Fig. 5.

Triplet STDP leads to spatiotemporal receptive field development. (A) Four different bars (horizontal, vertical, and the two diagonals on a 9 × 9-pixels image) were presented as inputs to a feedforward network with a single postsynaptic neuron; each bar can move in one of two directions, giving a total of eight patterns. (B) Time evolution of the 81 synaptic weights. (C) Final weights reordered in a grid corresponding to the input location. (D) Histogram of the postsynaptic firing rate plotted after convergence of the weights, at the end of the learning in B. The firing rates shown resulted from the presentation of the eight different patterns (four orientations and two directions) averaged over 200 s. (E) After learning with different training presentation times (5, 7, 10, 12, 17, 20, 22, and 25 ms), the weights were frozen during a testing phase. The pattern (of the eight patterns) that resulted in the highest firing rate at the training presentation time was presented again to the network at different tested presentation times (5, 7, 10, 12, 17, 20, 22, and 25 ms) while the firing rate was measured. The best tested presentation time for which the firing rate (averaged over 100 s) was the highest is plotted against the training presentation time (mean ± SEM over 10 trials).