The Brain and the Neural Networks

intro for physicists and mushroom-pickers

The topics "brain" and "neural networks" might suggest that they are investigated by neuro- biologists, mathematicians, or microprocessor engineers.

What may the physicists do here?

Still, they really are doing a lot. The signal analysis, the systems with chaotic dynamics, the computer simulations, the mathematical modelling, and the phase transition analysis have always been in the domain of modern physics.

A quick start question: is the brain a neural network?

YES and NO



So, the simplifications are inevitable in modelling the brain activity. It is a tempting task to reveal in (over)simplified models the features pertinent to the real brain, due to the YES.


The neurophysiology is reluctant to give answers to our questions, and that is another reason for model simplification. On one hand, the neurons are effectively damaged by the investigations in vivo. On the other hand, the non-damaging methods provide little information on the activity of separate neurons.

Happily enough, a histologist tells us that ~70% of neuron cells in the cerebral cortex are very similar. Having this, one would like to mimic in a network of interconnected nodes - "neurons" - the features a real brain has. These may be:

The learning in networks is perhaps the most intensely studied subject by physicists. Two popular models have emerged, presented in some detail here.

1. Recurrent cooperative network

2. Perceptron

Both 1 and 2 type networks have their drawbacks when compared to the functioning of the "grey matter". Among these,

Still, some features match or may be matched. And more, the artificial networks exist and operate independently of the real brain investigations.

Why not like the gods?

The investigators, if you ask them, assert you that they are not trying to make any artificial brain. No no no, they are not so ambitious. But to be able to trigger a new soul - how very intriguing that would be!

Hot links

Neuroscienes on the Internet
Introduction to the Theory of Neural Computation
An informative preprint on the subject, by Horner and Kuehn
Neural Networks Investigations at NORDITA

Last edited 1997.12.16. If you have comments or suggestions, email me at

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