The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network
PLoS ONE – February 18, 2015
Source: OpenAlex
Summary
A powerful hallucinogen, Ayahuasca, significantly reduces activity in the brain's default mode network (DMN), a key area for mind-wandering and consciousness. Using functional magnetic resonance imaging (resting state fMRI) on ten experienced subjects, neuroscience revealed decreased activity in regions like the Posterior Cingulate and Precuneus. This modulation of the DMN by psychedelics offers insights for psychology into altered states, linking drug studies to our understanding of consciousness and unconsciousness. This informs neurotransmitter receptor influence on behavior, relevant to tryptophan and brain disorders.
Abstract
The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regions more active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity through most parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. Altogether, our results support the notion that the altered state of consciousness induced by Ayahuasca, like those induced by psilocybin (another serotonergic psychedelic), meditation and sleep, is linked to the modulation of the activity and the connectivity of the DMN.