Hemispheric asymmetry of chromatic motion perception

The present study investigated hemispheric symmetry of cortical functions, in terms of the chromatic motion mechanism. A series of experiments examined the visual sensitivities to chromatic and achromatic stimuli with or without motion, presented in either of the two (left or right) visual hemifields. Experiment 1 measured, individually, the subjective isoluminance of red/green stimuli for each visual field. Experiment 2 examined the visual field differences of the detection thresholds for static stimuli with the isoluminant color contrast and achromatic luminance contrast. Subsequent experiments measured contrast thresholds for motion detection (Experiment 3) and motion direction discrimination (Experiment 4) with both chromatic and achromatic stimuli. No visual field differences between thresholds were found in Experiments 1 and 2, whereas in Experiments 3 and 4, thresholds for the chromatic conditions were found to be lower in the left than in the right visual field, suggesting functional lateralization of the early motion mechanism with chromatic information in motion detection and direction discrimination.