Abstract
PURPOSE: Retinal stimulation is required for afterimages but mechanisms beyond the retina are involved in afterimage formation. Recent evidence suggests that percepts (not merely visual stimuli) during adaptation can influence the afterimage (Gilroy & Blake, Current Biology, 2005). Binocular color rivalry was used here to investigate the relation between percepts during adaptation and the percepts of afterimages. This method provides constant retinal stimulation while the percept of the stimuli changes over time.
METHOD: Perceptual alternation was measured for two dichoptically presented, chromatically rivalrous gratings. The gratings were equiluminant so observers would experience perceptual misbinding of color to form during adaptation (Hong & Shevell, VSS 2005). In a control condition the gratings had luminance contrast, which eliminated perceptual color misbinding. Following the rivalrous adaptation, a uniform achromatic field was presented and the observer's percepts of the afterimage were reported using a computer's button pad.
RESULTS: Color misbinding in the afterimage was experienced following adaptation to the equiluminant gratings. The percept with misbound color was dominant during adaptation but was not the dominant afterimage. In the control condition, no misbinding was experienced during adaptation or in the afterimage.
DISCUSSION: The measurements showed that color misbinding was experienced in the afterimage only when rivalrous chromatic gratings during adaptation resulted in misbinding. Two possible explanations are that the afterimage with color misbinding results (1) directly from the misbound percept during adaptation or (2) from a neural process of color-form (mis)binding that follows monocular neural representations of an afterimage.
Supported by PHS grant EY-04802