前額葉皮質參與親社會行為中「自我」與「他人」相關之處理的年齡差異

Abstract

Greater prosocial behavior in older than younger adults, such as in financial donations, has been suggested to stem from increased empathy with age. We considered, however, that young and older prosocial decisions might also reflect motivations apart from empathy such as other more self-oriented reasons. In this present study, young and older adults underwent an fMRI experiment in which they apportioned real money to others during decision phases of hypothetical scenarios. Scenarios included opportunities to be prosocial, make typical purchases, or were neutral scenarios not typically requiring exchange of money. Participants’ decided amounts were then selectively adjusted in feedback on scenario outcomes and self-report on emotional reactions assessed. As expected, older adults apportioned more money than younger adults in prosocial scenarios. However, young adults reported greater magnitudes of emotional reactions than older adults. Age modulated scenario decision neural processing with a ventral to dorsal in the medial prefrontal cortex. These regions evinced lower neural activity to prosocial than purchase or neutral scenarios in older than younger adults, whereas younger adults were reversed. Critically, lower VMPFC activity was associated with more prosocial money apportioned and greater personal distress scores more in older adults, but with greater empathy concern more in younger adults. These findings suggest that young adults may not be less empathetic than older adults during financial prosocial decision. Moreover, other motivational psychological mechanisms might underlie older adult prosocial behaviors apart from general empathy.