Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.05.137067v1?rss=1 Authors: Tang, D.-l., Mottonen, R., Asaridou, S. S., Watkins, K. E. Abstract: 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 that affect prosody. In speakers of tonal languages, however, processing of pitch (i.e., tone) changes that alter word meaning is left-lateralized. This indicates that linguistic function and language experience shape auditory speech processing asymmetries; their effect on auditory-motor speech processing remains unknown, however. Here, we investigated the asymmetry of motor contributions to auditory speech processing in speakers of tonal and non-tonal languages. We temporarily disrupted the left or right speech motor cortex using repetitive transcranial magnetic stimulation (rTMS) and measured the impact of these disruptions on auditory processing of phoneme and tone changes in sequences of syllables using electroencephalography (EEG). We found that disruption of the speech motor cortex in the left, but not the right hemisphere, impaired processing of phoneme changes in both language groups equally. In contrast, the effect of motor disruptions on processing of tone changes differed in tonal and non-tonal language groups: disruption of the left speech motor cortex significantly impaired processing of tone changes in tonal language speakers, whereas disruption of the right speech motor cortex modulated processing of tone changes in non-tonal speakers. We conclude that the contribution of the left and right speech motor cortex to auditory speech processing is determined by the functional role of the acoustic cues in the listener's native language. Copy rights belong to original authors. Visit the link for more info