Shared control-network recruitment and task-dependent brain-behavior associations in bilingual language and rule...

Bilingual language control is thought to draw on domain-general cognitive control, yet it remains unclear whether cross-task overlap in neural recruitment is accompanied by similar brain-behavior relationships. Previous connectivity studies have typically estimated functional connectivity (FC) across entire tasks or blocks, obscuring network changes specific to switch trials. We combined hierarchical drift-diffusion modeling, regional activation, and beta-series FC in 126 Chinese-English bilinguals (123 with usable fMRI data) who completed language- and rule-switching tasks. Both tasks reduced drift rates and prolonged nondecision times on switch trials. They also recruited a common 28-region switch-sensitive control core and showed increased switch-related FC within this core and between the core and default mode, subcortical, and cerebellar systems. At the individual-difference level, generalized estimating equations revealed task-dependent brain-behavior relationships: core-within and core-subcortical FC were more positively associated with drift-rate switch cost during language switching than during rule switching. Together, the results identify partial overlap in regional recruitment, similarly directed system-level FC changes, and distinct FC-evidence-accumulation relationships across tasks.