The advanced brain imaging technology available to doctors today such as CAT scans, MRIs etc not only show the structure of the brain but informs the function of the brain as well. Therefore during an experiment, with brain imaging, doctors can tell what part of the brain is responding or being utilized for a particular task. Restak also explains that new brain pathways and circuits are built with each new experience and circuits are strengthened by continued use. As we practice certain tasks the circuits responsible for that task are strengthened. "Both comparatively straightforward activities and highly sophisticated ones, like learning to become a star athlete or musician, involved taking advantage of the brain's plasticity in order to set up the necesary programs for excellence," says Restak.
Practice matters. I've always known this but in The New Brain Dr. Restak explains WHY.
Also, multitasking can hurt. When multitasking we're not focusing on either task 100% and are therefore less efficient and are in fact training our brain to be less focused. By multi-tasking we strenghten the circuits of the brain that accept a divided focus approach. Chapter 3: Attention Deficit: The Brain Syndrome of Our Era, discusses this.
" 'Civilization is revving itself into a pathologically short attention span. The trend might be coming from the acceleration of technology, the short-horizon perspective of market-driven economies, the next-election perspective of democracies, or the distractions of personal multitasking. All are on the increase,' according to Stewart Brand, a noted commentator on technology and social change."
Great book.