London, April 13 : Researchers at the University of California have found that low doses of a commonly used anaesthetic drug could prevent the formation of painful memories.
The researchers found that sevoflurane gas stopped patients remembering 'emotive' images.
They are hoping that the new finding could eventually help eradicate rare instances of anaesthetised patients remembering the full horrors of their surgery.
Anaesthetic drugs are mostly used to make patients fall unconscious before operations, but their effects on the body are frequently far more complex.
The researchers set out to determine the effect of much lower doses of the gas than those used prior to surgery.
They treated study participants either with the anaesthetic, or a placebo gas, and exposed them to a series of pictures.
While some of these had everyday content, such as a cup of coffee, others had images designed to provoke a far more powerful emotional response, such as a bloody severed human hand.
After one week, researchers asked participants to recall as many of the images as they could.
Participants who received dummy gas remembered approximately 29 percent of the powerful images, and 12 percent of the others.
However, participants who were given sevoflurane gas could remember just 5 percent of the 'emotive' images and 10 percent of the others.
When researchers scanned their brains, they found that the gas appeared to interfere with impulses between the amygdala and hippocampus, areas of the brain nown for their involvement in the processing of emotion and memory.
"This study reports the discovery of an agent and method for blocking human emotional memory," BBC quoted the researchers, as saying.
They further said that understanding how drugs could stop this happening might provide clues to 'intraoperative awareness' - rare instances in which the memory-disrupting qualities of anaesthetic drugs fail and patients can recall the experience of undergoing surgery.
While the study suggested that the gas could prevent the acquisition of new memories following painful events, it does not point to any effect on pre-existing memories, good or bad.
The study is published in the journal Proceedings of the National Academy of Sciences.