Brain, Body, Mind: Get a Grip on Fear


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Erin Eller, science columnist.

Halloween is a celebration of all things scary, but do you understand your own fear? Fear is such an important evolutionary emotion that your brain has its own special pathway dedicated to it.

The fear response begins, of course––with a fear-inducing stimulus––whether this is a big test, a spider or a spooky ghost. A study by Olsson, Nearing and Phelps revealed that most human fears are likely learned socially rather than by direct aversive experience. This means people who are afraid of cats might not have actually had any personal fear-inducing memories involving cats.

Instead humans can acquire fear associations indirectly by witnessing another person’s fear in response to the stimulus. For this reason, you may be afraid of heights without ever experiencing a fall (or near fall) from a high elevation. Further supporting this theory, a 2013 study revealed fear can be inherited from parents or grandparents.

The brain processes this stimulus in a relay station called the thalamus. This structure is the target for most sensory information coming into the brain. From the thalamus, information about the stimulus travels to the cerebral cortex for decision-making and processing as well as to another key structure in your body’s fear response called the amygdala.

Courtesy of Amber Rieder
The amygdala is depicted in red on the MRI scan.

When the amygdala is stimulated, information is sent to several other brain areas which orchestrate physiological and behavioral responses to the aversive stimulus. For example, projections from the thalamus to the hypothalamus activate your body’s sympathetic response, resulting in changes you’ll recognize such as elevated heart rate, blood pressure and respiration rate.

You’re also probably familiar with the tense feeling in your muscles that occurs when you feel threatened by something. This is all part of your body’s “fight-or-flight” response, preparing you physically to react to your fear. The hypothalamus releases hormones into your bloodstream which cause these physiological changes. Other neuronal projections from the amygdala facilitate increased vigilance, stress response and facial expressions of fear.

Many of the things we fear on a regular basis may seem irrational, but in the early days of humanity a distinct fear response was vital to survival. One good example of a common fear which may seem silly or irrational today is the fear of bugs. Bugs carry diseases, many of which are easily cured or vaccinated against now. Many years ago, however, these were life-threatening diseases and so humans evolved an instinctual fear against the bugs which carried them. This is the root cause of many seemingly irrational fear patterns known as phobias.

So if fear produces such undesired effects on our bodies and minds, then why do we love it so much to celebrate it on Halloween? Apart from the candy, it seems that many people enjoy feeling fear in such a controlled setting. The sympathetic response evoked by your hypothalamus produces a thrilling adrenaline rush. The excitement of sensory stimulation may also explain why some people enjoy horror movies so much, despite being scared.

The views reflected in this column do not necessarily represent the views of The Review.

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