The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs

"In the present context, the “metastability” (Tognoli and Kelso, 2014) of a brain network is a measure of the variance in the network’s intrinsic synchrony over time. That is, if the signal in all of the voxels within a given network deviates little from the network’s mean signal, then variance is low, whereas if the signal in voxels fluctuate erratically, then variance is high."

INCREASED NETWORK ENTROPY IN THE PSYCHEDELIC STATE, p. 10

They operationalize metastability as variance of intra-network synchrony and use it to quantify how psychedelic states move brain dynamics toward higher variability consistent with critical-like emergent dynamics .

"Results revealed significantly increased network variance in high-level association networks after psilocybin but not in sensory specific and motor networks, and there were no changes after placebo. These results imply that activity in high-level networks becomes relatively disorganized under psilocybin, consistent with the entropic brain hypothesis."

INCREASED NETWORK ENTROPY IN THE PSYCHEDELIC STATE, p. 10

Empirical fMRI evidence shows selective increases in variance in association networks under psilocybin, supporting a shift toward more entropic, globally flexible dynamics relevant to consciousness state changes .

Figures

Fig. 6 (p. 11) : Figure 6 visualizes increased metastability and entropy after psilocybin, indicating more chaotic network behavior—a hallmark of emergent dynamics near criticality in altered conscious states .

"For example, intracranial recordings from the ventral PCC in humans revealed a dominant presence of theta oscillations. The phase of these oscillations modulate the amplitude of high-gamma oscillations and the magnitude of this coupling fluctuates at a frequency that is consistent with that of spontaneous BOLD signal fluctuations (i.e., ∼0.1 Hz) observed in resting-state networks (RSNs) such as the DMN."

THE DEFAULT MODE NETWORK AND THE EGO, p. 8

This establishes a temporal coordination mechanism—phase-amplitude coupling in PCC—that tracks resting-state timescales, linking local oscillatory timing to large-scale DMN dynamics relevant to content binding and segmentation in conscious processing .

"it was remarkable that we recently found a highly significant positive correlation between the magnitude of alpha power decreases in the PCC after psilocybin and ratings of the item “I experienced a disintegration of my ‘self ’ or ‘ego’.”"

THE DEFAULT MODE NETWORK AND THE EGO, p. 8

A report-linked neural signature (PCC alpha power decrease) tracks subjective ego-dissolution, tying metacognitive/self-model processes to measurable neural changes during altered consciousness .

Figures

Fig. 4 (p. 8) : Figure 4 summarizes the correlation between PCC alpha reductions and self-report of ego-disintegration, linking neural oscillatory changes to reportable self-model alterations .

"In the next section we cite direct evidence for increased entropy in brain networks in psychedelic state and use this to support a general principle: that the transition from normal waking consciousness to primary consciousness is marked by an increase in system entropy."

INCREASED NETWORK ENTROPY IN THE PSYCHEDELIC STATE, p. 10

They explicitly frame the psychedelic shift as a state transition characterized by increased entropy, aligning with metastable switching between processing regimes in consciousness research .

Figures

Fig. 3 (p. 8) : Figure 3 shows a time-locked change in hippocampal variance following infusion, consistent with an induced transition into a new dynamical regime .