決策差異於錯誤預測跨年齡之調節

Abstract

在這個研究中，我們檢視年輕人與老年人在整合機率和回饋大小的決策風格之差異如何影響回饋學習過程中的神經錯誤預測。我們假設較年長的成人採用相對於年輕人而言較不複雜的決策策略，這樣的策略較無法有效的評估決策中的機率與回饋大小的資訊，因此在接收回饋時產生了錯誤預測的差異；再者，錯誤預測的神經反應無法區分採用相似決策策略的年輕人與老年人。我們利用磁震造影技術以及機率選擇作業收集年輕人與老年人的決策策略以及神經錯誤預測反應。研究結果顯示老年人在前額葉紋狀體區呈現減少的正向錯誤預測但較大的負向錯誤預測；此外，於年輕人雙側腦島中出現的對於負向回饋的反應，並未在老年樣本中觀察到。相對於老年人大部份的年輕人採用較為複雜的決策，採用相當於年輕人的決策策略的老年人則在前額葉紋狀體區產生相當於年輕人的錯誤預測反應；然而，決策並不影響年齡在腦島區的反應。這些研究結果顯示決策策略的偏好對於回饋處理中的神經錯誤預測影響多過於生物老化機制。選擇過程中的決策差異解釋了回饋處理過程中，前額葉紋狀體區的錯誤預測年齡差異上的縮減，但值得注意的是，年齡差異在腦島對於負向回饋的影響對於決策風格的調節較不敏感，顯示了生物老化在決策及回饋學習中的重要性。

In this present study, we examined how young and older adult differences in the complexity of strategy during value-based decisions involving integrating probability and magnitude contribute to age differences in neural prediction error responses for outcome learning. We hypothesized that more older adults adopt a less complex strategy than younger adults, with less effective weighting of probability or magnitude information for decisions, resulting in neural prediction error differences upon receiving feedback. Moreover, prediction error responses should not dissociate older from younger adults adopting similar strategies. We assessed complexity of decision strategy and prediction error responses in young and older adults using a lottery choice task in a functional magnetic resonance imaging (fMRI) experiment. Our results show that older adults had reduced gain prediction error (positive neural response) but greater loss prediction error (negative neural response) in fronto-striatal regions. In addition, whereas younger adult bilateral insula responded to losses, this was not observed in older adults. Further, a greater proportion of younger adults used more complex strategy than older adults. Older adults in the same strategy group as younger adults demonstrated comparable fronto-striatal prediction error responses. However, strategy did not influence age effects on insula responses. These findings suggest that decision strategy preference contributed more to fronto-striatal neural prediction error rather than biological age effects on feedback learning. Once strategy during choice is accounted for, age differences in fronto-striatal prediction error during feedback were eliminated. Notably, age differences in insula response to losses were insensitive to strategy suggesting a more prominent role of biological aging in this brain area for decision-making and feedback-learning.