Revisiting the Functional Specialization of Left Inferior Frontal Gyrus in Phonological and Semantic Fluency: The Crucial Role of Task Demands and Individual Ability
Revisiting the Functional Specialization of Left Inferior Frontal Gyrus in Phonological and Semantic Fluency: The Crucial Role of Task Demands and Individual Ability
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DOI：
10.1523/jneurosci.3147-12.2013
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发表时间：
2013-05-01
影响因子：
5.3
通讯作者：
Kaller, Christoph P.
中科院分区：
文献类型：
--
作者：
Katzev, Michael;Tuescher, Oliver;Kaller, Christoph P.
尽管有大量的研究，现存的研究结果左额下回（LIFG）在语音和语义流畅性的功能作用仍然存在争议。基于交叉研究比较，最近的一项神经影像学结果的元分析表明，后背侧（布罗德曼区，BA，44）和前腹侧部分（BA 45）的LIFG有助于差异的语音和语义线索的单词检索过程，分别。相反，随后的功能性磁共振成像实验未能验证提出的分离使用内科目设计。特别是，没有证据表明BA 45在语义流畅性中的特定作用，在这里，我们解决了这一明显的争议表明，当考虑到任务要求和个人能力对功能磁共振成像激活模式的影响时，可以解释相互矛盾的发现。通过比较语音与语义流畅性，较高的激活被稳健地观察到BA 44。相反的比较，较高的激活被发现在背BA 45，然而，这是更明显的BA 45的后背部分的低性能的科目，只有在前背部分的BA 45下的控制语义检索的高要求是明显的。因此，我们的研究结果揭示了重要的决定因素，检测功能分离的LIFG在语言流畅性，也有影响的争议性结果在以前的病变研究。此外，背侧BA 45的本分组与解剖学证据很好地对应，表明分为前部（45 A）和后部（45 B），因此可以代表其在人类中的功能意义的证据。
Despite a large body of research, extant findings on the functional role of left inferior frontal gyrus (LIFG) in phonological and semantic fluency are still controversial. Based on cross-study comparisons, a recent meta-analysis of neuroimaging results suggests that posterior-dorsal (Brodmann area, BA, 44) and anterior-ventral parts (BA 45) of LIFG contribute differentially to processes of phonologically and semantically cued word retrieval, respectively. In contrast, a subsequent functional magnetic resonance imaging experiment failed to validate the proposed dissociation using a within-subjects design. In particular, no evidence for a specific role of BA 45 in semantic fluency was found. Here, we resolve this apparent controversy by showing that the conflicting findings can be accounted for when considering the influence of task demands and individual ability on resulting functional magnetic resonance imaging activation patterns. By comparing phonological versus semantic fluency, higher activation was robustly observed in BA 44. For the opposite comparison, higher activation was found in dorsal BA 45; however, this was more pronounced in posterior-dorsal parts of BA 45 for low-performing subjects and was only apparent in anterior-dorsal parts of BA 45 under high demands on controlled semantic retrieval. Our results thus disclose important determinants for detecting a functional segregation of LIFG in verbal fluency that also have implications for the controversial findings in previous lesion studies. Moreover, the present parcellation of dorsal BA 45 corresponds well with anatomical evidence suggesting a subdivision into an anterior (45A) and posterior part (45B) and may therefore represent evidence for its functional significance in humans.