Texture discrimination: representation of orientation and luminance differences in cells of the cat striate cortex.

Neuronal texture discrimination in the cat striate cortex was investigated by measuring the responses of single cells to different pattern structures. The representation of two independent features, texture orientation and texture luminance, was analysed in detail and the sensitivity of neurones to either feature was studied at different levels of structure density. Texture patterns were systematically moved across the receptive field. From the cell response to various parts of the pattern, "response patterns" were generated which displayed the cell transform of the textured stimulus pattern. Only when texture structures were coarse, were cells able to encode the texture orientation of an area. Differences in texture luminance, on the other hand, were detected only in fine texture structures. Further, these textural features were processed in a different manner: Cells responded to differences in texture luminance but continuously to areas of similar texture orientation. Thus, responses of striate cells reveal an ambiguous representation of texture features and a failure to uniquely encode texture borders.