Deficits Of Emotional Processing In Patients With Major Depression

Depression is a kind of mood disorder which is commonly found.Emotion processing deficits are one of the main features of depression and universally acknowledged in the academic and clinical fields.There are plenty of theories and models describing the deficits of emotion processing in depression,such as Cognitive Model of Depression(CMD),Emotion Context Insensitivity(ECI)Theory,and Deficits in Cognitive Inhibition(DCI)Theory.These theories are well-supported by many empirical researches.However,there is a lack of electrophysiological evidence concerning the subliminal perception and working memory in current research field,and thus the time course of emotion processing deficits in depression is barely known.To answer these questions and to further our understandings about this deficit,we regarded the bottom-up subliminal perception and the top-down updating process in working memory as the entry point and investigated the emotion processing features and the relevant electrophysiological evidence in depression,using the combination of the behavioral and Event-Related Potentials(ERPs)techniques.The current study recruited the clinical patients with major depression and the same number of healthy controls with highly matching demographic characteristics.Experiment 1 is designed to examine the subliminal processing of emotional facial expressions in depressive patients by means of ERPs.The ERP responses to subliminally presented happy/neutral/sad faces were recorded in 26 medication-free patients and 26 healthy controls in a backward masking task.Experiment 2 is conducted to explore the updating process of emotional stimuli in the working memory system in depressive patients.We collected the ERP data from all participants to happy/neutral/sad personality adjectives in 25 medication-free patients and 25 healthy controls.Data from Experiment 1 suggested that negative processing bias exists on the unconscious level in individuals with MDD.The ERP measures indicated that the unconscious emotional processing in MDD patients has a time course of three-stage deflection.To be more specific,the three components of P1,N170 and P3 have unique patterns that could separately index the deficits on the stages of primary visual,configural,and elaborated semantic processing.Thus the result of this experiment supported the CMD model,rather than the ECI model.Data from Experiment 2 indicated that patients with depression showed anhedonia(P1)during the encoding period of working memory updating;patients also recruited more cognitive resources in two sub-processes of working memory(shift and replacement),indexed by larger P2 and late positive potential(LPP).Thus the result of this experiment supported the DCI theory.The results from our current study described above discover the multi-level deficits in emotion processing in depression.On the one hand,under the perspective of bottom-up subliminal perception,it manifests the constant focuses on the negative emotion and the discontinuous lack of focuses on the positive emotion.On the other hand,from the view of top-down working memory updating,it exhibits the attention inhibition dysfunction to irrelevant negative emotion and the lack of efficiency on the processes of replacement and shift in working memory.In general,the current study provides a new vision to the conflicting theories and may also help to develop neurobiological markers for differential diagnosis of patients' emotion processing impairments in subliminal perception and working memory.