Science: Researchers Over-Write the Fearful Memories of Rats

Recent success in training rats to overcome their fears may someday be combined with current therapeutic practices to help humans conquer theirs as well, researchers say. This experimental approach is a significant advance in the sense that no drugs or invasive procedures are needed to overcome these fearful associations.

Damage done to the mind's "fear system" is at the core of many psychiatric disorders, and understanding how we store fearful memories and respond to them could shed light on more advanced therapies. While researchers have also had success with over-writing fearful associations in human subjects, it has traditionally been accomplished with strong drugs or invasive surgeries.

The new research suggesting that we may be able to conquer our fears without drugs is published in the 3 April 2009 issue of the journal Science.

Dr. Marie Monfils of the Center for Neural Science at New York University and the Department of Psychology at the University of Texas, along with colleagues from New York University, the Nathan Kline Institute, and the Emotional Brain Institute, performed a series of experiments with rats.

The researchers found that by applying a standard "extinction" treatment soon after the rats recalled fearful memories, they could effectively over-write the original memory that inspired the fear. This extinction treatment, which is sometimes used on humans, involves the repeated presentation of a fear stimulus, but in a safe setting without anything to actually fear and without any negative consequences.

They began their experiments by inducing fear in rats by sounding a tone and administering a subsequent electric shock. Afterwards, they noticed that, while the fearful association of tone and shock was still fresh in the rats' minds, administering a long series of tones without the shocks could effectively destabilize the rats' fearful association of the two and replace it with an apparently benign memory of the event.

Monfils and her colleagues observed that rats treated with this technique showed lower levels of fear induced by the sound itself, lower levels of fear induced by the shock itself, and also smaller chances that the original fear memory would spontaneously resurface. In their report, the authors note, "These results could suggest either that the initial memory has been reversed" or that the power of the fear stimulus has been "permanently re-valued, and re-encoded as safe."

This means that the technique seems to over-write the fear memories permanently, and without the use of pharmacology. Someday in the future, it might be applied to humans as well to treat psychiatric disorders and to conquer our own fearful associations, the researchers say.

Brandon Bryn

3 April 2009