Bulletin

Issue: January/February 2006

News

Memory – an unreliable tool for recalling

Whenever we remember something we seem to have an almost unshakeable view that things occurred exactly as we recall them. This is not so, as many studies over the last 20 years have shown.

According to Professor Simon Crowe, Head of La Trobe University’s School of Psychological Science, memory can relatively easily be altered, re-written and we can quite easily be led to believe that things that did not actually happen did take place.

‘Clearly, the mechanism for this process of writing and re-writing memory is an important one and one that deserves study,’ Professor Crowe said.

Professor Crowe has received an ARC Discovery Grant of $160,000 to investigate the biological processing and re-processing of memory. The project title is ‘Remembering that things have changed’.

He said that the issue of memory accuracy has had its most frightening expression in legal and ethical disputes as a result of the debate over recovered memory – memory which has been unearthed a considerable time after the alleged events were thought to have taken place.

‘There have been cases where innocent individuals have been charged and convicted for childhood sexual abuse and satanic cult worship,’ Professor Crowe said.

‘The basis on which the memory process rests is that memory encoding and consolidation is not the same as video or tape recording. We are active players in the encoding of memory, not just in the original processing of the memory but also in what we choose to remember and the way in which we choose to remember it afterwards,’ he said.

Professor Crowe said that memory goes through two processes called consolidation and re-consolidation. ‘Consolidation is the encoding of the original memory of the event at the time that it first happened.

‘Reconsolidation is the process whereby the original memory changes as we recall and re-examine the memory at a later time. Reconsolidation allows the new context in which the memory is recalled to alter and add to the original memory by adding new components which occurred at the time that we reminisce.

‘An example is when family members gather at Christmas and recall past events they shared. Each member inevitably has a different version of the original event because each one makes additions or changes to that event.’

Professor Crowe is building on pioneering research by Professor Kim Ng and Dr Marie Gibbs at La Trobe 30 years ago into the behavioural, pharmacological and biochemical difference between consolidation and re-consolidation in the memory of day old chicks.

Day-old male chicks are used for humane memory testing techniques in which they peck at coloured beads coated with an unpleasant substance and then are required to recall later on whether a similar bead was the same colour as the original.

‘Using Ng’s and Gibbs’ original model, it is possible to identify a series of stages in the biochemical processing of memory which can be revealed by using pharmacological agents by systematically disrupting each of these.

‘Because the stages are relatively discrete and identifiable from each other, it is possible for recall to exist only up to the end of each stage before the amnesia rising from the pharmacological disruption of the next phase sets in. For a long time it has been assumed that memory could be modified and rewritten, but up to now we have not understood how this process might work.

‘We are examining mechanisms by which it is possible to get that memory back again and to specifically manipulate the information that it contains. This gives us an account of how ongoing update and recall may be taking place.

‘In cases of post-traumatic stress disorder in which individuals, subsequent to the event, have a very protracted and unpleasant course of anxiety related phenomena (as with many Vietnam war veterans or witnesses to murders or armed robberies) there is often a possibility of a very practical outcome.

‘In the case of serious trauma like a near death experience, we could possibly revisit that event and rewrite that memory. The implication is that it might be possible for us to be able to change the contingencies associated with a particular memory.

‘It may be possible to manipulate the situation in which that memory took place so that on retrieval the memory would be less horrifying.

‘Associated with each of the experiences is a set of reinforcement contingencies which tell you whether what happened was a good thing (meaning you should do it again) or a bad thing (meaning that you should not). There is a biochemical mechanism which allows you to be able to identify outcomes as good or bad.

‘Generally speaking, good outcomes are associated with a flow of the neurotransmitter dopamine and bad outcomes are associated with the acute stress hormones including adrenaline and noradrenaline.

‘It may be possible for us to revisit the traumatic memory and change the neurotransmitter related contingencies associated with them, thus making the horrific event less horrifying.’

Professor Crowe said that apart from its possible benefit to the treatment of post-traumatic stress disorder, his research would address the fundamental scientific and practical problem of whether re-consolidation was a repetition of consolidation or a distinct process.