An ER-fMRI investigation of morphological inflection in German reveals that the brain makes a distinction between regular and irregular forms

The hypothesis that morphological processing is supported by a mental dictionary of stored entries plus a set of mental computations based on rules is examined using event-related fMRI. If a rules-plus-memory model (Pinker, 1999) reflects the actual organization of the language faculty, two distinct patterns of brain activation should be observed for production of German irregular and regular noun and verb inflections. If a connectionist alternative to the rules-and-memory model (Rumelhart & McClelland, 1986, and many others since), which seeks to explain the production of both irregular and regular forms within a single associative memory mechanism, is correct, there should be no neural differentiation between German regular and irregular inflection. The results we report support the existence of substantially differing patterns of activation for regulars vs. irregulars, an outcome that is consistent with the two-component rules-plus-memory account.