Decomposing perseverative errors among undergraduates scoring high on the Schizotypal Personality Questionnaire

Context-Specificity of Locomotor Learning Is Developed during Childhood

Humans can perform complex movements with speed and agility in the face of constantly changing task demands. To accomplish this, motor plans are adapted to account for errors in our movements because of changes in our body (e.g., growth or injury) or in the environment (e.g., walking on sand vs ice). It has been suggested that adaptation that occurs in response to changes in the state of our body will generalize across different movement contexts and environments, whereas adaptation that occurs with alterations in the external environment will be context-specific. Here, we asked whether the ability to form generalizable versus context-specific motor memories develops during childhood. We performed a cross-sectional study of context-specific locomotor adaptation in 35 children (3-18 years old) and 7 adults (19-31 years old). Subjects first adapted their gait and learned a new walking pattern on a split-belt treadmill, which has two belts that move each leg at a different speed. Then, subjects walked overground to assess the generalization of the adapted walking pattern across different environments. Our results show that the generalization of treadmill after-effects to overground walking decreases as subjects' age increases, indicating that age and experience are critical factors regulating the specificity of motor learning. Our results suggest that although basic locomotor patterns are established by two years of age, brain networks required for context-specific locomotor learning are still being developed throughout youth.

Language proficiency does not modulate executive control in older bilinguals

We examined if language proficiency modulates performance in tasks that measure executive control in older Telugu-English bilinguals (n = 50, mean age = 57.15 years). We administered numerical Stroop task, Attention Network Task, Dimensional Change Card Sorting task, and stop-signal task that are known to tap into different aspects of executive functioning on healthy aging Telugu-English bilinguals. Second language (English) proficiency was calculated as a cumulative score that considered both subjective and objective measures of L2 fluency and use. Bilinguals were divided into two groups based on the cumulative score and compared on each task. We did not find any effect of language proficiency on any of the executive control measures. The additional Bayesian analysis also supported these findings. Therefore, the results do not support the claim that bilingual language proficiency modulates executive control, at least in the elderly population. We discuss the results with regard to the issue of bilingual advantage in executive control and the role of age and language use.

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.

Evaluation of association of common variants in HTR1A and HTR5A with schizophrenia and executive function

The 5-HT1A receptor (HTR1A) and the 5-HT5A receptor (HTR5A) are key 5-HT receptors with distinct inhibitory functions. Studies have been conducted to investigate the association of a few HTR1A polymorphisms with schizophrenia, producing conflicting results, and the relationship between HTR5A and schizophrenia has not yet been well investigated. We aimed to examine the association of HTR1A and HTR5A with schizophrenia and executive function. The study included a discovery stage with 1,115 patients and 2,289 controls and a replication stage with 2,128 patients and 3,865 controls. A total of 30 common SNPs in HTR1A and HTR5A were genotyped in the discovery stage, and significantly associated SNPs were genotyped in the replication stage. We identified that two SNPs (rs878567 in HTR1A and rs1800883 in HTR5A) were significantly associated with schizophrenia in both datasets, and similar results were observed in imputation and haplotype association analyses. Moreover, we found that SNP rs1800883 significantly interacted with executive function when processing the perseverative error of Wisconsin Card Sorting Test in patients. Our results provide further supportive evidence of the effect of HTR1A and HTR5A on the etiology of schizophrenia and suggest that the selected genetic variations in HTR5A may be involved in impaired executive function.

Common variants in SLC1A2 and schizophrenia: Association and cognitive function in patients with schizophrenia and healthy individuals

SLC1A2 is reported to be responsible for the majority of glutamate uptake, which has a crucial role in neural development and synaptic plasticity, and a disturbance in glutamatergic transmission has been suggested to be involved in the pathophysiology of schizophrenia (SCZ) and cognition. To evaluate the relationship of common variants within SLC1A2 with SCZ and cognition in Han Chinese, 28 tag SNPs were genotyped in the discovery stage, which included 1117 cases and 2289 controls; significantly associated markers were genotyped in the replication stage with 2128 cases and 3865 controls. The rs4354668 SNP was identified to be significantly associated with SCZ in both datasets, and a similar pattern was also observed in the two-stage study on conducting imputation and haplotype association analyses. In addition, significant associations between the rs4354668 SNP and cognition were observed when processing the perseverative error of the Wisconsin Card Sorting Test in patients and controls. Our results provide supportive evidence for an effect of SLC1A2 on the etiology of SCZ, suggesting that genetic variation (rs4354668 and its haplotypes) in SLC1A2 may be involved in impaired executive function, which adds to the current body of knowledge regarding the risk of SCZ and the impairment of cognitive performance.

Prefronto-striatal physiology is associated with schizotypy and is modulated by a functional variant of DRD2

“Schizotypy” is a latent organization of personality related to the genetic risk for schizophrenia. Some evidence suggests that schizophrenia and schizotypy share some biological features, including a link to dopaminergic D2 receptor signaling. A polymorphism in the D2 gene (DRD2 rs1076560, guanine > thymine (G > T)) has been associated with the D2 short/long isoform expression ratio, as well as striatal dopamine signaling and prefrontal cortical activity during different cognitive operations, which are measures that are altered in patients with schizophrenia. Our aim is to determine the association of schizotypy scores with the DRD2 rs1076560 genotype in healthy individuals and their interaction with prefrontal activity during attention and D2 striatal signaling. A total of 83 healthy subjects were genotyped for DRD2 rs1076560 and completed the Schizotypal Personality Questionnaire (SPQ). Twenty-six participants underwent SPECT with [¹²³I]IBZM D2 receptor radiotracer, while 68 performed an attentional control task during fMRI. We found that rs1076560 GT subjects had greater SPQ scores than GG individuals. Moreover, the interaction between schizotypy and the GT genotype predicted prefrontal activity and related attentional behavior, as well as striatal binding of IBZM. No interaction was found in GG individuals. These results suggest that rs1076560 GT healthy individuals are prone to higher levels of schizotypy, and that the interaction between rs1076560 and schizotypy scores modulates phenotypes related to the pathophysiology of schizophrenia, such as prefrontal activity and striatal dopamine signaling. These results provide systems-level qualitative evidence for mapping the construct of schizotypy in healthy individuals onto the schizophrenia continuum.

Poorer Wisconsin card-sorting test performance in healthy adults with higher positive and negative schizotypal traits

Non-clinical schizotypy was found to be related to poorer Wisconsin Card-Sorting Test (WCST) performance, but the results were inconsistent. Two subgroups, the higher negative-higher positive and the lower negative-lower positive (15 vs 16), were selected from the top and the bottom quartiles of negative and positive scale scores of the Schizotypal Personality Questionnaire (SPQ) completed by 177 healthy volunteers, respectively. The higher negative-higher positive SPQ score subgroup had significantly poorer performance regarding the completed categories of WCST than the lower negative-lower positive SPQ score subgroup. Subjects with higher non-clinical schizotypy trait showed relatively mild cognitive dysfunction.

Schizotypal traits and N400 in healthy subjects

We examined whether correlations previously found between symptoms of schizophrenia patients and the amplitude of an event-related potential (ERP), the N400, could be also found between schizotypal experiences of healthy subjects and the N400. We chose a semantic categorization task previously used with patients. Schizotypal experiences were measured with the schizotypal personality questionnaire (SPQ). The effects of the other factors were controlled for when assessing the correlations between each SPQ factor and N400s. These correlations were assessed at each electrode site to see whether their distribution on the scalp follows that of the N400 effect. Disorganization and interpersonal scores were found to correlate with ERPs in the N400 time window, as previously reported for the comparable symptoms of patients. However, the scalp distribution of these correlations differed from that of the N400 effect.

Association between genetic variants of the metabotropic glutamate receptor 3 (GRM3) and cognitive set shifting in healthy individuals

Set-shifting and maintenance are complex cognitive processes, which are often impaired in schizophrenia. The genetic basis of these processes is poorly understood. We aimed to investigate the association between genetic variants of the metabotropic glutamate receptor 3 (GRM3) and cognitive set-shifting in healthy individuals. The relationship between 14 selected single nucleotide polymorphisms (SNPs) of the GRM3 gene and cognitive set-shifting as measured by perseverative errors using the modified card sorting test (MCST) was analysed in a sample of N = 98 young healthy individuals (mean age in years: 22.7 +/- 0.19). Results show that SNP rs17676277 is related to the performance on the MCST. Subjects with the TT genotype showed significantly less perseverative errors as compared with the AA (P = 0.025) and AT (P = 0.0005) and combined AA/AT genotypes (P = 0.0005). Haplotype analyses suggest the involvement of various SNPs of the GRM3 gene in perseverative error processing in a dominant model of inheritance. The findings strongly suggest that the genetic variation (rs17676277 and three haplotypes) in the metabotropic GRM3 is related to cognitive set-shifting in healthy individuals independent of working memory. However, because of a relatively small sample size for a genetic association study, the present results are tentative and require replication.

Validation of the Schizotypal Personality Questionnaire-Brief Form in adolescents

The main objective of the study was to validate the Schizotypal Personality Questionnaire-Brief (SPQ-B) in a sample of non-clinical adolescents. In addition, the schizotypal personality structure and differences in the dimensions of schizotypy according to gender and age are analyzed. The sample comprises 1683 students, 818 males (48.6%), with a mean age of 15.9 years (SD=1.2). The results showed that the SPQ-B had adequate psychometric properties. Internal consistency of the subscales and total score ranged from 0.61 to 0.81. Confirmatory factor analyses indicated that the three-factor model (positive, negative, and disorganized) and the four-factor model (positive, paranoid, negative, and disorganized) fit reasonably well in comparison to the remaining models. With regard to gender and age, statistically significant differences were found due to age but not to gender. In line with previous literature, the results confirmed the multi-factor structure of the schizotypal personality in non-clinical adolescent populations. Future studies could use the SPQ-B as a screening self-report of rapid and efficient application for the detection of adolescents vulnerable to the development of schizophrenia-spectrum disorders in the general population, in genetically high-risk samples and in clinical studies.