Using Electroencephalography as a Method to Determine Blue-Yellow and Red-Green Perceptual Asymmetries in the Human Visual System
AuthorTolles, Traci A.
College of Science
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Knowledge of color perception in infants and children is limited; in order to develop research methods to gain an understanding of this particular age group, we must first develop objective methods within an adult population that can then be applied to children in future studies. We presented stimuli with a fast-periodic visual stimulation paradigm, and analyzed the resulting steady-state visual-evoked potentials using electroencephalography. We used this technique to directly measure whether a difference response is present between colors defined by two intermediate axes in cone-contrast color space, which elicit equal average responses from the two axes of retinal color coding. Adult human observers are more sensitive to contrast along one of these axes than the other, and a primary motivation of this study is to find a neural correlate for this perceptual asymmetry. We presented adult human observers with blue-yellow (135° - 315°) and red-green (45° - 225°) gratings at an alternation rate of 2.5 Hz, i.e., one presentation every 400ms for each grating. With the same paradigm, we also tested observers with an achromatic condition (i.e. pure luminance gratings) in order to compare difference responses elicited along achromatic axes to those for chromatic axes. Our results show that we created a stimulus design which elicits higher amplitude responses for chromatic stimuli (5.95 µV) compared to achromatic stimuli (4.81 µV). The lowest amplitude difference response between the chromatic axes was 1.72 µV at a contrast ratio of 1.17 for red-green to blue-yellow, and 0.09 µV at a contrast ratio of 1.07 for the achromatic axes. Designing a sensitive measure for comparing responses across chromatic axes that can be used with infants and adults will advance understanding on the developmental trajectory of color perception.