Access to lexical meaning in pitch-flattened Chinese sentences: An fMRI study

Chinese is a tonal language in which variation in pitch is used to distinguish word meanings. Thus, in order to understand a word, listeners have to extract the pitch patterns in addition to its phonemes. Can the correct word meaning still be accessed in sentence contexts if pitch patterns of words are altered? If so, how is this accomplished? The present study attempts to address such questions with event-related functional magnetic resonance imaging (fMRI). Native speakers of Mandarin Chinese listened to normal and pitch-flattened (monotone) speech inside the scanner. The behavioral results indicated that they rated monotone sentences as intelligible as normal sentences, and performed equally well in a dictation test on the two types of sentences. The fMRI results showed that both types of sentences elicited similar activation in the left insular, middle and inferior temporal gyri, but the monotone sentences elicited greater activation in the left planum temporale (PT) compared with normal sentences. These results demonstrate that lexical meaning can still be accessed in pitch-flattened Chinese sentences, and that this process is realized by automatic recovery of the phonological representations of lexical tones from the altered tonal patterns. Our findings suggest that the details of spoken pitch patterns are not essential for adequate lexical-semantic processing during sentence comprehension even in tonal languages like Mandarin Chinese, given that listeners can automatically use additional neural and cognitive resources to recover distorted tonal patterns in sentences.