When fear strikes, you may feel your hair stand on end, your stomach churn, and your heart race… Recently, scientists have discovered a “switch” for fear in the brain and how to turn it off.
Fear can be terrifying; strangely enough, it can also be exhilarating, such as when you are exploring an abandoned house.
Fear: Both Beneficial and Troublesome
Essentially, fear is a useful emotion. However, at times, fear can cause considerable trouble – (Photo: Shutterstock).
Essentially, fear is an incredibly useful emotion. It is an instinctive response to danger that enhances your chances of survival when situations worsen. However, there are times when fear can lead to significant inconveniences.
In cases like anxiety disorders and stress disorders, the fear response can become inappropriate to your circumstances or environment, severely hindering mental health and quality of life.
To gain a deeper understanding of fear and how this emotion operates, a research team led by neuroscientist Hui-Quan Li from the University of California, San Diego (UC San Diego) mapped changes in brain chemistry and neural signals in mice that experienced extreme fear. The study even found ways to prevent fear.
The research was conducted on genetically modified mice that expressed a specific transporter of glutamate, an important neurotransmitter in the brain (an excitatory neurotransmitter), as well as fluorescent proteins in their brain cells, allowing for monitoring of changes in the brain.
The mice were subjected to electric shocks at two different levels of severity under specific conditions. When returning to that environment two weeks later, they tended to freeze in fear.
Those who experienced severe shocks also tended to “freeze up” similarly to the mice, in a different environment, indicating a generalized overreaction. Observing inside the brain revealed what fueled this excessive fear response.
Specifically, researchers examined a brain region called the dorsal raphe, located in the brainstem of mammals. This brain area is responsible for regulating mood and anxiety and provides a significant amount of serotonin to the brain. Importantly, the dorsal raphe also plays a crucial role in fear learning.
In cases like anxiety disorders and stress disorders, the fear response can become inappropriate to your circumstances or environment – Photo: Simply Psychology
How to “Turn Off” Fear?
The research team discovered that a severe feeling of fear activated a “switch” in the neurons, altering the neurotransmission mechanism from glutamate—the excitatory neurotransmitter—to GABA—the inhibitory neurotransmitter.
This “switch” appears to continue maintaining the fear response when it should have turned off or diminished, resulting in symptoms consistent with generalized anxiety or fear disorders.
A study of the brains of deceased individuals who suffered from PTSD (Post-Traumatic Stress Disorder) during their lives showed a similar conversion from glutamate to GABA neurotransmission.
This finding is a starting point for discovering ways to prevent the fear response. One method involves injecting mice with an adenovirus to inhibit the gene responsible for producing GABA.
When researchers trained these mice with a fear-inducing stimulus, they did not develop the signs of generalized fear disorder as seen in untreated mice. This preventive method requires prior knowledge of certain stressors that may lead to the disorder.
However, researchers have found a method to mitigate the impact of fear after an event. If treated with the conventional antidepressant fluoxetine immediately after experiencing fear, the neurotransmitter conversion and subsequent generalized fear will be prevented.
But this treatment must occur immediately. Using medication after the neurotransmitter conversion has taken place and the fear response has become evident is too late. Researchers suggest this might explain why antidepressants are often ineffective in patients with PTSD.
These findings are not yet considered a cure but represent a promising beginning toward effective treatment.
“We have grasped the core mechanism of fear induced by stress and the circuitry that executes this fear. Consequently, interventions can be more targeted and specific,” says Nicholas Spitzer, a neuroscientist from UC San Diego.
The research was published in the journal Science.
