Reporting in the current issue (September) of the quarterly journal Psychology and Aging, the scientists say there is less white matter in the frontal lobes of those who struggle with focusing. The differences became apparent through the use of functional magnetic resonance (fMRI) imaging of the brains of 40 individuals ranging in age from 19 to 87.
"We found that both performance and brain-activation differences of older good performers and the older poor performers are predicted by changes in brain structure, specifically by the volume of white matter connecting the right and left hemispheres of the frontal lobes," said Arthur F. Kramer, a professor of psychology.
Participants took part in a "flanker" experiment in which they viewed a line of five keyboard arrows on a computer screen and reacted by pushing one of four buttons that corresponded with the direction the center arrow was pointing. Sometimes the participants would be distracted by changes in direction by arrows not in the center.
The experiment allowed researchers to study the ability to focus on important information and inhibit inappropriate information, Kramer said. Such focusing is important when driving a car, flying a plane or making a variety of everyday decisions.
Young people and high-functioning older adults tended to call upon tissue from the right frontal lobe -- specifically, the right middle frontal gyrus -- while some older, poorer-scoring participants also activated tissue in the left hemisphere (left middle frontal gyrus), said lead author Stan J. Colcombe, a research scientist at the Beckman Institute.