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

By Robin L. Carhart-Harris, Robert Leech, Peter J Hellyer, Murray Shanahan, A. Feilding, Enzo Tagliazucchi, Dante R. Chialvo, David J. Nutt. Frontiers in Human Neuroscience, 2014

1,084 citations recorded by the source corpus.

Entropy is a dimensionless quantity that is used for measuring uncertainty about the state of a system but it can also imply physical qualities, where high entropy is synonymous with high disorder. Entropy is applied here in the context of states of consciousness and their associated neurodynamics, with a particular focus on the psychedelic state. The psychedelic state is considered an exemplar of a primitive or primary state of consciousness that preceded the development of modern, adult, human, normal waking consciousness. Based on neuroimaging data with psilocybin, a classic psychedelic drug, it is argued that the defining feature of “primary states” is elevated entropy in certain aspects of brain function, such as the repertoire of functional connectivity motifs that form and fragment across time. Indeed, since there is a greater repertoire of connectivity motifs in the psychedelic state than in normal waking consciousness, this implies that primary states may exhibit “criticality,” i.e., the property of being poised at a “critical” point in a transition zone between order and disorder where certain phenomena such as power-law scaling appear. Moreover, if primary states are critical, then this suggests that entropy is suppressed in normal waking consciousness, meaning that the brain operates just below criticality. It is argued that this entropy suppression furnishes normal waking consciousness with a constrained quality and associated metacognitive functions, including reality-testing and self-awareness. It is also proposed that entry into primary states depends on a collapse of the normally highly organized activity within the default-mode network (DMN) and a decoupling between the DMN and the medial temporal lobes (which are normally significantly coupled). These hypotheses can be tested by examining brain activity and associated cognition in other candidate primary states such as rapid eye movement (REM) sleep and early psychosis and comparing these with non-primary states such as normal waking consciousness and the anaesthetized state.

Subfields: Clinical Psychology, Cognitive Neuroscience, Experimental and Cognitive Psychology

View Paper: https://www.semanticscholar.org/paper/e414fc2efa0b64905c7e1378f0ee3b8ca4c2430f

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Citations in the corpus

Rapid and sustained symptom reduction following psilocybin treatment for anxiety and depression in patients with life-threatening cancer: a randomized controlled trial (2016, background): “The former is significant because depressive symptoms have been associated with increased activity in the medial PFC (Drevets et al., 2008; Farb et al., 2011) and normalization of medial PFC activity has been demonstrated with anti-depressant treatment (Deakin et al., 2008; Holtzheimer and Mayberg, ”
Quality of Acute Psychedelic Experience Predicts Therapeutic Efficacy of Psilocybin for Treatment-Resistant Depression (2018, background): “…the pharmacological to the whole-brain systems level, increased cortical entropy has been found to be a reliable feature of the psychedelic state (Carhart-Harris et al., 2014), to relate to high-level subjective experiences such as “ego-dissolution” (Nour et al., 2016; Atasoy et al., 2017;…”
Neural correlates of the LSD experience revealed by multimodal neuroimaging (2016, background): “Consistent with a prior hypothesis (17), these studies suggest that an “entropic” effect on cortical activity is a key characteristic of the psychedelic state.”
Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial (2016, background): “As a 5-HT2A agonist, the psilocybin metabolite psilocin directly and indirectly affects various brain cortical and subcortical areas and alters brain network dynamics (Carhart-Harris et al., 2012, 2014; Vollenweider and Kometer, 2010).”
Pilot Study of the 5-HT2AR Agonist Psilocybin in the Treatment of Tobacco Addiction (2014, background): “Several plausible mechanisms of hallucinogen-facilitated treatments have been proposed (Bogenschutz and Pommy, 2012; Carhart-Harris et al., 2012, 2014; Ross, 2012; Vollenweider and Kometer, 2010).”
REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics (2019, background): “2014 (Carhart-Harris et al., 2014) and later revisited and updated in”
The spectral exponent of the resting EEG indexes the presence of consciousness during unresponsiveness induced by propofol, xenon, and ketamine (2019, positive): “This idea is supported by theoretical work (Carhart-Harris et al., 2014; Pearlmutter and Houghton, 2009), and by multiple lines of experimental evidence (Priesemann et al., 2014; Hahn et al., 2017).”
Serotonin and brain function: a tale of two receptors (2017, background): “Moreover, a recent LSD neuroimaging study by our team found that acute ‘entropic’ brain changes under the drug (Carhart-Harris et al., 2014b) were predictive of long-term increases in the personality trait ‘openness’ (Lebedev et al., 2016).”
Mapping the self in the brain's default mode network (2016, positive): “, 2008; Tomasi and Volkow, 2011; Leech and Sharp, 2014), likely acts as the central conduit through which temporal and parietal cortical representations of self are made accessible to prefrontal cortical reflective systems; with a unitary notion of self defined by the large-scale integration of the ”