Grant: Project Grant

Our rich and effortless perception of the complex mixtures of objects and surfaces comprising our everyday world is one of the most remarkable achievements of the human brain. A key early step in the required neural processing is separation of the retinal image into regions corresponding to distinct surfaces of different objects. In natural images we can effortlessly perform such "figure-ground segmentation" of borders defined by differences in a variety of local image properties, for example differences in luminance, colour, contrast, or texture. This segmentation process necessarily precedes higher-level visual functions such as object recognition, and is fundamentally important to normal visual perception. Analysis of complex visual patterns begins in the early visual cortex, areas V1 and V2. The responses of single neurons in these cortical areas are highly specific, or "tuned", to particular kinds of visual stimuli. An understanding of the nature of stimulus selectivity of these neurons forms a critical basis of our current understanding of human visual perception. This research program has three specific objectives: to evaluate and extend our recently discovered model of the neural circuitry for detecting luminance and texture boundaries in early visual cortex; to explore whether there might be two different kinds of such neural processing; and to examine the relationship to detection of colour boundaries. The outcomes of this work will yield fundamental, health-related knowledge that may facilitate the future design of diagnostic tests and therapies for visual disorders.