DMT-induced shifts in criticality correlate with self-dissolution

Irrmischer and colleagues situate their work in the context of classic psychedelics, which reliably alter both subjective experience and brain dynamics. They focus on DMT, described as a classic psychedelic that powerfully disrupts ordinary consciousness and can produce intense visual imagery and changes in self-experience. The authors are particularly interested in “self-dissolution” or “ego-dissolution” – a temporary breakdown of the usual coherent sense of being a bounded self, often described with items such as “I experienced a disintegration of my self or ego”. They note that such experiences are increasingly thought to be relevant for the therapeutic and scientific importance of psychedelics.

The core theoretical construct in this paper is “criticality” in brain dynamics. A system is said to operate at criticality when it sits at a tipping point between order and disorder, such that fluctuations occur across many spatial and temporal scales. In this regime, activity is highly structured yet flexible, and the system shows “long-range temporal correlations” (LRTC) – the idea that what happens now is influenced by what happened many seconds before. Brain oscillations recorded with EEG appear to show such near-critical dynamics in healthy waking states. Moving away from criticality – either towards overly ordered, sluggish dynamics (subcritical) or overly unstable, runaway dynamics (supercritical) – is thought to reduce information-processing capacity. The authors highlight evidence that LRTC and critical dynamics are modulated by sleep, anaesthesia, meditation and attention, suggesting that changes in criticality may track different states of consciousness.

The paper builds on two key metrics. First, the authors use detrended fluctuation analysis (DFA) to quantify LRTC. DFA estimates a scaling exponent between 0.5 and 1. A value near 0.5 resembles “white noise” (very random, no memory), indicating a system far from criticality; a value near 1 resembles “pink noise” (1/f spectrum), indicating stronger long-range correlations and dynamics closer to criticality. Second, they use a “functional excitatory/inhibitory ratio” (fE/I), a summary measure derived from how the amplitude and temporal structure of oscillations co-vary over time. This metric distinguishes whether a system is in a subcritical (inhibition-dominated) state, a critical state, or a supercritical (excitation-dominated) state. Irrmischer and colleagues aim to determine how DMT changes these markers of criticality in different frequency bands, and how such changes relate specifically to subjective reports of self-dissolution.

Methods

Participants and experimental design