Neuronal responses to orientation and motion contrast in cat striate cortex

Responses of striate neurons to line textures were investigated in anesthet ized and paralyzed adult cars. Light bars centered over the excitatory rece ptive field (RF) were presented with different texture surrounds composed o f many similar bars. In two test series, responses of 169 neurons to textur es with orientation contrast (surrounding bars orthogonal to the center bar ) or motion contrast (surrounding bars moving opposite to the center bar) w ere compared to the responses to the corresponding uniform texture conditio ns (all lines parallel, coherent motion) and to the center bar alone. In th e majority of neurons center bar responses were suppressed by the texture s urrounds. Two main effects were found. Some neurons were generally suppress ed by either texture surround. Other neurons were less suppressed by textur e displaying orientation or motion (i.e. feature) contrast than by the resp ective uniform texture, so that their responses to orientation or motion co ntrast appeared to be relatively enhanced (preference for feature contrast) . General suppression was obtained in 33% of neurons tested for orientation and in 19% of neurons tested for motion. Preference for orientation or mot ion contrast was obtained in 22% and 34% of the neurons, respectively, and was also seen in the mean response of the population. One hundred nineteen neurons were studied in both orientation and motion tests. General suppress ion was correlated across the orientation and motion dimension, but not pre ference for feature contrast. We also distinguished modulatory effects from end-zones and flanks using butterfly-configured texture patterns. Both reg ions contributed to the generally suppressive effects. Preference for orien tation or motion contrast was not generated from either end-zones or flanks exclusively. Neurons with preference for feature contrast may form the phy siological basis of the perceptual saliency of pop-out elements in line tex tures, If so, pop-out of motion and pop-out of orientation would be encoded in different pools of neurons at the level of striate cortex.