A COMPARISON OF VISUAL RESPONSES TO OBJECT-MOTION AND EGO-MOTION IN THE MACAQUE SUPERIOR TEMPORAL POLYSENSORY AREA

The responses of visual movement-sensitive neurons in the anterior sup erior temporal polysensory area (STPa) of monkeys were studied during object-motion, ego-motion and during both together. The majority of th e cells responded only to the image of a moving object against a stati onary background and failed to respond to the retinal movement of the same object (against the same background) caused by the monkey's ego-m otion. All the tested cells continued responding to the object-motion during ego-motion in the opposite direction. By contrast, most cells f ailed to respond to the motion of an object when the observer and obje ct moved at the same speed and direction (eliminating observer-relativ e motion cues). The results indicate that STPa cells compute motion re lative to the observer and suggest an influence of reference signals ( vestibular, somatosensory or retinal) in the discrimination of ego- an d object-motion. The results extend observations indicating that STPa cells are selective for visual motion originating from the movements o f external objects and unresponsive to retinal changes correlated with the observer's own movements.