In the reading for this week, "Analysis of Signals in the Nervous System", we have learned about the basic function and structure of neurons (the building blocks used to construct our complex minds. Though the neuron is a relatively simple biological entity the understanding of one neuron is hardly sufficient for explaining the human mind and all the thousands of tasks it performs just as knowing what a stone is and what it looks like does nothing to help us understand the structure of a gothic cathedral. Now that the building blocks of the brain are understood the difficult question is how such simple structures can be put together to form the fully functional entity that is the human brain (Or a gerbils brain for that matter).
Like everything else in this universe, grasping the internal structure of a neuron is no simple matter and with today's knowledge of physics is impossible on the smallest scales. The basic functionality of the Neuron, however, seems to be understood. A neuron affects other neurons by sending out an electrical charge along it's Axon and along its 104dendrites. These dendrites are connected to other Axons. A Neuron fires its electric charge when it is charged up by another neuron's pulse. Sometimes it receives a high frequency of charges in which case it fires more often and sometimes it receives very low frequencies of charge and therefore fires less often. How the brain controls the neurons is through the use of synapses. These synapses can be either encouraging or inhibitory which either increases or decreases the likelihood of the neuron firing.
With this basic understanding of a neuron it seems that to make a fully intelligent person would take more than hormones, neurons and their connections to our internal organs and sensory organs. One might say that there has to be more than this one building block to deal with all the information we need to process but what really makes the brain functional is the structure. This structure is what we still don't fully understand and will probably not understand for a long time but to get anywhere we must try to discover the way the brain is organized.
How are neurons used to create memory? How is it used to identify objects and to figure out what to do with them? The answer is in the way they are connected and how the connections can be minutely altered. But how can a mere connection be responsible for anything? You stick one neuron on top of another neuron and what do you have? Two neurons. With 10 15 connections there is a lot of room for complexity of structure but it seems that you'd still only have just a whole lot of neurons.
To use this massive number of neurons the brain has to have some sort of coding to identify and compute objects. Recently we learned how someone might identify a coffee cup. When an eyeball is focused on a table there is a section of the table at the center of the gaze which is viewed with high resolution. This image is not printed in miniature form on the cerebellum. Instead it must be encoded so that the information can be recorded by neurons. If each neuron is assigned a certain pattern and color then with enough neurons the shapes can be superimposed to represent the object that was seen by the eye. In this way a certain group of neurons can represent a physical object in the world. To paraphrase the article these neurons are to a coffee cup like the letters d o g are to an actual dog.
If neurons are caused to fire only by the firing of other neurons and they can not be given an "on" or "off" state like the bits in a computer then how are those neurons tied together in such a way that they create a memory of a coffee cup? The brain must work with synapses since that is all that it controls. Each time a synapse fires it is slightly widened so that it is more likely to fire in the future. In this way one neuron becomes more and more likely to fire a certain pattern so groups of neurons can end up being fired together. The synapse can also be made smaller by the inhibitory synapse and thus people can forget things.
As I started thinking about the brain being organized in this basic way the electricity started coursing through the cells and axons of my mind and I started to feel that I might understand how all this might fit together in such a way that a big lump of cells could be responsible for all my actions. I started imagining my thoughts as many different chunks of memory present in my mind in one time. Each chunk would fire to thousands of other neurons nearby. If these neurons nearby were in some way linked back to this original chunk than a circuit would be created between these relevant thoughts. Because of this encouragement the synapses would widen and I would come to an understanding of the relation of these chunks. If I were to read a sentence that said drinking coffee leads to good health and eternal life I would have the coffee pattern and eternal life pattern firing like crazy. Eternal life is something my dopamine is suggesting I achieve and thinking about eternal life would then be connected to coffee. If I then read a sign saying, "Free coffee in the dining center." The coffee would fire the eternal life memory and this would be connected with the dining center and so I'd know that I should go to the dining center. Maybe it is possible to view thinking as just the association of memories which inspires one to see the world in new ways.
Though we can understand simple neuron connections, like those involved in reflexes, and we can imagine an abstract way the brain might produce thought and emotion it is misleading to say that explaining our thoughts is only a matter of understanding neurons. Knowing the building blocks is only the beginning for the incredible amount of searching that it will take to understand how the mind can conceptualize of and build a computer, love someone, and write them poetry all with the interaction of neurons and the body to which those neurons are connected.