In parts one and two we touched on the basic building blocks of the CNS and a couple of the mechanisms that allow our biological neural networks to develop with experience. This part is mercifully short but important (should have doe this one before plasticity). Before starting into the higher levels of organization within the CNS it's good to really nail down the level of complexity that exists at the most basic level. One of the hang ups people have about a biological explanation for thought is an under appreciation for just how extensive our neural networks really are.
Part one covered very basic structures of the neuron with the picture below.
We covered the fact that the level of connectivity of a real neuron was considerably higher, but how high is it really? The image below is closer to reality. This image looks much more complex than the simplified one above. Surely, it's an accurate illustration of a real neuron.
No, not really. This illustration shows 800 dendrites. Eight hundred individual connections with other neurons to a single neuron. And it's still just a simplification. The average neuron in the average adult human brain has 7000+ connections. So this complex looking picture is 8-10x too simple to represent the average human neuron.
Now imagine the connections to this one neuron.
In this image stimulating neurons are ones with purple dendrites and regulating ones are in green. Some neurons are tasked with suppressing the firing of a neuron and others with stimulating it to pass its signal to those up its chain. This is just the connectivity of one amongst 10- 11 billion others. Each of which is connected to a similar number of others.
Looks very complex doesn't it. The only problem is that these last two pictures would have to include 260x more connections to be an accurate picture of an average neuron. Do the math. Is it really that hard to imagine that some extraordinary processes that at times look magical can be accomplished with the numbers of combinations or permutations that actually exist in our brains?