Thursday, August 12, 1999 Published at 12:24 GMT 13:24 UK
A trip down memory lane
The patient provided an opportunity to test assumptions
A 76-year-old American suffering from amnesia has offered science new insights into how our brains store memories about the world around us.
He is featured in one of two research papers in the current edition of Nature magazine that show, just like computers, our brains have separate storage areas for working memory and archive information.
The US patient, known only as EP, got an infection in 1992 that led to major memory loss. It was so severe that the man constantly failed to recognise even the researchers working with him, despite 40 visits to his home in one year.
Brain scans revealed major damage to EP's hippocampus - an area at the centre of the brain that experiments suggest is probably involved in how we map out our physical environment.
Work in rodents has indicated that the hippocampus is especially important for spatial memory - both for forming and storing spatial maps. Edmond Teng and Larry Squire of the University of California San Diego, realised that E P offered a unique opportunity to test the theory.
In some surprising tests, the researchers found that EP could remember geographical details about his home town, a place he moved away from over 50 years ago, and even outperformed some of his old school friends who had also since moved away.
But any questions about his current neighbourhood drew a complete blank from EP - he could remember nothing about where he lived or any of the major landmarks. This showed Teng and Squire that the brain stores new and old geographical, the so-called spatial, memories in different places.
Separate research reported by French scientists at the University of Bordeaux, also in the current Nature magazine, explains what could be happening.
Their experiments on mice show that although the brain stores recent spatial memories in the hippocampus, after a certain period - within 25 days in mice - these recollections are re-filed or downloaded to an archive area in the brain's outer regions.
It seems that, like computers, our brains have an efficient filing system - moving old memories to long term storage for safe keeping.