How memory and spatial cognition are related

Washington, August 6 : U.S. researchers have gained fresh insights into how memory and special cognition are related.

Researchers at the University of California, San Diego School of Medicine and the Veteran Affairs (VA) San Diego Healthcare System say that their findings are based on a study of memory-impaired patients as they navigated their environment.

The researchers say that path integration - the brain's ability to compute the distance and direction of a travelled path - is an important aspect of spatial cognition, which has been long-thought to be dependent on the medial temporal lobe structures of the brain.

However, they insisted, their study showed that the hippocampus and entorhinal cortex - two major medial temporal lobe structures - are not essential for path integration.

Lead researcher Dr. Larry R. Squire said that the study, reported in the online edition of Proceedings of the National Academy of Sciences (PNAS), was designed to measure whether these structures of the brain are essential for spatial cognition.

"For decades, the medial temporal lobe structures have been linked to both memory and spatial cognition," said Squire.

The researcher further said that one important aspect of spatial cognition was keeping track of a reference location during movement by using internal cues, yet such tracking also relied on memory.

"So we set out to test how these two abilities related to one another and to the temporal lobe area of the brain," Squire added.

During the study, the researchers looked at five memory-impaired patients with lesions of the medial temporal lobe along with seven matched controls, testing each for their path integration ability.

Participants who were blindfolded and wore noise-canceling earphones were led by researchers on 16 paths, and asked to keep their starting point in mind.

After walking the path, participants were asked to point to their start location.

The researchers found that the memory-impaired patients pointed to and estimated their distance from the start location as accurately as the controls.

"We concluded that the hippocampus and entorhinal cortex are not essential for path integration, since we showed that the tests could be successfully accomplished despite damage to these brain regions," said Squire.

ANI