A concurrent examination of neurocognitive and language impairments in schizophrenia thought disorder

Formal thought disorder (FTD) in schizophrenia has been associated with both cognitive and language impairments. However, there is still considerable debate regarding the degree to which each contributes to FTD. This study had two aims: (i) to examine which cognitive impairments are related to FTD and, (ii) to explore if FTD has any language-specific symptoms. 57 schizophrenia/schizoaffective patients and 48 healthy controls completed the MATRICS battery and D-KEFS Stroop task assessing general neurocognition and inhibition, as well as three language tasks assessing word identification (lexical recognition), synonym identification (lexical semantics) and sentence meanings (syntax). PANSS FTD ratings were used. Cognitive assessment results revealed FTD patients performed worse than non-FTD patients on measures of semantic and executive processing (p<.05), with both groups poorer than controls (p<.01). This supports indications of concurrent semantic and executive dysfunction, and suggests that a combination of both may relate to manifest FTD. Language assessment results revealed impairments in FTD compared to non-FTD patients and controls in the recognition of homophones (but not antonyms) and sentence comprehension (syntax). Lexical recognition of words (without semantic manipulation) was not impaired in schizophrenia patients generally compared to controls. This supports language processing impairments at both the single word and sentence levels in FTD. Significant correlations were observed between positive FTD symptoms and syntactic problems (p<.001). Stepwise regressions revealed that syntactic errors predicted 10% of the variance (p=.008) in positive TD severity, after controlling for semantic and executive deficits and lexical semantic processing. This provides evidence that a language-specific impairment of syntactic comprehension is present in schizophrenia, and exacerbated in FTD. Overall, this study supports current cognitive and language theories of impairment in FTD, with evidence for concurrence of executive, semantic and syntactic dysfunction