March 22, 2007

The Consolidation of Reconsolidation

Eupatorus gracilicornis.jpgWhen I began my neuroscience research memory consolidation (both molecular and network) was the hot thing: the chemistry, neuropsychiatry and theories were lining up, all that was lacking was mid-level evidence to demonstrate actual consolidation from the hippocampus to cortex, as well as better neural network models of how it was done. By now it looks like most of this has been achieved (although I still think our neural network models of hippocampus-cortex transfer are a bit weak).

Fortunately we got reconsolidation to complicate matters. This phenomen has rapidly gone from a fringe claim to the new hottest topic. See "Rites of Passage of the Engram: Review Reconsolidation and the Lingering Consolidation Hypothesis" by Yadin Dudai and Mark Eisenberg for a review of current models.

That memories can become fluid again poses many interesting issues for how overall memory plasticity works. The original impetus for the network consolidation models was to deal with the problem of overwriting information: we needed a slow learning cortex for long storage and a fast learning hippocampus to portion out the information. But reconsolidation, together with modulation of plasticity from subcortical sources makes the cortex a far more dynamical place. How does these processes produce a fairly stable engram, without accidentally overwriting it? Beats me. But there seem to be some complexity in when reconsolidation can occur, and maybe different kinds of memory and memory ages affect the process. That would imply a much closer link between the network behavior of entire memories and the molecular behavior of how synapses change. Previously the assumption was (at least in my mind) that there was an abstraction level between them, but maybe the brain is messier than we expected.

There are also possible applications such as the one I mentioned on this week's CNE blog, selective memory erasure. Together with consolidation enhancers and drugs that affect consolidation byt not reconsolidation or vice versa suggests a lot of interesting potential for memory editing. And that will of course keep neuroethicists and psychologists busy for a long time.

Posted by Anders3 at March 22, 2007 01:29 PM