Thursday, September 02, 2010

Neuron to Neuron Calls

The neurons are the electrical wiring of the body. All thoughts, commands to muscles, and sensory inputs happen through this system. The spinal cord is a lot like the main wiring harness to your car that carries information about speed, gas level, temperature, etc. That wiring can also send commands, turn on the headlights, honk the horn, turn on the windshield wiper motors.

Neurons receive input at one end from a branch structure, called Dendrites. They receive the signal and can pass it along through their axon to a dendrite at the tail end of their axon. Axons, similar to a wire, can run quite a distance, up to about three feet. The electrical signal runs along them and can be transmitted, much like a game of telephone from neuron to neuron. While neurons can take input from many other neurons from their dendrites, they only transmit through one axon.

At the end of the axon is a bulb, or ball. That synaptic knob and the Dendrite do not actually connect, the distance between them is called the synaptic gap. The electrical impulse is actually conducted by chemical neurotransmitters. These transmitters get released by the axon when the pulse hits them. The pulse opens up the bulbs and the transmitters go to the receptors on the next neuron. These transmitters can either excite or inhibit the receptors of the next neuron in the chain.

Friday, August 27, 2010

Action Potential

Neurons get an electrical imbalance, with a relative positive charge outside and negative charge inside. This comes about as the membrane surrounding the neuron lets out three Sodium ions(Na+) and brings in two Potassium ions(K+); this is called the Sodium Pump. The net effect is to have a relatively positive charge outside the cell. As the electrical charge builds outside the cell, the voltage difference will rapidly increase. Eventually this imbalance triggers channels in the membrane to open that will release the Potassium that is built up inside and the process starts anew.

This imbalance, called action potential, happens at just one small spot on the neuron. when the change occurs, there will be an electrical imbalance to the area just next to it. In this way, electrons essentially pulse down the neuron. These pulses travel much faster if the diameter is larger. Squid have the largest diameter, and so the fastest pulses. The problem with larger diameters however is that the signal fades out faster, so they can't travel long distances. They are also easier to see and as a result a lot of experiments have been done on our multi-legged friends. The other thing that increases speed is myelin sheaths. These sheaths have breaks in them, that have the poetic name of the 'nodes of ranvier'. Myelin essentially prevents the positive imbalance everywhere but the gaps, this forces the electrons to shoot from node to node, speeding the transfer.

Wednesday, August 25, 2010

Neurons

Consciousness is wrapped up in the brain. At its core the brain is based upon the way neurons work together. The brain is essentially electrical. It functions through Sodium and Potassium ions which are either allowed in or expelled. These are transmitted through channels, called axons. If I understand it properly, neurons function rather like capacitors, where they get a certain charged based on the flow of Sodium and potassium ions. Once they hit a certain charge they are likely to fire, this charge grows until they absolutely fire. They receive charge from other neurons on one side, and send charge to other neurons when they fire.

In this way a group of neurons fires up or dampens the neurons around it. Where the neurons ‘talk’ to each other are called the synapses. The spaces between them are called synaptic gaps. They can be either exciting neurons next to them to chatter, or shushing them to quiet down. Some interesting side notes here, epilepsy is essentially when the neurons fire wildly, creating almost an electrical storm in the brain. Multiple Sclerosis on the other hand is a degradation of the sheath that insulates the axon. Very much like a wire that has no plastic insulation left, it is likely to short or not transmit its charge, causing difficulty in speech and muscle control.

The way neurons fire, or don’t fire is wound up in how we remember things as well as how we think. It seems that these processes are not completely understood. In general the brain seems to have different departments that manage certain functions. But the brain is rather remarkable in being able to retrain other areas to take over these functions when injured. We will look closer at the ingress and egress of potassium and sodium tomorrow.

Tuesday, August 24, 2010

Consciousness

I suppose in starting off, I really ought to try and define consciousness. The easiest way comes from my dictionary:

1 : the quality or state of being aware especially of something within
2: the state of being characterized by sensation, emotion, volition, and thought : mind
3: the totality of conscious states of an individual
4: the normal state of conscious life
5: the upper level of mental life of which the person is aware as contrasted with unconscious processes

This gives a reasonable starting point, particularly the second definition. Sensation, emotion, volition and thought. Can animals be considered conscious; perhaps they can’t be considered to think. Emotion would tend to leave out computers as we know them know, but artificial intelligence is in it’s infancy, perhaps this will emerge as models progress. John Locke defined it as “the perception of what passes in a man’s own mind.” This captures the self-awareness and thoughtfulness that likely excludes animals.

The self-aware portion goes away while asleep, leaving us temporarily unconscious. Being conscious of our thoughts and surroundings is considered to be so vital, that if our brain is deemed to permanently have lost that ability, it is ok to extinguish someone’s life. This elusive consciousness is the most valuable piece of life. This must be why we have made it a divine spark from the gods. It is completely unique and separates Human’s from the rest of animals.

Monday, August 23, 2010

Turing Test

One of the interesting questions about consciousness is whether it belongs exclusively to the living. In other words, can people come up with a computer sophisticated enough that it can be considered conscious? Probably the most famous test for this was by the British code breaker in World War II, Alan Turning. The Turing Test would have one person in conversation with another person and a computer. If the computer can answer questions put to it in such a way that people can’t tell it is a computer, it can be considered to be a thinking machine. While it has critics, the Turing test is considered to be a benchmark for artificial intelligence, one that no machine has yet to be able to achieve.

Sort of an interesting analog is the use CAPTCHA, where you are required to input a distorted word or string of letters in order to prevent machines from spamming websites or blogs. Humans are very good at pattern recognition, so these distorted images are typically clear to people. If someone were to develop a pattern recognition software capable of defeating this method of identifying people, it would in a sense be thwarting todays test.

Computers already extend what people can do dramatically; the question is whether people will be able to build essentially minds that are more powerful than their own. The other question this brings up is if they do, will the computers really need people anymore? This has been grist for any number of science fiction plots, the most obvious being HAL in 2001, A Space Odyssey. This brings up some odd moral questions too, would it be ethical to turn off a computer that was ‘aware?’ It also brings up the issue of whether people are simply complex machines, or if there is something more required; either on a quantum level, or if there is some sort of divine spark that makes human’s unique. Just scratching the surface, I lean towards thinking there is something not determined by natural physics laws, but something likely not religious in nature.

Friday, August 20, 2010

Thinking about Thought

I ran across a blog that was discussing atheism, determinism and consciousness. While the conversation did not progress very well, it did spark a powerful curiosity about the topic. I come to realize that although I think every day, I know very little about the process. I am conscious, but have spent very little time considering what, exactly, that means. As an atheist among Christians I seemed to primarily be an annoyance, but for myself, the process of writing about thinking led to so many interesting questions, that I thought I would continue it here where folks would have to seek out being annoyed.

What is thinking? What are the physical mechanics? How are thinking and past experiences entwined? What is consciousness? Is it a deterministic (pre-determined) process based on the exact makeup of our brains, or is there a random element? Do thought mechanics allow for free will? How exactly do we sense things for the outside world? Is it possible that there is more to sense and we just aren’t equipped to do it? How does the mind focus on something? How well do we multi-task? If we create a machine that emulates the mind well enough, can we call it conscious? Why music and art; what do we get from these? What are emotions and what use do they have? Can we chemically or electrically alter our emotions?

It seems to me that these questions are what makes humans truly unique, I don’t seem to have thought much about them. I’m planning to push out a thought and read some every week day; weekends are for important things like family and football.

Friday, April 02, 2010

Dr. Cassel Will See You Now, if You Dress-right

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