Basolateral and central amygdala orchestrate how we learn whom to trust

Area of Science:

• Neuroscience
• Social Psychology
• Decision Making

Background:

• Trust and cooperation are fundamental to social interactions.
• Assessing trustworthiness is crucial for navigating social dynamics.
• Previous research has not fully elucidated the neural mechanisms underlying trust-based decision-making and learning.

Purpose of the Study:

• To investigate the neural correlates of learning to trust and differentiate trustworthiness in humans.
• To examine the roles of specific brain regions, including the amygdala and nucleus accumbens, in trust behavior.
• To bridge the gap between animal models and human neuroimaging studies of trust.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to scan 62 healthy volunteers.
• Participants engaged in a repeated trust game, interacting with both trustworthy and untrustworthy artificial players.
• Behavioral data on trust choices and learning success were collected alongside neural activity.

Main Results:

• The central amygdala was activated during trust behavior planning, while the basolateral amygdala was active during outcome evaluation.
• Both central and basolateral amygdala showed stronger activation for untrustworthy players, but only in participants who successfully learned to differentiate trustworthiness.
• The nucleus accumbens encoded trust reciprocation independently of learning success, suggesting a distinct role from trust learning.

Conclusions:

• Learning whom to trust is primarily orchestrated by the amygdala, not reward processing in the nucleus accumbens.
• Different amygdala subnuclei and connected areas guide the formation of subjective trustworthiness beliefs and subsequent trust choices.
• This study provides novel insights into the neural basis of social learning and decision-making regarding trust in humans.