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About this resource
This is an English version of a 2015 fMRI study examining how resting-state brain activity and functional connectivity changed during an acute ayahuasca-induced altered state of consciousness. Ten healthy adults with ayahuasca experience were scanned before ingestion and during acute effects. The focus was the default mode network (DMN), which is often associated with internally directed thought and self-related processing.
Finding a difference in brain imaging does not mean that the cause of a particular experience or clinical effect has been proved. The fMRI BOLD signal is an indirect measure related to blood flow and oxygenation, not a device that reads subjective experience itself. This study had no placebo control and was an acute pre/post comparison in 10 people.
Study design
Participants underwent resting-state fMRI at baseline before ingestion and during the acute phase after receiving research ayahuasca. Researchers conducted analyses related to cerebral blood flow and BOLD, comparing activity in major DMN regions, functional connectivity within the network, and relationships with other regions. Subjective-effect scales were also used, and their correspondence with imaging changes was explored.
Comparing the same people before and after reduces between-person variation, but without a placebo condition it cannot separate the effects of elapsed time, repeated scanning, expectations, the scanner environment, or head motion. Selecting experienced participants may help reduce anxiety and motion during scanning, while limiting generalization to people without prior experience.
Content
The DMN is studied as a network of multiple regions that coordinate when attention is not focused on an external task. The posterior cingulate cortex or precuneus and the medial prefrontal cortex are treated as major nodes. Because previous psychedelic research had reported changes in activity and connectivity in this network, the authors examined whether ayahuasca showed a similar pattern.
The analyses reported decreased activity in major DMN nodes and reduced connectivity within parts of the network. Changes in connectivity centered particularly on the posterior cingulate cortex were shown. Because visible patterns can vary with analytical methods and thresholds, however, it would be inaccurate to simplify the results as “the DMN stopped” or “the ego disappeared.”
The authors discussed possible relationships with self-related processing, internally directed thought, and changes in the subjective sense of self. These are interpretations linking the imaging findings to earlier research, not results that measured the specific content of each participant’s thoughts. Later research has also shown network-connectivity changes with other psychoactive effects and shifts in arousal, so DMN changes may not be unique to ayahuasca.
Results
During the acute phase, activity measures decreased in several DMN regions, and reduced within-network connectivity including the posterior cingulate cortex was observed. The study showed that the acute ayahuasca state alters measurements associated with the ordinary organization of resting-state networks. Although small, it is positioned as an early neuroimaging resource focused on ayahuasca.
The study did not examine improvement in symptoms such as depression. It cannot support conclusions that lower DMN activity is healthier, reduced connectivity is a therapeutic mechanism, or subjective insight has been proved neuroscientifically. Acute correlational findings and long-term clinical outcomes are different research questions.
Limitations
The sample of 10 participants was very small, with no placebo control, randomization, or independent replication sample. Because acute effects are strong, expectations and psychological state cannot be controlled. Head motion and vascular effects can influence fMRI signals. Studies addressing multiple brain regions and analytical measures must also consider chance differences and the effects of analytical choices.
Results in healthy experienced participants do not represent patients with psychiatric illness, first-time participants, different ages or physical conditions, or different brews. A pre/post difference alone cannot separate contributions from DMT, β-carbolines, expectations, and setting.
Network-analysis results may change depending on how the brain is divided into regions, which frequency bands and preprocessing procedures are used, and how head motion is corrected. Outliers also have a large effect in a small sample. The published spatial patterns are statistical images derived from measurements and analytical procedures in these 10 people, not brain markers suitable for individual diagnosis.
Safety
The imaging study screened participants and observed them under supervision during the acute phase. Even if serious events were not prominent in a small study, it lacks power to assess rare psychiatric or cardiovascular risks and drug interactions. Tolerability in the unusual environment of a scanner also cannot be generalized to ordinary settings.
Neuroimaging changes should not be used as evidence of health benefit or safety. This page does not show how to reproduce an altered state or provide instructions for use, and imaging findings should not be substituted directly for clinical judgment.
Participants who could be scanned during acute altered consciousness were experienced people able to adapt to the procedure. The course of people unable to complete scanning because of anxiety, claustrophobic reactions, vomiting, movement, or other factors is less likely to appear. Successful image acquisition does not amount to a comprehensive assessment of physical or psychiatric safety.
The term DMN does not refer to a single psychological function; it denotes a statistical pattern of coordination among multiple regions. Reduced activity cannot be read as “reduced brain function,” nor can reduced connectivity automatically be read as “improved flexibility.” The meaning of imaging findings must be judged through accumulated control conditions, behavioral measures, and replication studies.
Even if acute neuroimaging correlates with psychological scales weeks later, that does not prove a mediating causal pathway. This study is not a completed account of therapeutic mechanisms; it is an exploratory foundational resource showing a candidate phenomenon that can be measured.
Source and rights
Original source: Palhano-Fontes F, et al. The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network. PLOS ONE. 2015;10(2):e0118143. DOI: 10.1371/journal.pone.0118143.
The original article is published under a Creative Commons Attribution license. This page is a source-aligned English translation under that license, reconstructed to distinguish observed neuroimaging results from the authors’ interpretations. Images, figures, and tables are not reproduced.