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“I Love You from the Bottom of My Hypothalamus,” or What You Need to Know about Love This Valentine’s Day

Going for a more scientifically accurate Valentine’s card this year? How about one that reads, “I love you from the bottom of my ventral tegmental area”?

It may not be the most romantic declaration of love, but the fact of the matter is that love does not originate in the heart, but rather in the brain.

3D CT scan of a human brain, with the hypothalamus highlighted in green. The hypothalamus is a deep region of the brain responsible for basic impulses like hunger, thirst and even lust.

3D MRI scan of a human brain, with the hypothalamus highlighted in green. The hypothalamus is a deep region of the brain responsible for basic impulses like hunger, thirst and even lust.

This Valentine’s Day, The Pulse guides you through a dissection of sorts that will help you make sense of what governs the head and the heart. Does love boil down to the simple impulse to propagate the species? Or is there more to it?

Call it cold-hearted, but scientists have broken down the process of falling in love into three distinct, predictable stages: lust, attraction and attachment. With each phase, different parts of the brain become more active than others. A whole host of chemicals come into play, influencing the way we think and feel.

It looks like mind cannot win over matter when it comes to love: the brain wants what the brain wants. Scientists have joined countless poets, artists and writers in attempting to decipher the true nature of love. Some scientists even reckon they have boiled love down to a set of 36 questions that can guarantee love between two people. Safe to say, scientists have the advantage with tools like functional Magnetic Resonance Imaging (fMRI) and Positron Emission Tomography (PET) that enable them to image the brain and the chemical reactions going on inside.

When you first see someone you feel attracted to, primal instincts evolved over millions of years kick in. The hypothalamus, the region of the brain that regulates basic impulses like hunger and thirst, releases a chemical called phenylethylamine (PEA). PEA leads to the release of other endogenous chemicals such as testosterone (in both men and women). Your heart races, your breathing gets faster, and your palms begin to sweat. Classic signs that you’re into someone.

Spend some time getting to know this person, and your brain will decide whether they are a good match (based on several factors that are still up for debate, like how healthy you think your offspring would be or what your parents look like). If you do deem them suitable, the next phase of love sets in: attraction.

Studies show that the attraction phase occurs via the brain’s nucleus accumbens and ventral tegmental area, home to the brain’s reward system. These regions are flooded with dopamine, the brain’s main ‘feel-good’ chemical, triggering the same response seen when using cocaine. Other chemicals related to stress and excitement also spike: cortisol, phenylephrine and norepinephrine.

Vivid™ E9 with XDclear Cardiovascular Ultrasound with color flow Doppler of the pulmonary veins in a healthy heart.

Image of pulmonary veins in a healthy heart using Color Flow Doppler. Blood flowing toward the transducer from the lungs is colored red, while blood flowing away from the transducer to the rest of the body is colored blue. Image obtained with the Vivid™ E9 with XDclear™.

Interestingly, serotonin drops in the early attraction phase, or ‘new love’. Low serotonin levels are a symptom of Obsessive Compulsive Disorder (OCD), depression and anxiety. Which explains why new lovers will spend inordinate amounts of time obsessing over each other.

When the dopamine-fueled thrill of new love dies down, and you settle into a routine with your new partner, you will be in what is called the attachment phase. This phase is mainly driven by oxytocin and vasopressin. These are known as the brain’s ‘calming’ chemicals. Oddly enough these also come from the hypothalamus, where lust originates. These chemicals accompany the feelings of closeness and coziness that come with a long-term relationship. Oxytocin is also called the ‘cuddle’ hormone, as it spikes in moments of close bonding.

But what about breakups? Studies show that the changes that the brain undergoes after a heavy breakup are akin to those seen after traumatic physical injury. In some cases, physical injury may actually happen as a result. The brain and the heart may be linked in love after all.

Click below to see our gallery of Valentine’s Day photos showing the science behind romance and the fascinating ways our bodies change when we meet that special someone.