Deiber M P, Wise S P, Honda M, Catalan M J, Grafman J, Hallett M
Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, Bethesda 20892-1428, USA.
J Neurophysiol. 1997 Aug;78(2):977-91. doi: 10.1152/jn.1997.78.2.977.
Studies on nonhuman primates show that the premotor (PM) and prefrontal (PF) areas are necessary for the arbitrary mapping of a set of stimuli onto a set of responses. However, positron emission tomography (PET) measurements of regional cerebral blood flow (rCBF) in human subjects have failed to reveal the predicted rCBF changes during such behavior. We therefore studied rCBF while subjects learned two arbitrary mapping tasks. In the conditional motor task, visual stimuli instructed which of four directions to move a joystick (with the right, dominant hand). In the evaluation task, subjects moved the joystick in a predetermined direction to report whether an arrow pointed in the direction associated with a given stimulus. For both tasks there were three rules: for the nonspatial rule, the pattern within each stimulus determined the correct direction; for the spatial rule, the location of the stimulus did so; and for the fixed-response rule, movement direction was constant regardless of the pattern or its location. For the nonspatial rule, performance of the evaluation task led to a learning-related increase in rCBF in a caudal and ventral part of the premotor cortex (PMvc, area 6), bilaterally, as well as in the putamen and a cingulate motor area (CM, area 24) of the left hemisphere. Decreases in rCBF were observed in several areas: the left ventro-orbital prefrontal cortex (PFv, area 47/12), the left lateral cerebellar hemisphere, and, in the right hemisphere, a dorsal and rostral aspect of PM (PMdr, area 6), dorsal PF (PFd, area 9), and the posterior parietal cortex (area 39/40). During performance of the conditional motor task, there was only a decrease in the parietal area. For the spatial rule, no rCBF change reached significance for the evaluation task, but in the conditional motor task, a ventral and rostral premotor region (PMvr, area 6), the dorsolateral prefrontal cortex (PFdl, area 46), and the posterior parietal cortex (area 39/40) showed decreasing rCBF during learning, all in the right hemisphere. These data confirm the predicted rCBF changes in premotor and prefrontal areas during arbitrary mapping tasks and suggest that a broad frontoparietal network may show decreased synaptic activity as arbitrary rules become more familiar.
对非人类灵长类动物的研究表明，运动前区（PM）和前额叶区（PF）对于将一组刺激任意映射到一组反应是必需的。然而，对人类受试者进行的正电子发射断层扫描（PET）测量区域脑血流量（rCBF）的结果未能揭示在这种行为过程中预测的rCBF变化。因此，我们在受试者学习两项任意映射任务时研究了rCBF。在条件性运动任务中，视觉刺激指示用右手（优势手）将操纵杆向四个方向中的哪一个移动。在评估任务中，受试者将操纵杆沿预定方向移动，以报告箭头是否指向与给定刺激相关的方向。对于这两项任务都有三条规则：对于非空间规则，每个刺激内的模式决定正确方向；对于空间规则，刺激的位置决定正确方向；对于固定反应规则，无论模式或其位置如何，移动方向都是恒定的。对于非空间规则，评估任务的执行导致双侧运动前皮质尾侧和腹侧部分（PMvc，6区）以及左侧半球的壳核和扣带运动区（CM，24区）的rCBF与学习相关地增加。在几个区域观察到rCBF减少：左侧眶额前皮质（PFv，47/12区）、左侧小脑半球外侧，以及右侧半球运动前区的背侧和嘴侧部分（PMdr，6区）、背侧前额叶区（PFd，9区）和顶叶后皮质（39/40区）。在条件性运动任务执行期间，仅顶叶区域的rCBF减少。对于空间规则，评估任务中没有rCBF变化达到显著水平，但在条件性运动任务中，腹侧和嘴侧运动前区（PMvr，6区）、背外侧前额叶皮质（PFdl，46区）和顶叶后皮质（39/40区）在学习期间rCBF均减少，均在右侧半球。这些数据证实了在任意映射任务期间运动前区和前额叶区预测的rCBF变化，并表明随着任意规则变得更加熟悉，广泛的额顶网络可能显示突触活动减少。
