Some traumatic events may lead to the development of severe medical conditions such as anxiety disorders or posttraumatic stress disorder (PTSD).
Despite successful treatments, some patients relapse, and the original symptoms reappear over time (fear of crowds, recurring nightmares, etc.). An understanding of the neuronal structures and mechanisms involved in this spontaneous recovery of traumatic responses is essential.
All observations made by researchers indicate that fear behaviors are controlled in the forebrain at the level of the dorsomedial prefrontal cortex. This control of fear behavior is based on the activation of neurons in the prefrontal cortex that are in contact with specific areas of the amygdala.
Using an innovative approach combining electrophysiological recording techniques, optogenetic manipulations and behavioral approaches, the researchers were able to demonstrate that fear expression is related to the inhibition of highly specific interneurons -- the parvalbumin-expressing prefrontal interneurons.
More specifically, inhibition of their activity disinhibits the activity of the prefrontal projection neurons, and synchronises their action.
Synchronization of the activity of different neuronal networks in the brain is a fundamental process in the transmission of detailed information and the triggering of appropriate behavioral responses. Although this Synchronization had been demonstrated as crucial to sensory, motor and cognitive processes, it had not yet been examined in relation to the circuits involved in controlling emotional behavior.
The identification and better understanding of these neuronal circuits controlling fear behavior should allow the development of new treatment strategies for conditions such as posttraumatic stress disorder and anxiety disorders. "We could, for example, imagine the development of individual markers for these specific neurons, or the use of transmagnetic stimulation approaches to act directly on excitatory or inhibitory cells and reverse the phenomena."
The above story is based on materials provided by INSERM (Institut national de la santé et de la recherche médicale). Note: Materials may be edited for content and length.
- Julien Courtin, Fabrice Chaudun, Robert R. Rozeske, Nikolaos Karalis, Cecilia Gonzalez-Campo, Hélène Wurtz, Azzedine Abdi, Jerome Baufreton, Thomas C. M. Bienvenu, Cyril Herry. Prefrontal parvalbumin interneurons shape neuronal activity to drive fear expression. Nature, 2013; DOI: 10.1038/nature12755
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