Deficits in nominal reference identify thought disordered speech in a narrative production task.

Gabriel Sevilla,Raymond Salvador,Salvador Sarró,Wolfram Hinzen,Joana Rosselló,Laura López-Araquistain,Edith Pomarol-Clotet,Sinan Guloksuz

doi:10.1371/journal.pone.0201545

Abstract

Formal thought disorder (TD) is a neuropathology manifest in formal language dysfunction, but few behavioural linguistic studies exist. These have highlighted problems in the domain of semantics and more specifically of reference. Here we aimed for a more complete and systematic linguistic model of TD, focused on (i) a more in-depth analysis of anomalies of reference as depending on the grammatical construction type in which they occur, and (ii) measures of formal grammatical complexity and errors. Narrative speech obtained from 40 patients with schizophrenia, 20 with TD and 20 without, and from 14 healthy controls matched on pre-morbid IQ, was rated blindly. Results showed that of 10 linguistic variables annotated, 4 showed significant differences between groups, including the two patient groups. These all concerned mis-uses of noun phrases (NPs) for purposes of reference, but showed sensitivity to how NPs were classed: definite and pronominal forms of reference were more affected than indefinite and non-pronominal (lexical) NPs. None of the measures of formal grammatical complexity and errors distinguished groups. We conclude that TD exhibits a specific and differentiated linguistic profile, which can illuminate TD neuro-cognitively and inform future neuroimaging studies, and can have clinical utility as a linguistic biomarker.

Highlights

Formal thought disorder (TD) is a neuropathology clinically manifest in formal language dysfunction: expressive language is disorganized not at the level of the content of thought, but its form
TD was assessed with the Thought, Language and Communication (TLC) scale [2], and patients were included in the TD group based on a total score of >1
The results demonstrate a differentiated profile in which some linguistic variables showing sensitivity to TD divide from others that do not

Summary

Introduction

Formal thought disorder (TD) is a neuropathology clinically manifest in formal language dysfunction: expressive language is disorganized not at the level of the content of thought (what is expressed, as in the case of a delusion like ‘I have 1,000 children’), but its form (how it is said, i.e. its organization). It is a key symptom of schizophrenia according to the DSM-5, though not found in all patients with schizophrenia and not confined to this diagnosis. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Methods

Results

Conclusion