Erasing memories

IT was a simple oversight that nearly killed Robyn Langford 3 1/2 years ago. She'd forgotten to put the handbrake on in her car when she went to check the mail.

In an instant the unoccupied car ploughed her down from behind, causing massive blood loss and crushing her body. The physical injuries were extensive but at times it was the psychological damage that was most difficult to deal with.

"Initially I was so all-consumed with physically getting better that I didn't really focus on the mental side of things, but as the physical side improved I realised I was having difficulty coping mentally," she says.

Thankfully, help was available. Further, scientists are learning more and more about the neurobiological workings of the brain. Soon, even more effective treatments will be available for tackling horrific memories such as those that traumatised Langford.

She found terrible memories of the accident could intrude at any time or place. Nightmares were frequent. She couldn't sleep at night and couldn't concentrate when she was awake.

Flashback triggers were everywhere: in a meeting, watching television. Even seemingly unrelated things such a gust of wind on her face when driving with the window down would trigger memories. The sensation reminded her of a distressing hospital procedure in which medical staff had placed a suction cup over her face to force air into her lungs.

About six months after the accident Langford saw Mark Creamer, a professor of psychology and director of the Australian Centre for Post-traumatic Mental Health, a research centre at the University of Melbourne.

It was Creamer who diagnosed Langford with post-traumatic stress disorder and took her through a series of intensive treatment sessions he describes as "imaginal exposure". In other words, he helped her confront the painful memories as well as activities and situations that she was avoiding as too distressing. Significantly, this treatment gave her tools to cope, to move on, and to regain her life after the accident.

Creamer says patients today are faring much better than in years past. "Treatment has come a long way in the last decade or so. We now have a strong body of research evidence to guide our interventions and around four out of five patients show substantial improvement with interventions such as imaginal exposure therapy," he says.

But that still leaves 20 per cent of patients who don't respond to present treatments, and even for those who do make vast improvements, the symptoms don't disappear entirely. "I still experience nightmares and flashbacks, but not to the extent that I did before, and they don't distress me to the level that they did . . . Now I have a mechanism to cope, but it's still always in the back of my mind," Langford says.

The emerging understanding of the process by which memories are stored and retrieved could help Langford and others put the memories away forever.

In a study published in Nature earlier this month, researchers at New York University conducted a simple experiment that used the basic principles of the tried-and-true imaginative exposure therapy, also known as extinction, to erase simple fear memories rather than merely suppress them.

The researchers intermittently paired coloured squares with mild wrist shocks so participants learned to fear the square alone. A day later all participants received extinction training, in which they were re-exposed to the squares without the accompanying shocks, but the timing of the training differed. A third received the training soon after the memory was reactivated, another third were given the training about six hours later and the remaining third received the training without having the fear memory reactivated. Only the participants who received the training soon after the fear memory was reactivated didn't experience any fear response when they were exposed again, even a full year afterwards.

It's a finding even the study's authors concede is confusing.

Scientists believe that whenever a memory is reactivated there's a period of time when it's fragile and can be changed. In other words, the details of a memory can be changed even long after the initial incident occurred.

"Normally what happens is that extinction training creates a new `safe' memory, but you still have the old `fear' memory and those two memories compete for expression. The more stressed you get, the more likely it is that the original `fear' memory will resurface. The inhibition of fear memories requires a region of the brain that is [affected] by stress hormones, so as those hormones increase it becomes harder to inhibit the original `fear' memory," says the study's lead researcher Elizabeth Phelps.

The idea behind the research is that if you time the training right you can rewrite the original fear memory rather than creating a separate competing memory.

"Because the emotional part of a memory and the factual part of a memory are stored in different parts of the brain, it could be possible to take away the emotional impact without erasing the knowledge of the event," Phelps says.

However, she warns it's too early to say what, if any, implications this sort of preliminary research may have for patients with anxiety disorders. "We're trying to understand the biological process so that we can manipulate it, but it's a big step from here to see if we can apply it to complex memories that may contribute to anxiety disorders. We don't yet know how this is going to extend into clinical practice," Phelps says.

That's a point Creamer takes great pains to make. He says it's a massive leap to go from a laboratory experiment to a real-world application. Also, the study would need to be replicated in a population with a disorder such as a phobia. Then a proper randomised control trial would be needed to convince mental health professionals that changes to treatment were justified.

"I'm urging loads and loads of caution . . . there's no understanding of exactly how this would translate to a treatment in the real world," he says.

Meanwhile, Australian researchers, including those at Creamer's centre, are working to improve outcomes for PTSD patients in other ways.

One approach is to identify patients at high risk for developing PTSD, and target them for early intervention.

Preliminary results of a trial at two Melbourne hospitals found that when at-risk patients sought help early they fared significantly better than with usual care, says Meaghan O'Donnell, the centre's director of research. Injury patients at the two hospitals were screened for known risk factors of PTSD shortly after their accident and then followed up a month later to see how they were coping. Those at high risk and showing symptoms of anxiety and depression were then offered access to early therapy, but more than half the high-risk patients declined the early treatment.

"Most people who go through trauma will show symptoms of sadness and anxiety. That's a normal response that everyone goes through and most people do recover. So the idea of sending out counsellors to everyone is not very useful since only a small number of patients will actually go on to develop PTSD," O'Donnell says.

However, there are several known risk factors that can be screened for, such as lack of strong social networks or history of psychological problems.

High-risk patients who declined early treatment did so for a variety of reasons. Some thought they could handle it on their own, or didn't think they could commit to so many sessions or justify the time and effort of the therapy. Some declined because they were receiving treatment already, but follow-ups of those patients showed they were still not doing well.

"Evidence-based treatments such as cognitive behaviour therapy work very well as an early intervention but we need to address the barriers to care and make sure patients are getting evidence-based treatment," O'Donnell says.While earlier treatment may be preferable, it's never too late to seek help. Treatment can be effective even years after the traumatic event.

To that end, experts such as Creamer and O'Donnell stress that while there's always room for improvement, many patients are making significant headway with existing treatments.

Langford can testify to that. It's been a tough road but now she's back at work and finally feels able to move on: "I have my life back."