Model studies of the mechanisms of tuning of visual cortex neurons to incomplete cross-shaped figures.

Numerical simulation modeling of the receptive fields of visual cortex neurons able to detect cross-shaped figures with masked central or peripheral areas was performed. Receptive field models of two types were considered: those with antagonistic and cooperative interactions between the center and the periphery. Model neurons with receptive fields with reciprocal (antagonistic) interactions produced greater responses to peripheral or central crosses than to complete crosses. Studies using the model showed that the basis of this type of tuning could be provided by a disinhibition mechanism: blockade of the inhibitory zones in the center or periphery of the receptive field by activation of a lateral disinhibitory zone. A model with cooperative interactions between the center and periphery of the receptive field was also studied, in which responses to complete crosses were summed from the responses to the peripheral and central parts. Tuning of these model receptive fields was comparable to the sensitivity of real visual cortex neurons to the shape, size, and orientation of figures. The properties of model receptive fields (configuration, localization, and weightings of the various zones) allowing simulation of the properties of cat visual cortex field 17 neurons sensitive to the orientation and configuration of incomplete cross-shaped figures were identified.