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The present electrophysiological study investigated irregular versus regular verb form processing in Swedish during reading. In line with previous results from other languages, overregularized verbs, i.e. incorrect irregular stem + regular past tense suffix combinations (e.g. * stjäl + de 'steal + past tense'), elicited a left-lateralized negativity (LAN) relative to correct irregulars (stal 'stole'), suggesting rule-based decomposition of regularly inflected words. Lack of a similar effect for misapplication of the irregular stem formation pattern on regular verbs (e.g. * löft 'lifted' instead of lyfte) suggests the involvement of different processing mechanisms, possibly whole word access, for irregular items, at least to some degree. A P600 showing reprocessing was seen for all incorrect forms. The results add cross-linguistic support for morphological decomposition in the verbal inflection of a language where results from previous neurolinguistic studies of nominal inflection have only suggested the use of full-form access to words. • ERPs of both overregularized and irregularized verbs in Swedish were recorded. • LAN obtained for overregularized verbs suggests rule-based decomposition. • Irregularized verbs elicited only a P600 relative to the correct variant. [ABSTRACT FROM AUTHOR]

Previous studies on the neuro-cognition of language have provided a strong case for systematic inter-individual variability in event-related potentials (ERPs) evoked during language processing. In the present study, we aimed at extending this evidence to the processing of morphologically complex words. We focused on German plural forms and tested two types of morphological violations: overapplications of regular plural morphemes ('regularizations') and of irregular plural morphemes ('irregularizations'). The group-level results showed a biphasic LAN-P600 response for regularizations, and a P600 for irregularizations. In line with previous reports, our analyses of inter-individual variability suggested that biphasic responses consisting of a negativity followed by a positivity are unlikely to exist at the individual level. Importantly, when analyzing the scalp distribution of ERPs elicited in participants supposed to show negativity-dominant responses, we found this to vary as a function of the type of morphological form: regularizations elicited a left-hemisphere response (LAN), while irregularizations a more widespread negativity (N400). Our results are consistent with dual-route accounts of morphological processing that distinguish between rule-based processing for regular inflection and memory retrieval for irregular inflection. At a more general level, our study shows that complementing group-level results with analyses of inter-individual variability can crucially contribute to a more detailed understanding of brain signatures of language. • Overapplications of regular plural forms elicited a LAN-P600 response at group-level. • Overapplications of irregular plural forms elicited a P600 response at group-level. • Some individuals showed a negativity-dominant, others a positivity-dominant response. • Negativity-dominant individuals showed a lateralized negativity with regularizations. • Analyses of inter-individual variability help to better understand ERP components. [ABSTRACT FROM AUTHOR]

Consensus recommendations for three variants of primary progressive aphasia (PPA), the non-fluent/agrammatic, logopenic and semantic variants, were published in 2011 [Gorno-Tempini et al., 2011]. These recommendations describe the most characteristic language impairments for each variant. However, studies using these criteria in larger groups of patients revealed serious limitations concerning their application. Some of these limitations are related to imprecisions in the description of language features, especially for grammatical features. The aim of this review was to examine studies of inflectional morphology in three variants of PPA and in the disease that is the most relevant for differential diagnosis, namely Alzheimer's disease. MedLine, CINAHL and PsycINFO electronic databases were searched to retrieve all relevant peer-reviewed articles published in English language journals. Despite the focus that has been placed on agrammatism by the consensus recommendations, the studies reviewed do not systematically report impairments of inflectional morphology in the non-fluent/agrammatic variant. Studies also show that some individuals with the logopenic variant present with substantial inflection impairments. Contrary to expectations, some studies reveal the presence of morphological difficulties in the semantic variant. These difficulties concern mostly the production of irregular, low-frequency verbs while regular verbs are spared. Similar difficulties are also reported in studies of people with Alzheimer's disease. Overall, the results show the need to more clearly define the criteria related to grammar and morphology and to better characterise impairment severity. Future research on primary progressive aphasia and other degenerative diseases with language impairments will help refine our expectations regarding language features that characterise each profile. [ABSTRACT FROM AUTHOR]