Slow and steady: sustained effects of lexico-semantic associations can mediate referential impairments in schizophrenia

Abstract

The present study investigated the contribution of lexico-semantic associations to impairments in establishing reference in schizophrenia. We examined event-related potentials as schizophrenia patients and healthy demographically-matched controls read five-sentence scenarios. Sentence 4 introduced a noun which referred back to three possible referents introduced in sentences 1–3. These referents were contextually appropriate, contextually inappropriate but lexico-semantically associated, and contextually inappropriate and lexico-semantically non-associated. In order to determine whether participants had correctly linked the anaphor to its referents, the final sentence reintroduced each referent and participants indicated whether the last two sentences referred to the same entity. Results indicated that between 300–400msec, patients, like healthy controls, used discourse context to link the noun with its preceding referent. However, between 400–500msec, neural activity in patients was modulated only by lexico-semantic associations rather than discourse context. Moreover, patients were also more likely than controls to incorrectly link the noun with contextually-inappropriate, but lexico-semantically associated, referents. Results suggest that at least some types of referential impairments may be driven by sustained activation of contextually inappropriate lexico-semantic associations.

Disordered semantic activation in disorganized discourse in schizophrenia: a new pragma‐linguistic tool for structure and meaning reconstruction

“…The second highly unintelligible passage with its derailment (Passage 2) was shown to be due to overreliance on semantic associations, which eventually blurred the construction of a coherent global picture (‘gist’) of the discourse (Ditman and Kuperberg , , Kuperberg et al . ).…”

“…) and electrophysiological (ERP) studies (Kumar and DeBruille , Ditman and Kuperberg , Kuperberg , Ditman et al . ). These and other studies speak for overactive semantic priming, inability to suppress context‐inappropriate meanings and overreliance on semantic memory‐based associations.…”

“…As regards the mechanisms underlying disorganized discourse, deficient processing of context in schizophrenia has been demonstrated in several behavioural (Bazin et al 2000, Babin et al 2007, Andreou et al 2009) and electrophysiological (ERP) studies (Kumar and De-Bruille 2004, Ditman and Kuperberg 2007, Kuperberg 2010, Ditman et al 2011. These and other studies speak for overactive semantic priming, inability to suppress context-inappropriate meanings and overreliance on semantic memory-based associations.…”

“…We base this hypothesis especially on findings that speak for an abnormally long‐term lexical–semantic activation in schizophrenia (Ditman et al . ) and the relative inability of individuals in schizophrenia to inhibit parallel topics and thoughts (Kiang et al . , Niznikiewicz et al .…”

“…We hypothesize that (1) by analysing long stretches of discourse and focusing especially on recurrence of topics and referents, and (2) by taking into account the various knowledge stores and discourse models, we can often reveal structure in the allegedly disorganized speech in schizophrenia. We base this hypothesis especially on findings that speak for an abnormally long-term lexical-semantic activation in schizophrenia (Ditman et al 2011) and the relative inability of individuals in schizophrenia to inhibit parallel topics and thoughts (Kiang et al 2007, Niznikiewicz et al 2010.…”