失憶型輕度認知障礙族群之事件分割在記憶中的角色

Abstract

為了將日常生活中的連續活動視為離散的事件，人們需要將正在進行的經驗分成有意義的單元，這個過程稱為事件分割（event segmentation)，影響經驗如何被記憶和日後的回憶。失憶型輕度認知障礙（aMCI）患者以顯著的記憶功能下降為特徵，而 aMCI 患者在事件分割的表現仍未被充分了解。本研究旨在闡明健康老年人 （HOA）與 aMCI 在事件分割表現上的差異，以及事件邊界（boundary）對記憶表現的影響。結果表明，相較於 HOA 組別， aMCI 組別分割事件具異質性，頻率較低且後續的延遲細節記憶表現較差。在 HOA 組別中，適當的分割事件與較好的時序記憶相關。此外，HOA 組別在時序記憶和自由回憶方面的表現優於 aMCI組別。邊界效應（boundary effect）在兩組之間相似，顯示兩組記憶表現皆於非邊界物體優於邊界物體，且跨事件邊界的時序表現優於事件內的時序。此外，事件分割表現與左側內嗅皮層灰質厚度呈現正相關，與海馬體或海馬旁迴未有顯著相關，表明內嗅皮層在事件分割中的重要角色，事件分割表現的下降可能是記憶受損的早期指標。本研究強調正常老化和 aMCI 患者如何將日常經歷轉化為有意義的記憶歷程。

To perceive the continuous activity of everyday life as discrete events, individuals must divide ongoing experiences into significant temporal segments, a process known as event segmentation, which influences how experiences are remembered and later recalled. Amnestic mild cognitive impairment (aMCI) is characterized by significant memory deficits and how effectively aMCI patients segment ongoing events remains uncharacterized. This study aims to elucidate the differences in event segmentation performance between healthy older adults (HOA) and individuals with aMCI, as well as the effect of boundaries on memory performance. The results indicated that individuals with aMCI segmented events less frequently and in a more idiosyncratic manner compared to the HOA, which predicted inferior delayed detail memory performance. In the HOA group, an optimal level of moderately segmented events was associated with better temporal order memory. Moreover, the HOA group exhibited superior performance in temporal order memory and free recall compared to the aMCI group. The boundary effect was similar across both groups, showing that memory performance for non-boundary objects was better than for boundary objects, and performance was enhanced across event boundaries compared to within-event conditions. Notably, group-collapsed correlational analyses demonstrated that event segmentation performance was related to the gray matter thickness of the left entorhinal cortex, rather than the hippocampus or the parahippocampal cortex. These results revealed that the entorhinal cortex played a crucial role in event segmentation, and a decline in event segmentation performance may serve as an early indicator of memory impairments. The present study underscores how normal aging and individuals with aMCI transform everyday experiences into meaningful memory representations.