Abstract

Visual systems first evolved not to enable animals to perceive the world, but to provide distal sensory control of their movements. Conscious sight is a relatively recent invention, but its emergence has enabled organisms such as humans and other primates to carry out complex cognitive operations on a detailed perceptual representation of the world. The two streams of visual processing that have been identified in the primate cerebral cortex are a reflection of these two functions of vision. The dorsal 'action' stream projecting from early visual areas to the posterior parietal cortex mediates the visual control of skilled motor acts. The ventral 'perceptual' stream projecting from early visual areas to the temporal lobe provides a perceptual experience of the world beyond our bodies. Both streams work together in the production of adaptive behavior.