With focus was on the frontal cortex, which is critical for executive functions, and its connections to other parts of the brain during fMRI scanning, the researchers asked participants to perform four different tasks in two-minute trials, with five trials assigned to each participant for each task.

Images of faces and scenes, each selected from a set of 10, were flashed before the subjects sequentially, with each displayed for six-tenths of a second, followed by a pause of varying length before the next was displayed.

The easiest task required participants to press a button to categorize a displayed image as either a scene or a face, and the most difficult task was to recall both the previous face and previous scene.

Compared to a task-free "resting state," older adults performing tasks of any difficulty recruited additional between-module connections. In contrast, younger adults recruited additional between-module connections only for the most difficult task.

Most previous research in which researchers looked at age-related changes in brain function due to specific cognitive demands focused on activation of individual brain regions rather than taking a network approach, Gallen said in a news release from UC Berkeley.

Earlier studies showed that frontal activity in the brain increases in older adults compared to younger adults during less-demanding cognitive tasks.

"Our new results further support the idea of compensatory recruitment and suggest a large-scale network-level mechanism by which the aging brain reorganizes to support executive control processing," she said.