Academic journal article The Journal of Parapsychology

A Comparison of Ganzfeld and Hypnagogic State in Terms of Electrophysiological Measures and Subjective Experience

Academic journal article The Journal of Parapsychology

A Comparison of Ganzfeld and Hypnagogic State in Terms of Electrophysiological Measures and Subjective Experience

Article excerpt

ABSTRACT: The ganzfeld setting has often been used to induce experimentally the hypnagogic state, similar to that which occurs at sleep onset. However, the underlying assumption that the ganzfeld really induces a true hypnagogic state has not been adequately investigated to date.

The aim of this exploratory study was to investigate electrophysiological correlates and subjective dimensions of experience of: (a) the hypnagogic state, at sleep onset, and (b) the ganzfeld state, induced by homogenization of perceptual field. Twelve female paid volunteers ranging in age from 22 to 39 participated in the study. Nineteen channels EEG, 2 channels horizontal EOG, and 1 channel EMG were recorded in 5 experimental conditions: (a) waking state at daytime, (b) ganzfeld, (c) waking state before sleep onset, (d) sleep stage 1, and (e) sleep stage 2. Following a predefined schedule, the participants were given an acoustic signal and asked for a verbal report of their momentary subjective experiences and ratings of the reported experiences on several ordinal self-rating scales. The reports were recorded and transcribed later. A total of 241 reports with simultaneous EEG recordings were collected.

Data preprocessing and analysis were divided into several phases. The first phase aimed at the characterization of the induced states in terms of spectral measures of the electrical brain activity (EEG). FFT analysis of 5 consecutive 2-s epochs of EEG activity immediately preceding the prompt proved that the average EEG spectrum in the ganzfeld is more similar to that of the relaxed waking state than to that of sleep on-set. …

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