Brain region recalls new information

Reuters News

The region of the brain called the hippocampus is known to be involved in memory, but its exact role has been unclear. Now, two reports in the August 12th issue of Nature suggest that the hippocampus does not store old memories. Instead, it appears to play an important role in recalling things encountered recently, including remembering landmarks used to navigate our surroundings.

In one study, Drs. Edmond Teng and Larry R. Squire, of the University of California at San Diego, studied an elderly man who developed amnesia after an infection damaged his brain, including the hippocampus.

Since some experts believe that the hippocampus serves as the brain's atlas by storing information on places and how to navigate through them, the researchers set out to test how well the man remembered the streets of his boyhood hometown. Teng and Squire compared his memories to those of four other elderly people who had also moved away from the same town decades ago.

The man with amnesia was able to remember his hometown as well or better than the other elderly subjects did, but he could not remember the streets of his current neighborhood, where he moved after developing amnesia, the researchers report.

Based on these results, the hippocampus appears to play a role in creating memories, but not in retrieving old ones, Squire told Reuters Health in an interview. In addition, the man's ability to remember streets from his hometown but not from his current neighborhood casts doubt on the idea that the hippocampus stores the brain's maps, he said.

Instead, it appears to be involved in creating a person's "general purpose" memory, Squire said.

Another study in the same issue of the journal also suggests that the hippocampus is involved in recalling recently acquired knowledge. Dr. Bruno Bontempi and colleagues at the Universite Bordeaux I in Talence, France, studied mice that were placed in a maze 5 days or 25 days after they initially learned which parts of the maze contained food.

When they measured brain activity in the mice, the researchers detected more activity in the hippocampus in the 5-day group than in the 25-day group, according to the report. But activity in several other parts of the brain was higher in the 25-day group, Bontempi's team notes.

According to the researchers, the findings suggest that the hippocampus plays a role in making memories, as well as in retrieving recent ones. However, the hippocampus does not seem to be involved in long-term memory storage, Bontempi and colleagues conclude.

SOURCE: Nature 1999;400:671-674, 675-677.