Neurobiology of love: the theory of the 3 brain systems

The love it is one of the most complex phenomena that human beings are capable of feeling. This peculiar feeling has made people wonder how and why it happens. Science has also dealt with this phenomenon, and One of the best known researchers in this line of research is Helen Fisher, a biologist and anthropologist who has spent more than 30 years trying to understand it.

Helen Fisher's investigation

To try to explain this complex feeling, Fisher focused on trying to find out the brain mechanisms that are involved in the process of falling in love and love. To do this, she subjected several subjects who were madly in love to IMRf scans, to know the areas of the brain that are activated when the subject thinks about his loved one.

Neutral and "loving" pictures

To perform the tests, Helen asked the study participants to bring two photographs: one of the loved one and another that had no special meaning, that is, a neutral face. Then, once the person was inserted into the brain scan, the person was first shown on the screen the photograph of the loved one for a few seconds while the scanner recorded the blood flow in different regions of the brain.

Afterwards, the individuals were asked to observe a random number, and then they had to subtract it from seven by seven, and then look at the neutral photograph where it would be scanned again. This was repeated several times to obtain a significant number of images of the brain and thus ensure the consistency of what was obtained while looking at both photographs.

Research results

There were many parts of the brain that were activated in the lovers who made up the experiment. However, it seems that there are two regions that are especially important in the sublime experience of being in love.

Perhaps the most important discovery was the activity of the caudate nucleus. It is an extensive region, in the shape of a "C", which is very close to the center of Our brain. It is primitive; It is part of what is known as the reptile brain, because this region evolved long before the proliferation of mammals, about 65 million years ago. The scans showed that there were parts of the body and tail of the caudate nucleus that became especially active when a lover looked at the photo of the woman in love with her.

The brain's reward system is important in falling in love

Scientists have long known that this brain region directs body movement. But until recently they haven't discovered that this huge motor is part of the brain's "reward system", the mental network that controls sexual arousal, feelings of pleasure, and motivation for rewards. And what is the neurotransmitter that is released during activation of the caudate nucleus? The dopamine, a substance very involved in motivation, that is, it helps us to detect and perceive a reward, discriminate between several and wait for one of them. Generate the motivation to get a reward and plan the specific moves to get it. The caudate is also associated with the act of paying attention and learning.

This study also found activity in other regions of the reward system, including the septum areas and the ventral tegmental area (AVT). This last region is also associated with the release of a huge amount of dopamine and norepinephrine, which is distributed throughout the brain, including the caudate nucleus. When this occurs, attention narrows, the person appears to have more energy, and you may experience feelings of euphoria and even mania.

The conception of love from this research

From studying it, Helen Fisher radically changed the way of thinking about love. Love used to be considered to involve a range of different emotions ranging from euphoria to despair. After this study, she comes to the conclusion that love is a powerful motivational system, a basic matchmaking drive. But why is it an impulse and not an emotion (or a range of emotions)?

• It is difficult for passion to disappear like any other impulse (hunger, thirst, etc), in addition to being difficult to control. Unlike emotions that come and go.

• Romantic love it focuses on obtaining the gratification of a specific reward: being loved. On the contrary, emotions are linked to an infinity of objects, such as fear, which is associated with darkness or being assaulted.

• There is no different facial expression for romantic love, other than the basic emotions. All basic emotions have a facial expression that is specific only during the onset of that emotion.

• Last but not least, romantic love is a need, a longing, an urge to be with the loved one.

The chemical waterfall of love

Everything I have described is related to what romantic love (or infatuation) would be, that which is felt in the first moments when we are obsessed with being loved. For Helen Fisher, romantic love evolved in the brain to direct all our attention and motivation on a specific person. But this does not end here. To make love more complex, this brain system that generates a force as intense as romantic love it is also intrinsically related to two other basic mating drives: the sexual impulse (desire) and the need to establish deep bonds with the partner (attachment).

Sexual desire is what allows an individual to perpetuate the species through reproduction with an individual of the opposite sex. The hormones involved in this impulse are androgens, made up of estrogen, although fundamentally, testosterone is the most committed to this function, both in men and women. The areas that are activated in the brain when there is the sexual impulse are: the anterior cingulate cortex, other subcortical regions, and the hypothalamus (involved in the release of testosterone).

In the case of romantic love, as we discussed, it is related to focusing attention on one individual at a time, in such a way that time and energy are saved for courtship. The neurotransmitter par excellence is dopamine, although it is accompanied by norepinephrine and a decrease in serotonin. The areas that are functional to this system are: mainly the caudate nucleus and in turn the ventral tegmental area, the insula, the anterior cingulate cortex and the hippocampus.

Attachment and its relationship with oxytocin and vasopressin

And finally, as the couple strengthens the bond and deepens their relationship, attachment arises, a system whose function is to allow two individuals to tolerate each otherat least long enough to achieve parenting during infancy. It is closely related to the decrease in dopamine and norepinephrine, which leads to a considerable increase in two hormones that allow this function: oxytocin and vasopressin. The neural circuits that produce such neurotransmitters are the hypothalamus and the gonads.

Each of these three brain systems evolved to fulfill a specific function for mating. Desire evolved to allow sexual reproduction with almost any more or less suitable partner. Romantic love allowed individuals to focus on only one partner at a time, thereby saving considerable time and energy for courtship. And attachment resulted in men and women being together long enough to raise a child during infancy.

The heart is in the brain

Regardless of the fact that such systems generally appear the way they have been explained (sexual desire, romantic love and finally attachment), they do not always occur in this order. Some friendships (attachment) over the years awaken a deep love that can lead to love or a friendship ruined by a broken heart. Even, It is possible to feel sexual attraction for one person, romantic love for another and a deep attachment for another.. This theory that opens a question when trying to explain such an interesting and unloved behavior in a relationship, infidelity.

Anyway, it is interesting that we are getting closer to understanding how such a small mass of only 1.3 kg, that is, the brain, can generate something as complex as love, an impulse so strong as to be the subject of so many songs, novels, poems, stories and legends.

Bibliographic references:

• Fisher, H. (2004). Why We Love: Nature and Chemistry of Romantic Love. Santa Fe and Bogotá: Taurus Thought
• Fisher, H. (1994) Anatomy Of Love: Natural History Of Monogamy, Adultery, And Divorce. Barcelona: Anagram
• Fisher, H. [TED]. (2007, January 16). Helen Fisher talks to us about why we love and cheat [Video file]. Recovered from https://www.youtube.com/watch? v = x-ewvCNguug
• Pfaff, D. (1999), DRIVE: Neurobiological and Molecular Mechanisms of Sexual Motivation, Cambridge, Mass.: The MIT Press.