Thinking and choosing depend on different brain parts

Washington, August 22 (ANI): By examining patients with lesions in the brain, researchers have been able to see exactly which parts of the frontal lobes are critical for tasks like behavioural control and decision-making.

The frontal lobes are the largest part of the human brain, and thought to be the part that expanded most during human evolution. Damage to the frontal lobes-which are located just behind and above the eyes-can result in profound impairments in higher-level reasoning and decision-making.

To find out more about what different parts of the frontal lobes do, neuroscientists at the California Institute of Technology (Caltech) recently teamed up with researchers at the world's largest registry of brain-lesion patients.

By mapping the brain lesions of these patients, the team was able to show that reasoning and behavioural control are dependent on different regions of the frontal lobe than the areas called upon when making a decision.

The team analysed data that had been acquired over a 30-plus-year time span by scientists from the University of Iowa's department of neurology-which has the world's largest lesion patient registry. They used that data to map brain activity in nearly 350 people with damage, or lesions, in their frontal lobes. The records included data on the performances of each patient while doing certain cognitive tasks.

"These are really unique data that could not have been obtained anywhere else in the world," explained Jan Glascher, lead author of the study and a visiting associate in psychology at Caltech.

That quantification of the lesions as well as the different task measurements came from several decades of work led by two coauthors on the study: Hanna Damasio, Dana Dornsife Chair in Neuroscience at the University of Southern California (USC); and Daniel Tranel, professor or neurology and psychology at the University of Iowa.

"The patterns of lesions that impair specific tasks showed a very clear separation between those regions of the frontal lobes necessary for controlling behaviour, and those necessary for how we give value to choices and how we make decisions," said Tranel.

Ralph Adolphs, Bren Professor of Psychology and Neuroscience at Caltech and a co-author of the study, noted that aspects of what the team found had been observed previously using fMRI methods in healthy people. But, he said, those previous studies only showed which parts of the brain are activated when people think or choose, but not which are the most critical areas, and which are less important.

"Only lesion mapping, like we did in the present study, can show you which parts of the brain are actually necessary for a particular task. This information is crucial, not only for basic cognitive neuroscience, but also for linking these findings to clinical relevance," he added.

Their findings are described online this week in the early edition of the Proceedings of the National Academy of Sciences (PNAS). (ANI)