Neural mechanisms underlying motivation of mental versus physical effort

Functional dysconnectivity of the triple network in women with premenstrual syndrome

OBJECTIVE

Premenstrual syndrome (PMS) is a risk factor for female depression, linked to neural circuit dysfunction. This study investigates PMS-related brain network patterns, focusing on the triple network's integration and segregation.

MATERIALS & METHODS

The study enrolled 56 PMS patients and 67 healthy controls (HCs), assessed via the Daily Record of Severity of Problems (DRSP). Functional MRI (fMRI) was analyzed using independent component analysis (ICA) to calculate functional connectivity (FC) and functional network connectivity (FNC) within and between brain networks. Correlation analysis examined links between imaging metrics and DRSP scores.

RESULTS

Compared with HCs, PMS patients showed increased FC in the left inferior frontal gyrus of the salience network (SN). Additionally, there was increased FNC between the dorsal default mode network (dDMN), while a decrease was observed between the right execution network (RECN) and SN. Conversely, the FNC between RECN and dDMN was enhanced. Significant correlations were found between the FC values within the SN and DRSP scores. Similarly, the abnormal FNC pattern also correlated significantly with DRSP scores.

CONCLUSION

Triple-network dysconnectivity may serve as a biomarker for PMS, offering insights into its pathophysiology and potential targets for network-based neuromodulation therapies.

CLINICAL RELEVANCE STATEMENT

Identifying network dysconnectivities in PMS offers potential biomarkers for diagnosis and targets for neuromodulation therapy, ultimately improving symptom management and patient outcomes.

From social effort to social behavior: An integrated neural model for social motivation

As humans rely on social groups for survival, social motivation is central to behavior and well-being. Here we define social motivation as the effort that initiates and directs behavior towards social outcomes, with the goal of satisfying our fundamental need for connection. We propose an integrated framework of social motivation which emphasizes the maintenance of optimal connection levels through effort exertion, regulating social approach and avoidance, which allow interpersonal synchrony. Together, these behaviors serve as basic building blocks of social behavior, and give rise to behaviors critical for collective living such as cooperation and empathy. We describe a neural model according to which social connection levels are monitored by the hypothalamus, while the anterior cingulate cortex and anterior insula respond to detected social deficiency. As adjustment is required, the social effort system - comprised of the thalamus and striatum - is activated. This system directs neural networks that permit interpersonal synchrony or, conversely, desynchronization, aiming to restore and maintain optimal connection by preventing isolation on the one hand, and exaggerated social closeness on the other hand. The proposed framework offers insights into disorders characterized by aberrant social motivation, potentially identifying neural dysfunctions that may inform novel interventions.

Motivational disturbances and cognitive effort-based decision-making in Parkinson's disease

BACKGROUND

Motivational disturbances, such as apathy and impulse control disorders (ICDs), frequently co-occur in patients with Parkinson's disease (PD). The assessment of these motivational disturbances has proven to be challenging due the absence of validated objective behavioral measures for evaluating motivation in older adults. This scenario may contribute to underdiagnosis. The present study aimed to investigate the clinical utility of a modified version of an existing effort-based decision-making task which required cognitive (e.g., working memory) instead of physical (e.g., finger tapping) effort.

METHODS

Ninety-five non-demented individuals (45-85 years of age) with idiopathic PD completed a cognitive screening measure, self-report questionnaires, and a cognitive adaptation of the Effort Expenditure for Rewards Task (COG-EEfRT), which is a multi-trial game where a participant can choose whether to expend greater effort for larger rewards which vary in magnitude and probability. Patients were classified as having clinically significant symptoms of apathy and/or an ICD based on recommended cut-off scores on the Apathy Scale (AS) and Questionnaire for Impulse Control Disorders in Parkinson's Disease - Rating Scale (QUIP-RS). The methodological cutoffs defined two groups: Apathy (36.8 %), and ICD (48.4 %).

RESULTS

The level of effort expended by patients significantly predicted apathy and ICD status with high accuracy (88.2 % and 82.4 %, respectively), above and beyond age, levodopa equivalent dose and self-report measures of motivation. Additionally, we found that greater symptoms of apathy and ICD (i.e., negative urgency) were significantly correlated with patients choosing to expend greater effort. This result varied based on reward probability and outcome.

CONCLUSION

We offer preliminary evidence suggesting the clinical utility of the COG-EEfRT for identifying and quantifying motivational disturbances in PD. Additionally, anticipatory anhedonia and impulsive traits may be important predictors of cognitive effort-based decision-making. Compared to tasks requiring physical effort, the COG-EEfRT may be a more suitable tool for PD and perhaps for people with motor impairment.

Make it worth it: Effort-reward modulations on reinforcement-learning and prediction-error signaling across adolescence

Adolescence is characterized by significant shifts in effort allocation. A well-known neuro-economic framework suggests that rewards help overcome potential effort costs. However, few studies have examined the neurobiological mechanisms by which rewards and associated effort costs drive adolescent learning. This study utilized functional magnetic resonance imaging in a sample of adolescents (N = 146, 13-25 years) and employed a reinforcement-learning paradigm that manipulated effort and reward levels, by varying task demands and varying potential rewards. The analysis of trial-by-trial learning signals (reward prediction errors) and behavioral learning performance demonstrated that greater reward levels enhanced adolescent learning, especially when faced with greater effort demands. Moreover, this effect was more pronounced in those experiencing greater effort demands: younger adolescents and adolescents who place less value on effort for demanding tasks. Neuroimaging results revealed that the dorsal anterior cingulate cortex (dACC) was a key region in signaling the interaction between reward and effort demands. That is, greater reward strengthened prediction error coding in the dACC, particularly under conditions of greater task demands, with these effects being more pronounced in younger adolescents and adolescents who place less value on effort for demanding tasks. These findings support a role for dACC in the engagement of cognitive control, especially in situations where more cognitive control would be beneficial despite its associated effort costs, such as in high-demanding learning situations. This comprehensive approach aims to inform strategies for supporting effort allocation in learning during this crucial developmental period.

A randomized proof-of-mechanism trial of TNF antagonism for motivational deficits and related corticostriatal circuitry in depressed patients with high inflammation

Chronic, low-grade inflammation has been associated with motivational deficits in patients with major depression (MD). In turn, impaired motivation has been linked to poor quality of life across psychiatric disorders. We thus determined effects of the anti-inflammatory drug infliximab-a potent tumor necrosis factor (TNF) antagonist-on behavioral and neural measures of motivation in 42 medically stable, unmedicated MD patients with a C-reactive protein >3 mg/L. All patients underwent a double-blind, placebo-controlled, single-dose, randomized clinical trial with infliximab (5 mg/kg) versus placebo. Behavioral performance on an effort-based decision-making task, self-report questionnaires, and neural responses during event-related functional magnetic resonance imaging were assessed at baseline and 2 weeks following infusion. We found that relative to placebo, patients receiving infliximab were more willing to expend effort for rewards. Moreover, increase in effortful choices was associated with reduced TNF signaling as indexed by decreased soluble TNF receptor type 2 (sTNFR2). Changes in effort-based decision-making and sTNFR2 were also associated with changes in task-related activity in a network of brain areas, including dorsomedial prefrontal cortex (dmPFC), ventral striatum, and putamen, as well as the functional connectivity between these regions. Changes in sTNFR2 also mediated the relationships between drug condition and behavioral and neuroimaging measures. Finally, changes in self-reported anhedonia symptoms and effort-discounting behavior were associated with greater responses of an independently validated whole-brain predictive model (aka "neural signature") sensitive to monetary rewards. Taken together, these data support the use of anti-inflammatory treatment to improve effort-based decision-making and associated brain circuitry in depressed patients with high inflammation.

The role of uncertain reward in voluntary task-switching as revealed by pupillometry and gaze

Cognitive flexibility, the brain's ability to adjust to changes in the environment, is a critical component of executive functioning. Previous literature shows a robust relationship between reward dynamics and flexibility: flexibility is highest when reward changes, while flexibility decreases when reward remains stable. The purpose of this study was to examine the role of uncertain reward in a voluntary task switching paradigm on behavior, pupillometry, and eye gaze. We used pupil dilation as a neuropsychological correlate of arousal and accumulated fixations on a region (i.e. dwell time) to measure oculomotor attention capture. Results during the cue phase showed that pupil dilation under a deterministic, but not a stochastic reinforcement schedule tracked arousal from the magnitude of reward. In addition, dwell time was increased for the eventual choice and dwell-time was reduced under high reward. Taken together, results show that arousal and attentional capture by reward depends to some extent on reward certainty. Turning to reward outcome, pupil dilation was highest (and average dwell time was lowest) following Error feedback compared to correct rewarded feedback. Overall results show that uncertain reward cues may alter pupil-linked arousal and attention as compared to certain reward, highlighting the role of uncertainty as an important modulator affecting attention and reward processing in environments that demand cognitive flexibility.

A neurometabolic mechanism involving dmPFC/dACC lactate in physical effort-based decision-making

Motivation levels vary across individuals, yet the underlying mechanisms driving these differences remain elusive. The dorsomedial prefrontal cortex/dorsal anterior cingulate cortex (dmPFC/dACC) and the anterior insula (aIns) play crucial roles in effort-based decision-making. Here, we investigate the influence of lactate, a key metabolite involved in energy metabolism and signaling, on decisions involving both physical and mental effort, as well as its effects on neural activation. Using proton magnetic resonance spectroscopy and functional MRI in 63 participants, we find that higher lactate levels in the dmPFC/dACC are associated with reduced motivation for physical effort, a relationship mediated by neural activity within this region. Additionally, plasma and dmPFC/dACC lactate levels correlate, suggesting a systemic influence on brain metabolism. Supported by path analysis, our results highlight lactate's role as a modulator of dmPFC/dACC activity, hinting at a neurometabolic mechanism that integrates both peripheral and central metabolic states with brain function in effort-based decision-making.

Getting a grip on visual search: Relating effort exertion to the control of attention

Humans are generally biased to conserve energy, limiting the exertion of physical and mental effort. The need for attention to selectively process perceptual information is a ubiquitous part of mental life, but how mentally effortful is the process of finding the target of a visual search, and how much mental effort is required to focus attention in the face of potentially distracting stimuli? Does learning from demands on physical effort shape the control of attention, much like rewards and punishments? In this tutorial review, we provide an overview of a novel approach to probing the mental effort involved in visual search and the control of attention more generally. Situations are created in which exerting physical effort, via a hand dynamometer, can modify the demands of a visual search task. More specifically, participants can exert physical effort to reduce the putative mental effort required to find a target. When comparing across search conditions, this approach can reveal the conditions that participants are willing to physically work to achieve, with implications for the mental effort associated with these conditions. We also introduce a reciprocal approach in which demands on physical effort, and their association with the visual search task, are manipulated, providing an opportunity to examine how the control of attention is shaped by these effort demands. Some practical considerations for the implementation of these novel approaches are discussed, as are potential new research directions for which these approaches are well suited.

Approach and withdrawal from cognitively effortful activities: Development, validation, and transdiagnostic clinical utility of a cognitive motivation scale

BACKGROUND

Deficits in cognition and motivation predict functioning in depressive and psychotic disorders. However, experimental tasks of cognitive motivation are inconsistently correlated with functioning, time-intensive, and not intuitive in clinical practice. We aimed to develop and validate a self-report instrument to assess motivation processes pertinent to engagement with cognitive activities in daily life.

METHOD

Following item generation, scale dimensionality, reliability, and validity were evaluated iteratively over Studies 1-3 with online general adult participants (n1 = 205; n2 = 235; n3 = 181). The 20-item Cognitive Motivation scale was also validated in a Study 3 sub-sample reporting high levels of depressive symptoms (n = 74) and Study 4 early psychosis outpatients (n = 25).

RESULTS

Two-factor model of cognitive approach and cognitive withdrawal, each with good internal consistency, convergent validity, discriminant validity was supported. Cognitive withdrawal showed stronger associations with cognitive difficulties, depressive symptoms, and functional impairments than traditional motivation scale. Participants reporting high depression levels showed more severe difficulties with cognitive motivation than participants reporting low depression levels. In early psychosis outpatients, correlations with functioning and cognitive effort expenditure provided support for scale validity.

LIMITATIONS

Cross-sectional data collection restricted evaluation of repeated administration psychometric properties. Scale validation was mostly established in online community samples and a small patient sample during the COVID-19 pandemic, thereby limiting generalizability of clinical applications.

CONCLUSIONS

Cognitive Motivation scale is a promising tool for future intervention trials seeking to target motivational processes associated with functioning in the general population and potentially across patient groups with amotivation symptoms.

Abnormal hedonic process in patients with stable schizophrenia: Relationships to negative symptoms and social functioning

BACKGROUND

Anhedonia is a deficit of dynamic reward process, and a large proportion of schizophrenia patients continue to experience anhedonia even during the stable phase. However, few studies have examined the multiple aspects of performance in reward processing in patients with stable schizophrenia and evidence suggests that physical and cognitive effort may involve different neural mechanisms.

METHODS

Parallel measures of effort-based expenditure for reward tasks (EEfRT) and self-report questionnaires of pleasure were applied in 61 patients with stable schizophrenia (SSZ) and 46 healthy controls (HCs), and percentages of hard task choices (HTC%) were used to assess motivation in reward processing. Negative symptoms, neurocognitive and social function were evaluated in SSZ patients, and associations with performance in reward tasks were explored.

RESULTS

SSZ patients reported more severe consummatory and anticipatory anhedonia and social anhedonia. HTC% in reward tasks of SSZ patients were significantly lower than that of HCs, especially in cognitive-effort tasks. HTC% in cognitive tasks were correlated with motivation and pleasure dimension of negative symptoms, whereas HTC% in physical tasks were associated with expression dimension. Anticipatory anhedonia and negative symptoms were correlated with Personal and Social Performance Scale (PSP) scores.

CONCLUSION

Patients with stable schizophrenia have social anhedonia, physically consummatory and anticipatory anhedonia and reduced reward motivation. They are less willing to make cognitive effort than physical effort for reward. The different associations of physical and cognitive effort with negative symptoms indicate physical and cognitive effort may represent disparate neuropsychological processes. Anticipatory anhedonia is closely related to social functioning.

Exploring breed differences in discrimination, reversal learning, and resistance to extinction in the domestic dog (Canis familiaris)

Learning is crucial for shaping domestic dogs' behaviour through life experiences, yet not all breeds exhibit the same learning aptitude towards a particular task. The current study's objective was to identify differences in behaviour and learning performance across and within five breed clades and elucidate the underlying factors contributing into these variations. Dogs (n = 111) from five breed clades (UK Rural, Retrievers, Asian Spitz, European Mastiff, and New World) participated in a virtual learning task with their owners. Owners completed validated questionnaires of Impulsivity and Reward Responsiveness. The learning task comprised of reinforcing an arbitrary behaviour (hand-touch) through multiple sessions of Acquisition (reinforcing the hand-touch), Discrimination (reinforcing the hand-touch on one of two hands) and Reversal Learning (reinforcing the hand-touch on the opposite hand), followed by a single session of Extinction (hand-touch not reinforced). Results showed notable differences across the studied breed clades in certain learning and behavioural components. However, the observed disparities may not be entirely attributed to inherent cognitive differences among the breed clades but rather potentially influenced by contextual factors such as the human-dog communication dynamics associated with breeds' cooperativity. Furthermore, breed clades differed in the contributing factors predicting individual learning performances, which could highlight the potential effect of breeds' historical function.

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.

Assessing the effectiveness of high frequency repetitive transcranial magnetic stimulation for post-mastectomy pain in breast cancer patients: A randomized controlled trial

BACKGROUND

Post-mastectomy pain Syndrome (PMPS), characterized by chronic neuropathic pain stemming from intercostobrachial nerve lesions, presents a formidable clinical challenge. With the incidence of breast cancer surging, effective interventions for PMPS are urgently needed. To address this, we conducted this double-blind, placebo-controlled, randomized clinical trial to study the efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) therapy over the motor cortex on pain, quality of life and thermal sensitivity in PMPS patients.

METHODS

We delivered 15 rTMS sessions over three weeks in a cohort of 34 PMPS patients. These patients were allocated randomly to either rTMS therapy or sham therapy groups. Pain assessments, utilizing the Visual Analogue Scale (VAS) and Short Form McGill Pain Questionnaire (SF-MPQ), alongside quality-of-life evaluations through the Functional Assessment of Cancer Therapy-Breast (FACT-B), were recorded before and after the 15 sessions. Additionally, we assessed thermal sensitivity using Quantitative Sensory Testing (QST).

RESULTS

Our findings demonstrate the superior efficacy of rTMS therapy (over sham therapy) in reducing VAS and SF-MPQ scores (p < 0.0001), improving physical (p = 0.037), emotional (p = 0.033), and functional well-being (p = 0.020) components of quality of life, as quantified by FACT-B. Our investigation also unveiled marked enhancements in thermal sensitivity within the rTMS therapy group, with statistically significant improvements in cold detection threshold (p = 0.0001), warm detection threshold (p = 0.0033), cold pain threshold (p = 0.0078), and hot pain tolerance threshold (p = 0.0078).

CONCLUSION

The study underscores the profound positive impact of rTMS therapy on pain, quality of life, and thermal sensitivity in patients having PMPS, opening new avenues for pain management strategies.

Beta and theta oscillations track effort and previous reward in the human basal ganglia and prefrontal cortex during decision making

Choosing whether to exert effort to obtain rewards is fundamental to human motivated behavior. However, the neural dynamics underlying the evaluation of reward and effort in humans is poorly understood. Here, we report an exploratory investigation into this with chronic intracranial recordings from the prefrontal cortex (PFC) and basal ganglia (BG; subthalamic nuclei and globus pallidus) in people with Parkinson's disease performing a decision-making task with offers that varied in levels of reward and physical effort required. This revealed dissociable neural signatures of reward and effort, with BG beta (12 to 20 Hz) oscillations tracking effort on a single-trial basis and PFC theta (4 to 7 Hz) signaling previous trial reward, with no effects of net subjective value. Stimulation of PFC increased overall acceptance of offers and sensitivity to reward while decreasing the impact of effort on choices. This work uncovers oscillatory mechanisms that guide fundamental decisions to exert effort for reward across BG and PFC, supports a causal role of PFC for such choices, and seeds hypotheses for future studies.

The effect of Huntington's disease on cognitive and physical motivation

Apathy is one of the most common neuropsychiatric features of Huntington's disease. A hallmark of apathy is diminished goal-directed behaviour, which is characterized by a lower motivation to engage in cognitively or physically effortful actions. However, it remains unclear whether this reduction in goal-directed behaviour is driven primarily by a motivational deficit and/or is secondary to the progressive cognitive and physical deficits that accompany more advanced disease. We addressed this question by testing 17 individuals with manifest Huntington's disease and 22 age-matched controls on an effort-based decision-making paradigm. Participants were first trained on separate cognitively and physically effortful tasks and provided explicit feedback about their performance. Next, they chose on separate trials how much effort they were willing to exert in each domain in return for varying reward. At the conclusion of the experiment, participants were asked to rate their subjective perception of task load. In the cognitive task, the Huntington's disease group were more averse to cognitive effort than controls. Although the Huntington's disease group were more impaired than controls on the task itself, their greater aversion to cognitive effort persisted even after controlling for task performance. This suggests that the lower levels of cognitive motivation in the Huntington's disease group relative to controls was most likely driven by a primary motivational deficit. In contrast, both groups expressed a similar preference for physical effort. Importantly, the similar levels of physical motivation across both groups occurred even though participants with Huntington's disease performed objectively worse than controls on the physical effort task, and were aware of their performance through explicit feedback on each trial. This indicates that the seemingly preserved level of physical motivation in Huntington's disease was driven by a willingness to engage in physically effortful actions despite a reduced capacity to do so. Finally, the Huntington's disease group provided higher ratings of subjective task demand than controls for the cognitive (but not physical) effort task and when assessing the mental (but not the physical) load of each task. Together, these results revealed a dissociation in cognitive and physical motivation deficits between Huntington's disease and controls, which were accompanied by differences in how effort was subjectively perceived by the two groups. This highlights that motivation is the final manifestation of a complex set of mechanisms involved in effort processing, which are separable across different domains of behaviour. These findings have important clinical implications for the day-to-day management of apathy in Huntington's disease.

The effects of reward and punishment on the performance of ping-pong ball bouncing

Introduction

Reward and punishment modulate behavior. In real-world motor skill learning, reward and punishment have been found to have dissociable effects on optimizing motor skill learning, but the scientific basis for these effects is largely unknown.

Methods

In the present study, we investigated the effects of reward and punishment on the performance of real-world motor skill learning. Specifically, three groups of participants were trained and tested on a ping-pong ball bouncing task for three consecutive days. The training and testing sessions were identical across the three days: participants were trained with their right (dominant) hand each day under conditions of either reward, punishment, or a neutral control condition (neither). Before and after the training session, all participants were tested with their right and left hands without any feedback.

Results

We found that punishment promoted early learning, while reward promoted late learning. Reward facilitated short-term memory, while punishment impaired long-term memory. Both reward and punishment interfered with long-term memory gains. Interestingly, the effects of reward and punishment transferred to the left hand.

Discussion

The results show that reward and punishment have different effects on real-world motor skill learning. The effects change with training and transfer readily to novel contexts. The results suggest that reward and punishment may act on different learning processes and engage different neural mechanisms during real-world motor skill learning. In addition, high-level metacognitive processes may be enabled by the additional reinforcement feedback during real-world motor skill learning. Our findings provide new insights into the mechanisms underlying motor learning, and may have important implications for practical applications such as sports training and motor rehabilitation.

The Mesocortical System Encodes the Strength of Subsequent Force Generation

Our minds impact motor outputs. Such mind-motor interactions are critical for understanding motor control mechanisms and optimizing motor performance. In particular, incentive motivation strongly enhances motor performance. Dopaminergic neurons located in the ventral midbrain (VM) are believed to be the center of incentive motivation. Direct projections from the VM to the primary motor cortex constitute a mesocortical pathway. However, the functional role of this pathway in humans remains unclear. Recently, we demonstrated the functional role of the mesocortical pathway in human motor control in the context of incentive motivation by using functional magnetic resonance imaging (fMRI). Incentive motivation remarkably improved not only reaction times but also the peak grip force in subsequent grip responses. Although the reaction time has been used as a proxy for incentive motivation mediated by dopaminergic midbrain activity, the premovement activity of the mesocortical pathway is involved in controlling the force strength rather than the initiation of subsequent force generation. In this commentary, we review our recent findings and discuss remaining questions regarding the functional role of the mesocortical pathway in mind-motor interactions.

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.

A randomized proof-of-mechanism trial of TNF antagonism for motivational anhedonia and related corticostriatal circuitry in depressed patients with high inflammation

Chronic, low-grade inflammation has been associated with motivational deficits in patients with major depression (MD). In turn, impaired motivation has been linked to poor quality of life across psychiatric disorders. We thus determined effects of the anti-inflammatory drug infliximab-a potent tumor necrosis factor (TNF) antagonist-on behavioral and neural measures of motivation in 42 medically stable, unmedicated MD patients with a C-reactive protein > 3mg/L. All patients underwent a double-blind, placebo-controlled, single-dose, randomized clinical trial with infliximab (5mg/kg) versus placebo. Behavioral performance on an effort-based decision-making task, self-report questionnaires, and neural responses during event-related functional magnetic resonance imaging were assessed at baseline and 2 weeks following infusion. We found that relative to placebo, patients receiving infliximab were more willing to expend effort for rewards. Moreover, increase in effortful choices was associated with reduced TNF signaling as indexed by decreased soluble TNF receptor type 2 (sTNFR2). Changes in effort-based decision-making and sTNFR2 were also associated with changes in task-related activity in a network of brain areas, including dmPFC, ventral striatum, and putamen, as well as the functional connectivity between these regions. Changes in sTNFR2 also mediated the relationships between drug condition and behavioral and neuroimaging measures. Finally, changes in self-reported anhedonia symptoms and effort-discounting behavior were associated with greater responses of an independently validated whole-brain predictive model (aka "neural signature") sensitive to monetary rewards. Taken together, these data support the use of anti-inflammatory treatment to improve effort-based decision-making and associated brain circuitry in depressed patients with high inflammation.

Evaluating the Neural Underpinnings of Motivation for Walking Exercise

OBJECTIVE

Motivation is critically important for rehabilitation, exercise, and motor performance, but its neural basis is poorly understood. Recent correlational research suggests that the dorsomedial prefrontal cortex (dmPFC) may be involved in motivation for walking activity and/or descending motor output. This study experimentally evaluated brain activity changes in periods of additional motivation during walking exercise and tested how these brain activity changes relate to self-reported exercise motivation and walking speed.

METHODS

Adults without disability (N = 26; 65% women; 25 [standard deviation = 5] years old) performed a vigorous exercise experiment involving 20 trials of maximal speed overground walking. Half of the trials were randomized to include "extra-motivation" stimuli (lap timer, tracked best lap time, and verbal encouragement). Wearable near-infrared spectroscopy measured oxygenated hemoglobin responses from frontal lobe regions, including the dmPFC, primary sensorimotor, dorsolateral prefrontal, anterior prefrontal, supplementary motor, and dorsal premotor cortices.

RESULTS

Compared with standard trials, participants walked faster during extra-motivation trials (2.43 vs 2.67 m/s; P < .0001) and had higher oxygenated hemoglobin responses in all tested brain regions, including dmPFC (+842 vs +1694 μM; P < .0001). Greater dmPFC activity was correlated with more self-determined motivation for exercise between individuals (r = 0.55; P = .004) and faster walking speed between trials (r = 0.18; P = .0002). dmPFC was the only tested brain region that showed both of these associations.

CONCLUSION

Simple motivational stimuli during walking exercise seem to upregulate widespread brain regions. Results suggest that dmPFC may be a key brain region linking affective signaling to motor output.

IMPACT

These findings provide a potential biologic basis for the benefits of motivational stimuli, elicited with clinically feasible methods during walking exercise. Future clinical studies could build on this information to develop prognostic biomarkers and test novel brain stimulation targets for enhancing exercise motivation (eg, dmPFC).

Apathy scores in Parkinson's disease relate to EEG components in an incentivized motor task

Apathy is one of the most prevalent non-motor symptoms of Parkinson's disease and is characterized by decreased goal-directed behaviour due to a lack of motivation and/or impaired emotional reactivity. Despite its high prevalence, the neurophysiological mechanisms underlying apathy in Parkinson's disease, which may guide neuromodulation interventions, are poorly understood. Here, we investigated the neural oscillatory characteristics of apathy in Parkinson's disease using EEG data recorded during an incentivized motor task. Thirteen Parkinson's disease patients with apathy and 13 Parkinson's disease patients without apathy as well as 12 healthy controls were instructed to squeeze a hand grip device to earn a monetary reward proportional to the grip force they used. Event-related spectral perturbations during the presentation of a reward cue and squeezing were analysed using multiset canonical correlation analysis to detect different orthogonal components of temporally consistent event-related spectral perturbations across trials and participants. The first component, predominantly located over parietal regions, demonstrated suppression of low-beta (12-20 Hz) power (i.e. beta desynchronization) during reward cue presentation that was significantly smaller in Parkinson's disease patients with apathy compared with healthy controls. Unlike traditional event-related spectral perturbation analysis, the beta desynchronization in this component was significantly correlated with clinical apathy scores. Higher monetary rewards resulted in larger beta desynchronization in healthy controls but not Parkinson's disease patients. The second component contained gamma and theta frequencies and demonstrated exaggerated theta (4-8 Hz) power in Parkinson's disease patients with apathy during the reward cue and squeezing compared with healthy controls (HCs), and this was positively correlated with Montreal Cognitive Assessment scores. The third component, over central regions, demonstrated significantly different beta power across groups, with apathetic groups having the lowest beta power. Our results emphasize that altered low-beta and low-theta oscillations are critical for reward processing and motor planning in Parkinson's disease patients with apathy and these may provide a target for non-invasive neuromodulation.

Double dissociation of dopamine and subthalamic nucleus stimulation on effortful cost/benefit decision making

Deep brain stimulation (DBS) and dopaminergic therapy (DA) are common interventions for Parkinson's disease (PD). Both treatments typically improve patient outcomes, and both can have adverse side effects on decision making (e.g., impulsivity).1,2 Nevertheless, they are thought to act via different mechanisms within basal ganglia circuits.3 Here, we developed and formally evaluated their dissociable predictions within a single cost/benefit effort-based decision-making task. In the same patients, we manipulated DA medication status and subthalamic nucleus (STN) DBS status within and across sessions. Using a series of descriptive and computational modeling analyses of participant choices and their dynamics, we confirm a double dissociation: DA medication asymmetrically altered participants' sensitivities to benefits vs. effort costs of alternative choices (boosting the sensitivity to benefits while simultaneously lowering sensitivity to costs); whereas STN DBS lowered the decision threshold of such choices. To our knowledge, this is the first study to show, using a common modeling framework, a dissociation of DA and DBS within the same participants. As such, this work offers a comprehensive account for how different mechanisms impact decision making, and how impulsive behavior (present in DA-treated patients with PD and DBS patients) may emerge from separate physiological mechanisms.

Apathy and Motivation: Biological Basis and Drug Treatment

Apathy is a disabling syndrome associated with poor functional outcomes that is common across a broad range of neurological and psychiatric conditions. Currently, there are no established therapies specifically for the condition, and safe and effective treatments are urgently needed. Advances in the understanding of motivation and goal-directed behavior in humans and animals have shed light on the cognitive and neurobiological mechanisms contributing to apathy, providing an important foundation for the development of new treatments. Here, we review the cognitive components, neural circuitry, and pharmacology of apathy and motivation, highlighting converging evidence of shared transdiagnostic mechanisms. Though no pharmacological treatments have yet been licensed, we summarize trials of existing and novel compounds to date, identifying several promising candidates for clinical use and avenues of future drug development.

Effort Expenditure Increases Risk-Taking for Improbable Rewards

Previous studies have found that exerting effort can lead people to engage in risk-taking behaviors. While effort can be either cognitive or physical, risk-taking can take place in either a risky context with known outcome probabilities or an ambiguous context with unknown outcome probabilities. The goal of the current research is to investigate how effort type and decision context influence risk-taking after effort exertion. Across three experiments, we find evidence that investing effort increases risk-taking at a short timescale. Importantly, this effect is particularly noticeable when the chance of winning is low, rather than when it is uncertain. Furthermore, the increase in risk-taking happens regardless of whether the effort is cognitive or physical. These findings suggest the existence of a cost-invariant but decision context-variant mechanism for the risk-taking after-effect of effort expenditure, which helps to bring the negative emotions caused by effort exertion back to a state of emotional homeostasis.

Effort Foraging Task reveals positive correlation between individual differences in the cost of cognitive and physical effort in humans

Effort-based decisions, in which people weigh potential future rewards against effort costs required to achieve those rewards involve both cognitive and physical effort, though the mechanistic relationship between them is not yet understood. Here, we use an individual differences approach to isolate and measure the computational processes underlying effort-based decisions and test the association between cognitive and physical domains. Patch foraging is an ecologically valid reward rate maximization problem with well-developed theoretical tools. We developed the Effort Foraging Task, which embedded cognitive or physical effort into patch foraging, to quantify the cost of both cognitive and physical effort indirectly, by their effects on foraging choices. Participants chose between harvesting a depleting patch, or traveling to a new patch that was costly in time and effort. Participants' exit thresholds (reflecting the reward they expected to receive by harvesting when they chose to travel to a new patch) were sensitive to cognitive and physical effort demands, allowing us to quantify the perceived effort cost in monetary terms. The indirect sequential choice style revealed effort-seeking behavior in a minority of participants (preferring high over low effort) that has apparently been missed by many previous approaches. Individual differences in cognitive and physical effort costs were positively correlated, suggesting that these are perceived and processed in common. We used canonical correlation analysis to probe the relationship of task measures to self-reported affect and motivation, and found correlations of cognitive effort with anxiety, cognitive function, behavioral activation, and self-efficacy, but no similar correlations with physical effort.

Beta and theta oscillations track effort and previous reward in human basal ganglia and prefrontal cortex during decision making

Choosing whether to exert effort to obtain rewards is fundamental to human motivated behavior. However, the neural dynamics underlying the evaluation of reward and effort in humans is poorly understood. Here, we investigate this with chronic intracranial recordings from prefrontal cortex (PFC) and basal ganglia (BG; subthalamic nuclei and globus pallidus) in people with Parkinson's disease performing a decision-making task with offers that varied in levels of reward and physical effort required. This revealed dissociable neural signatures of reward and effort, with BG beta (12-20 Hz) oscillations tracking subjective effort on a single trial basis and PFC theta (4-7 Hz) signaling previous trial reward. Stimulation of PFC increased overall acceptance of offers in addition to increasing the impact of reward on choices. This work uncovers oscillatory mechanisms that guide fundamental decisions to exert effort for reward across BG and PFC, as well as supporting a causal role of PFC for such choices.

Dissociable neural after-effects of cognitive and physical effort expenditure during reward evaluation

The reward after-effect of effort expenditure refers to the phenomenon that previous effort investment changes the subjective value of rewards when obtained. However, the neural mechanisms underlying the after-effects of effort exertion are still not fully understood. We investigated the modulation of reward after-effects by effort type (cognitive vs. physical) through the lens of neural dynamics. Thirty-two participants performed a physically or cognitively demanding task during an effort phase and then played a simple gambling game during a subsequent reward phase to earn monetary rewards while their electroencephalogram (EEG) was recorded. We found that previous effort expenditure decreased electrocortical activity during feedback evaluation. Importantly, this effort effect occurred in a domain-general manner during the early stage (as indexed by the reward positivity) but in a domain-specific manner during the later and more elaborative stage (as indexed by the P3 and delta oscillation) of reward evaluation. Additionally, effort expenditure enhanced P3 sensitivity to feedback valence regardless of effort type. Our findings suggest that cognitive and physical effort, although bearing some surface resemblance to each other, may have dissociable neural influences on the reward after-effects.

Premovement activity in the mesocortical system links peak force but not initiation of force generation under incentive motivation

Motivation facilitates motor performance; however, the neural substrates of the psychological effects on motor performance remain unclear. We conducted a functional magnetic resonance imaging experiment while human subjects performed a ready-set-go task with monetary incentives. Although subjects were only motivated to respond quickly, increasing the incentives improved not only reaction time but also peak grip force. However, the trial-by-trial correlation between reaction time and peak grip force was weak. Extensive areas in the mesocortical system, including the ventral midbrain (VM) and cortical motor-related areas, exhibited motivation-dependent activity in the premovement "Ready" period when the anticipated monetary reward was displayed. This premovement activity in the mesocortical system correlated only with subsequent peak grip force, whereas the activity in motor-related areas alone was associated with subsequent reaction time and peak grip force. These findings suggest that the mesocortical system linking the VM and motor-related regions plays a role in controlling the peak of force generation indirectly associated with incentives but not the initiation of force generation.

Core Body Temperatures in Intermittent Sports: A Systematic Review

BACKGROUND

Hyperthermia (and associated health and performance implications) can be a significant problem for athletes and teams involved in intermittent sports. Quantifying the highest thermal strain (i.e. peak core body temperature [peak Tc]) from a range of intermittent sports would enhance our understanding of the thermal requirements of sport and assist in making informed decisions about training or match-day interventions to reduce thermally induced harm and/or performance decline.

OBJECTIVE

The objective of this systematic review was to synthesise and characterise the available thermal strain data collected in competition from intermittent sport athletes.

METHODS

A systematic literature search was performed on Web of Science, MEDLINE, and SPORTDiscus to identify studies up to 17 April 2023. Electronic databases were searched using a text mining method to provide a partially automated and systematic search strategy retrieving terms related to core body temperature measurement and intermittent sport. Records were eligible if they included core body temperature measurement during competition, without experimental intervention that may influence thermal strain (e.g. cooling), in healthy, adult, intermittent sport athletes at any level. Due to the lack of an available tool that specifically includes potential sources of bias for physiological responses in descriptive studies, a methodological evaluation checklist was developed and used to document important methodological considerations. Data were not meta-analysed given the methodological heterogeneity between studies and therefore were presented descriptively in tabular and graphical format.

RESULTS

A total of 34 studies were selected for review; 27 were observational, 5 were experimental (2 parallel group and 3 repeated measures randomised controlled trials), and 2 were quasi-experimental (1 parallel group and 1 repeated measures non-randomised controlled trial). Across all included studies, 386 participants (plus participant numbers not reported in two studies) were recruited after accounting for shared data between studies. A total of 4 studies (~ 12%) found no evidence of hyperthermia, 24 (~ 71%) found evidence of 'modest' hyperthermia (peak Tc between 38.5 and 39.5 °C), and 6 (~ 18%) found evidence of 'marked' hyperthermia (peak Tc of 39.5 °C or greater) during intermittent sports competition.

CONCLUSIONS

Practitioners and coaches supporting intermittent sport athletes are justified to seek interventions aimed at mitigating the high heat strain observed in competition. More research is required to determine the most effective interventions for this population that are practically viable in intermittent sports settings (often constrained by many competing demands). Greater statistical power and homogeneity among studies are required to quantify the independent effects of wet bulb globe temperature, competition duration, sport and level of competition on peak Tc, all of which are likely to be key modulators of the thermal strain experienced by competing athletes.

REGISTRATION

This systematic review was registered on the Open Science Framework ( https://osf.io/vfb4s ; https://doi.org/10.17605/OSF.IO/EZYFA , 4 January 2021).

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.

Amphetamines Improve the Motivation to Invest Effort in Attention-Deficit/Hyperactivity Disorder

Prevailing frameworks propose that a key feature of attention-deficit/hyperactivity disorder (ADHD) is lower motivation. An important component of motivation is the willingness to engage in cognitively or physically effortful behavior. However, the degree to which effort sensitivity is impaired in ADHD has rarely been tested, and the efficacy of stimulant medication in ameliorating any such impairments is unclear. Here, we tested 20 individuals with ADHD (11 males, 9 females) who were managed with amphetamine-based medication (dexamfetamine, lisdexamfetamine), and 24 controls (8 males, 16 females). Individuals with ADHD were tested over two counterbalanced sessions, ON and OFF their usual amphetamine-based medication. In each session, participants performed an effort-based decision-making task, in which they were required to choose how much cognitive or physical effort they were willing to engage in return for reward. Our results revealed three main findings. First, individuals with ADHD had lower motivation relative to controls to invest effort in both the cognitive and physical domains. Second, amphetamine increased motivation uniformly across both domains. Finally, the net effect of amphetamine treatment was to mostly restore motivation across both domains of effort relative to healthy controls. These data provide clear evidence for a heightened sensitivity to both cognitive and physical effort in ADHD, and reveal the efficacy of amphetamine-based drugs in restoring effort sensitivity to levels similar to controls. These findings confirm the existence of reduced motivational drive in ADHD, and more broadly provide direct causal evidence for a domain-general role of catecholamines in motivating effortful behavior.SIGNIFICANCE STATEMENT A core feature of attention-deficit/hyperactivity disorder (ADHD) is thought to be a heightened aversion to effort. Surprisingly, however, the degree to which effort sensitivity is impaired in ADHD has rarely been tested. More broadly, the relative efficacy of catecholamines in motivating the investment of cognitive and physical effort is unclear. We tested 20 individuals with ADHD ON and OFF amphetamines, and compared their behavior on an effort-based decision-making task to 24 controls. When tested OFF medication, the ADHD group was less cognitively and physically motivated than controls. However, amphetamines led to a comparable increase in motivation across both domains. This demonstrates the efficacy of catecholamines in facilitating domain-general effort, and highlights the broader potential of such drugs to treat disorders of motivation.

Dissociation of Cognitive Effort-Based Decision Making and Its Associations With Symptoms, Cognition, and Everyday Life Function Across Schizophrenia, Bipolar Disorder, and Depression

BACKGROUND

Anhedonia and amotivation are symptoms of many different mental health disorders that are frequently associated with functional disability, but it is not clear whether the same processes contribute to motivational impairments across disorders. This study focused on one possible factor, the willingness to exert cognitive effort, referred to as cognitive effort-cost decision making.

METHODS

We examined performance on the deck choice task as a measure of cognitive effort-cost decision making, in which people choose to complete an easy task for a small monetary reward or a harder task for larger rewards, in 5 groups: healthy control (n = 80), schizophrenia/schizoaffective disorder (n = 50), bipolar disorder with psychosis (n = 58), current major depression (n = 60), and past major depression (n = 51). We examined cognitive effort-cost decision making in relation to clinician and self-reported motivation symptoms, working memory and cognitive control performance, and life function measured by ecological momentary assessment and passive sensing.

RESULTS

We found a significant diagnostic group × reward interaction (F8,588 = 4.37, p < .001, ηp2 = 0.056). Compared with the healthy control group, the schizophrenia/schizoaffective and bipolar disorder groups, but not the current or past major depressive disorder groups, showed a reduced willingness to exert effort at the higher reward values. In the schizophrenia/schizoaffective and bipolar disorder groups, but not the major depressive disorder groups, reduced willingness to exert cognitive effort for higher rewards was associated with greater clinician-rated motivation impairments, worse working memory and cognitive control performance, and less engagement in goal-directed activities measured by ecological momentary assessment.

CONCLUSIONS

These findings suggest that the mechanisms contributing to motivational impairments differ among individuals with psychosis spectrum disorders versus depression.

Associations Between Cognitive and Physical Effort-Based Decision Making in People With Schizophrenia and Healthy Control Subjects

BACKGROUND

Effort can take a variety of forms including physical (e.g., button pressing) and cognitive (e.g., working memory tasks). Few studies have examined whether individual differences in willingness to expend effort are similar or different across modalities.

METHODS

We recruited 30 individuals with schizophrenia and 44 healthy control subjects to complete 2 effort-cost decision-making tasks: the Effort Expenditure for Rewards Task (physical effort) and the cognitive effort discounting task (cognitive effort).

RESULTS

Willingness to expend cognitive and physical effort was positively associated for both individuals with schizophrenia and control subjects. Further, we found that individual differences in motivation and pleasure dimension of negative symptoms modulated the association between physical and cognitive effort. Specifically, participants with lower motivation and pleasure scores, irrespective of group status, showed stronger associations between task measures of cognitive and physical effort-cost decision making.

CONCLUSIONS

These results suggest a generalized deficit across effort modalities in individuals with schizophrenia. Further, reductions in motivation and pleasure may impact effort-cost decision making in a domain-general manner.

Fatigue during acute systemic inflammation is associated with reduced mental effort expenditure while task accuracy is preserved

BACKGROUND

Earlier work within the physical domain showed that acute inflammation changes motivational prioritization and effort allocation rather than physical abilities. It is currently unclear whether a similar motivational framework accounts for the mental fatigue and cognitive symptoms of acute sickness. Accordingly, this study aimed to assess the relationship between fatigue, cytokines and mental effort-based decision making during acute systemic inflammation.

METHODS

Eighty-five participants (41 males; 18-30 years (M=23.0, SD=2.4)) performed a mental effort-based decision-making task before, 2 hours after, and 5 hours after intravenous administration of 1 ng/kg bacterial lipopolysaccharide (LPS) to induce systemic inflammation. Plasma concentrations of cytokines (interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)) and fatigue levels were assessed at similar timepoints. In the task, participants decided whether they wanted to perform (i.e., 'accepted') arithmetic calculations of varying difficulty (3 levels: easy, medium, hard) in order to obtain rewards (3 levels: 5, 6 or 7 points). Acceptance rates were analyzed using a binomial generalized estimated equation (GEE) approach with effort, reward and time as independent variables. Arithmetic performance was measured per effort level prior to the decisions and included as a covariate. Associations between acceptance rates, fatigue (self-reported) and cytokine concentrations levels were analyzed using partial correlation analyses.

RESULTS

Plasma cytokine concentrations and fatigue were increased at 2 hours post-LPS compared to baseline and 5 hours post-LPS administration. Acceptance rates decreased for medium, but not for easy or hard effort levels at 2 hours post-LPS versus baseline and 5 hours post-LPS administration, irrespective of reward level. This reduction in acceptance rates occurred despite improved accuracy on the arithmetic calculations itself. Reduced acceptance rates for medium effort were associated with increased fatigue, but not with increased cytokines.

CONCLUSION

Fatigue during acute systemic inflammation is associated with alterations in mental effort allocation, similarly as observed previously for physical effort-based choice. Specifically, willingness to exert mental effort depended on effort and not reward information, while task accuracy was preserved. These results extend the motivational account of inflammation to the mental domain and suggest that inflammation may not necessarily affect domain-specific mental abilities, but rather affects domain-general effort-allocation processes.

Measuring cognitive effort without difficulty

An important finding in the cognitive effort literature has been that sensitivity to the costs of effort varies between individuals, suggesting that some people find effort more aversive than others. It has been suggested this may explain individual differences in other aspects of cognition; in particular that greater effort sensitivity may underlie some of the symptoms of conditions such as depression and schizophrenia. In this paper, we highlight a major problem with existing measures of cognitive effort that hampers this line of research, specifically the confounding of effort and difficulty. This means that behaviour thought to reveal effort costs could equally be explained by cognitive capacity, which influences the frequency of success and thereby the chance of obtaining reward. To address this shortcoming, we introduce a new test, the Number Switching Task (NST), specially designed such that difficulty will be unaffected by the effort manipulation and can easily be standardised across participants. In a large, online sample, we show that these criteria are met successfully and reproduce classic effort discounting results with the NST. We also demonstrate the use of Bayesian modelling with this task, producing behavioural parameters which can be associated with other measures, and report a preliminary association with the Need for Cognition scale.

Semantic knowledge of social interactions is mediated by the hedonic evaluation system in the brain

Attaching semantic meaning to sensory information received from both inside and outside our bodies is a fundamental function of the human brain. The theory of Controlled Semantic Cognition (CSC) proposes that the formation of semantic knowledge relies on connections between spatially distributed modality-specific spoke-nodes, and a modality-general hub in the anterior temporal lobes (ATLs). This theory can also be applied to social semantic knowledge, though certain domain-specific spoke-nodes may make a disproportionate contribution to the understanding of social concepts. The ATLs have strong connections with spoke-node structures such as the subgenual ACC (sgACC) and the orbitofrontal cortex (OFC) that play an important role in predicting the hedonic value of stimuli. We hypothesized that in addition to the ATL semantic hub, a social semantic task would also require input from hedonic evaluation structures. We used voxel based morphometry (VBM) to examine structural brain-behavior relationships in 152 patients with neurodegeneration (Alzheimer's disease [N = 12], corticobasal syndrome (N = 18], progressive supranuclear palsy [N = 13], behavioral variant frontotemporal dementia [N = 56], and primary progressive aphasia (PPA) [N = 53]) using the Social Interaction Vocabulary Task (SIVT). This task measures the ability to correctly match a social term (e.g. "gossiping") with a visual depiction of that social interaction. As predicted, VBM showed that worse SIVT scores corresponded with volume loss in bilateral ATL semantic hub regions, but also in the sgACC, OFC, caudate and putamen (pFWE <0.05). These results support the CSC model of a hub-and-spoke organization of social semantic knowledge with the ATL as a domain-general semantic hub, and ventromedial and striatal structures as domain specific spoke-nodes. Importantly, these results suggest that correct comprehension of social semantic concepts requires emotional 'tagging' of a concept by the evaluation system, and that the social deficits observed in some neurodegenerative disease syndromes may be caused by the break-down of this mechanism.

Conscious cognitive effort in cognitive control

Cognitive effort is thought to be familiar in everyday life, ubiquitous across multiple variations of task and circumstance, and integral to cost/benefit computations that are themselves central to the proper functioning of cognitive control. In particular, cognitive effort is thought to be closely related to the assessment of cognitive control's costs. I argue here that the construct of cognitive effort, as it is deployed in cognitive psychology and neuroscience, is problematically unclear. The result is that talk of cognitive effort may paper over significant disagreement regarding the nature of cognitive effort, and its key functions for cognitive control. I highlight key points of disagreement, and several open questions regarding what causes cognitive effort, what cognitive effort represents, cognitive effort's relationship to action, and cognitive effort's relationship to consciousness. I also suggest that pluralism about cognitive effort-that cognitive effort may manifest as a range of intentional or non-intentional actions the function of which is to promote greater success at paradigmatic cognitive control tasks-may be a fruitful and irenic way to conceive of cognitive effort. Finally, I suggest that recent trends in work on cognitive control suggests that we might fruitfully conceive of cognitive effort as one key node in a complex network of mental value, and that studying this complex network may illuminate the nature of cognitive control, and the role of consciousness in cognitive control's proper functioning. This article is categorized under: Philosophy > Consciousness Philosophy > Psychological Capacities Neuroscience > Cognition.

Effort avoidance as a core mechanism of apathy in frontotemporal dementia

Apathy is a core symptom in patients with behavioural variant frontotemporal dementia (bvFTD). It is defined by the observable reduction in goal-directed behaviour, but the underlying mechanisms are poorly understood. According to decision theory, engagement in goal-directed behaviour depends on a cost-benefit optimization trading off the estimated effort (related to the behaviour) against the expected reward (related to the goal). In this framework, apathy would thus result from either a decreased appetence for reward, or from an increased aversion to effort. Here, we phenotyped the motivational state of 21 patients with bvFTD and 40 matched healthy controls using computational analyses of behavioural responses in a comprehensive series of behavioural tasks, involving both expression of preference (comparing reward value and effort cost) and optimization of performance (adjusting effort production to the reward at stake). The primary finding was an elevated aversion to effort, consistent across preference and performance tasks in patients with bvFTD compared to controls. Within the bvFTD group, effort avoidance was correlated to cortical atrophy in the dorsal anterior cingulate cortex and to apathy score measured on a clinical scale. Thus, our results highlight elevated effort aversion (not reduced reward appetence) as a core dysfunction that might generate apathy in patients with bvFTD. More broadly, they provide novel behavioural tests and computational tools to identify the dysfunctional mechanisms producing motivation deficits in patients with brain damage.

Fatigue and Human Performance: An Updated Framework

Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.

To engage or not engage: Early incentive motivation prevents symptoms of chronic post-stroke depression - A longitudinal study

BACKGROUND

Although post-stroke depression (PSD) is known to disrupt motor rehabilitation after stroke, PSD is often undertreated and its relationship with motor impairment remains poorly understood.

METHODS

In a longitudinal study design we investigated, which factors at the early post-acute stage may increase the risk for PSD symptoms. We were especially interested in whether interindividual differences in the motivational drive to engage in physically demanding tasks indicate PSD development in patients suffering from motor impairments. Accordingly, we used a monetary incentive grip force task where participants were asked to hold their grip force for high and low rewards at stake to maximize their monetary outcome. Individual grip force was normalized according to the maximal force prior to the experiment. Experimental data, depression, and motor impairment were assessed from 20 stroke patients (12 male; 7.7 ± 6.78 days post-stroke) with mild-to-moderate hand motor impairment and 24 age-matched healthy participants (12 male).

RESULTS

Both groups showed incentive motivation as indicated by stronger grip force for high versus low reward trials and the overall monetary outcome in the task. In stroke patients, severely impaired patients showed stronger incentive motivation, whereas early PSD symptoms were associated with reduced incentive motivation in the task. Larger lesions in corticostriatal tracts correlated with reduced incentive motivation. Importantly, chronic motivational deficits were preceded by initially reduced incentive motivation and larger corticostriatal lesions in the early stage post-stroke.

CONCLUSIONS

More severe motor impairment motivates reward-dependent motor engagement, whereas PSD and corticostriatal lesions potentially disturb incentive motivational behavior, thereby increasing the risk of chronic motivational PSD symptoms. Acute interventions should address motivational aspects of behavior to improve motor rehabilitation post-stroke.

The neural correlates of mental fatigue and reward processing: A task-based fMRI study

Increasing time spent on the task (i.e., the time-on-task (ToT) effect) often results in mental fatigue. Typical effects of ToT are decreasing levels of task-related motivation and the deterioration of cognitive performance. However, a massive body of research indicates that the detrimental effects can be reversed by extrinsic motivators, for example, providing rewards to fatigued participants. Although several attempts have been made to identify brain areas involved in mental fatigue and related reward processing, the neural correlates are still less understood. In this study, we used the psychomotor vigilance task to induce mental fatigue and blood oxygen-level-dependent functional magnetic resonance imaging to investigate the neural correlates of the ToT effect and the reward effect (i.e., providing extra monetary reward after fatigue induction) in a healthy young sample. Our results were interpreted in a recently proposed neurocognitive framework. The activation of the right middle frontal gyrus, right insula and right anterior cingulate gyrus decreased as fatigue emerged and the cognitive performance dropped. However, after providing an extra reward, the cognitive performance, as well as activation of these areas, increased. Moreover, the activation levels of all of the mentioned areas were negatively associated with reaction times. Our results confirm that the middle frontal gyrus, insula and anterior cingulate cortex play crucial roles in cost-benefit evaluations, a potential background mechanism underlying fatigue, as suggested by the neurocognitive framework.

Effort-based decision making in schizotypy and its relationship with amotivation and psychosocial functioning

INTRODUCTION

Suboptimal effort-based decision-making with reduced willingness to expend effort for high-probability/high-value reward is observed in schizophrenia patients and is related to diminished motivation, but is understudied in schizotypy. This study aimed to examine effort-allocation in schizotypy individuals and its association with amotivation and psychosocial functioning.

METHODS

We recruited 40 schizotypy individuals and 40 demographically-matched healthy controls, based on Schizotypal Personality Questionnaire-Brief (SPQ-B) score (top and bottom 10% SPQ-B scores, respectively), from 2400 young people aged 15-24 years participating a population-based mental health survey in Hong Kong and examined effort-allocation using the Effort Expenditure for Reward Task (EEfRT). Negative / amotivation symptoms and psychosocial functioning were assessed by the Brief Negative Symptom Scale (BNSS) and the Social Functioning and Occupational Assessment Scale (SOFAS), respectively. Schizotypy individuals were categorized into high-amotivation and low-amotivation groups based on a median-split of BNSS amotivation domain score.

RESULTS

Our results showed no main group effect (in either two or three-group comparison) on effort task performance. Three-group comparison analyses on selected EEfRT performance indices revealed that high-amotivation schizotypy individuals displayed significantly less increase in effortful options from low-value to high-value reward (reward-difference score) and from low-probability/low-value to high-probability/high-value reward (probability/reward-difference score) than low-amotivation individuals and controls. Correlation analyses demonstrated trend-wise significance between BNSS amotivation domain score and several EEfRT performance indices in schizotypy group. Schizotypy individuals with poorer psychosocial functioning tended to exhibit smaller probability/reward-difference score relative to other two groups.

DISCUSSION

Our findings indicate subtle effort-allocation abnormalities in schizotypy individuals with high levels of diminished motivation, and suggest the link between laboratory-based effort-cost measures and real-world functional outcome.

Physical Effort Exertion for Peer Feedback Reveals Evolving Social Motivations From Adolescence to Young Adulthood

Peer relationships and social belonging are particularly important during adolescence. Using a willingness-to-work paradigm to quantify incentive motivation, we examined whether evaluative information holds unique value for adolescents. Participants (N = 102; 12-23 years old) rated peers, predicted how peers rated them, and exerted physical effort to view each peer's rating. We measured grip force, speed, and opt-out behavior to examine the motivational value of peer feedback, relative to money in a control condition, and to assess how peer desirability and participants' expectations modulated motivated effort across age. Overall, when compared with adolescents, adults were relatively less motivated for feedback than money. Whereas adults exerted less force and speed for feedback when expecting rejection, adolescents exerted greater force and speed when expecting to be more strongly liked or disliked. These findings suggest that the transition into adulthood is accompanied by a self-protective focus, whereas adolescents are motivated to consume highly informative feedback, even if negative.

Brain stimulation over dorsomedial prefrontal cortex modulates effort-based decision making

Deciding whether to engage in strenuous mental activities requires trading-off the potential benefits against the costs of mental effort, but it is unknown which brain rhythms are causally involved in such cost-benefit calculations. We show that brain stimulation targeting midfrontal theta oscillations increases the engagement in goal-directed mental effort. Participants received transcranial alternating current stimulation over dorsomedial prefrontal cortex while deciding whether they are willing to perform a demanding working memory task for monetary rewards. Midfrontal theta tACS increased the willingness to exert mental effort for rewards while leaving working memory performance unchanged. Computational modelling using a hierarchical Bayesian drift diffusion model suggests that theta tACS shifts the starting bias before evidence accumulation towards high reward-high effort options without affecting the velocity of the evidence accumulation process. Our findings suggest that the motivation to engage in goal-directed mental effort can be increased via midfrontal tACS.

The Yale Food Addiction Scale 2.0 and the modified Yale Food Addiction Scale 2.0 in Taiwan: Factor structure and concurrent validity

INTRODUCTION

The most widely used instruments to assess food addiction - the Yale Food Addiction Scale 2.0 (YFAS 2.0) and its modified version (mYFAS 2.0) - have not been validated in a Taiwanese population. The present study compared the psychometric properties between the Taiwan versions of YFAS 2.0 and mYFAS 2.0 among university students.

METHODS

An online survey comprising the YFAS 2.0, mYFAS 2.0, Weight Self-Stigma Questionnaire (WSSQ) and International Physical Activity Questionnaire-Short Form (IPAQ-SF) were used to assess food addiction, self-stigma, and physical activity.

RESULTS

All participants (n = 687; mean age = 24.00 years [SD ± 4.48 years]; 407 females [59.2%]) completed the entire survey at baseline and then completed the YFAS 2.0 and mYFAS 2.0 again three months later. The results of confirmatory factor analysis (CFA) indicated that the YFAS 2.0 and mYFAS 2.0 both shared a similar single-factor solution. In addition, both the YFAS 2.0 and mYFAS 2.0 reported good internal consistency (Cronbach's α = 0.90 and 0.89), good test-retest reliability (ICC = 0.71 and 0.69), and good concurrent validity with the total scores being strongly associated with the WSSQ (r = 0.54 and 0.57; p < 0.01), and less strongly associated with BMI (r = 0.17 and 0.13; p < 0.01) and IPAQ-SF (r = 0.23 and 0.25; p < 0.01).

DISCUSSION

Based on the findings, the Taiwan versions of the YFAS 2.0 and mYFAS 2.0 appear to be valid and reliable instruments assessing food addiction.

Therapeutic Application of Virtual Reality in the Rehabilitation of Mild Cognitive Impairment: A Systematic Review and Meta-Analysis

This review aimed to quantify the effect of therapeutic application of virtual reality (VR) on cognitive function in individuals with mild cognitive impairment (MCI). We searched for randomized controlled trials involving VR in the interventions provided to individuals with MCI. After searching four international electronic databases, we analyzed six studies involving 279 individuals with MCI. RevMan 5.4 was used for quality assessment and quantitative analysis. Therapeutic application of VR in individuals with MCI resulted in a significant improvement in cognitive function (mean difference = -1.46; 95% confidence interval: -2.53 to -0.39; heterogeneity: χ² = 970.56, df = 18, I² = 98%; and overall effect: Z = 2.67, p = 0.008). However, there was no significant improvement in the subcategories such as global cognition, working memory, executive function, memory function, and attention. In conclusion, feedback stimulation through VR has a potential value in improving cognitive function in individuals with MCI. However, on the basis of the results of the subcategories, a personalized VR program is required for the individual subcategories of cognitive function.

Glutathione in the nucleus accumbens regulates motivation to exert reward-incentivized effort

Emerging evidence is implicating mitochondrial function and metabolism in the nucleus accumbens in motivated performance. However, the brain is vulnerable to excessive oxidative insults resulting from neurometabolic processes, and whether antioxidant levels in the nucleus accumbens contribute to motivated performance is not known. Here, we identify a critical role for glutathione (GSH), the most important endogenous antioxidant in the brain, in motivation. Using proton magnetic resonance spectroscopy at ultra-high field in both male humans and rodent populations, we establish that higher accumbal GSH levels are highly predictive of better, and particularly, steady performance over time in effort-related tasks. Causality was established in in vivo experiments in rats that, first, showed that downregulating GSH levels through micro-injections of the GSH synthesis inhibitor buthionine sulfoximine in the nucleus accumbens impaired effort-based reward-incentivized performance. In addition, systemic treatment with the GSH precursor N-acetyl-cysteine increased accumbal GSH levels in rats and led to improved performance, potentially mediated by a cell-type-specific shift in glutamatergic inputs to accumbal medium spiny neurons. Our data indicate a close association between accumbal GSH levels and an individual’s capacity to exert reward-incentivized effort over time. They also suggest that improvement of accumbal antioxidant function may be a feasible approach to boost motivation.

Elevated Effort Cost Identified by Computational Modeling as a Distinctive Feature Explaining Multiple Behaviors in Patients With Depression

BACKGROUND

Motivational deficit is a core clinical manifestation of depression and a strong predictor of treatment failure. However, the underlying mechanisms, which cannot be accessed through conventional questionnaire-based scoring, remain largely unknown. According to decision theory, apathy could result either from biased subjective estimates (of action costs or outcomes) or from dysfunctional processes (in making decisions or allocating resources).

METHODS

Here, we combined a series of behavioral tasks with computational modeling to elucidate the motivational deficits of 35 patients with unipolar or bipolar depression under various treatments compared with 35 matched healthy control subjects.

RESULTS

The most striking feature, which was observed independent of medication across preference tasks (likeability ratings and binary decisions), performance tasks (physical and mental effort exertion), and instrumental learning tasks (updating choices to maximize outcomes), was an elevated sensitivity to effort cost. By contrast, sensitivity to action outcomes (reward and punishment) and task-specific processes were relatively spared.

CONCLUSIONS

These results highlight effort cost as a critical dimension that might explain multiple behavioral changes in patients with depression. More generally, they validate a test battery for computational phenotyping of motivational states, which could orientate toward specific medication or rehabilitation therapy, and thereby help pave the way for more personalized medicine in psychiatry.

Neural and Cognitive Signatures of Guilt Predict Hypocritical Blame

A common form of moral hypocrisy occurs when people blame others for moral violations that they themselves commit. It is assumed that hypocritical blamers act in this manner to falsely signal that they hold moral standards that they do not really accept. We tested this assumption by investigating the neurocognitive processes of hypocritical blamers during moral decision-making. Participants (62 adult UK residents; 27 males) underwent functional MRI scanning while deciding whether to profit by inflicting pain on others and then judged the blameworthiness of others' identical decisions. Observers (188 adult U.S. residents; 125 males) judged participants who blamed others for making the same harmful choice to be hypocritical, immoral, and untrustworthy. However, analyzing hypocritical blamers' behaviors and neural responses shows that hypocritical blame was positively correlated with conflicted feelings, neural responses to moral standards, and guilt-related neural responses. These findings demonstrate that hypocritical blamers may hold the moral standards that they apply to others.

Sign-tracking modulates reward-related neural activation to reward cues, but not reward feedback

Research shows cognitive and neurobiological overlap between sign-tracking [value-modulated attentional capture (VMAC) by response-irrelevant, discrete cues] and maladaptive behaviour (e.g. substance abuse). We investigated the neural correlates of sign-tracking in 20 adults using an additional singleton task (AST) and functional magnetic resonance imaging (fMRI). Participants responded to a target to win monetary reward, the amount of which was signalled by singleton type (reward cue: high value vs. low value). Singleton responses resulted in monetary deductions. Sign-tracking-greater distraction by high-value vs. low-value singletons (H > L)-was observed, with high-value singletons producing slower responses to the target than low-value singletons. Controlling for age and sex, analyses revealed no differential brain activity across H > L singletons. Including sign-tracking as a regressor of interest revealed increased activity (H > L singletons) in cortico-subcortical loops, regions associated with Pavlovian conditioning, reward processing, attention shifts and relative value coding. Further analyses investigated responses to reward feedback (H > L). Controlling for age and sex, increased activity (H > L reward feedback) was found in regions associated with reward anticipation, attentional control, success monitoring and emotion regulation. Including sign-tracking as a regressor of interest revealed increased activity in the temporal pole, a region related to value discrimination. Results suggest sign-tracking is associated with activation of the 'attention and salience network' in response to reward cues but not reward feedback, suggesting parcellation between the two at the level of the brain. Results add to the literature showing considerable overlap in neural systems implicated in reward processing, learning, habit formation, emotion regulation and substance craving.