Electro-Encephalography: II. Visual Stimulation and the After-Image as Affecting the Occipital Alpha Rhythm

“…Situations that disturb equilibrium and demand adjustment, whether the disturbance arises from external or internal sources, tend to produce the effect. There may be an important mechanism of adaptation to sensory (including imaginal and autonomic) disturbance involved, a notion that gains some support not only from the evidence already cited, but also from the 'adaptation' and ' switch-off' effects observed by Jasper & Cruickshank (1937).…”

Section: Discussionmentioning

confidence: 91%

Use of Eeg in Study of Imagery

Barratt

1956

British J of Psychology

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An experiment was designed totest the hypothesis that suppressionof the amplitudeof thealpha rhythm provides a reliable objective index of visual imageryunder two conditions of problem solution, namely, solving a 'verbal' problem and solving a 'visual' problem. Sixty-nine subjects were examined in the following way: first, preliminary 'runs' were made with each subject for EEG recording under the It was found that, although the visual content of awareness during the two problem-solution periods as reported by the subjects differed markedly, suppression of alpha rhythms occurred under both conditions, the amplitudes in both caaes falling about half-way between the two values recorded in the preliminary 'runs'. There was, however, a greater suppression effect in the caae of the 'visual' problem. The results, aa a whole, therefore, suggest that the hypothesis is not tenable, since 'imagery' appears to be only one of many factors that may produce suppression effects. This conclusion is supported by a breakdown of the subject sample, according to reports of imagery on the verbal problem, which showed that there was no difference in the basic patterns aa between those who visualized the verbal problem and those who did not.Repeated solution in a check period, immediately following the solution period, made no significant difference to suppression of alpha in the verbal problem, but did so in the visual problem. The suggested interpretation follows Fisher (1916) in regarding this as a possible decrease in image content.

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“…When feedback was initiated, "alpha" durations decreased and "no-alpha" durations increased relative to the immediately prcDownloaded by [JAMES COOK UNIVERSITY] at 05:58 16 March 2015 ceding resting condition (3, 5 ) . As feedback continued, "alpha" durations increased slowly while "no-alpha" durations decreased rapidly, then more slowly ( l o ) .…”

Section: General System Behaviormentioning

confidence: 98%