Effects of external stimulation on psychedelic state neurodynamics

Mediano, Pedro A. M.; Rosas, Fernando; Timmermann, C; Roseman, Leor; Nutt, David; Feilding, Amanda; Kaelen, Mendel; Kringelbach, Morten L.; Barrett, Adam B.; Seth, Anil K.; Muthukumaraswamy, Suresh; Bor, Daniel; Carhart‐Harris, Robin

doi:10.1101/2020.11.01.356071

Cited by 38 publications

(87 citation statements)

References 58 publications

(80 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent findings by Mediano et al (2020) provide strong quantitative evidence on how environmental conditions have a substantial influence on neural dynamics during a psychedelic experience in humans. This work showed how brain entropy is modulated by stimulus manipulation during a psychedelic experience by studying participants under the effects of LSD or placebo, either with gross state changes (eyes closed vs. open) or different stimulus (no stimulus vs. music vs. video).…”

Section: Discussionmentioning

confidence: 99%

Ketamine and sleep modulate neural complexity dynamics in cats

Pascovich

Castro-Zaballa

Mediano

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

There is increasing evidence that level of consciousness can be captured by neural informational complexity: for instance, complexity, as measured by the Lempel Ziv (LZ) compression algorithm, decreases during anesthesia and non-rapid eye movement (NREM) sleep in humans and rats, when compared to LZ in awake and REM sleep. In contrast, LZ is higher in humans under the effect of psychedelics, including subanesthetic doses of ketamine. However, it is both unclear how this result would be modulated by varying ketamine doses, and whether it would extend to other species. Here we studied LZ with and without auditory stimulation during wakefulness and different sleep stages in 5 cats implanted with intracranial electrodes, as well as under subanesthetic doses of ketamine (5, 10, and 15 mg/kg i.m.). In line with previous results, LZ was lowest in NREM sleep, but similar in REM and wakefulness. Furthermore, we found an inverted U-shaped curve following different levels of ketamine doses in a subset of electrodes, primarily in prefrontal cortex. However, it is worth noting that the variability in the ketamine dose-response curve across cats and cortices was larger than that in the sleep-stage data, highlighting the differential local dynamics created by two different ways of modulating conscious state. These results replicate previous findings, both in humans and other species, demonstrating that neural complexity is highly sensitive to capture state changes between wake and sleep stages while adding a local cortical description. Finally, this study describes the differential effects of ketamine doses, replicating a rise in complexity for low doses, and further fall as doses approach anesthetic levels in a differential manner depending on the cortex.

show abstract

Section: Discussionmentioning

confidence: 99%

Ketamine and sleep modulate neural complexity dynamics in cats

Pascovich

Castro-Zaballa

Mediano

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…This would shed light on how the low-level features modulated the brain dynamics, since in this study we focused more on the semantic features of the stimulation. Moreover, the careful investigation of how and to what extent DeepDream can be compared to actual altered experience would have a considerable impact on the field of psychedelic research, especially in light of recent findings suggesting an important role of the external stimulation on the brain dynamics of hallucinatory states [ 43 ]. Since DeepDream, by definition, mimics hallucinatory perception using external stimulation, it would be interesting to use it as a tool to further explore this aspect of psychedelic brain dynamics.…”

Section: Discussionmentioning

confidence: 99%

Increased Entropic Brain Dynamics during DeepDream-Induced Altered Perceptual Phenomenology

Greco

Gallitto

D’Alessandro

et al. 2021

Entropy

View full text Add to dashboard Cite

In recent years, the use of psychedelic drugs to study brain dynamics has flourished due to the unique opportunity they offer to investigate the neural mechanisms of conscious perception. Unfortunately, there are many difficulties to conduct experiments on pharmacologically-induced hallucinations, especially regarding ethical and legal issues. In addition, it is difficult to isolate the neural effects of psychedelic states from other physiological effects elicited by the drug ingestion. Here, we used the DeepDream algorithm to create visual stimuli that mimic the perception of hallucinatory states. Participants were first exposed to a regular video, followed by its modified version, while recording electroencephalography (EEG). Results showed that the frontal region’s activity was characterized by a higher entropy and lower complexity during the modified video, with respect to the regular one, at different time scales. Moreover, we found an increased undirected connectivity and a greater level of entropy in functional connectivity networks elicited by the modified video. These findings suggest that DeepDream and psychedelic drugs induced similar altered brain patterns and demonstrate the potential of adopting this method to study altered perceptual phenomenology in neuroimaging research.

show abstract

“…Additionally, while shamanic practitioners kept their eyes closed during shamanic drumming, methodology varied across the studies included by Studerus et al ( 2010 ). Recent literature examining the impact of external stimulation during the psychedelic state found that the greatest changes in brain activity (i.e., brain entropy) occurred during eye closure (Mediano et al, 2020 ). Thus, the heightened OAV scores in shamanic practitioners compared to those of individuals under the influence of psychedelics may be due to the inclusion of less intense experiences due to eye-opening.…”

Section: Methodologic Strengths and Weaknessesmentioning

confidence: 99%

Neural Correlates of the Shamanic State of Consciousness

Huels

Kim

Lee

et al. 2021

Front. Hum. Neurosci.

View full text Add to dashboard Cite

Psychedelics have been recognized as model interventions for studying altered states of consciousness. However, few empirical studies of the shamanic state of consciousness, which is anecdotally similar to the psychedelic state, 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 an 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.

show abstract

Effects of external stimulation on psychedelic state neurodynamics

Cited by 38 publications

References 58 publications

Ketamine and sleep modulate neural complexity dynamics in cats

Ketamine and sleep modulate neural complexity dynamics in cats

Increased Entropic Brain Dynamics during DeepDream-Induced Altered Perceptual Phenomenology

Neural Correlates of the Shamanic State of Consciousness

Contact Info

Product

Resources

About