01 September 2017

Biochemistry of Happiness

What do neurophysiologists know about the source of positive emotions in the brain

Elizaveta Ivtushok, N+1

As you know, there is no universal definition of happiness, the same for representatives of all countries and cultures, and even the words for "happiness" in different languages have different meanings (read about what anthropologists think about this in our previous article). However, happiness is actually even more subjective. From the point of view of cognitive sciences, it is impossible to develop a reliable methodology that would allow us to study what happiness is, because for each person it depends on different factors. Only certain aspects of our behavior and emotional state can be measured, but perhaps they can give a clue to what processes occur in the brain of a happy person. They will be discussed in this article.

From the point of view of cognitive science, happiness is very difficult to measure, because for each person it is expressed in its own way: for someone happiness is wealth, for someone love, and someone will say that happiness consists in having a goal in life. Accordingly, our good mood is controlled by individual stimuli that can cause different people to have different intensity of positive emotions (from light joy to euphoria). Therefore, it is almost impossible to systematically study the brain of a happy person in order to answer the question of what happiness is.

The subjective experience of happiness, however, can be divided into two relatively objective components: emotional (the intensity of bad and good emotions) and cognitive (the integrity of our consciousness). The "recipe" for a happy life, therefore, includes two components: positive emotions (and, as a matter of fact, the absence of negative emotions) and a sense of meaningfulness of what is happening in the world around us and with ourselves. Below we will focus mainly on the first of them.

The lever of pleasure

Emotion is a mental state (positive or negative), the appearance of which is largely responsible for a complex set of brain structures – the limbic system (it is also responsible for regulating more basic human functions, such as olfaction and circadian rhythms). In simple terms, an emotion is a person's reaction to a certain external (from the surrounding world) or internal (for example, mental) stimulus and what this stimulus may follow.

Negative emotions, such as fear or disgust, can be traced in the human brain quite easily: the amygdala, or amygdala, is responsible for them. And if fear and disgust are basic emotions developed in the process of evolution, then with positive emotions everything is much more complicated. Psychologists have long believed that positive emotions are largely associated with pleasure. Therefore, in order to trace the processes taking place in the brain of a joyful or happy person, they study the emotional response of a happy person.

Studies of pleasure and the neural correlates associated with its receipt originate in the experiments of behaviorists of the early XX century. The object of the study of behaviorism as a direction of psychology is behavior, in particular, the behavior of an individual as a reaction to a certain stimulus (external or internal). The famous experiment conducted by American behavioral psychologists James Olds and Peter Milner in 1954 led to the discovery of an important part of the brain, which they called the "pleasure center".

The experiment involved rats who were sitting in a special box with electrodes implanted in the limbic system. The scientists wanted to find out what kind of reaction the stimulation of different parts of this area would lead to. Low current discharges were released through the electrodes every time the rat entered a certain corner of the cage. Scientists found that after receiving stimulation, the rat began to return to the corner again and again. Later, the scientists checked whether the effect would be preserved if the animal was responsible for receiving the reward itself, and gave him the opportunity to receive stimulation by pressing the lever. The rat, ignoring the actions necessary for survival, pressed the lever until it died of exhaustion.

Based on this, Olds and Milner concluded that brain stimulation caused pleasure in mice, and the electrical stimulus itself was a good positive reinforcement. Two areas of the brain that are subject to stimulation have been named by scientists as part of a large set of brain structures called "pleasure centers": the septal area adjacent to the corpus callosum, as well as a small part of the striatum – the nucleus accumbens.

Subsequently, experiments with implanting electrodes into the brain in the area of the "pleasure center" were tried to be carried out on people (the psychology of the 60s was not very ethical by current standards), but soon this practice was abandoned. Later, the study of the "pleasure centers" led to the discovery of a substance released in the brain in the process of obtaining pleasure – dopamine.

There are several "pleasure centers" in the brain: in addition to the mentioned departments of the limbic system, scientists also distinguish some parts of the cerebral cortex (for example, the orbitofrontal cortex and the insular lobe). The exact functions of each of them have not yet been established. In addition, the "pleasure centers" are most often considered as parts of a more complex system – a set of brain structures called the reward system. Such a system is responsible for several aspects related to receiving a reward: the desire for a pleasant stimulus, positive emotions (pleasure) in response to a pleasant stimulus, as well as the consolidation of behavior that led to the receipt of this stimulus.

Molecules of happiness

Several neurotransmitters are responsible for getting pleasure in the brain – chemicals that transmit a signal between two neurons through a synapse, the place of contact of two neurons. We will consider the properties and functions of the most basic.

Dopamine is a neurotransmitter from the monoamine group, a biochemical precursor of norepinephrine. Dopamine has several very different functions, including control over motor and executive (cognitive) activity. Dopamine is also a neurotransmitter involved in the activation of the reward system.

The neurons of the "pleasure centers" secrete dopamine in the process of responding to a certain pleasant stimulus for a person, as well as to the anticipation of receiving it. The stimulus can be anything: sexual, sensory, external, internal. It can be food, or it can be the face of a loved one. Everything that pleases us causes us pleasure; pleasure, in turn, causes joy.

Another important neurotransmitter involved in the formation of positive emotions is serotonin. Like dopamine, serotonin comes from the monoamine group. Among the functions for which serotonin production is responsible, in addition to mood regulation, are memory and sleep. Serotonergic pathway dysfunction is one of the causes of clinical depression and restless states – a kind of "antonym" of happiness. That is why many antidepressants work on the principle of inhibiting serotonin reuptake: in a mentally unhealthy brain, the production of serotonin as a neurotransmitter slows down, and such drugs are able to restore this process.

Another group of neurotransmitters, endorphins, refers to neuropeptides that act on opioid receptors. Neuropeptides are produced in response to stress as a protective mechanism, as well as in order to reduce pain. Some opioids (for example, morphine and its analogues) also act on opioid receptors and cause the same reaction: from pain reduction to euphoria. That is why, in the pursuit of easy happiness, people start using opioid drugs. However, the feeling of euphoria is available to them only for the first time, then drug use is necessary to relieve withdrawal syndrome, or simply "withdrawal".

Also worth noting are endocannabinoid neurotransmitters, for example, anandamide and 2-arachidonoylglycerin. They take part in controlling the stress response and regulating the level of arousal. Cannabinoids – the active substances of cannabis, from which marijuana is obtained – also act on cannabinoid receptors.

The neuropeptide oxytocin, produced in the hypothalamus, is responsible for establishing social connections and developing warm, positive emotions towards someone. Thus, oxytocin is released in large quantities during childbirth, which contributes to the establishment of a strong bond between mother and child, and also helps the mother in the feeding process. A small amount of oxytocin is also released during orgasm, so it is believed that it plays an important role in obtaining pleasure during sex.

Finally, the last neurotransmitter that we will consider is norepinephrine (also known as norepinephrine), a monoamine that is a precursor to adrenaline. This neurotransmitter, along with adrenaline, plays an important role in the regulation of fear and other negative emotions, increases blood pressure and heartbeat, and is also the main neurotransmitter responsible for the stress response of the body.

Stress for many is associated with negative emotions, and a happy life in constant stress seems impossible. Does this mean that excessive production of norepinephrine is an obstacle to happiness? Definitely not. Some people find their happiness in conditions of constant stress: they include both fans of extreme sports and gambling, and those for whom the main joy in life is a permanent job.

Gamma-aminobutyric acid (abbreviated GABA), the main inhibitory ("inhibitory") neurotransmitter, whose main function is to reduce nervous excitability, also helps to control the reaction to stress. The GABA receptors are affected by benzodiazepines - psychoactive substances that have an anti–anxiety and sedative effect. Benzodiazepines are part of many medications prescribed for the treatment of anxiety and panic disorders.

Relatively recently, in 2012, Swedish scientist Hugo Levheim proposed a three–dimensional model of the connection between the joint action of three monoamines – dopamine, serotonin and norepinephrine - and the manifestation of emotions, called the "emotional cube". According to this model, joy and satisfaction are caused by high levels of dopamine and serotonin and low levels of norepinephrine, and feelings of anxiety and longing are caused by high levels of norepinephrine and low levels of the other two. However, in order for a person to experience excitement or excitement, all three monoamines must be produced in large quantities.

Chemistry and Will

Various psychoactive substances affect the release of different emotional mediators: for example, cocaine affects the exchange of dopamine, serotonin and norepinephrine, and nicotine can participate in the exchange of dopamine. The effect of these substances, however, is short-lived, dangerous and, as is known, can lead to addiction.

However, there are also less radical ways to directly affect the receptors associated with the work of various neurotransmitters. Physical exercise, for example, enhances the action of beta-endorphins, thereby improving mood. It is even believed that increased physical activity can serve as a good prevention of depression. Areas of the brain containing dopaminergic neurons are activated, for example, in people who experience pleasure when listening to music

Today it is safe to say that those sections of cognitive sciences that are responsible for the study of complex emotional states (and happiness belongs to them) are still in the process of development. Many psychologists, in particular Professor Morten Kringelbach of Oxford University, are trying to trace a systematic link between pleasure and happiness and identify neural correlates responsible for a happy life and a good mood.

Kringelbach and his colleague, American psychologist Kent Berridge, distinguish three components of the reward system: "liking", which is responsible for an objective, "chemical" reaction of a person to a stimulus; "wanting", which is responsible for a person's volitional effort to receive a stimulus; and "learning", which is responsible for for building associations related to receiving an incentive. The "propensity" to receive a stimulus, being satisfied, provides us with pleasure, but pleasure alone is not enough for happiness. The "desire" of the stimulus provides motivation to receive it, that is, this component brings a goal into our life, but the "desire" alone, without being restrained by anything, leads to dependence on the stimulus. "Learning" connects these two components and encourages us to find ways to have fun again. Happiness, according to Kringelbach and Berridge, comes down to the balance of these three components. However, scientists do not write how to achieve this balance.

Thus, modern neuroscience can give us an idea of only one component of happiness – a positive emotional response to a stimulus. The second component – the sense of meaningfulness of what is happening, the presence of a goal in life – is rather a philosophical question and at the moment is beyond the possibilities of systematic objective study.

Portal "Eternal youth" http://vechnayamolodost.ru  01.09.2017

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