Lee Kyoung-Min, Wade Alex R, Lee Byeong-Taek
The Smith-Kettlewell Eye Research Institute, 2318 Fillmore Street, San Francisco, CA 94115, USA.
Neuroimage. 2006 Oct 15;33(1):307-15. doi: 10.1016/j.neuroimage.2006.06.039. Epub 2006 Aug 17.
The time taken to choose a response appropriate for a cue increases with the number of potential response options (Hick's law). We used this temporal constraint of choice behavior in event-related fMRI experiments to identify brain areas carrying out the translation from a cue stimulus to response: Since the process takes longer with more alternatives, the activity of the areas would increase in correlation with the number of alternatives (NA) available at the time of choice decision. During a choice saccade task in which one target is selected among many alternatives based on the color of a cue in the center, the frontal eye fields (FEF) and intraparietal sulcus (IPS) were activated. Within these regions, signals were correlated with NA at the medial part of the FEF and the posterior part of the IPS, but not at the lateral FEF and anterior IPS. This suggests a functional differentiation within each cortical region. Furthermore, given the separate fronto-parietal projections linking sub-regions that are alike in NA-correlation, cognitive steps for choice decision may occur in different networks of the sub-regions: i.e., the stimulus-response translation step in a network of the posterior IPS and medial FEF, and response execution in the anterior IPS/lateral FEF network.
选择与线索相匹配的反应所需的时间会随着潜在反应选项的数量增加而延长（希克定律）。在与事件相关的功能磁共振成像实验中，我们利用这种选择行为的时间限制来识别从线索刺激到反应的转换过程中起作用的脑区：由于可供选择的项目越多，这一过程耗时越长，因此在做出选择决策时，这些脑区的活动会随着可用选项数量（NA）的增加而增强。在一项选择扫视任务中，根据中央线索的颜色从多个备选目标中选择一个目标，结果发现额眼区（FEF）和顶内沟（IPS）被激活。在这些区域内，信号在FEF内侧部分和IPS后部与NA相关，但在FEF外侧部分和IPS前部则不然。这表明每个皮质区域内存在功能分化。此外，鉴于连接NA相关性相似的子区域的额顶叶投射是分开的，选择决策的认知步骤可能发生在不同的子区域网络中：即在后部IPS和内侧FEF网络中进行刺激-反应转换步骤，在前部IPS/外侧FEF网络中进行反应执行。
