How do we learn? How do we remember? How can a mass of neurons in the brain produce bodies of knowledge from our experiences?
Recently I came across an excellent description of what we know about this in Dennis Bray’s wonderful book, Wetware, which I have referred to a number of times in this blog.
Neurons communicate with other neurons via synapse. A synapse is a tiny gap (cleft) between the sending part of one neuron (the axon) and a receiving part of another neuron (a dendrite or cell body). When an electrical signal travels to the end of an axon, it causes the axon to spill out molecules of neurotransmitter. The neurotransmitter molecules spill into the tiny synaptic cleft. Then they diffuse across the synaptic cleft and lodge in receptors on the receiving neuron.
So far, all we have is a signal from neuron A to neuron B. But it turns out that if neuron B is simultaneously sending a signal (say to neuron C or D), the synapse between A and B will be strengthened.
Bray’s example here is the Pavlov experiment with dogs. The sound of the bell makes neuron A fire a signal so that the dog hears the bell. The smell of food makes neuron B fire a signal so that the dog salivates. The strengthened synapse results in the dog salivating when it merely hears the bell.
How does this synapse strengthening happen? More on this in my next post.