Most neuroimaging studies examining verb morphology have focused on verb tense, with fewer examining agreement morphology, and no previous fMRI studies have investigated distinctions between past and present tense inflection. However, models of language representation and processing suggest differences in where these inflections are instantiated in the phrase structure as well as differences in the linguistic functions they serve, suggesting unique neural networks for these forms. In addition, results of available neuroimaging studies of grammatical morphology vary considerably due to methodological differences. Some studies have used overt production tasks, whereas others have used covert tasks. In the present study we examined brain activation associated with past tense and present tense/agreement morphology under overt and covert production conditions in 13 healthy adults using an event-related functional magnetic resonance imaging (fMRI) design. Production of verbs inflected for past tense (V + -ed) and present tense/agreement (V -s) was elicited using temporal adverbs (i.e. Yesterday, Nowadays). Results showed that in healthy adults inflecting both past tense and agreement morphology (compared to a verb stem production condition) recruited not only left inferior frontal structures, but also motor and premotor cortices, and posterior parietal regions. Activation also was observed in the basal ganglia, thalamus, and the cingulate gyrus. Past tense and present tense/agreement recruited partially overlapping tissue in these regions, with distinctions observed for the two forms in frontal and parietal brain areas. We also found that activation varied with task demands, with more extensive frontal activation noted in the overt compared to the covert verb inflection task. These results are consistent with the hypothesis that the neural signatures for verb inflection differ from that for verb stems alone and involve a distributed frontal and parietal network of brain regions. Further, the neural tissue recruited for instantiation of past tense versus present tense/agreement morphology is distinct, supporting linguistic theories that differentiate the two forms.

中文翻译：

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时态和一致性形态的隐性和显性产生的神经相关性：来自 fMRI 的证据

大多数检查动词形态的神经影像学研究都集中在动词时态，较少检查一致形态，而且以前的 fMRI 研究没有调查过去和现在时态变化之间的区别。然而，语言表示和处理模型表明，这些屈折在短语结构中的实例化位置存在差异，以及它们所服务的语言功能存在差异，这表明这些形式具有独特的神经网络。此外，由于方法学上的差异，现有的语法形态学神经影像学研究的结果差异很大。一些研究使用了公开的生产任务，而另一些研究使用了隐蔽的任务。在本研究中，我们使用事件相关功能磁共振成像 (fMRI) 设计检查了 13 名健康成年人在公开和隐蔽生产条件下与过去时和现在时/一致形态相关的大脑激活。过去时 (V + -ed) 和现在时/同意 (V -s) 屈折动词的产生是使用时间副词（即昨天、今天）引出的。结果表明，在同时使用过去时和一致形态（与动词词干产生条件相比）的健康成年人中，不仅招募左下额叶结构，还招募运动和前运动皮质以及后顶叶区域。在基底神经节、丘脑和扣带回中也观察到了激活。过去时和现在时/协议在这些区域招募部分重叠的组织，在额叶和顶叶脑区观察到两种形式的区别。我们还发现激活随任务需求而变化，与隐性动词屈折任务相比，明显的正面激活更广泛。这些结果与以下假设一致，即动词屈折的神经特征不同于单独的动词词干，并且涉及大脑区域的分布式额叶和顶叶网络。此外，用于实例化过去时与现在时/一致形态的神经组织是不同的，支持区分这两种形式的语言学理论。与隐性动词屈折任务相比，在显性中注意到更广泛的正面激活。这些结果与以下假设一致，即动词屈折的神经特征不同于单独的动词词干，并且涉及大脑区域的分布式额叶和顶叶网络。此外，用于实例化过去时与现在时/一致形态的神经组织是不同的，支持区分这两种形式的语言学理论。与隐性动词屈折任务相比，在显性中注意到更广泛的正面激活。这些结果与以下假设一致，即动词屈折的神经特征不同于单独的动词词干，并且涉及大脑区域的分布式额叶和顶叶网络。此外，用于实例化过去时与现在时/一致形态的神经组织是不同的，支持区分这两种形式的语言学理论。