High level of dexterity: differential contributions of frontal and parietal areas.

In the present functional magnetic resonance imaging experiment, study participants performed a dynamic tracking task in a precision grip configuration. The precision level of the force control was varied while the mean force level of 5 N was kept constant. Contrasts cancelling error rate differences between the conditions showed activation of nonprimary motor areas and other frontal structures in response to increasing precision constraints when the precision of force control could still be increased, and of right primary and associative parietal areas when the precision of the produced force control reached its maximum. These results suggest that the network of frontal and parietal areas, usually working together in fine control of dexterity tasks, can be differentially involved when environmental constraints become very high.