Neurobiology of love: the theory of the 3 brain systems

Love is one of the most complex phenomena that we humans are able to experience. This particular feeling has made people wonder how and why this happens. Science has also dealt with this phenomenon, and one of the best-known researchers in this field of research is Helen Fisher, A biologist and anthropologist who has spent over 30 years trying to figure this out.

Helen Fisher’s research

To try to explain this complex feeling, Fisher focused on trying to understand the brain mechanisms involved in the process of falling in love and falling in love. To do this, he submitted several subjects who were madly in love with IMRF scanners, in order to discover the areas of the brain that activate when the subject thinks of their loved one.

“Love” and neutral photographs

To perform the tests, Helen asked study participants to bring two photographs: one of the loved one and one that had no special meaning, i.e. a neutral face. Then, once the person was put into the brain scanner, the image of the loved one was first displayed on the screen for a few seconds while the scanner recorded blood flow to different regions of the brain.

Individuals were then asked to look at a random number, then they had to subtract seven by seven, then look at the neutral photograph where a scan would again be performed. This was repeated several times to obtain a large number of brain images and thus ensure the consistency of what was obtained by looking at the two photographs.

Research results

There were many parts of the brain that were activated in the lovers who invented the experience. However, there appear to be two regions that place particular emphasis on the sublime experience of being in love.

Perhaps the most important discovery was the activity of the caudate nuclei. This is a large “C” shaped region that is very close to the center of our brain. It is primitive; is part of what is called the brain of reptiles, because this region evolved long before the proliferation of mammals, about sixty-five million years ago. Scans showed that there were parts of the body and tail of the caudate nucleus that became particularly active when a lover looked at his lover’s photo.

The brain’s reward system is important for falling in love

Scientists have long known that this region of the brain directs the movement of the body. But until recently, they didn’t find out that this enormous motor is part of the brain’s “reward system”., The mental network that controls sexual arousal, feelings of pleasure, and motivation to gain rewards. And what is the neurotransmitter that is released upon activation of the caudate nucleus? Dopamine, a substance very involved in motivation, that is to say it helps us to detect and perceive a reward, to distinguish several of them and to expect one. Generate motivation to get a reward and plan specific moves to get it. Caudality is also associated with the act of paying attention and learning.

In this study, activity was also found in other regions of the reward system, including the areas of the septum and the ventral tegmental area (AVT). This latter region is also associated with the release of an enormous amount of dopamine and norepinephrine, which is distributed throughout the brain, including the caudate nucleus. When this happens, attention is reduced, the person seems to have more energy and you may experience feelings of euphoria and even mania.

The conception of love resulting from this research

From her study, Helen Fisher radically changed the way she thinks about love. Love was once thought to involve a range of different emotions ranging from euphoria to despair. After this study, we conclude that love is a powerful motivational system, a basic impetus for mating. But why is it an impulse and not an emotion (or a range of emotions)?

  • It’s hard for passion to fade like any other impulse (Hunger, thirst, etc.), in addition it is difficult to control. Unlike the emotions that come and go.

  • Romantic love focuses on obtaining the satisfaction of a specific reward: being loved. In contrast, emotions are linked to countless objects, such as fear, associated with darkness or aggression.

  • There is no differentiated facial expression for romantic love, Different from basic emotions. All basic emotions have a facial expression that is only specific at the start of that emotion.

  • Last but not least, romantic love is a necessity, a desire, An impulse to be with the loved one.

The chemical cascade of love

Everything I have described has to do with what romantic love (or falling in love) would be like, which is felt in the first few moments when we become obsessed with being loved. For Helen Fisher, romantic love evolved in the brain to direct all of our attention and motivation to a specific person. But it does not stop there. To make love more complex, this brain system that generates a force as intense as romantic love it is also intrinsically linked to two other basic impulses for mating: The sexual drive (desire) and the need to establish a deep bond with the partner (affection).

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 boost are androgens, which are made up of estrogen, although testosterone is primarily most involved in this function in both men and women. The areas that are activated in the brain when there is a sexual urge are: the anterior cingulate cortex, the other subcortical regions and the hypothalamus (involved in the release of testosterone).

In the case of romantic love, as we are dealing with it, it is about focusing attention on one individual at a time, thus saving time and energy for those around them. The neurotransmitter par excellence is dopamine, although it is accompanied by norepinephrine and a decrease in serotonin. The functional areas of this system are: mainly the caudate nucleus and in turn the ventral tegmental area, the insula, the anterior cingulate cortex and the hippocampus.

The condition and its relationship to oxytocin and vasopressin

And finally, as the couple bond and deepen their relationship, tilt arises, a system whose function is to allow two individuals to tolerate each otherAt least long enough to become a parent during childhood. It is closely related to the decrease in dopamine and norepinephrine, leading to a dramatic increase in two hormones that enable such a function: oxytocin and vasopressin. The neural circuits that produce such neurotransmitters are the hypothalamus and the gonads.

Each of these three brain systems evolves to perform a specific mating function. Desire has evolved to allow sexual reproduction with almost any more or less suitable partner. Romantic love allowed individuals to focus on one couple at a time, thus saving a lot of time and energy for those around them. And this affection has kept men and women together long enough to raise a child through childhood.

The heart is in the brain

Regardless of how these systems generally appear in the way they have been explained (sexual desire, romantic love, and ultimately affection), it is not always given in that order. Some friendships (affection) over the years awaken a deep love that can lead to love or friendship ruined by a broken heart. even, it is possible to feel sexual attraction to one person, romantic love for another, and deep affection for another. This theory that opens a question when trying to explain a behavior as interesting as little liked in a relationship, infidelity.

Anyway, it’s interesting that we come to understand how such a small mass of only 1.3 kg, i.e. the brain, can generate something as complex as the love, an impulse so strong that it is the subject of so many songs, novels, poems, tales and legends.

Bibliographical references:

  • Fisher, H. (2004). Why we love: Nature and chemistry of romantic love. Santa Fe and Bogota: 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 explains why we love and cheat [Archivo de video]. Retrieved from
  • Pfaff, D. (1999), DRIVE: Neurobiological and Molecular Mechanisms of Sexual Motivation, Cambridge, Massachusetts: The MIT Press.

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