Dynamic changes in the tuning of striate neurons to the shapes of cross-shaped figures

Time slice analysis was used to study the dynamics of tuning to the shapes of cross-shaped figures flashing in the receptive fields of 83 neurons in the primary visual cortex (field 17) of the cat brain. Tuning was assessed in terms of the numbers of spikes in the overall response and its sequential 20-msec fragments. Only 11.7% of neurons produced reproducibly developing spike responses to a given shape (defined as the angle between the lines), i.e., had a preferred cross-shaped figure. In the remaining cases (88.3%), tuning of neurons to the shape of the cross showed dynamic changes. In 7.2% of cases, changes in the preferred shape of the cross occurred monophasically; changes were biphasic in 27.0% of cases, while in the remaining 54.1% of cases, the dynamics in changes in the preferred cross shape were undulatory. The tuning of receptive field zones is assessed as the cause of these effects and their difference from the previously observed dynamics of preferred orientations of single bars and cross-shaped figures; the functional significance of these effects is also discussed.