Neural correlates of effort-based valuation with prospective choices

The impact of subclinical psychotic symptoms on delay and effort discounting: Insights from behavioral, computational, and electrophysiological methods

BACKGROUND

The ability to value rewards is crucial for adaptive behavior and is influenced by the time and effort required to obtain them. Impairments in these computations have been observed in patients with schizophrenia and may be present in individuals with subclinical psychotic symptoms (PS).

METHODS

In this study, we employed delay and effort-discounting tasks with food rewards in thirty-nine participants divided into high and low levels of PS. We investigated the underlying mechanisms of effort-discounting through computational modelling of dopamine prefrontal and subcortical circuits and the electrophysiological biomarker of both delay and effort-discounting alterations through resting-state frontal alpha asymmetry (FAA).

RESULTS

Results revealed greater delay discounting in the High PS group compared to the Low PS group but no differences in the effort discounting task. However, in this task, the same levels of estimated dopamine release were associated with a lower willingness to exert effort for high-calorie food rewards in High PS participants compared to Low PS participants. Although there were no significant differences in FAA between the High PS and Low PS groups, FAA was significantly associated with the severity of participants' negative symptoms.

CONCLUSIONS

Our study suggests that the dysfunction in temporal and effort cost computations, seen in patients with schizophrenia, may be present in individuals with subclinical PS. These findings provide valuable insight into the early vulnerability markers (behavioral, computational, and electrophysiological) for psychosis, which may aid in the development of preventive interventions. These findings are preliminary and warrant further investigation.

The role of the human hippocampus in decision-making under uncertainty

The role of the hippocampus in decision-making is beginning to be more understood. Because of its prospective and inferential functions, we hypothesized that it might be required specifically when decisions involve the evaluation of uncertain values. A group of individuals with autoimmune limbic encephalitis-a condition known to focally affect the hippocampus-were tested on how they evaluate reward against uncertainty compared to reward against another key attribute: physical effort. Across four experiments requiring participants to make trade-offs between reward, uncertainty and effort, patients with acute limbic encephalitis demonstrated blunted sensitivity to reward and effort whenever uncertainty was considered, despite demonstrating intact uncertainty sensitivity. By contrast, the valuation of these two attributes (reward and effort) was intact on uncertainty-free tasks. Reduced sensitivity to changes in reward under uncertainty correlated with the severity of hippocampal damage. Together, these findings provide evidence for a context-sensitive role of the hippocampus in value-based decision-making, apparent specifically under conditions of uncertainty.

Human ventromedial prefrontal cortex is necessary for prosocial motivation

Ventromedial prefrontal cortex (vmPFC) is vital for decision-making. Functional neuroimaging links vmPFC to processing rewards and effort, while parallel work suggests vmPFC involvement in prosocial behaviour. However, the necessity of vmPFC for these functions is unknown. Patients with rare focal vmPFC lesions (n = 25), patients with lesions elsewhere (n = 15) and healthy controls (n = 40) chose between rest and exerting effort to earn rewards for themselves or another person. vmPFC damage decreased prosociality across behavioural and computational measures. vmPFC patients earned less, discounted rewards by effort more, and exerted less force when another person benefited, compared to both control groups. Voxel-based lesion mapping revealed dissociations between vmPFC subregions. While medial damage led to antisocial behaviour, lateral damage increased prosocial behaviour relative to patients with damage elsewhere. vmPFC patients also showed reduced effort sensitivity overall, but reward sensitivity was limited to specific subregions. These results reveal multiple causal contributions of vmPFC to prosocial behaviour, effort and reward.

Disentangling effort from probability of success: Temporal dynamics of frontal midline theta in effort-based reward processing

The ability to weigh a reward against the effort required to acquire it is critical for decision-making. However, extant experimental paradigms oftentimes confound increased effort demand with decreased reward probability, thereby obscuring neural correlates underlying these cognitive processes. To resolve this issue, we designed novel tasks that disentangled probability of success - and therefore reward probability - from effort demand. In Experiment 1, reward magnitude and effort demand were varied while reward probability was kept constant. In Experiment 2, effort demand and reward probability were varied while reward magnitude remained fixed. Electroencephalogram (EEG) data was recorded to explore how frontal midline theta (FMT; an electrophysiological index of mPFC function) and component P3 (an index of incentive salience) respond to effort demand, and reward magnitude and probability. We found no evidence that FMT tracked effort demands or net value during cue evaluation. At feedback, however, FMT power was enhanced for high compared to low effort trials, but not modulated by reward magnitude or probability. Conversely, P3 was sensitive to reward magnitude and probability at both cue and feedback phases and only integrated expended effort costs at feedback, such that P3 amplitudes continued to scale with reward magnitude and probability but were also increased for high compared to low effort reward feedback. These findings suggest that, when likelihood of success is equal, FMT power does not track net value of prospective effort-based rewards. Instead, expended cognitive effort potentiates FMT power and enhances the saliency of rewards at feedback. SIGNIFICANCE STATEMENT: The way the brain weighs rewards against the effort required to achieve them is critical for understanding motivational disorders. Current paradigms confound increased effort demand with decreased reward probability, making it difficult to disentangle neural activity associated with effort costs from those associated with reward likelihood. Here, we explored the temporal dynamics of effort-based reward (via frontal midline theta (FMT) and component P3) while participants underwent a novel paradigm that kept probability of reward constant between mental effort demand conditions. Our findings suggest that the FMT does not track net value and that expended effort enhances, instead of attenuates, the saliency of rewards.

Neurobiological foundations and clinical relevance of effort-based decision-making

Applying effort-based decision-making tasks provides insights into specific variables influencing choice behaviors. The current review summarizes the structural and functional neuroanatomy of effort-based decision-making. Across 39 examined studies, the review highlights the ventromedial prefrontal cortex in forming reward-based predictions, the ventral striatum encoding expected subjective values driven by reward size, the dorsal anterior cingulate cortex for monitoring choices to maximize rewards, and specific motor areas preparing for effort expenditure. Neuromodulation techniques, along with shifting environmental and internal states, are promising novel treatment interventions for altering neural alterations underlying decision-making. Our review further articulates the translational promise of this construct into the development, maintenance and treatment of psychiatric conditions, particularly those characterized by reward-, effort- and valuation-related deficits.

Value Estimation versus Effort Mobilization: A General Dissociation between Ventromedial and Dorsomedial Prefrontal Cortex

Deciding on a course of action requires both an accurate estimation of option values and the right amount of effort invested in deliberation to reach sufficient confidence in the final choice. In a previous study, we have provided evidence, across a series of judgment and choice tasks, for a dissociation between the ventromedial prefrontal cortex (vmPFC), which would represent option values, and the dorsomedial prefrontal cortex (dmPFC), which would represent the duration of deliberation. Here, we first replicate this dissociation and extend it to the case of an instrumental learning task, in which 24 human volunteers (13 women) choose between options associated with probabilistic gains and losses. According to fMRI data recorded during decision-making, vmPFC activity reflects the sum of option values generated by a reinforcement learning model and dmPFC activity the deliberation time. To further generalize the role of the dmPFC in mobilizing effort, we then analyze fMRI data recorded in the same participants while they prepare to perform motor and cognitive tasks (squeezing a handgrip or making numerical comparisons) to maximize gains or minimize losses. In both cases, dmPFC activity is associated with the output of an effort regulation model, and not with response time. Taken together, these results strengthen a general theory of behavioral control that implicates the vmPFC in the estimation of option values and the dmPFC in the energization of relevant motor and cognitive processes.

I like therefore I can, and I can therefore I like: the role of self-efficacy and affect in active inference of allostasis

Active inference (AIF) is a theory of the behavior of information-processing open dynamic systems. It describes them as generative models (GM) generating inferences on the causes of sensory input they receive from their environment. Based on these inferences, GMs generate predictions about sensory input. The discrepancy between a prediction and the actual input results in prediction error. GMs then execute action policies predicted to minimize the prediction error. The free-energy principle provides a rationale for AIF by stipulating that information-processing open systems must constantly minimize their free energy (through suppressing the cumulative prediction error) to avoid decay. The theory of homeostasis and allostasis has a similar logic. Homeostatic set points are expectations of living organisms. Discrepancies between set points and actual states generate stress. For optimal functioning, organisms avoid stress by preserving homeostasis. Theories of AIF and homeostasis have recently converged, with AIF providing a formal account for homeo- and allostasis. In this paper, we present bacterial chemotaxis as molecular AIF, where mutual constraints by extero- and interoception play an essential role in controlling bacterial behavior supporting homeostasis. Extending this insight to the brain, we propose a conceptual model of the brain homeostatic GM, in which we suggest partition of the brain GM into cognitive and physiological homeostatic GMs. We outline their mutual regulation as well as their integration based on the free-energy principle. From this analysis, affect and self-efficacy emerge as the main regulators of the cognitive homeostatic GM. We suggest fatigue and depression as target neurocognitive phenomena for studying the neural mechanisms of such regulation.

Not all discounts are created equal: Regional activity and brain networks in temporal and effort discounting

Reward outcomes associated with costs like time delay and effort investment are generally discounted in decision-making. Standard economic models predict rewards associated with different types of costs are devalued in a similar manner. However, our review of rodent lesion studies indicated partial dissociations between brain regions supporting temporal- and effort-based decision-making. Another debate is whether options involving low and high costs are processed in different brain substrates (dual-system) or in the same regions (single-system). This research addressed these issues using coordinate-based, connectivity-based, and activation network-based meta-analyses to identify overlapping and separable neural systems supporting temporal (39 studies) and effort (20 studies) discounting. Coordinate-based activation likelihood estimation and resting-state connectivity analyses showed immediate-small reward and delayed-large reward choices engaged distinct regions with unique connectivity profiles, but their activation network mapping was found to engage the default mode network. For effort discounting, salience and sensorimotor networks supported low-effort choices, while the frontoparietal network supported high-effort choices. There was little overlap between the temporal and effort networks. Our findings underscore the importance of differentiating different types of costs in decision-making and understanding discounting at both regional and network levels.

The dorsomedial prefrontal cortex represents subjective value across effort-based and risky decision-making

Decisions that require taking effort costs into account are ubiquitous in real life. The neural common currency theory hypothesizes that a particular neural network integrates different costs (e.g., risk) and rewards into a common scale to facilitate value comparison. Although there has been a surge of interest in the computational and neural basis of effort-related value integration, it is still under debate if effort-based decision-making relies on a domain-general valuation network as implicated in the neural common currency theory. Therefore, we comprehensively compared effort-based and risky decision-making using a combination of computational modeling, univariate and multivariate fMRI analyses, and data from two independent studies. We found that effort-based decision-making can be best described by a power discounting model that accounts for both the discounting rate and effort sensitivity. At the neural level, multivariate decoding analyses indicated that the neural patterns of the dorsomedial prefrontal cortex (dmPFC) represented subjective value across different decision-making tasks including either effort or risk costs, although univariate signals were more diverse. These findings suggest that multivariate dmPFC patterns play a critical role in computing subjective value in a task-independent manner and thus extend the scope of the neural common currency theory.

Does decision confidence reflect effort?

Goal directed behaviour requires transformation of sensory input to decision, and then to output action. How the sensory input is accumulated to form the decision has been extensively studied, however, the influence of output action on decision making has been largely dismissed. Although the recent emerging view postulates the reciprocal interaction between action and decision, still little is known about how the parameters of an action modulates the decision. In this study, we focused on the physical effort which necessarily entails with action. We tested if the physical effort during the deliberation period of the perceptual decision, not the effort required after deciding a particular option, can impact on the process of forming the decision. Here, we set up an experimental situation where investing effort is necessary for the initiation of the task, but importantly, is orthogonal to success in task performance. The study was pre-registered to test the hypothesis that the increased effort will decrease the metacognitive accuracy of decision, without affecting the decision accuracy. Participants judged the direction of a random-dot motion stimuli, while holding and maintaining the position of a robotic manipulandum with their right hand. In the key experimental condition, the manipulandum produced force to move away from its position, requiring the participants to resist the force while accumulating the sensory evidence for the decision. The decision was reported by a key-press using the left-hand. We found no evidence that such incidental (i.e., non-instrumental) effort may influence the subsequent decision process and most importantly decision confidence. The possible reason for this result and the future direction of the research are discussed.

Gender Impacts the Relationship between Mood Disorder Symptoms and Effortful Avoidance Performance

We must often decide how much effort to exert or withhold to avoid undesirable outcomes or obtain rewards. In depression and anxiety, levels of avoidance can be excessive and reward-seeking may be reduced. Yet outstanding questions remain about the links between motivated action/inhibition and anxiety and depression levels, and whether they differ between men and women. Here, we examined the relationship between anxiety and depression scores, and performance on effortful active and inhibitory avoidance (Study 1) and reward seeking (Study 2) in humans. Undergraduates and paid online workers ([Formula: see text] = 545, [Formula: see text] = 310; [Formula: see text] = 368, [Formula: see text] = 450, [Formula: see text] = 22.58, [Formula: see text] = 17-62) were assessed on the Beck Depression Inventory II (BDI) and the Beck Anxiety Inventory (BAI) and performed an instructed online avoidance or reward-seeking task. Participants had to make multiple presses on active trials and withhold presses on inhibitory trials to avoid an unpleasant sound (Study 1) or obtain points toward a monetary reward (Study 2). Overall, men deployed more effort than women in both avoidance and reward-seeking, and anxiety scores were negatively associated with active reward-seeking performance based on sensitivity scores. Gender interacted with anxiety scores and inhibitory avoidance performance, such that women with higher anxiety showed worse avoidance performance. Our results illuminate effects of gender in the relationship between anxiety and depression levels and the motivation to actively and effortfully respond to obtain positive and avoid negative outcomes.

Value, Confidence, Deliberation: A Functional Partition of the Medial Prefrontal Cortex Demonstrated across Rating and Choice Tasks

Deciding about courses of action involves minimizing costs and maximizing benefits. Decision neuroscience studies have implicated both the ventral and dorsal medial PFC (vmPFC and dmPFC) in signaling goal value and action cost, but the precise functional role of these regions is still a matter of debate. Here, we suggest a more general functional partition that applies not only to decisions but also to judgments about goal value (expected reward) and action cost (expected effort). In this conceptual framework, cognitive representations related to options (reward value and effort cost) are dissociated from metacognitive representations (confidence and deliberation) related to solving the task (providing a judgment or making a choice). We used an original approach aimed at identifying consistencies across several preference tasks, from likeability ratings to binary decisions involving both attribute integration and option comparison. fMRI results in human male and female participants confirmed the vmPFC as a generic valuation system, its activity increasing with reward value and decreasing with effort cost. In contrast, more dorsal regions were not concerned with the valuation of options but with metacognitive variables, confidence being reflected in mPFC activity and deliberation time in dmPFC activity. Thus, there was a dissociation between the effort attached to choice options (represented in the vmPFC) and the effort invested in deliberation (represented in the dmPFC), the latter being expressed in pupil dilation. More generally, assessing commonalities across preference tasks might help in reaching a unified view of the neural mechanisms underlying the cost/benefit tradeoffs that drive human behavior.SIGNIFICANCE STATEMENT Decision neuroscience studies have implicated the medial PFC in forming the cognitive representations that drive human choice behavior. However, different studies using different tasks have suggested somewhat inconsistent links between precise computational variables and specific brain regions. Here, we use fMRI to demonstrate a robust functional partition of the medial PFC that generalizes across tasks involving an estimation of goal value and/or action cost to provide a judgment or make a choice. This general functional partition makes a critical dissociation between neural representations of decisional factors (the expected costs and benefits attached to a given option) and metacognitive estimates (confidence in the judgment or choice, and effort invested in the deliberation process).

Altered motivation of effortful decision-making for self and others in subthreshold depression

BACKGROUND

Amotivation is a typical feature in major depressive disorders and refers to individuals exhibiting reduced willingness to exert effort for rewards. However, the motivation pattern when deciding whether to exert effort for self versus others in people with depression remains unclear.

METHODS

We conducted a functional magnetic resonance imaging study and employed an adapted Effort-Expenditure for Rewards Task in subthreshold depressive (SD) participants (n = 33) and healthy controls (HC) (n = 32). This required participants to choose between a fixed low-effort/low-reward and a variable high-effort/high-reward option, and then immediately exert effort to obtain corresponding rewards for themselves or for unfamiliar people.

RESULTS

Compared with the HC group, the SD group showed blunted activity in the left dorsal anterior cingulate cortex/dorsomedial prefrontal cortex, bilateral anterior insula (AI), and right putamen-left dorsolateral prefrontal cortex functional connectivity when choosing to exert effort for themselves. Additionally, the SD group exhibited increased willingness and greater activation in the bilateral AI when choosing to exert effort for others. Furthermore, these brain activations and functional connectivity were positively related to self-reported motivation.

CONCLUSIONS

These findings show altered motivation during effort-based decision-making in individuals with the mild depressive state, particularly with higher motivation for others. Thus, this suggests that motivational behaviors and prefrontal-striatal circuitry are altered in individuals with SD, which can be utilized to discover treatment targets and develop strategies to address mental illness caused by motivation disorders.

The neural basis of effort valuation: A meta-analysis of functional magnetic resonance imaging studies

Choosing how much effort to expend is critical for everyday decisions. While several neuroimaging studies have examined effort-based decision-making, results have been highly heterogeneous, leaving unclear which brain regions process effort-related costs and integrate them with rewards. We conducted two meta-analyses of functional magnetic resonance imaging data to examine consistent neural correlates of effort demands (23 studies, 15 maps, 549 participants) and net value (15 studies, 11 maps, 428 participants). The pre-supplementary motor area (pre-SMA) scaled positively with pure effort demand, whereas the ventromedial prefrontal cortex (vmPFC) showed the opposite effect. Moreover, regions that have been previously implicated in value integration in other cost domains, such as the vmPFC and ventral striatum, were consistently involved in signaling net value. The opposite response patterns of the pre-SMA and vmPFC imply that they are differentially involved in the representation of effort costs and value integration. These findings provide conclusive evidence that the vmPFC is a central node for net value computation and reveal potential brain targets to treat motivation-related disorders.

Relationship of ventral striatum activation during effort discounting to clinical amotivation severity in schizophrenia

Motivational deficits play a central role in disability due to negative symptoms of schizophrenia (SZ), but limited pathophysiological understanding impedes critically needed therapeutic development. We applied an fMRI Effort Discounting Task (EDT) that quantifies motivation using a neuroeconomic decision-making approach, capturing the degree to which effort requirements produce reductions in the subjective value (SV) of monetary reward. An analyzed sample of 21 individuals with SZ and 23 group-matched controls performed the EDT during fMRI. We hypothesized that ventral striatum (VS) as well as extended brain motivation circuitry would encode SV, integrating reward and effort costs. We also hypothesized that VS hypoactivation during EDT decisions would demonstrate a dimensional relationship with clinical amotivation severity, reflecting greater suppression by effort costs. As hypothesized, VS as well as a broader cortico-limbic network were activated during the EDT and this activation correlated positively with SV. In SZ, activation to task decisions was reduced selectively in VS. Greater VS reductions correlated with more severe clinical amotivation in SZ and across all participants. However, these diagnosis and amotivation effects could not be explained by the response to parametric variation in reward, effort, or model-based SV. Our findings demonstrate that VS hypofunction in schizophrenia is manifested during effort-based decisions and reflects dimensional motivation impairment. Dysfunction of VS impacting effort-based decision-making can provide a target for biomarker development to guide novel efforts to assess and treat disabling amotivation.

Anticipatory Energization Revealed by Pupil and Brain Activity Guides Human Effort-Based Decision Making

An organism's fitness is determined by how it chooses to adapt to effort in response to challenges. Exertion of effort correlates with activity in dorsomedial prefrontal cortex (dmPFC) and noradrenergic pupil dilation, but little is known about the role of these neurophysiological processes for decisions about future efforts, they may provide anticipatory energization to help us accept the challenge or a cost representation that is weighted against the expected rewards. Here, we provide evidence for the former, by measuring pupil and functional magnetic resonance imaging (fMRI) brain responses while 52 human participants (29 females) chose whether to exert efforts to obtain rewards. Both pupil-dilation rate and dmPFC fMRI activity increased with anticipated effort level, and these increases differ depending on the choice outcome: they were stronger when participants chose to accept the challenge compared with when the challenge was declined. Crucially, the choice-dependent modulation of pupil and brain-activity effort representations were stronger in participants whose behavioral choices were more sensitive to effort. Our results identify a process involving the peripheral and central human nervous system that simulates the required energization before overt response, suggesting a role in guiding effort-based decisions.SIGNIFICANCE STATEMENT The brain's arousal system tracks the effort we engage in during strenuous activity. But much less is known about what role this effort signaling may play when we decide whether to exert effort in the future. Here, we characterize pupil-linked arousal and brain signals that guide decisions whether to engage in effort to gain money. During such choices, increases in brain activity and pupil dilation correlated with the effort involved in the chosen option, and these increases were stronger when people decided to accept the effort compared with when they rejected it. These results suggest that the brain arousal system guides decisions by energizing the organism for the prospective challenge.

Mind wandering increases linearly with text difficulty

Although mind wandering during reading is known to be affected by text difficulty, the nature of this relationship is not yet fully understood. To examine this issue, we conducted an experiment in which participants read non-fiction texts that varied along five levels of difficulty under naturalistic conditions. Difficulty levels were determined based on Flesch-Kincaid Grade Levels and verified with Coh-Metrix indices. Mind wandering was measured with thought probes. We predicted that text difficulty and mind wandering have a U-shaped (i.e., quadratic) relationship. Contrary to our expectations, but in line with some prior studies, mind wandering linearly increased with text difficulty. Additionally, text interest moderated the effect of text difficulty on mind wandering. Finally, mind wandering was associated with worse performance on a comprehension test. Together, our findings extend previous work by showing that (a) a linear relationship between difficulty and mind wandering exists during common page-by-page reading of pre-existing texts and that (b) this relationship holds across a broad range of difficulty levels.

Distinct regions of the striatum underlying effort, movement initiation and effort discounting

The ventral striatum is believed to encode the subjective value of cost-benefit options; however, this effect has notably been absent during choices that involve physical effort. Previous work in freely moving animals has revealed opposing striatal signals, with greater response to increasing effort demands and reduced responses to rewards requiring effort. Yet, the relationship between these conflicting signals remains unknown. Using functional magnetic resonance imaging with a naturalistic maze-navigation paradigm, we identified functionally segregated regions within the ventral striatum that separately encoded effort activation, movement initiation and effort discounting of rewards. In addition, activity in regions associated with effort activation and discounting oppositely predicted striatal encoding of effort during effort-based decision-making. Our results suggest that the dorsomedial region hitherto associated with action may instead represent the cost of effort and raise fundamental questions regarding the interpretation of striatal 'reward' signals in the context of effort demands. This has implications for uncovering the neural architecture underlying motivated behaviour.

Neural synchronization between the anterior cingulate and orbitofrontal cortices during effort-based decision making

Optimal decision making reflects the ability to choose the most advantageous option for various alternatives so that the anterior cingulate cortex is an important area involved in effort-based decision making. The current study aimed to investigate the functional connectivity between the ACC (anterior cingulate cortex) and the orbitofrontal cortex (OFC) during effort-based decision-making. A T-maze decision-making task with different rewards (large vs. small reward) and costs (high vs. low effort) was used, and simultaneously, local field potentials (LFP) from the ACC and OFC were also recorded in male Wistar rats. During the effort-based decision making, when the animals preferred the higher over, the lower reward, neural synchronization was observed in theta/low beta (4-20 Hz) frequency bands between both of the areas. Also, neural synchronization was not significant when the animals chose a lower reward. High gamma (80-100 Hz) synchrony between the areas was also observed; however, it was not dependent on the animal's decision. In this regard, the present findings revealed that neural synchronization and functional connectivity between the ACC and OFC in the low-frequency range (theta/low beta) is essential during the effort-based decision making.

Evaluation of cognitive effort in rats is not critically dependent on ventrolateral orbitofrontal cortex

Organisms must frequently evaluate the amount of effort to invest in pursuing future rewards. Despite explicit awareness of the potential benefits of cognitive work, individuals vary in their willingness to attempt cognitively demanding tasks, regardless of intellectual ability. Such differences may suggest that the degree to which cognitive effort degrades perceived outcome value is a subjective, rather than objective, process, similar to risk and delay discounting. Although numerous studies suggest the orbitofrontal cortex (OFC) is important for allowing subjective value estimates to be updated and/or used in cost/benefit decision-making, the causal role of the OFC in valuations of mental effort has received scant investigation. We therefore trained 24 female Long-Evans rats on the rodent cognitive effort task (rCET) and assessed performance following temporary bilateral inactivation of the ventrolateral OFC (vlOFC). In the rCET, rats decide at trial outset whether to perform an easy or hard attentional challenge, namely to localize a brief visual stimulus to one of five possible locations. The difficulty of the challenge is determined by the stimulus duration (1.0 vs. 0.2s for easy vs. hard trials respectively), and success on hard trials results in double the sugar pellet rewards. Somewhat surprisingly, inactivations of the vlOFC did not affect rats' willingness or ability to exert cognitive effort for larger rewards, despite increasing omissions and motor impulsivity on-task. When considered with previous work, it appears the vlOFC plays a minimal role in cognitive effort allocation specifically, and in valuations of effort more generally.

Neural mechanisms underlying the effects of physical fatigue on effort-based choice

Physical fatigue crucially influences our decisions to partake in effortful action. However, there is a limited understanding of how fatigue impacts effort-based decision-making at the level of brain and behavior. We use functional magnetic resonance imaging to record markers of brain activity while human participants engage in uncertain choices for prospective physical effort, before and after bouts of exertion. Using computational modeling of choice behavior we find that fatiguing exertions cause participants to increase their subjective cost of effort, compared to a baseline/rested state. We describe a mechanism by which signals related to motor cortical state in premotor cortex influence effort value computations, instantiated by insula, thereby increasing an individual's subjective valuation of prospective physical effort while fatigued. Our findings provide a neurobiological account of how information about bodily state modulates decisions to engage in physical activity.

Redefining the relationship between effort and reward: Choice-execution model of effort-based decisions

Neuroscientific studies reliably demonstrate that rewards play a crucial role in guiding our choices when confronted with different effortful actions we could make. At the same time, psychological and economic research shows that effort we exert is not reliably predicted by the rewards we end up receiving. Why the mismatch between the two lines of evidence? Inspired by neuroscientific literature, we argue that value-based models of decision-making expose the complexity of the relationship between effort and reward, which changes between two crucial stages of the effort-based decision making process: Choice (i.e. action selection) and Execution (i.e. action execution involving actual effort exertion). To test this assumption, in the present study we set up two experiments (E1: N = 72, E2: N = 87), using a typical neuroscientific effort-based decision-making task. The findings of these experiments reveal that when making prospective choices, rewards do guide the level of effort people are prepared to exert, consistent with typical findings from Neuroscience. At a later stage, during execution of effortful actions, performance is determined by the actual amount of effort that needs to be exerted, consistent with psychological and behavioral economic research. We use the model we tested and the findings we generated to highlight critical new insights into effort-reward relationship, bringing different literatures together in the context of questions regarding what effort its, and the role that values play.

Emotional content impacts how executive function ability relates to willingness to wait and to work for reward

Research has demonstrated that better value-based decision making (e.g., waiting or working for rewards) relates to greater executive function (EF) ability. However, EF is not a static ability, but is influenced by the emotional content of the task. As such, EF ability in emotional contexts may have unique associations with value-based decision making, in which costs and benefits are explicit. Participants (N = 229) completed an EF task (with both negative and neutral task conditions) and two value-based decision-making tasks. Willingness to wait and to work were evaluated in separate path models relating the waiting and working conditions to the EF conditions. Willingness to wait and willingness to work showed distinct relationships with EF ability: Greater EF ability on a negative, but not on a neutral, EF task was related to a willingness to wait for a reward, whereas greater EF ability across both EF tasks was related to a greater willingness to work for a reward. EF ability on a negative EF task showed an inverted-U relationship to willingness to wait for reward, and was most related to willingness to wait at a 6-month delay. Greater EF, regardless of whether the task was negative or neutral, was related to a greater willingness to work when reward was uncertain (50%) or was likely (88%), but not when reward was unlikely (12%). This study suggests that the emotional content of value-based decisions impacts the relationship between EF ability and willingness to wait or to work for reward.

The Subjective Value of Cognitive Effort is Encoded by a Domain-General Valuation Network

Cognitive control is necessary for goal-directed behavior, yet people treat cognitive control demand as a cost, which discounts the value of rewards in a similar manner as other costs, such as delay or risk. It is unclear, however, whether the subjective value (SV) of cognitive effort is encoded in the same putatively domain-general brain valuation network implicated in other cost domains, or instead engages a distinct frontoparietal network, as implied by recent studies. Here, we provide rigorous evidence that the valuation network, with core foci in the ventromedial prefrontal cortex and ventral striatum, also encodes SV during cognitive effort-based decision-making in healthy, male and female adult humans. We doubly dissociate this network from frontoparietal regions that are instead recruited as a function of decision difficulty. We show that the domain-general valuation network jointly and independently encodes both reward benefits and cognitive effort costs. We also demonstrate that cognitive effort SV signals predict choice and are influenced by state and trait motivation, including sensitivity to reward and anticipated task performance. These findings unify cognitive effort with other cost domains, and suggest candidate neural mechanisms underlying state and trait variation in willingness to expend cognitive effort.SIGNIFICANCE STATEMENT Subjective effort costs are increasingly understood to diminish cognitive control over task performance and can thus undermine functioning across health and disease. Yet, we are only beginning to understand how decisions about cognitive effort are made. A key question is how subjective values are computed. Recent work suggests that the value of cognitive effort might be computed by networks that are distinct from those involved in other domains like intertemporal and risky decision-making, implying distinct mechanisms. Here we demonstrate that the domain-general network also encodes effort-discounted value, linking cognitive effort closely with other domains. Our results thus elucidate key mechanisms supporting decisions about cognitive effort, and point to candidate neural targets for intervention in disorders involving impaired cognitive motivation.

Sleep deprivation, effort allocation and performance

Sleep deprivation causes physiological alterations (e.g., decreased arousal, intrusion of micro-sleeps), that negatively affect performance on a wide range of cognitive domains. These effects indicate that cognitive performance relies on a capacity-limited system that may be more challenged in the absence of sleep. Additionally, sleep loss can result in a lower willingness to exert effort in the pursuit of performance goals. Such deficits in motivation may interact with the effects of capacity limitations to further stifle cognitive performance. When sleep-deprived, cognitive performance is experienced as more effortful, and intrinsic motivation to perform dwindles. On the other hand, increasing motivation extrinsically (e.g., by monetary incentives) can inspire individuals to allocate more task-related effort, and can partially counter performance deficits associated with sleep deprivation. In this chapter, we review current research on the interplay between sleep deprivation, effort and performance. We integrate these findings into an effort-based decision-making framework in which sleep-related performance impairments may result from a voluntary decision to withdraw effort. We conclude with practical implications of this framework for performance in healthy populations (e.g., work productivity) and clinical conditions.