Grant: Discovery Grants Program - Individual

We rely on vision to guide our actions. As there is more information available to the eyes than the brain can process simultaneously, our visual system is said to have limited capacity. To overcome this bottleneck, the brain has mechanisms to preferentially process a subset of the visual information. One such process is surface-based selection, which has been shown to select one of two overlapping transparent surfaces. For example, when driving a car, the driver attends to the road in front of car instead of the windshield with bugs or dirt on it, even though the dirty windshield shares the same field of view.   The aim of this proposal is to elucidate the mechanisms of surface-based selection. The first set of experiments investigates how different stimulus characteristics modulate surface-based selection.  These experiments will constrain the mechanism(s) of surface-based selection by determining which characteristics can modulate it. Knowing these boundary conditions will help determine the locus of selection and the earliest stage(s) at which this selection is occurring.   The second set of experiments determines whether the characteristics that modulate surface-based selection work in parallel or are part of the same mechanism. This would test whether combining characteristics has an additive, multiplicative or no additional influence on selection. Different characteristics may have different relationships with each other. The results will facilitate modeling the relative contributions of different characteristics on surface representations and surface-based selection. Thus, the experiments will constrain the possible physiological mechanisms giving rise to selection.   A better understanding of surface-based selection and surface representation will lead to an increase in our knowledge of how basic features are bound together into an object. The results will also have implications for a variety of neurological disorders linked to attention and object-processing, such as autism and schizophrenia.