The graph displays spatial activity patterns predicted from a computational model of optic flow processing in the visual system of a housefly. The upper plots depict patterns of local response amplitudes within four retinotopic arrays of motion detector circuits that have small spatial receptive fields. Each motion detector is sensitive to the local direction and speed of motion inputs to the retina as a fly moves through the air. The four motion detector arrays all share the same overall spatial receptive field, which is the circular region outlined in the plots. Individual motion detectors are excited maximally by rightward, leftward, upward or downward motion, and all motion detectors in a given array have the same preferred direction (arrows).
The motion detector outputs are filtered through a synaptic connection matrix and then summed by a model collator neuron. The pattern of synaptic connections is one that promotes sensitivity to centered, clockwise rotation. In the two examples shown here, the network was stimulated by a clockwise rotational flow field positioned at the center (C) or the left edge (E) of the receptive field. The lower plots (S) show the pattern of summed outputs from the four detector arrays, and predict spatial activity patterns with the dendritic tree of a wide-receptive-field neuron that collates responses of the small-field motion detectors. The output color code is normalized to the maximum (red)
and minimum (blue) summed output amplitudes.
This graph was submitted by John Douglass, Arizona Research Laboratories Division of Neurobiology at the University of Arizona, Tucson, AZ.