Physics of Neural Networks

The material basis of our thinking, intelligence and creativity are 1013-1014 nerve cells (neurons) which in our brain are densely packed into a grey sub­ stance weighing about 1.5 kg. Each neuron has — like the root of a tree — highly branched dendrites that collect information from about 10000 other nerve cells. This huge network, which on a microscopic scale looks rather homogeneous and disordered, is able to process information. The properties of the brain obviously arise from the co­ operation of a very large number of neu­ rons. But is it possible to understand complex processing of information on the basis of nerve cells and their inter­ actions ? Physicists are, of course, not the first and only people to think about neural networks. Much is known about single cells and their interactions. A neuron emits electrical pulses, and the mecha­ nism by which the pulses move along nerve fibres (axons) has been explained. Complex biochemical processes in the contact regions (synapses) between two neurons transmit the pulses to the connected neurons. Each neuron inte­ grates all of the transmitted pulses to