It keeps us up long hours, fearing sleep. Perhaps it’s the reason we toss and turn at night, or wake up in a panic, sometimes even struggling to breathe, or why you find yourself reluctant to look at the news alerts on your phone — or read email. As advanced as our species has become over the last two centuries, it seems we cannot elude the primal state of anxiety — it’s almost always right there waiting for us. Of course, some sense it more than others. Usually, you’ve got a good reason to be worried — will your yearly job review be a good one? Did you prepare enough for your final exam? Will the hospital test results come out OK?
It’s easy to think that we’re the only ones who agonize like this over events that are all too often inevitable, but what we’re experiencing is actually something our species has long evolved with. Our primate ancestors navigated a harsh and unforgiving terrain — having to retreat to trees or caverns when nightfall came — bringing with it an array of predators. Those who survived the prehistoric times — at least long enough to produce offspring, were those who could best recognize approaching danger — to spot leopards, snakes, even larger primates, hiding in the tall savannah grasses.
Crossing paths with a striking adder would have triggered the classic “fight-or-flight response” in their brains. The response starts off when the brain’s amygdala first processes the threat. It relays a message to the hypothalamus, activating the pituitary gland that begins to secrete the hormone epinephrine, rapidly increasing blood flow to the muscles and allowing our ancestors to either flee or intimidate their attacker. The rush of chemical signals from the brain produce cortisol increasing blood sugar and blood pressure to heighten that same energy and awareness we sense in a stressful situation.
TO FLEE OR NOT TO FLEE?
From the time Walter Bradford Cannon first described this response back in 1929, we have come to equate the almond-shaped amygdala with the emotion of fear — thinking with our amygdala, the primal so-called reptilian brain, when we are easily startled. Recent research, however, suggests that basic emotions like fear and anger are hardly restricted to any particular region of the brain. As Aalto University doctoral candidate and researcher Heini Saarimäki describes it, “From the biological point of view, an emotion is a state of the entire brain at a given moment.”
Rather than specific regions of the brain being activated when we anxiously await our test results, the emotion we feel is actually the sum total of a number of factors. The doctor’s tone of voice or the way they enter the room, may be interpreted by the brain as ominous or reassuring. As that happens, the brain is also quickly pulling up a number of memories — where you were the last time you received bad news, for example.
You may wonder why painful memories remain so detailed in our minds for years after they happened — why it’s possible to replay them and revisit them so often, while forgetting mundane details from yesterday. We may now know why this has become part of our mental fabric. A recent study identified “anxiety neurons” residing in the hippocampuses of lab mice, using calcium imaging to highlight brain activity. The hippocampus is a part of the brain’s limbic system that plays a role in the formation of memories.
SHINING A LIGHT
To instill feelings of anxiety in the mice, the researchers at the University of California, San Francisco, placed them in an intricate maze. Some of the trails brought them to open spaces, others lifted them onto a different platform forcing them from the safety of the walls. Even though they have no natural enemies, the mice displayed the same feelings of vulnerability to predators, just as their cousins would in the wild. Miniature microscopes placed into their brains highlighted a burst of activity in the ventral CA1 region of the hippocampus, the more agitated the mice became.
The output from these neurons came from the hypothalamus, responsible for regulating the hormones behind emotions. The same regulation process occurs in people too, so the researchers suspect that the same anxiety neurons occur in human biology. The good news is that at least for the mice, there’s a way these neurons can be controlled.
The technique is known as “optogenetics” in which the cells are controlled by a beam of light, shone directly onto the ventral CA1 region. The cells that were activated during periods of high anxiety shut down, and the mice confidently explored their environment once again. Adjusting the light settings further allowed the researchers to reverse this effect. They were able to increase anxiety levels even when the rodents were safely enclosed in familiar surroundings. The team suspects that these neurons may exist in other parts of the brain as well.
“These cells are probably just one part of an extended circuit by which the animal learns about anxiety-related information,” said neuroscientist and lead researcher Mazen Kheirbek, who plans to pursue the study further. Perhaps one day in the future, conditions like post-traumatic stress disorder could become as treatable as turning a light switch on and off.
WHAT ABOUT US?
Another experiment, performed at University of Waterloo in Canada looked at anxiety levels in 80 different students who were categorized as having either high or low anxiety, though all at levels they could manage. They were shown words that flashed across a computer screen, superimposed on random images, and then quizzed on the words they could remember. While the high- and low-anxiety groups seemed to recall similar numbers of words, the researchers noticed that the high-anxiety group was actually better at recalling words superimposed on the more bleak images — pictures of car wrecks or burning buildings, for example.
“Their memories were more emotionally tinted,” says professor of psychology Myra Fernandes, who co-authored the study, “and as a result rendered more memorable.” While anxious people may have an advantage with memory over their less anxious peers, there is a caveat. If you have too much anxiety, your mood can also affect the way you perceive day-to-day events.
Therefore, Fernandes suggests being mindful of the biases you bring to the table when you live your day-to-day life — try to observe what is happening around you if you find yourself looking too far inward. Keeping a journal in which you simply list events that happened throughout your day can help us to look objectively, even helping to remember some of the things we accomplished more smoothly.
The constant fear of predators likely stole sleep from our ancestors — and even though we have moved from the grasslands, the problem of sleep deprivation plagues us today. Nearly one-third of the population is thought to suffer from what the World Health Organization has described as a catastrophic sleep-loss epidemic. Around 31 percent of the American and Canadian population falls into this statistic.
With an eventful workweek, it may seem like second nature to lose a few hours of sleep, but our brains take a toll that we may not realize. The more tired your brain is, the more difficult it is to assess an ordinary situation from a threatening one. You might attribute feeling tired after work to crunching numbers all day, but working longer hours and sleeping fewer hours actually leaves you vulnerable to more negative emotional states.
With sleep deprivation, the connectivity of the amygdala to the ventromedial prefrontal cortex is weakened. The amygdala initiates a fear response but cannot act without the approval of the ventromedial prefrontal cortex. Connectivity between the insula and the amygdala are increased, magnifying the fear response. As basic as it sounds, getting a minimum of seven to eight hours of uninterrupted sleep is crucial — for much more than we realize. Just getting back those few extra hours each week can be the difference that push us to go the extra mile — to chase after the dream job or apartment that we never thought we could get, rather than to just play it safe and keep our deepest fears at bay.
This article was originally published in the Summer 2018 issue of Brain World Magazine.
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