title: Cortical mechanisms for afterimage formation: evidence from interocular grouping.
abstract: Whether the retinal process alone or retinal and cortical processes jointly determine afterimage (AI) formation has long been debated. Based on the retinal rebound responses, recent work proposes that afterimage signals are exclusively generated in the retina, although later modified by cortical mechanisms. We tested this notion with the method of "indirect proof". Each eye was presented with a 2-by-2 checkerboard of horizontal and vertical grating patches. Each corresponding patch of the two checkerboards was perpendicular to each other, which produces binocular rivalry, and can generate percepts ranging from complete interocular grouping to either monocular pattern. The monocular percepts became more frequent with higher contrast. Due to adaptation, the visual system is less sensitive during the AIs than during the inductions with AI-similar contrast. If the retina is the only origin of AIs, comparable contrast appearance would require stronger retinal signals in the AIs than in the inductions, thus leading to more frequent monocular percepts in the AIs than in the inductions. Surprisingly, subjects saw the fully coherent stripes significantly more often in AIs. Our results thus contradict the retinal generation notion, and suggest that in addition to the retina, cortex is directly involved in the generation of AI signals.
authors.affiliation: CAS Key Laboratory of Behavioral Science, Institute of Psychology, Beijing 100101, P.R. China.|University of Chinese Academy of Sciences, Beijing 100101, P.R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Dong
authors.affiliation: Department of Psychology, Umeå University, S-901 87 Umeå, Sweden.
authors.forename: Linus
authors.initials: L
authors.lastname: Holm
authors.affiliation: CAS Key Laboratory of Behavioral Science, Institute of Psychology, Beijing 100101, P.R. China.
authors.forename: Min
authors.initials: M
authors.lastname: Bao
mesh_terms: D000328:Adult; D000360:Afterimage / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology*; D015348:Vision, Binocular / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult