Pitt-led study maps the making of a decision in the human brain

October 30, 2007

PITTSBURGH--The brain, the human supercomputer, might work more like an assembly line when recognizing objects, with a hierarchy of brain regions separately absorbing and processing information before a person realizes what they are seeing, according to new research conducted at the University of Pittsburgh and published in the Oct. 31 edition of the Journal of Neuroscience.

Led by Mark Wheeler, a psychology professor in Pitt's School of Arts and Sciences, and conducted at Pitt's Learning Research and Development Center, the research is a step toward mapping the human decision-making process. This study used an innovative technique and analysis to show that human decision-making is a collaboration of brain regions performing individual functions. Future work based on these findings could lead to a better understanding of how decisions--good and bad--are made and the considerations people put into them.

The study is the first in humans to separate the areas of the brain active in the time leading up to a decision--which Wheeler terms evaluation areas--from the areas associated with communication and thinking that are traditionally related to decision-making, Wheeler said. It then lays out a hierarchy for the evaluation stage.

Wheeler and his colleagues used functional magnetic resonance imaging (fMRI) to track brain activity as study participants tried to recognize images gradually revealed to them. The pictures were blacked out then gradually revealed until the person viewing them recognized the image. As expected, activity increased in the brain's vision-processing centers as the picture was revealed and the brain absorbed the information.

The surprise came when activity also increased steadily in the brain's areas for object processing, reasoning, and memory. This suggests that these regions evaluated the images in the context of memories and past experiences as new information became available. Meanwhile, the brain regions already known to be active when a person makes a decision showed little change in activity until the person identified the picture. The flourish suggests that these regions handled the final recognition once the information was gathered.

These findings are consistent with previous research on monkeys that has shown the brain areas that are active when a decision is made, Wheeler said; however, this project, aside from pertaining to humans, also is the first to map the decision-making and evidence-gathering process prior to the actual "eureka" moment, he said.

"We're the first to show in humans the dynamic evolution of decision-dependent activity that we believe reflects evidence gathering," Wheeler said. "Our results relate particular parts of the brain to the evidence-gathering process, when your brain is taking in information to find out what the possibilities are. These evaluation areas process the information until that salient moment that the object a person is trying to recognize becomes obvious."

Not yet obvious is where the final decision actually forms, Wheeler said. Further research is needed to determine the point between the information-processing regions and the areas active at the moment of recognition, when a person comes to a conclusion.
Wheeler worked with Pitt graduate student Elisabeth Ploran and graduate student Steve Nelson from Washington University in St. Louis. Also part of the research team were Katerina Velanova of Pitt's Department of Psychiatry in the School of Medicine; Steven Petersen, a cognitive neuroscience professor at Washington University in St. Louis; and Psychology Professor David Donaldson of Stirling University in the United Kingdom.

Wheeler also is affiliated with Pitt's Center for Neuroscience and the Center for the Neural Basis of Cognition, a collaboration of Pitt and Carnegie Mellon University.

For more information on this research, visit the Journal of Neuroscience Web site at www.jneurosci.org.

University of Pittsburgh

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