The basic artificial neuron
The building block of a neural network is an abstraction of a biological neuron, a quite simplistic but powerful computational unit that was proposed for the first time by F. Rosenblatt in 1957 to make up the simplest neural architecture, called a perceptron, which we are going to analyze in the next section. Contrary to Hebbian learning, which is more biologically plausible but has some strong limitations, the artificial neuron was designed with a pragmatic viewpoint and only its structure is based on a few of the elements that characterize a biological neuron.
However, recent deep learning research activities have unveiled the enormous power of this kind of architecture. Even though there are more complex and specialized computational cells, the basic artificial neuron can be summarized as the conjunction of two blocks, which are clearly shown in the following diagram:
Structure of a generic artificial neuron
The input of a neuron...