Sustained attention and working memory deficits follow a familial pattern in schizophrenia

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.

Growth trajectories for executive and social cognitive abilities in an Indian population sample: Impact of demographic and psychosocial determinants

Cognitive abilities are markers of brain development and psychopathology. Abilities, across executive, and social domains need better characterization over development, including factors that influence developmental change. This study is based on the cVEDA [Consortium on Vulnerability to Externalizing Disorders and Addictions] study, an Indian population based developmental cohort. Verbal working memory, visuo-spatial working memory, response inhibition, set-shifting, and social cognition (faux pas recognition and emotion recognition) were cross-sectionally assessed in > 8000 individuals over the ages 6-23 years. There was adequate representation across sex, urban-rural background, psychosocial risk (psychopathology, childhood adversity and wealth index, i.e. socio-economic status). Quantile regression was used to model developmental change. Age-based trajectories were generated, along with examination of the impact of determinants (sex, childhood adversity, and wealth index). Development in both executive and social cognitive abilities continued into adulthood. Maturation and stabilization occurred in increasing order of complexity, from working memory to inhibitory control to cognitive flexibility. Age related change was more pronounced for low quantiles in response inhibition (β∼4 versus  -1 versus -0.25 for lower quantiles). Wealth index had the largest influence on developmental change across cognitive abilities. Sex differences were prominent in response inhibition, set-shifting and emotion recognition. Childhood adversity had a negative influence on cognitive development. These findings add to the limited literature on patterns and determinants of cognitive development. They have implications for understanding developmental vulnerabilities in young persons, and the need for providing conducive socio-economic environments.

Distractor filtering and its electrophysiological correlates in schizophrenia

OBJECTIVE

Patients with schizophrenia are characterized by compromised working memory (WM) performance and increased distractibility. Theta synchronization (especially over the frontal midline areas) is related to cognitive control and executive processes during WM encoding and retention. Alpha event-related desynchronization (ERD) is associated with information processing and attention.

METHODS

Participants (35 patients and 39 matched controls) performed a modified Sternberg WM task, containing salient and non-salient distractor items in the retention period. A high-density 128 channel EEG was recorded during the task. Theta (4-7 Hz) and fast alpha (10-13 Hz) event-related spectral perturbation (ERSP) were analyzed during the retention and encoding period.

RESULTS

Patients with schizophrenia showed worse WM performance and increased attentional distractibility in terms of lower hit rates and increased distractor-related commission errors compared to healthy controls. Theta synchronization was modulated by condition (learning vs. distractor) in both groups but it was modulated by salience only in controls. Furthermore, salience of distractors modulated less the fast alpha ERD in patients.

CONCLUSIONS

Our results suggest that patients with schizophrenia process salient and non-salient distracting information less efficiently and show weaker cognitive control compared to controls.

SIGNIFICANCE

These differences may partly account for diminished WM performance and increased distractibility in schizophrenia.

Study of differences between patients with schizophrenia and healthy people in semantic processing

Semantic processing is important in language comprehension and production, and context can facilitate understanding and accelerate processing speed by pre-activating semantically related words. There are many studies suggesting that patients with schizophrenia have inferior language ability. This study was aimed to examine the differences between patients with schizophrenia and healthy people in semantic processing with Chinese classifier-noun pairs rating tasks. Participants were required to finish rating tasks to judge acceptability of classifier-noun pairs. Also, the Positive and Negative Syndrome Scale (PANSS) was conducted in the schizophrenia group. According to results of variance analysis, schizophrenic patients' accuracy of judgment on the acceptability of classifier-noun pairs differed from the control group (F = 4.13, p < .05), and the contextual effect of classifier constraint could be observed in healthy people (F(1, 31) = 5.38, p < .05) but not in patients with schizophrenia (F(1, 25) = 3.55, p = .07), indicating that they failed to use the contextual information to facilitate language comprehension as healthy people. Stepwise linear regression analysis found that hostility, poor impulse control and suspiciousness/persecution and preoccupation in the PANSS may have contributed to the reduced sensitivity in the rating in patients (t = -2.38-3.80, p < .05).

Divided Attention in Schizophrenia: A Dual Task Paradigm

Schizophrenia is known to be associated with attentional deficits. Few studies have examined whether the disorder is also associated with a deficit in the ability to divide attention, and they have given contradictory results. Some have reported that patients show greater loss of performance than healthy controls when moving from single tasks to dual tasks, and others have reported that performance loss is similar in both groups or even that patients perform the dual task better than either task on its own. To help resolve this controversy, we performed a first study in which we designed a dual task paradigm with a group of 36 healthy participants. This dual task involves 2 tasks of equivalent difficulty that make use of different sensory modalities. In the second study, we gave this dual task to 23 patients with schizophrenia and 25 healthy participants. Both groups decreased similarly their performance in dual tasks, but the patients showed lower baseline performance in the single task. Our findings suggest that patients with schizophrenia and healthy participants use similar strategies to divide their attention, but in a high-degrading stimuli condition patients perform below the controls in a single task.

Translation-Focused Approaches to GPCR Drug Discovery for Cognitive Impairments Associated with Schizophrenia

There are no effective therapeutics for cognitive impairments associated with schizophrenia (CIAS), which includes deficits in executive functions (working memory and cognitive flexibility) and episodic memory. Compounds that have entered clinical trials are inadequate in terms of efficacy and/or tolerability, highlighting a clear translational bottleneck and a need for a cohesive preclinical drug development strategy. In this review we propose hippocampal-prefrontal-cortical (HPC-PFC) circuitry underlying CIAS-relevant cognitive processes across mammalian species as a target source to guide the translation-focused discovery and development of novel, procognitive agents. We highlight several G protein-coupled receptors (GPCRs) enriched within HPC-PFC circuitry as therapeutic targets of interest, including noncanonical approaches (biased agonism and allosteric modulation) to conventional clinical targets, such as dopamine and muscarinic acetylcholine receptors, along with prospective novel targets, including the orphan receptors GPR52 and GPR139. We also describe the translational limitations of popular preclinical cognition tests and suggest touchscreen-based assays that probe cognitive functions reliant on HPC-PFC circuitry and reflect tests used in the clinic, as tests of greater translational relevance. Combining pharmacological and behavioral testing strategies based in HPC-PFC circuit function creates a cohesive, translation-focused approach to preclinical drug development that may improve the translational bottleneck currently hindering the development of treatments for CIAS.

Cognition in offspring of parents with psychotic and non-psychotic severe mental illness

BACKGROUND

Cognitive impairment is a feature of severe mental illness (SMI; schizophrenia, bipolar disorder, major depressive disorder). Psychotic forms of SMI may be associated with greater cognitive impairment, but it is unclear if this differential impairment pre-dates illness onset or whether it reflects a consequence of the disorder. To establish if there is a developmental impairment related to familial risk of psychotic SMI, we investigated cognition in offspring of parents with psychotic and non-psychotic SMI.

METHOD

Participants included 360 children and youth (mean age 11.10, SD 4.03, range 6-24), including 68 offspring of parents with psychotic SMI, 193 offspring of parents with non-psychotic SMI, and 99 offspring of control parents. The cognitive battery assessed a range of functions using standardized tests and executive function tasks from the Cambridge Automated Neuropsychological Test Battery.

RESULTS

Compared to controls, offspring of parents with psychotic SMI performed worse on overall cognition (β = -0.32; p < 0.001) and 6 of 15 cognitive domains, including verbal intelligence, verbal working memory, processing speed, verbal learning and memory, verbal fluency, and sustained attention. Offspring of parents with non-psychotic SMI performed worse than controls on 3 of the 15 domain specific cognitive tests, including verbal intelligence, visual memory and decision-making.

CONCLUSIONS

Widespread mild-to-moderate cognitive impairments are present in young offspring at familial risk for transdiagnostic psychotic SMI. Offspring at familial risk for non-psychotic SMI showed fewer and more specific impairments in the domains of verbal intelligence, visual memory and decision-making.

The psycho-periodic cube

The current diagnostic classification systems in psychiatry have been developed primarily for evidence-based clinical decision making with both categorical and dimensional approaches having their own advantages and disadvantages. Efforts have been made to improve these classification systems, and we are now at the point where we must expand beyond the one-dimensionality of these systems. In this paper, we propose that psychiatric disorders can be arranged in a three-dimensional classification system according to the degree of dysfunctions on three specific axes in a way that is similar to the arrangement of chemical elements according to their atomic weights in Mendeleyev's periodic table. For the three axes, we chose externalization, drive, and attention to represent the three-dimensional descriptions of mental health, namely, well-being in social, motivational, and cognitive areas, respectively. Throughout the paper, we explain our reasons for choosing these three axes and compare our hypothesis with categorical diagnostic systems as well as Cloninger's dimensional diagnostic system using personality disorders, affective disorders, and schizophrenia as the specific diagnostic samples.

Sustaining attention to simple visual tasks: a central deficit in schizophrenia? A systematic review

Impairments in sustained attention, that is, the ability to achieve and maintain the focus of cognitive activity on a given stimulation source or task, have been described as central to schizophrenia. Today, sustained attention deficit is still considered as a hallmark of schizophrenia. Nevertheless, current findings on this topic are not consistent. To clarify these findings, we attempt to put these results into perspective according to the type of assessment (i.e., overall and over time assessment), the participants' characteristics (i.e., clinical and demographic characteristics), and the paradigms (i.e., traditionally formatted tasks, go/no-go tasks, and the sustained attention task) and measures used. Two types of assessment lead to opposite findings; they do not evaluate sustained attention the same way. Studies using overall assessments of sustained attention ability tend to reveal a deficit, whereas studies using over time assessments do not. Therefore, further research is needed to investigate the underlying cognitive control mechanisms of changes in sustained attention in schizophrenia.

Neurocognitive performance, psychopathology and social functioning in individuals at high risk for schizophrenia or psychotic bipolar disorder

INTRODUCTION

Although cognitive deficits are consistent endophenotypes of schizophrenia and bipolar disorder, findings in psychotic bipolar disorder (BDP) are inconsistent. In this study we compared adult unaffected first-degree relatives of schizophrenia and BDP patients on cognition, psychopathology, social functioning and quality of life.

METHODS

Sixty-six unaffected first-degree relatives of schizophrenia patients (SUnR), 36 unaffected first-degree relatives of BDP patients (BDPUnR) and 102 controls participated in the study. Between-group differences were examined and Discriminant Function Analysis (DFA) predicted group membership.

RESULTS

Visual memory, control inhibition, working memory, cognitive flexibility and abstract reasoning were linearly impaired in the relatives' groups. Poorer verbal fluency and processing speed were evident only in the SUnR group. The SUnR group had higher depressive and somatization symptoms while the BDPUnR group had higher anxiety and lower social functioning compared with the controls. Individuals with superior cognition were more likely to be classified as controls; those with higher social functioning, prolonged processing speed and lower anxiety were more likely to be classified as SUnR.

LIMITATIONS

The relatives' sample is quite heterogeneous; the effects of genetic or environmental risk-factors were not examined.

CONCLUSIONS

Cognitive functions mediated by a fronto-parietal network, show linear impairments in unaffected relatives of BDP and schizophrenia patients; processing speed and verbal fluency impairments were evident only in schizophrenia relatives. Self-perceived symptomatology and social functioning also differ between schizophrenia and BDP relatives. The continuum seen in patients in several indices was also seen in the cognitive impairments in unaffected relatives of schizophrenia and BDP patients.

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.

Performance of Verbal Fluency as an Endophenotype in Patients with Familial versus Sporadic Schizophrenia and Their Parents

What’s the neurocognitive deficit as an endophenotype to familial schizophrenia? Here, we investigate the neurocognitive endophenotype in first-episode patients with familial schizophrenia (FS) and sporadic schizophrenia (SS), and their parents. 98 FS patients and their 105 parents; 190 SS patients and their 207 parents; 195 controls matched with patients, and 190 controls matched with the patients’ parents, were assessed with the short version of the Wechsler Adult Intelligence Scale-Revised in China (WAIS-RC), the immediate and delayed logical memory tests from the Wechsler Memory Scale-Revised in China (WMS-RC), the Verbal Fluency Test (VFT), the Trail Making Test Parts A and B-Modified (TMA, TMB-M), and the Modified Wisconsin Card Sorting Test (WCST-M). The results showed that with age, gender, and education as covariates, after controlling for false discovery rates, the FS group and their parent group performed worse than the SS group and their parent group on VFT. No significant differences were found for other neurocognitive tests between the FS and SS patient groups, and their respective parent groups. Our findings suggest the patients with familial and sporadic schizophrenia and their respective parent groups may have a different genetic predisposition in relation to a cognitive endophenotype.

Behavioral response inhibition in psychotic disorders: diagnostic specificity, familiality and relation to generalized cognitive deficit

Difficulty inhibiting context-inappropriate behavior is a common deficit in psychotic disorders. The diagnostic specificity of this impairment, its familiality, and its degree of independence from the generalized cognitive deficit associated with psychotic disorders remain to be clarified. Schizophrenia, schizoaffective and bipolar patients with history of psychosis (n=523), their available first-degree biological relatives (n=656), and healthy participants (n=223) from the multi-site B-SNIP study completed a manual Stop Signal task. A nonlinear mixed model was used to fit logistic curves to success rates on Stop trials as a function of parametrically varied Stop Signal Delay. While schizophrenia patients had greater generalized cognitive deficit than bipolar patients, their deficits were similar on the Stop Signal task. Further, only bipolar patients showed impaired inhibitory control relative to healthy individuals after controlling for generalized cognitive deficit. Deficits accounted for by the generalized deficit were seen in relatives of schizophrenia and schizoaffective patients, but not in relatives of bipolar patients. In clinically stable patients with psychotic bipolar disorder, impaired inhibitory behavioral control was a specific cognitive impairment, distinct from the generalized neuropsychological impairment associated with psychotic disorders. Thus, in bipolar disorder with psychosis, a deficit in inhibitory control may contribute to risk for impulsive behavior. Because the deficit was not familial in bipolar families and showed a lack of independence from the generalized cognitive deficit in schizophrenia spectrum disorders, it appears to be a trait related to illness processes rather than one tracking familial risk factors.

Sustained attention in psychosis: Neuroimaging findings

To provide a systematic review of scientific literature on functional magnetic resonance imaging (fMRI) studies on sustained attention in psychosis. We searched PubMed to identify fMRI studies pertaining sustained attention in both affective and non-affective psychosis. Only studies conducted on adult patients using a sustained attention task during fMRI scanning were included in the final review. The search was conducted on September 10^th, 2013. 15 fMRI studies met our inclusion criteria: 12 studies were focused on Schizophrenia and 3 on Bipolar Disorder Type I (BDI). Only half of the Schizophrenia studies and two of the BDI studies reported behavioral abnormalities, but all of them evidenced significant functional differences in brain regions related to the sustained attention system. Altered functioning of the insula was found in both Schizophrenia and BDI, and therefore proposed as a candidate trait marker for psychosis in general. On the other hand, other brain regions were differently impaired in affective and non-affective psychosis: alterations of cingulate cortex and thalamus seemed to be more common in Schizophrenia and amygdala dysfunctions in BDI. Neural correlates of sustained attention seem to be of great interest in the study of psychosis, highlighting differences and similarities between Schizophrenia and BDI.

The global cognitive impairment in schizophrenia: consistent over decades and around the world

OBJECTIVE

Schizophrenia results in cognitive impairments as well as positive, negative, and disorganized symptomatology. The present study examines the extent to which these cognitive deficits are generalized across domains, potential moderator variables, and whether the pattern of cognitive findings reported in schizophrenia has remained consistent over time and across cultural and geographic variation.

METHOD

Relevant publications from 2006 to 2011 were identified through keyword searches in PubMed and an examination of reference lists. Studies were included if they (1) compared the cognitive performance of adult schizophrenia patients and healthy controls, (2) based schizophrenia diagnoses on contemporary diagnostic criteria, (3) reported information sufficient to permit effect size calculation, (4) were reported in English, and (5) reported data for neuropsychological tests falling into at least 3 distinct cognitive domains. A set of 100 non-overlapping studies was identified, and effect sizes (Hedge's g) were calculated for each cognitive variable.

RESULTS

Consistent with earlier analyses, patients with schizophrenia scored significantly lower than controls across all cognitive tests and domains (grand mean effect size, g=-1.03). Patients showed somewhat larger impairments in the domains of processing speed (g=-1.25) and episodic memory (g=-1.23). Our results also showed few inconsistencies when grouped by geographic region.

CONCLUSIONS

The present study extends findings from 1980 to 2006 of a substantial, generalized cognitive impairment in schizophrenia, demonstrating that this finding has remained robust over time despite changes in assessment instruments and alterations in diagnostic criteria, and that it manifests similarly in different regions of the world despite linguistic and cultural differences.

Discrimination within Recognition Memory in Schizophrenia

Episodic memory is one of the most affected cognitive domains in schizophrenia. First-degree biological relatives of individuals with schizophrenia also have been found to exhibit a similar, but milder, episodic memory deficit. Unlike most studies that focus on the percent of previously presented items recognized, the current investigation sought to further elucidate the nature of memory dysfunction associated with schizophrenia by examining the discrimination of old and new material during recognition (measured by d') to consider false recognition of new items. Using the Recurring Figures Test and the California Verbal Learning Test (CVLT), we studied a sample of schizophrenia probands and the first-degree biological relatives of patients with schizophrenia, as well as probands with bipolar disorder and first-degree biological relatives to assess the specificity of recognition memory dysfunction to schizophrenia. The schizophrenia sample had poorer recognition discrimination in both nonverbal and verbal modalities; no such deficits were identified in first-degree biological relatives or bipolar disorder probands. Discrimination in schizophrenia and bipolar probands failed to benefit from the geometric structure in the designs in the manner that controls did on the nonverbal test. Females performed better than males in recognition of geometric designs. Episodic memory dysfunction in schizophrenia is present for a variety of stimulus domains and reflects poor use of item content to increase discrimination of old and new items.

Less cognitive and neurological deficits in schizophrenia patients carrying risk variant in ZNF804A

BACKGROUND

The rs1344706 single nucleotide polymorphism in the ZNF804A gene is a common variant with strong evidence for association with schizophrenia. Recent studies show an association of rs1344706 with cognitive functioning, and there is some evidence suggesting that the risk allele may increase susceptibility for a subtype of schizophrenia with relatively spared cognition.

METHODS

We tested the effect of rs1344706 genotype in 89 schizophrenia patients on 3 basic cognitive domains (working memory, processing speed and attention) shown to be severely impaired in schizophrenia. Also we investigated the effect of rs1344706 on the severity of neurological soft signs, subtle impairments in motor and sensory functions highly frequent in schizophrenia patients. Neurological soft signs and cognitive deficits are central features of schizophrenia and are tightly linked with clinical, social and functional outcome.

RESULTS

Our results show an association of higher rs1344706 risk allele load with improved performance on processing speed and with fewer neurological soft signs.

CONCLUSIONS

Together with other studies, our findings suggest that ZNF804A is associated with a subtype of schizophrenia with better cognitive and neurological functioning. Discovery of the specific pathways through which ZNF804A is exerting this effect may lead to better prevention, diagnosis and treatment for a specific group of schizophrenia patients.

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.