7 Amazing Facts About the Amygdala

We tend to think of our brains as one big organ inside our skulls, but it’s actually comprised of many, small structures that make it possible for us to walk, talk, think, and feel. Of these, one of the more well-known structures, the amygdala, has been found to play a hugely important role in many social and emotional processes—influencing everything from health to addiction.

Mental_floss spoke to Rahul Jandial, a neurosurgeon and neuroscientist at City of Hope Cancer Center in Los Angeles, California, and Brandon Brock, a staff clinician at the Cerebrum Health Centers Brain Initiative Group in Texas, about this fascinating part of the brain.

1. IT'S NOT REALLY ONE STRUCTURE …

One of the more well-known structures, the amygdala is located within the depths of the anterior-inferior temporal lobe. The almond-shaped region is part of the limbic system and is actually a paired structure, with parts in each temporal lobe, according to Jandial.

He says you can survive with only one of the two: “How do I know? I can surgically remove one as part of a brain surgery called selective amygdalohippocampectomy.” In fact, in studies where rats, monkeys, or rabbits have their amygdala removed, the animals live normal lives except for one notable new development: They don’t feel fear.

2. … BECAUSE THE AMYGDALA IS YOUR BRAIN'S FEAR FACTORY.

Your fear of snakes and scary movies is in large part due to the function of your amygdala, which “responds before frontal lobes weigh in,” Jandial says. It’s part of your instinctive brain and serves as your “emotional thermostat.” He adds, “It’s not in charge of just fear, but all deep and visceral emotions—one of those ancient brain regions that can defy the frontal lobe request.”

According to a 2007 study in Social Cognitive and Affective Neuroscience, “amygdala activity may represent the generation of emotional experience itself, and/or it may reflect sundry aspects of emotional information processing correlated with emotional experience.”

3. THE AMYGDALA ALSO HAS A TRUE MIND-BODY CONNECTION.

And yet the amygdala has purposes beyond fear. It has been shown to assist in emotional learning, “whereby cues acquire significance through association with rewarding or aversive events,” according to a paper in Current Opinion Neurobiology. More recent research, the authors write, suggest that the amygdala regulates additional cognitive processes, such as memory or attention.

With its ability to interpret sensory stimuli in the world and translate them into physical reactions, the amygdala, as a research paper in Social Cognitive and Affective Neuroscience suggests, “may thus represent embodied attention—the crucial link between central (mental) and peripheral (bodily) resources.”

4. DAMAGE TO THE AMYGDALA CAN LEAVE YOU HORNY AND HUNGRY.

An injured amygdala can leave a person “super hungry, sexually aroused, and fixated with putting things in their mouth,” says Jandial. In other cases, it can lead to a reduced fear of risks, and thus an increase in risky behavior. Researchers found that adult monkeys who were given amygdalectomies “showed more pro-social cues and less avoidance behaviors toward other (healthy) monkeys.” In one extreme case, damage to the amygdala shut down one woman’s ability to feel fear altogether.

5. IT ALSO PLAYS A ROLE IN PAIN.

Fibromyalgia is a disease characterized by "widespread musculoskeletal pain with diffuse tenderness at multiple tender points,” as a study in Clinical Neuroscience describes. Brock says that changes in the amygdala’s volume and function play a role in both fibromyalgia and chronic pain syndromes. This appears to be a consequence of the amygdala becoming hypervigilant and oversensitized to internal sensations of pain or trauma, according to a study in Explore. “This results in exhaustion of the neuro-endocrine and immune systems and chronic physical and mental exhaustion, as well as many secondary symptoms and ongoing complications.”

6. THE AMYGDALA IS KEY TO UNDERSTANDING ADDICTION.

Addiction is considered a brain disease by the medical community rather than a lack of willpower or a character defect. According to a study in Brain Research, a common addiction cycle comprises three stages—“preoccupation/anticipation, binge/intoxication, and withdrawal/negative affect—in which impulsivity often dominates at the early stages and compulsivity dominates at terminal stages.” The amygdala becomes recruited in the final withdrawal stage, where it sends stress signals to the body, driving a person to crave more of their substance.

7. DESPITE ADVANCES IN BRAIN-IMAGING TECHNOLOGY, IT'S STILL DIFFICULT TO STUDY.

Though we know much more about the amygdala since it was first discovered in the 1930s in monkeys, there’s still much to learn. Because of the amygdala’s deep brain location and its entanglement with other neighboring brain structures, it’s difficult to find “exact ways to monitor its function, output and all regions that it has a synaptic influence on. Time and further scientific research will hopefully unveil that,” Brock explains.

10 Facts About Your Tonsils

iStock/Neustockimages
iStock/Neustockimages

Most of us only become aware of our tonsils if they become swollen or infected. But these masses of lymphatic tissue in the mouth and throat are important immunological gatekeepers at the start of the airways and digestive tract, grabbing pathogens and warding off diseases before they reach the rest of your body. Here are some essential answers about these often-overlooked tissues—like what to do when your tonsils are swollen, and whether you should get your tonsils removed.

1. People actually have four kinds of tonsils.

The term tonsils usually refers to your palatine tonsils, the ones that can be seen at the back of your throat. But tonsillar tissue also includes the lingual tonsil (located in the base of the tongue), tubal tonsils, and the adenoid tonsil (often just called adenoids). "Collectively, these are referred to as Waldeyer's ring," says Raja Seethala, the director of head and neck pathology at the University of Pittsburgh Medical Center and a member of the College of American Pathologists Cancer Committee.

2. Tonsils are one of the body's first responders to pathogens.

The tonsils are a key barrier to inhaled or ingested pathogens that can cause infection or other harm, Seethala tells Mental Floss. "These pathogens bind to specialized immune cells in the lining—epithelium—to elicit an immune response in the lymphoid T and B cells of the tonsil," he says. Essentially, they help jumpstart your immune response.

3. Adenoid tonsils can obstruct breathing and cause facial deformities.

If the adenoid tonsils are swollen, they can block breathing and clog up your sinus drainage, which can cause sinus and ear infections. If adenoids are too big, it forces a person to breathe through their mouth. In children, frequent mouth breathing has the potential to cause facial deformities by stressing developing facial bones. "If the tonsils are too large and cause airway obstruction, snoring, or obstructive sleep apnea, then removal is important," says Donald Levine, an ear, nose, and throat specialist in Nyack, New York. Fortunately, the adenoids tend to get smaller naturally in adulthood.

4. As many of us know, sometimes tonsils are removed.

Even though your tonsils are part of your immune system, Levine tells Mental Floss, "when they become obstructive or chronically infected, then they need to be removed." The rest of your immune system steps in to handle further attacks by pathogens. Another reason to remove tonsils besides size, Levine says, is "chronic tonsillitis due to the failure of the immune system to remove residual bacteria from the tonsils, despite multiple antibiotic therapies."

5. Tonsillectomies have been performed for thousands of years ...

Tonsil removal is believed to have been a phenomenon for three millennia. The procedure is found in ancient Ayurvedic texts, says Seethala, "making it one of the older documented surgical procedures." But though the scientific understanding of the surgery has changed dramatically since then, "the benefits versus harm of tonsillectomy have been continually debated over the centuries," he says.

6. ... and they were probably quite painful.

The first known reported case of tonsillectomy surgery, according to a 2006 paper in Otorhinolaryngology, is by Cornélio Celsus, a Roman "encylopaediest" and dabbler in medicine, who authored a medical encyclopedia titled Of Medicine in the 1st century BCE. Thanks to his work, we can surmise that a tonsillectomy probably was an agonizing procedure for the patient: "Celsus applied a mixture of vinegar and milk in the surgical specimen to hemostasis [stanch bleeding] and also described his difficulty doing that due to lack of proper anesthesia."

7. Tonsil removal was performed for unlikely reasons.

The same paper reveals that among some of the more outlandish reasons for removing tonsils were conditions like "night enuresis (bed-wetting), convulsions, laryngeal stridor, hoarseness, chronic bronchitis, and asthma."

8. An early treatment for swollen tonsils included frog fat.

As early practitioners struggled to perfect techniques for removing tonsils effectively, another early physician, Aetius de Amida, recommended "ointment, oils, and corrosive formulas with frog fat to treat infections."

9. Modern tonsillectomy is much more sophisticated.

A common technique today for removing the tonsils, according to Levine, is a far cry from the painful early attempts. Under brief general anesthesia, Levine uses a process called coblation. "[It's] a kind of cold cautery, so there is almost no bleeding, less post operative pain, and quicker healing. You can return to normal activities 10 days later," Levine says.

10. Sexually-transmitted HPV can cause tonsil cancer.

The incidence of tonsillar cancers is increasing, according to Seethala. "Unlike other head and neck cancers, which are commonly associated with smoking and alcohol, tonsillar cancers are driven by high-risk human papillomavirus (HPV)," he says. "HPV-related tonsillar cancer can be considered sexually transmitted."

26 Amazing Facts About the Human Body

Mental Floss via YouTube
Mental Floss via YouTube

At some point in your life, you've probably wondered: What is belly button lint, anyway? The answer, according to Mental Floss editor-in-chief Erin McCarthy, is that it's "fibers that rub off of clothing over time." And hairy people are more prone to getting it for a very specific (and kind of gross-sounding) reason. A group of scientists who formed the Belly Button Biodiversity Project in 2011 have also discovered that there's a whole lot of bacteria going on in there.

In this week's all-new edition of The List Show, Erin is sharing 26 amazing facts about the human body, from your philtrum (the dent under your nose) to your feet. You can watch the full episode below.

For more episodes like this one, be sure to subscribe here.

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