健康老年的心智：認知神經科學的觀點

Insights into the Healthy Aging Mind: A Cognitive Neuroscience Perspective

認知老化的行為研究將衰退視為老年心智的表徵。然而，來自老化的認知神經科學研究卻有不同的觀點。在本篇文章中，我們回顧近20年來認知神經科學領域對於健康、正常老化歷程的實證研究，特別是應用非侵入性的腦造影工具，例如：功能性和解剖性磁共振造影，以及擴散磁振造影來探討老化大腦功能上與結構上的改變，以及這些變化如何影響認知行為。目前許多證據已經指出，雖然隨著年齡增加，大腦體積與皮質厚度會逐漸減少，大腦結構連結的完整性逐漸減損，神經回路的處理效率也逐漸降低，但是高齡者的大腦仍然能彈性運用既有的神經認知資源，來適應內外環境的變化和因應不同的認知挑戰，顯示出大腦動態的適應歷程。此外，我們簡介幾個當代提出的老化認知神經科學理論，也對這些理論提出我們的觀察和評論。最後，我們針對老化認知神經科學在台灣的研究方向，提出了幾項應該持續關注的研究議題。我們認為，老化認知神經科學研究的持續投入，能夠釐清正常老化的大腦神經機制，也協助描繪老年心智的完整圖像。

Age-related declines in behavior and cognition were reported as a dominant picture of the aging mind. Compelling evidence from the burgeoning field of cognitive neuroscience of aging, however, urges a reconsideration of this pessimistic view. In this article, we review the number of reports on the cognitive neuroscience of aging, focusing on a variety of neuroimaging technology, such as structural and functional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). In the face of the declines with age in brain structure volume, cortical thickness, and white matter integrity, functional neuroimaging studies have demonstrated increased neural activation in prefrontal and parietal regions across different cognitive domains in older adults. These results suggest that the aging brain retains considerable plasticity of function and is adaptive in response to cognitive challenges posed by structural deterioration. We review the converging evidence that is stimulating new hypotheses regarding the neural mechanisms underlying age-related changes in neurocognitive function. The current trends, unsolved issues and future directions in the cognitive neuroscience of aging are discussed.