don't forget to remember ...

Consolidation is the progressive postacquisition stabilization of long-term memory. The term is commonly used to refer to two types of processes: synaptic consolidation, which is accomplished within the first minutes to hours after learning and occurs in all memory systems studied so far; and system consolidation, which takes much longer, and in which memories that are initially dependent upon the hippocampus undergo reorganization and may become hippocampal-independent. The textbook account of consolidation is that for any item in memory, consolidation starts and ends just once. Recently, a heated debate has been revitalized on whether this is indeed the case, or, alternatively, whether memories become labile and must undergo some form of renewed consolidation every time they are activated. This debate focuses attention on fundamental issues concerning the nature of the memory trace, its maturation, persistence, retrievability, and modifiability.

I knew that we revise a memory each time we access it, so that our record is not some kind of holy writ but a palimpsest; but had not realised (though in a way it is obvious) that every time a memory is activated, even a long term memory, it also becomes vulnerable to erasure. Remembering can thus lead to irretrievable forgetting:

Experimenting with rats we reactivated long-term memory and then, using the drug propranolol, blocked protein synthesis in the amygdala - one of the systems crucial for learning and consolidating memories of fearful events - and the rats were no longer afraid ... it was bizarre. It should have been a fixed memory ... the same process has been demonstrated in snails, honey bees, earthworms, crabs and, last year, humans ...

The humans in question were cocaine users and the technique of erasure was designed not so much to eliminate memory of drug-taking per se as it was to neutralise the emotional boost given the memory of a hit when it is recalled. There are clearly all manner of other possible applications for this process (=rediscovered reconsolidation), for instance in the treatment of Post Traumatic Stress Disorder; but, equally obviously, some of these applications have a sinister side.

These and other neuro-ethical issues are being monitored by the Centre for Cognitive Liberty and Ethics, whose Director, Dr Wrye Sententia, predicts a coming boom in the production and consumption of neuroceuticals just like the industry that has grown up around plastic surgery. The genie is already out of the bottle, Dr Sententia allowed.

Guess we'll just have to wait and see what form(s) cosmetic neurology might take; I can think of a few ...

(The first quote is the abstract of a paper entitled The neurobiology of consolidations, or, how stable is the engram? by Y Dudai, published in the Annual Review of Psychology, 2004; the second from Choose to forget Sydney Morning Herald, Health & Science, 3.11.05.)

No comments: