Adaptive matched filtering in peripheral nervous system

It is known that the spatial visual receptive fields of fly lamina cells are influenced by the mean level of luminance such that the inhibitory regions flanking the central excitatory maximum are lost on lowering luminance. At the same time, the biphasic temporal response of the 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/m²) 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 for the center of a uniform region. The authors describe this theory and its behavioral corroboration in walking flies (Lucilia cuprina)