Early parallel processing of visual spatial information and its subsequent convergence in the visual pathway

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A spatial form (e.g. a bar) can be rendered visible if its interior differs sufficiently from its surroundings in any one of the following dimensions: brightness; colour; motion; texture; relative stereoscopic depth. In the everyday world several of these cues are often present simultaneously. It has long been known that (1) for brightness-defined form, an early stage in the temporal sequence of visual processing crudely analyzes the image at the back of the eye through parallel form detection mechanisms, each of which is selectively sensitive to a range of object sizes and orientations, and (2) that the just-noticeable difference in size and orientation is far smaller than the bandwidths of these early detection mechanisms.We published experimental evidence that these just-noticeable differences are small because they are determined by the relative activity across the early detection mechanisms.We have found that, for spatial form that is rendered visible by relative motion, or texture difference or relative depth, just-noticeable differences in orientation, size and shape are surprisingly small and not greatly different for the three kinds of form. The proposed research is to find (1) whether just noticeable differences in size, orientation and shape for spatial form that is rendered visible by relative motion or by texture are also determined by the relative activity across detection mechanisms for the relevant kind of spatial form, and (2) the extent to which information about size, orientation and shape for different kinds of spatial form is pooled before the visual processing stage at which a just-noticeable difference in size, orientation or shape is computed. I envisage that the proposed research will extend current understanding of our ability to see objects and to distinguish one object from another, and that this new understanding will lead to improvements in the design of visual displays in flight simulators used to train commercial pilots.