## Adaptivity

**“**Information is stored in the weight matrix W of a neural network. Learning is the determination of the weights. Following the way learning is performed, we can distinguish two major categories of neural networks:

fixed networksin which the weights cannot be changed, ie dW/dt=0. In such networks, the weights are fixed a priori according to the problem to solve.

adaptive networkswhich are able to change their weights, ie dW/dt not= 0.”

Source: http://www.doc.ic.ac.uk/~nd/surprise_96/journal/vol4/cs11/report.html