Dissociation of pathways for object and spatial vision: a PET study in humans

A positron emission tomography (PET) study was conducted to determine which brain regions are differentially involved in visual object identification and object localization. Subjects engaged in a spatial task in which they matched the location of common objects, and an object task in which they matched the identity of common objects. In both tasks the stimulus arrangements used were of the same kind. Regional cerebral blood flow data showed that a right-sided region in the inferior parietal lobule was more activated during spatial than during object matching. In contrast, bilateral occipitotemporal regions, with the left more predominant, were more activated during object than spatial matching. These results provide support for Ungerleider and Mishkin's dual pathway model of vision and indicate important patterns of lateralization in the human visual system.