University of Pittsburgh scientists identify how brain 'gets ready' to perform

November 05, 2000

Findings presented at annual Society for Neuroscience meeting

NEW ORLEANS, Nov. 6 - Researchers at the University of Pittsburgh School of Medicine have uncovered the mechanism by which the brain prepares itself to solve a problem. Their research was presented today at the 30th Annual Meeting of the Society for Neuroscience.

The Pitt researchers, led by Cameron Carter, M.D., associate professor of psychiatry, conducted a series of functional magnetic resonance imaging (fMRI) studies showing that the part of the brain called the dorsolateral prefrontal cortex (DLPFC) becomes active when a person is preparing for a task. The more it activates, the better that person performs a given task. Yet, absent anticipation that a task needs to be performed, the DLPFC does not activate at all. According to Dr. Carter, the data suggest that DLPFC activation is associated with representing and maintaining the attentional demands of a task.

"This part of the brain plays a unique role in preparing us to perform a cognitive task," said Dr. Carter. "The DLPFC seems to look forward to what the brain needs to do next in order to perform the task better."

The current research adds to Dr. Carter's previous work, which identified the brain's error-checking device, and shows how several areas in the brain perform unique tasks in a team effort to solve problems.

According to Dr. Carter, this research may give scientists a greater understanding of psychiatric disorders, such as schizophrenia, by identifying the pathways normal brains use to perform cognitive functions and finding out how they differ in those with mental illness.

The researchers assessed the DLPFC - located on the outer surface of the frontal lobes of the brain - in relation to other brain regions linked to performance by devising tests that allowed them to watch subjects' brains respond to a variety of cognitive tasks during fMRI imaging of the brain.

The first study employed a task-switching Stroop test, in which subjects were challenged to either name the color a word was written in (when the word itself spelled a color) or just read the word out loud. This is difficult because the test-taker has to ignore the word and pay attention to the color, say for example if the word "red" is in blue ink. In contrast, having to read the word itself is easy. When participants knew they would have to say the color of the letters, their DLPFC kicked into high gear to help them prepare. The more activity a subject had in his DLPFC, the better he was able to do on the test.

The second study was a task-switching experiment in which tasks were equally difficult and in which task-related conflict, but not response conflict, was elicited. To determine the role of the DLPFC in task preparation, on some trials subjects knew that they were going to have to switch to a different task, on others they did not. When a person knew they would have to switch to a different task, the DLPFC would activate. When the person was not told about the upcoming task, or when they simply repeated the task that they had just performed, the DLPFC stayed quiet.

"In both studies, DLPFC activity corresponded with good performance," said Dr. Carter. "Further, we found that people whose brains can activate the DLPFC quickly as they get ready to do a task perform much better than those whose brains can't."

Other areas of the brain also play a role in performance, said Dr. Carter. In the first test, a person's anterior cingulate cortex (ACC), located on the inner surface of the frontal lobes - which acts as a yellow flag for the brain to be watchful for mistakes - became active when subjects knew they would have to identify colors when the word and colors were different, but not when the word and color were the same. In the second test, subjects' ACCs were not as active because the tests were not designed to elicit response conflict. The parietal cortex, toward the back of the brain, however, was active when people prepared for all tasks, but its response was not specific to whether they were preparing to perform the same task or different tasks.

"The bottom line is that although many regions of the brain work together and participate in executive functions, different regions appear to make unique contributions to the process. The DLPFC seems to be uniquely involved in preparing attention for what is just about to happen and is more active when a person has to prepare to overcome a habitual response or switch from one task to another. The parietal cortex lets a person prepare attention or link appropriate stimuli to their correct response, and the ACC detects conflict and lets a person know when he is not doing very well," said Dr. Carter.
In addition to Dr. Carter, other Pitt researchers involved include Angus MacDonald (a graduate student in psychology), Stefan Ursu (a graduate student in neuroscience) and Andy Stenger, M.D., assistant professor of radiology, University of Pittsburgh School of Medicine and Myeong Ho Sohn and John Anderson, psychologists at Carnegie Mellon University.

Craig Dunhoff
Lisa Rossi
PHONE: (412) 624-2607
FAX: (412) 624-3184

University of Pittsburgh Medical Center

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