輕度認知障礙是一種從正常認知功能轉變為失智的過渡階段。認知包含多種面向，例如記憶、專注、視覺空間功能、精神運作速度、語言及執行功能。由於腦部組織貫注不足可能是認知功能障礙的危險因子。近紅外光譜儀屬於一種非侵入性的血液動力學監測系統，其優點在於可以讓受測者在動態活動下即時監控帶氧及去氧血紅素之濃度變化。本研究目的在於分析有無輕度認知障礙的受測者在大腦前額區與大腿股外側肌的組織氧合度之相關性，並探討體能活動介入之影響，期望能為病患提供更多相關資訊。此外，有證據顯示體能活動與減少認知功能下降有關，但目前對此之證據仍然不足。實驗將分為兩個部分，第一部分受測者將分為有無輕度認知障礙，第二部分受側者將會進行為期三個月的體能活動介入，所有受測者皆透過重複的等長膝關節伸展運動下量測大腦前額區與大腿股外側肌的血氧變化。藉由頻譜分析（Welch’s method）歸納出三個主要的低頻段，其中包含：內皮細胞相關的血管調控（0.005-0.02 Hz）、交感神經支配下的血管調控（0.02-0.06 Hz）與血管平滑肌內的肌源性反應（0.06-0.15 Hz）。研究結果顯示輕度認知功能障礙病患前額葉與下肢肌肉組織有較明顯的內皮細胞活化活動。此可能顯示輕度認知功能障礙患有較差的氧合表現，需透過代償性的血管調控維持前額與肌肉組織間氧氣的傳遞與利用。同時，我們發現在無輕度認知功能障礙的組別中前額葉與肌肉在NIRS的頻譜有著顯著的相關性，相反的，在輕度認知功能障礙的組別中則沒有顯著的相關性。另一方面，相對於體能活動介入前，受測者在體能活動介入後，前額葉與肌肉在NIRS的頻譜有著顯著的相關性。以上結果顯示輕度認知功能障礙似乎會降低中樞和週邊組織之間的組織氧合相關性，而體能活動的介入似乎可以改善中樞和週邊組織之間的組織氧合相關性。本研究與相關研究文獻的表明一致認為經由探討血液動力學的訊號內頻率組成成分的改變，可以一窺相關疾病的致病機制，並在臨床實驗結果上指出身體活動和認知能力下降之間的反比關係。

Mild cognitive impairment (MCI) is a transitional phase from normal cognitive function to dementia which influences many cognitive functions such as memory, attention, visuospatial skills, mental processing speed, language and executive function. Because cerebral hypo-perfusion is a risk factor for cognitive dysfunction, changes in tissue oxygenation may be involved in cognitive functions. Near-infrared spectroscopy (NIRS) has been developed as non-invasive method to monitor the concentration change of hemoglobin. However, there are insufficient data to show that the improvements in the cognitive function can be attributed to physical exercises. The purpose of this present study is to analyze the association of the tissue oxygenation between MCI and non-MCI groups and to investigate the effects of physical exercises. NIRS signals were obtained simultaneously from prefrontal cortex and vastus lateralis muscle for repeatedly isometric knee-extension measurement. Three dominant frequencies of low-frequency oscillations (LFOs) in NIRS signals related to endothelial activity (0.005-0.02 Hz), sympathetic innervation (0.02-0.06 Hz) and myogenic response (0.06-0.15 Hz) have been obtained from the Welch’s method. Our results suggested that the higher activity of endothelium might be related to compensate adequate oxygen for peripheral muscle and prefrontal cortex in MCI. Moreover, significant correlation between cerebral and muscle were found in the MCI groups, but not in the non-MCI groups from analysis of NIRS spectra. These results suggest that the impact of MCI seems to be detrimental for the interaction of tissue oxygenation between central and peripheral tissue. On the other hand, significant correlation between cerebral and muscle in subjects who had performed the exercise intervention were also found. These results suggest the improvements of cognitive function were attributed to physical exercises. Our study coincides with previous studies that changes in the spectral components of NIRS signal could provide some insights into pathogenic mechanisms of diseases. Our clinical evidences also indicated an inverse relationship between physical activity and cognitive decline.

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