ANN
Single Processing Unit

The central paradigm of neural networks is based on local computing. This means that neural networks gain their power from connecting several processing units, which have only very restricted capabilities and do not know anything about the "higher" goals of the network. The "know-how" of the network is thus not contained in its processing units but in the connections.

The actual implementation of a processing unit may differ widely and depends on the model to be used. The example below shows a processing unit as it is used in multi-layer perceptrons.

This processing unit consists of three parts:
 

• the net intput signal of the unit which is "collected" from all incoming connections
• the activation function, and
• the output function.

Distinguishing between activation and output function is somewhat arbitrary and is often neglected by setting one of these functions to the identity function. It is important to note that one of these functions has a non-linear response curve, most often a sigmoid curve.