EEG correlates of physical effort and reward processing during reinforcement learning

Area of Science:

• Neuroscience
• Cognitive Science
• Decision Making

Background:

• Effort-based decision making is typically modeled by subjective value, factoring in reward and effort.
• Understanding how physical effort impacts neural correlates of reward processing is crucial.

Purpose of the Study:

• To investigate if electroencephalography (EEG) event-related potential (ERP) correlates of reward processing are modulated by physical effort.
• To explore the neural mechanisms underlying effort-based decision making and reward valuation.

Main Methods:

• Participants performed a task requiring varying levels of quadriceps muscle activation (low vs. high effort) for rewards.
• Electromyography (EMG) recorded muscle activation; EEG captured event-related potentials (ERPs).
• Probabilistic contingencies determined effort levels, requiring adaptive learning and response switching.

Main Results:

• Feedback indicating effort level did not modulate the feedback-related negativity/reward positivity (FRN/RP).
• Neural responses to reinforcement outcomes were significantly increased by preceding physical effort.
• Source decomposition revealed effort-reward interactions primarily in later ERP components (P300-like positivity).

Conclusions:

• Retrospective physical effort modulates neural reward processing, particularly in later ERP components.
• This modulation may explain why rewards obtained through greater effort can act as more potent reinforcers.
• Effort itself is not perceived as punishment but influences subsequent reward processing and motivation.