Cortical Maps of Separable Tuning Properties Predict Population Responses to Complex Visual Stimuli

In the earliest cortical stages of visual processing, a scene is represented in different functional domains selective for specific features. Maps of orientation and spatial frequency preference have been described in the primary visual cortex using simple sinusoidal grating stimuli. However, recent imaging experiments suggest that the maps of these two spatial parameters are not sufficient to describe patterns of activity in different orientation domains generated in response to complex, moving stimuli. A model of cortical organization is presented in which cortical temporal frequency tuning is superimposed on the maps of orientation and spatial frequency tuning. The maps of these three tuning properties are sufficient to describe the activity in orientation domains that have been measured in response to drifting complex images. The model also makes specific predictions about how moving images are represented in different spatial frequency domains. These results suggest that the tangential organization of primary visual cortex can be described by a set of maps of separable neuronal receptive field features including maps of orientation, spatial frequency, and temporal frequency tuning properties.