Saturday, July 28, 2012
The CIRCUIT is the MEMORY
Place a few isolated neurons (brain cells) into a petri dish, submerge them in a solution of nutrients, and every time, without fail, they will reach out to each other with axons, touch each other's dendrites, establish synapses, and, lo and behold, a mini-network, or neural circuit, will be formed. (The picture shows only 11 neurons, but the contacts number in the thousands.)
This happens in the brain millions of times every day. We also know that if one loses ones sight, ones hearing would become extra acute, indicating that the brain can "rewire" itself in response to major life changes.
What I'm writing about is my own "theory" of how this phenomenon of neural circuit formation and modification relates to and results in memory, thought and action. I could be completely wrong, or this model could have already been advanced, in which case any neuroscientist out there kindly correct me.
In neural circuitry analysis, the general schematic is that there are 3 general layers: the input layer, the processing layer and the output layer. The input layer receives stimuli from the 5 senses, and the output layer goes mostly to speech and action. It is the middle processing layer I'm talking about.
Let's talk in terms of memory alone. In my view, memory is not some nebulous, mystical or metaphysical phenomenon, but is as physical, chemical and biological as, well, the brain itself.
Memory could be multilevelled in that it could be stored on the molecular, cellular and intercellular levels. It is the intercellular level that I will be concentrating on.
On the intercellular level, i.e. in terms of neural circuitry, in this model, MEMORY IS CIRCUITRY; THE CIRCUIT IS THE MEMORY.
Let me explain:
Neurons are the only cells in the body that do not divide and multiply. The number of neuron one is born with is the maximum number one will ever have, maximum because, on the other hand, neurons can die, and they do so on a daily basis , especially after mid-life. The average number of neurons a human being is born with is about 100 billion, and this number decreases in the brain as one ages. On the other hand, there is almost no limit as to the number of synaptic contacts a neuron can have with its neighbours, far and near. On average, they number about 7000 per neuron. Generally, the more thinking one does and the more experiences one accumulates through life, the higher this number. Einstein, for example, could have 10,000 synapses per neuron, or 20,000, or 30,000, while a recreational hunter doing nothing but serial deer-killing, or some religious fanatic who reads just one book through his life (you know which one), if he reads at all, could have only 1,000, or less.
This also means that even though the number of neurons through ones life may gradually decrease, the total number of synaptic contacts may continue to increase.
In a new born baby, the 100 billion neurons are all there, but the number of synapses per neuron could be near zero. As he grows and learns, the synapses per neuron increases, and neural circuits develop. For example, when he learns how to ride a bicycle, a bicycle-riding neural circuit would be formed, and the more he rides, and develops skills, the more complex and stronger the circuit becomes. Likewise if he develops a bad habit, like smoking, there will likewise develop a smoking circuit, and once the circuit is triggered by some timed means, the urge would arise, and the output layer would cause him to light up another cigarette. In this latter case, if he wants to quit smoking, he would have to actively resist the urge and desist, which brings forth the reverse phenomenon, which is that the lesser he uses the circuit, the more it will atrophy, until finally, the circuit disintegrates, and the urge to smoke eventually dissipates.
This can apply to almost every thing in his life experience. When he hears a song, a circuit of that song would develop, and the more he hears the song, the stronger that circuit becomes, and the better he would remember the lyrics, and the more automatic the output layer can enable him to sing the song.
In this model, memory can be lost in one of two ways: the dismantling of a circuit by decreasing the number of synapses in the circuit, or the death of the neurons involved in the circuit.
This brings us to the unsavory subject of dementia, and the hopeful topic of prevention thereof. According to this model, the more one uses ones brain, in as diverse a range as possible, the larger the number of synapses would be per neuron, and the greater the total number of synapses in ones brain, and the more complex the neural circuitry therein, will result. So, even if a redneck and a renaissance man lose the same number of neurons by the same age, the redneck will be the one to lose his brain function, or lose it first.
So the moral of this model is: USE IT OR LOSE IT!
Anthony Marr, Founder and President
Heal Our Planet Earth (HOPE)
Global Anti-Hunting Coalition (GAHC)