2006; Scholte et al. 2006; but see Ito and Gilbert 1999) and might even guide attentional recourses (Qiu et al. 2007). In this perspective, figure–ground segregation could actually
pave the way for prioritizing regions of a visual scene which attention can assign for deeper processing. Thus, if stack–frame differences were caused by attention, these effects would still be depending on the framework generated by figure–ground segregation. Form from motion Classically, it is thought that in stimuli like we used in this study, processing proceeds from motion detection via local motion detectors (e.g., direction selective cells in V1, V3, or middle temporal [MT]), via the detection of motion Inhibitors,research,lifescience,medical discontinuities, or motion-defined borders (via opponent motion-sensitive cells, for Inhibitors,research,lifescience,medical example, in MT see Movshon et al. 1985; Stoner and Albright 1992) to mechanisms that are selective for motion-defined shapes (e.g., kinetic shape-selective cells in inferior temporal cortex [IT], see Sary et al. 1993). Our experiment was designed so that stack versus frame stimuli were identical with respect to these three stages of processing: on average local motion is identical, stimuli contain the same research amount of motion discontinuities, and these motion discontinuities define the same shapes Inhibitors,research,lifescience,medical (rectangles). Their only difference lies in
the manner in which filling processes Inhibitors,research,lifescience,medical proceed over these rectangles: in frame stimuli the interior rectangle is “grouped” with the background, and the frame stands out as a different surface, whereas in stack stimuli the interior rectangle fills in as a separate surface. We find, in accordance with earlier results (Scholte
et al. 2008), that these different ways of filling in the rectangles Inhibitors,research,lifescience,medical find their neural correlates in relative late cortical processing, the way beyond the timing of the three steps described above. This is probably due to the fact that these three stages are mediated by rapid feedforward sweep processing (Lamme and Roelfsema 2000), whereas the filling in is mediated by re-entrant processing mediated by horizontal and feedback connections. As a consequence, shape (or mafosfamide form) from motion occurs before filling in, yet we designed our stimuli so that from the perspective of motion-defined shape (form from motion) mechanisms, the stack and frame stimuli are comparable, and hence, a form from motion versus no-form from motion differences cannot explain our results. Late activity in early visual cortex When visual information is initially processed by means of feedforward activation, in the right setting, this information can elicit activity throughout the brain, even reaching the highest levels of the cortical hierarchy (Dehaene et al. 2006; Lau and Passingham 2007; Nakamura et al. 2007; van Gaal et al. 2010; Wokke et al. 2011). As visual information travels upstream, neural responses become increasingly more complex.