Brain is simple
Our brain contains approximately 86 billion nerve cells, proved Brazilian researcher Dr. Suzana Herculano-Houzel in 2009. Earlier it was believed that this number was close to hundreds of billions. The exact number was determined by, quite literally, dissolving a brain in a special solution and counting the number of neurons. Those are connected by special projections – axons and dendrites. A small space between them – the so-called synaptic gap – is where neutrons interact with each other.
Ilya Martynov
Axons serve as signal outputs for nerve cells. If a neuron is not excited enough, information is not transmitted and the neuron remains inactivated. The responsibility for cell interaction rests on neurotransmitters. They are synthesized inside a cell and are delivered to the end of an axon, to the presynaptic membrane. There, electrical impulses push them into the synaptic gap and activate the next neuron’s receptors. Once they are activated, the neurotransmitter either re-enters the cell (reuptake) or is destroyed.
Neurotransmitters can be inhibitory or excitatory. The number of each type affects a person’s behavior, their thoughts and their decision-making process. This balance and the switching between inhibiting some cells and exciting others is necessary for humans to be able to switch between activities and adapt to the changes in their environment.
The structure of a neutron. Credit: depositphotos.com
For instance, when one falls asleep on a night train – how does the brain block out the sound of the tracks, voices, the flickering of lamps? By dampening the activity of certain cells, the brain modifies our auditory perception, which is why it’s much harder to wake up someone sleeping on a train using repetitive, constant noise.
Culture, decision making, the ability to put things off – none of this would have existed if the brain didn’t have this ability. Neurons are able to compete with each other for the chance to be activated and to receive more neurotransmitters, explains Ilya Martynov. This competition works like natural selection – it depends on the amount of blood supplied to certain brain regions, from the functional state of each neuron, the amount of oxygen and nutrition surrounding it and other biological factors that are nearly impossible to predict or control. There are also special “braking systems” in the brain that prevent particular types of competition from occurring. This concerns, for example, the neurons that are responsible for sending the signals needed for contraction of muscles – if these neurons would compete with each other, our bodies would never stop twitching. In a developing fetus, 60 million neurons die off every hour – so high is the amount of competition among them. Each neuron has to establish a synaptic connection with at least one other neuron or it will die. Neurotransmitters are required for such connections to occur.
Dopamine
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Dopamine is the main source of pleasure or the anticipation of pleasure. It is produced when humans encounter a subjectively pleasing experience. Why subjectively? Because most of all we love the things that help us survive as individuals – which is why the highest levels of dopamine are achieved during meals or sex.
Yet dopamine also serves as the precursor of pleasure – that feeling of anticipation before one is rewarded for their actions. This is why we can get up each morning and go to work for years on end, even if it takes great effort. Dopamine makes us aware of the fact that work means money and money means being able to do something nice for yourself.
In a lab experiment, mice had their levels of dopamine increased when they pressed a button. Over time, the mice had started to press it with increasing frequency. They also stopped eating, sleeping, or doing anything else except for pressing the button a thousand times per hour. The feeling of impending pleasure was more important to them than actual satisfaction.
In humans, dopamine serves as a constant stimulus that makes us do things, develop long-term plans and goals. Otherwise humans would have never been able to create civilization. The ability to plan things and to delay pleasure has made us truly sentient.
“People who lack dopamine are always late; they often switch jobs and find it hard to do repetitive work. Neurotransmitters also let us switch from one type of cognitive activity to another, to keep moving forward. When you see someone who is so irregular or amorphous, they might just be lacking in dopamine. However, this is not some disorder – these people can still focus and motivate themselves when they need to; this is just a peculiarity of their neurophysiology and genetics,” – explains Martynov.
Malfunctioning dopamine receptors can cause schizophrenia and hallucinations. There is also such an occurrence as dopamine-cognitive fatigue. Basically, your brain “programs” itself to feel exhausted. The body might be in an adequate state, yet the person will still feel fatigued. This state is caused by the brain and neurotransmitters, as the brain tries to prevent over-exhaustion.
Another interesting fact related to dopamine has to do with love. Some people will love others “until death”, while others jump from one “chosen one” to another. Neurobiologists jokingly refer to the latter as “pathological lovers”.
“They say that love is an artificial feeling, as it is easier for us to replenish our resources, i.e. receive dopamine, through someone else. But you can fall in love with and sustain yourself on other things, too: videogames, or, say, hobbies or doing work you enjoy,” – notes Ilya.
Serotonin
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Serotonin is responsible for vascular and muscle tone and affects the gastrointestinal muscles. A lack of serotonin increases pain sensitivity in the body’s nervous system, which is the reason why everyone has a different pain threshold. The pain experienced by drug addicts during withdrawals is caused by a lack of serotonin, too. When their neurotransmitter level drops, they become overly sensitive to pain and even the slightest touch causes agony.
Serotonin also helps filter thoughts and images. If these filters are broken down, the first symptoms of schizophrenia may begin to occur. LSD, for instance, works because the drug’s chemical compounds combine with serotonin receptors and disrupt their normal functions, causing neurotransmitters to activate various zones of the brain at random.
Serotonin is also an indirect cause of depression, which occurs due to the lack of this neurotransmitter, which controls negative emotions and balances them against positive ones. After all, if humans only walked around happy and eager, they’d never get far – the refusal to act on instincts is humans’ self-preservation mechanism against risky decisions.
Brain is king
The understanding of how a person’s actions are determined not by their “mind”, but the physical and chemical processes in their brain is gradually becoming more commonplace not just among doctors, but others, too. Ilya Martynov brings up a few examples of how that might work.
There have been several precedents in legal history where defendants have claimed that their crimes were committed not by them, but their brain due to a spontaneous impulse or malfunction. This is becoming a hot topic among legal experts even now.
Some artists propose to scan the brains of their distinguished colleagues to understand how their brains work. Research into activating the brain’s pleasure zones is actively used by art marketers. For instance, people may be asked to listen to a song while being tested by an MRI machine. The test subject might claim that they don’t like the song or it’s nothing special, but if their brain “lights up” with pleasure, then the song is a successful one.
So, is it time to talk about the end of the age of subjectivity? Or do you still believe that you are what you think?
