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Fig. 14.3. Architecture of the handwritten digit recognition system. In the input, a normalized bitmap image of digit 8 is presented. The activation propagates through the afferent connections to the map, which is either a SOM or a LISSOM network; a LISSOM map is shown in this figure, together with an outline of the afferent (solid line), lateral inhibitory (dashed black line), and lateral excitatory (dotted white line) connections of one neuron. In LISSOM, the activity settles through the lateral connections into a stable activity pattern (Figure 14.8); in SOM, the response is due only to the afferent connections (Figure 14.7). This pattern is the internal representation of the input that is then recognized by the array of perceptrons at the output. In this case, the output unit representing 8 is correctly activated, with weak activations on other units representing similar digits such as 2, and 9. The gray scale from white to black represents activity from low to high at all levels.