Sarah E. Morris

Reward Processing in Schizophrenia: A Deficit in the Representation of Value

Patients with schizophrenia demonstrate deficits in motivation and learning that suggest impairment in different aspects of the reward system. In this article, we present the results of 8 converging experiments that address subjective reward experience, the impact of rewards on decision making, and the role of rewards in guiding both rapid and long-term learning. All experiments compared the performance of stably treated outpatients with schizophrenia and demographically matched healthy volunteers. Results to date suggest (1) that patients have surprisingly normal experiences of positive emotion when presented with evocative stimuli, (2) that patients show reduced correlation, compared with controls, between their own subjective valuation of stimuli and action selection, (3) that decision making in patients appears to be compromised by deficits in the ability to fully represent the value of different choices and response options, and (4) that rapid learning on the basis of trial-to-trial feedback is severely impaired whereas more gradual learning may be surprisingly preserved in many paradigms. The overall pattern of findings suggests compromises in the orbital and dorsal prefrontal structures that play a critical role in the ability to represent the value of outcomes and plans. In contrast, patients often (but not always) approach normal performance levels on the slow learning achieved by the integration of reinforcement signals over many trials, thought to be mediated by the basal ganglia.

A Randomized, Controlled Trial of Computer-Assisted Cognitive Remediation for Schizophrenia

OBJECTIVE There is considerable interest in cognitive remediation for schizophrenia, but its essential components are still unclear. The goal of the current study was to develop a broadly targeted computer-assisted cognitive remediation program and conduct a rigorous clinical trial in a large group of schizophrenia patients. METHOD Sixty-nine people with schizophrenia or schizoaffective disorder were randomly assigned to 36 sessions of computer-assisted cognitive remediation or an active control condition. Remediation broadly targeted cognitive and everyday performance by providing supportive, graduated training and practice in selecting, executing, and monitoring cognitive operations. It used engaging computer-based cognitive exercises and one-on-one training. A total of 61 individuals (34 in remediation group, 27 in control group) engaged in treatment, completed posttreatment assessments, and were included in intent-to-treat analyses. Primary outcomes were remediation exercise metrics, neuropsychological composites (episodic memory, working memory, attention, executive functioning, and processing speed), and proxy measures of community functioning. RESULTS Regression modeling indicated that performance on eight of 10 exercise metrics improved significantly more in the remediation condition than in the control condition. The mean effect size, favoring the remediation condition, was 0.53 across all 10 metrics. However, there were no significant benefits of cognitive remediation on any neuropsychological or functional outcome measure, either immediately after treatment or at the 3-month follow-up. CONCLUSIONS Cognitive remediation for people with schizophrenia was effective in improving performance on computer exercises, but the benefits of training did not generalize to broader neuropsychological or functional outcome measures. The evidence for this treatment approach remains mixed.

Learning-related changes in brain activity following errors and performance feedback in schizophrenia

In previous studies of self-monitoring in schizophrenia, patients have exhibited reductions in the amplitude of the error-related negativity (ERN), a component of the event-related brain potential (ERP) elicited most prominently immediately following the execution of incorrect responses. In the current study, we examined the ERN and a related component, the feedback negativity (FBN) in 26 schizophrenia outpatients and 27 psychiatrically healthy comparison subjects during a probabilistic learning task in which participants could learn stimulus-response pairs by attending to feedback indicating response accuracy. The validity of the feedback varied in three conditions. In one condition, accuracy feedback was entirely consistent (i.e., a left response to one of the stimuli in this condition was always correct and a right response was always incorrect). In the second condition, feedback was valid on only 80% of the trials, and in the third condition, accuracy feedback was random. Changes in ERP amplitudes accompanying learning of stimulus-response pairs were examined. Schizophrenia patients exhibited reduced ERN amplitude compared to healthy subjects in all conditions. This finding extends the previously reported impairment to include disruption of self-monitoring on a task in which participants learn stimulus-response mappings by trial and error, rather than being told the mappings explicitly. Schizophrenia patients also exhibited reduced FBN amplitude compared to healthy subjects in the 100% condition during early trials when the feedback was essential for accurate performance. These findings suggest that reward-related brain activity is weakened in schizophrenia, perhaps reflecting diminished sensitivity to whether ongoing events are better or worse than expected.

Studying Hallucinations Within the NIMH RDoC Framework

We explore how hallucinations might be studied within the National Institute of Mental Health (NIMH) Research Domain Criteria (RDoC) framework, which asks investigators to step back from diagnoses based on symptoms and focus on basic dimensions of functioning. We start with a description of the objectives of the RDoC project and its domains and constructs. Because the RDoC initiative asks investigators to study phenomena across the wellness spectrum and different diagnoses, we address whether hallucinations experienced in nonclinical populations are the same as those experienced by people with psychotic diagnoses, and whether hallucinations studied in one clinical group can inform our understanding of the same phenomenon in another. We then discuss the phenomenology of hallucinations and how different RDoC domains might be relevant to their study. We end with a discussion of various challenges and potential next steps to advance the application of the RDoC approach to this area of research.

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.

Rethinking mental disorders: the role of learning and brain plasticity.

Recent research in neurodevelopment, neuroplasticity and genetics is providing new insights into the etiogenesis of psychopathology, but progress in treatment development has been hampered by reliance on diagnostic categories that are characterized by heterogeneity and based primarily on phenomenology. The NIMH Research Domain Criteria (RDoC) initiative seeks to provide a neuroscience-based nosological framework for future research on psychopathology, categorizing individuals for research purposes using a dimensional approach that capitalizes on advances in modern neuroscience. These scientific advances and new approaches to classification can inform the development of novel, circuit-based interventions and the personalization of treatment. In this paper, we review key advances areas in clinical neuroscience, describe the RDoC project and highlight some emerging treatment approaches that are consistent with these developments.

Response activation impairments in schizophrenia: evidence from the lateralized readiness potential.

Previous research has demonstrated deficits in preresponse motor activity in schizophrenia, as evidenced by a reduced lateralized readiness potential (LRP). The LRP deficit could be due to increased activation of the incorrect response (e.g., failure to suppress competition) or to reduced activation of the correct response (e.g., a low-level impairment in response preparation). To distinguish these possibilities, we asked whether the LRP impairment is increased under conditions of strong response competition. We manipulated the compatibility of stimulus-response mappings (Experiment 1) and the compatibility of the target with flankers (Experiment 2). In both experiments, the patient LRP was reduced as much under conditions of low response competition as under high competition. These results are incompatible with a failure of patients to suppress competition and are instead consistent with a deficit in activating the correct response.

Psychophysiological science and the research domain criteria: A commentary ☆

The current special issue, devoted to the Research Domain Criteria (RDoC) initiative of the US National Institute of Mental Health, showcases a variety of empirical and review articles that address issues related to this dimensional and multi-method approach to research on mental disorders. Here, we provide an integrative perspective on various aspects of these articles, focused around the primary principles of the RDoC approach and the practical and methodological issues related to conducting RDoC-informed research. The chief point we wish to highlight is that these articles demonstrate the ways in which the field of psychophysiology already thinks along the lines of RDoC in terms of using biobehavioral constructs, looking for convergence among constructs using various methodologies, and utilizing dimensional measurements in studies. In this sense, RDoC is not novel; however, by specifying a formal research platform it provides explicit encouragement and guidance for using such principles in understanding psychiatric phenomena, rather than continuing to focus research efforts on traditional diagnostic categories alone.

Effects of cognitive remediation on negative symptoms dimensions: Exploring the role of working memory

Background Recent theories suggest that poor working memory (WM) may be the cognitive underpinning of negative symptoms in people with schizophrenia. In this study, we first explore the effect of cognitive remediation (CR) on two clusters of negative symptoms (i.e. expressive and social amotivation), and then assess the relevance of WM gains as a possible mediator of symptom improvement. Method Data were accessed for 309 people with schizophrenia from the NIMH Database of Cognitive Training and Remediation Studies and a separate study. Approximately half the participants received CR and the rest were allocated to a control condition. All participants were assessed before and after therapy and at follow-up. Expressive negative symptoms and social amotivation symptoms scores were calculated from the Positive and Negative Syndrome Scale. WM was assessed with digit span and letter-number span tests. Results Participants who received CR had a significant improvement in WM scores (d = 0.27) compared with those in the control condition. Improvements in social amotivation levels approached statistical significance (d = −0.19), but change in expressive negative symptoms did not differ between groups. WM change did not mediate the effect of CR on social amotivation. Conclusions The results suggest that a course of CR may benefit behavioural negative symptoms. Despite hypotheses linking memory problems with negative symptoms, the current findings do not support the role of this cognitive domain as a significant mediator. The results indicate that WM improves independently from negative symptoms reduction.