Distinguishing neural sources of movement preparation and execution An electrophysiological analysis Hartmut Leuthold *, Ines Jentzsch Department of Psychology, University of Glasgow, 58 Hillhead Street, Glasgow G12 8QB, UK Received 20 September 2001; accepted 21 April 2002 Abstract The present study examined lateralized event-related potentials (L-ERPs) associated with movement preparation and execution. In a response precuing task that involved hand and foot movements a precue conveyed either information about side and effector, side alone, or no information. Advance movement preparation was indicated by RT shortening with increasing amount of precue information. L-ERPs revealed during the preparatory interval an initial parietal activity when movement side was precued. Later in the preparatory interval L-ERPs revealed a polarity inversion for foot versus hand movements when effector and side were specified in advance. This polarity inversion showed up also in execution-related L-ERP waveforms. Comparison of preparation- versus execution-related brain signals yielded topographic differences and dissimilar dipole sources for hand-related L-ERP activity. We take present findings to indicate that brain generators within the parietal lobe and anterior MI are hierarchically related to precue-induced motor preparation, whilst posterior MI is associated with motor execution functions. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Movement preparation; Movement execution; Lateralized readiness potential; Reaction time; Source localization * Corresponding author. Tel.:  /44-141-330-6847; fax:  /44-141-330-4606 E-mail address: h.leuthold@psy.gla.ac.uk (H. Leuthold). Biological Psychology 60 (2002) 173  /198 www.elsevier.com/locate/biopsycho 0301-0511/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0301-0511(02)00032-7