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Biology 202
2001 Second Web Report
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Love and Neurobiology: Not So Strange Bedfellows

Melissa Hoegler

"The moment you have in your heart this extraordinary thing called love and feel the depth, the delight, the ecstasy of it, you will discover that for you the world is transformed." -J. Krishnamurti

Love is one of life's great mysteries. People live and build their lives around love. For many people, love, or the quest to find love, is a reason to get out of bed in the morning. Love is arguably the most overwhelming of all emotions. Many ideals and religions consider the bond of love sacred. But, why do people fall in love? Is romantic love an enigma, or can it be reduced to the presence of certain chemicals and neurotransmitters within the brain at a given time?

In the hit movie Roxanne, Steve Martin plays an articulate, put-together fire chief. However, when he falls in love with Roxanne, he acts crazy and performs dangerous acrobatics on her balcony in an attempt to earn her love. In Titanic, the two lovebirds risk it all in a vein attempt to pursue their love. And, in Shakespeare's classic, Romeo and Juliet, the love struck Venetians deny their families and take their own lives in the name of love. What causes this temporary insanity that most everyone encounters at some point in his or her life? Many believe that love is spontaneous and inexplicable, however many neurobiologists disagree. They stand by the idea that the brain causes all behavior, even love.

The scientific definition of love is "having stimulation that one desires" (5). Recent research by two British neurologists concludes that love is linked to certain brain activities. By conducting tests using a magnetic resonance imager, the scientists measured brain activity in 17 people while they were viewing a picture of their loved one, and while they were viewing a photo of a friend of the same sex as their lover. When the individuals see the picture of the person they love, clear activity occurs in four regions of the brain that were not active when the image of the friend was present. The media insula, which is responsible for instinctual feelings, and the anterior cingulate, which acts in response to euphoria-inducing drugs, such as cocaine, are the two areas of the cortex stimulated by pictures of a lover. The striatum, that is activated when we are rewarded and the prefrontal cortex also increase their activity when shown the same picture. Interestingly, the prefrontal cortex is an area within the brain that is often overactive in the brains of the depressed (1). Perhaps this is why people in love often act out of character, like the characters in the movies.

Or maybe the reason people in love act fanatical is because of the decrease in serotonin associated with being in love. While studying obsessive compulsive disorder (OCD), Donatella Marazziti discovered that levels of serotonin are especially low in people with the disorder. Marazziti hypothesized that people in love often experience feelings and symptoms similar to those with OCD, such as uncontrollable thoughts. She then proceeded to test the level of serotonin in the brains of people in love, and discerned that the level of serotonin within the brain of person in love depletes to the same point as a person with OCD (about 40% less). She also found that people with a low presence of serotonin in the brain are more susceptible to fall in love and engage in sexual activity. Because levels of serotonin cannot be measured within the brain precisely and the sample used for this research was small and mostly female, Marazziti's research is controversial, but noteworthy, nonetheless. Perhaps the idea the idea that love makes people crazy, which is mirrored by Hollywood, has a little truth to it after all (2).

But where does love come from? It originates in the neocortex, while other primitive emotions, such as fear, stem from the amygdala. These two areas of the brain share the same neural pathway (3). Animals without a neocortex, such as reptiles, are obviously incapable of love. This might be why baby snakes have to hide from their mothers so they are not eaten. According to reputable research, the link between the neocortex and the brain is extremely important because without it, people would not be able to determine how they feel about things. Research done on people with damage to their neocortex demonstrates that although these individuals retain their intellectual abilities, their inability to function on an emotional level makes everything in their lives fall apart. They are unable to ascertain a sense of self-awareness. For example, if a person with a damaged neocortex makes a bad decision, he will be likely to repeat the same mistake, because he cannot determine how he felt about the decision he made (4).

Humans are dependent on evaluating and responding to other people's emotional signals, such as body language, and this happens in the neocortex. Emotions are read in neural networks that categorize the information according to the past experience of the individual. One idea is that as children, individuals develop a template of the people they love. As adults, when a person meets someone who demonstrates qualities like those in the template, a feeling of yearning to have the template filled again follows. When the yearning to have the template filled and the stimulus this feeling provides is accepted and desired, feelings of infatuation and sometimes love follow (5). These feelings are initially triggered by phenylethylamine (PEA). PEA causes feelings of elation. When injected into mice they demonstrate feelings of delight, by jumping, frolicking, and squealing. The feeling caused by PEA is only present for a limited amount of time, because the brain grows used to its presence. So, why do some love affairs last? One theory is the increased presence of the hormone oxytocin within the brain sustains love. Oxytocin can be released through intimate contact with another person, with or without touching. It produces a release of dopamine, which is related to addiction. This may be why people in love are so attached to one another. Brien A. Seely, M.D., writes that love's, "staying power probably derives from a sturdy process of protein synthesis" (3).

Thomas Lewis' would disagree. In his book, "A General Theory of Love," Lewis, et al assert that our nervous systems are not an autonomous or self-contained. By drawing on new brainwave research, the authors conclude that the brain is constantly being "rewired" by intimate contact with others. Lewis argues that when two people are close their brains form a bond and change (6) . This theory may shed light on the much quoted Erich Fromm line, "In love the paradox occurs that two beings become one and yet remain two." However interesting, this theory is not widely accepted.

Although there is some information that explains the physiological mechanisms behind falling in love, it does not make love any easier to understand. For example, why is love such a vital part of life? Feelings of love and attachment come naturally to people, but why? What is its purpose? The presence of love in the world cannot just be for the proliferation of the human race. Homosexuals, monks, and priests all experience love that has nothing to do with reproduction. Why is it that emotions, specifically love, have the ability to override intellectual reasoning? Why is it that all love does not last forever? As of now, these questions are unanswered, and perhaps the ambiguity surrounding love is one of the things that makes it so desirable.

WWW Sources

1)So you think you're in love?, a quick article from the New Scientist that talks about the parts of the brain stimulated by love.

2)Love Sick , also an article from the New Scientist. This article discusses the similarities between love and OCD.

3)What is Love, Medically Speaking, An essay on love from a medical perspective

4)The EQ Factor, A fascinating article from Time Magazine that talks about Emotional intelligence..

5)The Evolutionary Antecedents to Love, From Psychoneuroendocrinology, an article about the brain and behavior, specifically sexual behavior

6) Lewis, Thomas. A General Theory of Love. New York: Random House, 2000., available from TRIPOD

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