Local spectral analysis in the visual cortex.

On the basis of experimental evidence presented earlier a model of local spectral analysis of the image performed by the complex receptive fields of the visual cortex has been proposed. An essential feature of the model is that the generalized piece-wise Fourier transform is performed not over the image luminance function but over the logarithm contrast function resulted from analysis of the image by the round receptive fields of the preceding levels. Such an assumption removes a number of experimental objections offered against the hypothesis of two-dimensional Fourier transform in the visual system. The consequences from the piece-wise expansion in a series of basic functions have been considered and among them: the channel frequency characteristics which can have more than one maximum; the possibility of describing the image by a limited number of channels with overlapping frequency characteristics; the existence of mechanisms for estimation of phase shift between frequencies.