging study
Miguel Castelo-Branco, Anna Gaidosch, Marta Teixeira, Gisela Lima, Carla Soares, Marta Pais, Patrícia Rijo, Célia Cabral, Goebel Rainer
preprint DOI: 10.21203/rs.3.rs-11114520/v1 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Placebo-controlled within-subject fMRI study |
|---|---|
| Sample size | 11 |
| Population | 11 participants receiving ayahuasca and placebo in a within-subject design |
| Intervention | Ayahuasca |
| Dose | multiple doses of Ayahuasca; high-dose condition specified |
| Topics | Ayahuasca |
| Key points | High-dose ayahuasca attenuated strong stimulus-evoked activation in ventral visual regions and reduced stimulus-evoked deactivation in the precuneus, while early visual cortex responses remained unaffected. Ayahuasca also decreased de-coupling between early visual cortex and a midline associative region spanning cuneal cortex and precuneus. The authors argue these findings support the view that ayahuasca biases visual processing away from externally driven input toward internally oriented processing, consistent with predictive coding and the REBUS model. |
Abstract
Abstract Ayahuasca, an amazonian brew containing the serotonergic psychedelic substance N,N-dimethyltryptamine (DMT), induces distinctive visual perceptual phenomenology, yet the neural mechanisms underlying the interplay between external visual drive and internal imagery remain unknown. Using a placebo-controlled, within-subject fMRI design, the present study investigated the impact of multiple doses of Ayahuasca upon strong bottom-up visual drive using high contrast periodic dynamic stimuli processing in 11 participants. Subjective ratings indicated psychedelic effects regarding visual perception and imagery, with dose-dependent increases in simple and complex visual imagery and intensity ratings. At the neural level, high-dose Ayahuasca attenuated this strong stimulus-evoked activation in ventral visual regions and reduced stimulus-evoked deactivation in the precuneus, while early visual cortex responses remained unaffected at this high stimulus drive level. Functional connectivity analyses revealed that Ayahuasca decreased the de-coupling between early visual cortex and a midline associative region, spanning the cuneal cortex and precuneus. These findings support the view that Ayahuasca biases visual processing away from externally driven input toward internally oriented processing, consistent with predictive coding and the REBUS model of psychedelic action.
Comparable studies
Other randomized controlled trials on ayahuasca, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Rapid antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression: a randomized placebo-controlled trial Patients with treatment-resistant depression | 2018 | Randomized controlled trial | n = 29 |
| Human Pharmacology of Ayahuasca: Subjective and Cardiovascular Effects, Monoamine Metabolite Excretion, and Pharmacokinetics Volunteers with prior experience in the use of psychedelics | 2003 | Double-blind placebo-controlled clinical trial | n = 18 |
| Subjective effects and tolerability of the South American psychoactive beverage Ayahuasca in healthy volunteers Healthy male volunteers with prior experience using ayahuasca | 2001 | Single-blind crossover placebo-controlled clinical trial | n = 6 |
| Increased frontal and paralimbic activation following ayahuasca, the pan-amazonian inebriant Male volunteers with prior experience in the use of psychedelics | 2006 | Randomized controlled trial | n = 15 |
| Human brain effects of DMT assessed via EEG-fMRI. Healthy volunteers | 2023 | Within-subjects, placebo-controlled design | n = 20 |