Context-dependent effects of morphosyntax processing in Turkish–Persian bilinguals: Electrophysiological and neuroanatomic correlates

Aims and objectives: Morphosyntax processing is related to the P600 event-related potentials (ERPs) component and blood-oxygen-level dependent (BOLD) activation of the Pars opercularis (PO). First, this paper aims to investigate the relation of these variables across individuals. Second, we consider the role of context in morphosyntactic processing. Design/methodology: Highly proficient Turkish–Persian bilinguals ( N = 33) made morphosyntactic judgments on sentences. In a monolingual context, only L2 sentences (Persian) were presented, and the electroencephalography (EEG) was recorded. In a bilingual context, Persian and Turkish sentences alternated, and functional magnetic resonance imaging (fMRI) was measured. Data and analysis: The EEG and fMRI data were taken from separately published experiments on the same participants. Here, we correlated amplitudes of EEG-derived ERP components and the number of activated voxels in fMRI in designated brain regions because both parameters are proportionally attuned to the number of activated neurons. Findings/conclusions: Morphosyntactic violations in a Persian monolingual context yielded a P600 component in the ERP. In L1, morphosyntactic violations increased BOLD activation in the left PO and in L2 they activated the posterior superior temporal gyrus (pSTG). The P600 amplitude correlated only with BOLD activity in the left PO for L1. These results first support a critical role of the PO in generating the P600; second, the findings are context-specific and are most pronounced for the presumed base languages in different contexts (i.e., L2 in monolingual and L1 in bilingual contexts). These results are consistent with predictions of the adaptive control theory. Originality: This study contributes to the rarely investigated interface between ERPs and fMRI in bilingual speakers during morphosyntactic processing. The results offer novel insights into language context effects. Significance/implications: Our findings highlight the importance of cross-modality neuroimaging in bilinguals and language processing in both monolingual and bilingual contexts.