In a recent study, US researchers found a brain-wide correlation between fear and anxiety. This unique research could shed light on the neural response to fear. This link can also be how fear turns into anxiety.
What if we were well on our way to discovering how anxiety arises from fear? An unprecedented study published in the journal NeuroImage on May 28, 2020 lays the first foundations for a satisfactory response. Researchers at the University of New Mexico and the CalTech Institute (United States) carried out experiments on rodents. More specifically, these are behavioral analysis coupled with MRI scans.
According to the results, several areas of the brain stimulated by fear are still active long after the event that generated the same fear! In order to obtain these results, the scientists manipulated serotonin receptors by disabling the SERT gene. Remember that serotonin is a neurotransmitter located in particular in the central nervous system, also known to be the hormone of happiness.
Turning off this gene made mice (SERT-KO) more vulnerable to fear and hence anxiety. However, this allowed a better MRI and behavioral analysis. In addition, the researchers injected them with manganese. In its ionic form, this chemical element helps bring out neurons during MRI sessions.
After that, the mice were left to rest for a few days in order to avoid possible parasitic stress. Then they were confronted with a scent capable of triggering fear. It is the TMT (2,3,5-trimethyl-3-thiazoline) molecule, which comes from the anal glands of the fox.
It should be noted that the researchers performed MRI scans before, during and after the fear experiments. The imaging revealed many areas of high brain activity (45 in total). Also, some of these areas appeared several days after the fear experience. In addition, the researchers found that in SERT-KO mice, the signals did not disappear until 23 days after exposure to the odor. In the case of normal mice, this duration is 9 days.
For the study leaders, there is a difference between brain activity during anxiety and that related to a specific response to fear. Here, the activity involves several specific regions of the brain. Above all, there is a loss of natural coordination between these same regions. These include the striatum (motivation and survival) and the pallidum, connected to the striatum and participating in the basal ganglia system. It should be remembered that a study published in 2018 located the neurological basis of anxiety in the hippocampus.
Finally, an episode of anxiety following a fear experience also affects the brain’s reward circuitry, which is made up of serotonin receptors, among other things. For the leaders of the study, this research could be used to better identify anxiety but also post-traumatic syndromes in humans. It could be a question of more appropriate treatments bringing more effectiveness.