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

Papo, David

doi:10.3389/fnhum.2016.00423

Cited by 12 publications

(13 citation statements)

References 32 publications

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“…In one study, the authors suggested that enhanced priors, mediated by over-activation of deep layers, generated the subjective effects associated with psychedelics (Muthukumaraswamy et al, 2013), while in another study, the same effects were associated with impaired bottom-up processing (combined with intact top-down processing) mediated by enhanced AMPA signalling (Corlett et al, 2009). The present account also appears compatible with another contemporary theory of psychedelics, the entropic brain theory (EBT) (Carhart-Harris, 2018;Carhart-Harris et al, 2014;Carhart-Harris and Friston, 2019). EBT suggests that psychedelics increase the entropy of brain activity, rendering it more chaotic and susceptible to intrinsic and extrinsic influences, while psychedelics also increase connectivity between resting-state (and task-positive) brain networks, in agreement with the enhanced integration induced by descending loops (Carhart-Harris et al, 2016;De Araujo et al, 2012).…”

Section: Discussionsupporting

confidence: 79%

From hallucinations to synaesthesia: a circular inference account of unimodal and multimodal erroneous percepts in clinical and drug-induced psychosis

Leptourgos¹,

Bouttier²,

Jardri³

2021

Preprint

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Psychedelics are known to distort perception and induce visual and multimodal hallucinations as well as synaesthesia. This is in contradiction with the high prevalence of distressing voices in schizophrenia. Here we introduce a unifying account of unimodal and multimodal erroneous percepts based on circular inference. We show that amplification of top-down predictions (descending loops) leads to an excessive reliance on priors and aberrant levels of integration of the sensory representations, resulting in crossmodal percepts and stronger illusions. By contrast, amplification of bottom-up information (ascending loops) results in overinterpretation of unreliable sensory inputs and high levels of segregation between sensory modalities, bringing about unimodal hallucinations and reduced vulnerability to illusions. We delineate a canonical microcircuit in which layer-specific inhibition controls the propagation of information across hierarchical levels: inhibitory interneurons in the deep layers exert control over priors, removing descending loops. Conversely, inhibition in the supragranular layers counterbalances the effects of the ascending loops. Overall, we put forward a multiscale and transnosographic account of psychosis with important theoretical, conceptual and clinical implications.

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Section: Discussionsupporting

confidence: 79%

From hallucinations to synaesthesia: a circular inference account of unimodal and multimodal erroneous percepts in clinical and drug-induced psychosis

Leptourgos¹,

Bouttier²,

Jardri³

2021

Preprint

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“…Intriguingly, MEG and EEG signal diversity was elevated in psychedelic states induced by LSD, psilocybin, DMT, and subanesthetic doses of ketamine, in line with reports of increased range and intensity of conscious contents in psychedelic states, and has even been found to correlate with some subjective ratings of psychedelic phenomenology (Schartner et al, 2017a;Timmermann et al, 2019;Farnes et al, 2020). Hence, signal diversity (of a system) may be a correlate of consciousness and richness of subjective experience (supported by that system), at least under certain conditions and within a limited range, as suggested by complexity theories such as IIT and Carhart-Harris' speculative entropic brain hypothesis (Marshall et al, 2016;Tononi et al, 2016;Carhart-Harris, 2018) [but see Papo (2016)].…”

Section: Introductionmentioning

confidence: 99%

EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience

et al. 2021

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Several theories link consciousness to complex cortical dynamics, as suggested by comparison of brain signal diversity between conscious states and states where consciousness is lost or reduced. In particular, Lempel-Ziv complexity, amplitude coalition entropy and synchrony coalition entropy distinguish wakefulness and REM sleep from deep sleep and anesthesia, and are elevated in psychedelic states, reported to increase the range and vividness of conscious contents. Some studies have even found correlations between complexity measures and facets of self-reported experience. As suggested by integrated information theory and the entropic brain hypothesis, measures of differentiation and signal diversity may therefore be measurable correlates of consciousness and phenomenological richness. Inspired by these ideas, we tested three hypotheses about EEG signal diversity related to sleep and dreaming. First, diversity should decrease with successively deeper stages of non-REM sleep. Second, signal diversity within the same sleep stage should be higher for periods of dreaming vs. non-dreaming. Third, specific aspects of dream contents should correlate with signal diversity in corresponding cortical regions. We employed a repeated awakening paradigm in sleep deprived healthy volunteers, with immediate dream report and rating of dream content along a thought-perceptual axis, from exclusively thought-like to exclusively perceptual. Generalized linear mixed models were used to assess how signal diversity varied with sleep stage, dreaming and thought-perceptual rating. Signal diversity decreased with sleep depth, but was not significantly different between dreaming and non-dreaming, even though there was a significant positive correlation between Lempel-Ziv complexity of EEG recorded over the posterior cortex and thought-perceptual ratings of dream contents.

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“…Desynchronized default mode network (DMN) activity, increased hippocampal BOLD signal variance (i.e., amplitude fluctuations), and DMN-hippocampal decoupling under psilocybin may reduce constrained cognition and thus allow for more possible states (Carhart-Harris et al, 2014). Increased excitatory connection from the thalamus to the posterior cingulate cortex (PCC)…”

Section: Neurophenomenology Of Psychedelic Substances and Effects On The (Bodily) Selfmentioning

confidence: 99%

“…Post-psilocybin (Carhart-Harris et al, 2012;Lewis et al, 2017) and DMT (Palhano-Fontes et al, 2015) decreases in both global cerebral blood flow and BOLD signal of high-association hubs along cortical midline structures evidence a reduced connectivity of associative networks, particularly in the DMN (Buckner, Andrews-Hanna, & Schacter, 2008); a large-scale intrinsic network that is activated during rest, deep meditative states (Brewer et al, 2011) and metacognitive operations such as introspection and memory retrieval (Qin & Northoff, 2011). It has been suggested that the anticorrelated temporal dynamics of the DMN-TPN during normal wakefulness could reflect the self-reflection and processing necessary to distinguish between self and others, whereas a disintegration of this negative network coupling during the psychedelic state may underlie the perceived feelings of unity and ego dissolution (Carhart-Harris et al, 2014;Millière, 2017). More specifically, dissolution of the self, or general self-referential processing following LSD administration seem to be reflected by altered resting-state connectivity of the PCC, including the retrosplenial cortex , and disintegration of the SN (Lebedev et al, 2015).…”

Section: Disintegration Of the Embodied Pre-reflective Selfmentioning

confidence: 99%

“…The primary connections of the DMN extend to the thalamus, PCC, and MPFC, as well as to the information integration systems of the brain (i.e., parahippocampal cortex and hippocampus) (Raichle, 2015). Interruption of the sensory gating from cortico-striato-thalamo-cortical loops increases the availability of information normally repressed by these systems to reach high-level association areas (Vollenweider & Geyer, 2001;Winkelman, 2017) through a disruption of normal rhythmic oscillations of excitatory cortical neurons at 5-HT2A receptors (Carhart-Harris et al, 2014). Increased serotonergic activation by psychedelics reduces effective connectivity from the ventral striatum to the thalamus, opening the thalamic filter and thereby decreasing information gating, while increasing bottom-up information flow to certain cortical areas (Preller et al, 2019).…”

Section: Readaptation Of the Narrative Selfmentioning

confidence: 99%

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Neuropharmacological modulation of the aberrant bodily self through psychedelics

Preller

Lenggenhager

2020

Neuroscience & Biobehavioral Reviews

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As a continual source of sensory input and fundamental component of self-referential processing, the body holds an integral modulatory role in cognition. In a healthy state, predictive coding of multisensory integration promotes the construction of a coherent self. However, several psychiatric disorders comprise aberrant perceptions of the bodily self that are purported to involve discrepancies in the integration and updating of multisensory systems. Changes in functional connectivity of somatomotor and high-level association networks in these disorders could be successfully remediated through 5-HT2A receptor agonism via psychedelics. Reported alterations of bodily self-awareness during psychedelic experiences allude to a potentially central role of the bodily self. In this article, we bridge the domains of (aberrant) bodily self-awareness and psychedelics by discussing the predictive coding mechanisms underlying the bodily self and psychedelics. Furthermore, we propose that psychedelically-induced desynchronization of predictive coding might involve modulation of somatomotor, sensorimotor, and high-level association networks that could remediate aberrant perceptions of the bodily self.

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

Cited by 12 publications

References 32 publications

From hallucinations to synaesthesia: a circular inference account of unimodal and multimodal erroneous percepts in clinical and drug-induced psychosis

From hallucinations to synaesthesia: a circular inference account of unimodal and multimodal erroneous percepts in clinical and drug-induced psychosis

EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience

Neuropharmacological modulation of the aberrant bodily self through psychedelics

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