In Brief

Researchers provide insight into the chemistry of fear

In experiments involving mice, researchers at MIT's Picower Institute for Learning and Memory and Howard Hughes Medical Institute report that they have identified a chemical pathway that may underlie the persistence of debilitating fear following a traumatic event.

The researchers used genetically engineered mice in which production of a chemical known as Cdk5, produced in the hippocampus, a part of the brain involved in storing memories, can be controlled through the addition of doxycycline (a common antibiotic) in the diet. The mice were placed in a new environment and exposed to mild foot shocks — in other words, subjected to classic Pavlovian fear conditioning — which resulted in a normal "freezing in place" response.