Memories are made of this da-da da-da-da-da

The Xmas edition of The Economist has a survey of neuroscience. It is a useful overview which gets you to the frontiers of the area quickly. I was particularly taken by the discussion of memory. Like many (of my vintage) I worry about the strength of my own memory.

The part of the brain that is concerned with memory is the hippocampus. With Alzheimer's disease, the hippocampus is one of the first regions of the brain to suffer damage - memory problems and disorientation are among the first symptoms.

But my currently imprecise memory (of names? faces?) might best be viewed as an adaptation to my vast knowledge rather than an age-induced defect. To start off, understand that there are two types of memory - autobiographical memory which provides a record of particular past episodes and semantic memory which generalises from these experiences. While autobiographical memory is stored in the hippocampus, semantic memory is consolidated in the cerebral cortex - that foldy-foldy piece of 'grey matter' that regulates thinking.

Dr Matthew Wilson of the Picower Institute for Memory and Learning argues that as people age memory becomes more semantic and less autobiographical. Thus old guys, like me, are notorious for being able to remember every detail of our childhoods but often forget what they did last week. This inability to remember detail is often seen as a failure whereas eidetic (or photographic) memory - of the type enjoyed by Wolfgand Amadeus Mozart or John von Neuman - is regarded as an ideal.

But Dr Wilson thinks this might all be wrong. An ideal memory would be able to generalise from experience without recalling specific events. My vast experience means that I do not need to add extra episodic junk to my valuable and limited information storage levels to improve my survival prospects. If I don't remember the specifics of your name or face please be aware that this is a sign of evolutionary adaptation that results from my vast experience. I am not heading downhill! I am just exercising my intelligence. Its a hopeful thought as we zoom towards 2007 and I continue the (so far) long march of life towards boot hill.