Our brain is the most complex machine that ever existed. With over 7.146 billion models it is also the most ubiquitous. Despite this, we are unsure of its complexity. We still do not yet understand how it works. By defining the functionality of certain areas of the brain, and by understanding some of the mechanics at the neural chemical level, we still remain ignorant of how the brain coordinates all of its activities and develops language, thought and a sense of self.
This three point three-pound wet mass—greyish on the outside, and whitish pink on the inside—controls every single thing you will ever do. Ever. Each one of us needs these complex structures because each one of us needs it to reflect the totality of the world we live in and how we function within it. Our brain constructs a representation of the world and how we function within it. Other animals do this as well, but what is important in their world is different from what our brain determines is important for us.
In the past we took a different attitude to studying the brain. Most of the scientific writing on the brain was focused on establishing the superiority of human intelligence. But there is not one single factor that we can apply to distinguish our brains from those of other animals. We cannot just use size, because some mammals (eg whales) have bigger brains. Perhaps it is the size of the brain in proportion to the body. When we try that by measuring the Encephalization Quotient (EQ) ratio, small birds beat us. Perhaps it is size, EQ and something else. The correct question is to ask what aspects of the world are we, as humans, trying to represent in our brain? And how complex is the brain really?
In 2009, the Brazilian scientist Suzana Herculano-Houzel performed a review of what we know about the physical structure of the brain. The adult human male brain has 86 billion neurons--more than any other primate. Each neuron has between 1,000 to 10,000 synapses that result in 125 trillion synapses in the cerebral cortex alone. That is at least 1,000 times the number of stars in our galaxy. Stephen Smith from Stanford University reported that one synapse might contain some 1,000 molecular-scale switches. That is over 125,000 trillion switches in a single human brain.
With such a lean mean machine then it is surprising to learn that the brain is obese. It is 60 percent fat, with over 25 percent of that being cholesterol. Cholesterol is in every cell in our body and becomes concentrated in our brain. Most of the cholesterol in the brain is produced in the hypothalamus itself, establishing cholesterol as an integral part of our brain. Cholesterol is used by a specific type of glial cells in the brain to form myelination—sheathing which enhances neuron speed and integrity of signal. Glial cells outnumber neurons ten times over with 860 billion cells. It was only in 2010 that glial cells were found to assist neurons in forming synaptic connections between each other. Once thought to be simply support cells, cleaning up and helping with myelination, they are now known to also promote dendrite growth, and to be as important as neurons in forming the neural network that make up cognitive activity. Glial cells can also reproduce—if neurons reproduce they do it slower—and similarly release transmitters and control neural activity just like neurons. All of this activity is monitored by microglia cells that not only clean up damaged cells but they also prune dendrites, forming part of the learning process.
Comparing mapping the brain to mapping the human genome is like comparing the artistry of the Mona Lisa to Sponge Bath Bob. The total length of the human genome is 3 billion base pairs, the brain has nearly 30 times more neurons. And whereas the genome base pairs has an on and off arrangement, each neuron might have a thousand switches. Mapping the brain will mean that if every switch in every synaptic end at every neuron is identified by a second of time then it will take 4,000,000,000 years to complete. The brain is that complex.
In the cortex alone, there are 100,000 miles of myelin-covered—insulted—nerve fibers. Each nerve leaves the base of the brain to the outer reaches of our skin, we have a neural network that is incomparable. We have millions of nerve endings in the outermost layer of our body that sense minute variations of light, sounds, vibrations, touch, smell, pressure, temperature; all extremely sensitive in most cases more sensitive than any computer on earth. The marvel of the brain is not just the capacity but the sensitivity to stimuli.The Human Protein Atlas identifies some 318 proteins that are involved in all these activities.
There is a galaxy of neural networks active in our bodies designed to get information from the outside. All this information is travelling from the outer reaches of the body to the brain, sometimes at speeds of 268 miles per hour. The brain is structured in such a way that information is processed both linear and parallel. And here is the beauty of the brain. It creates a kind of a dance, it orchestrates the flow of information in a way that we still do not fully understand.
We filter out most of the sensory information. Information travelling from our peripheral senses to the brain, making a vibrating, electrical symphony. Constantly on and constantly playing and the brain makes music from trillions of individual notes every second throughout our lives. And the musical composition has to do with the world outside and how it affects us. The brain teaches the body to survive. We represent the dynamics of the outside world inside our brain. There we can predict and therefore control the outcome. This is learning. Through learning and some innate ability we identify what is important and what is not so important. That “so” is crucial. Information has differing levels of importance, and also different times when we are more prone to learn than at other times.
Our brain is an organic reflection of the environment that we face day-in-day-out. Our conscious attention is drawn to specific aspects of all sensory information monitored by the brain. We are monitoring many other peripheral events at a subconscious level. The more we learn the less we need the brain, unless we challenge it all the time. That constant state of unease, that novelty, is what keeps the brain functioning as it is meant to function. Once it can predict then it no longer needs to learn new things.
All of this complexity allows the brain to continuously receive feedback from the outside to modify its construct of the world and then to determine what is important for us. Its aim is to be able to predict the environment we live in and to do that is has developed one of the most complex structures known to humans. By mapping the brain we will be holding a mirror to another mirror.
© USA Copyrighted 2014 Mario D. Garrett