Brain: what happens when we are afraid?

Racing heart, tremors or dizziness, sweating, difficulty concentrating… The physical symptoms of fear are well known. But until now, what happens in our brains when we are frightened has remained largely unknown. Indeed, the mechanisms involved lie deep in the brain, where it is difficult to obtain brain wave readings. Thanks to a Chinese and German team of researchers, the mystery is about to be lifted. In a study published in Science Advancesthey detail the results of their experiments, conducted with epileptic patients whom they equipped with brain probes before subjecting them to a fear learning task.

Activity concentrated in the amygdala and medial prefrontal cortex

Previous work had already suggested that in the brain, fear originates in the amygdala and in the medial prefrontal cortex (MPC), which this new study confirms. To learn more about what’s going on in these brain regions, the researchers showed the volunteers a square on a computer screen. At random times, a shock to the wrist accompanied the display of a colored square, teaching the volunteer to fear this square. The same volunteers then looked at the square again after their probes were in place.

The study authors were then able to see an increase in brain activity when a volunteer saw a square that they associated with a shock to the wrist – a measure of the fear response. This brain activity is a type of rhythm called the theta wave, which occurred in both the amygdala and the MPC.

The researchers also noticed that this fear response originated in the dorsal CPM, as had already been studied in primates. This work could lead to the development of therapies to treat anxiety disorders, scientists now hope.