La Razon / People with anxiety disorders such as posttraumatic stress disorder (PTSD) often experience a prolonged and exaggerated fear. Now, an animal study suggests that this could involve the disruption of a gradual change in brain circuits to recover memories of fear. Researchers funded by the National Institutes of Health (NIH, for its acronym in English) Americans have found in rats that an old fear memory returns through a different brain pathway that originally used to remember when recent.
After rats conditioned to fear a tone associated with a mild concussion, the behavior expressed remained unchanged over time, but the way that recalls the traumatic event was diverted, perhaps increasing its staying power. “While our memories are constant over time, the neural pathways that support actually change over time,” says Gregory Quirk, School of Medicine, University of Puerto Rico, San Juan, who informs their findings in a paper published Monday in Nature.
“Discovering new ways to old memories could change the view of scientists about the disorder, post-traumatic stress disorder, in which the terrible events months or years before symptoms appear happen, “adds the expert, who researches supported by the National Institute for Mental Health (NIMH, for its acronym in English) of the NIH. Immediately after fear conditioning in rats, a circuit that runs from the prefrontal cortex, the executive center, part of the amygdala, the fear center, was dedicated to recover memories. However, after several days, the authors found that the recovery had migrated to a circuit different from the prefrontal cortex to an area in the thalamus, called periventricular region (PVT) which, in turn, communicates with a central part different from the amygdala orchestrating learning and expression of fear.
The team Quirk and his colleague Fabricio Do-Monte saw the movimento of memories using a genetic technique called optogenetics, which can activate or silencing pathways separately from specific operation. Researchers say the PVT can be used to integrate the fear with other adaptive responses such as stress, thereby strengthening the fear memory. “In people with anxiety disorders, any alteration of the time-dependent control circuits recovery could worsen fear responses that occur long after a traumatic event,” Quirk suigere.
the same issue of the journal Nature, researchers from the ‘Cold Spring Harbor Laboratory’, in New York, Bo Li and Mario Penzo, also with funding from NIMH, and colleagues reveal how they function in mice circuits fear memory long term translate the detection of stress in adaptive behaviors. Li and colleagues independently discovered the same change in the recovery circuit memory that occurs over time, after fear conditioning in mice. Using a powerful methods for experimentally change channels on and off, showed conclusively that the originating neurons PVT regulate the processing of fear to act on a class of neurons have fear memories in the central region of the amygdala.
Li’s team drew this activity in the PVT in the action of a chemical messenger in the brain-derived neurotrophic factor (BDNF, for its acronym in English), which has previously been implicated in disorders of state mood and anxiety disorders. For example, altered expression of BDNF has been linked to PTSD. The BDNF of PVT, working through a specific receptor, activated neurons in the amygdala stock memories. Simply, infusion of BDNF in the central area of the amygdala caused mice were paralyzed by fear, suggesting that not only allows the formation of fear memories, but also the expression of fear responses.
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