One of the oldest questions in cognitive science is whether cognitive operations are modular or distributed across domains. We propose that fMRI has made a unique contribution to this question by elucidating the nature of structure-function relations. We focus our discussion on language, which is the classic domain for arguments in favor of domain specificity and a fixed neural architecture. We argue that fMRI has provided evidence for the idea that there is a dynamic functional architecture, rather than a fixed neural architecture, that emerges across the lifespan, pursuant to injury and in response to language experience. We use empirical examples to highlight how fMRI has helped restructure theory by shedding light on how functionally distinct modular components of the grammar can recruit some of the same neural regions, how areas considered to be domain-specific may be recruited in a domain-general fashion, and how language network specialization and left lateralization dynamically emerge in response to experience. fMRI provides a window into neural plasticity and dynamic functional organization not easily afforded by behavior alone.
