Neural correlates of effort-based valuation with prospective choices

Abstract

How is effort integrated in value-based decision-making? Animal models and human neuroimaging studies primarily linked the anterior cingulate cortex (ACC) and ventral striatum (VS) to the integration of effort in valuation. Other studies demonstrated the role of these regions in invigoration to effort demands, thus it is hard to separate the neural activity linked to anticipation and subjective valuation from actual performance. Here, we studied the neural basis of effort valuation separated from performance. We scanned forty participants with fMRI, while they were asked to accept or reject monetary gambles that could be resolved with future performance of a familiar grip force effort challenge or a fixed risk prospect. Participants' willingness to accept prospective gambles reflected discounting of values by physical effort and risk. Choice-locked neural activation in contralateral primary sensory cortex and ventromedial prefrontal cortex (vmPFC) tracked the magnitude of prospective effort the participants faced, independent of choice time and monetary stakes. Estimates of subjective value discounted by effort were found to be tracked by the activation of a network of regions common to valuation under risk and delay, including vmPFC, VS and sensorimotor cortex. Together, our findings show separate neural mechanisms underlying prospective effort and actual effort performance.

Keywords: Decision-making; Mixed-gambles; Physical effort; Prospection; Risk; fMRI.

Figure 1.

Summary of behavioral task: A) Effort level calibrated for each subject without incentive or feedback. B) Training phase tested performance at 5 calibrated levels of grip force with real-time effort feedback. After training phase, subjects rated subjective attractiveness of prospective effort mixed gambles. C) then prospective risk mixed gambles. D) before resolution of one randomly selected gamble from each session.

Figure 2.

Behavioral results: A) Increasing effort levels reduced performance success rate during training and confidence success rate during post-task survey. B) Group normalized median reaction times related to distance from indifference reflected in mean gamble acceptance rates in effort (red) and risk (blue) tasks. C,D) Heat maps depict preferences by level of prospective cost. For illustration, gain and loss were collapsed into 3 levels each. Error bars indicate S.E.M.

Figure 3.

Parametric activation and deactivation related to magnitude of prospective effort A, potential gain B, and loss C, in effort-based mixed gamble stimuli, and activation related to prospective risk D, and gain E, in risk-based mixed gamble stimuli. Statistical maps corrected for multiple comparisons using Gaussian Random Field Theory at whole-brain level p < 0.05.

Figure 4.

Parametric activation and deactivation related to estimates of subjective value from the effort A, and risk B tasks. Statistical maps corrected for multiple comparisons at whole-brain gaussian random field theory level p < 0.05.