Figure 1.

Properties of correlation-type elementary movement detectors (EMDs). (A) Structure of a basic variant of three neighboring movement detectors including peripheral filtering (PF) in the input lines; signals from each receptor are delayed via the phase delay of a temporal first-order low-pass filter, multiplied and half-wave rectified; spatial pooling of signals in accomplished by the output element Z (left); a two-dimensional EMD array consisting of EMDs most sensitive to horizontal and vertical motion, respectively (right). (B) Time course of pattern-dependent response modulations of model cell that pools the responses of an array of EMDs with horizontal preferred direction. The spatial sensitivity distribution of the model cell is given by the weight field shown in the inset. The brighter the gray level the larger the local weight of the corresponding EMDs and, thus, the spatial sensitivity. The frontal equatorial viewing direction is at 0° azimuth and 0° elevation. The model cell was stimulated by horizontal constant velocity motion of the panoramic high dynamic range image shown in (C). (D) Logarithmic color coded standard deviation of the mean pattern-dependent modulation for one-dimensional receptive fields differing in vertical receptor position and azimuthal receptive field size (# of receptors included horizontally). The pattern-dependent modulation amplitude decreases with horizontal receptive field extent. They depend on the contrast distribution of the input image, as can be seen, when comparing pattern-dependent modulation amplitudes corresponding to the different elevations of the input image. (Data from Meyer et al., 2011).