The Wisconsin Card Sorting impairment in schizophrenia is evident in the first four trials

Frontal brain volume correlates of impaired executive function in schizophrenia

Cognitive impairments affect functional capacity in individuals with schizophrenia (SZH), but their neural basis remains unclear. The Wisconsin Card Sorting Test (WCST), and the Stroop Task (SCWT), are paradigmatic tests which have been used extensively for examining executive function in SZH. However, few studies have explored how deficits on these tasks link to brain volume differences commonly seen in SZH. Here, for the first time, we tested associations between FreeSurfer-derived frontal brain volumes and performance on both WCST and SCWT, in a well-matched sample of 57 SZH and 32 control subjects. We also explored whether these associations were dissociable from links to symptom severity in SZH. Results revealed correlations between volumes and task performance which were unique to SZH. In SZH only, volumes of right middle frontal regions correlated with both WCST and Stroop performance: correlation coefficients were significantly different to those present in the control group, highlighting their specificity to the patient group. In the Stroop task, superior frontal regions also showed associations with Stroop interference scores which were unique to SZH. These findings provide important detail around how deficits on these two paradigmatic executive function tasks link to brain structural differences in SZH. Results align with converging evidence suggesting that neuropathology within right middle frontal regions (BA9 and BA46) might be of particular import in SZH. No volumetric associations with symptom severity were found, supporting the notion that the structural abnormalities underpinning cognitive deficits in SZH differ from those associated with symptomatology.

A meta-cognitive Wisconsin Card Sorting Test in people with schizophrenia and bipolar disorder: Self-assessment of sorting performance

People with serious mental illness have challenged self-awareness, including momentary monitoring of performance. A core feature of this challenge is in the domain of using external information to guide behavior, an ability that is measured very well by certain problem-solving tasks such as the Wisconsin Card Sorting Test (WCST) . We used a modified WCST to examine correct sorts and accuracy decisions regarding the correctness of sort. Participants with schizophrenia (n = 99) or bipolar disorder (n = 76) sorted 64 cards and then made judgments regarding correctness of each sort prior to feedback. Time series analyses examined the course of correct sorts and correct accuracy decisions by examining the momentary correlation and lagged correlation on the next sort. People with schizophrenia had fewer correct sorts, fewer categories, and fewer correct accuracy decisions (all p<.001). Positive response biases were seen in both groups. After an incorrect sort or accuracy decision, the groups were equally likely to be incorrect on the next sort or accuracy decision. Following correct accuracy decisions, participants with bipolar disorder were significantly (p=.003) more likely to produce a correct sort or accuracy decision. These data are consistent with previous studies implicating failures to consider external feedback for decision making. Interventions aimed at increasing consideration of external information during decision making have been developed and interventions targeting use of feedback during cognitive test performance are in development.

Associative learning and facial expression recognition in schizophrenic patients: Effects of social presence

Schizophrenia (SCZ) is a psychiatric disorder that alters both general and social cognition. However, the exact mechanisms that are altered remain to be elucidated. In this study, we investigated associative learning (AL) and facial expression recognition (FER) in the same patients, using emotional expressions and abstract images. Our main aim was to investigate how these cognitive abilities are affected by SCZ and to assess the role of mere social presence, a factor that has not been considered before. The study compared the behavioral performance of 60 treated outpatients with SCZ and 103 demographically matched healthy volunteers. In the AL task, participants had to associate abstract images or facial expressions with key presses, guided by feedback on each trial. In the FER task, they had to report whether two successively presented facial expressions were the same or different. All participants performed the two tasks under two social context conditions: alone or in the presence of a passive but attentive audience. The results showed a severe learning impairment in patients compared to controls, with a slight advantage for facial expressions compared to abstract images, and a gender-dependent effect of social presence. In contrast, facial expression recognition was partially spared in patients and facilitated by social presence. We conclude that cognitive abilities are impaired in patients with SCZ, but their investigation needs to take into account the social context in which they are assessed.

Computerized adaptive test strategies for the matrix reasoning subtest of the Wechsler Adult Intelligence Scale, 4th Edition (WAIS-IV)

OBJECTIVE

Most neuropsychological tests were developed without the benefit of modern psychometric theory. We used item response theory (IRT) methods to determine whether a widely used test - the 26-item Matrix Reasoning subtest of the WAIS-IV - might be used more efficiently if it were administered using computerized adaptive testing (CAT).

METHOD

Data on the Matrix Reasoning subtest from 2197 participants enrolled in the National Neuropsychology Network (NNN) were analyzed using a two-parameter logistic (2PL) IRT model. Simulated CAT results were generated to examine optimal short forms using fixed-length CATs of 3, 6, and 12 items and scores were compared to the original full subtest score. CAT models further explored how many items were needed to achieve a selected precision of measurement (standard error ≤ .40).

RESULTS

The fixed-length CATs of 3, 6, and 12 items correlated well with full-length test results (with r = .90, .97 and .99, respectively). To achieve a standard error of .40 (approximate reliability = .84) only 3-7 items had to be administered for a large percentage of individuals.

CONCLUSIONS

This proof-of-concept investigation suggests that the widely used Matrix Reasoning subtest of the WAIS-IV might be shortened by more than 70% in most examinees while maintaining acceptable measurement precision. If similar savings could be realized in other tests, the accessibility of neuropsychological assessment might be markedly enhanced, and more efficient time use could lead to broader subdomain assessment.

Cognitive flexibility in schizophrenia: A confirmatory factor analysis of neuropsychological measures

Cognitive flexibility (CF) is the ability to adapt cognitive strategies according to the changing environment. The deficit in CF has often been linked to various neurological and psychiatric disorders including schizophrenia. However, the operationalization and assessment of CF have not been unified and the current research suggests that the available instruments measure different aspects of CF. The main objective of the present study was to compare three frequently used neuropsychological measures of CF-Wisconsin Card Sorting Test (WCST), Trail Making Test (TMT) and Stroop Color and Word Test (SCWT) in a population of patients (N = 220) with first-episode schizophrenia spectrum disorders in order to evaluate their convergent validity. The hypothesis of an underlying latent construct was tested via a confirmatory factor analysis. We used a one-factor CF model with scores from WCST, SCWT and TMT as observed variables. The established model showed a good fit to the data (χ² = 1.67, p = 0.43, SRMR = 0.02, RMSEA = 0.0, CFI = 1.00). The highest factor loading was found in WCST as CF explained most of the variance in this neuropsychological measure compared to the other instruments. On the other hand, a TMT ratio index and a SCWT interference demonstrated lowest loadings in the model. The findings suggest that not all the frequently used measures share an underlying factor of CF or may capture different aspects of this construct.

Assessing cognitive flexibility in humans and rhesus macaques with visual motion and neutral distractors

Introduction

Cognitive flexibility is the ability of an individual to make behavioral adjustments in response to internal and/or external changes. While it has been reported in a wide variety of species, established paradigms to assess cognitive flexibility vary between humans and non-human animals, making systematic comparisons difficult to interpret.

Methods

We developed a computer-based paradigm to assess cognitive flexibility in humans and non-human primates. Our paradigm (1) uses a classical reversal learning structure in combination with a set-shifting approach (4 stimuli and 3 rules) to assess flexibility at various levels; (2) it employs the use of motion as one of three possible contextual rules; (3) it comprises elements that allow a foraging-like and random interaction, i.e., instances where the animals operate the task without following a strategy, to potentially minimize frustration in favor of a more positive engagement.

Results and Discussion

We show that motion can be used as a feature dimension (in addition to commonly used shape and color) to assess cognitive flexibility. Due to the way motion is processed in the primate brain, we argue that this dimension is an ideal candidate in situations where a non-binary rule set is needed and where participants might not be able to fully grasp other visual information of the stimulus (e.g., quantity in Wisconsin Card Sorting Test). All participants in our experiment flexibly shifted to and from motion-based rules as well as color- and shape-based rules, but did so with different proficiencies. Overall, we believe that with such approach it is possible to better characterize the evolution of cognitive flexibility in primates, as well as to develop more efficient tools to diagnose and treat various executive function deficits.

Computational reinforcement learning, reward (and punishment), and dopamine in psychiatric disorders

In the DSM-5, psychiatric diagnoses are made based on self-reported symptoms and clinician-identified signs. Though helpful in choosing potential interventions based on the available regimens, this conceptualization of psychiatric diseases can limit basic science investigation into their underlying causes. The reward prediction error (RPE) hypothesis of dopamine neuron function posits that phasic dopamine signals encode the difference between the rewards a person expects and experiences. The computational framework from which this hypothesis was derived, temporal difference reinforcement learning (TDRL), is largely focused on reward processing rather than punishment learning. Many psychiatric disorders are characterized by aberrant behaviors, expectations, reward processing, and hypothesized dopaminergic signaling, but also characterized by suffering and the inability to change one's behavior despite negative consequences. In this review, we provide an overview of the RPE theory of phasic dopamine neuron activity and review the gains that have been made through the use of computational reinforcement learning theory as a framework for understanding changes in reward processing. The relative dearth of explicit accounts of punishment learning in computational reinforcement learning theory and its application in neuroscience is highlighted as a significant gap in current computational psychiatric research. Four disorders comprise the main focus of this review: two disorders of traditionally hypothesized hyperdopaminergic function, addiction and schizophrenia, followed by two disorders of traditionally hypothesized hypodopaminergic function, depression and post-traumatic stress disorder (PTSD). Insights gained from a reward processing based reinforcement learning framework about underlying dopaminergic mechanisms and the role of punishment learning (when available) are explored in each disorder. Concluding remarks focus on the future directions required to characterize neuropsychiatric disorders with a hypothesized cause of underlying dopaminergic transmission.

Psychometric Properties of Two Tasks in the Allen Cognitive Level Screen-Sixth Edition for Community-Dwelling People Living With Schizophrenia

IMPORTANCE

Empirical evidence is needed on the psychometric properties of the Allen Cognitive Level Screen-Sixth Edition (ACLS-6), an instrument that assesses cognitive functions and is commonly used for people living with schizophrenia.

OBJECTIVE

To examine the convergent validity, discriminative validity, and test-retest reliability of two tasks, stitching and copying, in the ACLS-6 for community-dwelling people living with schizophrenia.

DESIGN

Prospective observational study.

SETTING

Psychiatric center.

PARTICIPANTS

110 people living with schizophrenia.

OUTCOMES AND MEASURES

To examine convergent validity, we calculated correlations (Pearson's r) between the two tasks and between these two tasks and three cognitive measures. We checked for floor and ceiling effects and conducted independent t tests to evaluate discriminative validity. We calculated intraclass correlation coefficients (ICCs) to investigate test-retest reliability.

RESULTS

We found a strong correlation (r = .88) between the two tasks and moderate correlations (rs = .32-.52) between the two tasks and the three cognitive measures. No floor or ceiling effects were observed for the two tasks, and t tests showed significant differences between two participant groups with marginal and mild clinical symptoms (p < .001). The ICC values for the two tasks were .71-.74.

CONCLUSION AND RELEVANCE

The stitching and copying tasks of the ACLS-6 have good convergent validity, discriminative validity, and test-retest reliability for community-dwelling people living with schizophrenia. The copying task showed a strong correlation with the stitching task and a similar score range, so practitioners can consider using the copying task as a substitute for the stitching task. What This Article Adds: The stitching and copying tasks of the ACLS-6 have sound psychometric properties for measuring cognitive functions in community-dwelling people living with schizophrenia.

The instrumental role of operant paradigms in translational psychiatric research: Insights from a maternal immune activation model of schizophrenia risk

Rigorous behavioral analysis is essential to the translation of research conducted using animal models of neuropsychiatric disease. Here we discuss the use of operant paradigms within our lab as a powerful approach for exploring the biobehavioral bases of disease in the maternal immune activation rat model of schizophrenia. We have investigated a range of disease features in schizophrenia including abnormal perception of time, cognition, learning, motivation, and internal state (psychosis), providing complex insights into brain and behavior. Beyond simple phenotyping, implementing sophisticated operant procedures has been effective in delineating aspects of pathological behavior, identifying interacting pathologies, and isolating contributing mechanisms of disease. We provide comment on the strengths of operant techniques to support high-quality behavioral investigations in fundamental neuropsychiatric research.

How Working Memory and Reinforcement Learning Are Intertwined: A Cognitive, Neural, and Computational Perspective

Reinforcement learning and working memory are two core processes of human cognition and are often considered cognitively, neuroscientifically, and algorithmically distinct. Here, we show that the brain networks that support them actually overlap significantly and that they are less distinct cognitive processes than often assumed. We review literature demonstrating the benefits of considering each process to explain properties of the other and highlight recent work investigating their more complex interactions. We discuss how future research in both computational and cognitive sciences can benefit from one another, suggesting that a key missing piece for artificial agents to learn to behave with more human-like efficiency is taking working memory's role in learning seriously. This review highlights the risks of neglecting the interplay between different processes when studying human behavior (in particular when considering individual differences). We emphasize the importance of investigating these dynamics to build a comprehensive understanding of human cognition.

A network analysis and empirical validation of executive deficits in patients with psychosis and their healthy siblings

BACKGROUND

Psychopathological symptoms and cognitive impairment are core features of patients with psychotic disorders. Executive dysfunctions are commonly observed and typically assessed using tests like the Wisconsin Card Sorting Test (WCST). However, the structure of executive deficits remains unclear, and the underlying processes may be different. This study aimed to explore and compare the network structure of WCST measures in patients with psychosis and their unaffected siblings and to empirically validate the resulting network structure of the patients.

METHODS

The subjects were 298 patients with a DSM 5 diagnosis of a psychotic disorder and 89 of their healthy siblings. The dimensionality and network structure of the WCST were examined by means of exploratory graph analysis (EGA) and network centrality parameters.

RESULTS

The WCST network structure comprised 4 dimensions: perseveration (PER), inefficient sorting (IS), failure to maintain set (FMS) and learning (LNG). The patient and sibling groups showed a similar network structure, which was reliably estimated. PER and IS showed common and strong associations with antecedent, concurrent and outcome validators. The LNG dimension was also moderately associated with these validators, but FMS did not show significant associations.

CONCLUSIONS

Four cognitive processes underlying WCST performance were identified by the network analysis. PER, IS and LNG were associated with and shared common antecedent, concurrent and outcome validators, while FMS was not associated with external validators. These four underlying dysfunctions might help disentangle the neurofunctional basis of executive deficits in psychosis.

Using a Meta-cognitive Wisconsin Card Sorting Test to measure introspective accuracy and biases in schizophrenia and bipolar disorder

People with schizophrenia (SCZ) and bipolar disorder (BD) have challenges in self-evaluation of their cognitive and functional performance (introspective accuracy). They also manifest response biases, with tendencies toward overestimation. This study aimed to examine objective test performance, momentary judgments of performance, momentary confidence, and subsequent global judgments of performance on a metacognitive version of the Wisconsin Card Sorting Test (WCST). This sample included 99 participants with SCZ and 67 with BD. After each of the 64 WCST trials, participants reported whether they believed their sort was correct and how confident they were in that judgment, they then received performance feedback. After completion of the entire task, participants generated a global performance judgment. On average, the SCZ group got 31 sorts correct, reporting being correct on 49 whereas the BD group got 37 trials correct but reported being correct on 53. For participants with BD, sorting performance correlated with trial x trial accuracy judgments, confidence, and predicted global judgments. For SCZ participants, performance minimally correlated with trial x trial accuracy judgments, confidence, and global judgments, while trial x trial confidence was strongly associated with trial x trial accuracy judgments (r = 0.58). Our findings suggest that confidence in participants with BD is correlated with task performance, whereas in SCZ confidence was entirely associated with self-generated performance judgments. SCZ participants manifested challenges with utilization of feedback. Global judgments of performance were predicted by task performance and confidence for BD participants, with performance and confidence judgments occurring prior to generation of the global performance judgments.

Cerebral and behavioral signs of impaired cognitive flexibility and stability in schizophrenia spectrum disorders

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Patients are impaired regarding both, cognitive flexibility and stability.

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Deficient prediction error discrimination is related to reduced striatal activation.

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Decreased ACC and hippocampus activation predicts impaired rule switch detection.

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Decreased frontal and insular activation predicts impaired distractor shielding.

Background

Manifold cognitive deficits have been reported in schizophrenia spectrum disorders, including disturbances in flexible updating to altered circumstances as well as stabilization deficits in the face of distractors. In this functional magnetic resonance imaging study, we examined the neural correlates of these deficits as two complementary components of predictive processing.

Methods

In 22 patients with schizophrenia spectrum disorders and 22 healthy matched control participants, we applied a serial predictive switch-drift task to assess flexibility as successful detection of prediction-rule switches, and stability as successfully ignoring distractors (“drifts”).

Results

Patients compared with controls less reliably detected rule switches and also less efficiently inhibited drifts. A reduced striatal response to switches or drifts correlated with weaker switch-drift-discrimination in patients, suggesting impaired gating of prediction errors. The increase in activity in anterior cingulate cortex and hippocampus for detected vs. undetected switches was reduced in patients compared to controls, which may reflect impaired behavioral adaptation following prediction errors. The comparison between shielding against distractions and undetected switches showed increased activity in the inferior frontal cortex and posterior insula in controls but not in patients.

Conclusion

Our results suggest new insights into the specific disruption of predictive flexibility and stability in schizophrenia spectrum disorders, which is characterized by impaired striatal gating and inadequate cortical encoding of predictive errors.

Normative scores of the Wisconsin Card Sorting Test in a sample of the adult Portuguese population

OBJECTIVES

The Wisconsin Card Sorting Test (WCST) is a neuropsychological instrument that is widely used for assessment of executive functioning in both clinical and research settings. The aim of this study was to provide the normative scores for the WCST in a sample of Portuguese healthy adults.

METHODS

The data was collected from archival data in a total sample of 359 individuals, 149 men (41.5%, Mage = 38.3; SD = 20.3) and 210 women (58.5%, Mage = 52.2; SD = 19.4). Descriptive statistics were calculated to describe mean scores, standard-deviation and percentiles of the WCST indexes by gender, age and education. ANOVAs were used to explore the differences between these scores in sociodemographic variables. The normative scores were adjusted for age and educational level.

RESULTS

Significant statistical differences in mean scores were found in several WCST indexes, such as, total errors, perseverations, perseverative errors and conceptual level responses regarding age and education. Percentiles for WCST indexes were stratified by age group and educational level.

CONCLUSIONS

Age and education are important factors explaining performance on the WCST. This is the first study focused on the development of WCST normative scores for the adult Portuguese population, which can be applied in clinical, educational and research contexts.

Aerobic exercise improves memory and prevents cognitive deficits of relevance to schizophrenia in an animal model

INTRODUCTION AND OBJECTIVES

Cognitive impairment associated with schizophrenia (CIAS) greatly reduces patients' functionality, and remains an unmet clinical need. The sub-chronic phencyclidine (scPCP) rat model is commonly employed in studying CIAS. We have previously shown that voluntary exercise reverses impairments in novel object recognition (NOR) induced by scPCP. However, there has not been a longitudinal study investigating the potential protective effects of exercise in a model of CIAS. This study aimed to investigate the pro-cognitive and protective effects of exercise on CIAS using the translational NOR and attentional set-shifting tasks (ASST).

METHODS

Female Lister Hooded rats were either exercised (wheel running for one hour per day, five days per week, for six weeks; n=20) or not (n=20) and then tested in a natural-forgetting NOR test. Rats in each group were then administered either PCP (2 mg/kg intraperitoneally (i.p.)) or saline solution (1 mL/kg i.p.) for seven days, followed by seven days washout. Three NOR tests were conducted immediately and two and nine weeks after washout, and a natural-forgetting NOR test was carried out again eight weeks post washout. Rats were trained and tested in ASST from week 6 to week 10 post washout.

RESULTS

Non-exercised rats displayed a deficit in both of the natural-forgetting NOR tests, whereas exercised rats did not. The scPCP exercise group did not show the expected deficit in NOR at any time point, and had a significantly ameliorated deficit in the ASST compared to the scPCP control group.

CONCLUSION

Voluntary exercise has long-lasting pro-cognitive and protective effects in two cognitive domains. Exercise improves cognition and could provide protection against CIAS.

Measuring Cognitive Flexibility with the Flexible Item Selection Task: From fMRI Adaptation to Individual Connectome Mapping

Cognitive flexibility, the ability to appropriately adjust behavior in a changing environment, has been challenging to operationalize and validate in cognitive neuroscience studies. Here, we investigate neural activation and directed functional connectivity underlying cognitive flexibility using an fMRI-adapted version of the Flexible Item Selection Task (FIST) in adults (n = 32, ages 19-46 years). The fMRI-adapted FIST was reliable, showed comparable performance to the computer-based version of the task, and produced robust activation in frontoparietal, anterior cingulate, insular, and subcortical regions. During flexibility trials, participants directly engaged the left inferior frontal junction, which influenced activity in other cortical and subcortical regions. The strength of intrinsic functional connectivity between select brain regions was related to individual differences in performance on the FIST, but there was also significant individual variability in functional network topography supporting cognitive flexibility. Taken together, these results suggest that the FIST is a valid measure of cognitive flexibility, which relies on computations within a broad corticosubcortical network driven by inferior frontal junction engagement.

Striato-nigro-striatal tract dispersion abnormalities in patients with chronic schizophrenia

The white matter connections between the midbrain dopamine neurons and the striatum are part of a neural system involved in reward-based learning, a process that is impaired in patients with schizophrenia. The striato-nigro-striatal (SNS) tract, which participates in this process, has not as yet been explored. The present study aimed to use diffusion MRI (dMRI) to delineate the SNS tract, and to compare the application of two dMRI measures, Tract Dispersion (TD), an index of white matter morphology, and Fractional Anisotropy (FA), an index of white matter integrity, to detect group differences between patients with chronic schizophrenia (CSZ) and healthy controls (HC). dMRI scans were acquired in 22 male patients with CSZ and 23 age-matched HC. Two-tensor tractography was used in addition to manually-delineated regions of interest to extract the SNS tract. A mixed-model analysis of variance was used to investigate differences in TD and FA between CSZ patients and HC. The associations between TD and behavioral measures were also explored. Patients and controls differed significantly in TD (P = 0.04), but not in FA (P = 0.69). The group differences in TD were driven by a higher TD in the right hemisphere in the CSZ group. Higher TD correlated significantly with poorer performance in the Iowa Gambling Task (IGT) when combining the scores of both groups. The findings suggest that dysconnectiviy of the SNS tract which is associated with schizophrenia, could arise from abnormalities in white matter morphology. These abnormalities may potentially reflect irregularities in brain development.

Spatial learning and flexibility in 129S2/SvHsd and C57BL/6J mouse strains using different variants of the Barnes maze

Behavioural flexibility is the ability to switch between tasks and strategies following a change in rules, and involves intact functioning of the medial prefrontal cortex. Impairments of behavioural flexibility have frequently been reported in patients with schizophrenia and rodents with disruption/dysfunction of the prefrontal cortex. The discovery of a mutation in the disrupted in schizophrenia 1 (DISC1) gene in the 129 mouse strain suggests that these mice may be exploited as a 'naturally occurring' model of schizophrenia. The aim of this present study was to assess cognition and behavioural flexibility of 129S2/SvHsd mice in comparison with C57BL/6J mice in the Barnes maze, using three different maze variations that consisted of either 8, 16 or 32 holes. Whereas C57BL/6J mice were able to perform both acquisition and reversal learning in all three mazes, 129S2/SvHsd mice displayed impairments dependent on the complexity of the test. Intact acquisition and reversal occurred in the 8-hole maze; intact acquisition, but impaired reversal, was evident in the 16-hole maze and impaired acquisition was evident in the most difficult 32-hole test. Furthermore, analysis of search strategies confirmed strain differences in the adoption of spatial searches across both acquisition and reversal trials. 129S2/SvHsd mice displayed fewer spatial-type trials than C57BL/6J mice and instead employed more random or serial/chaining search behaviours. The deficits observed in both cognition and behavioural flexibility support the notion of the 129 mouse strain as a potential model of schizophrenia.

Neural and neuronal discoordination in schizophrenia: From ensembles through networks to symptoms

Despite the substantial knowledge accumulated by past research, the exact mechanisms of the pathogenesis of schizophrenia and causal treatments still remain unclear. Deficits of cognition and information processing in schizophrenia are today often viewed as the primary and core symptoms of this devastating disorder. These deficits likely result from disruptions in the coordination of neuronal and neural activity. The aim of this review is to bring together convergent evidence of discoordinated brain circuits in schizophrenia at multiple levels of resolution, ranging from principal cells and interneurons, neuronal ensembles and local circuits, to large-scale brain networks. We show how these aberrations could underlie deficits in cognitive control and other higher order cognitive-behavioural functions. Converging evidence from both animal models and patients with schizophrenia is presented in an effort to gain insight into common features of deficits in the brain information processing in this disorder, marked by disruption of several neurotransmitter and signalling systems and severe behavioural outcomes.

Test-retest reliability of the Wisconsin Card Sorting Test in people with schizophrenia

PURPOSE

The aim of this study was to examine the test-retest reliability of the Wisconsin Card Sorting Test in people with schizophrenia. In this study, minimal detectable change (MDC) was calculated and systematic measurement errors were evaluated.

METHOD

Sixty-three people with schizophrenia underwent the WCST twice with a two-week interval. Test-retest reliability was evaluated using intraclass correlation coefficient. Systematic measurement error was examined using paired t-test and effect size (Cohen's d).

RESULTS

The values of intraclass correlation coefficient were >0.70, except for two indices ("nonperseverative errors" and "failure to maintain set" with intraclass correlation coefficient of 0.56 and 0.30, respectively). Seven indices showed nonsignificant differences between the two assessments (t(62)= -0.84 to 1.38, p > 0.05) and negligible effect sizes (d = 0.03-0.13). The values of MDC with 95% certainty were 32.3, 42.0, 31.2, 36.9, 40.1, 3.3, and 3.8 for the "total number correct," "perseverative responses," "perseverative errors," "nonperseverative errors," "conceptual level responses," "number of categories completed," and "failure to maintain set" indices, respectively.

CONCLUSIONS

The WCST has acceptable test-retest reliability. Two indices ("nonperseverative errors" and "failure to maintain set") revealed lower levels of consistency in scores over repeated assessments. Clinicians and researchers should be cautious when using these two indices to interpret of the re-assessment results in people with schizophrenia.IMPLICATIONS FOR REHABILITATIONThe Wisconsin Card Sorting Test showed acceptable test-retest reliability in people with schizophrenia.Six indices of the Wisconsin Card Sorting Test revealed substantial random measurement errors, which should be used cautiously to interpret executive functions over repeated assessments.

Reward-driven decision-making impairments in schizophrenia

The ability to use feedback to guide optimal decision-making is essential for goal-directed behaviour. While impairments in feedback-driven decision-making have been associated with schizophrenia and depression, this has been examined primarily in the context of binary probabilistic choice paradigms. In real-world decision-making, however, individuals must make choices when there are more than two competing options that vary in the frequency and magnitude of potential rewards and losses. Thus, the current study examined win-stay/lose-shift (WSLS) behaviour on the Iowa Gambling Task (IGT) in order to evaluate the influence of immediate rewards and losses in guiding real-world decision-making in patients with schizophrenia and major depressive disorder. Fifty-one patients with schizophrenia, 43 patients with major depressive disorder, and 51 healthy controls completed the IGT, as well as a series of clinical and cognitive measures. WSLS was assessed by quantifying trial-by-trial behaviour following rewards and losses on the IGT. Multivariate analyses of variance revealed that patients with schizophrenia demonstrated intact lose-shift behaviour, but significantly reduced win-stay rates compared to healthy controls. In contrast, no WSLS impairments emerged in the depressed group. Win-stay impairments in the schizophrenia group were significantly related to deficits in motivation and cognition. Patients with schizophrenia exhibit impaired reward-driven decision-making in the context of multiple choices with concurrent rewards and losses, and this appears to be driven by a reduced propensity for advantageous win-stay behaviour. With the importance of reward learning and decision-making in generating goal-directed behaviour, these findings suggest a potential mechanism contributing to the motivation deficits seen in schizophrenia.

Neuropsychological tests of the future: How do we get there from here?

OBJECTIVE

This article reviews current approaches to neuropsychological assessment, identifies opportunities for development of new methods using modern psychometric theory and advances in technology, and suggests a transition path that promotes application of novel methods without sacrificing validity.

METHODS

Theoretical/state-of-the-art review.

CONCLUSIONS

Clinical neuropsychological assessment today does not reflect advances in neuroscience, modern psychometrics, or technology. Major opportunities for improving practice include both psychometric and technological strategies. Modern psychometric approaches including item response theory (IRT) enable linking procedures that can place different measures on common scales; adaptive testing algorithms that can dramatically increase efficiency of assessment; examination of differential item functioning (DIF) to detect measures that behave differently in different groups; and person fit statistics to detect aberrant patterns of responding of high value for performance validity testing. Opportunities to introduce novel technologies include computerized adaptive testing, Web-based assessment, healthcare- and bio-informatics strategies, mobile platforms, wearables, and the 'internet-of-things'. To overcome inertia in current practices, new methods must satisfy requirements for back-compatibility with legacy instrumentation, enabling us to leverage the wealth of validity data already accrued for classic procedures. A path to achieve these goals involves creation of a global network to aggregate item-level data into a shared repository that will enable modern psychometric analyses to refine existing methods, and serve as a platform to evolve novel assessment strategies, which over time can revolutionize neuropsychological assessment practices world-wide.

Anticholinergic discontinuation and cognitive functions in patients with schizophrenia: a pharmacist-physician collaboration in the outpatient department

INTRODUCTION

Cognitive impairment is a core feature and shows the highest impact on functional outcome in patients with schizophrenia. There have been no previous studies investigating the role of the pharmacist in a multidisciplinary team on cognitive outcomes in patients with schizophrenia.

PURPOSE

We evaluated the impact of pharmacist intervention on cognitive outcomes in patients with schizophrenia by focusing on anticholinergic discontinuation.

PATIENTS AND METHODS

A prospective, open-label, randomized, controlled study was conducted. Patients with schizophrenia were randomly assigned to either the pharmacist intervention or usual care groups. In the pharmacist intervention group, the pharmacist identified drug-related problems (DRPs) and provided a pharmacotherapy suggestion, while there was no intervention in the usual care group. The primary outcome was mean change from baseline of executive function by using Wisconsin Card Sorting Test (WCST) perseverative errors within the pharmacist intervention group at week 12.

RESULTS

A total of 30 patients completed the study (13 in the pharmacist intervention group and 17 in the usual care group). WCST perseverative errors at the end of the study within the pharmacist intervention group improved significantly from baseline (P=0.003). DRPs at week 12 were reduced by 85.19% and 9.76% in the pharmacist intervention and usual care groups, respectively. The most common intervention was the discontinuation of anticholinergics in patients without extrapyramidal side effects.

CONCLUSION

Added-on pharmacist intervention in a multidisciplinary team could help to improve cognitive functions in patients with schizophrenia by reducing DRPs and optimizing the drug therapy regimen, especially for anticholinergic discontinuation.

Informationally administered reward enhances intrinsic motivation in schizophrenia

Even when individuals with schizophrenia have an intact ability to enjoy rewarding moments, the means to assist them to translate rewarding experiences into goal-directed behaviors is unclear. The present study sought to determine whether informationally administered rewards enhance intrinsic motivation to foster goal-directed behaviors in individuals with schizophrenia (SZ) and healthy controls (HCs). Eighty-four participants (SZ=43, HCs=41) were randomly assigned to conditions involving either a performance-contingent reward with an informationally administered reward or a task-contingent reward with no feedback. Participants were asked to play two cognitive games of equalized difficulty. Accuracy, self-reported intrinsic motivation, free-choice intrinsic motivation (i.e., game play during a free-choice observation period), and perceived competency were measured. Intrinsic motivation and perceived competency in the cognitive games were similar between the two participant groups. The informationally administered reward significantly enhanced self-reported intrinsic motivation and perceived competency in both the groups. The likelihood that individuals with schizophrenia would play the game during the free-choice observation period was four times greater in the informationally administered reward condition than that in the no-feedback condition. Our findings suggest that, in the context of cognitive remediation, individuals with schizophrenia would benefit from informationally administered rewards.

Computational approaches to schizophrenia: A perspective on negative symptoms

Schizophrenia is a heterogeneous spectrum disorder often associated with detrimental negative symptoms. In recent years, computational approaches to psychiatry have attracted growing attention. Negative symptoms have shown some overlap with general cognitive impairments and were also linked to impaired motivational processing in brain circuits implementing reward prediction. In this review, we outline how computational approaches may help to provide a better understanding of negative symptoms in terms of the potentially underlying behavioural and biological mechanisms. First, we describe the idea that negative symptoms could arise from a failure to represent reward expectations to enable flexible behavioural adaptation. It has been proposed that these impairments arise from a failure to use prediction errors to update expectations. Important previous studies focused on processing of so-called model-free prediction errors where learning is determined by past rewards only. However, learning and decision-making arise from multiple cognitive mechanisms functioning simultaneously, and dissecting them via well-designed tasks in conjunction with computational modelling is a promising avenue. Second, we move on to a proof-of-concept example on how generative models of functional imaging data from a cognitive task enable the identification of subgroups of patients mapping on different levels of negative symptoms. Combining the latter approach with behavioural studies regarding learning and decision-making may allow the identification of key behavioural and biological parameters distinctive for different dimensions of negative symptoms versus a general cognitive impairment. We conclude with an outlook on how this computational framework could, at some point, enrich future clinical studies.

[A history and overview of anhedonia in endogenous mental disorders]

Anhedonia is the inability to experience pleasure. This disorder is heterogeneous across psychiatric disorders and is difficult for measuring and submitting to scientific analysis. Over the last several decades there has been increasing interest in the role that anhedonia plays in various psychopathologies. This article reviews the recent literature on anhedonia and its psychopathological features, which are important for prognosis in affective disorders and schizophrenia. Attempts to dissect various subtypes of anhedonia observed in negative syndrome and depression are reviewed as well.

Combination of behaviorally sub-effective doses of glutamate NMDA and dopamine D1 receptor antagonists impairs executive function

Impairment of executive function is a core feature of schizophrenia. Preclinical studies indicate that injections of either N-methyl d-aspartate (NMDA) or dopamine D₁ receptor blockers impair executive function. Despite the prevailing notion based on postmortem findings in schizophrenia that cortical areas have marked suppression of glutamate and dopamine, recent in vivo imaging studies suggest that abnormalities of these neurotransmitters in living patients may be quite subtle. Thus, we hypothesized that modest impairments in both glutamate and dopamine function can act synergistically to cause executive dysfunction. In the present study, we investigated the effect of combined administration of "behaviorally sub-effective" doses of NMDA and dopamine D₁ receptor antagonists on executive function. An operant conditioning-based set-shifting task was used to assess behavioral flexibility in rats that were systemically injected with NMDA and dopamine D₁ receptor antagonists individually or in combination prior to task performance. Separate injections of the NMDA receptor antagonist, MK-801, and the dopamine D₁ receptor antagonist, SCH 23390, at low doses did not impair set-shifting; however, the combined administration of these same behaviorally sub-effective doses of the antagonists significantly impaired the performance during set-shifting without affecting learning, retrieval of the memory of the initial rule, latency of responses or the number of omissions. The combined treatment also produced an increased number of perseverative errors. Our results indicate that NMDA and D₁ receptor blockade act synergistically to cause behavioral inflexibility, and as such, subtle abnormalities in glutamatergic and dopaminergic systems may act cooperatively to cause deficits in executive function.

Probabilistic Reversal Learning in Schizophrenia: Stability of Deficits and Potential Causal Mechanisms

Although individuals with schizophrenia show impaired feedback-driven learning on probabilistic reversal learning (PRL) tasks, the specific factors that contribute to these deficits remain unknown. Recent work has suggested several potential causes including neurocognitive impairments, clinical symptoms, and specific types of feedback-related errors. To examine this issue, we administered a PRL task to 126 stable schizophrenia outpatients and 72 matched controls, and patients were retested 4 weeks later. The task involved an initial probabilistic discrimination learning phase and subsequent reversal phases in which subjects had to adjust their responses to sudden shifts in the reinforcement contingencies. Patients showed poorer performance than controls for both the initial discrimination and reversal learning phases of the task, and performance overall showed good test-retest reliability among patients. A subgroup analysis of patients (n = 64) and controls (n = 49) with good initial discrimination learning revealed no between-group differences in reversal learning, indicating that the patients who were able to achieve all of the initial probabilistic discriminations were not impaired in reversal learning. Regarding potential contributors to impaired discrimination learning, several factors were associated with poor PRL, including higher levels of neurocognitive impairment, poor learning from both positive and negative feedback, and higher levels of indiscriminate response shifting. The results suggest that poor PRL performance in schizophrenia can be the product of multiple mechanisms.

The neural underpinnings of cognitive flexibility and their disruption in psychotic illness

Schizophrenia (SZ) has long been associated with a variety of cognitive deficits, including reduced cognitive flexibility. More recent findings, however, point to tremendous inter-individual variability among patients on measures of cognitive flexibility/set-shifting. With an eye toward shedding light on potential sources of variability in set-shifting abilities among SZ patients, I examine the neural substrates of underlying probabilistic reversal learning (PRL) - a paradigmatic measure of cognitive flexibility - as well as neuromodulatory influences upon these systems. Finally, I report on behavioral and neuroimaging studies of PRL in SZ patients, discussing the potentially influences of illness profile and antipsychotic medications on cognitive flexibility in SZ.

Neurocognitive functioning as an intermediary variable between psychopathology and insight in schizophrenia

Based on the neuropsychological deficit model of insight in schizophrenia, we constructed exploratory prediction models for insight, designating neurocognitive measures as the intermediary variables between psychopathology and insight into patients with schizophrenia. The models included the positive, negative, and autistic preoccupation symptoms as primary predictors, and activation symptoms as an intermediary variable for insight. Fifty-six Korean patients, in the acute stage of schizophrenia, completed the Positive and Negative Syndrome Scale, as well as a comprehensive neurocognitive battery of tests at the baseline, 8-weeks, and 1-year follow-ups. Among the neurocognitive measures, the Korean Wechsler Adult Intelligence Scale (K-WAIS) picture arrangement, Controlled Oral Word Association Test (COWAT) perseverative response, and the Continuous Performance Test (CPT) standard error of reaction time showed significant correlations with the symptoms and the insight. When these measures were fitted into the model as intermediaries between the symptoms and the insight, only the perseverative response was found to have a partial mediating effect - both cross-sectionally, and in the 8-week longitudinal change. Overall, the relationship between insight and neurocognitive functioning measures was found to be selective and weak.

Neural correlates of rules and conflict in medial prefrontal cortex during decision and feedback epochs

The ability to properly adjust behavioral responses to cues in a changing environment is crucial for survival. Activity in the medial Prefrontal Cortex (mPFC) is thought to both represent rules to guide behavior as well as detect and resolve conflicts between rules in changing contingencies. However, while lesion and pharmacological studies have supported a crucial role for mPFC in this type of set-shifting, an understanding of how mPFC represents current rules or detects and resolves conflict between different rules is unclear. Here, we directly address the role of rat mPFC in shifting rule based behavioral strategies using a novel behavioral task designed to tease apart neural signatures of rules, conflict and direction. We demonstrate that activity of single neurons in rat mPFC represent distinct rules. Further, we show increased firing on high conflict trials in a separate population of mPFC neurons. Reduced firing in both populations of neurons was associated with poor performance. Moreover, activity in both populations increased and decreased firing during the outcome epoch when reward was and was not delivered on correct and incorrect trials, respectively. In addition, outcome firing was modulated by the current rule and the degree of conflict associated with the previous decision. These results promote a greater understanding of the role that mPFC plays in switching between rules, signaling both rule and conflict to promote improved behavioral performance.

Working memory contributions to reinforcement learning impairments in schizophrenia

Previous research has shown that patients with schizophrenia are impaired in reinforcement learning tasks. However, behavioral learning curves in such tasks originate from the interaction of multiple neural processes, including the basal ganglia- and dopamine-dependent reinforcement learning (RL) system, but also prefrontal cortex-dependent cognitive strategies involving working memory (WM). Thus, it is unclear which specific system induces impairments in schizophrenia. We recently developed a task and computational model allowing us to separately assess the roles of RL (slow, cumulative learning) mechanisms versus WM (fast but capacity-limited) mechanisms in healthy adult human subjects. Here, we used this task to assess patients' specific sources of impairments in learning. In 15 separate blocks, subjects learned to pick one of three actions for stimuli. The number of stimuli to learn in each block varied from two to six, allowing us to separate influences of capacity-limited WM from the incremental RL system. As expected, both patients (n = 49) and healthy controls (n = 36) showed effects of set size and delay between stimulus repetitions, confirming the presence of working memory effects. Patients performed significantly worse than controls overall, but computational model fits and behavioral analyses indicate that these deficits could be entirely accounted for by changes in WM parameters (capacity and reliability), whereas RL processes were spared. These results suggest that the working memory system contributes strongly to learning impairments in schizophrenia.

Jumping to conclusions in schizophrenia

Schizophrenia is a mental disorder associated with a variety of symptoms, including hallucinations, delusions, social withdrawal, and cognitive dysfunction. Impairments on decision-making tasks are routinely reported: evidence points to a particular deficit in learning from and revising behavior following feedback. In addition, patients tend to make hasty decisions when probabilistic judgments are required. This is known as "jumping to conclusions" (JTC) and has typically been demonstrated by presenting participants with colored beads drawn from one of two "urns" until they claim to be sure which urn the beads are being drawn from (the proportions of colors vary in each urn). Patients tend to make early decisions on this task, and there is evidence to suggest that a hasty decision-making style might be linked to delusion formation and thus be of clinical relevance. Various accounts have been proposed regarding what underlies this behavior. In this review, we briefly introduce the disorder and the decision-making deficits associated with it. We then explore the evidence for each account of JTC in the context of a wider decision-making deficit and then go on to summarize work exploring JTC in healthy controls using pharmacological manipulations and functional imaging. Finally, we assess whether JTC might have a role in therapy.

Motivational Deficits and Negative Symptoms in Schizophrenia: Concepts and Assessments

Recent years have seen a resurgence of interest in motivational disturbances in schizophrenia . This is largely driven by the recognition that these disturbances are central to the "experiential" subdomain of negative symptoms and are particularly important determinants of functional disability. Research into the causes and treatment of experiential negative symptoms is therefore a high priority. This chapter reviews findings from experimental psychopathology and affective science relevant to understanding the neurobehavioral processes that underlie these negative symptoms. We focus on abnormalities in four processes that have received the most attention as likely contributors: anticipatory pleasure, reward learning, effort-based decision-making, and social motivation. We also review the research literature on pharmacological and psychosocial approaches to reduce functional deficits attributable to negative symptoms. Translational research is beginning to inform the development of new treatments specifically designed to target the experiential subdomain of negative symptoms.

Identifying cognitive remediation change through computational modelling--effects on reinforcement learning in schizophrenia

OBJECTIVE

Converging research suggests that individuals with schizophrenia show a marked impairment in reinforcement learning, particularly in tasks requiring flexibility and adaptation. The problem has been associated with dopamine reward systems. This study explores, for the first time, the characteristics of this impairment and how it is affected by a behavioral intervention-cognitive remediation.

METHOD

Using computational modelling, 3 reinforcement learning parameters based on the Wisconsin Card Sorting Test (WCST) trial-by-trial performance were estimated: R (reward sensitivity), P (punishment sensitivity), and D (choice consistency). In Study 1 the parameters were compared between a group of individuals with schizophrenia (n = 100) and a healthy control group (n = 50). In Study 2 the effect of cognitive remediation therapy (CRT) on these parameters was assessed in 2 groups of individuals with schizophrenia, one receiving CRT (n = 37) and the other receiving treatment as usual (TAU, n = 34).

RESULTS

In Study 1 individuals with schizophrenia showed impairment in the R and P parameters compared with healthy controls. Study 2 demonstrated that sensitivity to negative feedback (P) and reward (R) improved in the CRT group after therapy compared with the TAU group. R and P parameter change correlated with WCST outputs. Improvements in R and P after CRT were associated with working memory gains and reduction of negative symptoms, respectively.

CONCLUSION

Schizophrenia reinforcement learning difficulties negatively influence performance in shift learning tasks. CRT can improve sensitivity to reward and punishment. Identifying parameters that show change may be useful in experimental medicine studies to identify cognitive domains susceptible to improvement.

Extreme Elemental Processing in a High Schizotypy Population: Relation to Cognitive Deficits

The cognitive deficits observed in schizophrenia have been characterized as a failure to utilize task-setting information to guide behaviour, especially in situations in which there is response conflict. Recently, we have provided support for this account; high schizotypy individuals demonstrated inferior biconditional discrimination performance compared to low scorers, but were not impaired on a simple discrimination that did not require the use of task-setting cues. These results may, however, also be explained by the way in which individuals with high schizotypy process stimulus compounds . Here, we examine the initial approaches to solving biconditional and control discrimination tasks of participants with high and low schizotypy scores. In particular, we focus on performance during the first block of training trials to capture processing style before the acquisition of the discrimination tasks. Participants scoring highly on the introvertive anhedonia subscale (which has been allied to the negative and cognitive symptoms of schizophrenia) demonstrated better biconditional performance during the first block of training trials than did low-schizotypy individuals, consistent with a highly elemental approach to stimulus processing. Subsequent recognition tests confirmed this analysis demonstrating that the pattern of performance observed in participants with high schizotypy was associated with a failure to discriminate conjunctions of items that had been seen before from those that had not. These results suggest that the negative/cognitive symptoms of schizophrenia may reflect an extreme bias towards elemental, as opposed to configural, processing of stimulus conjunctions.

Reinforcement learning and dopamine in schizophrenia: dimensions of symptoms or specific features of a disease group?

Abnormalities in reinforcement learning are a key finding in schizophrenia and have been proposed to be linked to elevated levels of dopamine neurotransmission. Behavioral deficits in reinforcement learning and their neural correlates may contribute to the formation of clinical characteristics of schizophrenia. The ability to form predictions about future outcomes is fundamental for environmental interactions and depends on neuronal teaching signals, like reward prediction errors. While aberrant prediction errors, that encode non-salient events as surprising, have been proposed to contribute to the formation of positive symptoms, a failure to build neural representations of decision values may result in negative symptoms. Here, we review behavioral and neuroimaging research in schizophrenia and focus on studies that implemented reinforcement learning models. In addition, we discuss studies that combined reinforcement learning with measures of dopamine. Thereby, we suggest how reinforcement learning abnormalities in schizophrenia may contribute to the formation of psychotic symptoms and may interact with cognitive deficits. These ideas point toward an interplay of more rigid versus flexible control over reinforcement learning. Pronounced deficits in the flexible or model-based domain may allow for a detailed characterization of well-established cognitive deficits in schizophrenia patients based on computational models of learning. Finally, we propose a framework based on the potentially crucial contribution of dopamine to dysfunctional reinforcement learning on the level of neural networks. Future research may strongly benefit from computational modeling but also requires further methodological improvement for clinical group studies. These research tools may help to improve our understanding of disease-specific mechanisms and may help to identify clinically relevant subgroups of the heterogeneous entity schizophrenia.

Using negative feedback to guide behavior: impairments on the first 4 cards of the Wisconsin Card Sorting Test predict negative symptoms of schizophrenia

Research has demonstrated that individuals with schizophrenia fail to appropriately use negative feedback to guide learning. These learning deficits are thought to arise from abnormalities in midbrain dopamine activity. Primary and enduring negative symptoms are also associated with abnormal dopamine activity and are expected to produce more severe deficits in learning when they present in individuals with schizophrenia. The current study examines this matter by comparing individuals with deficit syndrome schizophrenia, which is characterized by primary and enduring negative symptoms, to individuals with nondeficit syndrome schizophrenia and to normal controls in their use of positive feedback and negative feedback to guide learning on the first four cards of the WCST. Participants included 67 individuals with schizophrenia (15 deficit; 52 nondeficit syndrome) and 51 healthy controls. Accuracy data from the first 4 cards of the WCST and measures of global test performance were examined. Individuals with schizophrenia were significantly less accurate than controls in their performance on early (pre-shift) WCST trials, and this impairment was significantly greater in patients with deficit than nondeficit schizophrenia. Additionally, accuracy across the first 4 WCST cards significantly predicted the number of categories completed and percentage of perseverative errors across the entire test. These findings suggest that negative symptoms of schizophrenia are associated with difficulty using negative feedback to adaptively guide behavior, and are consistent with the notion that abnormal DA signaling contributes to the higher-order executive functioning impairments seen in schizophrenia with severe negative symptoms.

Neural structures underlying set-shifting: roles of medial prefrontal cortex and anterior cingulate cortex

Impaired attentional set-shifting and inflexible decision-making are problems frequently observed during normal aging and in several psychiatric disorders. To understand the neuropathophysiology of underlying inflexible behavior, animal models of attentional set-shifting have been developed to mimic tasks such as the Wisconsin Card Sorting Task (WCST), which tap into a number of cognitive functions including stimulus-response encoding, working memory, attention, error detection, and conflict resolution. Here, we review many of these tasks in several different species and speculate on how prefrontal cortex and anterior cingulate cortex might contribute to normal performance during set-shifting.

Negative symptoms and executive function in schizophrenia: does their relationship change with illness duration?

BACKGROUND

Negative symptoms and cognitive dysfunction are of crucial functional and prognostic importance in schizophrenia. However, the nature of the relationship between them and the factors that may influence it have not been well established.

AIMS

To investigate whether the relationship between negative symptoms and executive function changes according to the duration of illness in schizophrenia.

METHODS

The Positive and Negative Syndrome Scale was used to assess psychopathology and the Wisconsin Card Sorting Test (WCST) to evaluate executive function in a sample of 200 schizophrenic patients who were classified in 3 groups according to their duration of illness: up to 5 years (short duration group), 6-20 years (intermediate duration group) and over 20 years of illness (long duration group).

RESULTS

Medium-sized correlations were found between negative symptoms and WCST performance as assessed by the number of completed categories in all 3 groups. However, differences were found according to the duration of schizophrenia. For patients in the short duration group, negative symptoms correlated with WCST nonperseverative errors, but for those in the long duration group the correlation was with perseverative errors.

CONCLUSION

We found a differential relationship between negative and cognitive symptoms in different stages of schizophrenia. Illness duration should be considered when studying the relationship between negative symptoms and cognition.

Versatility of the mouse reversal/set-shifting test: effects of topiramate and sex

The ability to learn a rule to guide behavior is crucial for cognition and executive function. However, in a constantly changing environment, flexibility in terms of learning and changing rules is paramount. Research suggests there may be common underlying causes for the similar rule learning impairments observed in many psychiatric disorders. One of these common anatomical manifestations involves deficits to the GABAergic system, particularly in the frontal cerebral cortical regions. Many common anti-epileptic drugs and mood stabilizers activate the GABA system with the reported adverse side effects of cognitive dysfunction. The mouse reversal/set-shifting test was used to evaluate effects in mice given topiramate, which is reported to impair attention in humans. Here we report that in mice topiramate prevents formation of the attentional set, but does not alter reversal learning. Differences in the GABA system are also found in many neuropsychiatric disorders that are more common in males, including schizophrenia and autism. Initial findings with the reversal/set-shifting task excluded female subjects. In this study, female mice tested on the standard reversal/set-shifting task showed similar reversal learning, but were not able to form the attentional set. The behavioral paradigm was modified and when presented with sufficient discrimination tasks, female mice performed the same as male mice, requiring the same number of trials to reach criterion and form the attentional set. The notable difference was that female mice had an extended latency to complete the trials for all discriminations. In summary, the reversal/set-shifting test can be used to screen for cognitive effects of potential therapeutic compounds in both male and female mice.

Anterior cingulate cortex activation is related to learning potential on the WCST in schizophrenia patients

The remediation of executive function in patients with schizophrenia is important in rehabilitation because these skills affect the patient's capacity to function in the community. There is evidence that instructional techniques can improve deficits in the Wisconsin Card Sorting Test (WCST) in some schizophrenia patients. We used a standard test/training phase/standard test format of the WCST to classify 36 schizophrenia patients as high-achievers, learners or non-retainers. All healthy controls performed as high-achievers. An event-related fMRI design assessed neural activation patterns during post-training WCST performance. Patients showed a linear trend between set-shifting related activation in the anterior cingulate cortex and learning potential, i.e. increased activation in high-achievers, a trend for increased activation in learners, and no activation in non-retainers compared to controls. In addition, activation in the temporoparietal cortex was highest in patients classified as learners, whereas in non-retainers activation was increased in the inferior frontal gyrus compared to controls and high-achieving patients. These results emphasize the relevance of the ACC's neural integrity in learning set-shifting strategies for patients with schizophrenia. Also, our results support the hypothesis that compensatory neural activation in patients with schizophrenia helps them to catch up with healthy controls on cognitive tasks.

Dissociation of response and feedback negativity in schizophrenia: electrophysiological and computational evidence for a deficit in the representation of value

Contrasting theories of schizophrenia propose that the disorder is characterized by a deficit in phasic changes in dopamine activity in response to ongoing events or, alternatively, by a weakness in the representation of the value of responses. Schizophrenia patients have reliably reduced brain activity following incorrect responses but other research suggests that they may have intact feedback-related potentials, indicating that the impairment may be specifically response-related. We used event-related brain potentials and computational modeling to examine this issue by comparing the neural response to outcomes with the neural response to behaviors that predict outcomes in patients with schizophrenia and psychiatrically healthy comparison subjects. We recorded feedback-related activity in a passive gambling task and a time estimation task and error-related activity in a flanker task. Patients' brain activity following an erroneous response was reduced compared to comparison subjects but feedback-related activity did not differ between groups. To test hypotheses about the possible causes of this pattern of results, we used computational modeling of the electrophysiological data to simulate the effects of an overall reduction in patients' sensitivity to feedback, selective insensitivity to positive or negative feedback, reduced learning rate, and a decreased representation of the value of the response given the stimulus on each trial. The results of the computational modeling suggest that schizophrenia patients exhibit weakened representation of response values, possibly due to failure of the basal ganglia to strongly associate stimuli with appropriate response alternatives.

Abnormal negative feedback processing in first episode schizophrenia: evidence from an oculomotor rule switching task

BACKGROUND

Previous studies have shown that patients with schizophrenia are impaired on executive tasks, where positive and negative feedbacks are used to update task rules or switch attention. However, research to date using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an oculomotor 'rule switching' task to investigate the use of negative feedback when switching between task rules in people with schizophrenia.

METHOD

A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping had reversed.

RESULTS

Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ.

CONCLUSIONS

The results not only confirm the existence of a basic deficit in stimulus-response rule switching in schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia.