腦白質結構上的老化關聯風險決策差異

Abstract

過去研究顯示額葉與紋狀體相關的腦區調控著風險決策行為，且老化會造成其連接的腦白質完整度下降，而我們對白質相關的老化結構改變對風險決策的影響仍不了解。本研究使用累進展望理論的架構，考慮人類決策時非理性的機率與價值偏好。我們收集 66 位年輕與 57 位老年臺灣樣本，在核磁共振造影中進行彩票選擇實驗。在行為上，我們以累進展望理論模型參數定義出風險趨避、損失趨避與機率權重參數，並比較以期望值基礎的決策閾值；在結構影像上，我們利用 T1 影像進行基於白質束之自動化分析，將擴散頻譜造影腦模版 NTU-122 上的 74 條白質束形變映射到受試者個人的擴散張量造影上，以計算非等向性指標。我們發現老化相關的機率權重敏感與連結腹側前額葉的胼胝體有關，並且，連結雙側眼窩部前額葉的額葉紋狀體白質束影響著老化相關的強趨避損失和高決策閾值，以及連結楔前葉的胼胝體亦與老化的損失趨避有關。

Previous studies show that fronto-striatal brain areas modulate risky decision making. Aging is associated with white matter architectural decline in these fronto-striatal areas. However, the effect of aging on decision processing is not yet clearly specified. In this study, we rely on the Cumulative Prospect Theory, which proposes irrational probability and value preference involved in risky decision making. In a magnetic resonance imaging study, 66 young and 57 older Taiwanese participants performed a lottery-choice decision task. Participants decided whether to accept or decline risky or safe choices. We extracted four indices of risky decision making from behavioral task performance: risk aversion, loss aversion, probability weighting sensitivity, and expected value based decision making threshold. T1-weighted and diffusion tensor images were also acquired. Tract-based automatic analysis with registration to the NTU-122 DSI template allowed us to estimate fractional anisotropy in 74 tracts in each individual brain. We find aging-related probability weighting sensitivity related to corpus callosum which connect dorsal-lateral-prefrontal cortex, and both side of fronto-striatal tracts linked to orbito-prefrontal cortex related to aging-related stronger averse to losing and higher threshold of decision, also corpus callosum which connect precuneus related to aging-related loss aversion.