Spatiotemporal dynamics of the processing of spoken derived and inflected words
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AbstractThe present study examined the time-course and the neural sources of recognition of spoken morphologically complex words. Ten participants listened to derived, inflected, and monomorphemic Finnish words and judged their acceptability while the electroencephalography (EEG) and magnetoencephalography (MEG) responses were simultaneously recorded. The EEG and MEG responses were time-locked to the critical point (suffix onset for the complex words and uniqueness point for the monomorphemic words). The event-related potential (ERP) results showed that inflected words elicited a larger left-lateralized negativity than derived and monomorphemic words ~200 ms after the critical point, but no differences were observed between derived and monomorphemic words. Equivalent current dipole (ECD) modeling of the MEG responses showed that this negativity was explained by two bilateral sources in the temporal cortex, as inflected words showed larger source amplitudes than derived words. In addition to amplitude differences, the dipole locations differed significantly between derived and inflected words. Moreover, derived words elicited stronger source amplitudes than inflected and monomorphemic words in the right superior temporal area ~100 ms after the critical point. Our findings provide evidence for distinct cortical processing of spoken inflected and derived words. The results support models of morphological processing stating that during the recognition of inflected words, the constituent morphemes are accessed separately. The left-lateralization of the ERP responses suggests that the stem and suffix combination undergoes morphosyntactic licensing. With regard to derived words, stem and suffix morphemes might be at least initially activated along with the whole word representation. Funding: Supported by Academy of Finland.