Uncovering the roots of unconscious memory

In In Search of Lost Time Proust describes a whole host of memories suddenly brought back to him when he dips a madeliene biscuit into a cup of lime tea. Psychologists call this process unconscious memory and researchers from the University of California Davis believe that they have found the region of the brain responsible for it. The researchers compared people with amnesia who had damage to an area of the brain called the perirhinal cortex to a group of healthy people. They gave the subjects a long list of words and asked them to think of any pleasant associations they brought to mind; later they were asked to think up words in different categories such as 'furniture.' The participants had MRI scans as they took the tests and in the healthy participants, who performed better in the tests, the perirhinal cortex showed increased activity. The study ties in with other research which shows that Alzheimer's disease often attacks the perirhinal cortex before other brain areas.