Brain imaging studies in man and single cell recordings in monkey have suggested that medial supplementary motor areas (SMA) and lateral pre-motor areas (PMA) are functionally dissociated concerning their involvement in internally driven and externally cued movements. This dichotomy, however, seems to be relative rather than absolute. Here, we searched for further evidence of relative differences and aimed to determine by what aspect of brain activity (duration, strength, or both) these might be accounted for. Event-related potentials (ERPs) were recorded while healthy, right-handed subjects selected one of three possible right hand digit movements based either on 'internal' choice or 'external' cues. The results obtained from ERP mapping suggest that movement selection evokes the same electrical brain activity patterns in terms of surface potential configurations in the same order and at the same strength independent of the selection mode. These identical configurations, however, differed in their duration. Combined with the results of a distributed source localization procedure, our data are suggestive of longer lasting activity in SMA during the 'internal' and longer lasting activity in PMA during the 'external' condition. Our results confirm previous findings in showing that SMA and PMA are distinctively involved in the two tasks and that this functional dichotomy is relative rather than absolute but indicate that such a dissociation can result from differences in duration rather than pure strength of activation.
Matthias Wolf, Henry Markram, Kathryn Hess Bellwald, Felix Schürmann, Eilif Benjamin Muller, Srikanth Ramaswamy, Michael Reimann, Daniel Keller, Werner Alfons Hilda Van Geit, James Gonzalo King, Lida Kanari, Pramod Shivaji Kumbhar, Alexis Arnaudon, Ying Shi, Jean-Denis Georges Emile Courcol, Armando Romani, András Ecker, Michael Emiel Gevaert, Cyrille Pierre Henri Favreau, Vishal Sood, Sirio Bolaños Puchet, James Bryden Isbister, Judit Planas Carbonell, Daniela Egas Santander, Christoph Pokorny, Adrien Michel Achille Devresse, Gianluca Ficarelli, Hugo Thabo Dictus, Janis Lazovskis, Juan Bautista Hernando Vieites, Huanxiang Lu, Liesbeth Maria L Vanherpe, Ran Levi, Joni Henrikki Herttuainen, Samuel Lieven D. Lapere, Juan Luis Riquelme Roman, Thomas Brice Delemontex, Nicolas René Jean Ninin, Alexander Dietz, Benoît Jean-Albert Coste