How a flash of light can delete bad memories: Breakthrough may help dementia patients

Doctors may be able to switch a memory off - and then restore it again

Stimulating nerves with lasers can delete a specific memory

Research could also help boost memories in dementia patients



Erasing memories has long been the stuff of science-fiction movies.

But according to scientists, doctors may soon be able to switch a memory off at the press of a button – and restore it again just as easily.

The discovery, which has been shown to work in rats, may have huge potential for curing phobia sufferers of their fears, helping soldiers to recover from the horrors of battle or allow accident victims to put their trauma behind them. It might also be used for boosting memories in dementia patients.

Like the neuralyzer used by Will Smith and Tommy Lee Jones in the movie Men in Black, the experimental technique works with a flash of light.

Researchers from the University of California in San Diego found that stimulating nerves in the brain with optical lasers could delete a specific memory.

Researchers found that stimulating nerves in the brain with optical lasers could delete a specific memory. File picture

The research team worked on the theory that memories are formed, retained and recalled when the brain makes connections between nerves.

Through their experiments they demonstrated that strengthening or weakening the connections – called synapses – can remove or re-establish the memory.

Roberto Malinow, professor of neurosciences, said: ‘We can form a memory, erase that memory and we can reactivate it, at will, by applying a stimulus that selectively strengthens or weakens synaptic connections.’

The study, published in the journal Nature, used rats to prove the theory. The team used optical lasers at specific frequencies to stimulate a group of nerves in the brains of rats that had been genetically modified to make them sensitive to light.

The damaging products that build up in the brains of Alzheimer¿s disease patients can weaken synapses. This research could suggest ways to intervene in the process. File picture

While shining the laser, they simultaneously delivered an electrical shock to the animal’s foot.

The rats soon learned to associate the optical nerve stimulation with pain and displayed fear when the nerves were stimulated.

The scientists then used a series of low-frequency optical lasers to stimulate the same nerves in a different way, erasing the memories.

They found that the rats no longer responded to the original nerve stimulation with fear, suggesting the pain-association memory had been erased.

But in the study’s most startlingly discovery, the scientists found they could re-activate the lost memory by re-stimulating the nerves with a high-frequency blast.

The ‘reconditioned’ rats once again responded to the original stimulation with fear, even though they had not had their feet re-shocked.

Researcher Dr Sadegh Nabavi said: ‘We can cause an animal to have fear and then not have fear and then to have fear again by stimulating the nerves at frequencies that strengthen or weaken the synapses.’

Professor Malinow added: ‘We have shown that the damaging products that build up in the brains of Alzheimer’s disease patients can weaken synapses in the same way that we weakened synapses to remove a memory.

‘This research could suggest ways to intervene in the process.’

Thomas Insel, director the US National Institute of Mental Health, said: ‘This improved understanding of how memory works may hold clues to taking control of runaway emotional memories in mental illnesses, such as post-traumatic stress disorder.’

Last week, researchers in Virginia said mice given a pill containing fingolimod, a drug used to treat multiple sclerosis, forgot about painful experiences.