Nerve cells don’t touch each other. So, how is the electrochemical current of a nerve impulse transmitted from one nerve cell to the next in a nerve pathway? When the impulse reaches the end of a stimulated nerve cell, that cell secretes a chemical into the gap between it and the next nerve cell.
This chemical is the transmitter substance. When enough of it accumulates in the gap – zap – the next nerve cell is stimulated by it.
Now, if another nerve impulse comes along before all the transmitter substance still in the gap has broken down, the new impulse could be weak and still get the next nerve cell to fire, because it would be using transmitter substance leftover from the previous impulse.
Do you see what happens here? The more you use a certain pathway, the more transmitter substance in the gaps accumulates. Then some researcher comes along, runs some tests, and says, “You have an elevated level of blah, blah, blah.”
Oh, my! But that is no disease. It is your brain working the way it is supposed to work. Indeed, this is what gives us memory – transmitter substances that build up and remain virtually permanently in a gap – like the one that remembers your birthday.
Why did i post this? Because I thought it was a cheerful description of a serious fact of life - how the mind works.