Neural mechanisms of emotion-modulated startle reflexes: insights from ERP and EEG oscillations

The startle reflex is an involuntary response to a sudden, highly intense stimulus. Previous research has primarily focused on the early stages of the startle reflex, specifically examining the impact of emotional pictures on early responses such as the Probe P3 component. However, it remains unclear whether emotions affect the later stages of startle reflex processing. Furthermore, the influence of emotions on neural oscillations, such as theta and alpha waves, has not been sufficiently studied in this context.

This study involved 27 participants (N = 27) and used emotional pictures (positive, negative, and neutral) together with a startle probe, combined with event-related potential (ERP) and event-related oscillation (ERO) analyses, to investigate the effects of emotions on both the early and later stages of the startle reflex.

The ERP results demonstrate that when applying the sudden sound stimuli, the negative picture condition evokes the smallest Probe P3 component and LPP, followed by the positive and neutral picture condition. More specifically, negative images reduced Probe P3 and LPP amplitudes compared with positive and neutral images, indicating sustained emotional modulation from early attentional to later processing stages. The ERO results show that early theta and alpha oscillations in the frontocentral region significantly differ between conditions, while the theta and alpha oscillations are largest when the sudden sound stimuli is applied in the negative picture condition, followed by the positive and neutral picture condition.

These findings demonstrate that emotions exert sustained modulatory effects on both early and later stages of startle reflex processing, as reflected in ERP components and oscillatory neural activity. Together, the ERP and ERO results provide converging evidence for the neural dynamics underlying emotion-modulated startle responses.