Emotional Stimulus Processing in Depression: Insights from the Investigation of Symptom-Specific Alterations of the Late Positive Potential

Depression is associated with altered processing of emotional stimuli, often detected by changes in late positive potential (LPP) features. However, evidence on LPP amplitude and latency in individuals with depressive symptoms shows inconsistencies. These may stem from the heterogeneity inherent to depressive conditions, which were primarily investigated in terms of symptoms severity. Somatic and cognitive-affective symptoms, to our knowledge, have not been properly accounted for. 66 individuals with absent to severe depressive symptoms were presented with emotional pictures (pleasant, neutral, and unpleasant) while the electroencephalographic signal was recorded from a 32-channel cap. Linear mixed models were performed on LPP's mean amplitude and fractional peak latency adding fixed effects of emotional condition, severity of somatic and cognitive-affective depressive symptoms, and their interactions. Random effects included subject and channel factors. Our findings show a differential effect of somatic and cognitive-affective depressive symptoms on LPP amplitude and latency. Higher cognitive-affective symptoms were associated with reduced LPP amplitude for both pleasant (b = − .53, p < .001) and unpleasant (b = − .24, p = .007) pictures, while higher somatic symptoms were linked to an increased LPP amplitude for pleasant (b = .19, p = .030) and unpleasant (b = .31, p < .001) stimuli. Shorter LPP latencies were associated with higher somatic depressive symptoms, specifically for neutral pictures (b = -25.33, p = .007). These findings suggest a differential impact of somatic and cognitive depressive symptoms on central indices reflecting the elaboration of emotional stimuli. Therefore, we argue that a comprehensive understanding of the mechanisms governing emotional processing in depressive subjects should consider the specificity of individual symptoms.