The mirror neuron system and motor dexterity: what happens?

The mirror neuron system (MNS) is currently one of the most prominent areas of research in neuroscience. Some of the work has focused on the identification of factors that modulate its activity, but until now, no one has tried to identify the effect of motor ability on the MNS regions. The aim of the present work is to study a possible modulation of hand dexterity on the MNS activity. A blocked fMRI experiment has been designed, consisting of an execution condition, where participants must repeatedly perform a precision grasping pantomime, and an observation condition, where the same motor action is passively observed. A conjunction analysis was performed in order to confirm the existence of mirror activity. Moreover, participants were classified depending on their hand dexterity (measured with the Purdue Pegboard Test) as "High dexterity" or "Low dexterity" and a regression analysis was performed to investigate a possible linear relationship between the degree of dexterity and brain activity in the MNS. The conjunction analysis revealed, as expected, activity in the inferior parietal lobule, a region that constitutes one of the nuclei of the putative MNS and which is consistently activated by intransitive actions. The degree of dexterity only seems to modulate MNS regions during action execution. However, under the observation condition, no linear relationship of hand dexterity in MNS regions was registered in either the comparison between groups, or in the regression analysis. Therefore, the MNS network does not seem to be linearly modulated by the degree of motor dexterity, as occurs with other action-related factors like familiarity.