There are two types of symmetry breaking during the development of both feedback and feedforward connections. First the feedback connections break the symmetry of lateral connections patterns, the lateral connections self-organize into strip-like columnar structures that prefer intracortical activity pattern of a specific wave form. This type of symmetry breaking distinguishes our work from all the other works on the development of orientation and/or ocular columns. Second the feedforward connections for each V1 cells break the symmetry and become selective to inputs of certain orientations. The orientations of the cells are regulated by the symmetry breaking cortical feedback connections.
Figure 2: The results of the development of visual cortex with feedback connections. The simulated cortex consists of 48x48 neurons, each of which connects to 5x5 other cortical neurons (left) and receives inputs from 7x7 LGN neurons (right). In this figure, white indicates positive connections and black indicates negative connections. One can see that the change of receptive field's orientation (right) is highly correlated with the strip-like pattern of intracortical connections (left).
Our theoretical predictions of the development is illustrates in Figure 2. The intracortical connections break symmetry and develop strip-like patterns with a characteristic wave length which is comparable to the developed intracortical inhibitory range and the LGN-cortex afferent range (left). The feedforward (LGN-cortex) connections develop under the influence of the symmetry breaking development of the intracortical connections. The developed feedforward connections for each cell form a receptive field which is orientation selective and nearby cells have similar orientation preference (right). Their orientations change in about the same period as the strip-like pattern of the intracortical connections.