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Brain electrical activity and subjective experience during altered states of consciousness: ganzfeld and hypnagogic states.

Jirí Wackermann, Peter Pütz, Simone Büchi, Inge Strauch, Dietrich Lehmann

International Journal of Psychophysiology November 2002 DOI: 10.1016/s0167-8760(02)00070-3 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational crossover study Peer reviewed
Sample size 12
Population Female paid volunteers
Topics Altered states of consciousness
Key findings Ganzfeld EEG spectra resembled waking states, not sleep onset, and only the 'absorption' dimension differentiated ganzfeld from other states. The authors argue that hypnagogic and ganzfeld-induced states are special cases of a broader class of 'hypnagoid' phenomena.

Abstract

Manifestations of experimentally induced altered states of consciousness in the brain's electrical activity as well as in subjective experience were explored via the hypnagogic state at sleep onset, and the state induced by exposure to an unstructured perceptual field (ganzfeld). Twelve female paid volunteers participated in sessions involving sleep onset, ganzfeld, and eyes-closed relaxed waking, and were repeatedly prompted for recall of their momentary mentation, according to a predefined schedule. Nineteen channel EEG, two channels EOG and EMG were recorded simultaneously. The mentation reports were followed by the subjects' ratings of their experience on a number of ordinal scales. Two-hundred and forty-one mentation reports were collected. EEG epochs immediately preceding the mentation reports were FFT-analysed and the spectra compared between states. The ganzfeld EEG spectrum, showing no signs of decreased vigilance, was very similar to the EEG spectrum of waking states, even showed a minor acceleration of alpha activity. The subjective experience data were reduced to four principal components: Factor I represented the subjective vigilance dimension, as confirmed by correlations with EEG spectral indices. Only Factor IV, the 'absorption' dimension, differentiated between the ganzfeld state (more absorption) and other states. In waking states and in ganzfeld, the subjects estimated elapsed time periods significantly shorter than in states at sleep onset. The results did not support the assumption of a hypnagogic nature of the ganzfeld imagery. Dream-like imagery can occur in various global functional states of the brain; hypnagogic and ganzfeld-induced states should be conceived as special cases of a broader class of 'hypnagoid' phenomena.

Comparable studies

Other randomized controlled trials on altered states of consciousness, most cited first.

Study Year Design Participants
Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor Healthy human participants 2018 Double-blind, randomized, counterbalanced, cross-over study n = 24
Effective connectivity changes in LSD-induced altered states of consciousness in humans. Healthy participants 2019 Double-blind, randomized, placebo-controlled, cross-over study n = 25
Dose-related effects of salvinorin A in humans: dissociative, hallucinogenic, and memory effects. Healthy hallucinogen-using adults 2013 Double-blind, placebo-controlled study n = 8
High doses of dextromethorphan, an NMDA antagonist, produce effects similar to classic hallucinogens. Healthy volunteers with histories of hallucinogen use 2012 Randomized controlled trial n = 12
A placebo-controlled investigation of synaesthesia-like experiences under LSD. 2016 Within-groups placebo-controlled pilot study

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