Acting upon threat: Electrocortical, autonomic, and oculomotor responses in anticipation of avoidable and inevitable threats.

Abstract

Attentive immobility is a defensive state that prepares organisms for adaptive responses to imminent threats. In humans, it has been associated with a multimodal pattern of heart rate bradycardia, elevated skin conductance, freezing of gaze, and reductions in visuocortical alpha power to enhance perceptual processing and action preparation. However, the extent to which these processes are shaped by threat intensity or rather reflect stereotypic response patterns remains elusive. Here we combined avoidable and inevitable threats with different shock intensities to dissociate threat intensity from action preparation in defensive responding. Forty-eight participants observed naturalistic images while electrocortical activity, heart rate, skin conductance, pupil dilation, and eye movements were recorded. The color and shape of the cue preceding each trial were indicative of the trial type and predicted an inevitable or avoidable high-intensity (painful) or low-intensity stimulation after the picture offset. Results showed stronger gaze centralization in avoidable trials, indicating enhanced action preparation. Skin conductance primarily reflected threat intensity, while heart rate, alpha power reduction, fixation durations, and pupil dilation varied with both threat intensity and action readiness. The interplay between these components suggests a need to move away from the notion of separate systems governing physiological and motor responses under threat. We argue for an integrative framework where defensive responses and motor preparation are driven by motivational relevance, which escalates with perceived imminence, harm potential, and escape possibility. These findings underscore the interconnected nature of affective and motor processes, offering new perspectives on human defensive behavior.