1. Introduction

Artificial neural networks are inspired by the workings of the brain, in particular biological neurons, whose schematic diagram is shown in figure 1 . Neurons receive signals (electrical impulses) via dendrites (input) and send information via axons (output). Contacts between two neurons (between axon and dendrite) are made via synapses. Signaling is not linear, but follows a threshold effect. This biological neuron can easily be compared to the artificial neuron shown in figure 3 .