Classic psychedelics like N, N-Dimethyltryptamine (DMT) have a tremendous effect on perception, cognition, and self-experience. Recent studies suggest that these substances can reveal fundamental principles of brain function. According to one theoretical framework, the brain generally operates near critically an optimal balance between order and disorder that supports long-range temporal correlations (LRTC), efficient information processing, and maintenance of a coherent sense of self. Deviations from this criticality, reflected in changes to the temporal structure of neural oscillations, may play an important role in both altered states of consciousness and disruptions of self-related processing.
The present study aimed to quantify how DMT affects neural criticality and excitatory/inhibitory (E/I) dynamics in human electroencephalography (EEG) recordings and to assess whether these neural changes are associated with the subjective experience of self-dissolution, a hallmark of high-dose psychedelic states.
EEG data were combined from two single blind, placebo-controlled studies, which involved 27 healthy adults who received intravenous DMT (7 to 20 mg) and a placebo on separate visits. Participants were carefully screened for psychiatric and medical contraindications. EEG was recorded from 31 scalp electrodes at baseline and for 20 minutes after a 1.5-30 second DMT infusion. Participants completed visual analogue scales to assess changes in time perception, selfhood, space, cognition, and overall experimental intensity after the acute effects subsided. EEG data were pre-processed to remove artifacts using visual inspection and independent component analysis.
The primary neural measures were obtained by Detrended Fluctuation Analysis (DFA) to quantify LRTC in the narrow-band amplitude envelopes. Higher DFA exponents reflect more temporally structured, pink-noise-like dynamics, reflecting proximity to criticality. The functional excitatory/inhibitory ratio (fE/I) was computed by a sliding window method, which correlates oscillatory amplitude with the temporal structure of fluctuations. It is used to determine the direction of any criticality shift toward subcritical (inhibition-dominated) or supercritical (excitation-dominated) regimes, but it is only computed for windows with reliable LRTC (DFA > 0.6). Statistical comparisons between DMT and placebo conditions were performed using paired sample t-tests, and correlations with subjective ratings were calculated using Pearson’s r with false-discovery-rate correction.
Results showed that DMT induced a significant reduction in DFA exponents across theta, alpha, and beta frequency bands (ΔDFA = –0.06 to –0.09), with effects widespread across the scalp. These reductions indicate weakening of long-range temporal structure and a shift away from criticality. This reflects lower signal complexity and higher entropy consistent with a move toward white-noise-like dynamics. The fE/I metric was assessed and showed significant decreases in alpha band, specifically in parietal and occipital regions, and a smaller reduction in occipital beta, attributable to reduced DFA, which can increase during subcritical and supercritical transitions.
These findings indicate that observed departure from criticality occurred specifically in a subcritical direction, which means neural activity became more inhibition-dominated and less capable of sustaining long-time scale temporal dependencies. Reductions in DFA in theta and alpha bands correlated strongly with participants’ ratings of ego dissolution. This suggests a temporally extended sense of self during the psychedelic state.
This study provides novel evidence that DMT induces widespread shifts in the temporal organization of brain activity, reducing the complexity of neural oscillations and pushing alpha and adjacent frequency bands into subcritical regimes. These results suggest that weakened LRTC in alpha-mediated networks may serve as a neural marker for disruptions in self-related processing observed across various altered states, including psychedelics, meditation, and anaesthesia. Moreover, the findings reconcile reports of increased entropy under psychedelics with a more nuanced, frequency-specific account of criticality. Overall, this study sheds light on the neural mechanisms underlying ego dissolution and enhances our understanding of how psychedelics modify brain dynamics.
Reference: Timmermann C, Aqil M, Irrmischer M, et al. DMT-induced shifts in criticality correlate with self-dissolution. J Neurosci. 2025:e0344252025. doi:10.1523/JNEUROSCI.0344-25.2025
