Abstract

One of the parameters that describes the spatial properties of cells in the mammalian visual cortex is the spatial-frequency bandwidth. Although there is some variation in the range of tuning (0.5–2.5 octaves), the physiological evidence supports the notion that the bandwidths of cortical cells increase as the peak sensitivity increases in spatial frequency; the bandwidths are roughly constant (in octaves) on a log-frequency axis. This study looks into the possible reasons for this type of representation in the mammalian system. One suggestion is that octave-wide bandwidths allow for an equal distribution of activity throughout the sensors of the code. This can be shown to be true for channels with equal peak sensitivities and images with amplitude spectra of 1/f-However, there are a number of ways to produce this equal distribution other than by octave-wide codes. In this study, a second possibility was explored. By using a Gabor-like code and a variety of calibrated natural scenes, statistical properties were described in terms of a space versus frequency representation. In such a representation, features in natural images (local regions where the phases are correlated) become spatially smaller and broader in spatial frequency with increasing frequency. This is not a necessary property of scenes in general, and some images will be described that do not show this property. Such images may be more effectively represented by codes that do not show octave-wide bandwidths.

© 1990 Optical Society of America