Structured long-range connections can provide a scaffold for orientation maps

In the visual cortex of the cat and ferret, it is established that maturati on of orientation selectivity is shaped by experience-dependent plasticity. However, recent experiments indicate that orientation maps are remarkably stable and experience-independent. We present a model to account for these seemingly paradoxical results. In this model, a scaffold consisting of non- isotropic lateral connections is laid down in horizontal circuitry before v isual experience. These lateral connections provide an experience-independe nt framework for the developing orientation maps by inducing a broad orient ation tuning bias in the model neurons. Experience-dependent plasticity of the thalamocortical connections sharpens the tuning while the preferred ori entation of the neurons remains unchanged. This model is verified by comput er simulations in which the scaffolds are generated both artificially and i nferred from experimental optical imaging data. The plasticity is modeled b y the BCM synaptic plasticity rule, and the input environment consists of n atural images. We use this model to provide a possible explanation of the r ecent observation in which two eyes without common visual experience develo p similar orientation maps. Finally, we propose an experiment involving the disruption of lateral connections to distinguish this model from models pr oposed by others.