To the untrained eye, the human brain is indistinguishable from that of a chimpanzee - our closest relative in the animal kingdom - except for its size. The chimpanzee's is much smaller, weighing only about 420 grams, while the human brain weighs between 1.3 and 1.4 kilograms. If it were unfolded and ironed flat, it would take up about half a square meter on the table. To make room for it in the cranial cavity, it had to unfold, much like a walnut. Over the past 40,000 years, since our ancestors lived in caves, our brains have not changed much. We remember: About 30,000 years ago, the last of the Neanderthals - the closest relatives of modern humans - died out in the early part of the Paleolithic. Based on the fossilized remains of a larynx, paleoanthropologists believe that they already had a primitive spoken language, perhaps similar to the bleating of a sheep.
The brain's fuel is glucose, colloquially known as dextrose, and oxygen. Both come from the bloodstream. The brain consumes between 25 and 30 percent of the body's total glucose, even though it makes up only about two percent of the body's weight. For this reason, the brain is sometimes referred to as the body's parasite. The more this organ is used, the more glucose it consumes. However, it can also optimize glucose consumption by, for example, refusing to listen to someone who is speaking in a complicated, long-winded and verbose manner. The brain's energy consumption of about 30 watts per day shows how economically it works. This is the equivalent of one light bulb. When a "light" comes on, however, the energy consumption is likely to increase.
In the following, I will present you with some interesting and worth knowing facts and figures about the mysterious brain, which are extremely exciting and hardly any of us are aware of.
- Unlike a house with several tenants, the three levels of the brain (brainstem, diencephalon, and cerebrum) are constantly communicating with each other. The total length of all the nerve connections through which this happens is estimated to be six million kilometers. No skyscraper or building complex in the world has a network of nerves anywhere near as long. It would stretch about 150 times around the Earth. This figure is based on estimates, some of which are far apart. The one given here is the lower limit (the real one will probably be much higher).
- Communication between the three levels, as well as from the brain to the body and vice versa, occurs through electrical and biochemical signaling. Each of the approximately one hundred billion brain cells (neurons) is connected to thousands of other neurons by synapses. The job of synapses: They amplify, attenuate, or block incoming signals. Then they pass them on. All of this happens in milliseconds. If you've ever accidentally touched a hot stove, you know how quickly the brain reacts and processes information. Even before you become aware of the pain and its cause, your hand will reflexively jerk away from the hot plate.
- You can consciously change the state of your brain, for example, to find creative thoughts more easily: Expose it to new sensory stimuli, such as a short walk or a short break from thinking in the company cafeteria, to interrupt brooding over a problem. During such "distractions," the brain continues to work on possible solutions in the background.
- Comparing the brain to a supercomputer is a comparison that limps on both legs. It underestimates the brain's capabilities and overestimates those of the steel bit and byte machine. Granted: A computer can do many things much faster and better than a human, such as performing arithmetic operations or creating graphics and simulation models. But as soon as an emotional level is added (and all information is emotionally evaluated into a positive, negative or neutral form at the barrier to the brain), the computer has had its day. The brain does not.
As mentioned and explained before, our brain resembles a three-story house. The brainstem is on the bottom floor. It forms the interface between the spinal cord, which runs in the spinal canal as part of the central nervous system, and the other regions of the brain. Its main function is to control all basic life-sustaining functions such as heartbeat, blood pressure, and breathing. The reproductive instincts and drives are also located there. Serious injury to this part of the brain, which is the oldest in evolutionary history, results in immediate death.
A comparison shows how sensitive the brainstem is to other regions of the brain and body: If our foot falls asleep because of an unfavorable sitting posture, the cause is a nerve whose oxygen supply is disturbed. We get up and move. The foot wakes up because of the improved blood supply. If a stroke interrupts the blood supply to the cerebrum, which is located two levels above the brainstem, speech production, for example, can be severely impaired. Depending on which region was temporarily undersupplied and how long this deficiency lasted, partial or complete recovery of impaired speech functions is possible. However, if the blood supply to the brain stem is temporarily interrupted, the entire brain goes to sleep, to use the foot analogy, and we are dead.
On the second floor of our brain is the diencephalon. Its main task is to process all the information that arrives there through the sensory channels (optical, acoustic, etc.) and make it readable for the cerebrum. This is done by the thalamus, which is made up of two pigeon-sized halves and acts as an upstream filter. It decides which information is so important for the organism that it must reach consciousness. This is why it is called the "gateway to consciousness". Only essential information is allowed to pass. All other information is suppressed so as not to create data chaos in the cerebrum.
The diencephalon also regulates the metabolism. It controls the sex drive and stimulates the immune system. It also controls attention (what is interesting, what is not?). This is also where the neurovegetative and hormonal stress responses are formed, such as the increase in blood pressure, the acceleration of the heartbeat, the increase in the respiratory rate to add more oxygen to the blood, the constriction or dilation of the blood vessels, or the inhibition of intestinal activity. In this way, the body is optimally prepared for fight or flight. Because this much is clear: When you have to fight or flee, you need energy. Digestion is not so important now. The problem is that, unlike our prehistoric ancestors, we can't use enough or any of the energy provided for fight or flight. We don't hit someone over the head with a club in an argument, and we don't sprint out of a client's or boss's office at record speed when we feel personally attacked and insulted by their words.
Like a double ring with structures extending far into the cerebrum, the limbic system lies around the thalamus. The limbic system plays a dominant role in the development of basic emotions (anger, sadness, fear, joy, hate, disgust, etc.). In terms of the effect of verbal communication, this is where the action is. It can lift our mood or send it to the basement. The central switchboard, our information outlet, is the hippocampus. There is one in each hemisphere of the brain, and it looks like a seahorse. Hence the Latin name. Anatomically, however, the two hippocampi are located in the temporal lobe of the cerebrum. In other words, on the next floor up. So is the amygdala, also known as the almond nucleus, which is involved in the emotional evaluation of a situation and the development of fear.
In language processing, the limbic system's main task is to emotionally color incoming information (word content, sound and nonverbal signals) according to their meaning for us. Only then are they passed on to the next stage, where they are heard - i.e. consciously perceived - by the cerebrum and stored along with the emotional effect. For the brain, there is no value-free communication, only a valuable one that is useful in some way, a negatively evaluated one that leads to an attack or defense reaction, and one that requires no reaction.
The emotional coloration of language processing is always accompanied by corresponding physical reactions triggered by hormones (biochemical messengers). They are consciously perceived as a feeling of well-being or even happiness, or they penetrate the consciousness as unpleasant sensations (e.g., stress). The cerebrum then interprets the cause of these feelings. In this investigation of causes, it rarely behaves as if the bad feelings are the cause. The triggers are easier to find elsewhere than within oneself.