Karen McNulty Walsh
November 29, 2011
“The more gray matter you have in the decision-making, thought-processing part of your brain, the better your ability to evaluate rewards and consequences. That may seem like an obvious conclusion, but a new study conducted at the U.S. Department of Energy’s Brookhaven National Laboratory is the first to show this link between structure and function in healthy people — and the impairment of both structure and function in people addicted to cocaine. The study appears in the Journal of Cognitive Neuroscience.
Methodology and key findings -Structural analysis of the MRI scans was performed using voxel-based morphometry (VBM). VBM is a whole-brain, fully automated, unbiased and operator-independent MRI analysis technique that is commonly used to detect regionally specific differences in brain tissue composition using voxel-wise comparisons. The gray matter tissue probability from each voxel was then correlated with the P300 amplitude difference between the highest monetary reward (45 cents per correct response) and no money (0 cents) conditions of a sustained attention task. The red/orange/yellow highlights on these brain scans indicate the regions where the correlation between gray matter volume and differential P300 response was quite strong in healthy control subjects but weak or nonexistent in cocaine-addicted individuals — the dorso-lateral and ventro-lateral prefrontal cortex, anterior cingulate cortex, and the orbitofrontal cortex, which are known to be functionally involved in reward processing and decision-making. These results suggest that the structural integrity of the prefrontal cortex modulates electrocortical sensitivity to monetary reward. Impairments in these regions may also be related to decreased ability to assess and respond to other modulated rewards and consequences, such as those associated with using addictive drugs.
‘This study documents for the first time the importance to reward processing of gray matter structural integrity in the parts of the brain’s prefrontal cortex that are involved in higher-order executive function, including self-control and decision-making, said Muhammad Parvaz, a post-doctoral fellow at Brookhaven Lab and a co-lead author on the paper.
‘Previous studies conducted at Brookhaven and elsewhere have explored the structural integrity of the prefrontal cortex in drug addiction and the functional components of reward processing, but these studies were conducted separately,’ Parvaz said. ‘We wanted to know whether the specific function of reward processing could be ‘mapped’ onto the underlying brain structure — whether and how these two are related,’ he added.”
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One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.