Matched filter theory applied to responses of fly lamina cells predicts loss of edge-preference on lowering luminance

The biphasic temporal response of fly lamina cells becomes monophasic on lowering luminance. For a moving edge stimulus, this implies that the spatial integration by the lamina cell yields a temporal waveform which has the same features as the waveform of the temporal response of the lamina cell to an impulse of light, at high levels of luminance. In other words, the temporal waveform generated by the moving edge is matched to the temporal waveform most preferred by the lamina cell, and, as predicted by the matched filter theory, the stimulus causing the largest amplitude response at high (above 1 cd/m ²) levels of luminance is the edge. On lowering luminance, the matched filter theory predicts that the now monophasic nature of the spatial and temporal responses of the lamina gives a preference not for the edges but the center of a uniform region. This theory and its behavioral corroboration in walking flies (Lucilia cuprina) are described