Lange Regine K, Braun Christoph, Godde Ben
Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany.
Exp Brain Res. 2006 Jan;168(4):547-56. doi: 10.1007/s00221-005-0117-8. Epub 2005 Nov 18.
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 during 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 2 s 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 movement 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.
视觉运动任务的信息以外部的、以物体为中心的以及内部的、与身体相关的坐标进行编码。要使用对侧未经训练的手以镜像方向重现训练过的任务，必须转换已习得的外部坐标。相比之下，在执行原始方向的任务时，内部坐标必须进行修改。最近的研究表明，从右手到左手转换过程中的坐标转换过程与运动准备相关，并且优先发生在左半球。在此，在重复先前由非优势左手训练的绘图任务（习得任务）以及右手以原始和镜像方向执行该任务（正常任务和镜像任务）期间，记录了与运动相关的电位、脑电图功率和脑电图相干性。为了识别双手转换过程中坐标处理的脑电图相关因素，而不是由于使用右手与左手导致的影响，仅分析了正常任务和镜像任务之间存在差异的那些脑电图数据。正常任务在这些预定义的脑电图参数中与习得任务没有差异，而在运动开始后1至2秒的时间段内，镜像任务中的β相干性增加。这些增加在半球之间尤为明显，但在两个半球的顶叶 - 额叶电极对中也对称地观察到。行为数据显示，左手训练后，习得任务和两种转换任务的表现均有所提高。本研究结果表明，从左手到右手的转换过程中的坐标转换发生在运动执行阶段，并且主要影响外部坐标。内部坐标大概主要以其原始形式使用。外部坐标的修改伴随着两个半球之间信息流的增加；因此，通过胼胝体介导的半球间连接似乎起着核心作用。
