失憶型輕度認知功能障礙（a-MCI）患者被認為是演變成為阿茲海默症的高危險群，在早期由於海馬迴結構的神經纖維糾結，患者會開始產生記憶障礙。Braak和Braak在1991年將神經纖維糾結分成六個時期，開始會先從海馬迴結構的前內鼻區和側海馬迴產生病變，最後才會順延到海馬迴本體。由於前內鼻區主要處理事件及物件特徵，側海馬迴主要處理空間背景訊息，海馬迴本體主要處理空間位置記憶，所以本研究假設事件及物件特徵與空間背景訊息的配對記憶在a-MCI階段就會產生障礙，而空間位置記憶則在輕度阿茲海默症會開始產生障礙，如果不同階段神經病變的認知功能表現，可以在研究結果中呈現出來，或許可以協助找到早期偵測海馬迴結構病變的神經認知功能指標。 本研究受試者主要包含正常組（NC組）30人，失憶型輕度認知功能障礙組（a-MCI組）30人和輕度阿茲海默症組（AD組）30人，共計90人。每組受試者均接受神經心理測驗衡鑑和本研究自行發展的空間脈絡記憶測驗。空間脈絡記憶測驗總共分為三個部分：（1）空間位置記憶測驗：要求受試者回憶之前在地圖上隨機出現的建築物位置；（2）事件與地點連結測驗：事件和地點配對出現後，要求受試者選擇事件所配對的地點背景為何；（3）地點與物體的連結測驗：物體和地點配對出現後，要求受試者選擇該地點之前出現的物體為何。 研究結果呈現，不同組別在神經心理測驗結果，a-MCI組在延宕提取以及記憶保留的部分相較於其他認知功能顯著較差，而AD組相較於a-MCI組，除了記憶力表現更差外，其他認知功能的缺損也更為嚴重。而不同組別在空間脈絡記憶的結果，空間位置記憶分測驗呈現NC組＞a-MCI組＞AD組的結果，在事件與地點的連結分測驗呈現NC組＞a-MCI組＝AD組的結果，在地點與物體的連結分測驗呈現NC組＞a-MCI組＞AD組的結果。從ROC曲線分析呈現，空間脈絡記憶測驗相較於其他篩檢測驗，在區分NC組和a-MCI組的敏感度及特異度較好，而MMSE則在區分a-MCI組和AD組的敏感度及特異度較好。 研究結果呈現a-MCI受試者在一般認知功能尚未顯著下降的同時，空間脈絡記憶就已經呈現障礙，這可能和早期神經纖維糾結所破壞的區域有關，結果也呈現空間脈絡記憶測驗在a-MCI階段，比其他篩檢測驗能更敏感的區分出正常和異常的患者。目前臨床常用的MMSE測驗，因為複合了多項認知功能，反而適合用於篩檢已經為輕度阿茲海默症的患者。 / Background: Amnesic mild cognitive impairment (a-MCI) was identified to have a high risk to become Alzheimer’s disease (AD). In early stage of AD, because of neurofibrillary tangles, patient began complaining progressive memory deficits. The progressive course of neurofibrillary tangles was divided into 6 stages (Braak and Braak, 1991). Initially, the neurofibrillary tangles destroyed perirhinal and parahippocampus neurons, which may correspond to the a-MCI stage and then proceed to hippocampal body that correspond to early AD. According to previous studies, the perirhinal is primarily associated with item features encoding, the parahippocampus associated with scene features encoding, and the hippocampus associated with spatial location memory. Based on these findings, we hypothesized that the item and scene features association memory would show impairments in a-MCI and the spatial location memory would not be impaired in a-MCI but in early AD. If the different stages could be discriminated by the performance on spatial context memory test that we design, it can be utilized in clinical settings to assist the diagnosis of a-MCI. Method: Three groups of subjects were selected from the clinic of the neurological department of Chang Gung Memorial Hospital, including normal subjects (n=30), a-MCI subjects not diagnosed with dementia (n=30), and mild AD subjects (n=30). All of them were administered a package of neuropsychological tests and a self-developed spatial context memory test that include three sub-tests: (1) a spatial location memory test: subjects have to recognize the location of a building that was appeared in a map; (2) an event-place association memory test: subjects need point out which spatial scene that was associated with this event; and (3) a place-object association memory test: subjects need point out which object that was associated with this place shown before. Result: In neuropsychological tests, a-MCI group demonstrated significant impairment in delay retrieval and memory retention in comparison to their performance on tests for other cognitive functions. The AD group showed decline in overall cognitive functions including declarative memory and others. In the spatial context memory test, both the spatial location memory test and the place-object association memory subtest showed a decline in a-MCI group, and a further decline in AD group; the event-place association memory test presented significant decreases in both a-MCI and AD group in comparison to normal control, but no difference between the two clinical groups. Conclusion: The current study shows that the spatial context memory in a-MCI patients has greater impairment than their general cognitive function. Compared with other screening test, the spatial context memory has greater sensitivity and specificity to discriminate a-MCI from NC.