Modeling Effort-Based Decision Making: Individual Differences in Schizophrenia and Major Depressive Disorder

BACKGROUND

A critical facet of motivation is effort-based decision making, which refers to the mental processes involved in deciding whether a potential reward is worth the effort. To advance understanding of how individuals with schizophrenia and major depressive disorder utilize cost-benefit information to guide choice behavior, this study aimed to characterize individual differences in the computations associated with effort-based decision making.

METHODS

One hundred forty-five participants (51 with schizophrenia, 43 with depression, and 51 healthy control participants) completed the Effort Expenditure for Rewards Task, with mixed effects modeling conducted to estimate the predictors of decision making. These model-derived, subject-specific coefficients were then clustered using k-means to test for the presence of discrete transdiagnostic subgroups with different profiles of reward, probability, and cost information utilization during effort-based decision making.

RESULTS

An optimal 2-cluster solution was identified, with no significant differences in the distribution of diagnostic groups between clusters. Cluster 1 (n = 76) was characterized by overall lower information utilization during decision making than cluster 2 (n = 61). Participants in this low information utilization cluster were also significantly older and more cognitively impaired, and their utilization of reward, probability, and cost was significantly correlated with clinical amotivation, depressive symptoms, and cognitive functioning.

CONCLUSIONS

Our findings revealed meaningful individual differences among participants with schizophrenia, depression, and healthy control participants in their utilization of cost-benefit information in the context of effortful decision making. These findings may provide insight into different processes associated with aberrant choice behavior and may potentially guide the identification of more individualized treatment targets for effort-based motivation deficits across disorders.

Behavioural phenotypes of intrinsic motivation in schizophrenia determined by cluster analysis of objectively quantified real-world performance

Intrinsic motivation deficits are a prominent feature of schizophrenia that substantially impacts functional outcome. This study used cluster analysis of innate real-world behaviours captured during two open-field tasks to dimensionally examine heterogeneity in intrinsic motivation in schizophrenia patients (SZ) and healthy controls (HC). Wireless motion capture quantified participants' behaviours aligning with distinct aspects of intrinsic motivation: exploratory behaviour and effortful activity in the absence of external incentive. Cluster analysis of task-derived measures identified behaviourally differentiable subgroups, which were compared across standard clinical measures of general amotivation, cognition, and community functioning. Among 45 SZ and 47 HC participants, three clusters with characteristically different behavioural phenotypes emerged: low exploration (20 SZ, 19 HC), low activity (15 SZ, 8 HC), and high exploration/activity (10 SZ, 20 HC). Low performance in either dimension corresponded with similar increased amotivation. Within-cluster discrepancies emerged for amotivation (SZ > HC) within the low exploration and high performance clusters, and for functioning (SZ < HC) within all clusters, increasing from high performance to low activity to low exploration. Objective multidimensional characterization thus revealed divergent behavioural expression of intrinsic motivation deficits that may be conflated by summary clinical measures of motivation and overlooked by unidimensional evaluation. Deficits in either aspect may hinder general motivation and functioning particularly in SZ. Multidimensional phenotyping may help guide personalized remediation by discriminating between intrinsic motivation impairments that require amelioration versus unimpaired tendencies that may facilitate remediation.

Goal-directed planning and action impairments in schizophrenia evaluated in a virtual environment

Planning and executing goal-directed behaviours are critical final steps in translating motivation into action. Amotivation is a key feature of schizophrenia, but its impact on goal-directed functioning has not been extensively studied in an objective and ecologically valid manner. To address this, we investigated goal-directed planning and action in schizophrenia using a virtual reality task, the Multitasking in the City Test (MCT). The MCT was administered to 49 outpatients with schizophrenia and 55 healthy controls, and required participants to complete a series of errands in a virtual city. Ability to complete the task as directed was assessed by a performance score based on errands completed and errors committed. Task efficiency was evaluated by the total distance travelled, and an index of path efficiency comparing an optimal route with the traversed route. Schizophrenia participants had lower performance scores, travelled farther, and had reduced path efficiency compared to healthy controls. Greater distance travelled and lower path efficiency in schizophrenia were related to amotivation. Path efficiency in schizophrenia was also related to neurocognition, including planning ability; notably, this relationship appeared to be independent of the relationship with amotivation. Individuals with schizophrenia demonstrated impaired goal-directed planning and action in the context of a simulated everyday errands task, both in terms of reduced capacity to complete errands and reduced efficiency in doing so. The latter may manifest as diminished real-world motivated and functional behaviour in patients with schizophrenia and indicates a specific deficit in the execution of planned behaviour.

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.

Objective investigation of activity preference in schizophrenia: A pilot study

Amotivation and reduced goal-directed activity engagement are prominent features of schizophrenia. Previous investigations of patients' activities have relied on accounts of daily living activities, rather than objective measures. This study used wireless motion capture to objectively evaluate activity preference when individuals are provided an explicit choice between an active versus passive engagement option. Twenty outpatients with schizophrenia and twenty matched healthy controls completed the Activity Preference Task, in which participants play a motion-based game (active) or watch a film (passive), and were administered clinical and cognitive assessments. Schizophrenia participants' duration, intensity, and persistence of active engagement were associated with apathy and community functioning. No group differences emerged from comparisons of task measures; however, exploratory cluster analysis identified a distinct subgroup of schizophrenia patients with reduced engagement and increased apathy compared to other patients and controls. The Task provides a means of quantifying activity engagement, which may be particularly valuable given the lack of objective measures for intrinsically motivated behaviours. Our initial findings suggest that schizophrenia patients as a group are equally inclined as healthy individuals towards actively engaging activities when presented an explicit choice, but such provision may be insufficient for initiation and maintenance of functional behaviours among amotivated patients.

An Examination of the Multi-Faceted Motivation System in Healthy Young Adults

Background: Amotivation is a prevalent symptom in schizophrenia (SZ) and depression (MDD), and is linked to poor functional outcomes in affected individuals. Conceptualizations of motivation have outlined a multi-faceted construct comprised of reward responsiveness, reward expectancy, reward valuation, effort valuation, and action selection/preference-based decision making. To date, findings from studies utilizing variable-centered approaches to examining isolated facets of motivation in SZ and MDD have been inconsistent. Thus, the present study adopted a person-centered approach, and comprehensively examined the reward system in a non-clinical sample in an attempt to explore potential subtypes of motivation impairments, while minimizing the effects of illness-related confounds. Methods: Ninety-six healthy undergraduate students were evaluated for amotivation, schizotypal traits, depressive symptoms, and cognition, and administered objective computerized tasks to measure the different facets of motivation. Cluster analysis was performed to explore subgroups of individuals based on similar motivation task performance. Additionally, correlational analyses were conducted in order to examine inter-relationships between motivation facets, and relations between clinical measures and facets of motivation. Results: Cluster analysis identified two subgroups of individuals with differential motivation performance profiles. Correlational analyses revealed that reward responsiveness was associated with amotivation, depressive symptoms, and negative schizotypy. Further, significant inter-correlations were found between reward responsiveness and reward expectancy, as well as between reward valuation and effort valuation. Conclusions: Our results mark important steps forward in understanding motivation in a non-clinical sample, and guide future dimensional and comprehensive analyses of the multi-faceted reward system. It remains to be seen whether these patterns of results will be similar in clinical populations such as SZ and MDD.