Visual processing of contours and textures

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This application is for funds to continue my research into the visual processing of contours and textures. Being able to process the shapes of contours, such as a curved outline of a pear, as well as textures, such as the surface of a folded carpet, is an essential part of our ability to recognize objects and the shapes of surfaces in the visual world. My experiments involve human test subjects viewing large numbers of specially-designed computer-generated test patterns presented on a display monitor and making judgements about them. The particular experimental method I current employ is the 'visual after-effect'. Prolonged viewing, termed 'adaptation', of a particular contour/texture shape causes other contour/texture shapes to appear distorted. By measuring the amount of distortion, a great deal can be learnt about how the brain processes contour/texture shapes. For example, if one takes a simple curved contour and adapts to it, a slightly more curved contour appears even more curved than otherwise. This effect is termed the 'curvature after-effect', and the fact that it happens at all tells us that there are neurons in the brain that are specialized for seeing curves. Thus the curvature after-effect can be used to uncover the details of how the brain sees curves. To take one example of how it can do this, my lab has shown that if the adaptation and test curves are a different colour the curvature after-effect is much reduced (i.e. there is less distortion) compared to if they are the same colour. This tells us that the neurons in the brain that detect curves are 'tuned' for colour, in other words some neurons respond to red curves, some green curves, some blue curves etc. Together with other experiments, my research therefore leads to a better understanding of how the brain sees the shapes of contours and textures.