Building a clinically relevant cognitive task: case study of the AX paradigm

Persistence, diagnostic specificity and genetic liability for context-processing deficits in schizophrenia

Context-processing deficits have been shown in schizophrenia during first-episode, medication-naïve status, that persist after short-term antipsychotic treatment and also in first-degree relatives of individuals with schizophrenia. To confirm longer term persistence of deficits, we examined schizophrenia patients (n=63) during first-episode, medication-naïve status through to one-year follow-up, compared to healthy control (n=83) and non-schizophrenia psychosis comparison (n=47) groups, as well as unaffected first-degree relatives of individuals with schizophrenia (n=31). Context-processing ability was assessed by performance on the AX-CPT (Continuous Performance Test) at baseline, 8 weeks, 6 months, and 1 year (relatives only at baseline). Reaction time, error rates and signal detection indices (d'-context) of context processing were analyzed. Linear discriminant analyses (LDA) on early timepoints (baseline, 8 weeks) were conducted to predict confirmatory diagnosis (schizophrenia vs. psychosis control) at 6 months. Schizophrenia patients showed evidence of impaired context-processing relative to both the healthy and psychosis comparator groups at baseline and continued through to 1 year. While context-processing impairments persisted in schizophrenia patients through one year, the impairments in psychosis controls, which were more modest at baseline, remitted at follow-up. First-degree relatives showed deficits that were intermediate between the schizophrenia and healthy control groups. LDA showed 67% classification rates for distinguishing schizophrenia from non-schizophrenia psychosis. The persistence, diagnostic specificity and association with genetic liability give support for context processing impairments serving as a cognitive endophenotype for schizophrenia and evaluation of context processing could contribute to diagnostic assessments.

An intact social cognitive process in schizophrenia: situational context effects on perception of facial affect

BACKGROUND

Impaired facial affect recognition is the most consistent social cognitive finding in schizophrenia. Although social situations provide powerful constraints on our perception, little is known about how situational context modulates facial affect recognition in schizophrenia.

METHODS

Study 1 was a single-site study with 34 schizophrenia patients and 22 healthy controls. Study 2 was a 2-site study with 68 schizophrenia patients and 28 controls. Both studies administered a Situational Context Facial Affect Recognition Task with 2 conditions: a situational context condition and a no-context condition. For the situational context condition, a briefly shown face was preceded by a sentence describing either a fear- or surprise-inducing event. In the no-context condition, a face was presented without a sentence. For both conditions, subjects rated how fearful or surprised the face appeared on a 9-point Likert scale.

RESULTS

For the situational context condition of study 1, both patients and controls rated faces as more afraid when they were paired with fear-inducing sentences and as more surprised when they were paired with surprise-inducing sentences. The degree of modulation was comparable across groups. For the no-context condition, patients rated faces comparably to controls. The findings of study 2 replicated those from study 1.

CONCLUSIONS

Despite previous abnormalities in other types of context paradigms, this study found intact situational context processing in schizophrenia, suggesting that patients benefit from situational context when interpreting ambiguous facial expression. This area of relative social cognitive strength in schizophrenia has implications for social cognitive training programs.

Context-processing abilities in chronic cocaine users

Cocaine dependence is a particularly severe problem in the United States, resulting in broad economic and personal costs. Significant evidence of generalized cognitive deficits associated with cocaine dependence has been reported. Two studies evaluated whether context processing, the processes involved in representing and maintaining information regarding the context of one's environment, might be seen as a process-specific deficit that may explain some aspects of the broader cognitive deficits associated with cocaine dependence. Study 1 used the expectancy variant of the AX task to assess this ability; Study 2 employed the Dot Pattern Expectancy task. Significant between-groups differences were found in each study for d'-context, a comparison of AX hits and BX misses; these results indicated significant between-groups differences in context-processing ability. In Study 1, significant between-groups a priori contrasts of AY versus BX trials indicated the likelihood of a specific deficit in context processing in the cocaine group; however, this contrast was not significant in Study 2. Overall, the results of these studies support the theory of impaired context-processing ability associated with cocaine misuse. However, these results do not allow for the interpretation of a process-specific deficit in context-processing ability. Future research targeted at investigating aspects of this context-processing impairment associated with cocaine misuse can shed light on the specificity of this deficit.

Rostral-caudal gradients of abstraction revealed by multi-variate pattern analysis of working memory

The lateral frontal cortex (LFC) is thought to represent contextual and rule-based information that allows adaptive behavior according to circumstance. Recent progress has suggested that the representations of the LFC vary along its rostral-caudal axis with more abstract, higher level representations associated with rostral areas of the LFC and more concrete, lower level representations associated with caudal areas of the LFC. Here, we investigated this proposal. Subjects responded to stimuli based upon a nested series of contextual cues stored in working memory (WM) while being scanned with fMRI. Higher level context cues denoted an abstract rule set while lower level context cues provided more concrete information. Using multi-variate pattern analysis (MVPA), we found varying forms of representation along the rostral-caudal axis of the LFC depending on the type of information stored in WM. Rostral areas of frontal cortex in the lateral orbitofrontal cortex (OFC) represented the higher level context, but not more concrete information, and only when more concrete information was unavailable. Mid-level areas in the mid-dorsolateral prefrontal cortex (DLPFC) and inferior frontal junction (IFJ) represented more concrete rules, but only when the forthcoming response could not be anticipated. By contrast, the dorsal premotor cortex (PMd) and primary motor cortex (M1) represented contextual and response information when the forthcoming response could be anticipated on the basis of context. Collectively, these data indicate that representations dedicated to higher levels of abstraction become less discriminating when more concrete information becomes available. These patterns are consistent with rostral-caudal abstraction proposals of the LFC.

Dissociable frontal-striatal and frontal-parietal networks involved in updating hierarchical contexts in working memory

Recent theories propose that the prefrontal cortex (PFC) is organized in a hierarchical fashion with more abstract, higher level information represented in anterior regions and more concrete, lower level information represented in posterior regions. This hierarchical organization affords flexible adjustments of action plans based on the context. Computational models suggest that such hierarchical organization in the PFC is achieved through interactions with the basal ganglia (BG) wherein the BG gate relevant contexts into the PFC. Here, we tested this proposal using functional magnetic resonance imaging (fMRI). Participants were scanned while updating working memory (WM) with 2 levels of hierarchical contexts. Consistent with PFC abstraction proposals, higher level context updates involved anterior portions of the PFC (BA 46), whereas lower level context updates involved posterior portions of the PFC (BA 6). Computational models were only partially supported as the BG were sensitive to higher, but not lower level context updates. The posterior parietal cortex (PPC) showed the opposite pattern. Analyses examining changes in functional connectivity confirmed dissociable roles of the anterior PFC-BG during higher level context updates and posterior PFC-PPC during lower level context updates. These results suggest that hierarchical contexts are organized by distinct frontal-striatal and frontal-parietal networks.

CNTRICS imaging biomarker selections: Executive control paradigms

In this article, we describe results of the 5th Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia meeting which identified candidate imaging biomarkers for used in measuring neural activity associated with specific component processes of cognition that are targeted for treatment development in schizophrenia and other disorders. This manuscript describes the process by which measures related to executive control were selected, along with the specific measures recommended for further development. Two paradigms were recommended for measurement of the cognitive and neural mechanisms underlying 2 core component processes of executive control, rule generation and selection, and dynamic adjustments of Control. The 2 paradigms are the AX continuous performance task task (letter and dot forms), implemented as an functional magnetic resonance imaging (fMRI) paradigm to engage neural systems supporting rule generation and selection, and the switching Stroop task, implemented as either fMRI or electroencephalography that may be used as a measure of both rule generation and selection as well as dynamic adjustment in control. A detailed description of each paradigm, together with a review of the relevant literature related to their cognitive and neural validity and measurement properties is provided. These 2 paradigms are recommended for further development, including further validation at the cognitive and neural level and optimization with respect to subject tolerability, psychometric, and neurometric features.

Clinical, functional, and intertask correlations of measures developed by the Cognitive Neuroscience Test Reliability and Clinical Applications for Schizophrenia Consortium

The goal of the Cognitive Neuroscience Test Reliability and Clinical Applications for Schizophrenia (CNTRACS) Consortium was to develop measures of discrete cognitive processes, allowing for the interpretation of specific deficits that could be linked to specific neural systems. Here we report on the intertask, clinical, and functional correlates of the 4 tasks that were investigated in large groups of patients with schizophrenia (>100) and healthy controls (>73) at 5 sites across the United States. In both healthy and patient groups, the key dependent measures from the CNTRACS tasks were minimally intercorrelated, suggesting that they are measuring discrete abilities. Correlations were examined between CNTRACS tasks and measures of functional capacity, premorbid IQ, symptom severity, and level of community functioning. Performance on tasks measuring relational memory encoding, goal maintenance, and visual gain control were correlated with premorbid IQ and the former 2 tasks with the functional capacity. Goal maintenance task performance was negatively correlated with negative symptom severity and informant reports of community function. These correlations reflect the relationship of specific abilities with functional outcome. They are somewhat lower than functional outcome correlations observed with conventional neuropsychological tests that confound multiple cognitive and motivational deficits. The measures of visual integration and gain control were not significantly correlated with clinical symptoms or function. These results suggest that the CNTRACS tasks measure discrete cognitive abilities, some of which relate to aspects of functional capacity/outcome in schizophrenia.

Optimization of a goal maintenance task for use in clinical applications

BACKGROUND

We sought to develop a Dot Pattern Expectancy task (DPX) to assess goal maintenance for use in clinical trials. Altering the standard task created 5 versions of the DPX to compare-a standard version and 4 others. Alterations in the interstimulus interval (ISI) length and the strength of a learned prepotent response distinguished the different tasks. These adjustments were designed to decrease administration time and/or improve reliability of the data.

METHODS

We determined participant eligibility in an initial session (the first of 3) using clinical interviewing tools. The initial session also included a demographic assessment and assessments of community functioning and symptom severity. All versions of the DPX were administered, across 3 sessions. Specific deficits on the context processing compared with difficulty control condition were evaluated using mixed-effects logistic regression within a hierarchical linear model.

RESULTS

We analyzed the data from 136 control participants and 138 participants with schizophrenia. Relative to a difficulty control condition, patients performed worse than controls on context processing conditions that required goal maintenance. ISI did not predict errors. Stronger prepotency was associated with increased errors in the difficulty control relative to context processing condition for controls, which improved the interpretability of findings for patients. Reliability was acceptable for a version of the task with a 10-minute running time.

CONCLUSIONS

The best compromise between task duration and interpretability occurred on a version with a short ISI and a strong prepotency.

Early sensory contributions to contextual encoding deficits in schizophrenia

CONTEXT

The AX version of the visual continuous performance task (AX-CPT) is widely used for investigating visual working memory dysfunction in schizophrenia. Event-related potentials (ERP) provide an objective index of brain function and can be used to evaluate brain substrates underlying impaired cognition in schizophrenia.

OBJECTIVE

To assess the mechanisms that underlie visual working memory dysfunction in schizophrenia relative to impairment of early visual processing.

DESIGN

Case-control study.

SETTING

Inpatient and outpatient facilities associated with the Nathan Kline Institute for Psychiatric Research.

PARTICIPANTS

A total of 30 individuals with schizophrenia and 17 healthy comparison subjects.

INTERVENTIONS

Three versions of the AX-CPT, with parametric variations in the proportions of trial types, were used to test performance and underlying neural activity during differential challenge situations. Contrast sensitivity measures were obtained from most subjects.

MAIN OUTCOME MEASURES

Behavioral performance was assessed using d' context scores. Integrity of stimulus- and task-related cortical activation to both cue and probe stimuli was assessed using sensory (C1, P1, N1) and cognitive (N2, contingent negative variation [CNV]) ERP components. Early magnocellular/parvocellular function was assessed using contrast sensitivity. Linear regression and path analyses were used to assess relations between physiological and behavioral parameters.

RESULTS

Patients showed reduced amplitude of both early sensory (P1, N1) and later cognitive (N2, CNV) ERP components. Deficits in sensory (N1) and cognitive (N2) component activation to cue stimuli contributed independently to impaired behavioral performance. In addition, sensory deficits predicted impaired cognitive ERP generation. Finally, deficits in performance correlated with impairments in contrast sensitivity to low, but not high, spatial frequency stimuli.

CONCLUSIONS

Working memory deficits in schizophrenia have increasingly been attributed to impairments in stimulus encoding rather than to failures in memory retention. This study provides objective physiological support for encoding hypotheses. Further, deficits in sensory processing contribute significantly to impaired working memory performance, consistent with generalized neurochemical models of schizophrenia.

The paradox of cognitive flexibility in autism

We present an overview of current literature addressing cognitive flexibility in autism spectrum disorders. Based on recent studies at multiple sites, using diverse methods and participants of different autism subtypes, ages and cognitive levels, no consistent evidence for cognitive flexibility deficits was found. Researchers and clinicians assume that inflexible everyday behaviors in autism are directly related to cognitive flexibility deficits as assessed by clinical and experimental measures. However, there is a large gap between the day-to-day behavioral flexibility and that measured with these cognitive flexibility tasks. To advance the field, experimental measures must evolve to reflect mechanistic models of flexibility deficits. Moreover, ecologically valid measures are required to be able to resolve the paradox between cognitive and behavioral inflexibility.

CNTRICS final task selection: working memory

The third meeting of the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) was focused on selecting promising measures for each of the cognitive constructs selected in the first CNTRICS meeting. In the domain of working memory, the 2 constructs of interest were goal maintenance and interference control. CNTRICS received 3 task nominations for each of these constructs, and the breakout group for working memory evaluated the degree to which each of these tasks met prespecified criteria. For goal maintenance, the breakout group for working memory recommended the AX-Continuous Performance Task/Dot Pattern Expectancy task for translation for use in clinical trial contexts in schizophrenia research. For interference control, the breakout group recommended the recent probes and operation/symmetry span tasks for translation for use in clinical trials. This article describes the ways in which each of these tasks met the criteria used by the breakout group to recommend tasks for further development.

Selecting paradigms from cognitive neuroscience for translation into use in clinical trials: proceedings of the third CNTRICS meeting

This overview describes the goals and objectives of the third conference conducted as part of the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) initiative. This third conference was focused on selecting specific paradigms from cognitive neuroscience that measured the constructs identified in the first CNTRICS meeting, with the goal of facilitating the translation of these paradigms into use in clinical trials contexts. To identify such paradigms, we had an open nomination process in which the field was asked to nominate potentially relevant paradigms and to provide information on several domains relevant to selecting the most promising tasks for each construct (eg, construct validity, neural bases, psychometrics, availability of animal models). Our goal was to identify 1-2 promising tasks for each of the 11 constructs identified at the first CNTRICS meeting. In this overview article, we describe the on-line survey used to generate nominations for promising tasks, the criteria that were used to select the tasks, the rationale behind the criteria, and the ways in which breakout groups worked together to identify the most promising tasks from among those nominated. This article serves as an introduction to the set of 6 articles included in this special issue that provide information about the specific tasks discussed and selected for the constructs from each of 6 broad domains (working memory, executive control, attention, long-term memory, perception, and social cognition).