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Behavioral modeling of human choices reveals dissociable effects of physical effort and temporal delay on reward devaluation.

ABSTRACT: There has been considerable interest from the fields of biology, economics, psychology, and ecology about how decision costs decrease the value of rewarding outcomes. For example, formal descriptions of how reward value changes with increasing temporal delays allow for quantifying individual decision preferences, as in animal species populating different habitats, or normal and clinical human populations. Strikingly, it remains largely unclear how humans evaluate rewards when these are tied to energetic costs, despite the surge of interest in the neural basis of effort-guided decision-making and the prevalence of disorders showing a diminished willingness to exert effort (e.g., depression). One common assumption is that effort discounts reward in a similar way to delay. Here we challenge this assumption by formally comparing competing hypotheses about effort and delay discounting. We used a design specifically optimized to compare discounting behavior for both effort and delay over a wide range of decision costs (Experiment 1). We then additionally characterized the profile of effort discounting free of model assumptions (Experiment 2). Contrary to previous reports, in both experiments effort costs devalued reward in a manner opposite to delay, with small devaluations for lower efforts, and progressively larger devaluations for higher effort-levels (concave shape). Bayesian model comparison confirmed that delay-choices were best predicted by a hyperbolic model, with the largest reward devaluations occurring at shorter delays. In contrast, an altogether different relationship was observed for effort-choices, which were best described by a model of inverse sigmoidal shape that is initially concave. Our results provide a novel characterization of human effort discounting behavior and its first dissociation from delay discounting. This enables accurate modelling of cost-benefit decisions, a prerequisite for the investigation of the neural underpinnings of effort-guided choice and for understanding the deficits in clinical disorders characterized by behavioral inactivity.

SUBMITTER: Klein-Flugge MC

PROVIDER: S-EPMC4376637 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Behavioral modeling of human choices reveals dissociable effects of physical effort and temporal delay on reward devaluation.

Klein-Flügge Miriam C MC Kennerley Steven W SW Saraiva Ana C AC Penny Will D WD Bestmann Sven S

PLoS computational biology 20150327 3

There has been considerable interest from the fields of biology, economics, psychology, and ecology about how decision costs decrease the value of rewarding outcomes. For example, formal descriptions of how reward value changes with increasing temporal delays allow for quantifying individual decision preferences, as in animal species populating different habitats, or normal and clinical human populations. Strikingly, it remains largely unclear how humans evaluate rewards when these are tied to e ...[more]

PMID: 25816114

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Project description:RATIONALE:Substance-related behaviour is often viewed as an appetitive behaviour, motivated by the reinforcing effects of the drug. However, there are various indices of substance motivation (e.g. attentional bias, behavioural economic demand, craving) and it is unclear how these are related or whether they play an important role in all types of substance-related behaviour. OBJECTIVES:(1) To determine the effect of alcohol devaluation on several indices of alcohol motivation and goal-directed and cue-elicited alcohol behaviour. (2) To investigate which components of motivation mediate any effect of devaluation on behaviour. METHODS:Sixty-two social drinkers gave baseline measures of alcohol craving, behavioural economic demand and choice for alcohol vs. soft drink. Participants tasted alcohol which was either unadulterated (control) or adulterated with a bitter solution (devaluation) before craving and demand were measured again. Alcohol choice was assessed in several phases: extinction (evaluating goal-directed behaviour), in the presence of drink cues (Pavlovian-to-instrumental transfer (PIT, cue-elicited behaviour)), and reacquisition. Attentional bias (AB) was measured by tracking eye movements towards the drink cues during novel PIT trials where both cues were presented. Finally, consumption was evaluated in a taste test. RESULTS:Alcohol devaluation reduced alcohol-related demand, AB, alcohol choice in all phases, and consumption. Alcohol cues presented during PIT increased alcohol choice above baseline irrespective of devaluation. AB and demand for alcohol fully mediated the effect of devaluation on alcohol choice during extinction, AB fully mediated the effect on cue-elicited (specific PIT) alcohol choice and alcohol consumption. CONCLUSIONS:Alcohol behaviour in social drinkers is largely sensitive to devaluation, i.e. governed by current motivational value of the drug (suggesting goal-directed behaviour). However, a dissociable form of stimulus control can also drive alcohol-seeking independently of drug value (specific PIT). Mediation analyses suggests that AB may play a paradoxical role in both forms of alcohol seeking and consumption.

Project description:Antidepressants remediate negative biases in emotional processing early in treatment, prior to mood improvement. However, the effects on reward processing potentially relevant to the treatment of anhedonia are less clear. Here we investigate the early and sustained effects of the dopamine and noradrenaline reuptake inhibitor bupropion on behavioural measures of emotional and reward processing in currently depressed individuals. Forty-six currently depressed patients and 42 healthy controls participated in a repeated measures study, during which open-label bupropion was administered to only the patient group over a six week period without a placebo group. All participants completed the Emotional Test Battery and a probabilistic instrumental learning task at week 0, week 2 and week 6. Currently depressed patients displayed negative biases in emotional processing and blunted response bias for high-probability wins compared to the healthy controls at baseline. Bupropion was found to reduce the negative biases in emotional processing early in treatment, including a significant decrease in the percentage misclassification of other face emotions as sad and the number of negative self-referent words falsely recalled between baseline and week 2. Conversely, bupropion was found to initially further reduce the response bias for high-probability wins between baseline and week 2. This effect reversed with six weeks' bupropion treatment and reward processing was normalized compared to the healthy controls. Early in treatment, bupropion acts to reduce negative biases in emotional processing but exacerbates impaired reward processing. The beneficial actions of bupropion on reward processing then occur later in treatment. Such dissociation in the temporal effects of bupropion on emotional and reward processing has implications for the treatment of the different symptom domains of negative affect and anhedonia in depression.This article is part of a discussion meeting issue 'Of mice and mental health: facilitating dialogue between basic and clinical neuroscientists'.

Project description:BACKGROUND:McDowell CHOICES (Coordinated Health Opportunities Involving Communities, Environments, and Schools) Project is a county wide endeavor aimed at increasing opportunities for physical activity (PA) in McDowell County, West Virginia (WV). A comprehensive needs-assessment laid the foundation of the project. METHODS:During the 6 month needs assessment, multiple sources of data were collected in two Town Hall Meetings (n = 80); a student online PA interest survey (n = 465); a PA and nutrition survey among 5(th) (10-11 years) and 8(th) graders (13-14 years) with questions adapted from the CDC's Youth Risk Behavior Surveillance Survey (n = 442, response rate = 82.2%); six semi-structured school and community focus groups (n = 44); school site visits (n = 11); and BMI screening (n = 550, response rate = 69.7%). RESULTS:One third of children in McDowell County meet the national PA minimum of 60 minutes daily. At least 40% of 5(th) and 8(th) graders engage in electronic screen activity for 3 hours or more every day. The prevalence of obesity in 5(th) graders is higher in McDowell County than the rest of WV (~55% vs. 47% respectively). SWOT analyses of focus group data suggest an overall interest in PA but also highlight a need for increase in structured PA opportunities. Focus group data also suggested that a central communication (e.g. internet-based) platform would be beneficial to advertise and boost participation both in current and future programs. Schools were commonly mentioned as potential facilities for public PA participation throughout the county, both with regards to access and convenience. School site visits suggest that schools need more equipment and resources for before, during, and after school programs. CONCLUSIONS:An overwhelming majority of participants in the McDowell CHOICES needs assessment were interested to participate in more PA programs throughout the county as well as to improve opportunities for the provision of such programs. Public schools were widely recognized as the hub of the communities and provide the best venue for PA promotion for both students and adult citizens, and can potentially serve as a platform for change in rural communities such as McDowell County.

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Behavioral modeling of human choices reveals dissociable effects of physical effort and temporal delay on reward devaluation.

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Behavioral modeling of human choices reveals dissociable effects of physical effort and temporal delay on reward devaluation.

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