Orientation-dependent binocular interactions in area 21a of the cat.

We investigated binocular interactions in area 21a cells of the anaesthetized cat. Visual stimuli were drifting sinusoidal gratings presented at the same optimal orientation in each eye (iso-oriented condition) or at the optimal orientation in the dominant eye and the orthogonal orientation in the other eye (orthogonal condition). In 68% of cells the response in the binocular iso-oriented condition was greater than the dominant eye monocular response, while in 88% of cells the response in the binocular orthogonal condition was less than the dominant eye monocular response. Our results suggest a possible role for this extrastriate region of cortex in binocular contour rivalry.