Neural Circuits Implicated in Long-range Color Filling-in

Kenneth knoblauch, PhD: Université Claude Bernard, Lyon 1, Inserm U 1208, Stem-cell and Brain Research Institute, Building the cerebral cortex:  Connectomics, Bron, France and Faculty of Health and Social Sciences, Department of Optometry, Radiography and Lighting Design, University Southeastern Norway, Oslo, Norway

 Visual illusions—defined as deviations between what we expect the observer to perceive based on the stimulus and what is actually perceived—are frequently used to probe visual mechanisms.  In a general sense, analyzing stimulus features that induce illusions focuses only on bottom-up processing while the violation of expectation aspect relates more to built-in assumptions implicit to visual perception.  I will describe a series of psychophysical experiments in which we quantified optimal stimulus features to induce a long-range, color filling-In phenomenon called the watercolor effect.  This evidence suggests the phenomenon requires processing over multiple levels along the visual hierarchy.  We also investigated the neural substrate of the phenomenon using functional imagery.  Here, the evidence implicates an interaction between extrastriate cortical areas in both dorsal and ventral streams and feedback to earlier visual areas.  Since feedforward/feedback processes are established through layer-specific cortical projections, further insight as to the mechanisms underlying this phenomenon would benefit from studies using laminar resolution imaging.