A new paper recently published in the online journal Neuron, reveals that exposure therapy is able to remodel the inhibitory junction found in the amygdala, which is the most important brain region related to fear in humans. Exposure therapy is a technique used to treat anxiety disorders such as specific phobias and PTSD (post-traumatic stress disorder). During exposure therapy, the subject is confronted with a fear or a memory of the traumatic event that led to the anxiety disorder.
The results of the study further improve the understanding of the exposure therapy technique and the processes through which it suppresses fear. The research team is from the School of Medicine, in collaboration with the Sackler School of Graduate Biomedical Sciences, both from Tufts University, in the United States. According to precedent studies, fear is responsible for the activation of a specific group of neurons from the amygdala. Exposure therapy can partially inhibit these neurons, thus subjects experience less fear when given the same situation (to find out on how fear dictates us press here) .
According to the results of the current study, exposure therapy does not only partially inhibit these neurons, but is also responsible for inducing a remodeling effect of the perisomatic synapses. These specific synapses are known as inhibitory junctions, connecting the inhibiting neurons to other neurons in the vicinity. Through exposure therapy, the number of perisomatic synapses increases, thus causing the inhibition of more fear neurons.
Assistant professor Leon Reijmers, the senior author of the study, notes that this effect is a sign of brain remodeling. However, instead of erasing the memory of the fear situation, it suppresses it. Reijmers and his research team investigated this effect by using imaging techniques of neurons that were activated by fear in laboratory mouse models. The inhibitory connections in the mouse brains are similar to the connections in a human’s brain, thus making mice a perfect test subject for these types of studies.
The laboratory mice were put inside a box and researchers created fear-inducing situations in order to stimulate their amygdala. There were 2 groups of mice: a control group and a comparison group. The control group didn’t receive any kind of exposure therapy. The second group, the comparison group, received exposure therapy. In order to alleviate the fear response, the comparison group was placed repeatedly in the box, without exposing them to the fear-inducing situation again. This process is also known as fear extinction.
Investigators discovered that the mice who underwent exposure therapy had an increased number of inhibitory perisomatic synapses. Moreover, the majority of these synapses were located in the vicinity of the fear neurons. First author of the study, professor StÃ©phanie Trouche, notes that these results reveal that the remodeling of the inhibitory perisomatic synapses is closely related to the activity of the fear neurons in the amygdala. Reijmers concludes that exposure therapy is not effective for every human subject. Furthermore, the majority of patients who respond well to exposure therapy still experience fear, as the therapy has incomplete effects. Reijmers suggests that his study could possibly lead to an improvement in exposure therapy, thus making it more efficient for human patients suffering from various anxiety disorders.