Global visual processing in the monkey superior colliculus.

Neurons were recorded in the superficial layers of the superior colliculus in anesthetized monkeys. As classically described, cells were non-selective for target direction and speed when the target moved through an empty visual field. However, these same cells were sensitive to target direction and speed relative to a textured moving background. The target's response was suppressed when its direction and speed were similar to that of the background, irrespective of the absolute direction of background movement.