The neurofunctional basis of affective startle modulation in humans – evidence from combined facial EMG-fMRI
AbstractThe startle reflex, a protective response elicited by an immediate, unexpected sensory event, ispotentiatedwhen evoked during threat andinhibitedduring safety. In contrast to skin conductance responses or pupil dilation, modulation of the startle reflex is valence-specific and consideredthecross-species translational tool for defensive responding.Rodent models implicate a modulatory pathway centering on the brainstem (i.e., nucleus reticularis pontis caudalis, PnC) and the centromedial amygdala (CeM) as key hubs for flexibly integrating valence information into differential startle magnitude.We employed innovative combined EMG-fMRI measurements in two independent experiments and samples and provide converging evidence for the involvement of these key regions in the modulatory acoustic startle reflex pathway in humans. Furthermore, we provide the crucial direct link between EMG startle eye-blink magnitude and neural response strength.We argue that startle-evoked amygdala responding and its affective modulation may hold promise as an important novel tool for affective neuroscience.