The ability to make decision in new situations gradually declines with age and is linked with a reduction in the integrity of two specific white-matter pathways that connects a region in the cerebral cortex with two other regions deeper in the brain, according to a new study published in ‘The Journal of Neuroscience.’

White matter consists of cables like substances called axons, which carry signals from one part of the brain to another. It is associated with brain's processing speed and attention span, among other things.

"The evidence that this decline in decision-making is associated with white-matter integrity suggests that there may be effective ways to intervene," said Gregory R. Samanez-Larkin, the post-doctoral fellow in Vanderbilt's psychology department and Institute of Imaging Science, who is the study's first author. "Several studies have shown that white-matter connections can be strengthened by specific forms of cognitive training," he added.

A study was conducted involving 25 adults the ages 21 to 85 years. The participants were asked to perform a monetary learning task. The task was designed to get information which psychologists call probabilistic reward learning. "This is a common type of decision making that we use every day," said Samanez-Larkin. "Whenever we try to choose the best alternative based on previous experience and are uncertain of the outcome, we are relying on probabilistic reward learning."

Then the participants were scanned using diffusion tensor imaging (DTI) on the same day. DTI is a new MRI technique which detects the water trapped by the myelin sheaths that surround the axons in white-matter regions and produces a signal related to the density, diameter and amount of myelination of the axons. The signals combined give the integrity of the proteins present in white matter.

"The protocols for DTI have improved substantially," said Samanez-Larkin, "In future studies we'd really like to combine fMRI and DTI to better characterize age differences in these neural circuits and examine how training might improve both structure and function."

Financial Industry Regulatory Authority Investor Education Foundation and the National Institute on Aging funded the research.