MIT IDs mechanism behind fear( encing the fear associated with a speci...)

Treating these disorders involves methods geared toward making the behavior go away, or become extinct, but the molecular mechanisms underlying the extinction process are not well understood. However, Tsai said, studies have shown that some of the molecular machinery that initially encodes the troubling memories also regulates their extinction.

In the current work, genetically engineered mice received mild foot shocks in a certain environment and were re-exposed to the same environment without the foot shock. Mice with increased levels of Cdk5 activity had more trouble letting go--or extinguishing--the memory of the foot shock and continued to freeze in fear. Conversely, in mice whose Cdk5 activity was inhibited, the bad memory of the shocks disappeared when the mice learned that they no longer needed to fear the environment where the foot shocks had once occurred.

"In our study, we employ mice to show that extinction of learned fear depends on counteracting components of a molecular pathway involving the protein kinase Cdk5," said Tsai, a Howard Hughes Medical Institute investigator. "We found that Cdk5 activity prevents extinction, at least in part by negatively affecting the activity of another key kinase.

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Contact: Elizabeth Thomson
thomson@mit.edu
617-258-5402
Massachusetts Institute of Technology
15-Jul-2007