Speech processing relies on interactions between auditory and motor systems and is asymmetrically organized in the human brain. The left auditory system is specialized for processing of phonemes, whereas the right is specialized for processing of pitch changes in speech affecting prosody. In speakers of tonal languages, however, processing of pitch (i.e., tone) changes that alter word meaning is left-lateralized indicating that linguistic function and language experience shape speech processing asymmetries. Here, we investigated the asymmetry of motor contributions to auditory speech processing in male and female speakers of tonal and non-tonal languages. We temporarily disrupted the right or left speech motor cortex using transcranial magnetic stimulation (TMS) and measured the impact of these disruptions on auditory discrimination (mismatch negativity; MMN) responses to phoneme and tone changes in sequences of syllables using electroencephalography (EEG). We found that the effect of motor disruptions on processing of tone changes differed between language groups: disruption of the right speech motor cortex suppressed responses to tone changes in non-tonal language speakers, whereas disruption of the left speech motor cortex suppressed responses to tone changes in tonal language speakers. In non-tonal language speakers, the effects of disruption of left speech motor cortex on responses to tone changes were inconclusive. For phoneme changes, disruption of left but not right speech motor cortex suppressed responses in both language groups. We conclude that the contributions of the right and left speech motor cortex to auditory speech processing are determined by the functional roles of acoustic cues in the listener's native language.

SIGNIFICANCE STATEMENT The principles underlying hemispheric asymmetries of auditory speech processing remain debated. The asymmetry of processing of speech sounds is affected by low-level acoustic cues, but also by their linguistic function. By combining transcranial magnetic stimulation (TMS) and electroencephalography (EEG), we investigated the asymmetry of motor contributions to auditory speech processing in tonal and non-tonal language speakers. We provide causal evidence that the functional role of the acoustic cues in the listener's native language affects the asymmetry of motor influences on auditory speech discrimination ability [indexed by mismatch negativity (MMN) responses]. Lateralized top-down motor influences can affect asymmetry of speech processing in the auditory system.

语音处理依赖于听觉和运动系统之间的相互作用，并且在人脑中是不对称组织的。左听觉系统专用于处理音素，而右听觉系统专用于处理影响韵律的语音音高变化。但是，在使用口语的人中，音调（即音调）的变化会改变单词的含义，因此在左侧偏左，表示语言功能和语言会影响语音处理的不对称性。在这里，我们调查了男性对语音和非调性语言的听觉语音处理中运动贡献的不对称性。我们使用颅磁刺激（TMS）暂时破坏了右或左语音运动皮层，并使用脑电图（EEG）测量了这些破坏对听觉辨别（失配阴性； MMN）对音素序列中音素变化和音调变化的影响。我们发现，运动中断对语调变化的处理在不同语言组之间是不同的：右语音运动皮层的中断抑制了非调性语言说话者对音调变化的响应，而左语音运动皮层的破坏抑制了对音调变化的响应用音调语言讲。在非调性语言说话者中，左语音运动皮层的中断对音调变化的响应的影响尚无定论。对于音素更改，左但不是右语音运动皮层的破坏抑制了两种语言组的反应。我们得出结论，左右语音运动皮层对听觉语音处理的贡献取决于听觉提示在听众母语中的功能作用。

意义声明关于听觉语音处理的半球不对称性的基本原理仍有争议。语音处理的不对称性受低级声音提示的影响，但也受其语言功能的影响。通过结合经颅磁刺激（TMS）和脑电图（EEG），我们研究了在声调和非声调语言说话者中运动对听觉语音处理的贡献的不对称性。我们提供了因果证据，即听觉提示在听众母语中的功能作用会影响运动对听觉语音辨别能力的影响的不对称性（以失配负（MMN）反应为指标）。自上而下的横向运动影响可能会影响听觉系统中语音处理的不对称性。