Spontaneous symmetry-breaking energy functions and the emergence of orientation selective cortical cells.

The mammalian visual cortex is comprised of "hypercolumns" of orientation selective cells. The developmental process by which cells are generated with receptive fields tuned to a variety of orientations has so far remained a mystery. We present a model for the production of orientation selective cells that requires no external stimuli and a minimum of input parameters. The process involves spontaneous symmetry-breaking in an energy function that governs the maturation of the cortical cells in a multi-layer network of Hebb-type feedforward neurons. An important feature is that the symmetry breaking occurs for each cell separately and is not due to global organizing effects. We present examples of receptive field profiles calculated with the symmetry-breaking procedure and note that the results seem robust and may be useful in the study of development in several types of cortical cells. The inclusion of long range lateral (intra-layer) correlations in the energy function could result in the development of cell groups with correlated preferred orientations that resemble the hypercolumns seen in the visual cortex.