How semantic deficits in schizotypy help understand language and thought disorders in schizophrenia: a systematic and integrative review

Individual differences in associative/semantic priming: Spreading of activation in semantic memory and epistemically unwarranted beliefs

Starting from the enhanced spreading of activation through semantic memory (one of the explanatory mechanisms attempting to explain some manifestations observed in schizophrenia) and the psychosis continuum (a dimensional approach to psychotic disorders, where 'normality' and 'psychopathology' are not qualitatively different in nature but placed on varying levels of the same continuum), the main aim of the present research was to explore whether there are individual differences in associative/semantic priming in people with different levels of epistemically unwarranted beliefs (EUB). Participants varying in paranormal, pseudoscientific and conspiracy endorsement completed a primed lexical decision task containing related prime-target words (e.g., bulb-light) and unrelated prime-target words (e.g., sock-light). Bayesian linear mixed-effects models over response times (RTs) revealed a main direct priming effect (faster RTs in related pairs than in unrelated ones), a main facilitatory effect for some EUB scores (i.e., the higher the value for EUB score, the faster RTs), and an interactive effect between the experimental manipulation and some EUB scores (the higher the EUB score, the smaller the direct priming effect). These results are consistent with predictions made from the enhanced spreading of activation explanatory mechanism, but other alternative accounts are also discussed.

Schizotypal traits and their relationship to reading abilities in healthy adults

Schizotypal traits (i.e., personality characteristics that range from mild eccentricities to more pronounced schizophrenia-like perceptions, thought patterns, and behaviours) have been associated with a variety of cognitive impairments, including difficulties in language processing. Although these difficulties span several aspects of language (e.g., semantic processing, verbal fluency, visual word recognition), it is unclear whether reading abilities are also affected. Thus, the current study employed the Schizotypal Personality Questionnaire (SPQ) - Brief (Raine and Benishay, 1995) to examine how schizotypal traits impact both word-level and text-level reading skills (using a battery of standardized assessments) in a sample of healthy young adults. We found some evidence that higher schizotypal traits, specifically, increased Disorganized factor scores (reflecting aberrant thinking, communication patterns, and behaviour), were associated with reduced word-level reading abilities. However, this finding did not remain significant after correcting for multiple comparisons. Overall, our study suggests that reading may be another aspect of language affected by schizotypal traits, although additional research (with greater power) is needed to further explore and confirm this finding.

Cognitive-perceptual and disorganized schizotypal traits are nonlinearly related to atypical semantic content on tasks of semantic fluency

Language deficits emerge early in the course of schizophrenia, yet research findings in those at-risk for schizophrenia, such as those with schizotypy, are mixed. The purpose of the present study was to elucidate the relationship of language ability, measured via semantic fluency, to schizotypy, examining both linear and non-linear relations. Semantic fluency data from 295 individuals with varying amounts of schizotypal traits were analyzed utilizing traditional methods (i.e., counting words generated that fit a specific semantic category). The content of semantic fluency responses was also analyzed via a semantic infrequency score (i.e., how infrequent participant responses were relative to all responses generated for the category in the study sample) and a total semantic productivity score (i.e., how many unique words generated overall, including those that did not fit the semantic category). Using traditional methods of scoring, schizotypy was not related to semantic fluency. However, schizotypy was non-linearly related to semantic infrequency and productivity, reflecting atypical semantic activation and processing. In particular, cognitive-perceptual and disorganized, but not interpersonal, traits were related to semantic infrequency and productivity. Valuable content-based information is missed when only analyzing semantic fluency data via the traditional method in the schizophrenia spectrum population. Cognitive-perceptual and disorganized traits, attenuated thought disorder symptoms, evidence the strongest relationship to semantic fluency, further illustrating the link between language and schizophrenia symptoms along the schizophrenia spectrum.

Schizotypal personality and semantic functioning: Revisiting category fluency effects in a subclinical sample

Semantic disturbances have been proposed as a possible cause of formal thought disorder in schizophrenia. Fluency tasks, in which volunteers are asked to produce as many exemplars as they can for a given category during one minute, are usually applied to the assessment of semantic processing. However, studies associating fluency and proneness to psychosis have provided conflicting results so it is not clear whether these disturbances can be identified at subclinical stages. We conducted two experiments. In the first one, 71 volunteers completed written category fluency tasks with four semantic categories (animals, fruits, clothing and vehicles). In the second experiment, 77 new participants completed oral category and phonological fluency tasks (words starting with f, t, p and c). In both experiments, we assessed schizotypal personality and vocabulary size. Schizotypal traits were not reliably associated with either productivity or originality of the responses in any experiment. In contrast, vocabulary size significantly predicted the participants' scores in all the tasks. Along with results of other recent studies, our data cast doubt on the reliability of previous observations pointing out an association between schizotypy and lexical-semantic disturbances, at least in relation to productivity and originality in fluency tests.

Cognitive functioning in schizotypy through the lens of the accessibility model

INTRODUCTION

Individuals with schizotypy self-report subjective cognitive complaints commensurate with deficits reported by individuals with schizophrenia. In contrast to schizophrenia, objective deficits in memory are modest in individuals with schizotypy, as compared to their self-reported cognitive complaints. It has been proposed that abnormalities in semantic memory systems may underlie this dysjunction.

METHODS

This study employed a modified verbal memory paradigm in a sample of 87 individuals with psychometrically defined schizotypy. Appraisals of memory performance were evaluated across global (i.e. drawing on semantic memory systems and assessing perceived typical performance) and situation-specific (i.e. drawing on episodic memory systems) epochs. Objective memory performance was assessed using a verbal recall paradigm.

RESULTS

Individuals with schizotypy did not differ in situation-specific appraisals or in objective memory performance. Global appraisals of memory performance predicted negative and disorganised schizotypy scores. No other measure of memory performance predicted any facet of schizotypy. Individuals with schizotypy appraised their global memory performance higher than controls at a medium effect.

CONCLUSIONS

Higher order global appraisals of cognitive performance, subsumed within semantic networks, may be important in the subjective-objective paradox in schizotypy, suggesting the importance of considering demand characteristics when assessing measures of neurocognitive performance in individuals with schizotypy.

Neuropsychological correlates of schizotypy: a systematic review and meta-analysis of cross-sectional studies

INTRODUCTION

Cognitive deficits can precede the onset of psychotic episodes and predict the onset of the illness in individuals with schizotypy traits. In some studies, high levels of schizotypy were associated with impairments in memory, attention, executive functions, and verbal fluency. This review provides a more comprehensive understanding of cognitive impairments related to schizoytpy.

METHODS

 A systematic review of "schizotypy and neuropsychological measures" was conducted, and it retrieved 67 studies. All papers with case-control design showing means and standard deviations from neuropsychological measures were included in a meta-analysis (n = 40). A comparison between our finding and another metaanalysis with patients with schizophrenia-spectrum disorders [Fatouros-Bergman, H., Cervenka, S., Flyckt, L., Edman, G., & Farde, L. (2014). Meta-analysis of cognitive performance in drugnaive patients with schizophrenia. Schizophrenia Research. doi: 10.1016/j.schres.2014.06.034 ] was performed to study the similarities on the MATRICS domains between the two disorders.

RESULTS

We found evidence of worse functioning of verbal and visual-spatial working memory, and of language in people with schizotypy or with schizotypal traits. Working memory deficit is present in both schizotypy and schizophrenia with larger effect sizes compared to other domains.

CONCLUSIONS

 Working memory deficit might be a cognitive marker of the risk of psychosis. Interventions targeting cognitive deficits early may be crucial to the prevention of psychosis.