Emergence of response selectivity for a source. (A) Evolution of neuron 1's responses that learn to encode source 1, in the sense that the response is high when source 1 takes a value of one (red dots), and it is low when source 1 takes a value of zero (blue dots). Lines correspond to smoothed trajectories obtained using a discrete cosine transform. (B) Emergence of neuron 2's response that learns to encode source 2. These results indicate that the neural network succeeded in separating two independent sources. (C) Neural network cost function $L$⁠. It is computed based on equation 3.1 and plotted against the averaged synaptic strengths, where $W11_avg1$ (⁠$z$-axis) is the average of 1 to 16 elements of $W11$⁠, while $W11_avg2$ (⁠$x$-axis) is the average of 17 to 32 elements of $W11$⁠. The red line depicts a trajectory of averaged synaptic strengths. (D) Trajectory of synaptic strengths. Black lines show elements of $W11$⁠, and magenta and cyan lines indicate $W11_avg1$ and $W11_avg2$⁠, respectively.