Fig. 4.

Network evolution. (A) Example of one of the 4,600 inputs presented to each evolving network during its lifetime. The input values closer to 1 (primarily LM cone activation) are depicted in shades of yellow, and those closer to 0 (primarily S cone activation) are depicted in shades of blue (see color bar). The inputs mimic the responses of single-opponent blue-yellow neurons to natural spectra, responding relatively strongly in response to LM cone activation and weakly to S cone activation. (B) After 4,000 generations, the evolved network output values (green squares) closely matched the conditional cumulative probability distribution function (red circles) of the input at the central stimulus grid square, given the input values in the surround. The slope of the conditional cumulative distribution function at any point indicates the frequency of occurrence of one of the 23 possible values at the target location (T), given the surrounding input pattern. Gray triangles show the output responses before evolution.