scholarly journals Increased signal diversity/complexity of spontaneous EEG, but not evoked EEG responses, in ketamine-induced psychedelic state in humans

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242056
Author(s):  
Nadine Farnes ◽  
Bjørn E. Juel ◽  
André S. Nilsen ◽  
Luis G. Romundstad ◽  
Johan F. Storm
Keyword(s):  
Subjective Experience ◽  
Brain Activity ◽  
Altered States Of Consciousness ◽  
Altered States ◽  
Eeg Signal ◽  
Eyes Closed ◽  
States Of Consciousness ◽  
Significant Difference ◽  
Eyes Open ◽  
Signal Diversity

How and to what extent electrical brain activity reflects pharmacologically altered states and contents of consciousness, is not well understood. Therefore, we investigated whether measures of evoked and spontaneous electroencephalographic (EEG) signal diversity are altered by sub-anaesthetic levels of ketamine compared to normal wakefulness, and how these measures relate to subjective experience. High-density 62-channel EEG was used to record spontaneous brain activity and responses evoked by transcranial magnetic stimulation (TMS) in 10 healthy volunteers before and during administration of sub-anaesthetic doses of ketamine in an open-label within-subject design. Evoked signal diversity was assessed using the perturbational complexity index (PCI), calculated from EEG responses to TMS perturbations. Signal diversity of spontaneous EEG, with eyes open and eyes closed, was assessed by Lempel Ziv complexity (LZc), amplitude coalition entropy (ACE), and synchrony coalition entropy (SCE). Although no significant difference was found in TMS-evoked complexity (PCI) between the sub-anaesthetic ketamine condition and normal wakefulness, all measures of spontaneous EEG signal diversity (LZc, ACE, SCE) showed significantly increased values in the sub-anaesthetic ketamine condition. This increase in signal diversity correlated with subjective assessment of altered states of consciousness. Moreover, spontaneous signal diversity was significantly higher when participants had eyes open compared to eyes closed, both during normal wakefulness and during influence of sub-anaesthetic ketamine. The results suggest that PCI and spontaneous signal diversity may reflect distinct, complementary aspects of changes in brain properties related to altered states of consciousness: the brain’s capacity for information integration, assessed by PCI, might be indicative of the brain’s ability to sustain consciousness, while spontaneous complexity, as measured by EEG signal diversity, may be indicative of the complexity of conscious content. Thus, sub-anaesthetic ketamine may increase the complexity of the conscious content and the brain activity underlying it, while the level or general capacity for consciousness remains largely unaffected.

scholarly journals Increased signal diversity/complexity of spontaneous EEG, but not evoked EEG responses, in ketamine-induced psychedelic state in humans

2019 ◽  
Author(s):  
Nadine Farnes ◽  
Bjørn E. Juel ◽  
André S. Nilsen ◽  
Luis G. Romundstad ◽  
Johan F. Storm
Keyword(s):  
Brain Activity ◽  
Altered States Of Consciousness ◽  
Altered States ◽  
Eeg Signal ◽  
Eyes Closed ◽  
Electrical Brain Activity ◽  
States Of Consciousness ◽  
Significant Difference ◽  
Eyes Open ◽  
Signal Diversity

AbstractObjectiveHow and to what extent electrical brain activity is affected in pharmacologically altered states of consciousness, where it is mainly the phenomenological content rather than the level of consciousness that is altered, is not well understood. An example is the moderately psychedelic state caused by low doses of ketamine. Therefore, we investigated whether and how measures of evoked and spontaneous electroencephalographic (EEG) signal diversity are altered by sub-anaesthetic levels of ketamine compared to normal wakefulness, and how these measures relate to subjective assessments of consciousness.MethodsHigh-density electroencephalography (EEG, 62 channels) was used to record spontaneous brain activity and responses evoked by transcranial magnetic stimulation (TMS) in 10 healthy volunteers before and after administration of sub-anaesthetic doses of ketamine in an open-label within-subject design. Evoked signal diversity was assessed using the perturbational complexity index (PCI), calculated from the global EEG responses to local TMS perturbations. Signal diversity of spontaneous EEG, with eyes open and eyes closed, was assessed by Lempel Ziv complexity (LZc), amplitude coalition entropy (ACE), and synchrony coalition entropy (SCE).ResultsAlthough no significant difference was found in the index of TMS-evoked complexity (PCI) between the sub-anaesthetic ketamine condition and normal wakefulness, all the three measures of spontaneous EEG signal diversity showed significantly increased values in the sub-anaesthetic ketamine condition. This increase in signal diversity also correlated with subjective assessment of altered states of consciousness. Moreover, spontaneous signal diversity was significantly higher when participants had eyes open compared to eyes closed, both during normal wakefulness and during influence of sub-anaesthetic ketamine doses.ConclusionThe results suggest that PCI and spontaneous signal diversity may be complementary and potentially measure different aspects of consciousness. Thus, our results seem compatible with PCI being indicative of the brain’s ability to sustain consciousness, as indicated by previous research, while it is possible that spontaneous EEG signal diversity may be indicative of the complexity of conscious content. The observed sensitivity of the latter measures to visual input seems to support such an interpretation. Thus, sub-anaesthetic ketamine may increase the complexity of both the conscious content (experience) and the brain activity underlying it, while the level, degree, or general capacity of consciousness remains largely unaffected.

scholarly journals Increased spontaneous EEG signal diversity during stroboscopically-induced altered states of consciousness

2019 ◽  
Author(s):  
David J. Schwartzman ◽  
Michael Schartner ◽  
Benjamin B. Ador ◽  
Francesca Simonelli ◽  
Acer Y.-C. Chang ◽  
...  
Keyword(s):  
Subjective Experience ◽  
Altered States Of Consciousness ◽  
Altered States ◽  
Eeg Signal ◽  
Visual Hallucinations ◽  
Subjective Experiences ◽  
Eeg Signals ◽  
Neural Signal ◽  
States Of Consciousness ◽  
Signal Diversity

AbstractWhat are the global neuronal signatures of altered states of consciousness (ASC)? Recently, increases in neural signal diversity, compared to those found in wakeful rest, have been reported during psychedelic states. Neural signal diversity has previously been identified as a robust signature of the state of consciousness, showing lower scores during sleep or anaesthesia compared to wakeful rest. The increased neural signal diversity during psychedelic states raises the additional possibility that it may also reflect the increased diversity of subjective experiences associated with these states. However, psychedelic states involve widespread neuropsychopharmacological changes, only some of which may be associated with altered phenomenology. Therefore, we used stroboscopic stimulation to induce non-pharmacological altered states of consciousness while measuring the diversity of EEG signals. Stroboscopic stimulation caused substantial increases in the intensity and range of subjective experiences, with reports of both simple and complex visual hallucinations. These experiences were accompanied by increases in EEG signal diversity scores (measured using Lempel-Ziv complexity) exceeding those associated with wakeful rest, in line with studies of the psychedelic state. Our findings support the proposal that EEG signal diversity reflects the diversity of subjective experience that is associated with different states of consciousness.

Synaesthetic Overdrive

2018 ◽  
Author(s):  
Jonathan Weinel
Keyword(s):  
Subjective Experience ◽  
Visual Media ◽  
Altered States Of Consciousness ◽  
Altered States ◽  
Visual Music ◽  
Background Theory ◽  
States Of Consciousness ◽  
Feature Films ◽  
Expanded Cinema ◽  
Improved Accuracy

This chapter discusses altered states of consciousness in audio-visual media, such as films, psychedelic light shows, and VJ performances. First, some background theory is introduced, explaining the main categories of film sound, and what research tells us regarding the way in which sound influences the perception of visual images and vice versa. Following this background section, a tour is provided through various films that represent altered states of consciousness, including surrealist movies, ‘trance films’, and Hollywood feature films. These demonstrate a progression, where more recent movies are able to make use of digital audio and visual effects to represent the subjective experience of altered states with improved accuracy. Meanwhile, beyond the traditional confines of the cinema, ‘expanded cinema’ works such as visual music, psychedelic light shows, and VJ performances have provided increasingly sophisticated synaesthetic experiences, which are designed to transform the consciousness of their audience.

scholarly journals Intrinsic Brain Activity in Altered States of Consciousness

2008 ◽  
Vol 1129 (1) ◽  
pp. 119-129 ◽  
Author(s):  
M. Boly ◽  
C. Phillips ◽  
L. Tshibanda ◽  
A. Vanhaudenhuyse ◽  
M. Schabus ◽  
...  
Keyword(s):  
Brain Activity ◽  
Altered States Of Consciousness ◽  
Altered States ◽  
States Of Consciousness ◽  
Intrinsic Brain Activity

scholarly journals Neural correlates of the shamanic state of consciousness

2020 ◽  
Author(s):  
Emma R Huels ◽  
Hyoungkyu Kim ◽  
UnCheol Lee ◽  
Tarik Bel-Bahar ◽  
Angelo Colmenero ◽  
...  
Keyword(s):  
Classical Music ◽  
Empirical Studies ◽  
Neural Correlates ◽  
Altered States Of Consciousness ◽  
Music Listening ◽  
Altered States ◽  
Beta Band ◽  
Drug Induced ◽  
States Of Consciousness ◽  
Signal Diversity

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.

scholarly journals EEG microstate dynamics indicate a U-shaped path to propofol-induced loss of consciousness

2021 ◽  
Author(s):  
Fiorenzo Artoni ◽  
Julien Maillard ◽  
Juliane Britz ◽  
Martin Seeber ◽  
Christopher Lysakowski ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Brain Activity ◽  
Altered States Of Consciousness ◽  
Initial Increase ◽  
Altered States ◽  
Stream Of Consciousness ◽  
Sequence Complexity ◽  
States Of Consciousness ◽  
Brain States ◽  
The Brain

It is commonly believed that the stream of consciousness is not continuous but parsed into transient brain states manifesting themselves as discrete spatiotemporal patterns of global neuronal activity. Electroencephalographical (EEG) microstates are proposed as the neurophysiological correlates of these transiently stable brain states that last for fractions of seconds. To further understand the link between EEG microstate dynamics and consciousness, we continuously recorded high-density EEG in 23 surgical patients from their awake state to unconsciousness, induced by step-wise increasing concentrations of the intravenous anesthetic propofol. Besides the conventional parameters of microstate dynamics, we introduce a new method that estimates the complexity of microstate sequences. The brain activity under the surgical anesthesia showed a decreased sequence complexity of the stereotypical microstates, which became sparser and longer-lasting. However, we observed an initial increase in microstates' temporal dynamics and complexity with increasing depth of sedation leading to a distinctive U-shape that may be linked to the paradoxical excitation induced by moderate levels of propofol. Our results support the idea that the brain is in a metastable state under normal conditions, balancing between order and chaos in order to flexibly switch from one state to another. The temporal dynamics of EEG microstates indicate changes of this critical balance between stability and transition that lead to altered states of consciousness.

scholarly journals Neural correlates of the DMT experience assessed with multivariate EEG

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Christopher Timmermann ◽  
Leor Roseman ◽  
Michael Schartner ◽  
Raphael Milliere ◽  
Luke T. J. Williams ◽  
...  
Keyword(s):  
Subjective Experience ◽  
Brain Activity ◽  
Plasma Concentrations ◽  
Oscillatory Activity ◽  
Visual Component ◽  
Eyes Closed ◽  
Drug Plasma Concentrations ◽  
Drug Plasma ◽  
Oscillatory Power ◽  
Signal Diversity

AbstractStudying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,N-Dimethyltryptamine (DMT - a fast-acting tryptamine psychedelic) offers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the effects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the alpha and beta bands and robustly increased spontaneous signal diversity. Time-referenced and neurophenomenological analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience - particularly its eyes-closed visual component. These findings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specific components of the subjective experience, thus advancing our understanding of the neurobiological underpinnings of immersive states of consciousness.

Effect of a Static Magnetic Field (1.5T) on Brain Oscillatory Activities in Resting State Condition

2008 ◽  
Vol 21 (5) ◽  
pp. 629-635 ◽  
Author(s):  
E. Formaggio ◽  
M. Avesani ◽  
S.F. Storti ◽  
F. Milanese ◽  
A. Gasparini ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Static Magnetic Field ◽  
Alpha Power ◽  
Eeg Signal ◽  
Eyes Closed ◽  
Prime Concern ◽  
Eeg Data ◽  
Significant Difference ◽  
Eyes Open ◽  
The Magnetic Field

The aim of the present study was to compare the EEG signal recorded outside and inside a 1.5T magnetic resonance (MR) scanner. The EEG was recorded in eyes open and eyes closed conditions using a digital recording MR-compatible system. To characterize how a static magnetic field induces changes in EEG signal, EEG data were analyzed using FFT frequency analysis. No significant difference between the alpha powers recorded outside and inside the magnetic field was observed in eyes closed conditions. However, in eyes open condition there was a significant increase in alpha power inside the magnet in comparison to the outside position. The changes in alpha power according to the eyes open/closed conditions could be inversely correlated to a subject's state of wakefulness and due to some physiological changes, rather than an effect of the magnetic field. This experiment suggests that subjects' state of wakefulness is of prime concern when performing functional MRI.

scholarly journals Whole-Brain Models to Explore Altered States of Consciousness from the Bottom Up

2020 ◽  
Vol 10 (9) ◽  
pp. 626 ◽  
Author(s):  
Rodrigo Cofré ◽  
Rubén Herzog ◽  
Pedro A.M. Mediano ◽  
Juan Piccinini ◽  
Fernando E. Rosas ◽  
...  
Keyword(s):  
Brain Activity ◽  
Generative Models ◽  
Altered States Of Consciousness ◽  
Global Changes ◽  
Altered States ◽  
Altered Consciousness ◽  
Whole Brain ◽  
Bottom Up ◽  
States Of Consciousness ◽  
Brain Models

The scope of human consciousness includes states departing from what most of us experience as ordinary wakefulness. These altered states of consciousness constitute a prime opportunity to study how global changes in brain activity relate to different varieties of subjective experience. We consider the problem of explaining how global signatures of altered consciousness arise from the interplay between large-scale connectivity and local dynamical rules that can be traced to known properties of neural tissue. For this purpose, we advocate a research program aimed at bridging the gap between bottom-up generative models of whole-brain activity and the top-down signatures proposed by theories of consciousness. Throughout this paper, we define altered states of consciousness, discuss relevant signatures of consciousness observed in brain activity, and introduce whole-brain models to explore the biophysics of altered consciousness from the bottom-up. We discuss the potential of our proposal in view of the current state of the art, give specific examples of how this research agenda might play out, and emphasize how a systematic investigation of altered states of consciousness via bottom-up modeling may help us better understand the biophysical, informational, and dynamical underpinnings of consciousness.

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