Neural oscillation to Mandarin lexical tone processing in bilingual children: A developmental study

Tonal language experience is associated with structural and functional characteristics in the brain that underlie facilitated pitch perception. However, it is less understood what the developmental trajectory is for lexical tone processing at the cortical level, especially in bilingual children. In the present research, we investigated these developmental changes in terms of neuronal oscillations in response to Mandarin lexical tone contrasts. We measured lexical tone processing in bilingual English-Mandarin learning children and bilingual English-Mandarin young adults. Event-related brain potentials (ERPs) were recorded in an oddball paradigm with two tonal contrasts: one with a small acoustical difference, and one with a larger acoustical difference. We then analyzed the phase locking and amplitude modulation of ongoing oscillations in theta (4–8 Hz), alpha (8–14 Hz), and beta (14–30 Hz) bands to two types of lexical tone changes. Preliminary results suggest developmental changes were associated with strengthened phase locking of neural oscillations to both small and large acoustical contrasts, while stronger phase locking and higher power was observed in the larger acoustical contrast. Beyond this, the theta, alpha, and beta bands demonstrated different sensitivities to developmental changes. Such findings further our understanding of bilingual lexical tone development at the cortical level.