An international team of scientists led by NARSAD Investigator Jin-Hee Han, Ph.D., of the University of Toronto, has succeeded in erasing a fear memory in laboratory mice, according to a report published in the March 13, 2009 issue of the journal Science.
Co-authors of the paper included three other NARSAD Investigators, Paul Frankland, Ph.D., and Sheena A. Josselyn, Ph.D., also of the University of Toronto, and Rachael Neve, Ph.D., of the Massachusetts Institute of Technology; as well as collaborators from Erasmus University, The Netherlands; University of Zurich, Switzerland; Johnannes Gutenberg University, Germany; and the University of Bordeaux.
The authors state: "Memories are thought to be encoded by sparsely distributed groups of neurons. However, identifying the precise neurons supporting a given memory (the memory trace) has been a long-standing challenge."
In previous research, the team showed that a group of brain cells called the lateral amygdala neurons are selectively recruited into the memory trace by increases in levels of a protein called CREB. In the current study, the researchers used a diphtheria-toxin strategy to erase the memory by selectively deleting the neurons that were overexpressing CREB. The memory loss was �robust and persistent,� they report, suggesting that it was permanent.
The study showed that neurons with increased CREB levels at the time of fear learning "are critical to the stability of that memory," write the authors. The results "establish a causal link between a defined subpopulation of neurons and expression of a fear memory and, thereby, identify a key component of the memory trace."
In describing his NARSAD-supported research, Dr. Han has stated that "it is becoming increasingly apparent that the mechanisms underlying fear conditioning in rodents have much in common with human anxiety disorders. Thus a better understanding of how fear memories are acquired, processed and stored will aid in understanding and treating human anxiety disorders."