Noise masking of S-cone increments and decrements.
S-cone increment and decrement detection thresholds were measured in the presence of bipolar, dynamic noise masks. Noise chromaticities were the L-, M-, and S-cone directions, as well as L-M, L+M, and achromatic (L+M+S) directions. Noise contrast power was varied to measure threshold Energy versus Noise (EvN) functions. S+ and S- thresholds were similarly, and weakly, raised by achromatic noise. However, S+ thresholds were much more elevated by S, L+M, L-M, L- and M-cone noises than were S- thresholds, even though the noises consisted of two symmetric chromatic polarities of equal contrast power. A linear cone combination model accounts for the overall pattern of masking of a single test polarity well. L and M cones have opposite signs in their effects upon raising S+ and S- thresholds. The results strongly indicate that the psychophysical mechanisms responsible for S+ and S- detection, presumably based on S-ON and S-OFF pathways, are distinct, unipolar mechanisms, and that they have different spatiotemporal sampling characteristics, or contrast gains, or both.
Psychology Department, Northeastern University, Boston, MA, USA.
Quanhong
Q
Wang
Psychology Department, Northeastern University, Boston, MA, USA.
David P
DP
Richters
Psychology Department, Northeastern University, Boston, MA, USA.
Rhea T
RT
Eskew
D003118:Color Perception / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D009622:Noise; D010470:Perceptual Masking / Q000502:physiology*; D011601:Psychophysics; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology*
S cone; chromatic detection; chromatic noise; color mechanisms; increment/decrement; on/off