CORRELATED SIZE VARIATIONS IN HUMAN VISUAL-CORTEX, LATERAL GENICULATE-NUCLEUS, AND OPTIC TRACT

We have examined several components of the human visual system to dete rmine how the dimensions of the optic tract, lateral geniculate nucleu s (LGN), and primary visual cortex (V1) vary within the same brain. Me asurements were made of the cross-sectional area of the optic tract, t he volumes of the magnocellular and parvocellular layers of the LGN, a nd the surface area and volume of V1 in one or both cerebral hemispher es of 15 neurologically normal human brains obtained at autopsy. Consi stent with previous observations, there was a two- to threefold variat ion in the size of each of these visual components among the individua ls studied. Importantly, this variation was coordinated within the vis ual system of any one individual. That is, a relatively large V1 was a ssociated with a commensurately large LGN and optic tract, whereas a r elatively small V1 was associated with a commensurately smaller LGN an d optic tract. This relationship among the components of the human vis ual system indicates that the development of its different parts is in terdependent. Such coordinated variation should generate substantial d ifferences in visual ability among humans.