[Receptive fields of the visual cortex--detectors or filters of spatial frequencies?].

Spatial frequency characteristics of the complex cortical visual receptive field were studied in curarized cats. It is shown that, besides the main maximum, they also have additional maxima and negative regions as predicted by the theory of piecewise Fourier-analysis. Comparison of responses of the complex receptive field to sinusoidal grating entering the field completely or incompletely together with the comparison of responses to sinusoidal and squarewave gratings shows the linear properties of the receptive field as a spatial frequency filter. The response of the complex receptive field increases with the number of periods constituting the sinusoidal grating. Several periods of optimal spatial frequency matched the size of the complex receptive field. In the columns of neurons, the receptive fields were found tuned to a broad band of spatial frequencies. The data confirm the hypothesis according to which the complex receptive fields are rather spatial frequency filters than detectors.