短期壓力對於與作業轉換相關腦電波之影響

Abstract

在我們日常生活中無法避免面對壓力事件的發生，而在遭遇壓力情境時，認知能力的運作會受到影響。人類在日常生活中常有機會同時進行不同種類的作業，在這類情境下，需要時常針對當下作業而轉換相對應的任務規則。作業轉換能力被視為是工作記憶能力中的中央執行功能。由於在探討壓力所造成之腦電波變化的文獻中，對於作業轉換的腦電波活動如何受急性壓力影響，並未有太多資料；而了解此一問題，有助於釐清中央執行功能受壓力影響的腦部機制。因此，本論文的主要目的，即在於探討急性壓力之下進行作業轉換時的腦電波變化。

本研究受試者會依照其於判斷形狀或大小的作業轉換表現，而獲得不同額度的獎金；進行作業的同時，其腦電波亦被記錄，並以獨立成分分析的方法來找出訊號的來源。在我們的研究裡提出了行為與生理訊號的證據，證明了受試者因急性壓力的影響感受到壓力、並且作業表現變好。然而，唾液中的皮質醇濃度沒有因壓力的操弄而有顯著的改變；另外一方面，腦電波結果顯示急性壓力明顯地影響了腦電波θ、α與γ的頻譜能量，這些成份的位置主要在額葉與頂葉中間的皮質部位，在急性壓力的影響之下，我們觀察到額葉的θ波的能量會有顯著的減少，還有額葉的α波在決策前也會顯著增加，最後額葉與頂葉的γ波都會顯著地增強。由本研究的行為與腦電波資料推論，適當的壓力可能會使人類的注意力集中，來讓工作記憶運作更有效率；而工作記憶運作效率的改善，會進而促進作業轉換能力，因此使得壓力下作業轉換的表現變得更好。

It is inevitable to face a stressful event in daily life. One may switch task rules in switching by doing different tasks. Besides, task switching task is a common method to investigate executive functions such as working memory, attention, etc. This study intended to investigate of switching task on brain activities under acutely stressful circumstances. Surprisingly few studies have so far been made at this intention; but it was still remained unclear on this. All 17 participants were recruited from university students, which were paid for small compensations depend on individual performance. Only one participant excluded from this study due to abnormal huge noise recorded on electroencephalogram (EEG) data. Independent component analysis applied for source localization. There are behavioral and physiological evidences to indicate that acute stress makes the participants more tension to perform well. Under stressful situations, participants were performed quick response with stable and high accuracy. Nonetheless, unexpected results were discovered on salivary cortisol. On the other hand, EEG results reflected that acute stress was pronounced at frontal and parietal midline cortex, especially on theta, alpha, gamma bands. There were three important findings on stress effects as following: (1) Frontal midline theta power decreased at baseline stage. (2) Frontal midline alpha power enhanced a short period before decision making (3) Frontal and parietal gamma power increased at baseline stage. One possible explanation for current results may be that executive functions changed strategy such as pay more attention result in higher working memory capacity to enhance performance on task switching during stressful conditions.