An engineering principle used by mother nature: use of feedback for robust columnar development

In spite of the inherent variability in parameters that govern development, the columnar structures in mammalian sensory systems are surprisingly robust. For example, the average width of ocular dominance columns in cats is about 400 μm, with very little variability from animal to animal. In engineering, the effect of appropriate feedback on stable, dynamical systems is to make them robust with respect to noise, including parameter variations. The question we ask (and answer) in this paper is, if during neural development, mother nature is cleverly using this engineering principle. Through computer simulations of a biologically plausible model we demonstrate that, during the development of ocular dominance columns, this is indeed the case. Transient neuron populations such as the subplate may play a major role in the initial formation of these feedback circuits. For cleverly using feedback, mother nature also gets a bonus: the synaptic computations in the circuits are completely local and hence independent of the time constants associated with the dendritic arbors of post-synaptic (layer 4) neurons that may still be growing!