Gabrieli J D, Poldrack R A, Desmond J E
Department of Psychology, Stanford University, Stanford, CA 94305, USA.
Proc Natl Acad Sci U S A. 1998 Feb 3;95(3):906-13. doi: 10.1073/pnas.95.3.906.
This article reviews attempts to characterize the mental operations mediated by left inferior prefrontal cortex, especially the anterior and inferior portion of the gyrus, with the functional neuroimaging techniques of positron emission tomography and functional magnetic resonance imaging. Activations in this region occur during semantic, relative to nonsemantic, tasks for the generation of words to semantic cues or the classification of words or pictures into semantic categories. This activation appears in the right prefrontal cortex of people known to be atypically right-hemisphere dominant for language. In this region, activations are associated with meaningful encoding that leads to superior explicit memory for stimuli and deactivations with implicit semantic memory (repetition priming) for words and pictures. New findings are reported showing that patients with global amnesia show deactivations in the same region associated with repetition priming, that activation in this region reflects selection of a response from among numerous relative to few alternatives, and that activations in a portion of this region are associated specifically with semantic relative to phonological processing. It is hypothesized that activations in left inferior prefrontal cortex reflect a domain-specific semantic working memory capacity that is invoked more for semantic than nonsemantic analyses regardless of stimulus modality, more for initial than for repeated semantic analysis of a word or picture, more when a response must be selected from among many than few legitimate alternatives, and that yields superior later explicit memory for experiences.
本文回顾了利用正电子发射断层扫描和功能磁共振成像等功能神经影像学技术，对左侧前额叶下回（尤其是脑回的前部和下部）所介导的心理操作进行特征描述的尝试。在语义任务（相对于非语义任务）期间，即根据语义线索生成单词或将单词或图片分类到语义类别时，该区域会出现激活。在已知语言方面非典型地以右侧半球为主导的人群中，这种激活出现在右侧前额叶皮质。在该区域，激活与有意义的编码相关，这种编码会导致对刺激的更好的外显记忆，而失活与对单词和图片的内隐语义记忆（重复启动）相关。报告了新的研究结果，表明全面性遗忘症患者在与重复启动相关的同一区域出现失活，该区域的激活反映了从众多选项中相对于少数选项进行反应的选择，并且该区域的一部分激活具体与语义处理而非语音处理相关。据推测，左侧前额叶下回的激活反映了一种领域特异性的语义工作记忆能力，无论刺激模态如何，这种能力在语义分析而非非语义分析中被调用得更多，在对单词或图片的初始语义分析而非重复语义分析中被调用得更多，在必须从众多而非少数合理选项中选择反应时被调用得更多，并且会为后续经历产生更好的外显记忆。
