Sustained Responses as Neurophysiological Parameter for the Assessment of Processing of Tonal Languages

Abstract

To understand speech processing is one of the ultimate goals of investigations of sound processing in the auditory cortex. Chinese tones are the perfect object for this kind of investigation because they are very short but still contain complex linguistic information. In tonal languages such as Mandarin Chinese, pitch contours discriminate lexical meaning at a systematic level, which is not the case in non-tonal languages such as German. It is still unclear how such differences in phonological systems are reflected at the cortical level. Using magnetoencephalography I investigated the sustained field (SF) evoked in native Chinese and native German speakers. Natural speech stimuli evoked significantly larger SF for the Chinese than for the German group, whereas for a musical tone there was no significant difference between both group. The SF for Chinese subjects were larger when evoked by meaningful syllables as compared to meaningless ones, but there was no significant difference in the SF evoked when vowels were part of the Chinese phonological system or not. These findings suggest that the SF generated in the auditory cortex represents a relevant neurophysiological parameter for the assessment of language-related processes.