Fink G R, Marshall J C, Halligan P W, Frith C D, Driver J, Frackowiak R S, Dolan R J
Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK.
Brain. 1999 Mar;122 ( Pt 3):497-512. doi: 10.1093/brain/122.3.497.
Normal sensorimotor states involve integration of intention, action and sensory feedback. An example is the congruence between motor intention and sensory experience (both proprioceptive and visual) when we move a limb through space. Such goal-directed action necessitates a mechanism that monitors sensorimotor inputs to ensure that motor outputs are congruent with current intentions. Monitoring in this sense is usually implicit and automatic but becomes conscious whenever there is a mismatch between expected and realized sensorimotor states. To investigate how the latter type of monitoring is achieved we conducted three fully factorial functional neuroimaging experiments using PET measures of relative regional cerebral blood flow with healthy volunteers. In the first experiment subjects were asked to perform Luria's bimanual co-ordination task which involves either in-phase (conditions 1 and 3) or out-of-phase (conditions 2 and 4) bimanual movements (factor one), while looking towards their left hand. In half of the conditions (conditions 3 and 4) a mirror was used that altered visual feedback (factor two) by replacing their left hand with the mirror image of their right hand. Hence (in the critical condition 4) subjects saw in-phase movements despite performing out-of-phase movements. This mismatch between intention, proprioception and visual feedback engendered cognitive conflict. The main effect of out-of-phase movements was associated with increased neural activity in posterior parietal cortex (PPC) bilaterally [Brodmann area (BA) 40, extending into BA 7] and dorsolateral prefrontal cortex (DLPFC) bilaterally (BA 9/46). The main effect of the mirror showed increased neural activity in right DLPFC (BA 9/ 46) and right superior PPC (BA 7) only. Analysis of the critical interaction revealed that the mismatch condition led to a specific activation in the right DLPFC alone (BA 9/46). Study 2, using an identical experimental set-up but manipulating visual feedback from the right hand (instead of the left), subsequently demonstrated that this right DLPFC activation was independent of the hand attended. Finally, study 3 removed the motor intentional component by moving the subjects' hand passively, thus engendering a mismatch between proprioception and vision only. Activation in the right lateral prefrontal cortex was now more ventral than in studies 1 or 2 (BA 44/45). A direct comparison of studies 1 and 3 (which both manipulated visual feedback from the left hand) confirmed that a ventral right lateral prefrontal region is primarily activated by discrepancies between signals from sensory systems, while a more dorsal area in right lateral prefrontal cortex is activated when actions must be maintained in the face of a conflict between intention and sensory outcome.
正常的感觉运动状态涉及意图、动作和感觉反馈的整合。一个例子是当我们在空间中移动肢体时，运动意图与感觉体验（本体感觉和视觉）之间的一致性。这种目标导向的动作需要一种机制来监测感觉运动输入，以确保运动输出与当前意图一致。从这个意义上说，监测通常是隐性的和自动的，但只要预期的和实际的感觉运动状态之间存在不匹配，就会变得有意识。为了研究后一种监测是如何实现的，我们使用正电子发射断层扫描（PET）测量相对局部脑血流量，对健康志愿者进行了三项全因子功能神经成像实验。在第一个实验中，受试者被要求执行卢里亚的双手协调任务，该任务涉及同相（条件1和3）或异相（条件2和4）双手运动（因素一），同时看向他们的左手。在一半的条件下（条件3和4），使用一面镜子，通过用右手的镜像替换左手来改变视觉反馈（因素二）。因此（在关键条件4中），受试者尽管执行的是异相运动，但看到的却是同相运动。意图、本体感觉和视觉反馈之间的这种不匹配引发了认知冲突。异相运动的主要效应与双侧顶叶后皮质（PPC）[布罗德曼区域（BA）40，延伸至BA 7]和双侧背外侧前额叶皮质（DLPFC）（BA 9/46）神经活动增加有关。镜子的主要效应仅显示右侧DLPFC（BA 9/46）和右侧顶上小叶（BA 7）神经活动增加。对关键交互作用的分析表明，不匹配条件仅导致右侧DLPFC（BA 9/46）的特定激活。研究2使用相同的实验设置，但操纵右手（而不是左手）的视觉反馈，随后证明这种右侧DLPFC激活与所关注的手无关。最后，研究3通过被动移动受试者的手消除了运动意图成分，从而仅产生本体感觉和视觉之间的不匹配。现在右侧前额叶外侧皮质的激活比研究1或2中的更靠腹侧（BA 44/45）。对研究1和3（两者都操纵左手的视觉反馈）的直接比较证实，右侧前额叶外侧腹侧区域主要由感觉系统信号之间的差异激活，而当面对意图和感觉结果之间的冲突时必须维持动作时，右侧前额叶外侧皮质中更靠背侧的区域被激活。
