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Greg Appelbaum, Alex Wade, Mark Pettet, Vladimir Vildavski, Anthony M. Norcia; Dynamics of texture segmentation. Journal of Vision 2005;5(12):12. doi: 10.1167/5.12.12.
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© ARVO (1962-2015); The Authors (2016-present)
The segmentation of visual images into coherent objects and their surrounds is a fundamental process of the early visual system. To assess the role of local boundary cues in figure-ground segmentation, we constructed displays in which figure and background regions were separately ‘tagged’ with periodic modulations of their texture orientations or phase (relative alignment). Tagging allowed us to monitor figure and background responses separately and to study non-linear interactions between them as a function of segmentation cue and retinotopic location. Steady-state visually evoked potentials (SSVEPs) were recorded over 128 channels as subjects passively viewed the stimuli. Distributed source modeling was performed based on individual head models and cortical current density distributions were plotted in relationship to visual areas defined by fMRI retinotopic maps. SSVEP responses at harmonics of the figure tag-frequency were maximal over lateral regions of the occipital cortex, while harmonic responses of the background tag-frequency were restricted to the midline occipital pole. These responses were typically cue and retinotopically invariant. Responses at frequencies equal to low-order sums and differences of the tag frequencies, resulting from non-linear interactions occurring between the figure and background regions, were both cue and retinotopically dependent.
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