Figure 5.

Changes in topology for different structural plasticity mechanisms. These are the connection matrices from the input population to the computation population for four differently trained networks. Since STDP has no mechanism to delete weak synapses the connection matrix of the network trained with only STDP has non zero entries spread evenly. Bookkeeping with pruning reduced the total number of synapses over time which led to a sparser matrix. The bottom left and upper right corner of each matrix have non-zero entries due to the wrap around and therefore periodic nature of the input.