Assessing the Relationship between Semantic Processing and Thought Disorder Symptoms in Schizophrenia

Abstract

Aberrant semantic processing has been linked to the etiology of formal thought disorder (TD) symptoms in schizophrenia. In this cross-sectional study, two prominent theories, overactivation and disorganized structure of semantic memory (SM), were examined in relation to TD symptoms using the continuum approach across two established semantic tasks (direct/indirect semantic priming and categorical fluency). The aim was to examine the validity of the two TD theories in relation to TD symptoms in schizophrenia. Greater direct and indirect priming, fluency productivity and category errors were expected if the data supported the overactivation theory. Reduced fluency productivity and increased category errors would be characteristic of disorganized storage. Fifty-seven schizophrenia/schizoaffective disorder patients and 48 controls completed a clinical assessment and the semantic tasks. There was significantly reduced direct priming in patients compared to controls (p<.05), while indirect priming was not significantly different; there was no association between TD and degree of priming. Patients produced more category-inappropriate words (p<.005) than controls, which was related to increasing severity of circumstantiality. The pattern of results was more indicative of a disorganized SM storage problem in this sample. This phenomenon may underlie some TD symptoms in general schizophrenia. The findings strengthen the relationship between SM deficits and TD symptoms, though this appears to differ between individual symptoms. The authors discuss the value of the continuum approach in addressing research questions in TD etiology. Given low levels of TD in this study, replication of these findings in a sample with greater TD is desirable.

Impaired meaning-based cognitive skills are specifically associated with poorer subjective quality of life in schizophrenia

“…Our data further demonstrates that this relationship differs between patients and healthy controls, which is intuitive given that a better appreciation of what their life situation means in patients would then lead to reduced life satisfaction relative to healthy controls; indeed the current findings support this longstanding notion [44,13]. Impairment in semantic/meaning-making abilities is a recognised feature of schizophrenia [45] which may be affecting patient perceptions of their life situation. Previous work has shown that the cognition-sQOL relationship is independent of patient insight [6].…”

Reduced intra- and inter-individual diversity of semantic representations in the brains of schizophrenia patients

“…Patients with schizophrenia frequently manifest semantic processing impairments [1][2][3] , which may contribute to the formal thought disorder that is a hallmark of this disease [3][4][5][6] . It has been proposed that semantic processing impairments in schizophrenia stem from the disorganization of semantic storage in the brain 7,8 as evidenced by behavioral tests, such as verbal fluency [9][10][11][12][13][14] .…”

A systematic review of task-based functional neuroimaging studies investigating language, semantic and executive processes in thought disorder

“…Another limitation of current aetiological theories and hypotheses is that they tend to ignore the non-unitary nature of the manifestation of TD. Indeed, different aspects of TD appear to be subserved by different combinations of cognitive deficits (Barch and Berenbaum, 1996;Berenbaum and Barch, 1995;Tan et al, 2015;Tan and Rossell, 2017;Xu et al, 2014). For example, when four individual aspects of TD were explored in relation to three language production tasks, a heterogeneous pattern of relationships was found: errors in self-monitoring were associated with derailment and illogicality, errors in grammaticalphonological encoding were associated with neologisms and word approximations, and selecting irrelevant information during discourse planning was associated with incompetent references (Barch and Berenbaum, 1996).…”