The macaque lateral geniculate nucleus (LGN) exhibits an intricate lamination pattern:depending on the visual eccentricity, it has regions with six, four, and two distinct layers.The transition from six to four layers always coincides with the position of small cell-free gaps corresponding to the blind spot in theretina [42]. We have developed a 3-D model in which local cell interactions cause a wave of development of neuronal receptive fields to propagate through the nucleus and establish distinct lamination patterns. The initial (six-layered) pattern is maintained andpropagated along the LGN by strict retinotopy, cell interactions promoting clustering of cells with similar functionality, as well asexternal gradients. The initial pattern gradually becomes unstable and perturbations due to the blind spot gaps induce a sharptransition to a more stable four-layered pattern. Critical factorsfor the final global lamination pattern are the choice of the initial (foveal) pattern, the cell interaction distances, the size andlocation of the gaps, and the shape of the developmental wave-front. A simplified version of the model is amenable to analyticaltreatment, which provides important insights in the behavior of the more general model.This analysis reveals a close similarity of the laminar transition in this biological system with a well understood physical phenomenon, the so called shock-wave effect.
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