Spatial frequency characteristics of nearby neurons in cats' visual cortex.

Various methods have allowed mapping of responses to several stimulus features on the cortical surface, particularly edge orientation and motion direction. The cortical mapping of spatial frequencies (SF), which is the basic property that leads to perception of spatial details of visual objects, is still controversial. We recorded simultaneously extracellular action potentials from neighboring cells in superficial layers of the area 17-18 border region of anesthetized cats. Responses of nearby cells to sine-wave gratings of varying SF were analyzed. Spatial frequency tuning curves were cross-correlated to establish the degree of similarity between the curves and optimal SFs were compared for each pair of neurons. The investigation showed that only about a half of nearby neurons exhibited close optimal SFs and similar tuning curves. The results suggest that SF channels do not show a clear clustering within a small pool of neurons. Such organization may contribute to the perception of spatial details at all orientations and motion directions.