The Neuroscience of Love or Hatred: Chemical Warcraft
And therefore is winged Cupid painted blind1. (1.1.234-235)
He waits outside the door, hiding flowers behind his back. He knows she would love them. He can feel it in his bones. The anticipation makes him all giddy.
The door slowly creaks open, and reveals on the other side, the love of his life, Jane.
“Hi,” she smiles, although it’s a bit strained, but he doesn’t notice.
He brings out the flowers, and she jerks back a bit. And when she takes them from him, his world lights up.
“Hi. ”he replies.
“You’re back early?” she asks, discomfort clearly evident on her face.
“Surprise!” he replies. “I just wanted to spend more time with you.”
“Oh!” Her eyes search around, worry evident, until an idea flashes, and her face lights up. “In that case, let’s have dinner outside.” She puts her arm in his, and leads him out.
“Yes, but at least, keep the flowers in.” She would’ve, if only she could’ve.
“I love them so much, I don’t want to part.” That simple sentence makes him so happy, he would’ve made her a garden if she asked. “Can I take them with me?”
“Sure, love.” Anything for her. She shuts the door, and they go away. He never notices that she left the door slightly ajar.
Emotions are governed by a complex set of connections in the brain called the limbic system. How we perceive emotional stimuli and how we respond emotionally, is all controlled by the limbic system. Here we will analyze some circuitry of John Doe’s brain.
One important circuit in the limbic system is the mesolimbic pathway, a major neurochemical pathway of the reward system. It is mediated by dopamine, the motivational chemical which fuels our craving to achieve a reward2. It makes us work hard in anticipation of something wonderful. Intense romantic love is associated with subcortical reward regions that are also dopamine-rich3.
The anticipation of Jane’s smile released a gush of dopamine in John’s brain. It made him go an extra mile to get her some flowers. Most of our understanding of emotions comes from studies of voles4, 5. Voles are quite like humans when it comes to relationships.
When a female prairie vole is mated with a male, she forms a distinct preference for her partner. However, when a dopamine agonist is infused into the nucleus accumbens, she begins to prefer a male present at the time of infusion, even if she has not mated with this male4. The idea that our relationships can so easily be manipulated is quite scary, and yet, intriguing.
Oxytocin is the “cuddle” hormone. It involves bonding and trust. Vasopressin is a close relative. They are the ‘feel good’ chemicals. They increase generosity and empathy, and you see the world through rose-colored spectacles6.
Amygdala is a part of the limbic system, and it has much to do with emotions, especially fear6, 7. If you’re walking down an alley, and you feel you’re being pursued, that’s the amygdala firing, trying to warn you. Your cingulate cortex is critical for self-awareness8.
Consider watching a horror movie. While your amygdala is probably scared out of its wits, your cingulate cortex keeps mumbling to you, “Relax, it’s just a movie. You’re safe.”
When you’re in love, the oxytocin completely smothers the amygdala, and your ability to detect a threat is impaired9. This is probably why most people fail to see the abusive nature, or in John’s case, evident infidelity of their partner. Since amygdala is the fear center, love (oxytocin) will make you take a bullet for them, too9. Although proved to be an anxiolytic10, 11, it won’t be long before we have our very own “love potion”.
Now, if by chance, John does stumble upon Jane’s infidelity, he’d lose faith in love. Just like a child, who nearly drowns, is afraid of taking a bath. When such incidents happen, the amygdala makes new connections (synaptic plasticity) with the cingulate cortex12. Since the memory is still recent, the cingulate cortex keeps reminding the amygdala through these newly made connections to not repeat the history. However, as time passes, and the memory becomes remote, the connections between the cortices and amygdala weaken12.
“It has been said, ‘time heals all wounds.’ I do not agree. The wounds remain. In time, the mind, protecting its sanity, covers them with scar tissue and the pain lessens. But it is never gone.”
So, time would help John trust again, and with time, the child will embrace the water again, but the horrors of the past shall always remain engraved deep in their minds. Such is the complexity of our brains. The connections it made will remain, and even if we forget, the mind will remember forever.
Although much work has been done on the “science of love”, the same cannot be said about hate. Welcome Laboratory of Neurobiology, UK, performed and analyzed the MRI brain scans of 17 volunteers while showing them pictures of neutral as well as hateful people13. Turns out, the hate pattern is quite distinct from that of other closely related emotions such as fear, anger, aggression and danger13. Yet, the parts of the right putamen and the medial insula activated in this study correspond closely to the parts activated in an earlier study of romantic love14.
Simply put, hate relates more to love than it does to the other emotions we often see where hate exists. This probably explains why most of our fictional romantic characters, who simply can’t stand each other, end up falling in love. Beware! If this is true, love may also turn to hatred, or more amazingly, both may coexist, and we will, finally, have an explanation for our love-hate relationship with medicine.
1. Shakespeare, William. A Midsummer Night’s Dream. 1596
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3. Aron, Arthur, Helen Fisher, Debra J. Mashek, Greg Strong, Haifang Li, and Lucy L. Brown. “Reward, motivation, and emotion systems associated with early-stage intense romantic love.” Journal of neurophysiology 94, no. 1 (2005): 327-337.
4. Gingrich, Brenden, Yan Liu, Carissa Cascio, Zuoxin Wang, and Thomas R. Insel. “Dopamine D2 receptors in the nucleus accumbens are important for social attachment in female prairie voles (Microtusochrogaster).” Behavioral neuroscience 114, no. 1 (2000): 173.
5. Liu, Y., and Z. X. Wang. “Nucleus accumbens oxytocin and dopamine interact to regulate pair bond formation in female prairie voles.” Neuroscience 121, no. 3 (2003): 537-544.
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9. Kirsch, Peter, Christine Esslinger, Qiang Chen, Daniela Mier, Stefanie Lis, SarinaSiddhanti, HaraldGruppe, Venkata S. Mattay, Bernd Gallhofer, and Andreas Meyer-Lindenberg. “Oxytocin modulates neural circuitry for social cognition and fear in humans.” The Journal of Neuroscience 25, no. 49 (2005): 11489-11493.
10. de Oliveira, Danielle CG, Antonio W. Zuardi, Frederico G. Graeff, Regina HC Queiroz, and José AS Crippa. “Anxiolytic-like effect of oxytocin in the simulated public speaking test.” Journal of Psychopharmacology 26, no. 4 (2012): 497-504.
11. Ditzen, Beate, Marcel Schaer, Barbara Gabriel, Guy Bodenmann, Ulrike Ehlert, and Markus Heinrichs. “Intranasal oxytocin increases positive communication and reduces cortisol levels during couple conflict.” Biological psychiatry 65, no. 9 (2009): 728-731.
12. Toyoda, Hiroki, Xiang-Yao Li, Long-Jun Wu, Ming-Gao Zhao, GianninaDescalzi, Tao Chen, Kohei Koga, and Min Zhuo. “Interplay of amygdala and cingulate plasticity in emotional fear.” Neural plasticity 2011 (2011).
13. Zeki, Semir, and John Paul Romaya. “Neural correlates of hate.” PloS one 3, no. 10 (2008): e3556.
14. Bartels, Andreas, and SemirZeki. “The neural correlates of maternal and romantic love.” Neuroimage 21, no. 3 (2004): 1155-1166.
About the Author: Urooj Imdad Memon is a 2nd Year Medical Student in Sindh Medical College, Dow University of Health Sciences. She’s interested in Epigenetics and Bioinformatics. Urooj represented Pakistan in International Biology Olympiad 2011, held in Taipei, Taiwan. At present, she is a member of Sehar Welfare Society, an NGO that provides free education to underprivileged children. She can be reached at email@example.com
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