title: 1/f Noise in human color vision: the role of S-cone signals.
abstract: We examine the functional role of S-cone signals on reaction time (RT) variability in human color vision. Stimuli were selected along red-green and blue-yellow cardinal directions and at random directions in the isoluminant plane of the color space. Trial-to-trial RT variability was not statistically independent but correlated across experimental conditions and exhibited 1/f noise spectra with an exponent close to unity in most of the cases. Regarding contrast coding, 1/f noise for random chromatic stimuli at isoluminance was similar to that for achromatic stimuli, thus suggesting that S-cone signals reduce variability of higher order color mechanisms. If we regard spatial coding, the effect of S-cone density in the retina on RT variability was investigated. The magnitude of 1/f noise at 16 min of arc (S-cone free zone) was higher than at 90 min of arc in the blue-yellow channel, and it was similar for the red-green channel. The results suggest that S-cone signals are beneficial and they modulate 1/f noise spectra at postreceptoral stages. The implications related to random multiplicative processes as a possible source of 1/f noise and the optimal information processing in color vision are discussed.
authors.affiliation: Center for Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal. jmanuel@fisica.uminho.pt
authors.forename: José M
authors.initials: JM
authors.lastname: Medina
authors.forename: José A
authors.initials: JA
authors.lastname: Díaz
mesh_terms: D003116:Color; D055253:Color Vision / Q000502:physiology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology*