Abstract
IN a repeat of earlier research1,2 into the relationship between alpha abundance and visual thresholds for emotive words, red and green monochromatic lights were used as the visual stimuli. On the first presentation of each colour, results were in substantial agreement with those obtained in the previous work. Irrespective of stimulus wave-length, high thresholds for emotive words followed on sustained alpha abundance while low thresholds followed reduced alpha. The second presentation under a different colour, however, produced results which diverged somewhat from those previously reported. Irrespective of stimulus wave-length subjects tended to show higher thresholds for emotive than for neutral words, but those with higher thresholds for emotive words in red light showed reduced alpha abundance before reaching the threshold. This result is consistent with the finding3,4 that a red stimulus in juxtaposition to a potentially emotive subliminal stimulus will evoke emotional disturbance, and the finding5 that sympathetic activity decreases retinal sensitivity for light of long wave-length. All in all, the results suggest that while a given level of cortical activation may be necessary for awareness of a visual stimulus of low intensity, visual thresholds may also depend on a retinal variable under autonomic control.
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DIXON, N. Threshold Regulation and Stimulus Wave-length. Nature 210, 1291 (1966). https://doi.org/10.1038/2101291a0
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DOI: https://doi.org/10.1038/2101291a0
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