Precision grasping in humans: from motor control to cognition.

In the past decade, functional neuroimaging has proved extremely useful in mapping the human motor circuits involved in skilled hand movements. However, one major drawback of this approach is the impossibility to determine the exact contribution of each individual cortical area to precision grasping. Because transcranial magnetic stimulation (TMS) makes it possible to induce a transient 'virtual' lesion of discrete brain regions in healthy subjects, it has been extensively used to provide direct insight into the causal role of a given area in human motor behaviour. Recent TMS studies have allowed us to determine the specific contribution, as well as the timing and the hemispheric lateralisation, of distinct parietal and frontal areas to the control of both the kinematics and dynamics of precision grasping. Moreover, recent researches have shown that the same cortical network may contribute to language and number processing, supporting the existence of tight interactions between processes involved in cognition and actions. The aim of this paper is to offer a concise overview of recent studies that have investigated the neural correlates of precision grasping and the possible contribution of the motor system to higher cognitive functions such as language and number processing.