You probably wish sometimes that you had a better memory. But imagine being regularly traumatised by thoughts of a road accident, a bereavement or a failed relationship. You might prefer to lose that memory instead of letting it ruin your life. This is the prospect being held out by scientists at the 2,000-strong annual meeting of the Cognitive Neuroscience Society, now being held in New York.
Neuroscientists claim that research may soon make it possible to prevent bad memories from forming, and to control or remove them once they have formed. The fiction of the film Eternal Sunshine of the Spotless Mind, in which Kate Winslet and Jim Carrey fall in love again having had their memories of each other deliberately erased, may soon be reality.
If the scientists in New York, who will be discussing “memory regulation” on Tuesday, are right, many tragedies associated with traumatic events might be avoided. In 1996, for example, a 20-year-old man was convicted of manslaughter in New Zealand, having killed a man who made sexual advances towards him. The victim looked like someone who had abused the young man 13 years earlier, triggering the traumatic memories and causing a violent reaction.
There’s also the potential to cure people of depressive disorders and to destroy addictive behaviour patterns. And, for most people, there may simply be the potential to get rid of useless information cluttering up the brain.
Contrary to expectations, memories are not a simple matter of having them or losing them: scientists are only just beginning to understand how fluid they are. They start as patterns of electrical activity between cells in the brain’s hippocampus. Translating what may be transient thoughts into something more permanent involves structural changes in the connections between cells (synapses). Proteins are laid down in the synapses, in effect, etching a memory circuit. Memories can be re-evoked. If one part of the circuit is stimulated, say by a current event, the whole circuit is activated and the memory brought to mind.
According to Professor Trevor Robbins, the head of the department of experimental psychology at Cambridge University, some commonly used drugs, such as beta-blockers, can block our ability to produce that protein and have been shown to impede memory formation. The antidepressant Triptanol has been shown to stop memories becoming ingrained if taken within a few hours of a traumatic event. Another drug, called Inderal, is being sold online as a supposed post-trauma “forget pill ”.
Michael Anderson, a professor of psychology at the University of Oregon, one of the chairs of the New York symposium, says that it is possible to train the mind to lose bad memories. “A while ago I knocked a plant off the window ledge,” he says. “I instinctively tried to catch it and then stopped myself at the last second because I remembered it was a cactus. I think it is possible to train the mind in the same way; to see a bad memory coming and to push it out of your mind.”
His experiments have shown that the amount of forgetting that people can do rises with practice. “They show that people who have had many traumas are better at suppressing bad memories than people who have not had any.” If people’s skill at shutting out memories grows with experience, it should be possible to train the brain to use the same process without the trauma. There are likely to be therapeutic uses for this work, particularly in depression and post-traumatic stress disorder.
New techniques of brain scanning are already providing vital clues for Anderson’s work to find out exactly what kind of “retraining” is required. They show that a part of the brain called the dorsal lateral prefrontal cortex is associated with controlling memory, which is fascinating to Anderson because it is the same area involved in overriding instinctive physical responses, such as the urge to grab the cactus. This suggests that exposure therapy, in which someone is reminded repeatedly of a memory and learns not to find it traumatic, may be the key. This is supported by work in Canada, where Karim Nader, from McGill University, has demonstrated in animal experiments that memories become unfixed again when the brain is confronted with a similar situation. Afterwards, the memory is laid down again, but possibly modified by the more recent experience. This is why our autobiographical memories constantly reshape as we go through life.
There can be a positive side to this. There is evidence that children who have suffered sexual abuse by strangers cope with the long-term memory less well than people who have had similar experiences from a family member. Anderson suggests that if the perpetrator is present to remind the victim of their trauma, they may be forced to develop ways of coping with it.
If fine-tuned, the applications for such retraining are widespread. Addicts often react strongly to specific cues: the sight of a needle for a heroin-user; a casino for a chronic gambler; a pub for an alcoholic. Anderson believes that it may be possible to train the addict to see the cue but override the response to it.
Professor David Nutt, of Bristol University, says that using memory drugs to cure addiction may work better. “There are drugs that allow stronger and faster memory formation. They were originally used to treat fear of heights but we are using them to help lay down a strong new memory that will overwrite the old one. If it works, the craving for alcohol will be buried beneath new and more positive memories.”
There is probably never going to be a simple delete button for human memory, which is why Anderson says we will always need to stress the importance of coping: “For events such as the death of someone close, methods of coping with the memory are bound to be preferable.”
Details of the annual meeting of the Cognitive Neuroscience Society are at www.cogneurosociety.org
Scratch the head
Can’t get Is This the Way to Amarillo? out of your head? Persistent tunes are prime candidates for memory eradication and American scientists are a step closer, having discovered that they cause a “brain itch” that can be scratched only if the tune is mentally sung.
Researchers from Dartmouth College pinpointed the part of the brain that was most active when volunteers listened to familiar tunes and found that it remained active even after the tune had stopped. It is the words in the song that may be the real problem. The researchers found that songs with lyrics caused more advanced brain activity than instrumentals. “It makes us think that lyrics may be the focus of the memory,” says David Kraemer, from Dartmouth’s brain sciences department.
