Figure 2.

Demonstration of the underlying conflict between disordered phase preference, development of simple cells, and Mexican-hat-like lateral interactions. Left, RFs for an example pair of simple cells with half-rectified activation functions that are selective to the same orientation but opposite phase. When such cells are presented with stimuli of preferred orientation, they will have mutually anti-correlated activities. Mexican-hat-like lateral interactions constrain nearby neurons to have highly correlated activities, and will thus cause neurons selective for the same orientation but opposite phase to develop in different map locations. Right, an example configuration that resolves this conflict by applying a squaring transfer function to the response of the simple cells, which relies on the neurons somehow maintaining a “negative activation” internally, mapping both strong positive and strong negative activations to a strong output level. This ensures that the activity of neurons will become correlated and thus allows them to occupy nearby locations in the map, but renders their output non-simple-cell-like, and is not based on any known neural mechanism.