"Brain biochemistry doesn't just underpin our mental activity; our mental activity and thinking process can also affect the biochemistry," says Professor Klingberg, who led the study.

The neurotransmitter dopamine plays a key part in many of the brain's functions. Disruptions to the dopamine system can impair working memory, making it more difficult to remember information over a short period of time, such as when problem solving. Impaired working memory has, in its turn, proved to be a contributory factory to cognitive impairments in such disorders as ADHD.

Professor Klingberg and his colleagues have previously shown that the working memory can be improved with a few weeks' intensive training. Through a collaborative project conducted under the Stockholm Brain Institute, the researchers have now taken a step further and monitored the brain using PET scans, and have confirmed that intensive brain training leads to a change in the number of dopamine D1 receptors in the cortex.

In another study, University of Oregon researchers found that students with high working memory storage capacity were clearly better able to ignore distractions and stay focused on their assigned tasks.

Principal investigator Edward K. Vogel, a UO professor of psychology, compares working memory to a computer's random-access memory (RAM) rather than the hard drive's size — the higher the RAM, the better processing abilities. With more RAM, he said, students were better able to ignore distractions.