Are illusory visual phantoms seen by the motion system: Investigations utilizing the motion aftereffect

The constructive nature of motion perception has been highlighted in studies of the visual phantom illusion. Visual phantoms can occur when two low-contrast collinear drifting gratings are separated by a blank gap, leading to the ghostly impression of drifting stripes that extend through the gap. Although previous work has shown that phantom-inducing gratings can elicit a motion aftereffect (MAE) in the gap region, it is not known whether these MAEs arise from the perception of visual phantoms per se. Here, we evaluated the strength of MAEs elicited by phantom-inducing gratings and well-matched control stimuli. Either the darkest portion of the inducer gratings matched the background luminance to elicit more vivid phantoms or the mean luminance of the inducers matched the background as a control. Both phantom and control inducers predominantly evoked impressions of opposite-direction motion, but the dynamic MAE proved somewhat stronger for phantom than control inducers. Also, MAEs were more strongly modulated by the physical contrast of the control inducers and less influenced by the contrast of the phantom inducers. These findings suggest that low-level motion adaptation strongly contributes to the MAEs elicited in the gap region but that the magnitude of adaptation is further modulated by phantom perception.