Figure 2
From: Invisible noise obscures visible signal in insect motion detection
Spatiotemporal filter and opponent energy tuning in an opponent motion model. (A,B) Fourier spectra of rightward and leftward energies ((A + B′)2 + (A′ − B)2, Equation 6, and (A − B′)2 + (A′ + B)2, Equation 7) for example mammalian and insect opponent energy motion detectors (see Methods for details, Equations 18–22). The colored lines in each plot are 0.25 sensitivity contours. The Fourier spectra of leftward and rightward energies are very similar to the model’s filters in each case: spatially bandpass in mammals and low-pass in insects. (C,D) Opponent energy, AB′ − A′B, computed as the difference between rightward and leftward energies. In mammals, rightward and leftward responses do not overlap because the spatial filter are band-pass (panel A). In insects, the low-pass spatial filters cause an overlap between rightward and leftward responses (panel B) but this overlap is canceled at the opponency stage making opponent energy insensitive to low spatial frequencies (panel D).
