Abstract
Using an improved Sternberg working memory paradigm and affective pictures of different valences, this study investigates the emotional experience capability of 22 first-onset and untreated major depressive disorder patients (MDD) compared with the matching 22 healthy control participants (HC) and whether there is a moodcongruent working memory effect. We employed a general linear model analysis of variance (ANOVA) with two-factor repeated measures analysis on the emotional experience capability (pupil diameter changes) and the working memory performance (accuracy). The results show that the pupil diameter changes of positive emotions are significantly greater in MDD than those in HC (p<0.001), and the pupil diameter changes of negative emotions are not significantly different between two groups (p=0.055), which suggest that MDD have a significantly decrease in the ability to experience pleasure (anhedonia). In addition, the results only present that the working memory performances of negative emotions are significantly greater in MDD than those of positive emotions (p<0.05), which indicates that there is a mood-congruent memory effect. Moreover, in MDD, a positive correlation is found between the pupil diameter changes and working memory performances of positive emotions, however there is no correlation between those of negative emotions. Taken together, these results suggest that MDD have a moodcongruent memory effect and anhedonia, and the mood-congruent memory effect may be due to the decreased memory performances of positive emotions (a decrease in the ability to experience pleasure), but not those of negative emotions increased. This study not only illustrates that the core symptoms of depressive patients may be a mood-congruent memory effect and anhedonia but also enriches the connotation of anhedonia as an endophenotype indicator.
Highlights
The working memory is a system that provides cognitive information processing with temporary information storage and limited processing; it is the cognitive basis for speech comprehension, learning, reasoning, and problem solving [1]
The emotional experience results showed that the depressive disorder group had a significantly lower emotional experience capability for positive emotions compared to the healthy control (HC) group, indicating that depressive patients had a significantly diminished ability to experience pleasure and present obvious symptoms of anhedonia
Based on a group of first-onset and untreated depressive patients and an HC group that had never suffered from any mental illnesses as participants, we investigated the major depressive disorder patients (MDD)’s working memory of different affective pictures and their emotional experience
Summary
The working memory is a system that provides cognitive information processing with temporary information storage and limited processing; it is the cognitive basis for speech comprehension, learning, reasoning, and problem solving [1]. Previous research has shown a significantly diminished working memory in untreated patients with major depressive disorder [2], which manifests in significantly diminished working memory accuracy and significantly extended reaction time [3]. Harvey et al used an n-back working memory paradigm to study verbal memory and found that the working memory capacity of patients with major depressive disorder was significantly impaired compared to a healthy control (HC) group, manifesting in significantly reduced accuracy and a significantly slower memory retrieval capability [5]. The working memory results of Rose and Ebmeier [6], who used a symbolic n-back experimental paradigm on patients with major depressive disorder, were consistent with the results of Harvey et al [5]. The verbal memory-based study by Fossati et al found that depressive patients had normal recognition and cued recall but impaired free recall [7]
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