QUOTE : The currently most popular model for such an artificial neural network represents the state of each neuron by a single number and the strength of each synapse by a single number. In this model, each neuron updates its state at regular time steps by simply averaging together the inputs from all connected neurons, weighting them by the synaptic strengths, optionally adding a constant, and then applying what’s called an activation function to the result to compute its next state.fn5 The easiest way to use a neural network as a function is to make it feedforward, with information flowing only in one direction, as in figure 2.9, plugging the input to the function into a layer of neurons at the top and extracting the output from a layer of neurons at the bottom.