Inducing a safety memory in the brain

Researchers at the University of Puerto Rico, School of Medicine have found a way to pharmacologically induce a memory of safety in the brain of rats. As reported in the June, 4 2010 issue of Science, administering brain-derived neurotrophic factor BDNF into the prefrontal cortex prevented rats from expressing fear to a tone that had been previously paired with a shock.

... Could naturally occurring variations in brain BDNF levels explain why some individuals extinguish better than others? To address this, the researchers measured BDNF protein in rats that showed successful vs. failed extinction. Failed extinction was associated with deficient BDNF in the hippocampus, a structure that projects to ILC and is important for extinction. They further showed that augmenting BDNF in the hippocampal-ILC pathway was sufficient to induce extinction. This suggests that BDNF infused into ILC mimics the BDNF normally released from the hippocampus during extinction, serving to strengthen synaptic connection within ILC during extinction.Failure to extinguish fear is thought to contribute to anxiety disorders, such as post-traumatic stress disorder PTSD. People with PTSD have a smaller than normal hippocampus and ILC. "Our finding suggests that augmenting BDNF in these circuits may ameliorate PTSD and perhaps other disorders such as addictions" said Dr. Jamie Peters, the post-doctoral researcher who collaborated with Quirk on this project. The focus now is to look for ways to augment BDNF's actions in the brain, which might include anti-depressant medications and even exercise. Dr. Thomas Insel, Director of the National Institute of Mental Health, which funds Quirk and Peter's research said, "This work supports the idea that medications could be developed to augment the effects of BDNF, providing opportunities for pharmaceutical treatment of post-traumatic stress disorder and other anxiety disorders."

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