Shared and distinct neural correlates of first and second language morphological processing in bilingual brain.

While morphology constitutes a crucial component of the human language system, the neural bases of morphological processing in the human brain remains to be elucidated. The current study aims at exploring the extent to which the second language (L2) morphological processing would resemble or differ from that of their first language (L1) in adult Chinese-English bilinguals. Bilingual participants were asked to complete a morphological priming lexical decision task drawing on derivational morphology, which is present for both Chinese and English, when their electrophysiological and optical responses were recorded concurrently. Functional near-infrared spectroscopy (fNIRS) revealed a neural dissociation between morphological and semantic priming effects in the left fronto-temporal network, while L1 Chinese engaged enhanced activation in the left prefrontal cortex for morphological parsing relative to L2 English. In the early stage of lexical processing, cross-language morphological processing manifested a difference in degree, not in kind, as revealed by the early left anterior negativity (ELAN) effect. In addition, L1 and L2 shared both early and late structural parsing processes (P250 and 300 ~ 500 ms negativity, respectively). Therefore, the current results support a unified competition model for bilingual development, where bilinguals would primarily employ L1 neural resources for L2 morphological representation and processing.