Looking for the Self: Phenomenology, Neurophysiology and Philosophical Significance of Drug-induced Ego Dissolution

High doses of hallucinogenic drugs can produce a profound alteration of self-experience known as drug-induced ego dissolution (DIED), where the sense of self dissolves and boundaries between self and world disappear. Three classes of drugs induce this: classical psychedelics, dissociative anesthetics, and kappa opioid receptor agonists. Neuroimaging of DIED may reveal neural correlates of the self, but results must be interpreted cautiously—they may show necessary but not sufficient conditions for selfhood. The phenomenon likely disrupts the minimal or embodied self, a basic sense of self rooted in multimodal sensory integration, consistent with Bayesian models of phenomenal selfhood. DIED challenges philosophical views that consciousness always involves self-awareness and suggests ordinary experience includes a minimal self-awareness that fades during ego dissolution.

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Abstract

There is converging evidence that high doses of hallucinogenic drugs can produce significant alterations of self-experience, described as the dissolution of the sense of self and the loss of boundaries between self and world. This article discusses the relevance of this phenomenon, known as "drug-induced ego dissolution (DIED)", for cognitive neuroscience, psychology and philosophy of mind. Data from self-report questionnaires suggest that three neuropharmacological classes of drugs can induce ego dissolution: classical psychedelics, dissociative anesthetics and agonists of the kappa opioid receptor (KOR). While these substances act on different neurotransmitter receptors, they all produce strong subjective effects that can be compared to the symptoms of acute psychosis, including ego dissolution. It has been suggested that neuroimaging of DIED can indirectly shed light on the neural correlates of the self. While this line of inquiry is promising, its results must be interpreted with caution. First, neural correlates of ego dissolution might reveal the necessary neurophysiological conditions for the maintenance of the sense of self, but it is more doubtful that this method can reveal its minimally sufficient conditions. Second, it is necessary to define the relevant notion of self at play in the phenomenon of DIED. This article suggests that DIED consists in the disruption of subpersonal processes underlying the "minimal" or "embodied" self, i.e., the basic experience of being a self rooted in multimodal integration of self-related stimuli. This hypothesis is consistent with Bayesian models of phenomenal selfhood, according to which the subjective structure of conscious experience ultimately results from the optimization of predictions in perception and action. Finally, it is argued that DIED is also of particular interest for philosophy of mind. On the one hand, it challenges theories according to which consciousness always involves self-awareness. On the other hand, it suggests that ordinary conscious experience might involve a minimal kind of self-awareness rooted in multisensory processing, which is what appears to fade away during DIED.