Neural dynamics of stroboscopic stimulation at different stimulation frequencies

Stroboscopic stimulation has been previously shown to induce visual hallucinations and altered states of consciousness, state by entraining the brain to the driving frequency, similar to those reported during the psychedelics although little systematic research exists on the effect of specific stimulation frequency on experience. The present study investigated the effects of different stroboscopic stimulation frequencies on neural dynamics, such as signal diversity (Lempel-Ziv complexity) and spectral power and attempted to relate these changes to self-reported changes in experiential content. The results indicated that the stimulation frequencies near the alpha band (8 to 12 Hz) caused the greatest increase across all neural measures, with 8 Hz consistently displaying the most pronounced results, relative to baseline. All tested frequencies led to an increase in all experiential dimensions, relative to baseline.

Differential effects of propofol and ketamine on critical brain dynamics

PLoS Computational Biology ◽

10.1371/journal.pcbi.1008418 ◽

2020 ◽

Vol 16 (12) ◽

pp. e1008418

Author(s):

Thomas F. Varley ◽

Olaf Sporns ◽

Aina Puce ◽

John Beggs

Keyword(s):

Cellular Level ◽

Brain Dynamics ◽

Neuronal Cultures ◽

Altered States ◽

Differential Effects ◽

States Of Consciousness ◽

Anaesthetized Rats ◽

And Control ◽

Whether the brain operates at a critical “tipping” point is a long standing scientific question, with evidence from both cellular and systems-scale studies suggesting that the brain does sit in, or near, a critical regime. Neuroimaging studies of humans in altered states of consciousness have prompted the suggestion that maintenance of critical dynamics is necessary for the emergence of consciousness and complex cognition, and that reduced or disorganized consciousness may be associated with deviations from criticality. Unfortunately, many of the cellular-level studies reporting signs of criticality were performed in non-conscious systems (in vitro neuronal cultures) or unconscious animals (e.g. anaesthetized rats). Here we attempted to address this knowledge gap by exploring critical brain dynamics in invasive ECoG recordings from multiple sessions with a single macaque as the animal transitioned from consciousness to unconsciousness under different anaesthetics (ketamine and propofol). We use a previously-validated test of criticality: avalanche dynamics to assess the differences in brain dynamics between normal consciousness and both drug-states. Propofol and ketamine were selected due to their differential effects on consciousness (ketamine, but not propofol, is known to induce an unusual state known as “dissociative anaesthesia”). Our analyses indicate that propofol dramatically restricted the size and duration of avalanches, while ketamine allowed for more awake-like dynamics to persist. In addition, propofol, but not ketamine, triggered a large reduction in the complexity of brain dynamics. All states, however, showed some signs of persistent criticality when testing for exponent relations and universal shape-collapse. Further, maintenance of critical brain dynamics may be important for regulation and control of conscious awareness.

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

10.1101/508697 ◽

2019 ◽

Cited By ~ 2

Author(s):

Nadine Farnes ◽

Bjørn E. Juel ◽

André S. Nilsen ◽

Luis G. Romundstad ◽

Johan F. Storm

Keyword(s):

Brain Activity ◽

Altered States ◽

Eeg Signal ◽

Eyes Closed ◽

Electrical Brain Activity ◽

States Of Consciousness ◽

Significant Difference ◽

Eyes Open ◽

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.

Altered states of consciousness in epilepsy: a DTI study of the brain

International Journal of Neuroscience ◽

10.1080/00207454.2016.1229668 ◽

2016 ◽

Vol 127 (8) ◽

pp. 667-672 ◽

Cited By ~ 4

Author(s):

Fangfang Xie ◽

Wu Xing ◽

Xiaoyi Wang ◽

Weihua Liao ◽

Wei Shi

Keyword(s):

Altered States ◽

States Of Consciousness ◽

Criticality Creates a Functional Platform for Network Transitions between Internal and External Processing Modes in the Human Brain

10.1101/2020.12.25.424325 ◽

2020 ◽

Author(s):

Minkyung Kim ◽

Hyoungkyu Kim ◽

Zirui Huang ◽

George A. Mashour ◽

Denis Jordan ◽

...

Keyword(s):

Brain Network ◽

External Information ◽

Altered States ◽

Order And Disorder ◽

States Of Consciousness ◽

Processing Modes ◽

Internal Information ◽

External Stimuli ◽

The Brain ◽

Temporal Windows

AbstractContinuous switching between internal and external modes in the brain is a key process of constructing inner models of the outside world. However, how the brain continuously switches between two modes remains elusive. Here, we propose that a large synchronization fluctuation of the brain network emerging only near criticality (i.e., a balanced state between order and disorder) spontaneously creates temporal windows with distinct preferences for integrating internal information of the network and external stimuli. Using a computational model and empirical data analysis during alterations of consciousness in human, we present that synchronized and incoherent networks respectively bias toward internal and external information with specific network configurations. The network preferences are the most prominent in conscious states; however, they disrupt in altered states of consciousness. We suggest that criticality produces a functional platform of the brain’s capability for continuous switching between two modes, which is crucial for the emergence of consciousness.

Neural correlates of the shamanic state of consciousness

10.1101/2020.07.20.212522 ◽

2020 ◽

Author(s):

Emma R Huels ◽

Hyoungkyu Kim ◽

UnCheol Lee ◽

Tarik Bel-Bahar ◽

Angelo Colmenero ◽

...

Keyword(s):

Classical Music ◽

Empirical Studies ◽

Neural Correlates ◽

Music Listening ◽

Altered States ◽

Beta Band ◽

Drug Induced ◽

States Of Consciousness ◽

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.

Oscillatory Components of Psychedelic Experience

Journal of Humanistic Psychology ◽

10.1177/00221678211041836 ◽

2021 ◽

pp. 002216782110418

Author(s):

Paul Grof

Keyword(s):

Imaging Techniques ◽

Brain Activity ◽

Dynamic Aspect ◽

Normal Range ◽

States Of Consciousness ◽

Psychedelic Drug ◽

Experiential Content ◽

Transformative Process ◽

Oscillatory Brain Activity ◽

As humanity has been utilizing psychedelic substances for millennia, much knowledge has already been accumulated about the exploratory potential and therapeutic power of the psychedelic-induced nonordinary states of consciousness (NSC). However, we still have only a limited understanding of the process that unfolds in mind and the brain. Only recently have systematic investigations become possible, as the myths about psychedelics are abating and the legal strictures gradually loosening. With the availability of brain imaging techniques, exciting findings have been made about the associated dynamic brain processes. Our prospective observations of spontaneously generated NSC, major mood disorders, have been elucidating another dynamic aspect, the oscillatory brain processes. The findings indicate that the NSC’s propensity is markedly increased at the peaks of the oscillatory brain activity and that the NSC entirely unfolds when the oscillations exceed their normal range. The observation that neurobiological correlates of experientially opposite NSC, melancholy and mania, appear qualitatively the same is compatible with the concept that the experiential content is emerging from nonlocal consciousness. Psychedelic experiences are triggered by the administration of the psychedelic drug. However, they are influenced by nondrug factors and molded, in particular, by the individual’s mental set and the setting of the session. The transformative process can be utilized psychotherapeutically for healing and profound inner restructuring.

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

10.1101/2021.10.26.465841 ◽

2021 ◽

Author(s):

Fiorenzo Artoni ◽

Julien Maillard ◽

Juliane Britz ◽

Martin Seeber ◽

Christopher Lysakowski ◽

...

Keyword(s):

Temporal Dynamics ◽

Brain Activity ◽

Initial Increase ◽

Altered States ◽

Stream Of Consciousness ◽

Sequence Complexity ◽

States Of Consciousness ◽

Brain States ◽

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.

Neural Correlates of the Shamanic State of Consciousness

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2021.610466 ◽

2021 ◽

Vol 15 ◽

Cited By ~ 1

Author(s):

Emma R. Huels ◽

Hyoungkyu Kim ◽

UnCheol Lee ◽

Tarik Bel-Bahar ◽

Angelo V. Colmenero ◽

...

Keyword(s):

Classical Music ◽

Empirical Studies ◽

Neural Correlates ◽

Music Listening ◽

Altered States ◽

Beta Band ◽

Drug Induced ◽

States Of Consciousness ◽

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.

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

PLoS ONE ◽

10.1371/journal.pone.0242056 ◽

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 ◽

Eeg Signal ◽

Eyes Closed ◽

States Of Consciousness ◽

Significant Difference ◽

Eyes Open ◽

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.

Consciousness: A Very Short Introduction

10.1093/actrade/9780198794738.001.0001 ◽

2017 ◽

Cited By ~ 2

Author(s):

Susan Blackmore

Keyword(s):

Neural Correlates ◽

Altered States ◽

Short Introduction ◽

New Developments ◽

Brain Science ◽

States Of Consciousness ◽

The World ◽

Construction Of Self ◽

Consciousness is ‘the last great mystery for science’. How can a physical brain create our experience of the world? What creates our identity? Do we really have free will? Could consciousness itself be an illusion? Exciting new developments in brain science are continuing these debates, and the field has now expanded to include biologists, neuroscientists, psychologists, and philosophers. Consciousness: A Very Short Introduction clarifies the potentially confusing arguments, and the major theories, whilst also outlining the amazing pace of neuroscience discoveries. Covering areas such as construction of self in the brain, mechanisms of attention, neural correlates of consciousness, and physiology of altered states of consciousness, it highlights the latest findings.