Affective processing in dysphoria: evidence from startle probe modulation of ERPs

Background: A core feature of depression is dysregulated affective disposition. Particularly, depression is thought to be characterized by reduced affective processing of emotional stimuli, both pleasant and unpleasant. Affective processing can be studied through startle-elicited event-related potentials (ERPs). Specifically, the N2 component reflects the early stages of stimulus identification and processing while the P3 portrays the later attention resources allocation to the stimulus. However, to date, startle-elicited ERPs have been rarely employed to explore depression and depression vulnerability. Aim of the study: The objective of the present study was to examine affective processing in individuals with dysphoria, a vulnerability condition to develop full-blown depression, through the analysis of startle-elicited ERP components N2 and P3, during the viewing of pleasant, neutral and, unpleasant emotional pictures. Materials and methods: 48 university students (46 females, 2 males) were divided into two groups, with and without dysphoria. Subsequently, both groups engaged in a passive viewing of emotional pictures (pleasant, neutral and, unpleasant) while a startle probe that was semi-randomly administered at 300, 1500, 3500, or 4500 ms after picture onset. The EEG data were recorded during the entire emotional picture viewing task. Results: The analysis revealed a significant Group x Condition effect (p = .040). Particularly, individuals without dysphoria had a significantly smaller N2 amplitude to the startle probe in the pleasant condition, compared to the neutral one (p = .008). No such effect was found in the group with dysphoria (p = 1.000). Additionally, the results showed only a Condition effect of the P3, whereby greater P3 amplitude to the startle probe in the unpleasant condition relative to the neutral one (p = .040) across all participants emerged. Conclusions: The findings on the N2 amplitude suggest that in controls, but not in dysphoria, the pleasant context inhibited the early auditory processing of the startle probe, indicating that higher early attentional resources were allocated to the pleasant content rather than the probe. Hence, the present study further supports the hypothesis of blunted affective processing of pleasant emotional stimuli in individuals with depressive symptoms and at higher risk to develop full-blown depression.