title: The chromatic input to global motion perception.
abstract: For over 30 years there has been a controversy over whether color-defined motion can be perceived by the human visual system. Some results suggest that there is no chromatic motion mechanism at all, whereas others do find evidence for a purely chromatic motion mechanism. Here we examine the chromatic input to global motion processing for a range of color directions in the photopic luminance range. We measure contrast thresholds for global motion identification and simple detection using sparse random-dot kinematograms. The results show a discrepancy between the two chromatic axes: whereas it is possible for observers to perform the global motion task for stimuli modulated along the red-green axis, we could not assess the contrast threshold required for stimuli modulated along the yellowish-violet axis. The contrast required for detection for both axes, however, are well below the contrasts required for global motion identification. We conclude that there is a significant red-green input to global motion processing providing further evidence for the involvement of the parvocellular pathway. The lack of S-cone input to global motion processing suggests that the koniocellular pathway mediates the detection but not the processing of complex motion for our parameter range.
authors.affiliation: Eleanor Rathbone Building, Department of Psychology, University of Liverpool, Liverpool, L69 7ZA, UK. air@liv.ac.uk
authors.forename: Alexa I
authors.initials: AI
authors.lastname: Ruppertsberg
authors.forename: Sophie M
authors.initials: SM
authors.lastname: Wuerger
authors.forename: Marco
authors.initials: M
authors.lastname: Bertamini
mesh_terms: D016477:Artifacts; D003116:Color; D003118:Color Perception / Q000502:physiology*; D015350:Contrast Sensitivity; D006801:Humans; D008027:Light; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D012684:Sensory Thresholds; D014796:Visual Perception / Q000502:physiology*