RESEARCH ARTICLE Regine K. Lange Æ Christoph Braun Æ Ben Godde Coordinate processing during the left-to-right hand transfer investigated by EEG Received: 5 January 2005 / Accepted: 25 June 2005 / Published online: 18 November 2005 Ó Springer-Verlag 2005 Abstract Information about visuomotor tasks is coded in extrinsic, object-centered and intrinsic, body-related coordinates. For the reproduction of a trained task in mirror orientation with the opposite untrained hand, acquired extrinsic coordinates must be transformed. In contrast, intrinsic coordinates have to be modified dur- ing the execution of the originally oriented task. As shown recently, processes of coordinate transformations during the right-to-left hand transfer are associated with movement preparation and occur preferentially in the left hemisphere. Here, movement-related potentials, EEG power, and EEG coherence were recorded during the repetition of a drawing task previously trained by the nondominant left hand (Learned-task) and its execution in original and mirror orientation by the right hand (Normal- and Mirror-task). To identify EEG correlates of coordinate processing during intermanual transfer rather than effects due to the use of the right versus left hand, only those EEG data were analyzed which differed between the Normal- and Mirror-tasks. Whereas the Normal-task did not differ from the Learned-task in any of these predefined EEG parameters, beta coherence increased in the Mirror-task in the period ranging from 1 to 2s after movement onset. These increases were especially prominent between hemispheres but were also observed symmetrically in the parieto-frontal electrode pairs of both hemispheres. Behavioral data revealed that the performance in the Learned- and both transfer tasks improved after left-hand training. Results of the present study indicate that coordinate transformation during the left-to-right hand transfer occurs in the phase of move- ment execution and affects predominantly extrinsic coordinates. Intrinsic coordinates are presumably mainly used in their original form. The modification of extrinsic coordinates is accompanied by increased information flow between both hemispheres; thereby inter-hemispheric connections—as mediated via the corpus callosum—seem to play a central role. Keywords Coordinate transformation Æ Intermanual transfer Æ Inter-hemispheric projection Æ EEG Æ Coherence Æ Motor learning Introduction The phenomenon that unilateral hand training affects performance of the other hand provides evidence that the CNS is capable of using skills acquired with one hand for the adequate control of the other hand. It has been proposed that coordinates of movement trajecto- ries are stored in different frames of reference (Kawato et al. 1988; Atkeson 1989; Andersen et al. 1993; McIn- tyre et al. 1997, 1998), which have to be mapped onto each other in visuomotor tasks (Soetching and Flanders 1989; Andersen et al. 1997; Vetter et al.1999; Buneo et al. 2002). Coordinates that describe the position of an object in the subject’s peripersonal space are referred to as ‘extrinsic’ coordinates. In contrast, ‘intrinsic’ coordi- nates describe the orientation of body segments with respect to each other (Soetching and Flanders 1989). Depending on the orientation of the task performed during intermanual transfer, learned information of ei- ther the extrinsic or the intrinsic reference frame can be used in its original learned form, while information of the other coordinate system must be transformed. During the control of the task in its original orientation—referred to here as Normal-task—extrinsic coordinates can be R. K. Lange Æ C. Braun Æ B. Godde Institute of Medical Psychology and Behavioral Neurobiology, University of Tu¨bingen, Tu¨bingen, Germany B. Godde (&) Jacobs Center for Lifelong Learning, International University Bremen, P.O. Box 750561, 28725 Bremen, Germany E-mail: b.godde@iu-bremen.de Tel.: +49-421-2004760 Fax: +49-421-200494760 C. Braun MEG-Center, University of Tu¨bingen, Tu¨bingen, Germany Exp Brain Res (2006) 168: 547–556 DOI 10.1007/s00221-005-0117-8