Working memory and multidimensional schizotypy: dissociable influences of the different dimensions

Empathic accuracy in individuals with schizotypal personality traits

Empirical research using the Empathic Accuracy Task (EAT) has suggested that schizophrenia patients and people with schizotypal personality disorder exhibit lower empathic accuracy than healthy people. However, empathic accuracy in a subclinical sample with high levels of schizotypy has seldom been studied. Our study aimed to investigate empathy in a subclinical sample using the Chinese version of the EAT and a self-report empathy measure. Forty participants with high levels of schizotypy (HS participants) and 40 with low levels of schizotypy (LS participants), as measured by the Schizotypal Personality Questionnaire (SPQ), were recruited. All participants completed the Chinese version of the EAT and the self-report Questionnaire of Cognitive and Affective Empathy. Empathic accuracy (EA) scores and the intra-individual variability of EA scores were calculated. Independent samples t tests and Pearson correlation analyses were performed to examine group differences in empathy and the relationship between empathy and schizotypy respectively. HS participants exhibited reduced EA for both positive and negative videos, and larger intra-individual variability of EA for negative videos than LS participants. However, HS and LS participants did not differ in self-report cognitive empathy. Moreover, the interpersonal dimension of the SPQ was negatively correlated with EAT performance and self-report cognitive empathy in LS participants. Individuals with HS show poorer performance-based EA but relatively intact self-report cognitive empathy. This study provides empirical evidence for the ontogeny of empathy deficits in subclinical populations at risk of developing schizophrenia, supporting early interventions for social cognitive deficits.

Children's early signs and developmental trajectories of psychotic-like experiences

INTRODUCTION

Children who experience persistent psychotic-like experiences (PLEs) are at a higher risk of developing psychotic disorder later in life. The developmental trajectories of PLEs are influenced by various factors. Therefore, it is important to identify early characteristics that can distinguish and predict between different developmental trajectories of PLEs.

METHODS

Using PLEs scores from the Adolescent Brain Cognitive Development (ABCD) data across three waves, we categorized participants into five distinct PLEs trajectories groups: persistent group (n = 47), remitting group (n = 185), increasing group (n = 117), remittent group (n = 21), and no PLEs group (n = 4,476). We utilized linear mixed-effect models and generalized linear mixed-effect models to examine the differences in baseline characteristics, including psychological and behavioral problems, suicidality, trauma experiences, developmental milestones, cognitive function, physical health, family income, family history of mental illness, and brain structureamong these PLEs trajectory groups.

RESULTS

We found that psychological and behavioral problems (such as DSM-oriented scales/externalizing/ADHD/social/attention/thought problems) assessed by the Child Behavior Checklist (CBCL) were associated with all PLEs groups. The persistent PLEs group had greater ADHD/social/thought problems and suicidal behavior compared to the remitting PLEs group. Comparing with the no PLEs group, poor cognitive function, abnormal brain structure (such as temporal lobe and supramarginal gyrus), more trauma experiences, and lower family income were found in only one of the PLEs groups, but not all PLEs groups.

CONCLUSION

The development of PLEs is accompanied by changes in many domains, implying a dynamic and complex developmental process. Given that psychological and behavioral problems can predict the emergence of PLEs at any time and can be regarded as risk factors for persistent PLEs, thereby enabling early precisely interventions, it is important to place greater emphasis on assessing psychological and behavioral problems.

A Nomothetic Span Approach to the Construct Validation of Sustained Attention Consistency: Re-Analyzing Two Latent-Variable Studies of Performance Variability and Mind-Wandering Self-Reports

The ability to sustain attention consistency is frequently assessed using either objective behavioral measures, such as reaction time (RT) variability, or subjective self-report measures, such as rates of task-unrelated thought (TUT). The current studies examined whether the individual-difference covariation in these measures provides a more construct valid assessment of attention consistency than does either alone. We argue that performance and self-report measures mutually validate each other; each measurement approach has its own sources of error, so their shared variance should best reflect the attention consistency construct. We reanalyzed two latent-variable studies where RT variability and TUTs were measured in multiple tasks (Kane et al. in J Exp Psychol Gen 145:1017-1048, 2016; Unsworth et al. in J Exp Psychol Gen 150:1303-1331, 2021), along with several nomological network constructs to test the convergent and discriminant validity of a general attention consistency factor. Confirmatory factor analyses assessing bifactor (preregistered) and hierarchical (non-preregistered) models suggested that attention consistency can be modeled as the shared variance among objective and subjective measures. This attention consistency factor was related to working memory capacity, attention (interference) control, processing speed, state motivation and alertness, and self-reported cognitive failures and positive schizotypy. Although bifactor models of general attention consistency provide the most compelling construct validity evidence for a specific ability to sustain attention, multiverse analyses of outlier decisions suggested they are less robust than hierarchical models. The results provide evidence for the general ability to sustain attention consistency and suggestions for improving its measurement.

Nabilone Impairs Spatial and Verbal Working Memory in Healthy Volunteers

Background: Memory impairments and psychosis-like experiences can be adverse effects of cannabis use. However, reports on the cognitive impact of cannabis use are not consistent. There are also limited studies on the psychotomimetic effects of cannabinoid compounds to reveal the association between cannabis and psychosis. Therefore, we investigated the effect of acute cannabinoid intoxication on verbal working memory (VWM) and spatial working memory (SWM) following oral doses of the synthetic cannabinoid agonist, nabilone (1-2 mg, oral). We further investigated the effect of nabilone on psychosis-like experiences (schizotypy scores) and associations of schizotypy with VWM and SWM. Methods: Healthy participants (n=28) completed spatial and digit span tasks across different delay conditions (0, 6, 12, and 18 sec) after receiving nabilone (1-2 mg, PO) or placebo in a randomized, double-blind, counterbalanced, crossover manner. A subset of participants completed a short battery of schizotypy measures (n=25). Results: Nabilone impaired VWM (p=0.03, weak effect size η2=0.02) and SWM (p=0.00016, η2=0.08). Nabilone did not significantly change overall schizotypy scores. Schizotypy scores were negatively correlated with working memory (WM) averaged across all delays and both modalities, under placebo (ρ=-0.41, p=0.04). In addition, there were significant negative correlations between occasions of cannabis use and overall WM averaged scores across drug treatments (ρ=-0.49, p=0.007) and under placebo (ρ=-0.45, p=0.004). The results showed that the drug effect in the less frequent cannabis users was more pronounced on the SWM (p<0.01) and VWM (p<0.01), whereas there appeared to be little drug effect in the frequent cannabis users. Conclusion: Low doses of synthetic cannabinoid impaired SWM and VWM, indicating that exogenous activation of the cannabinoid system influences cognitive performance. Further, the results replicated previous findings that schizotypy is correlated with deficits in WM. Clinical Trial Registry Name: Nabilone and caffeine effects on the perceptions of visually, auditory, tactile and multimodal illusions in healthy volunteers. Clinical Trial Registration Number: CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry).

The effects of caffeine and d-amphetamine on spatial span task in healthy participants

Studies that examined the effect of amphetamine or caffeine on spatial working memory (SWM) and verbal working memory (VWM) have used various tasks. However, there are no studies that have used spatial span tasks (SSTs) to assess the SWM effect of amphetamine and caffeine, although some studies have used digit span tasks (DST) to assess VWM. Previous reports also showed that increasing dopamine increases psychosis-like experiences (PLE, or schizotypy) scores which are in turn negatively associated with WM performance in people with high schizotypy and people with schizophrenia. Therefore, the present study aimed to examine the influence of d-amphetamine (0.45 mg/kg, PO), a dopamine releasing stimulant, on SST, DST, and on PLE in healthy volunteers. In a separate study, we examined the effect of caffeine, a nonspecific adenosine receptor antagonist with stimulant properties, on similar tasks.

METHODS

Healthy participants (N = 40) took part in two randomized, double-blind, counter-balanced placebo-controlled cross-over pilot studies: The first group (N = 20) with d-amphetamine (0.45 mg/kg, PO) and the second group (N = 20) with caffeine (200 mg, PO). Spatial span and digit span were examined under four delay conditions (0, 2, 4, 8 s). PLE were assessed using several scales measuring various aspects of psychosis and schizotypy.

RESULTS

We failed to find an effect of d-amphetamine or caffeine on SWM or VWM, relative to placebo. However, d-amphetamine increased a composite score of psychosis-like experiences (p = 0.0005), specifically: Scores on Brief Psychiatric Rating Scale, Perceptual Aberrations Scale, and Magical Ideation Scale were increased following d-amphetamine. The degree of change in PLE following d-amphetamine negatively and significantly correlated with changes in SWM, mainly at the longest delay condition of 8 s (r = -0.58, p = 0.006).

CONCLUSION

The present results showed that moderate-high dose of d-amphetamine and moderate dose of caffeine do not directly affect performances on DST or SST. However, the results indicate that d-amphetamine indirectly influences SWM, through its effect on psychosis-like experiences.

TRIAL REGISTRATION

CLINICAL TRIAL REGISTRATION NUMBER

CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry) for caffeine study, and ACTRN12608000610336 for d-amphetamine study.

Working memory and sensory memory in subclinical high schizotypy: An avenue for understanding schizophrenia?

The search for robust, reliable biomarkers of schizophrenia remains a high priority in psychiatry. Biomarkers are valuable because they can reveal the underlying mechanisms of symptoms and monitor treatment progress and may predict future risk of developing schizophrenia. Despite the existence of various promising biomarkers that relate to symptoms across the schizophrenia spectrum, and despite published recommendations encouraging multivariate metrics, they are rarely investigated simultaneously within the same individuals. In those with schizophrenia, the magnitude of purported biomarkers is complicated by comorbid diagnoses, medications and other treatments. Here, we argue three points. First, we reiterate the importance of assessing multiple biomarkers simultaneously. Second, we argue that investigating biomarkers in those with schizophrenia-related traits (schizotypy) in the general population can accelerate progress in understanding the mechanisms of schizophrenia. We focus on biomarkers of sensory and working memory in schizophrenia and their smaller effects in individuals with nonclinical schizotypy. Third, we note irregularities across research domains leading to the current situation in which there is a preponderance of data on auditory sensory memory and visual working memory, but markedly less in visual (iconic) memory and auditory working memory, particularly when focusing on schizotypy where data are either scarce or inconsistent. Together, this review highlights opportunities for researchers without access to clinical populations to address gaps in knowledge. We conclude by highlighting the theory that early sensory memory deficits contribute negatively to working memory and vice versa. This presents a mechanistic perspective where biomarkers may interact with one another and impact schizophrenia-related symptoms.

Mental rotation and schizotypal personality traits: A Bayesian approach

People diagnosed with schizophrenia exhibit mental rotation differences, suggesting that clinical levels of positive symptoms, such as psychotic hallucinations, are related to disruptions in their monitoring and manipulation of mental representations. According to the psychosis continuum, findings in people with a high level of schizotypal personality traits are expected to be qualitatively similar, but research concerning this topic is scarce. A spared mental imagery manipulation in this population only could suggest that this ability might be a possible protective factor, or that the emergence of clinical-level positive symptoms could be paired with disruptions in this capacity. To explore this issue, 205 undergraduate students (122 women) completed a novel mental rotation task identifying the stimulus that was a 90, 180, or 270° rotation of a black circle with colored portions and were assessed with the Schizotypal Personality Questionnaire. Men performed better in most conditions. No relationship was detected between schizotypal personality traits and accuracy in the task. These results do not support that mental imagery manipulation disruptions may be related to schizotypal personality traits in non-clinical populations. Thus, they might instead be associated with the onset of psychosis disorders as mental representation handling is hindered. However, additional research is required including the general population, as well as those with higher levels of psychotic symptoms and psychosis disorders. Future research could also focus on working memory processes related to mental representation manipulations of different sensory modalities such as auditory mental representations and their relationship with schizotypal personality traits and clinical populations.

Comparison of executive functions in individuals with high and low levels of schizotypal trait

The dimensional approach to Schizotypal Personality Disorder (SPD) indicates that SPD includes a constellation of maladaptive personality traits on a continuum with general personality functioning. This study aimed to compare executive functions (EFs) in low and high-level schizotypal individuals. Using a convenient sampling method, we recruited 120 individuals, from which 30 individuals with high schizotypal trait levels (fourth quartile) and 30 participants with lower schizotypal trait levels (first quartile) were selected based on their scores on the schizotypal personality disorder questionnaire. Then, participants from the two groups were administered the Corsi Block-Tapping Test (CBTT), Wisconsin Card Sorting Test (WCST), and Continuance Performance Test (CPT). The results indicated individuals with higher schizotypy trait levels performed significantly poorer in tasks measuring working-visual-spatial memory, cognitive flexibility, sustained attention, and response inhibition. This pattern of results indicated that EF dysfunctions in individuals with higher schizotypy trait levels would cause significant disturbances in multiple areas of life. The practical implications of the findings are further discussed.

Systematic reviews of the acute effects of amphetamine on working memory and other cognitive performances in healthy individuals, with a focus on the potential influence of personality traits

OBJECTIVES

This research aimed to systematically review the acute effects of amphetamine (AMP), a dopamine-releasing agent, on working memory (WM) and other cognitive performances. The investigation also aimed to review the impact of personality traits on the subjective and objective effects of AMP and possible links between personality traits and effects of AMP.

METHODS

Previous double-blind controlled studies assessing the main effects of AMP on WM and other cognitive performances in healthy volunteers were systematically reviewed. An electronic search was performed in the PUBMED and SCOPUS databases. Narrative reviews of the influence of personality traits on the subjective and objective effects of AMP were included.

RESULTS

Nineteen WM studies were included in the current review. Seven studies found effects of AMP on spatial WM, but only one study found the effect of AMP on verbal WM. Thirty-seven independent studies on other aspects of cognitive performance were identified. Twenty-two reported effects of AMP on cognitive functions. Studies also showed that personality traits are associated with the subjective effects of AMP. However, few studies reported the impacts of personality traits on the objective (such as WM) effects of AMP.

CONCLUSION

Overall, findings indicate that AMP has mixed-effects on spatial WM and other cognitive functions, but it lacks effects on verbal WM. Although there are insufficient studies on objective measures, studies also indicated that the subjective effects of AMP administration are linked to between-person variations in personality traits.

Clinical insight and cognitive functioning as mediators in the relationships between symptoms of psychosis, depression, and suicide ideation in first-episode psychosis

First-episode psychosis (FEP) is a particularly high-risk period for suicide. Literature suggests poor cognitive functioning may serve as a protective factor, while investigations of clinical insight reveal a complex relationship with suicide outcomes. This study examined the mediating role of cognition and clinical insight in the relationships between positive and negative symptoms, depression, and subsequent suicide ideation among individuals in FEP. Data were obtained from the Recovery After an Initial Schizophrenia Episode project. Participants (n = 404) included adolescents and adults in FEP between the ages of 15 and 40. Measurement utilized the Calgary Depression Rating Scale, Positive and Negative Syndrome Scale, and Brief Assessment of Cognition in Schizophrenia. Structural equation modeling was used to examine the mediation model. The likelihood of experiencing suicide ideation was significantly decreased when working memory was stronger (b = -0.034, SE = 0.02, OR = 0.967, p < .05), and significantly increased when clinical insight was stronger (b = 0.191, SE = 0.08, OR = 1.21, p < .01), positive symptoms were greater (b = 0.422, SE = 0.20, OR = 1.52, p < .05) and depressive symptoms were greater (b = 0.545, SE = 0.15, OR = 1.70, p < .001). Clinical insight and working memory functioned as mediators in the relationships between depression, positive symptoms, negative symptoms, and suicide ideation. Findings suggest it is essential that clinicians have awareness of insight being a risk factor for suicide ideation and balance therapeutic efforts to strengthen clinical insight and cognition in psychosocial treatments with suicide risk assessment and prevention methods.

Linking RDoC and HiTOP: A new interface for advancing psychiatric nosology and neuroscience

The Research Domain Criteria (RDoC) and the Hierarchical Taxonomy of Psychopathology (HiTOP) represent major dimensional frameworks proposing two alternative approaches to accelerate progress in the way psychopathology is studied, classified, and treated. RDoC is a research framework rooted in neuroscience aiming to further the understanding of transdiagnostic biobehavioral systems underlying psychopathology and ultimately inform future classifications. HiTOP is a dimensional classification system, derived from the observed covariation among symptoms of psychopathology and maladaptive traits, which seeks to provide more informative research and treatment targets (i.e., dimensional constructs and clinical assessments) than traditional diagnostic categories. This article argues that the complementary strengths of RDoC and HiTOP can be leveraged in order to achieve their respective goals. RDoC's biobehavioral framework may help elucidate the underpinnings of the clinical dimensions included in HiTOP, whereas HiTOP may provide psychometrically robust clinical targets for RDoC-informed research. We present a comprehensive mapping between dimensions included in RDoC (constructs and subconstructs) and HiTOP (spectra and subfactors) based on narrative review of the empirical literature. The resulting RDoC-HiTOP interface sheds light on the biobehavioral correlates of clinical dimensions and provides a broad set of dimensional clinical targets for etiological and neuroscientific research. We conclude with future directions and practical recommendations for using this interface to advance clinical neuroscience and psychiatric nosology. Ultimately, we envision that this RDoC-HiTOP interface has the potential to inform the development of a unified, dimensional, and biobehaviorally-grounded psychiatric nosology.

Functional connectivity of cerebellar dentate nucleus and cognitive impairments in patients with drug-naive and first-episode schizophrenia

Cognitive impairments are the hallmark of schizophrenia and prominent in the early episode stage. However, the underlying pathological mechanisms of cognitive impairments are not fully understood. This study aimed to investigate the abnormal functional connectivity (FC) of the cerebellar dentate nucleus (DN) and its correlation with cognitive impairments in patients with drug-naive and first-episode schizophrenia. Resting-state functional magnetic resonance imaging data were acquired in 47 patients and 43 healthy controls. Cognitive functions were assessed by number sequence span, verbal category fluency, digit-symbol coding tests. The results showed that the patients had deficits in all three cognitive tests compared to the controls. Furthermore, the increased FC of DN with the bilateral postcentral gyrus and decreased FC of DN with the right inferior temporal gyrus and regional cerebellum (e.g., Vermis 4-5 and Crus I) were observed in the patient group compared to the control group. Importantly, these abnormal DN FC significantly correlated with cognitive tests (e.g., number sequence span and digit-symbol coding) and clinical symptoms (e.g., negative symptom) in the patient group. The results suggested that abnormal FC of DN with cortical and subcortical regions was associated with cognitive impairments and symptom severity and might be an underlying neural mechanism in schizophrenia.

Resting frontal EEG asymmetry and schizotypal traits: a test-retest study

Introduction: Increase in right relative to left frontal electroencephalography (EEG) activity has been observed in patients with schizophrenia, both in cognitive tasks and during rest; and this lateralisation may be related to the severity of schizotypal traits. Methods: We used the Schizotypal Personality Questionnaire (SPQ) to assess schizotypal traits, and examined the correlation between these traits and resting EEG frontal asymmetry (left-right) in 52 college students, as well as the reliability of this correlation over a three-month interval. Results: A higher total score on the SPQ was correlated with reduced asymmetry in different frequency bands: gamma and beta2 frequency bands at baseline, and delta and alpha frequency bands three months later. Additionally, the reduced left relative to right frontal gamma and beta2 asymmetry was correlated with the participants' verbal fluency ability. However, this correlation was no longer statistically significant after the total SPQ score was controlled. Conclusions: These findings suggest that resting frontal EEG asymmetry is correlated with powers in different frequency bands, and may be an endophenotype for schizophrenia spectrum disorders.

Relationships between intra-individual variability and subclinical psychosis

Extensive research indicates that elevated intra-individual variability (IIV) of reaction time is associated with subclinical psychosis, as well as clinically diagnosed psychotic disorder. However, findings regarding the details of this relationship are equivocal. In particular, it is unknown whether associations between elevated IIV and subclinical psychosis are specific to certain psychotic symptoms or to complex reaction time tasks. Data from 492 undergraduates from the University of Otago were used to address this issue. Schizotypy and psychotic-like experiences (PLE) were assessed via interview and questionnaire, and participants completed both a simple reaction time (SRT) task and a continuous performance task-identical pairs version (CPT-IP). The individual standard deviation and coefficient of variation (ICV) were used as measures of IIV. Participants reporting PLE were more likely to have elevated ICV on the CPT-IP. These associations were specific to paranoid psychotic experiences, and to the suspiciousness subscale of the Schizotypal Personality Questionnaire. There were also weak associations between SRT ICV and PLE. The inclusion of a battery of reaction time tasks assessing different aspects of cognitive control is suggested for future research, and the findings are discussed in relation to theoretical approaches to paranoia and delusions.

Clinical utility of the dual n-back task in schizophrenia: A functional imaging approach

The neural correlate of working memory (WM) impairment in schizophrenia is key to the understanding of the cognitive deficits observed in this disorder. We sought to determine the clinical validity of the dual version n-back paradigm in patients with schizophrenia, and whether schizophrenia patients exhibit altered brain activation patterns compared with healthy controls in this dual version WM measure using functional magnetic resonance imaging. Patients with schizophrenia (n = 20) and healthy controls (n = 24) performed the dual n-back task that consists of both visuospatial and auditory-verbal n-back streams, in which participants were required to monitor and update the contents from these two different inputs simultaneously. Significant positive correlations were found between performance in the dual 2-back condition and another measure of WM capacity and IQ estimates. Moreover, hypoactivation was observed at the right middle frontal gyrus and the posterior parietal regions in schizophrenia participants compared with healthy controls. The right hippocampus was less deactivated in schizophrenia patients compared with healthy controls. Our results support the clinical utility of the dual n-back task in schizophrenia and may have implications for the development of specific cognitive training targeting these impaired neural substrates in relation to WM in patients with schizophrenia.

Social functioning impairments in schizotypy when social cognition and neurocognition are not impaired

The present study examined the social, cognitive, and emotional functioning of persons with schizotypy. Over 2000 undergraduate students were screened for schizotypy with the Schizotypal Personality Questionnaire - Brief over two consecutive semesters. Ninety-two persons with high schizotypy and 22 persons with low schizotypy completed measures of social functioning (Social Adjustment Scale, Social Functioning Scale, MOS Social Support Survey), working memory (Paced Auditory Serial Addition Test, Digit Span, Letter-Number Sequencing, Corsi Block Tapping Test) and empathy (Interpersonal Reactivity Index, Empathy Quotient). Persons with high schizotypy, when compared to their counterparts with low schizotypy, displayed deficits on many indices of social functioning even though differences in working memory and empathy were not observed. The social functioning deficits of persons with high schizotypy included impairments in friendship relations, family relations, interpersonal engagement, and recreational activities. These findings indicate that persons with high schizotypy experience broad deficits in social functioning even when their cognitive and emotional skills are unaffected.

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.

Do complaints of everyday cognitive failures in high schizotypy relate to emotional working memory deficits in the lab?

BACKGROUND

Individuals high on schizotypy complain of increased cognitive failures in everyday life. However, the neuropsychological performance of this group does not consistently indicate underlying ability deficits. It is possible that current neuropsychological tests lack ecological validity. Given the increased affective reactivity of high schizotypes, they may be more sensitive to emotional content interfering with cognitive ability. This study sought to explore whether an affective n-back working memory task would elicit impaired performance in schizotypy, echoing complaints concerning real world cognition.

METHODS

127 healthy participants completed self-report measures of schizotypy and cognitive failures and an affective n-back working memory task. This task was varied across three levels of load (1- to 3-back) and four types of stimulus emotion (neutral, fearful, happy, sad). Differences between high (n=39) and low (n=48) schizotypy groups on performance outcomes of hits and false alarms were examined, with emotion and load as within-groups variables.

RESULTS

As expected, high schizotypes reported heightened vulnerability to cognitive failures. They also demonstrated a relative working memory impairment for emotional versus neutral stimuli, whereas low schizotypes did not. High schizotypes performed most poorly in response to fearful stimuli. For false alarms, there was an interaction between schizotypy, load, and emotion, such that high schizotypy was associated with deficits in response to fearful stimuli only at higher levels of task difficulty. Inclusion of self-reported cognitive failures did not account for this.

CONCLUSION

These findings suggest that the "gap" between subjective and objective cognition in schizotypy may reflect the heightened emotional demands associated with cognitive functioning in the real world, although other factors also seem to play a role. There is a need to improve the ecological validity of objective assessments, whilst also recognizing that self-reported cognitive failures tap into a range of factors difficult to assess in the lab, including emotion. Cognitive interventions for at-risk individuals will likely be more beneficial if they address emotional processing alongside other aspects of cognition.

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.

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

Cognitive and oculomotor performance in subjects with low and high schizotypy: implications for translational drug development studies

The development of drugs to improve cognition in patients with schizophrenia is a major unmet clinical need. A number of promising compounds failed in recent clinical trials, a pattern linked to poor translation between preclinical and clinical stages of drug development. Seeking proof of efficacy in early Phase 1 studies in surrogate patient populations (for example, high schizotypy individuals where subtle cognitive impairment is present) has been suggested as a strategy to reduce attrition in the later stages of drug development. However, there is little agreement regarding the pattern of distribution of schizotypal features in the general population, creating uncertainty regarding the optimal control group that should be included in prospective trials. We aimed to address this question by comparing the performance of groups derived from the general population with low, average and high schizotypy scores over a range of cognitive and oculomotor tasks. We found that tasks dependent on frontal inhibitory mechanisms (N-Back working memory and anti-saccade oculomotor tasks), as well as a smooth-pursuit oculomotor task were sensitive to differences in the schizotypy phenotype. In these tasks the cognitive performance of 'low schizotypes' was significantly different from 'high schizotypes' with 'average schizotypes' having an intermediate performance. These results indicate that for evaluating putative cognition enhancers for treating schizophrenia in early-drug development studies the maximum schizotypy effect would be achieved using a design that compares low and high schizotypes.

Psychotic Experiences and Working Memory: A Population-Based Study Using Signal-Detection Analysis

Psychotic Experiences (PEs) during adolescence index increased risk for psychotic disorders and schizophrenia in adult life. Working memory (WM) deficits are a core feature of these disorders. Our objective was to examine the relationship between PEs and WM in a general population sample of young people in a case control study. 4744 individuals of age 17–18 from Bristol and surrounding areas (UK) were analyzed in a cross-sectional study nested within the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort study. The dependent variable was PEs, assessed using the semi-structured Psychosis-Like Symptom Interview (PLIKSi). The independent variable was performance on a computerized numerical n-back working memory task. Signal-Detection Theory indices, including standardized hits rate, false alarms rate, discriminability index (d’) and response bias (c) from 2-Back and 3-Back tasks were calculated. 3576 and 3527 individuals had complete data for 2-Back and 3-Back respectively. Suspected/definite PEs prevalence was 7.9% (N = 374). Strongest evidence of association was seen between PEs and false alarms on the 2-Back, (odds ratio (OR) = 1.17 [95% confidence intervals (CI) 1.01, 1.35]) and 3-back (OR = 1.35 [1.18, 1.54]) and with c (OR = 1.59 [1.09, 2.34]), and lower d’ (OR = 0.76 [0.65, 0.89]), on the 3-Back. Adjustment for several potential confounders, including general IQ, drug exposure and different psycho-social factors, and subsequent multiple imputation of missing data did not materially alter the results. WM is impaired in young people with PEs in the general population. False alarms, rather than poor accuracy, are more closely related to PEs. Such impairment is consistent with different neuropsychological models of psychosis focusing on signal-to-noise discrimination, probabilistic reasoning and impaired reality monitoring as a basis of psychotic symptoms.

Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

Many neuropsychiatric illnesses are associated with psychosis, i.e., hallucinations (perceptions in the absence of causative stimuli) and delusions (irrational, often bizarre beliefs). Current models of brain function view perception as a combination of two distinct sources of information: bottom-up sensory input and top-down influences from prior knowledge. This framework may explain hallucinations and delusions. Here, we characterized the balance between visual bottom-up and top-down processing in people with early psychosis (study 1) and in psychosis-prone, healthy individuals (study 2) to elucidate the mechanisms that might contribute to the emergence of psychotic experiences. Through a specialized mental-health service, we identified unmedicated individuals who experience early psychotic symptoms but fall below the threshold for a categorical diagnosis. We observed that, in early psychosis, there was a shift in information processing favoring prior knowledge over incoming sensory evidence. In the complementary study, we capitalized on subtle variations in perception and belief in the general population that exhibit graded similarity with psychotic experiences (schizotypy). We observed that the degree of psychosis proneness in healthy individuals, and, specifically, the presence of subtle perceptual alterations, is also associated with stronger reliance on prior knowledge. Although, in the current experimental studies, this shift conferred a performance benefit, under most natural viewing situations, it may provoke anomalous perceptual experiences. Overall, we show that early psychosis and psychosis proneness both entail a basic shift in visual information processing, favoring prior knowledge over incoming sensory evidence. The studies provide complementary insights to a mechanism by which psychotic symptoms may emerge.

High and low schizotypal female subjects do not differ in spatial memory abilities in a virtual reality task

INTRODUCTION

Schizotypy is a psychological construct related to schizophrenia. The exact relationship between both entities is not clear. In recent years, schizophrenia has been associated with hippocampal abnormalities and spatial memory problems. The aim of this study was to determine possible links between high schizotypy (HS) and low schizotypy (LS) and spatial abilities, using virtual reality tasks. We hypothesised that the HS group would exhibit a lower performance in spatial memory tasks than the LS group.

METHODS

Two groups of female students were formed according to their score on the ESQUIZO-Q-A questionnaire. HS and LS subjects were tested on two different tasks: the Boxes Room task, a spatial memory task sensitive to hippocampal alterations and a spatial recognition task.

RESULTS

Data showed that both groups mastered both tasks. Groups differed in personality features but not in spatial performance. These results provide valuable information about the schizotypy-schizophrenia connections.

CONCLUSION

Schizotypal subjects are not impaired on spatial cognition and, accordingly, the schizotypy-schizophrenia relationship is not straightforward.

Cognition and brain function in schizotypy: a selective review

Schizotypy refers to a set of personality traits thought to reflect the subclinical expression of the signs and symptoms of schizophrenia. Here, we review the cognitive and brain functional profile associated with high questionnaire scores in schizotypy. We discuss empirical evidence from the domains of perception, attention, memory, imagery and representation, language, and motor control. Perceptual deficits occur early and across various modalities. While the neural mechanisms underlying visual impairments may be linked to magnocellular dysfunction, further effects may be seen downstream in higher cognitive functions. Cognitive deficits are observed in inhibitory control, selective and sustained attention, incidental learning, and memory. In concordance with the cognitive nature of many of the aberrations of schizotypy, higher levels of schizotypy are associated with enhanced vividness and better performance on tasks of mental rotation. Language deficits seem most pronounced in higher-level processes. Finally, higher levels of schizotypy are associated with reduced performance on oculomotor tasks, resembling the impairments seen in schizophrenia. Some of these deficits are accompanied by reduced brain activation, akin to the pattern of hypoactivations in schizophrenia spectrum individuals. We conclude that schizotypy is a construct with apparent phenomenological overlap with schizophrenia and stable interindividual differences that covary with performance on a wide range of perceptual, cognitive, and motor tasks known to be impaired in schizophrenia. The importance of these findings lies not only in providing a fine-grained neurocognitive characterization of a personality constellation known to be associated with real-life impairments, but also in generating hypotheses concerning the aetiology of schizophrenia.

Impairments of working memory in schizophrenia and bipolar disorder: the effect of history of psychotic symptoms and different aspects of cognitive task demands

Comparisons of cognitive impairments between schizophrenia (SZ) and bipolar disorder (BPD) have produced mixed results. We applied different working memory (WM) measures (Digit Span Forward and Backward, Short-delay and Long-delay CPT-AX, N-back) to patients with SZ (n = 23), psychotic BPD (n = 19) and non-psychotic BPD (n = 24), as well as to healthy controls (HC) (n = 18) in order to compare the level of WM impairments across the groups. With respect to the less demanding WM measures (Digit Span Forward and Backward, Short-delay CPT-AX), there were no between group differences in cognitive performance; however, with respect to the more demanding WM measures (Long-delay CPT-AX, N-back), we observed that the groups with psychosis (SZ, psychotic BPD) did not differ from one another, but performed poorer than the group without a history of psychosis (non-psychotic BPD). A history of psychotic symptoms may influence cognitive performance with respect to WM delay and load effects as measured by Long-delay CPT-AX and N-back tests, respectively. We observed a positive correlation of WM performance with antipsychotic treatment and a negative correlation with depressive symptoms in BPD and with negative symptoms in SZ subgroup. Our study suggests that WM dysfunctions are more closely related to a history of psychosis than to the diagnostic categories of SZ and BPD described by psychiatric classification systems.

WORKING MEMORY IMPAIRMENT AS AN ENDOPHENOTYPIC MARKER OF A SCHIZOPHRENIA DIATHESIS

This chapter focuses on the viability of working memory impairment as an endophenotypic marker of a schizophrenia diathesis. It begins with an introduction of the construct of working memory. It follows with a review of the operational criteria for defining an endophenotype. Research findings regarding the working memory performance of schizophrenia and schizophrenia-spectrum patients, first-degree relatives of schizophrenia patients and healthy controls, are reviewed in terms of the criteria for being considered an endophenotypic marker. Special attention is paid to specific components of the working memory deficit (namely, encoding, maintenance, and manipulation), in terms of which aspects are likely to be the best candidates for endophenotypes. We consider the extant literature regarding working memory performance in bipolar disorder and major depression in order to address the issue of relative specificity to schizophrenia. Despite some unresolved issues, it appears that working memory impairment is a very promising candidate for an endophenotypic marker of a schizophrenia diathesis but not for mood disorders. Throughout this chapter, we identify future directions for research in this exciting and dynamic area of research and evaluate the contribution of working memory research to our understanding of schizophrenia.

Schizotypal personality disorder: a current review

The study of schizotypal personality disorder (SPD) is important clinically, as it is understudied, challenging to treat, often under-recognized or misdiagnosed, and associated with significant functional impairment. SPD also represents an intermediate schizophrenia-spectrum phenotype, and therefore, can provide a better understanding of the genetics, pathogenesis, and treatment of related psychotic illnesses. In this review we discuss recent findings of SPD related to epidemiology and functional impairment, heritability and genetics, working memory and cognitive impairments, social-affective disturbances, and neurobiology. Additionally, we examine the challenges associated with treating patients with SPD, as well as clinical recommendations. Finally, we address future directions and areas in need of further exploration.

Genetic modulation of working memory deficits by ankyrin 3 gene in schizophrenia

Neuropsychological endophenotype approach is an emerging strategy in schizophrenia research to understand and identify the functional importance of genetically transmitted, brain-based deficits present in this disorder. Accumulating evidence indicated that working memory deficit is a core neuropsychological dysfunction in schizophrenia and a primary endophenotype indexing the liability to develop schizophrenia. Genetic variation in ankyrin 3 gene (ANK3) is likely to have widespread cognitive effects. Our previous study has identified a significant association of ANK3 SNPs and schizophrenia. In this study, we aimed to examine whether the schizophrenia-risk SNPs within ANK3 may affect working memory deficits in schizophrenia patients. Herein, we assess the working memory performance in 163 patients with first-episode, antipsychotic-naïve schizophrenia and 42 sex, age-matched healthy subjects using N-back task. Two SNPs rs10761482 and rs10994336 were genotyped among the patients and 209 controls. Our results showed that schizophrenia patients showed significantly poorer performance than healthy controls on N-back task (ps<0.01). After adjusting for the scores of intelligence quotient, memory quotient and the demographic factors, there was a significant genotype effect of the rs10994336 on the accuracy rate and reaction time of 2-back item (p=0.048 and 0.024, respectively). Post-hoc analyses showed that patients with rs10994336T/T genotype had significantly lower accuracy rate and more reaction time at 2-back task than those with T/C and C/C genotypes. The association of SNP rs10994336 with schizophrenia was replicated in our sample (genotypic p=0.024 and allelic p=0.006). However, we did not find any significant association of rs10761482 with schizophrenia and parameters in N-back task. Our results indicated that genetic variation within ANK3 may exert gene-specific modulating effects on working memory deficits in schizophrenia.

Working memory in schizotypal personality disorder: fMRI activation and deactivation differences

BACKGROUND

Schizotypal personality disorder (SPD) is considered a schizophrenia spectrum disorder, sharing with schizophrenia cognitive, neuropsychological, epidemiological, and biological characteristics. Working memory may be one area of shared deficit, although to date, this is only the second study to investigate working memory in SPD using fMRI.

METHODS

In a block-design fMRI study, fifteen antipsychotic-naïve SPD and sixteen healthy control subjects performed blocks of a 2back visual working memory task and 0back continuous performance task while undergoing whole-brain fMRI at 3T. Whole-brain analyses were performed for the 0back>rest (fixation baseline) and the 2back>0back contrasts (isolating the working memory component from the visual perception and attention component). Parameter estimates were extracted to determine whether observed differences were due to task-induced activation and/or deactivation.

RESULTS

Activation differences emerged between the two groups, without differences in task performance. In the 0back task, SPD showed decreased task-induced activation of the left postcentral gyrus. In the 2back>0back contrast, HC showed greater task-induced activation of the left posterior cingulate gyrus, superior temporal gyrus, insula, and middle frontal gyrus. These differences were due to SPD subjects' decreased task-induced activation in the left posterior cingulate gyrus, and task-induced deactivation in the remaining regions.

CONCLUSIONS

These findings suggest that compared to HC subjects, individuals with SPD may achieve comparable working memory performance. However, differences emerge at the level of functional neural activation, attributable to different task-induced activation and deactivation patterns. Such differential recruitment of neural resources may be beneficial, contributing to SPD subjects' ability to perform these tasks comparably to HC subjects.

Working memory capacity and psychotic-like experiences in a general population sample of adolescents and young adults

Working memory (WM) impairment is a common feature in individuals with schizophrenia and high-risk for psychosis and a promising target for early intervention strategies. However, it is unclear to what extent WM impairment parallels specific behavioral symptoms along the psychosis continuum. To address this issue, the current study investigated the relation of WM capacity with psychotic-like experiences (PLEs) in a large Swedish population sample (N = 1012) of adolescents and young adults (M = 24.4 years, range 12-35). WM was assessed with two online computer tasks: a task where participants had to identify and remember the location of an odd shape and a task of remembering and following instructions. PLE scores were derived from a translated symptom questionnaire (Community Assessment of Psychic Experiences), which includes positive, negative, and depressive symptom scales. Positive and negative symptom scales were further subdivided into symptom clusters based on factor analyses. The results showed that low WM capacity was modestly associated with increased reports of bizarre experiences (BE) and depressive symptoms, after controlling for age, gender, and global symptom scores. Interestingly, when analyses were repeated for separate age groups, low WM was exclusively associated with a higher frequency of BE for young adults (20-27 years) and with depressive symptoms for older adults (28-35 years). These findings suggest that specific PLEs can be indicative of reduced WM capacity in early adulthood, which in turn may reflect an increased risk for psychosis and a greater need for targeted intervention. In contrast, during adolescence individual differences in cognitive development may influence the strength of the relationships and thereby mask potential vulnerabilities for psychopathology.

Neuropsychological effects associated with recreational cocaine use

RATIONALE

Recent evidence suggests that recreational cocaine use is on the increase, with the UK reporting one of the highest levels of use in the EU (EMCDDA 2010). Nevertheless, very few studies have addressed the neuropsychological effects associated with non-dependent recreational cocaine use.

OBJECTIVES

The current study aimed to assess whether recreational cocaine users show neuropsychological deficits on a battery of tests, previously shown to be sensitive to cocaine-dependent and psychosis-prone individuals. Schizotypal traits were also measured.

METHODS

Recreational cocaine users (n = 17) were compared with controls (n = 24) on drug use patterns, the General Health Questionnaire, the Brief Schizotypal Personality Questionnaire (SPQ-B) and four neuropsychological tasks: spatial working memory, intra/extra-dimensional set shifting, the Stocking of Cambridge and the rapid visual processing.

RESULTS

Relative to controls, recreational cocaine users produced significantly more errors on the intra/extra-dimensional set shift task and completed fewer stages, made significantly more six box stage errors on the spatial working memory task, and made significantly more errors and fewer hits, with overall poorer detection rates on the rapid visual processing task. Recreational cocaine users reported significantly higher scores on the cognitive perceptual and disorganised thinking SPQ-B subscales and total SPQ-B scores compared to controls.

CONCLUSIONS

Recreational cocaine users displayed impairments on tasks tapping sustained attention, attentional shifting and spatial memory and reported higher schizotypal trait expression. These findings are consistent with the emerging literature suggesting subtle cognitive deficits, putatively reflecting underlying dopaminergic dysfunction, in non-dependent, recreational cocaine users.