EEG Correlates of Affective Processing in Major Depressive Disorder

Background: Individuals with major depressive disorder present with deficits in emotional reactivity. Conflicting models have been proposed to characterise the direction of this effect. Previous studies mostly support the emotional context insensitivity model, which suggests that reactivity to positive and negatively-valenced emotional stimuli is blunted in depression. We sought to test the emotional context insensitivity hypothesis in a preregistered study. Methods: Forty-one depressed participants and 41 age- and gender-matched healthy controls were shown a series of unpleasant and neutrally-valenced pictures in a passive view paradigm while acquiring electroencephalography (EEG). The late positive potential (LPP), an EEG marker of emotional reactivity, was compared between groups using mixed-effects repeated-measures models and exploratory cluster-based permutation tests. Results: We found no difference in LPP amplitudes between MDD and healthy individuals using the preregistered analysis plan. However, exploratory permutation analysis revealed a significant reduction in the LPP for MDD participants while viewing unpleasant pictures in EEG electrodes marginally more posterior and within a narrower time interval than specified in our original analysis plan. Secondary analyses found that emotion regulation strategy use and anxiety comorbidity did not influence the LPP. Conclusions: We found significantly reduced LPP amplitudes to unpleasant pictures in MDD, in support of the emotional context insensitivity hypothesis. However, the parameters used to estimate the LPP deviated from the preregistered analysis plan, suggesting that methodological differences between studies may result in variability in the cortical response to emotional stimuli.