... . A few years ago, brain scans of London cabbies showed that the detailed mental maps they had built up in the course of navigating their city's complicated streets were apparent in their brains. Not only was the posterior hippocampus - one area of the brain where spatial representations are stored - larger in the drivers; the increase in size was proportional to the number of years they had been on the job.
... there is also accumulating evidence that the brain can change autonomously, in response to its own internal signals. Last year, Tibetan Buddhist monks, with the encouragement of the Dalai Lama, submitted to functional magnetic resonance imaging as they practiced ''compassion meditation,'' which is aimed at achieving a mental state of pure loving kindness toward all beings. The brain scans showed only a slight effect in novice meditators. But for monks who had spent more than 10,000 hours in meditation, the differences in brain function were striking. Activity in the left prefrontal cortex, the locus of joy, overwhelmed activity in the right prefrontal cortex, the locus of anxiety. Activity was also heightened in the areas of the brain that direct planned motion: ''... as if the monks' brains were itching to go to the aid of those in distress ... ''
from the NY Times