Behavioral and Electrophysiological Alterations for Reinforcement Learning in Manic and Euthymic Patients with Bipolar Disorder

Reinforcement learning and working memory in mood disorders: A computational analysis in a developmental transdiagnostic sample

BACKGROUND

Mood disorders commonly onset during adolescence and young adulthood and are conceptually and empirically related to reinforcement learning abnormalities. However, the nature of abnormalities associated with acute symptom severity versus lifetime diagnosis remains unclear, and prior research has often failed to disentangle working memory from reward processes.

METHODS

The present sample (N = 220) included adolescents and young adults with a lifetime history of unipolar disorders (n = 127), bipolar disorders (n = 28), or no history of psychopathology (n = 62), and varying severity of mood symptoms. Analyses fitted a reinforcement learning and working memory model to an instrumental learning task that varied working memory load, and tested associations between model parameters and diagnoses or current symptoms.

RESULTS

Current severity of manic or anhedonic symptoms negatively correlated with task performance. Participants reporting higher severity of current anhedonia, or with lifetime unipolar or bipolar disorders, showed lower reward learning rates. Participants reporting higher severity of current manic symptoms showed faster working memory decay and reduced use of working memory.

LIMITATIONS

Computational parameters should be interpreted in the task environment (a deterministic reward learning paradigm), and developmental population. Future work should test replication in other paradigms and populations.

CONCLUSIONS

Results indicate abnormalities in reinforcement learning processes that either scale with current symptom severity, or correspond with lifetime mood diagnoses. Findings may have implications for understanding reward processing anomalies related to state-like (current symptom) or trait-like (lifetime diagnosis) aspects of mood disorders.

Reward and punishment learning deficits among bipolar disorder subtypes

BACKGROUND

Reward sensitivity is an essential dimension related to mood fluctuations in bipolar disorder (BD), but there is currently a debate around hypersensitivity or hyposensitivity hypotheses to reward in BD during remission, probably related to a heterogeneous population within the BD spectrum and a lack of reward bias evaluation. Here, we examine reward maximization vs. punishment avoidance learning within the BD spectrum during remission.

METHODS

Patients with BD-I (n = 45), BD-II (n = 34) and matched (n = 30) healthy controls (HC) were included. They performed an instrumental learning task designed to dissociate reward-based from punishment-based reinforcement learning. Computational modeling was used to identify the mechanisms underlying reinforcement learning performances.

RESULTS

Behavioral results showed a significant reward learning deficit across BD subtypes compared to HC, captured at the computational level by a lower sensitivity to rewards compared to punishments in both BD subtypes. Computational modeling also revealed a higher choice randomness in BD-II compared to BD-I that reflected a tendency of BD-I to perform better during punishment avoidance learning than BD-II.

LIMITATIONS

Our patients were not naive to antipsychotic treatment and were not euthymic (but in syndromic remission) according to the International Society for Bipolar Disorder definition.

CONCLUSIONS

Our results are consistent with the reward hyposensitivity theory in BD. Computational modeling suggests distinct underlying mechanisms that produce similar observable behaviors, making it a useful tool for distinguishing how symptoms interact in BD versus other disorders. In the long run, a better understanding of these processes could contribute to better prevention and management of BD.

Cognitive Processes and Legal Capacity in Patients With Bipolar Disorder: A Brief Research Report

The current study verified the association between cognitive process such as attention, executive functioning, and legal capacity in patients with bipolar disorder (BD). The sample consisted of 72 participants, assorted to episodic patients (n = 21), euthymic patients (n = 22), and healthy controls (HCs) (n = 29). We used the following neuropsychological measures: subtests of the Wechsler Abbreviated Intelligence Scale (WASI): vocabulary and matrix reasoning; Continuous Performance Test (CPT); Five Digit Test (FDT); and Rey–Osterrieth Complex Figure (ROCF). Euthymic patients expressed slower processing speed (FDT) compared to HC. They tended to make more errors with slightly worse discrimination, suggesting more impulsiveness (CPT, p < 0.01). On the contrary, episodic patients showed worse discrimination, committed more omissions, were more inconsistent with regard to response speed (CPT-3, p < 0.01), showed more difficulties in organizing their actions (ROCF: copy, p = 0.03), and were more rigid (FDT: flexibility, p = 0.03). The results suggest that bipolar patients in episode express more cognitive impairments that can compromise the quality of legal capacity. These results highlight the need for more protective support for episodic BD patients regarding legal capacity.

Electrophysiological biomarkers of behavioral dimensions from cross-species paradigms

There has been a fundamental failure to translate preclinically supported research into clinically efficacious treatments for psychiatric disorders. One of the greatest impediments toward improving this species gap has been the difficulty of identifying translatable neurophysiological signals that are related to specific behavioral constructs. Here, we present evidence from three paradigms that were completed by humans and mice using analogous procedures, with each task eliciting candidate a priori defined electrophysiological signals underlying effortful motivation, reinforcement learning, and cognitive control. The effortful motivation was assessed using a progressive ratio breakpoint task, yielding a similar decrease in alpha-band activity over time in both species. Reinforcement learning was assessed via feedback in a probabilistic learning task with delta power significantly modulated by reward surprise in both species. Additionally, cognitive control was assessed in the five-choice continuous performance task, yielding response-locked theta power seen across species, and modulated by difficulty in humans. Together, these successes, and also the teachings from these failures, provide a roadmap towards the use of electrophysiology as a method for translating findings from the preclinical assays to the clinical settings.

Reward mechanism of depressive episodes in bipolar disorder: Enhanced theta power in feedback-related negativity

INTRODUCTION

This study aimed to explore the reward-related neural mechanism in patients with depressive mood in bipolar disorder (BD) using event-related potentials. It remains unknown whether or not different neurobiological markers underlying depression symptoms in BD depression and major depression disorder (MDD).

METHODS

24 patients with BD depression and 20 healthy controls were included. Participants underwent evaluation with the Temporal Experience of Pleasure Scale (TEPS), followed by the classical gambling paradigm, while undergoing 64-channel electroencephalography. The waveform of feedback-related negativity (FRN) was extracted from the 250-350 ms time-window after participants received feedback regarding loss or gain. Event-related potential datasets were obtained using time-frequency analysis.

RESULTS

(1) The TEPS scores of the patients were significantly lower than those of the controls [t₍₄₂₎ = 5.16, p < 0.01]. (2) The event of loss elicited a deeper FRN in patients than that in controls [t₍₄₂₎ = 2.19, p < 0.05], while no difference was observed in the event of gains (t₍₄₂₎ = 1.12, p > 0.05). (3) Theta power rooted in FRN in patients was significantly higher in loss than in gain [F_(1,42) = 30.32, p < 0.01]. (4) Analysis of Variance (ANOVA) illustrated the interaction effect of theta power in gain/loss between two groups [F_(1,42) = 3.59, p = 0.06].

LIMITATION

Our study did not analyze the effect of different drugs which might affect our results.

CONCLUSION

The enhanced reflection of negative feedback was consistent with the negative bias, impulse control impairment, and emotional dysregulation observed in the bipolar disorder spectrum. We suggested that the extreme theta power generated from the anterior cingulate gyrus (ACC) might be the main component of abnormal FRN.

Altered behavioral and electrophysiological responses to social fairness in manic and euthymic patients with bipolar disorder

BACKGROUND

Individuals with bipolar disorder show mood instability, including heightened anger and impulsivity. The Ultimatum Game (UG) is a tool used to evaluate emotional and social decision-making strategies. We investigated behavioral and electrophysiological responses to subjectively fair or unfair offers in the UG in patients with bipolar I disorder.

METHODS

Twenty-four manic patients, 20 euthymic patients, and 30 healthy controls participated in this study. We analyzed their behaviors and collected electroencephalography data with which to analyze feedback-related negativity (FRN) as they played in the UG as responders.

RESULTS

Manic patients exhibited significantly higher rejection rates for unfair offers than euthymic patients and healthy controls. Healthy individuals exhibited a greater (i.e., more negative) FRN amplitude in response to unfair offers than to fair offers, whereas euthymic patients exhibited a greater FRN amplitude in response to fair offers compared with unfair offers. Manic patients exhibited no difference in FRN amplitudes between fair and unfair offers.

CONCLUSIONS

The current data suggest that different behavioral responses and FRN amplitude patterns can be associated with characteristic manifestations of mood instability in manic bipolar patients. In addition, electrophysiological alterations in response to unfair offers may be a trait abnormality independent of mood state.

Affective cognition in bipolar disorder: A systematic review by the ISBD targeting cognition task force

BACKGROUND

Impairments in affective cognition are part of the neurocognitive profile and possible treatment targets in bipolar disorder (BD), but the findings are heterogeneous. The International Society of Bipolar Disorder (ISBD) Targeting Cognition Task Force conducted a systematic review to (i) identify the most consistent findings in affective cognition in BD, and (ii) provide suggestions for affective cognitive domains for future study and meta-analyses.

METHODS

The review included original studies reporting behavioral measures of affective cognition in BD patients vs controls following the procedures of the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) statement. Searches were conducted on PubMed/MEDLINE, EMBASE, and PsychInfo from inception until November 2018.

RESULTS

A total of 106 articles were included (of which nine included data for several affective domains); 41 studies assessed emotional face processing; 23 studies investigated reactivity to emotional words and images; 3 investigated explicit emotion regulation; 17 assessed implicit emotion regulation; 31 assessed reward processing and affective decision making. In general, findings were inconsistent. The most consistent findings were trait-related difficulties in facial emotion recognition and implicit emotion regulation, and impairments in reward processing and affective decision making during mood episodes. Studies using eye-tracking and facial emotion analysis revealed subtle trait-related abnormalities in emotional reactivity.

CONCLUSION

The ISBD Task Force recommends facial expression recognition, implicit emotion regulation, and reward processing as domains for future research and meta-analyses. An important step to aid comparability between studies in the field would be to reach consensus on an affective cognition test battery for BD.