The same trick is seen when a normal subject performs a highly complex task. Cramer explained, Just to get out of bed in the morning, a stroke patient has to turn on all the areas of the brain a golfer would use to sink an 18-foot putt. A second brain trick, demonstrated by about half the normal subjects and half the recovered stroke patients, is an increased ability to recruit areas richly connected to the motor cortex of the brain to supplement the main motor control area. Supplemental motor areas now can be observed with functional magnetic resonance imaging. Their increased activity after stroke might represent alternate strategies to plan a movement, or could be reliance on undamaged pathways to carry messages out of the brain in parallel with pathways affected by the stroke.
Strokes vary in the amount of harm done.
Sometimes the wreckage is small and deep but hits like a bomb d ropped on Grand Central Station during rush hour. Other times, the damage is larger, extending to the brain's surface and boring a hole in the cortex. People recovering well from major stroke show a third type of brain cell regrouping. Their functio nal MRI's reveal active spots along the wound's rim. It's almost as though the brain relocated its motor headquarters to the nearest viable part of the cortex, Cramer said.