title: Separating fusion from rivalry.
abstract: Visual fusion is the process in which differing but compatible binocular information is transformed into a unified percept. Even though this is at the basis of binocular vision, the underlying neural processes are, as yet, poorly understood. In our study we therefore aimed to investigate neural correlates of visual fusion. To this end, we presented binocularly compatible, fusible (BF), and incompatible, rivaling (BR) stimuli, as well as an intermediate stimulus type containing both binocularly fusible and monocular, incompatible elements (BFR). Comparing BFR stimuli with BF and BR stimuli, respectively, we were able to disentangle brain responses associated with either visual fusion or rivalry. By means of functional magnetic resonance imaging, we measured brain responses to these stimulus classes in the visual cortex, and investigated them in detail at various retinal eccentricities. Compared with BF stimuli, the response to BFR stimuli was elevated in visual cortical areas V1 and V2, but not in V3 and V4 - implying that the response to monocular stimulus features decreased from V1 to V4. Compared to BR stimuli, the response to BFR stimuli decreased with increasing eccentricity, specifically within V3 and V4. Taken together, it seems that although the processing of exclusively monocular information decreases from V1 to V4, the processing of binocularly fused information increases from earlier to later visual areas. Our findings suggest the presence of an inhibitory neural mechanism which, depending on the presence of fusion, acts differently on the processing of monocular information.
authors: Department of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
authors: Stefan M
authors: SM
authors: Kallenberger
authors: Department of Medical Psychology and Medical Sociology, Georg-August-Universität Göttingen, Göttingen, Germany.
authors: Constanze
authors: C
authors: Schmidt
authors: Department of Cognitive Neurology, Georg-August-Universität Göttingen, Göttingen, Germany.
authors: Peter
authors: P
authors: Dechent
authors: Department of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
authors: Clemens
authors: C
authors: Forster
authors: Department of Medical Psychology and Medical Sociology, Georg-August-Universität Göttingen, Göttingen, Germany.
authors: Nicole
authors: N
authors: von Steinbüchel
authors: Department of Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, Charité Campus Mitte, Berlin, Germany.
authors: Torsten
authors: T
authors: Wüstenberg
authors: Department of Medical Psychology and Medical Sociology, Georg-August-Universität Göttingen, Göttingen, Germany; Institute of Medical Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.
authors: Hans
authors: H
authors: Strasburger
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation; D015357:Vision Disparity; D015348:Vision, Binocular; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception; D055815:Young Adult