Brain Damage May Not Harm Short-Term Spatial Memory After All
TUESDAY Oct. 12, 2010 -- New research suggests the short-term ability to remember bits of information involving spatial reasoning is not jeopardized by injury to the part of the brain that is central to memory.
The observation, which runs contrary to previous thought, concerns what researchers refer to as "working memory," namely the ability to remember in the short run, rather than the long term.
This would mean that patients should be able to retain the ability, for example, to recall where they just put their keys even after suffering damage to a part of the brain that researchers have long identified as critical to memory function.
"The findings provide strong evidence for a fundamental distinction in the brain between working memory and long-term memory, even in the realm of spatial information and spatial-object associations," lead author Larry R. Squire, a professor of psychiatry, psychology and neurosciences at the University of California, San Diego School of Medicine, said in a university news release.
Squire, who is also a scientist at the VA San Diego Healthcare System, reports his team's findings in the Oct. 13 issue of The Journal of Neuroscience.
The researchers worked with four patients with damage to their medial temporal lobes (MTL) in the cerebral cortex region of the brain where the hippocampus is located. The MTL is linked to long-term memory, and all the patients were categorized as "memory-impaired."
After studying object arrangements on a table, the patients were asked to reconstruct the same arrangement on another table.
The patients had no problem doing so when only three or fewer objects were involved, thereby only requiring short-term memory function. But when the number of objects exceeded three, long-term memory function kicked in, and the patients started to have difficulty recreating the table arrangement.
"Their performance abruptly collapsed when the limit of working memory was reached," Squire said.
"It indicates that patients with memory impairment due to MTL damage, including early-stage Alzheimer's disease, have a narrower difficulty than what one might have thought," he noted. "They have an intact ability to hold information in [the] mind, and an ability to work with it on a temporary basis."
For more on memory and the brain, visit the Canadian Institutes of Health Research.
Posted: October 2010