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The neuronal circuits of fear

A study in rats

Thanks to the results obtained, the researchers hope to obtain valuable information for treating anxiety disorders, and which ones in particular related to post-traumatic stress

Fear is fundamental emotion in animals as in humans. Now a team of neuroscientists has localized to the neurons responsible for the first time due to fear conditioning in mammals.

due to the fear conditioning is a form of Pavlovian learning, or partnership, and is considered a model system for the understanding of phobias, post traumatic stress disorder and other anxiety disorders.

Using a technique imaging that displays the neuronal activation in rats, researchers at the University of Washington have identified in the basolateral nucleus of the amygdala, the region where it is encoded due to fear conditioning.

previous studies had already led to suspect that the amygdala and other brain regions, such as the dorsal hippocampus, were associated with the formation of memories of fearful events.

"This new work suggests that the role of the hippocampus and amygdala to process and transmit the information of the conditioned stimulus," said Ilene Bernstein, professor of psychology UW and co-author of the article appeared on open access journal " PLoS One" .

The conditioning is the basic form of associative learning in the animal kingdom and is regularly used in the study of brain circuitry changes they are undergoing as a result of experience.

In this case, the trial was aimed at the search site that converge in the brain information about the conditioned stimulus and unconditioned stimulus during the establishment of fear memories. The researchers used four groups of rats and have placed them individually for 30 minutes in a room that had never seen before.

Rats in the control group proceeded to explore the room, then became less active and some of them finally fell asleep. The group of "delayed shock" explored the room, decreased activity, but received a shock after 26 minutes. The third group of rats were left alone to get familiar with the room in 10 subsequent visits, and then also received the shock. The final group instead received an electric shock immediately after being introduced into the chamber.

In the following days, the rats were put back one by one in room, where they showed the characteristic behavior of immobilization, the result of fear. More intensive forms of immobilization were observed in those animals that received a delayed shock without having familiarized with the environment.

Only in the group of delayed shock were found converging evidence of activation of the conditioned stimulus (the room) and the unconditioned (shock). The experiment has thus shown that animals can acquire fear in the long term when a new context is paired with a shock administered 26 minutes after, but not when the shock is associated with a family setting.

"The fear and dislike of taste are both examples of associative learning, in which two experiences are acquired together. Often, learning is very fast, since it is critical to survival: it allows to avoid dangerous places or toxic foods, "explained Bernstein. "People often have phobias that are caused by stimuli that come from something that happened to them, like being scared by a snake or be in a dark room. In this way develop an anxiety disorder."

"With these results we can obtain valuable information to treat anxiety disorders, by doing so reduce or eliminate air conditioning: it is also a tool for understanding what happens in brain cells and the mechanism underlying the conditioning due to fear. "( fc )

taken from http://lescienze.espresso.repubblica.it/articolo/titolo/1339183