How anxiety disorders treatment helps overcome fear

During exposure therapy, an effective and common treatment for anxiety disorders, the patient confronts a fear or memory of a traumatic event in a safe environment that leads to a gradual loss of fear.

A new study in mice, published online today in Neuron, reports that exposure therapy remodels an inhibitory junction in the amygdala, a brain region important for fear in mice and humans.

The study, led by researchers at Tufts University School of Medicine and the Sackler School of Graduate Biomedical Sciences at Tufts found that exposure therapy not only silences fear neurons but also induces remodeling of a specific type of inhibitory junction, called the perisomatic synapse.

Senior author Leon Reijmers, Ph.D., assistant professor of neuroscience at Tufts University School of Medicine and member of the neuroscience program faculty at the Sackler School of Graduate Biomedical Sciences at Tufts, said that the increase in number of perisomatic inhibitory synapses is a form of remodeling in the brain. Interestingly, this form of remodeling does not seem to erase the memory of the fear-inducing event, but suppresses it.

Reijmers and his team discovered the increase in perisomatic inhibitory synapses by imaging neurons activated by fear in genetically manipulated mice.

Mice were placed in a box and experienced a fear-inducing situation to create a fear response to the box. One group of mice, the control group, did not receive exposure therapy.

Another group of mice, the comparison group, received exposure therapy to alleviate the fear response.

For exposure therapy, the comparison group was repeatedly placed in the box without experiencing the fear-inducing situation, which led to a decreased fear response in these mice. This is also referred to as fear extinction.

The researchers found that mice subjected to exposure therapy had more perisomatic inhibitory synapses in the amygdala than mice who did not receive exposure therapy. Interestingly, this increase was found around fear neurons that became silent after exposure therapy.

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