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Lisa Lindquist, Gregory McIntire, Sarah Haigh; The effect of chromaticity separation on neural processing during a visual task. Journal of Vision 2020;20(11):828. doi: https://doi.org/10.1167/jov.20.11.828.
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Our modern environment includes synthetic visual stimuli that frequently deviate from natural scenes, for example, flickering lights and computer screens, striped patterns and extreme color contrasts. Large differences in chromaticity separation (e.g. red and blue) elicit visual discomfort, large metabolic responses, and greater alpha suppression compared to small chromaticity separations (e.g. pink and purple). This suggests that visual cortex over-responds to large color differences. To investigate if uncomfortable chromatic stimuli negatively impact visual task performance, we presented 30 individuals (11 male and 19 female) with grating patterns composed of pairs of colors (either red-blue, blue-green or red-green) that varied in their chromaticity separation (small, mid-small, mid-large, and large; calculated in CIE UCS 1976 space). Gratings were superimposed with black letters, presented in a white circle and situated at the center of the screen. Participants completed a continuous pairs task while electroencephalography (EEG) was recorded. Letters were presented sequentially at 3Hz and the gratings alternated with a grey screen at 5Hz. This allowed for frequency tagging in the steady-state visual evoked potential (SSVEP) to assess responses to incremental differences in chromatic separation (at 5Hz) and their effect on task-related processing (at 3Hz). A subset of participants rated the gratings on a 9-point scale of discomfort. In accordance with prior research, we observed greater ratings of discomfort and increased power at 5Hz with the larger chromaticity separations, but no significant effect on power at 3Hz and no consistent effect on behavioral accuracy. Despite eliciting heightened neural responses, short term exposure to uncomfortable chromatic stimuli does not adversely impact visual task performance.
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