Patterning and Plasticity of Maps in the Mammalian Visual Pathway

Abstract

Maps at successive stages of the visual system, and in particular visual cortex, organize salient stimulus features into complex cortical networks. Retinotopic maps and ocular dominance domains arise during development using a molecular program that specifies the rough topographic order of projections. Genetic mutations in mice have identified guidance and patterning cues that mediate this organization of maps and may lead to the creation of new maps. Spontaneous activity produced in the retina refines the precision of the maps before eye opening, and patterned activity after eye opening drives further refinement and maintenance. For ocular dominance, the cortex has a critical period for synaptic plasticity during which it is especially responsive to changes in input. During this time, changes in eye-specific drive lead to Hebbian and homeostatic changes in the cortical network. This potential for plasticity represents a functional reorganization in response to changing demands from the outside world and allows the organism to adapt to its environment.