Priming production: Neural evidence for enhanced automatic semantic activity preceding language production in schizophrenia

Abstract

IntroductionLexico-semantic disturbances are considered central to schizophrenia. Clinically, their clearest manifestation is in language production. However, most studies probing their underlying mechanisms have used comprehension or categorization tasks. Here, we probed automatic semantic activity prior to language production in schizophrenia using event-related potentials (ERPs).Methods19 people with schizophrenia and 16 demographically-matched healthy controls named target pictures that were very quickly preceded by masked prime words. To probe automatic semantic activity prior to production, we measured the N400 ERP component evoked by these targets. To determine the origin of any automatic semantic abnormalities, we manipulated the type of relationship between prime and target such that they overlapped in (a) their semantic features (semantically related, e.g. “cake” preceding a < picture of a pie >, (b) their initial phonemes (phonemically related, e.g. “stomach” preceding a < picture of a starfish >), or (c) both their semantic features and their orthographic/phonological word form (identity related, e.g. “socks” preceding a < picture of socks >). For each of these three types of relationship, the same targets were paired with unrelated prime words (counterbalanced across lists). We contrasted ERPs and naming times to each type of related target with its corresponding unrelated target.ResultsPeople with schizophrenia showed abnormal N400 modulation prior to naming identity related (versus unrelated) targets: whereas healthy control participants produced a smaller amplitude N400 to identity related than unrelated targets, patients showed the opposite pattern, producing a larger N400 to identity related than unrelated targets. This abnormality was specific to the identity related targets. Just like healthy control participants, people with schizophrenia produced a smaller N400 to semantically related than to unrelated targets, and showed no difference in the N400 evoked by phonemically related and unrelated targets. There were no differences between the two groups in the pattern of naming times across conditions.ConclusionPeople with schizophrenia can show abnormal neural activity associated with automatic semantic processing prior to language production. The specificity of this abnormality to the identity related targets suggests that that, rather than arising from abnormalities of either semantic features or lexical form alone, it may stem from disruptions of mappings (connections) between the meaning of words and their form.

Language disintegration under conditions of severe formal thought disorder

“…Recent work in computational linguistics have suggested considerable potential for language as a biomarker in schizophrenia, as automated linguistic measures can predict symptoms of schizophrenia including FTD (Elvevåg et al 2010;Bedi et al 2015;Holshausen et al 2014). Experimental psycholinguistic studies have also revealed numerous language processing anomalies in schizophrenia, largely in comprehension/perception (Titone et al 2007;Kuperberg 2010;Kuperberg et al 2017; but see Kuperberg et al 2018, for a recent study of semantic priming in a naming task), and in part specific to FTD (Kuperberg et al 1998).…”

Lexical and semantic training to acquire words in a foreign language: An electrophysiological study

“…For ERP data analysis, a representative sub-array of nine channels was used (Blackford, Holcomb, Grainger & Kuperberg, 2012; Chauncey, Grainger & Holcomb, 2008; Grainger, Kiyonaga & Holcomb, 2006; Kuperberg, Delaney-Busch, Fanucci & Blackford, 2018). As Blackford and colleagues (2012) mentioned, following this design, a single analysis of variance (ANOVA) can be used for each time window analysis; and, hence, this electrode selection is a good meeting point between the use of a simple design and the correct description of the overall distribution of the effects.…”

Multimodal neuroimaging evidence for looser lexico-semantic networks in schizophrenia:Evidence from masked indirect semantic priming

“…As outlined in the Introduction, an enhanced automatic indirect priming effect in schizophrenia could, in theory, result either from an unconstrained (or disinhibited) spread of activity across semantic memory (e.g. Manschreck et al, 1988), or from noisier lexical representations --that is, looser (less finely-tuned) mappings/connections between representations of word-form and semantic features (Brown and Kuperberg, 2015;Kuperberg et al, 2018a), see Fig. 1.…”

“…1B. It holds that these formmeaning (lexical) mappings are weaker and less finely-tuned in people with schizophrenia than in healthy adults (Brown and Kuperberg, 2015;Kuperberg et al, 2018a). For example, in healthy controls, the lexical representation, BELL, encodes tight mappings between the semantic features, < bell > , and the specific word-form, b-e-l-l.…”