Stereopsis: where depth is seen

Disparity-selective cells appear to occur in all parts of the visual cortex, but a recent fMRI study finds that some cortical areas are more strongly associ-ated with disparity than others. More sophisticated tests of binocular function may be needed to identify the properties of single neurons that support this specialization. A fundamental organizing principle of the brain seems to be that anatomically discrete regions perform separate tasks. The extent of this specialization is clearest in the visual system, where the cerebral cortex is subdivided into distinct areas, each of which makes a different contribution to the processing of visual images [1]. These areas were originally iden-tified on anatomical grounds (and simply identifie