Substantial Heritability Underlies Fairness Norm Adaptation Capability and its Neural Basis

Area of Science:

• Neuroscience
• Behavioral Genetics
• Psychiatry

Background:

• Fairness norm adaptation is crucial for social cohesion.
• Understanding its genetic basis and neural mechanisms is key to mental health.
• Previous research has not fully elucidated the genetic links between norm adaptation, brain function, and mental health outcomes.

Purpose of the Study:

• To investigate the shared genetic underpinnings of fairness norm adaptation capability.
• To identify neural correlates of norm adaptation using fMRI.
• To examine the relationship between norm adaptation, its genetic basis, and long-term mental health, specifically depressive symptoms.

Main Methods:

• Recruited 186 twins for the Ultimatum Game (UG) with fMRI in early adulthood.
• Employed computational modeling to differentiate norm adaptation from fairness valuation in the UG.
• Assessed depressive symptoms eight years later and analyzed DRD2 polymorphisms and gene expression.

Main Results:

• Both norm adaptation and fairness valuation showed moderate heritability.
• The anterior insula and Supplementary Motor Area/Medial Frontal Gyrus (SMA/mSFG) were phenotypically correlated with norm adaptation.
• SMA/mSFG showed shared genetic influence with the learning rate (norm adaptation index), linked to DRD2 polymorphisms and dopamine gene expression.

Conclusions:

• Heritability significantly drives norm adaptation, facilitating social learning in dynamic environments.
• The learning rate predicts future depressive symptom severity, with shared genetic basis via DRD2 polymorphisms.
• Genetic contributions to norm adaptation play a role in preserving long-term mental health.