The Development of the Map from the Nucleus Isthmi: The Influence of Visual Experience on the Formation of Orderly Connections in the Visual System

The high degree of anatomical complexity of organization in the visual system is one of its most notable features. Many variations are played on the theme of retinotopic mapping—distortions, transformations and subdivision of maps have been extensively documented in a wide range of vertebrates (Allman and Kaas, 1974; Hubel and Wiesel, 1974; Gruberg and Udin, 1978; Grobstein and Comer, 1983). One feature which most of the visual maps share in common is that the representations from the two eyes are in register. For example, a binocular cell in striate cortex has identical or nearly identical receptive field locations from both eyes. What developmental processes establish this precision of matching of input from the two eyes? This question has received intense attention from many investigators, prompted in large part by the pioneering work of Hubel and Wiesel, who demonstrated that the establishment of binocular connections can be disrupted by monocular visual deprivation or by strabismus (Wiesel and Hubel, 1965; LeVay, et al., 1980). Such manipulations prevent individual cells from maintaining responsiveness to both eyes, but the overall topography of the ipsilateral and contralateral geniculocortical maps is not disrupted.