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Sandra Veser, Urte Roeber, Erich Schröger; Percept-dependent modulations of neuronal activity occur earlier for shape than for colour stimuli. Journal of Vision 2007;7(9):371. doi: https://doi.org/10.1167/7.9.371.
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© ARVO (1962-2015); The Authors (2016-present)
Binocular rivalry occurs when dissimilar images are presented to the two eyes. That is, at one time only a single image is perceived while the other is suppressed. Hierarchical models claim that binocular rivalry can occur at different levels within the visual process. In this study, we compared the time course of percept-dependent neural responses between a condition with stimuli of different colours and a condition with stimuli of different shapes. Equiluminant red/black or green/black radial frequency patterns of different shapes were presented dichoptically. Rivalling stimuli either differed in colour but had the same shape (report-perceived-colour task) or differed in shape but had the same colour (report-perceived-shape task). We measured event-related brain potentials (ERPs) following transitions from rivalling to non-rivalling stimulation. Depending on the prevailing percept reported by the observer, these transitions could concern the eye that was dominant (incompatible change) or suppressed (compatible change). Our results show that the first percept-dependent modulation of the ERP following shape rivalry occurs earlier (around 120 ms, P1-range) than the first percept-dependent modulation following colour rivalry (around 230 ms, N1-range). In both cases, incompatible changes elicited larger amplitudes than compatible changes. In conclusion, stimulus features determine the stage of percept-dependent processing of visual stimuli with shape-based processing being influenced earlier than colour-based processing.
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