Cerebral activation patterns for subsequent practice stages differ between sensorimotor and cognitive tasks (Cereb. Cortex 2005;15:1089-102). Sensorimotor tasks are defined as those that involve repetitive movements of a specific body part, for example, the left fingers of a violinist. Ongoing repeated fingering movements enhance horizontal synaptic connectivity within the finger homunculus. Consequently, there is enhanced cortical activation of that region with the fingering movement because of the greater number of neurons recruited for that task's performance (Science 1995;270:305-7). Cognitive tasks, in contrast, rely upon the integration of multiple brain regions that are geographically distant and serve different functions. With practice, the relative activation of all these different areas diminishes perhaps because they become physiologically integrated into a functional network that requires less effort expenditure from each component region.
Practice effects powerfully influence the level of dexterity any normal human brain can attain. However, biological differences do exist among us and also influence dexterity levels, as we shall consider next month.