Neural and computational mechanisms of momentary fatigue and persistence in effort-based choice

Abstract

From a gym workout, to deciding whether to persevere at work, many activities require us to persist in deciding that rewards are ‘worth the effort’ even as we become fatigued. However, studies examining effort-based decisions typically assume that the willingness to work is static. Here, we use computational modelling on two effort-based tasks, one behavioural and one during fMRI. We show that two hidden states of fatigue fluctuate on a moment-to-moment basis on different timescales but both reduce the willingness to exert effort for reward. The value of one state increases after effort but is ‘recoverable’ by rests, whereas a second ‘unrecoverable’ state gradually increases with work. The BOLD response in separate medial and lateral frontal sub-regions covaried with these states when making effort-based decisions, while a distinct fronto-striatal system integrated fatigue with value. These results provide a computational framework for understanding the brain mechanisms of persistence and momentary fatigue.

Heightened effort discounting is a common feature of both apathy and fatigue

“…Historically, effort discounting has predominantly been used to study the neurobiology of apathy 1 , 25 – 29 . More recently, however, a nascent literature has begun to apply effort discounting paradigms to quantify fatigue 16 , 21 , 30 – 32 . Given the frequent co-existence of apathy and fatigue, this raises immediate concerns about interpreting effort discounting data in terms of each trait to the exclusion of the other.…”

Noradrenergic deficits contribute to apathy in Parkinson’s disease through the precision of expected outcomes

“…Following hierarchical models of predictive coding, one could decompose behaviour in our experiment into predictions at multiple levels of abstraction, from low-level proprioceptive predictions for movement to high-level multi-modal, domain-general beliefs [ 46 , 106 – 111 ]. Future work is needed to address how such a framework can accommodate the various stages of information processing that are thought to be involved in effort- and reward-based decision-making [ 112 – 114 ], including the weighting of action policies [ 13 , 15 , 53 ], initiating and sustaining an action [ 115 ], and evaluating and learning from the action outcomes.…”

Task-induced subjective fatigue and resting-state striatal connectivity following traumatic brain injury

“…Moreover, our finding of altered resting-state striatal connectivity, even after task performance, and its association with subjective fatigue, highlights regional specificity in explaining TBI-related fatigue, and further suggests that striatal connectivity might be used as a neuronal correlate of fatigue following TBI. The involvement of the ventral striatum in motivational processing ( Daniel and Pollmann, 2014 ) might contribute to evaluating if the effort needed to invest in a task is worth the outcome ( Vassena et al, 2014 ), taking into account current levels of fatigue ( Massar and Csathó, 2018 , Müller et al, 2021 ). In other words, alterations in striatal connectivity in people with TBI might thus indicate a difference in the integration of fatigue and behavioral outcome and thereby influence the motivation to exert effort.…”