Wolfensteller Uta, Schubotz Ricarda I, von Cramon D Yves
Department of Cognitive Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, 04303 Leipzig, Germany.
J Neurosci. 2004 Nov 17;24(46):10431-9. doi: 10.1523/JNEUROSCI.2641-04.2004.
Previous studies using the serial prediction task (SPT) have shown that attending to the locations of objects activates the dorsal part of premotor cortex more than attending to the sizes of objects. The opposite holds for the ventral part of the premotor cortex. The present study used functional magnetic resonance imaging to investigate whether the learning of arbitrary stimulus-response mappings influences this functional dissociation. One experimental group learned to assign stimuli to response buttons based on stimulus size; another group did so based on stimulus location. More specifically, one-half of the participants in both experimental groups learned to assign stimuli to finger movements of their right hand, whereas the other half assigned stimuli to finger movements of their left hand. During scanning, all participants performed both size SPT and location SPT. Thus, we investigated the effects of the attended stimulus property (size or location), the motor effector assigned to it (fingers of left or right hand), and the spatial arrangement of the targets (the same in all groups). As expected, without motor training, the dorsal premotor cortex was less activated during size SPT compared with location SPT. The opposite held for ventral premotor cortex. With motor training, however, this differential activity pattern vanished. Activity in dorsal premotor cortex reflected neither the attended stimulus property nor the motor effector assigned to it. Instead, its activity may be related to the spatial properties of the response targets once some object property, such as size, takes on the "pragmatic relevance" of a spatially directed response.
以往使用序列预测任务（SPT）的研究表明，关注物体的位置比关注物体的大小更能激活运动前皮质的背侧部分。运动前皮质腹侧部分的情况则相反。本研究使用功能磁共振成像来探究任意刺激-反应映射的学习是否会影响这种功能分离。一个实验组学习根据刺激大小将刺激分配到反应按钮上；另一组则根据刺激位置进行分配。更具体地说，两个实验组中各有一半的参与者学习将刺激分配到右手的手指动作上，而另一半则将刺激分配到左手的手指动作上。在扫描过程中，所有参与者都执行了大小SPT和位置SPT。因此，我们研究了所关注的刺激属性（大小或位置）、分配给它的运动效应器（左手或右手的手指）以及目标的空间排列（所有组中均相同）的影响。正如预期的那样，在没有运动训练的情况下，与位置SPT相比，大小SPT期间背侧运动前皮质的激活程度较低。运动前皮质腹侧部分的情况则相反。然而，经过运动训练后，这种差异活动模式消失了。背侧运动前皮质的活动既不反映所关注的刺激属性，也不反映分配给它的运动效应器。相反，一旦某些物体属性（如大小）具有空间定向反应的“实用相关性”，其活动可能与反应目标的空间属性有关。
