Spectral signatures of serotonergic psychedelics and glutamatergic dissociatives

Pallavicini, Carla; Vilas, Martina G.; Villarreal, Mirta F.; Zamberlán, Federico; Muthukumaraswamy, Suresh; Nutt, David; Carhart‐Harris, Robin; Tagliazucchi, Enzo

doi:10.1016/j.neuroimage.2019.06.053

Cited by 44 publications

(37 citation statements)

References 71 publications

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“…This assertion is supported by the lack of congruency between previous EEG and MEG findings during the psychedelic state and the results of the current study. Past studies have demonstrated widespread decreases in broadband power (35)(36)(37)(38)(39)(40), with an emphasis on decreases in the alpha band that correlate with the degree of subjective effects (13,39,41,42). Given our results demonstrating an overlap in reported changes in experience during the shamanic state of consciousness and the psychedelic state, it is surprising that shamanic practitioners not only lacked changes in alpha power, but experienced increases in power isolated to the gamma band that correlated with the degree of elementary visual alterations.…”

Section: Shamanic Practitioners Enter An Altered State Of Consciousnesupporting

confidence: 47%

Neural correlates of the shamanic state of consciousness

Huels

Kim

Lee

et al. 2020

Preprint

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Despite the use of shamanism as a healing practice for several millennia, few empirical studies of the shamanic state of consciousness exist. We investigated the neural correlates of shamanic trance using high-density electroencephalography (EEG) in 24 shamanic practitioners and 24 healthy controls during rest, shamanic drumming, and classical music listening, followed by a validated assessment of altered states of consciousness. EEG data were used to assess changes in absolute power, connectivity, signal diversity, and criticality, which were correlated with assessment measures. We also compared assessment scores to those of individuals in a previous study under the influence of psychedelics. Shamanic practitioners were significantly different from controls in several domains of altered states of consciousness, with scores comparable to or exceeding that of healthy volunteers under the influence of psychedelics. Practitioners also displayed increased gamma power during drumming that positively correlated with elementary visual alterations. Furthermore, shamanic practitioners had decreased low alpha and increased low beta connectivity during drumming and classical music, and decreased neural signal diversity in the gamma band during drumming that inversely correlated with insightfulness. Finally, criticality in practitioners was increased during drumming in the low and high beta and gamma bands, with increases in the low beta band correlating with complex imagery and elementary visual alterations. These findings suggest that psychedelic drug-induced and non-pharmacologic alterations in consciousness have overlapping phenomenal traits but are distinct states of consciousness, as reflected by the unique brain-related changes during shamanic trance compared to previous literature investigating the psychedelic state.

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Section: Shamanic Practitioners Enter An Altered State Of Consciousnesupporting

confidence: 47%

Neural correlates of the shamanic state of consciousness

Huels

Kim

Lee

et al. 2020

Preprint

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“…We first identified a substantial reduction in broadband spectral power in the psychedelic state. This is a relatively well established effect, which has been described in several previous studies: see, e.g., Fink (1969) Pallavicini et al (2019) analysed spectral changes in LSD, psilocybin and ketamine using the same MEG dataset as used in this study. They report region-specific patterns of spectral power reduction in the alpha and theta bands common to LSD and psilocybin, as well as changes in the beta band common to all three drugs.…”

Section: Power Spectramentioning

confidence: 66%

“…Existing functional analyses of the psychedelic state (Riba et al, 2004;Muthukumaraswamy et al, 2013;Carhart-Harris et al, 2016;Pallavicini et al, 2019) have concentrated on changes in spectral power (Section 3.1). We therefore wondered whether the decreased directed functional connectivity we observed might have a straightforward explanation in terms of changes in spectral power.…”

Section: Spectral Power and Signal-to-noise Ratiomentioning

confidence: 99%

“…However, unlike the present study, this previous study did not analyse connectivity of any kind. Other EEG and MEG studies (Kometer et al, 2015;Alonso et al, 2015;Rivolta et al, 2015;Pallavicini et al, 2019) have applied FC measures, but did not systematically compare directed and undirected measures, and did not compare results across a range of psychedelics (see Introduction).…”

Section: Functional Connectivity and Signal Variabilitymentioning

confidence: 99%

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Decreased Directed Functional Connectivity in the Psychedelic State

Barnett

Muthukumaraswamy

Carhart‐Harris

et al. 2019

Preprint

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Neuroimaging studies of the psychedelic state offer a unique window onto the neural basis of conscious perception and selfhood. Despite well understood pharmacological mechanisms of action, the largescale changes in neural dynamics induced by psychedelic compounds remain poorly understood. Using source-localised, steady-state MEG recordings, we describe changes in functional connectivity following the controlled administration of LSD, psilocybin and low-dose ketamine, as well as, for comparison, the (non-psychedelic) anticonvulsant drug tiagabine. We compare both undirected and directed measures of functional connectivity between placebo and drug conditions. We observe a general decrease in directed functional connectivity for all three psychedelics, as measured by Granger causality, throughout the brain. These data support the view that the psychedelic state involves a breakdown in patterns of functional organisation or information flow in the brain. In the case of LSD, the decrease in directed functional connectivity is coupled with an increase in undirected functional connectivity, which we measure using correlation and coherence. This surprising opposite movement of directed and undirected measures is of more general interest for functional connectivity analyses, which we interpret using analytical modelling. Overall, our results uncover the neural dynamics of information flow in the psychedelic state, and highlight the importance of comparing multiple measures of functional connectivity when analysing time-resolved neuroimaging data.

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“…Synchronization of population dynamics across large cortical distances has been explored in vivo through spectral analysis in various human and animal studies: at anaesthetic doses, increased gamma oscillations in cortico-subcortical networks may result from an altered interplay between cortical pyramidal neurons and parvalbumin-expressing interneurons (Lazarewicz et al 2010;Slovik et al 2017;Grent-'t-Jong et al 2018;Qi et al 2018). Others found differential effects on neuronal oscillations with decreased large-scale beta band activity at both subanaesthetic (Ma et al 2018;Pallavicini et al 2019) and anaesthetic doses (Hertle et al 2016), and increased theta and decreased alpha EEG (Bojak et al 2013;Blain-Moraes et al 2014). One caveat of current studies comparing cortical processing between anaesthetic and awake states is that they mainly focus on single or multi-unit level data, or on the macroscopic EEG signal in human research.…”

Section: Introductionmentioning

confidence: 99%

Ketamine anaesthesia induces gain enhancement via recurrent excitation in granular input layers of the auditory cortex

Deane

Brunk

Curran

et al. 2020

The Journal of Physiology

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Ketamine is a common anaesthetic agent used in research and more recently as medication in treatment of depression. It has known effects on inhibition of interneurons and cortical stimulus-locked responses, but the underlying functional network mechanisms are still elusive. r Analysing population activity across all layers within the auditory cortex, we found that doses of this anaesthetic induce a stronger activation and stimulus-locked response to pure-tone stimuli. r This cortical response is driven by gain enhancement of thalamocortical input processing selectively within granular layers due to an increased recurrent excitation. r Time-frequency analysis indicates a higher broadband magnitude response and prolonged phase coherence in granular layers, possibly pointing to disinhibition of this recurrent excitation. r These results further the understanding of ketamine's functional mechanisms, which will improve the ability to interpret physiological studies moving from anaesthetized to awake paradigms and may lead to the development of better ketamine-based depression treatments with lower side effects.

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Spectral signatures of serotonergic psychedelics and glutamatergic dissociatives

Cited by 44 publications

References 71 publications

Neural correlates of the shamanic state of consciousness

Neural correlates of the shamanic state of consciousness

Decreased Directed Functional Connectivity in the Psychedelic State

Ketamine anaesthesia induces gain enhancement via recurrent excitation in granular input layers of the auditory cortex

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