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Brain and Memory

Networks and Memory

When we need to remember something, we create links between the various parts of what we need to memorize. It’s as if we’re building a network, and each part of what we need to remember is a piece of this network.

There are two networks that we use every day to remember things. One is language: when we speak, we connect words together, and every sentence we utter is a “path” in the network of words. Some words we use often and are linked to many other words, while other words we use rarely.

The Brain Network

The other network we use is our brain. One of the greatest brain experts, Kandel, explained that in the brain, information is carried by groups of interconnected neurons, not by single neurons. Therefore, even in the brain, the keyword is “connection”.

Even though our brain is very complex and can remember things in different ways (for example, it remembers some things for a short time, others for a long time, some as places, others as actions), the way it remembers things is always the same: it creates new “paths” between neurons. This is what a psychology expert, Hebb, understood in 1949.

Neuron Activation

Hebb understood that when two neurons activate together many times, the bond between them strengthens, and this is the trace that makes us remember things. If two neurons activate together often, our brain understands that they need to be connected, and thus it creates a “path” between them.

When we need to remember something for a long time, the link between the neurons becomes definitive. However, if we need to remember something for a short time, the bond weakens if we do not often use those neurons. In essence, in our brain, the bonds we use often become stronger, while those we use less weaken and eventually disappear. It’s a bit like when we talk: if we often use two words together, our brain understands that they need to be connected. A hundred years ago, for example, nobody said “too cool”, so these two words were not connected. Today, however, we often use them together, so our brain has created a bond between them.

Natural and Artificial Neural Networks

The first neural network: the brain

We know relatively little about how our brain works, but we know exactly how artificial neural networks work, i.e. the software behind various products based on Artificial Intelligence, such as MrCall. We can then compare simple biological “brains” to an artificial neural networks.

The simplest brain: Elegans

At the moment, the brain we know best is that of a small worm called C. elegans. In 1986, all 302 neurons in the brain of a female C. elegans were mapped, and then studied extensively. In 2012, the same thing was done for the brain of male C. elegans, which has 383 neurons. The difference is due to the fact that the male must try to mate with the female, while the female can have children alone.

This coupling is not a simple thing. Although C. elegans is a very simple organism, its way of mating is complex. Yet, it manages to do all this with just a few neurons.

Elegans and neural networks

If we looked at the elegans’ brain as an artificial neural network, we would say that Nature has developed a simple—technically “shallow”—neural network. Shallow networks have only a few layers of neurons.

And so it is for the elegans’ neural network: first there are the sensory neurons, which recognise things around them, for example if there is a female nearby. Then, the information passes to a second group of neurons, and finally to the third group, the motor neurons, which initiate the movements.

There are therefore only 3 layers of neurons. In addition, as in the artificial neural networks we use today, some neurons of the C. elegans are able to remember information and reuse it.

It took Nature a few million years to develop nervous systems like that of the C. elegans, but the apparently simplicity of the of the brain of this little worm must not mislead us: “natural” brains are in any case complex, because they are made up of neurons, i.e. cells, which in turn are capable of analysing information. The neurons of artificial neural networks, on the other hand, are very simple, and in fact an artificial neural network of 300 neurons does very little!