Left hemisphere (LH) specialization for language has been a key example of functional lateralization. However, the role of the right hemisphere (RH) and how the two hemispheres work together to process language remain poorly understood. In this talk, I will focus on the left-lateralized network for syntactic category processing, and I will present a series of studies we conducted to investigate how this brain asymmetry is modulated by one’s inter-hemispheric communication abilities and whether the modulating factors and the degree of asymmetry change with aging. We used the visual half-field presentation paradigm to assess event-related potential (ERP) responses to syntactic category violations preferentially elicited by the two hemispheres. Additional Diffusion Tensor Imaging (DTI) data and behavioral measures for inter-hemispheric coordination and inhibition were collected from the same individuals. We found that the left-lateralized grammaticality effects in younger adults were predicted by stronger integrity of the superior longitudinal fasciculus (SLF) and genu of the corpus callosum. In addition, younger adults less effective in coordinating information across hemispheres showed more left-lateralized P600 effects. By contrast, bilateral P600 responses were found in older adults. These additional responses were accompanied by lower sensitivity in grammatical judgment. Older adults more susceptible to interference from the contralateral hemisphere showed more bilateralP600s. Together, these studies demonstrated that, similar to the trend previously observed in other cognitive abilities, the degree of lateralization for syntactic category processing is also reduced with aging. The age-related reorganization in this case, however, was not compensatory. Furthermore, these findings suggest that functional brain asymmetry in syntactic category processing may be driven by multiple forces that are weighted differently across the lifespan.