title: Distinguishable neural correlates of verbs and nouns: a MEG study on homonyms.
abstract: The dissociability of nouns and verbs and of their morphosyntactic operations has been firmly established by lesion data. However, the hypothesis that they are processed by distinct neural substrates is inconsistently supported by neuroimaging studies. We tackled this issue in a silent reading experiment during MEG. Participants silently read noun/verb homonyms in minimal syntactic context: article-noun (NPs), pronoun-verb (VPs) (e.g., il ballo/i balli, the dance/the dances; io ballo/tu balli, I dance/you dance). Homonyms allow to rule out prelexical or postlexical nuisance factors-they are orthographically and phonologically identical, but serve different grammatical functions depending on context. Under these experimental conditions, different activity to nouns and verbs can be confidently attributed to representational/processing distinctions. At the sensor level, three components of event-related magnetic fields were observed for the function word and four for the content word, but Global Field Power (GFP) analysis only showed differences between VPs and NPs at several but very short time windows. By contrast, source level analysis based on Minimum Norm Estimates (MNE) yielded significantly greater activity for VPs in left frontal areas and in a left frontoparietal network at late time windows (380-397 and 393-409 ms). These results are fully consistent with lesion data, and show that verbs and nouns are processed differently in the brain. Frontal and parietal activation to verbs might correspond to morphosyntactic processes and to working memory recruitment (or thematic role assignment), respectively. Findings are consistent with the view that nouns and verbs and their morphosyntactic operations involve at least partially distinct neural substrates. However, they do not entirely rule out that nouns and verbs are processed in a shared neural substrate, and that differences result from greater complexity of verbal morphosyntax.
authors.affiliation: CIMeC, Center for Mind/Brain Sciences, University of Trento, Via delle Regole 101, 38100 Trento, Italy.
authors.forename: Styliani
authors.initials: S
authors.lastname: Tsigka
authors.affiliation: CIMeC, Center for Mind/Brain Sciences, University of Trento, Via delle Regole 101, 38100 Trento, Italy.
authors.forename: Christos
authors.initials: C
authors.lastname: Papadelis
authors.affiliation: CIMeC, Center for Mind/Brain Sciences, University of Trento, Via delle Regole 101, 38100 Trento, Italy; MEG-Center, University of Tübingen, Otfried-Müller-Str. 47, 72076 Tübingen, Germany; DiPSCo, Corso Bettini 31, 38068 Rovereto, Italy.
authors.forename: Christoph
authors.initials: C
authors.lastname: Braun
authors.affiliation: CIMeC, Center for Mind/Brain Sciences, University of Trento, Via delle Regole 101, 38100 Trento, Italy; CeRiN, Center for Neurocognitive Rehabilitation, CIMeC, Center for Mind/Brain Sciences, University of Trento, Via Matteo del Ben, 5/b, 38068 Rovereto, TN, Italy. Electronic address: gabriele.miceli@unitn.it.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Miceli
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008037:Linguistics; D008279:Magnetic Resonance Imaging; D008297:Male; D011932:Reading; D012660:Semantics; D013997:Time Factors; D014825:Vocabulary; D055815:Young Adult
keywords: Left inferior; Magnetoencephalography; Morphosyntactic processing; Noun processing; Posterior parietal cortex; Prefrontal cortex; Thematic role assignment; Verb processing; Verbal working memory