We Are Our Brains

As we get closer to Valentine’s Day, esteemed neurobiologist Dick Swaab takes a look at love on physiological perspective: what happens to our brains when we fall in love? Find out in this exclusive extract from his fascinating new book We Are Our Brains.

LOVE, n. A temporary insanity curable by marriage – Ambrose Bierce (1842– c. 1914)

A great many brain processes are involved in various stages of our love lives, including falling in love, sexual arousal, attachment leading to long-term partner bonding, and maternal and paternal behaviour. Although it wasn’t Mother Nature’s “intention,” we see on a daily basis that these stages can perfectly well exist independently of one another, and I will therefore look at them separately.

FIGURE 15. The prefrontal cortex (PFC) as seen from the side (external view at top, cross section at bottom).

FIGURE 15. The prefrontal cortex (PFC) as seen from the side (external view at top, cross section at bottom).

No one who can still remember the suddenness and intensity of falling passionately in love will classify partner choice as a free choice or even a well- considered decision. Love at first sight just happens— it is pure biology— along with all the euphoria and severe physical reactions that ensue, like a beating heart; perspiration and insomnia; emotional dependency; strongly focused attention; an obsessive, possessive, and protective attitude toward the partner; and a feeling of heightened energy. Plato (427– 347 b.c.) was equally convinced of the autonomy of this process. He regarded the sexual impulse as a fourth species of soul, located below the navel, describing it as “rebellious and masterful, like an animal disobedient to reason.”

For people all over the world, falling in love tends to be the basis for pair forming. You might think that where something as important as choosing someone to start a family with is concerned, our cerebral cortex would select the right person on a fully conscious basis. But no, during severe infatuation, when all of our attention and energy is focused on that one other person, it’s the areas down at the base of the brain, in structures that steer unconscious processes, that call the shots.

Brain scans of people who had just fallen deeply in love and who were shown a photograph of their significant other showed activity exclusively in brain structures below the cerebral cortex. Their reward circuitry was particularly active. This part of the brain focuses on obtaining a reward (in this case, for finding partner) in the form of a pleasurable sensation, which is transmitted by the chemical messenger dopamine (fi g. 16). The reward system isn’t involved just in matters of the heart but in everything that we find pleasant. It’s also associated with addiction, which explains why people experience severe withdrawal symptoms when a love affair ends. Scans show this system to be primarily activated on the right side of the brain, in proportion to the attractiveness of the face in the photo and the intensity of the romantic passion.

People who are in love also have raised levels of the stress hormone cortisol. Being in love is a stressful situation, and the body responds by producing more of this hormone. The level of testosterone (also produced by the activated adrenal gland) increases in women who are in love, while in men, cortisol reduces the testicular production of testosterone.

FIGURE 16. The dopaminergic reward system, originating in the cell bodies in the ventral tegmental area (1), whose fi bers extend into regions including the ventral striatum (ventral pallidum/nucleus accumbens [2]), the caudate nucleus (3), and the prefrontal cortex (4).

FIGURE 16. The dopaminergic reward system, originating in the cell bodies in the ventral tegmental area (1), whose fi bers extend into regions including the ventral striatum (ventral pallidum/nucleus accumbens [2]), the caudate nucleus (3), and the prefrontal cortex (4).

It’s only when love has persisted for a certain length of time that the prefrontal cortex, the front part of the brain involved in planning, deliberation, and assessment, becomes involved. If stable pair formation ensues, the activity in the stress axis dies down and testosterone levels return to normal. The processing of sensory information in the cerebral cortex has of course played a role during that exciting period— we have, after all, seen, smelt, and touched the person we love. But this isn’t the same thing as making a conscious choice for that particular person. Whether they are “Mr. (or Ms.) Right” is determined by our ancient reward circuitry, which thus links reproduction to the “right” partner— or at least the right partner in that moment. Only when the most intense period of infatuation has passed does the cerebral cortex take over. So if your son or daughter suddenly falls for the wrong person, it’s no good reproaching them that they should have used their brains. They did, in fact, do so, but those parts of the cerebral cortex (such as the PFC) that could have come to a different decision after a balanced, conscious judgment unfortunately only kick in when it’s too late.

We Are Our Brains is available now in hardback and eBook formats. Look out for more unconventional looks at love in the lead up to Valentine’s Day by following the hashtag #lovebooks on Twitter and Facebook.

 

 

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