Psychedelics and the science of self-experience

This short editorial (2017) describes the recent emergence of a neuroscience of self-experience and its relationship to psychoactive drugs and psychiatry.

Abstract

“Altered self-experiences arise in certain psychiatric conditions, and may be induced by psychoactive drugs and spiritual/religious practices. Recently, a neuroscience of self-experience has begun to crystallise, drawing upon findings from functional neuroimaging and altered states of consciousness occasioned by psychedelic drugs. This advance may be of great importance for psychiatry.”

Authors: Matthew M. Nour & Robin L. Carhart-Harris

Summary

Defining the self

The experience of a coherent and well-circumscribed ‘self’ is a cardinal feature of human waking consciousness. It is distinguished from a narrative self, which is a cognitive theoretical construct, and a minimal self, which is an immediate aspect of experience.

Self in neuroscience

The neuronal correlates of self have been investigated using tasks that measure increased activity in cortical midline brain regions during processing of self-specific stimuli, compared with stimuli related to others. The brain regions implicated in self-processing show anatomical overlap with important nodes of the default mode network.

Studies of self-attribution to physical and mental features are not well suited to identify neuronal correlates of minimal self-experience, but theoretical considerations suggest that the neuronal mechanisms underlying mismatch minimisation may be a good candidate.

Self-disturbance

Distortions of self-experience are a central feature of a number of altered states of consciousness, such as the psychedelic state and the mystical experience. Abnormalities of self-consciousness have also been described in a number of mental health conditions, such as schizophrenia.

Individuals with depression show abnormal activity in the perigenual anterior cingulate cortex, and both schizophrenia and depression are characterised by abnormal DMN resting-state activity.

Psychedelics as a window into the self

Psychedelic drugs perturb self-consciousness and occasion ego-dissolution experiences. These experiences are correlated with decreased integrity of important resting-state brain networks associated with the sense of self, as well as decreased segregation between these and other brain networks.

Recent studies have shown that ego-dissolution experiences occasioned by psilocybin and LSD correlate with decreased alpha power in the posterior cingulate cortex, increased whole-brain integration, and inversely correlated with DMN network integrity, functional connectivity between the parahippocampus and retrosplenial cortex, and oscillatory power in the delta and alpha frequency bands.

Therapeutic implications

Recent studies suggest that psychedelic drugs can improve anxiety, addiction and mood disorders when given in controlled therapeutic environments. The precise mechanism by which psychedelics can occasion positive and lasting changes in mood, attitudes and behaviours is deserving of further investigation.

Previous work has established that psilocybin-induced mystical experiences are associated with well-being, openness and meaningfulness. However, further research is required to adequately test this link.

Conclusions

Psychedelic drugs can occasion transient and dose-dependent reductions in the normally well-circumscribed experience of self, providing a valuable tool for investigating the neuronal correlates of normal and abnormal self-experience.