Abstract
The segregated pathway hypothesis has been challenged by observations on interactions between the different visual pathways. This is particularly true for the input of chromatic signals into the motion system. However, it is not clear whether this reflects a true co-processing of colour and motion, or whether it is the result of a net-chromatic population-response of motion sensitive neurons. In these experiments, I used chromatic adaptation as a means of testing chromatic processing of moving stimuli. The test stimuli were produced on a calibrated colour monitor. The adaptation pattern consisted of a 2×2 patch (test; L = 19.3 cd/m) presented in front of a checkerboard background (20×20 ; L1 = 28.3 cd/m; L2 = 10.3 cd/m). The stimuli were achromatic in the standard condition (u′= 0.197, v′=0.468). In the adaptation condition, the chromaticity of the entire pattern was shifted by a specific amount (? E*uv = 22.18) along an equiluminant L/M axis (u′= 0.166; v′= 0.472); a perceptual shift towards green. Chromatic adaptation (t = 5s) was measured by a hue cancellation method. Four conditions were tested (1) test and background static, (2) background and test moving at same speed, (3) test moving in front of a static background, and (4) test static, fixation point moving across the background. Velocity of motion in all experiments was constant and 0.04 m/s. Four subjects participated in the experiments. Chromatic adaptation in the “all-in-motion” condition was similar to that observed in the static condition. In the “relative motion” condition, however, adaptation was significantly enhanced (P<0.01). In experiment (4), a control for the effect of eye movements, adaptation was reduced. The results indicate the presence of chromatic processing in motion, whereby relative motion even facilitates chromatic adaptation. This suggests that colour and motion of a stimulus are processed in close cooperation, exceeding the effects of a residual chromatic sensitivity of motion sensitive cells.
Supported by DFG grant (We 1710 1/1) and the fortune programme (Faculty of Medicine, University of Tuebingen, grant # 1059-0-0).