Figure 4.

Language-dependent neural tuning supports the categorization of lexical tone. (a) Four distinct tone categories (high, rising, dipping, and falling) were included in this experiment, in which native Mandarin and English speakers were presented with naturally produced Mandarin speech (Li et al. 2021). This panel shows an example Mandarin sentence with the extracted pitch contour overlaid on a spectrogram representation of the speech sequence (color of the contour indicates corresponding tone category). (b) Single electrode responses to relative pitch height can be categorized based on the positive or negative relationship between relative pitch height (x-axis) and cortical response amplitude (y-axis). (c) Analysis of electrode pitch encoding reveals a balanced distribution of STG electrodes in native Mandarin speakers that are either negatively or positively tuned to relative pitch (−, +). In native English speakers, STG electrodes show primarily positive relative pitch tuning (+). Whereas lexical tone category can be decoded from the population-level neural response in native Mandarin speakers, the decodability of lexical tone is significantly reduced in English native speakers. These results indicate that the distribution of STG pitch tuning is biased depending on the language experience of the listener.