title: Directional selectivity and its use in early visual processing.
abstract: The construction of directionally selective units, and their use in the processing of visual motion, are considered. The zero crossings of delta 2G (x,y) * I(x,y) are located, as in Marr & Hildreth (1980). That is, the image is filtered through centre-surround receptive fields, and the zero values in the output are found. In addition, the time derivative delta[delta 2G(x,y) * I(x,y)]/delta t is measured at the zero crossings, and serves to constrain the local direction of motion to within 180 degrees. The direction of motion can be determined in a second stage, for example by combining the local constraints. The second part of the paper suggests a specific model of the information processing by the X and Y cells of the retina and lateral geniculate nucleus, and certain classes of cortical simple cells. A number of psychophysical and neurophysiological predictions are derived from the theory.
mesh_terms: D000818:Animals; D005829:Geniculate Bodies / Q000502:physiology; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D012160:Retina / Q000502:physiology; D013028:Space Perception; D014785:Vision, Ocular; D014793:Visual Cortex / Q000502:physiology; D014796:Visual Perception