Dixon Matthew L, Fox Kieran C R, Christoff Kalina
Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, BC, Canada V6T 1Z4.
Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, BC, Canada V6T 1Z4; Brain Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
Brain Res. 2014 Jul 14;1572:26-39. doi: 10.1016/j.brainres.2014.05.012. Epub 2014 May 16.
The functional organization of brain areas supporting goal-directed behavior is debated. Some accounts suggest a rostro-caudal organization, while others suggest a broad recruitment as part of a multiple demand network. We used fMRI and an anatomical region of interest (ROI) approach to test which account better characterizes the organization of key brain areas related to goal-directed behavior: the lateral prefrontal cortex (LPFC), medial prefrontal cortex (MPFC), cingulate cortex, and insula. Subjects performed a cognitive control task with distinct trial events corresponding to rule representation, rule maintenance, action execution, and monitoring progress towards an overarching motivational goal. The use of ROIs allowed us to look for evidence of rostro-caudal gradients during each event separately. Our results provide strong evidence for rostro-caudal gradients in all regions. During the action execution period, activation was robust in caudal ROIs and decreased linearly moving to rostral ROIs in the LPFC, cingulate cortex, and MPFC. Conversely, during the goal monitoring period, activation was weak in caudal ROIs and increased linearly moving to the rostral ROIs in the aforementioned regions. The insula exhibited the reverse pattern. These findings provide evidence for rostro-caudal organization in multiple regions within the same study. More importantly, they demonstrate that rostro-caudal gradients can be observed during individual trial events, ruling out confounding factors such as task difficulty.
支持目标导向行为的脑区功能组织存在争议。一些观点认为存在一种前后组织方式，而另一些观点则认为作为多需求网络的一部分会有广泛的脑区参与。我们使用功能磁共振成像（fMRI）和解剖学感兴趣区域（ROI）方法来测试哪种观点能更好地描述与目标导向行为相关的关键脑区的组织方式：外侧前额叶皮层（LPFC）、内侧前额叶皮层（MPFC）、扣带回皮层和脑岛。受试者执行一项认知控制任务，其中不同的试验事件对应规则表征、规则维持、动作执行以及朝着总体动机目标监测进展情况。使用感兴趣区域使我们能够分别在每个事件期间寻找前后梯度的证据。我们的结果为所有区域存在前后梯度提供了有力证据。在动作执行期间，尾侧感兴趣区域的激活很强，并且在LPFC、扣带回皮层和MPFC中向头侧感兴趣区域线性减少。相反，在目标监测期间，尾侧感兴趣区域的激活较弱，并且在上述区域中向头侧感兴趣区域线性增加。脑岛呈现相反的模式。这些发现为同一研究中的多个区域存在前后组织方式提供了证据。更重要的是，它们表明在单个试验事件期间可以观察到前后梯度，排除了诸如任务难度等混杂因素。
