What's the science?
What happens in the brain when we experience gratitude? Gratitude has previously been found to be associated with activity in the medial prefrontal cortex (mPFC) and perigenual anterior cingulate cortex (pACC), which are brain regions associated with value. In social interactions, how the giver perceives the cost of an action, and the receiver perceives the benefit, and how these two components are integrated in the brain, have not been studied in the context of gratitude. This week in Journal of Neuroscience, Yu and colleagues used functional magnetic resonance imaging (fMRI) to understand the experience of gratitude.
How did they do it?
The authors hypothesized that evaluation of cost and benefit would be related to activity in the mPFC (brain regions associated with valuation), and the experience of gratitude would be related to activity of the pACC. Thirty-one healthy young participants were included in data analysis. The authors first applied painful stimuli (electrical) and determined four pain levels calibrated to each individual. In the main experiment, during fMRI scanning, participants experienced many trials in which they were told they would receive a shock (at one of their four pain levels) unless their ‘partner’ in the experiment paid (at one of five payment levels, pre-determined per trial) to relieve their pain. The partner was actually a confederate, working with the experimenters.
What did they find?
The authors only analyzed trials in which the partner ‘helped’ the participant (by paying to reduce the participant’s pain). High cost (versus low cost) trials, where the partner paid more to help the participant, were associated with greater activation in the dorsomedial prefrontal cortex, right temporoparietal junction, and precuneus of the participant being helped. These regions are known to be involved in mentalizing and empathy. High benefit (partner pays to remove high pain) versus low benefit trials were associated with greater activity in regions associated with valuation; the ventromedial prefrontal cortex, and ventral and dorsal striatum. Gratitude was calculated using a formula that combined the cost and benefit for each trial together. Activity in the pgACC was found to track this measure of gratitude. pgACC activity also tracked how grateful participants reported feeling overall, at the end of the experiment. Finally, after measuring connectivity between the aforementioned brain regions, the authors found that a model in which ventral striatum and right temporoparietal junction influenced the pgACC was the best fit for the data. This suggests that gratitude is integrated in the pgACC.
What's the impact?
This is the first study to examine brain activity associated with gratitude using an index of gratitude on a trial-by-trial basis, and to consider how cost (to the helper) and benefit (to the receiver) are integrated into a perception of gratitude. The study found that cost was associated with brain regions involved in mentalizing, benefit was associated with brain regions involved in valuation, and gratitude was integrated in the pgACC. These findings help us to understand the representation of complex emotions like gratitude in the brain.
H. Yu et al., Decomposing gratitude: representation and integration of cognitive antecedents of gratitude in the brain. Journal of Neuroscience (2018). Access the original scientific publication here.