Inhibition and facilitation in schizotypy

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.

Cold executive function processes and their hot analogs in schizotypy

OBJECTIVE

To examine cold (based on logical reasoning) versus hot (having emotional components) executive function processes in groups with high individual schizotypal traits.

METHOD

Two-hundred and forty-seven participants were administered the Schizotypal Personality Questionnaire and were allocated into schizotypal (cognitive-perceptual, paranoid, negative, disorganized) or control groups according to pre-specified criteria. Participants were also administered a battery of tasks examining working memory, complex selective attention, response inhibition, decision-making and fluid intelligence and their affective counterparts. The outcome measures of each task were reduced to one composite variable thus formulating five cold and five hot cognitive domains. Between-group differences in the cognitive domains were examined with repeated measures analyses of covariance.

RESULTS

For working memory, the control and the cognitive-perceptual groups outperformed negative schizotypes, while for affective working memory controls outperformed the disorganized group. Controls also scored higher compared with the disorganized group in complex selective attention, while both the control and the cognitive-perceptual groups outperformed negative schizotypes in complex affective selective attention. Negative schizotypes also had striking difficulties in response inhibition, as they scored lower compared with all other groups. Despite the lack of differences in fluid intelligence, controls scored higher compared with all schizotypal groups (except from cognitive-perceptual schizotypes) in emotional intelligence; the latter group reported higher emotional intelligence compared with negative schizotypes.

CONCLUSION

Results indicate that there is no categorical association between the different schizotypal dimensions with solely cold or hot executive function processes and support impoverished emotional intelligence as a core feature of schizotypy.

Cognitive Functioning and Schizotypy: A Four-Years Study

Although there is ample evidence from cross-sectional studies indicating cognitive deficits in high schizotypal individuals that resemble the cognitive profile of schizophrenia-spectrum patients, there is still lack of evidence by longitudinal/follow-up studies. The present study included assessments of schizotypal traits and a wide range of cognitive functions at two time points (baseline and 4-years assessments) in order to examine (a) their stability over time, (b) the predictive value of baseline schizotypy on cognition at follow-up and (c) differences in cognition between the two time points in high negative schizotypal and control individuals. Only high negative schizotypal individuals were compared with controls due to the limited number of participants falling in the other schizotypal groups at follow-up. Seventy participants (mean age: 36.17; 70% females) were assessed at baseline and follow-up. Schizotypal traits were evaluated with the Schizotypal Personality Questionnaire. We found that schizotypal traits decreased over time, except in a sub-group of participants ("schizotypy congruent") that includes individuals who consistently meet normative criteria of inclusion in either a schizotypal or control group. In these individuals, negative schizotypy and aspects of cognitive-perceptual and disorganized schizotypy remained stable. The stability of cognitive functioning also varied over time: response inhibition, aspects of cued attention switching, set-shifting and phonemic/semantic verbal fluency improved at follow-up. High negative schizotypy at baseline predicted poorer response inhibition and semantic switching at follow-up while high disorganized schizotypy predicted poorer semantic processing and complex processing speed/set-shifting. The between-group analyses revealed that response inhibition, set-shifting and complex processing speed/set-shifting were poorer in negative schizotypals compared with controls at both time points, while maintaining set and semantic switching were poorer only at follow-up. Taken together, the findings show differential stability of the schizotypal traits over time and indicate that different aspects of schizotypy predict a different pattern of neuropsychological task performance during a 4-years time window. These results are of significant use in the formulation of targeted early-intervention strategies for high-risk populations.

Association of Schizotypy With Dimensions of Cognitive Control: A Meta-Analysis

Schizotypy is defined as a time-stable multidimensional personality trait consisting of positive, negative, and disorganized facets. Schizotypy is considered as a model system of psychosis, as there is considerable overlap between the 2 constructs. High schizotypy is associated with subtle but fairly widespread cognitive alterations, which include poorer performance in tasks measuring cognitive control. Similar but more pronounced impairments in cognitive control have been described extensively in psychosis. We here sought to provide a quantitative estimation of the effect size of impairments in schizotypy in the updating, shifting, and inhibition dimensions of cognitive control. We included studies of healthy adults from both general population and college samples, which used either categorical or correlative designs. Negative schizotypy was associated with significantly poorer performance on shifting (g = 0.32) and updating (g = 0.11). Positive schizotypy was associated with significantly poorer performance on shifting (g = 0.18). There were no significant associations between schizotypy and inhibition. The divergence in results for positive, negative, and disorganized schizotypy emphasizes the importance of examining relationships between cognition and the facets of schizotypy rather than using the overall score. Our findings also underline the importance of more detailed research to further understand and define this complex personality construct, which will also be of importance when applying schizotypy as a model system for psychosis.

Cognitive Correlates of Different Mentalizing Abilities in Individuals with High and Low Trait Schizotypy: Findings from an Extreme-Group Design

Mentalizing or Theory of Mind (ToM) deficits in schizophrenia have been studied to great extent, but studies involving samples of trait schizotypy yield ambiguous results. Executive functions like cognitive inhibition, cognitive flexibility, and agency are all prerequisites of mentalizing, and it is assumed that the impairment of these functions contributes to ToM deficits in schizophrenia. Whether these impairments influence the ToM performance of people with high trait schizotypy remains unclear. Although impaired self-agency has repeatedly been identified in people with schizotypy, its role in mentalizing is yet to be investigated. The main aim of this study was to explore whether deficits in cognitive and affective ToM can be found in high trait schizotypy, and to identify in what way these deficits are related to the positive and negative dimensions of schizotypy. The secondary aim was to examine whether these deficits correlate with executive functions. Based on the dimensional view of the schizophrenia spectrum, an extreme-group design was applied to non-clinical volunteers demonstrating high (N = 39) and low (N = 47) trait schizotypy. Affective and cognitive ToM were investigated using the Movie for Assessment of Social Cognition, a sensitive and video-based measurement. Cognitive inhibition was assessed using the Stroop Test, and cognitive flexibility was analyzed using the Trail-Making Test. Agency was measured using a computerized self-agency paradigm. Participants in the high-schizotypy group performed significantly worse in the affective ToM task (d = 0.79), and their overall ToM performance was significantly impaired (d = 0.60). No between-group differences were found with regards to cognitive ToM, executive functions, and self-agency. Cognitive flexibility correlated negatively with positive schizotypy, and contributed to a worse overall and affective ToM. Impaired cognitive inhibition contributed to undermentalizing-type errors. It was found that non-clinical participants with high trait (positive) schizotypy - especially those with slight executive-function deficits - may have difficulties in understanding the emotional state of others and consequently in functioning in social situations.

Associations of differential schizotypal dimensions with executive working memory: A moderated-mediation analysis

BACKGROUND

Increased schizotypal traits are observed in a percentage of the general population and in the schizophrenia-spectrum and have been associated with impairments in working memory. In this study we examined the effects of four schizotypal dimensions [Negative (NegS), Paranoid (ParS), Cognitive-Perceptual (CPS), Disorganized (DiS)] on executive working memory (EWM), as mediated by set-shifting, planning and control inhibition. We also examined whether these associations are moderated by family-history of psychosis.

METHODS

Our sample consisted of 110 unaffected first-degree relatives of schizophrenia-spectrum patients and 120 control individuals. Schizotypy was assessed with the Schizotypal Personality Questionnaire. Participants were also tested with the Letter-Number Sequencing, Wisconsin Card Sorting, Stroop Color-Word and Stockings of Cambridge tasks. The effects of set-shifting, control inhibition and planning on the relationship between schizotypy and EWM were examined with mediation analyses. Moderated-mediation analyses examined potential moderating effects of group membership (unaffected relative/community participant).

RESULTS

All mediators were significant in the relationship between NegS and EWM. The effects of ParS were mediated only by set-shifting and planning. Planning and control inhibition were the only significant mediators on the effects of CPS and DiS on EWM, respectively. The moderated-mediation analyses revealed that these findings apply only in the community group.

CONCLUSIONS

We found that the effects of different schizotypal dimensions on EWM are mediated by other cognitive processes in individuals without personal/family history of psychosis. This is probably due to either more severe impairments in the cognitive processes of the relatives or restrictions in our sample and study-design.

Individual differences in the executive control of attention, memory, and thought, and their associations with schizotypy

A large correlational study took a latent-variable approach to the generality of executive control by testing the individual-differences structure of executive-attention capabilities and assessing their prediction of schizotypy, a multidimensional construct (with negative, positive, disorganized, and paranoid factors) conveying risk for schizophrenia. Although schizophrenia is convincingly linked to executive deficits, the schizotypy literature is equivocal. Subjects completed tasks of working memory capacity (WMC), attention restraint (inhibiting prepotent responses), and attention constraint (focusing visual attention amid distractors), the latter 2 in an effort to fractionate the "inhibition" construct. We also assessed mind-wandering propensity (via in-task thought probes) and coefficient of variation in response times (RT CoV) from several tasks as more novel indices of executive attention. WMC, attention restraint, attention constraint, mind wandering, and RT CoV were correlated but separable constructs, indicating some distinctions among "attention control" abilities; WMC correlated more strongly with attentional restraint than constraint, and mind wandering correlated more strongly with attentional restraint, attentional constraint, and RT CoV than with WMC. Across structural models, no executive construct predicted negative schizotypy and only mind wandering and RT CoV consistently (but modestly) predicted positive, disorganized, and paranoid schizotypy; stalwart executive constructs in the schizophrenia literature-WMC and attention restraint-showed little to no predictive power, beyond restraint's prediction of paranoia. Either executive deficits are consequences rather than risk factors for schizophrenia, or executive failures barely precede or precipitate diagnosable schizophrenia symptoms. (PsycINFO Database Record

Schizotypal Traits are Associated with Poorer Executive Functioning in Healthy Adults

Previous research has shown mild forms of the neurocognitive impairments seen in schizophrenia among healthy individuals exhibiting high schizotypal traits. This study aimed to explore associations between schizotypy and cognitive performance in an adult community sample. Ninety-five females and 79 males completed the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE), which measures four separable aspects of schizotypy: cognitive disorganization, unusual experiences, introvertive anhedonia, and impulsive non-conformity. Subsequently, participants were administered a neurocognitive battery incorporating measures of executive skills including inhibition, cognitive flexibility, reasoning, and problem solving along with measures of attention and processing speed and both verbal and spatial working memory. In line with predictions, the current study found that higher scores on the subscales of unusual experiences, cognitive disorganization, and impulsive non-conformity related to worse performance on a measure of inhibition. Additionally, as introvertive anhedonia increased, both attention and processing speed and reasoning and problem-solving performance became more impaired. In conclusion, this study extends schizotypy literature by examining the subscales of the O-LIFE, and enables inferences to be drawn in relation to cognitive impairment in schizophrenia.

Genetics, cognition, and neurobiology of schizotypal personality: a review of the overlap with schizophrenia

Schizotypy refers to a set of temporally stable traits that are observed in the general population and that resemble the signs and symptoms of schizophrenia. Here, we review evidence from studies on genetics, cognition, perception, motor and oculomotor control, brain structure, brain function, and psychopharmacology in schizotypy. We specifically focused on identifying areas of overlap between schizotypy and schizophrenia. Evidence was corroborated that significant overlap exists between the two, covering the behavioral brain structural and functional as well molecular levels. In particular, several studies showed that individuals with high levels of schizotypal traits exhibit alterations in neurocognitive task performance and underlying brain function similar to the deficits seen in patients with schizophrenia. Studies of brain structure have shown both volume reductions and increase in schizotypy, pointing to schizophrenia-like deficits as well as possible protective or compensatory mechanisms. Experimental pharmacological studies have shown that high levels of schizotypy are associated with (i) enhanced dopaminergic response in striatum following administration of amphetamine and (ii) improvement of cognitive performance following administration of antipsychotic compounds. Together, this body of work suggests that schizotypy shows overlap with schizophrenia across multiple behavioral and neurobiological domains, suggesting that the study of schizotypal traits may be useful in improving our understanding of the etiology of schizophrenia.

Cognitive and prepulse inhibition deficits in psychometrically high schizotypal subjects in the general population: relevance to schizophrenia research

Schizophrenia and schizotypal personality disorder share common clinical profiles, neurobiological and genetic substrates along with Prepulse Inhibition and cognitive deficits; among those, executive, attention, and memory dysfunctions are more consistent. Schizotypy is considered to be a non-specific "psychosis-proneness," and understanding the relationship between schizotypal traits and cognitive function in the general population is a promising approach for endophenotypic research in schizophrenia spectrum disorders. In this review, findings for executive function, attention, memory, and Prepulse Inhibition impairments in psychometrically defined schizotypal subjects have been summarized and compared to schizophrenia patients and their unaffected first-degree relatives. Cognitive flexibility, sustained attention, working memory, and Prepulse Inhibition impairments were consistently reported in high schizotypal subjects in accordance to schizophrenia patients. Genetic studies assessing the effects of various candidate gene polymorphisms in schizotypal traits and cognitive function are promising, further supporting a polygenic mode of inheritance. The implications of the findings, methodological issues, and suggestions for future research are discussed.

Evidence of reduced selective attention in schizotypal personality disorder

It has been shown that high-schizotypy and schizophrenic participants demonstrate increased task-switching costs, although high-schizotypy participants present this pattern only in incongruent trials (Cimino & Haywood, 2008). In this study, we aim to explore whether this results from difficulties in selective attention or task control. A total of 18 participants with high levels of psychometrically defined schizotypy and 16 participants with low scores were tested in two different versions of a task-switching paradigm. Participants were asked to switch between attending to the color or the shape of bidimensional objects following a previous cue. Two versions of the task were investigated, one involving only switches in the perceptual dimension to attend (color or shape) and another also switching the response set. High-schizotypy subjects consistently showed increased switch costs in incongruent trials for both versions of the tasks, demonstrating a deficit in the selection of the perceptual dimension instead of the selection of the response rules.