Binocular interaction in the visual cortex of awake cats

Summary The effect of monocular and binocular stimulation on cortical neurons of area 17 was investigated in awake unparalyzed cats with painless head fixation. Two types of stimuli were applied: Stationary gratings of variable orientations, and a 3° wide dark stripe at different orientation and moving in different directions. All neurons which were excited from both eyes showed qualitatively similar input properties (orientation specificity, movement and/or direction sensitivity). Quantitatively, the input from both eyes was either equal or dominant from one eye. Contralateral dominance was found 5 times more frequently than ipsilateral dominance. Various types of binocular interaction were found. Some neurons showed an excitatory response from one eye and inhibitory response from the other (inhibition, 14% of our units), and others showed a response during binocular stimulation which was equal to the sum of the monocular responses (summation, 18%), larger (facilitation, 43%) or smaller (occlusion, 14%) than the sum of the two monocular responses. A few units with binocular responses did not respond to monocular stimulation of one or both eyes. The results are compared with those found by other authors in paralyzed and anesthetized animals, and current theories of neuronal mechanisms of binocular vision are discussed in the context of our findings.This work was supported by the Deutsche Forschungsgemeinschaft as a research project in the Sonderforschungsbereich Kybernetik (SFB 31).Dr. R.B. Freeman, jr. was supported by NIH-grant 363-93600-21, MF-428-69 during the period of this research.