Science/Medicine : Region of Brain Provides Storage of New Memories

New memories are processed in the hippocampus over a period of several weeks before being permanently stored elsewhere in the brain, psychiatrists Stuart M. Zola-Morgan and Larry R. Squire of UC San Diego reported last week in the journal Science. The new discovery helps to explain why damage to the hippocampus, common in some types of degenerative diseases, interferes with the victim’s ability to learn.

Zola-Morgan and Squire trained 18 cynomolgus monkeys to correctly choose one member of 100 pairs of objects. The objects were learned in groups of 20 at 16, 12, eight, four and two weeks before 11 of the monkeys had their hippocampuses surgically damaged. When the animals were retested two weeks after the surgery, the undamaged animals could remember more than 80% of the objects learned in the four weeks immediately before surgery, whereas the damaged ones could remember only 60%.

Both damaged and undamaged monkeys, however, could remember about 70% of all the objects learned more than eight weeks before the surgery, indicating that those memories were safely stored elsewhere in the brain.