Abstract
Although two previous studies have demonstrated that depressed individuals showed deficits in working memory (WM) updating of both negative and positive contents, the effects were confounded by shifting dysfunctions and the detailed neural mechanism associated with the failure in N-back task is not clear. Using a 2-back task, the current study examined the WM updating of positive, negative and neutral contents in depressed patients. It is found that depressed patients performed poorer than healthy controls only when updating positive material. Using event-related potential (ERP) technique, the current study also investigated the neural correlates of updating deficits in depression. According to previous studies, the n-back task was divided into three sub-processes, i.e., encoding, matching and maintaining. Our ERP results showed that depressed patients had smaller occipital P1 for positive material compared to healthy controls, indicating their insensitivity to positive items on early encoding stage. Besides, depressed patients had larger frontal P2 and parietal late positive potential (LPP) than healthy controls irrespective of the valence of the words, reflecting that patients are inefficient during matching (P2) and maintaining (LPP) processes. These two mechanisms (insufficient attention to positive stimuli and low efficiency in matching and maintaining) together lead to the deficits of WM updating in depression.
Highlights
It is well established that major depressive disorder (MDD) is associated with altered cognitive control which may contribute to symptoms such as anhedonia and maladaptive rumination (Marazziti et al, 2010; Rock et al, 2014)
Using an emotional 2-back task, the present study explored the deficits of working memory (WM) updating in MDD patients
Behavioral results showed a positive-specific deficit in the MDD group which is in line with the cognitive model of depression indicating that depression is associated with reduced response to positive stimuli (Disner et al, 2011)
Summary
It is well established that major depressive disorder (MDD) is associated with altered cognitive control which may contribute to symptoms such as anhedonia and maladaptive rumination (Marazziti et al, 2010; Rock et al, 2014). It has been proposed that impaired function of working memory (WM) is a hallmark of cognitive control deficits in depression (Austin et al, 2001; Joormann et al, 2011; Baddeley, 2013). It has been demonstrated that depressed individuals can hardly inhibit the interference of negative information. They fail to prevent irrelevant emotional information from entering WM, and have difficulties in removing task-irrelevant negative information from WM (Joormann, 2004, 2010; Goeleven et al, 2006; Foland-Ross et al, 2013). Excessive negative information is stored in their brain, contributing to uncontrollable and unintentional recurrence of negative thoughts and memories (Gotlib and Joormann, 2010; Joormann and Quinn, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
