While it has numerous biological functions, the prime role of the amagdala is to process negative emotional stimuli. Significant changes to normal amygdala activation are associated with serious psychological disorders. For example, human schizophrenics have significantly less activation in the amygdala and the memory system (the hippocampus), which is due to a substantial reduction in the size of these areas. People with depression, anxiety, and attachment insecurity, on the other hand, have significantly increased blood flow in the amygdala and memory system.
Neuroscientist Justin Feinstein and his colleagues (2010) studied a woman whose amygdala was destroyed after a rare brain condition. They exposed her to pictures of spiders and snakes, took her on a tour of the world’s scariest haunted house, and had her take notes about her emotional state when she heard a beep from a random beeper that had been attached to her. After three months of investigation, the researchers concluded that the woman could not experience fear. This is very good evidence for the idea that the amygdala is the main center for fear processing. (The chief competing hypothesis is that fear is processed in a brain region that receives its main information from the amygdala.)
Despite its tiny size, the amygdala is amazingly powerful. When its neurons fire intensely, this triggers a physical stress response in your body. Hans Selye, a Canadian endocrinologist, was the first to apply the word “stress” to physical and emotional strain. Before that, “stress” was just an engineering term. Selye, who did the bulk of his research in the 1930s, discovered that the stress hormone cortisol had detrimental health effects in rats.
Together with other adrenal gland hormones, such as epinephrine (adrenaline) and norepinephrine (noradrenaline), cortisol prepares the body for a “fight or flight” response. Stress hormones are secreted in situations of perceived danger. They can be aggressively rushing through the bloodstream, even when the danger isn’t real. For example, they run rampant in people with a fear of public speaking. They make your heart breakdance, your skeleton turn to gelatin, and your new Mickey Mouse voice make little squeaks the first time you stand in front of a hundred-person audience.
Falling in love then goes like this. Unpredictability, mystery, and sexual attraction make the amygdala go into a hyper-activation mode. Via neurotransmitters, this signals to the adrenal glands that something exciting, scary, mysterious, and unpredictable is going on. This, in turn, results in the adrenal glands pumping a surge of adrenaline, noradrenaline, and cortisol into the bloodstream. Via the bloodstream, adrenaline increases heart and breathing rates; noradrenaline produces body heat, making you sweat; and cortisol provides extra energ y for muscles to use.
Though falling in love is associated with anxiety and stress, this state—in combination with the belief that there may be reciprocation—is also at times accompanied by intensely pleasant emotions. These emotions arise from an underlying brain chemistry that resembles those triggered by cocaine use.
Your Brain on Crack
Cocaine is a serotonin/norepinephrine/dopamine reuptake inhibitor, like the most frequently prescribed antidepressants. Serotonin reuptake inhibitors block the transporter that normally carries the “feel good” neurotransmitter serotonin into the neurons. When serotonin is inside the neurons, it does not function as a neurotransmitter. To have an impact on the brain, it must be extracellular, or outside the neurons. When the transporter is blocked, less serotonin is carried back into the cell. So, the extracellular levels of serotonin increase, which stabilizes the brain’s chemistry and alleviates anxiety and depression.
Cocaine increases the brain levels of serotonin, norepinephrine, and dopamine. But unlike the selective serotonin reuptake inhibitors, or SSRIs, doctors normally prescribe for depression (for example, Zoloft, Celexa, or Lexapro), cocaine works instantly. This is because cocaine is a much more potent drug. Whereas standard antidepressants only partially block neurotransporters, cocaine completely blocks them, giving rise to a steep peak in the levels of norepinephrine, dopamine, and serotonin.
Increased levels of norepinephrine make you alert and energetic, suitable levels of serotonin make you feel satiated and self-confident, and increased levels of dopamine make you go into a pleasurable manic state. Dopamine also motivates us to continue to perform certain activities by causing a feeling of profound enjoyment in response to those activities, such as sex.
Because dopamine is associated with pleasure and memory associations between certain actions and pleasure, stimulants and narcotic drugs that increase the brain’s levels of dopamine can cause addiction. The brain remembers the intense pleasure and wants it repeated. This, however, is probably not the whole story behind addiction. Though pleasurable or satisfying activities normally are necessary to initiate an addiction, it may be an overall less efficient pleasure response to ordinary events that causes addiction. It’s the pleasurable or satisfying feeling created by dopamine that entices us to try a drug a second time. But it is likely a dopamine deficiency, a smaller number of dopamine receptors, or an impairment of the function of dopamine that causes addiction. For people with an addictive personality, normal everyday activities, such as working, reading, or watching a movie, don’t lead to sufficiently intense pleasure, so they seek the drug to give them a more profound experience.
Over time, cocaine and other drug use desensitizes the brain to the drug. Desensitization happens as a result of an increased reuptake of the drug or a reduction in or desensitization of receptors. As a result, a larger amount of the drug is required to achieve the same stimulating effect.
New love can have similar effects on the brain as cocaine. Helen Fisher, an anthropologist and relationship researcher, conducted a series of fascinating brain imaging studies of the brain chemistry and brain structure underlying new love. She found that serotonin, dopamine, and norepinephrine are crucially involved in the initial stages of romantic love in much the same way as they are in cocaine use.
When you fall in love with someone, norepinephrine fills you with raucous energy, serotonin boosts your self-confidence, and dopamine generates a feeling of pleasure. New love is a kind of love addiction but not yet a kind of pathological love addiction. In falling in love, however, the brain is on crack—a dangerous state of mind.
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