Montreal Neurological Institute, Montréal, Canada.
J Cogn Neurosci. 2009 Dec;21(12):2263-75. doi: 10.1162/jocn.2008.21172.
Although prefrontal cortex is clearly important in executive function, the specific processes carried out by particular regions within human prefrontal cortex remain a matter of debate. A rapidly growing corpus of functional imaging work now implicates various areas within prefrontal cortex in a wide range of "executive" tasks. Loss-of-function studies can help constrain the interpretation of such evidence by testing to what extent particular brain areas are necessary for a given cognitive process. Here we apply a component process analysis to understand prefrontal contributions to the n-back task, a widely used test of working memory, in a cohort of patients with focal prefrontal damage. We investigated letter 2-back task performance in 27 patients with focal damage to various regions within prefrontal cortex, compared to 29 demographically matched control subjects. Both "behavior-defined" approaches, using qualitative lesion analyses and voxel-based lesion-symptom mapping methods, and more conventional "lesion-defined" groupwise comparisons were undertaken to determine the relationships between specific sites of damage within prefrontal cortex and particular aspects of n-back task performance. We confirmed a critical role for left lateral prefrontal cortex in letter 2-back performance. We also identified a critical role for medial prefrontal cortex in this task: Damage to dorsal anterior cingulate cortex and adjacent dorsal fronto-medial cortex led to a pattern of impairment marked by high false alarm rates, distinct from the impairment associated with lateral prefrontal damage. These findings provide converging support for regionally specific models of human prefrontal function.
尽管前额叶皮层在执行功能中显然很重要，但人类前额叶皮层内特定区域执行的具体过程仍然存在争议。现在，大量的功能成像工作表明，前额叶皮层的各个区域都参与了广泛的“执行”任务。通过测试特定脑区对于特定认知过程的必要性，失能研究可以帮助限制对这些证据的解释。在这里，我们应用一个组成过程分析来理解前额叶对 n-back 任务（一种广泛用于测试工作记忆的任务）的贡献，在一组有局灶性前额叶损伤的患者中进行了研究。我们调查了 27 名前额叶不同区域有局灶性损伤的患者和 29 名年龄匹配的对照组在字母 2-back 任务中的表现。使用定性损伤分析和基于体素的损伤-症状映射方法的“行为定义”方法，以及更传统的“损伤定义”组间比较，都被用来确定前额叶内特定损伤部位与 n-back 任务表现的特定方面之间的关系。我们证实了左侧外侧前额叶皮层在字母 2-back 表现中的关键作用。我们还发现了内侧前额叶皮层在这项任务中的关键作用：背侧前扣带皮层和相邻的背侧额-内侧皮层的损伤导致了一种以高假警报率为特征的损伤模式，与外侧前额叶损伤相关的损伤不同。这些发现为人类前额叶功能的区域特异性模型提供了一致的支持。
