Postnatal development of the monkey's visual system.

The sudden increase of nervous activity after birth may influence the development of many parts of the brain. The visual system provides a particularly striking example of the crucial significance of birth itself in the maturation of the nervous system, for visual experience is obviously unlikely in utero. The role of the activity of afferent neurons in maintaining, even guiding, the formation of functional connections in the visual pathways has been extensively studied in a variety of species: such work in primates might give insight into the same process in man and into the aetiology of certain developmental disorders of vision. We have performed anatomical and physiological experiments on the monkey's lateral geniculate nucleus (LGN), which receives input from the optic nerves, and the primary visual cortex, to which the LGN sends its axons. In both structures there are enormous functional changes after birth, but those in the LGN seem not to depend on normal visual stimulation while those in the cortex seem crucially dependent on visual input.