Most of us would agree that when we experience an emotion, there is often a change in our body. We might be aware of our heart beating very fast when watching a scary film, or notice breathing heavily after a big argument.
As far back as the 1880s, it was theorised that physical changes in the body - such as a racing heart beat - would be sufficient to trigger an emotional experience. Though over the past 150 years, this has been hotly debated.
Now a new study, published in Nature, provides fresh insight.
The researchers used a nonsurgical pacemaker to precisely raise the heart rate of mice and measured behaviour that may indicate anxiety. This included how willing mice were to explore parts of a maze and how they searched for water.
They found that raising the heart rates of mice led to more anxiety-related behaviour, but only in “risky environments”. For example, when there was risk of a mild shock, mice with elevated heart rates showed more caution in their search for water.
These findings are in keeping with the “two-factor theory” of emotion and evidence from human studies. This theory states that while physical changes play a role in emotional experience, the context is important too. Increasing the mouse’s heart rate was not enough to cause anxiety. However, in a “risky environment” where they may expect to become anxious, increasing the heart rate triggered anxious behaviour.
We can see this if we think about how we interpret changes in our bodies in different situations. A sudden increase in your heart rate when you are dancing with friends doesn’t cause much concern. However, when walking home alone in the dark, a similar spike in heart rate might be interpreted as anxiety.
To get a better understanding of these effects, the researchers scanned the mice’s brains during the experiment. They found that an area of the brain associated with perceiving and interpreting bodily signals, the posterior insula cortex, was involved. When they inhibited this brain area, an increase in heart rate did not result in as much anxious behaviour.
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