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Concept: Altered state of consciousness


What is the level of consciousness of the psychedelic state? Empirically, measures of neural signal diversity such as entropy and Lempel-Ziv (LZ) complexity score higher for wakeful rest than for states with lower conscious level like propofol-induced anesthesia. Here we compute these measures for spontaneous magnetoencephalographic (MEG) signals from humans during altered states of consciousness induced by three psychedelic substances: psilocybin, ketamine and LSD. For all three, we find reliably higher spontaneous signal diversity, even when controlling for spectral changes. This increase is most pronounced for the single-channel LZ complexity measure, and hence for temporal, as opposed to spatial, signal diversity. We also uncover selective correlations between changes in signal diversity and phenomenological reports of the intensity of psychedelic experience. This is the first time that these measures have been applied to the psychedelic state and, crucially, that they have yielded values exceeding those of normal waking consciousness. These findings suggest that the sustained occurrence of psychedelic phenomenology constitutes an elevated level of consciousness - as measured by neural signal diversity.

Concepts: Philosophy of mind, Consciousness, Unconscious mind, Phenomenology, Psychedelic drug, Altered state of consciousness, 8-Circuit Model of Consciousness


The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regions more active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity through most parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. Altogether, our results support the notion that the altered state of consciousness induced by Ayahuasca, like those induced by psilocybin (another serotonergic psychedelic), meditation and sleep, is linked to the modulation of the activity and the connectivity of the DMN.

Concepts: Brain, Cerebrum, Mind, Consciousness, Cognitive neuroscience, Limbic system, Frontal lobe, Altered state of consciousness


Acute adverse psychological reactions to classic hallucinogens (“bad trips” or “challenging experiences”), while usually benign with proper screening, preparation, and support in controlled settings, remain a safety concern in uncontrolled settings (such as illicit use contexts). Anecdotal and case reports suggest potential adverse acute symptoms including affective (panic, depressed mood), cognitive (confusion, feelings of losing sanity), and somatic (nausea, heart palpitation) symptoms. Responses to items from several hallucinogen-sensitive questionnaires (Hallucinogen Rating Scale, the States of Consciousness Questionnaire, and the Five-Dimensional Altered States of Consciousness questionnaire) in an Internet survey of challenging experiences with the classic hallucinogen psilocybin were used to construct and validate a Challenging Experience Questionnaire. The stand-alone Challenging Experience Questionnaire was then validated in a separate sample. Seven Challenging Experience Questionnaire factors (grief, fear, death, insanity, isolation, physical distress, and paranoia) provide a phenomenological profile of challenging aspects of experiences with psilocybin. Factor scores were associated with difficulty, meaningfulness, spiritual significance, and change in well-being attributed to the challenging experiences. The factor structure did not differ based on gender or prior struggle with anxiety or depression. The Challenging Experience Questionnaire provides a basis for future investigation of predictors and outcomes of challenging experiences with classic hallucinogens.

Concepts: Psychology, Factor analysis, Major depressive disorder, Fear, Psychedelic drug, Psilocybin mushrooms, Altered state of consciousness, Bad trip


Extreme rituals (body-piercing, fire-walking, etc.) are anecdotally associated with altered states of consciousness-subjective alterations of ordinary mental functioning (Ward, 1984)-but empirical evidence of altered states using both direct and indirect measures during extreme rituals in naturalistic settings is limited. Participants in the “Dance of Souls”, a 3.5-hour event during which participants received temporary piercings with hooks or weights attached to the piercings and danced to music provided by drummers, responded to measures of two altered states of consciousness. Participants also completed measures of positive and negative affect, salivary cortisol (a hormone associated with stress), self-reported stress, sexual arousal, and intimacy. Both pierced participants (pierced dancers) and non-pierced participants (piercers, piercing assistants, observers, drummers, and event leaders) showed evidence of altered states aligned with transient hypofrontality (Dietrich, 2003; measured with a Stroop test) and flow (Csikszentmihalyi, 1990; Csikszentmihalyi & Csikszentmihalyi, 1990; measured with the Flow State Scale). Both pierced and non-pierced participants also reported decreases in negative affect and psychological stress and increases in intimacy from before to after the ritual. Pierced and non-pierced participants showed different physiological reactions, however, with pierced participants showing increases in cortisol and non-pierced participants showing decreases from before to during the ritual. Overall, the ritual appeared to induce different physiological effects but similar psychological effects in focal ritual participants (i.e., pierced dancers) and in participants adopting other roles.

Concepts: Metabolic syndrome, Mind, Positive psychology, Stress, Dance, Ritual, Body piercing, Altered state of consciousness


Perturbing a system and observing the consequences is a classic scientific strategy for understanding a phenomenon. Psychedelic drugs perturb consciousness in a marked and novel way and thus are powerful tools for studying its mechanisms. In the present analysis, we measured changes in resting-state functional connectivity (RSFC) between a standard template of different independent components analysis (ICA)-derived resting state networks (RSNs) under the influence of two different psychoactive drugs, the stimulant/psychedelic hybrid, MDMA, and the classic psychedelic, psilocybin. Both were given in placebo-controlled designs and produced marked subjective effects, although reports of more profound changes in consciousness were given after psilocybin. Between-network RSFC was generally increased under psilocybin, implying that networks become less differentiated from each other in the psychedelic state. Decreased RSFC between visual and sensorimotor RSNs was also observed. MDMA had a notably less marked effect on between-network RSFC, implying that the extensive changes observed under psilocybin may be exclusive to classic psychedelic drugs and related to their especially profound effects on consciousness. The novel analytical approach applied here may be applied to other altered states of consciousness to improve our characterization of different conscious states and ultimately advance our understanding of the brain mechanisms underlying them.

Concepts: Scientific method, Brain, Consciousness, Psychoactive drug, Recreational drug use, Psychedelic drug, Altered state of consciousness, Psilocybin


The altered state of consciousness produced by general anesthetics is associated with a variety of changes in the brain’s electrical activity. Under hyperpolarizing influences such as anesthetic drugs, cortical neurons oscillate at ~1 Hz, which is measurable as slow waves in the electroencephalogram (EEG). We have administered propofol anesthesia to 16 subjects and found that, after they had lost behavioral responsiveness (response to standard sensory stimuli), each individual’s EEG slow-wave activity (SWA) rose to saturation and then remained constant despite increasing drug concentrations. We then simultaneously collected functional magnetic resonance imaging and EEG data in 12 of these subjects during propofol administration and sensory stimulation. During the transition to SWA saturation, the thalamocortical system became isolated from sensory stimuli, whereas internal thalamocortical exchange persisted. Rather, an alternative and more fundamental cortical network (which includes the precuneus) responded to all sensory stimulation. We conclude that SWA saturation is a potential individualized indicator of perception loss that could prove useful for monitoring depth of anesthesia and studying altered states of consciousness.

Concepts: Brain, Magnetic resonance imaging, Cerebral cortex, Electroencephalography, Mind, Local anesthetic, Anesthetic, Altered state of consciousness


Empirical findings in the Cognitive Sciences on the relationship between feeling states and subjective time have led to the assumption that time perception entails emotional and interoceptive states. The perception of time would thereafter be embodied; the bodily self, the continuous input from the body is the functional anchor of phenomenal experience and the mental self. Subjective time emerges through the existence of the self across time as an enduring and embodied entity. This relation is prominently disclosed in studies on altered states of consciousness such as in meditative states, under the influence of hallucinogens as well as in many psychiatric and neurological conditions. An increased awareness of oneself coincides with an increased awareness of time. Conversely, a decreased awareness of the self is associated with diminished awareness of time. The body of empirical work within different conceptual frameworks on the intricate relationship between self and time is presented and discussed.

Concepts: Time, Psychology, Perception, Mind, Consciousness, Concepts in metaphysics, Unsolved problems in neuroscience, Altered state of consciousness


Abstract Frewen and Lanius (in press) recently articulated a “4-D model” as a framework for classifying symptoms of posttraumatic stress into those that potentially occur within normal waking consciousness (NWC) versus those that intrinsically represent dissociative experiences of trauma-related altered states of consciousness (TRASC). Four dimensions were specified: time-memory, thought, body, and emotion. The 4-D model further hypothesizes that, in traumatized persons, symptoms of TRASC, as compared with NWC forms of distress, will be: 1) observed less frequently; 2) less intercorrelated, especially as measured as moment-to-moment states; 3) observed more frequently in people with high dissociative symptomatology as measured independently; and 4) observed more often in people who have experienced repeated traumatization, particularly early developmental trauma. The aim of the present research was to begin to evaluate these four predictions of the 4-D model. Within a sample of 74 women with PTSD primarily due to histories of childhood trauma, as well as within a second sample of 504 undergraduates (384 female), the first two hypotheses of the 4-D model were supported. Additionally, within the PTSD sample, the third hypothesis was supported. However, inconsistent with the fourth hypothesis, severity of childhood trauma history was not strongly associated with TRASC. We conclude that the hypotheses articulated by the 4-D model were generally supported, although further research in different trauma-related disorders is needed and the role of childhood trauma history in the etiology of TRASC requires further research.

Concepts: Scientific method, Observation, Psychological trauma, Empiricism, Hypothesis, Posttraumatic stress disorder, Stress, Altered state of consciousness


A new control condition called Wiki is introduced. Key themes of each test suggestion of the Stanford Hypnotic Susceptibility Scale, Form C, were matched by a corresponding extract from The authors compared phenomenological reports of participants across 4 conditions: hypnosis split into high and low hypnotizable subgroups, music, and Wiki condition, using the Phenomenology of Consciousness Inventory. High hypnotizables undergoing hypnosis reported higher altered experience and altered states of awareness than individuals in the Wiki condition, supporting the authors' hypothesis that the Wiki condition does not evoke an altered state of consciousness (internal dialogue, volitional control, and self-awareness did not differ). Wiki might be a viable control condition in hypnosis research given further examination.

Concepts: Philosophy of mind, Consciousness, Awareness, Self-awareness, Phenomenology, Hypnosis, Altered state of consciousness, Theodore R. Sarbin


It has been proposed that the thalamocortical system is an important site of action of hallucinogenic drugs and an essential component of the neural correlates of consciousness. Hallucinogenic drugs such as LSD can be used to induce profoundly altered states of consciousness, and it is thus of interest to test the effects of these drugs on this system.

Concepts: Drug, Philosophy of mind, Consciousness, Hallucination, Psychedelics, dissociatives and deliriants, Altered state of consciousness, Consciousness studies, Neural correlates of consciousness