The kinetic occipital region in human visual cortex.

In the present study we showed that the kinetic occipital (KO) region, located laterally in occipital cortex approximately 20 mm behind human MT/V5, can be strongly and bilaterally activated under passive viewing conditions. We used continuous, randomly changing visual stimulation to compare kinetic gratings to uniform motion and kinetic gratings to luminance defined gratings. The KO activations under these passive conditions are stronger than those observed when the two types of gratings are compared under active conditions, i.e. while subjects perform a task (counting gratings of a given orientation). Region KO was shown to process both shape and motion information, the conjunction of which is typically present in kinetic contours. Area MT/V5 also processes these two aspects of visual stimulation but favors motion signals. Clear segregation of shape and motion processing was observed only in occipitotemporal and parietal regions respectively. Although neurons with properties similar to those derived from the conditions activating the KO region have been documented in the macaque monkey, their location seems inappropriate for them to correspond to the KO activation observed in humans.