Anaesthetics 'block bad memories'

Anaesthetics could be used to block the formation of harrowing memories, research has revealed.

Many people fantasise about wiping painful experiences from their minds.

And scientists have found that anaesthetic drugs can block the formation of memories associated with emotive images, the New Scientist reports in this week's edition.

Understanding how the process works could lead to a therapy for flushing out distressing memories before post-traumatic stress disorder sets in.

Dr Michael Alkire and Dr Larry Cahill at the University of California say low doses of anaesthetic can impede memory while leaving patients conscious. "One popular misconception about anaesthesia is that unconsciousness occurs immediately," Dr Alkire says.

Volunteers were treated either with a placebo or with a low dose of sevoflurane gas - 10% the amount needed to induce unconsciousness. They were then shown a series of 36 photos, ranging from a coffee cup to a bloody severed hand.

A week later the volunteers were asked to recall as many images as they could. Those given the placebo remembered 29% of the most emotive images and 12% of the banal ones, while those treated with the anaesthetic recalled 5% of the distressing images and 10% of the banal ones.

Brain scans have shown that the anaesthetic interferes with the communication between the regions of the brain which control emotion and long-term memory.

In the film Eternal Sunshine of the Spotless Mind, Jim Carrey and Kate Winslet use a fictional non-surgical procedure to erase painful memories of their relationship.

But the scientists say manipulating pre-existing memories is difficult. One idea is to remind the patient of the memory, taking it out of storage so that it becomes easier to manipulate, says Joseph LeDoux at New York University.

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