In a recent study, US researchers highlighted a brain-level correlation between fear and anxiety. This unique research could shed light on the neural response to fear. It can also be about how fear turns into anxiety.
What if we were on the way to discovering how anxiety arises from fear? An unprecedented study published in the journal NeuroImage May 28, 2020 lays the first foundations for a satisfactory response. Researchers from the University of New Mexico and the CalTech Institute (USA) conducted experiments on rodents. It is more precisely about behavioral analyzes coupled with MRI scans.
According to the results, several regions of the brain stimulated by fear are still active long after the event that generated this same fear! In order to obtain these results, the scientists manipulated serotonin receptors by deactivating 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.
Disabling this gene made (SERT-KO) mice more vulnerable to fear and therefore 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 makes it possible to bring out neurons during MRI sessions.
After that, the mice were left to rest for a few days to avoid possible parasitic stress. Then, they were confronted with a perfume capable of triggering fear . It is the molecule TMT (2,3,5-trimethyl-3-thiazoline), from the anal glands of the fox.
You should know that the researchers performed MRI scans before, during and after the fear experiments. Imaging revealed many areas of high brain activity (45 in total). Moreover, some of these areas appeared several days after the fear experience. Additionally, the researchers found that in SERT-KO mice, the signals only disappeared after 23 days following 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 relating to a precise response to fear. Here, the activity concerns 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. Note in passing that a study published in 2018 located the neurological basis of anxiety in the hippocampus.
Finally, an episode of anxiety following an experience fear also affects the reward circuit of the brain, composed among other things of serotonin receptors. 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 efficiency.
