The development of topography in the visual cortex: a review of models

The repetitive stochastic patterns of eye dominance and orientation preference found in the mammalian visual cortex have attracted much attention from theoretical neurobiologists during the last two decades. Reasons for this include the visually intriguing nature of the patterns and the fact that many aspects of their development seem likely to be dependent upon both spontaneous and visually driven patterns of neural activity. Understanding these processes holds out the promise that general theories of learning and memory may be derived from those found to be applicable to the visual cortex. It has turned out, in fact, that remarkably simple models, based on Hebbian synaptic plasticity, intracortical interactions and competitive interactions between cells and growing axons, have been able to explain much of the phenomenology. This article reviews the models of topographic organization in the visual cortex in a roughly historical sequence, beginning with von der Malsburg's paper 1973 paper in Kybernetik on self-organization of orientation selectivity. The principles on which each of the models is based are explained, and the plausibility of each model and the extent to which it is able to account for the relevant experimental data are evaluated. Attention is drawn to the underlying similarities and differences between the models and suggestions are made for future directions in research.