S. Yasui, T. Furukawa, M. Yamada, T. Saito
Despite the phylogenic and structural differences, the visual sys(cid:173) tems of different species, whether vertebrate or invertebrate, share certain functional properties. The center-surround opponent recep(cid:173) tive field (CSRF) mechanism represents one such example. Here, analogous CSRFs are shown to be formed in an artificial neural network which learns to localize contours (edges) of the luminance difference. Furthermore, when the input pattern is corrupted by a background noise, the CSRFs of the hidden units becomes shal(cid:173) lower and broader with decrease of the signal-to-noise ratio (SNR). The same kind of SNR-dependent plasticity is present in the CSRF of real visual neurons; in bipolar cells of the carp retina as is shown here experimentally, as well as in large monopolar cells of the fly compound eye as was described by others. Also, analogous SNR(cid:173) dependent plasticity is shown to be present in the biphasic flash responses (BPFR) of these artificial and biological visual systems . Thus, the spatial (CSRF) and temporal (BPFR) filtering proper(cid:173) ties with which a wide variety of creatures see the world appear to be optimized for detectability of changes in space and time.