Purpose: Congenital amusia is a neurogenetic disorder of musical pitch processing. Its linguistic consequences have been examined separately for speech intonations and lexical tones. However, in a tonal language such as Chinese, the processing of intonations and lexical tones interacts with each other during online speech perception. Whether and how the musical pitch disorder might affect linguistic pitch processing during online speech perception remains unknown.
Method: We investigated this question with intonation (question vs. statement) and lexical tone (rising Tone 2 vs. falling Tone 4) identification tasks using the same set of sentences, comparing behavioral and event-related potential measurements between Mandarin-speaking amusics and matched controls. We specifically focused on the amusics without behavioral lexical tone deficits (the majority, i.e., pure amusics).
Results: Results showed that, despite relative to normal performance when tested in word lexical tone test, pure amusics demonstrated inferior recognition than controls during sentence tone and intonation identification. Compared to controls, pure amusics had larger N400 amplitudes in question stimuli during tone task and smaller P600 amplitudes in intonation task.
Conclusion: These data indicate that musical pitch disorder affects both tone and intonation processing during sentence processing even for pure amusics, whose lexical tone processing was intact when tested with words.