Alterations in amygdala function explain how aging and loneliness impair trust learning

Abstract Functional relationships are essential for healthy aging and they rely on social cognition skills such as establishing and monitoring whom to trust. However, aging and loneliness can negatively affect social brain function, potentially leading to a vicious cycle. Using functional MRI and computational modeling we investigated trust learning in a sample of neurotypical older (64-84 years, n=29f/23m) compared to younger adults (20-33 years, n=31f/31m). Older participants displayed lower initial trust and less trust learning when repeatedly interacting with a trustworthy and an untrustworthy trustee. Their basolateral and central amygdala activation was lower during trust decisions, and this was associated with less optimal trust behavior. Computational modeling also revealed that a crucial learning parameter, trust prediction error precision, was decoupled from basolateral amygdala activation, and this effect was pronounced in lonely older adults. These findings indicate that differences in amygdala function and reward signaling at older age and higher loneliness could drive detrimental effects on trust learning, leading to poorer social cognition and putting individuals’ sociality and well-being at risk.