In her quest to examine the contents of consciousness, a scientist at The Johns Hopkins University has produced new evidence of the evolutionary path from the monkey brain to the human.
Susan Courtney, an assistant professor of psychology, recently reported that she had pinpointed the place where the human brain stockpiles information about spatial relationships for short-term use.
It was not where anyone expected.
Until recently, many scientists argued that storage depots for short-term memory (called "working memory") in humans were probably located in the same place as in monkeys; memory of spatial relationships was thought to be stored in the top half of the frontal cortex and memory of objects was stored in the bottom half.
But using a relatively new brain-mapping technology called functional magnetic resonance imaging (fMRI*), Courtney discovered that the human brain has a dedicated place for spatial working memory located further back in the brain anatomy.
"Until now, it's been rather controversial," Courtney said, "because people have based their theories about human brain physiology on what they have seen in non-human primates. And yet when scientists went looking for a particular place for spatial working memory in humans, they couldn't find it. But now, with the help of new technologies such as fMRI, we can see where the human brain handles some of its short-term storage."
"The difference has interesting implications for human brain evolution," Courtney said.
"The comparison indicates that there has been a great expansion of the frontal
cortex in the evolution from monkeys to humans, pushing this older area,
reserved for spatial memory, out of the way," she said. "Of course, one of the
big questions is what replaced it. From the imaging work and from studies of
people with damage to that part of the brain
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Contact: Gary Dorsey
gdd@jhu.edu
410-516-7160
Johns Hopkins University
27-Jan-1999