Issues in Neurolinguistic Studies of Morphology

Research in neurolinguistics examines how language is organized and processed in the human brain. The findings from neurolinguistic studies on language can inform our understanding of the basic ingredients of language and the operations they undergo. In the domain of the lexicon, a major debate concerns whether and to what extent the morpheme serves as a basic unit of linguistic representation, and in turn whether and under what circumstances the processing of morphologically complex words involves operations that identify, activate, and combine morpheme-level representations during lexical processing. Alternative models positing some role for morphemes argue that complex words are processed via morphological decomposition and composition in the general case (full-decomposition models), or only under certain circumstances (dual-route models), while other models do not posit a role for morphemes (non-morphological models), instead arguing that complex words are related to their constituents not via morphological identity, but either via associations among whole-word representations or via similarity in formal and/or semantic features. Two main approaches to investigating the role of morphemes from a neurolinguistic perspective are neuropsychology, in which complex word processing is typically investigated in cases of brain insult or neurodegenerative disease, and brain imaging, which makes it possible to examine the temporal dynamics and neuroanatomy of complex word processing as it occurs in the brain. Neurolinguistic studies on morphology have examined whether the processing of complex words involves brain mechanisms that rapidly segment the input into potential morpheme constituents, how and under what circumstances morpheme representations are accessed from the lexicon, and how morphemes are combined to form complex morphosyntactic and morpho-semantic representations. Findings from this literature broadly converge in suggesting a role for morphemes in complex word processing, although questions remain regarding the precise time course by which morphemes are activated, the extent to which morpheme access is constrained by semantic or form properties, as well as regarding the brain mechanisms by which morphemes are ultimately combined into complex representations.