憂鬱病譜中個體的作業記憶功能缺損：以情緒性語言與非語言刺激材料之N-Back作業表現為例

Abstract

回顧文獻發現，憂鬱個體的認知功能缺損，除了表現在認知建構上（如：態度或歸因等），尚涉及訊息處理速度、注意力、短期記憶、長期記憶、決策、及規劃等廣泛的訊息處理歷程，而造成廣泛性認知功能缺損的可能原因之一，即為憂鬱個體的作業記憶功能缺損或偏誤。現存文獻亦指出，影響作業記憶功能的調節變項包括研究樣本的特性及測量工具的特性，如：刺激材料的情緒性、作業費力的程度、刺激材料的語言或非語言屬性等。奠基於憂鬱病譜（depressive spectrum）及情緒一致記憶（mood-congruent memory）的概念，並同時兼顧對於作業記憶的調節變項，本研究之主要目的在於以實徵方式探討憂鬱病譜中個體，面對情緒性語言和非語言刺激之作業記憶功能表現，並驗證高憂鬱者可能的作業記憶功能缺損或偏誤，以及憂鬱程度與作業記憶負荷量和刺激材料情緒性之間的關聯性。本研究分為兩個子研究，研究一以憂鬱病譜中的大學生為樣本來源，依MINI確認診斷之有無，搭配BDI-II分數劃分為憂鬱組（n = 23）、情緒低落組（n = 25）、及控制組（n = 32），並控制其年齡、教育程度、語文智商、作業智商、及全量表智商等人口學變項與干擾變項。研究一為3 ×（3 × 3）的三因子混合設計，依序施測實驗一（語言刺激材料）和實驗二（非語言刺激材料）。組間獨變項為憂鬱程度（憂鬱組、情緒低落組、及控制組），組內獨變項為刺激材料情緒性（快樂、中性、及悲傷）與作業記憶負荷量（0-Back、1-Back、及2-Back），依變項為反應時間與正確率。研究二以臨床憂鬱患者為樣本（n = 18），並以MINI確認診斷，輔以BDI-II測量其憂鬱程度。研究設計為3（刺激材料情緒性）x 3（作業記憶負荷量）的二因子受試者內設計，組內獨變項及依變項皆與研究一相同。研究一的分析結果，不論實驗一（語言刺激材料）或實驗二（非語言刺激材料），以正確率為依變項時，作業記憶負荷量和刺激材料情緒性的主要效果顯著，且憂鬱程度與作業記憶負荷量的交互作用顯著；以反應時間為依變項時，作業記憶負荷量的主要效果顯著，且憂鬱程度與作業記憶負荷量的交互作用顯著。研究二的分析結果，不論實驗一（語言刺激材料）或實驗二（非語言刺激材料），以正確率或反應時間為依變項時，都只有作業記憶負荷量的主要效果顯著。綜合看來，不論以正確率或反應時間為依變項指標，作業記憶負荷量的主要效果皆顯著，故本研究採用N-Back作業確實能夠有效操弄作業記憶負荷量，且反應時間比正確率對於作業記憶負荷量的變化來得敏感。對於非臨床憂鬱個體而言，0-Back、1-Back、及2-Back的情況皆非十分費力的（effortful）作業，僅在語言的2-Back作業上，憂鬱組的反應時間顯著較長。對於臨床憂鬱症患者而言，0-Back和1-Back亦非十分費力的作業，但到了2-Back已開始感到費力。此現象符合Ellis和Ashbrook（1988）提出資源配置模式和認知干擾理論。本研究僅部份支持情緒一致記憶的效果，同時亦發現刺激材料的特性不同，可能導致不同的情緒不一致記憶效果。最後，探討本研究可能的貢獻與臨床應用，並提出研究可能的限制以及未來研究可以進行的方向。

It has been often noted in literature that depressive individuals may suffer from broad deficits/bias in several areas of cognitive functions, which may be possibly due to the dysfunctions of working memory. Incorporated the possible moderators of working memory dysfunctions and/or impairments with the conception of depressive spectrum and mood-congruent memory, the main purpose of the present study was to investigate the impairment/bias of working memory of individuals with depressive spectrum disorders using N-Back task with verbal and nonverbal emotion-valenced stimuli. Specifically, the present study examined: 1) the main effect of depression severity; and 2) the interaction effects between depression severity and working memory loadings as well as between depression severity and the valences of stimuli. The present study includes two sub-studies. Study-I recruited the students of the National Taiwan University as samples who were assigned to depressive group (n = 23), dysphoric group (n = 25), and normal control group (n = 32) based on the diagnosis of MINI and BDI-II scores. The demographic and other relevant variables such as age, education level, VIQ, PIQ, and FSIQ were controlled. The Study-I, with a 3 × (3 × 3) mixed design, consisted of N-Back experiment One (verbal version) and experiment Two (nonverbal version). In that, the within-group independent variables included valences of stimuli (positive, neutral, and negative) and working memory loadings (0-Back, 1-Back, and 2-Back). The dependent variables were accuracy and reaction time. Study-II recruited clinical depressive patients (n = 18) as samples. The Study-II, with a (3 × 3) within group design, consisted of N-Back experiment One (verbal version) and experiment Two (nonverbal version). The results of Study-I, both verbal or nonverbal experiments, while indexed by accuracy, showed the main effects of working memory loadings and valences of stimuli, the interaction effects of working memory loadings with valences of stimuli and with depression severity. While indexed by reaction time, the results of Study-I revealed the main effect of working memory loadings and the interaction effects of working memory loadings with valences of stimuli and with depression severity. Differently, the results of Study-II showed the only main effect of working memory loadings in response to verbal or nonverbal stimuli. The discussion of the present study, whether the dependent variables were accuracy or reaction time, there were significant main effects of working memory loadings, indicating of successful manipulation of the N-Back task for loading of working memory. For clinical patients, neither 0-Back nor 1-Back was effortful-enough task; however, 2-Back appeared to be an effortful-enough task. The present study partly supported the mood-congruent memory, but there were opposite trends about sad and happy stimuli in verbal and nonverbal experiments. Finally, we discussed the contributions and clinical applications of the present study, addressed the possible limitations, and provided some approaches to carry on further researches.