In sixty-five complex cells recorded from striate cortex of lightly anaesthetized, paralysed cats we investigated directional selectivity for motion of oriented and textured stimuli, both alone and when moving simultaneously in the same direction and at the same velocity. Monocular comparisons were made over a range of velocities for the dominant eye in all cells, and for the other eye in fourteen instances. For oriented stimuli, response magnitude varied with velocity, but preferred directions(s) and sharpness of tuning remained constant. For background texture motion, directional selectivity was typically unimodal at low velocities, but became increasingly bimodal at high velocities: a trough of depressed response (in directions optimal for oriented stimuli) separated two progressively more widely disparate preferred directions. Preferred velocity and velocity bandpass were typically higher for texture than for bar motion. Directional tuning interactions revealed no important class- or layer-specific differences and were similar for each monocular input. Results for bar and texture combinations moving in unison could not be predicted from selectivity for each stimulus alone. At all velocities they closely resembled those for bar motion alone. Tuning curves for the combination stimulus were only marginally broader than those for oriented stimuli: much sharper and totally different in profile from those for texture. It is concluded that an oriented stimulus in motion induces potent blockade of complex-cell sensitivity to moving textured backgrounds. Complex cells insensitive to relative motion between objects and backgrounds (Hammond & Smith, 1982a, 1983b) may thus be excellent candidates for resolving motion of objects regardless of the context in which they are seen.
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