Comprehending action words often engages similar brain regions to those involved in perceiving and executing actions. This finding has been interpreted as support for grounding of conceptual processing in motor representations or that conceptual processing involves motor simulation. However, such demonstrations cannot confirm the nature of the mechanism(s) responsible, as word comprehension involves multiple processes (e.g., lexical, semantic, morphological, phonological). In this study, we tested whether this motor cortex engagement instead reflects processing of statistical regularities in sublexical phonological features. Specifically, we measured brain activity in healthy participants using functional magnetic resonance imaging while they performed an auditory lexical decision paradigm involving monosyllabic action words associated with specific effectors (face, arm, and leg). We show that nonwords matched to the action words in terms of their phonotactic probability elicit common patterns of activation. In addition, we show that a measure of the action words' phonological typicality, the extent to which a word's phonology is typical of other words in the grammatical category to which it belongs (i.e., more or less verb-like), is responsible for their activating a significant portion of primary and premotor cortices. These results indicate motor cortex engagement during action word comprehension is more likely to reflect processing of statistical regularities in sublexical phonological features than conceptual processing. We discuss the implications for current neurobiological models of language, all of which implicitly or explicitly assume that the relationship between the sound of a word and its meaning is arbitrary.

理解动作词通常涉及与感知和执行动作的大脑区域相似的大脑区域。这一发现被解释为支持运动表征中概念处理的基础，或者概念处理涉及运动模拟。然而，这样的示范不能证实负责机制的性质，因为单词理解涉及多个过程（例如，词汇、语义、形态、语音）。在这项研究中，我们测试了这种运动皮层的参与是否反映了亚词汇语音特征中统计规律的处理。具体来说，我们使用功能性磁共振成像测量了健康参与者的大脑活动，同时他们执行了听觉词汇决策范式，涉及与特定效应器（面部、手臂和腿）相关的单音节动作词。我们展示了非词与动作词的匹配音序概率引发常见的激活模式。此外，我们表明，对动作词的音韵典型性的衡量，即一个词的音韵在它所属的语法类别中（即，或多或少类似于动词）中的其他词的典型程度，负责它们激活了很大一部分初级和前运动皮质。这些结果表明，动作词理解过程中的运动皮层参与更可能反映亚词汇语音特征中统计规律的处理，而不是概念处理。我们讨论了对当前语言神经生物学模型的影响，所有这些模型都隐含或明确地假设单词的声音与其含义之间的关系是任意的。