An auditory "low road" for threat processing in humans sensitive to fast temporal cues.

Rapid threat processing is a fundamental and evolutionarily conserved function of the brain. In vision, influential models of emotion propose the existence of a fast subcortical pathway for threat processing, connecting the visual thalamus with the amygdala, driven by coarse visual inputs. In audition, whether such a "shortcut" operates in humans has remained unknown. Here, using psychophysiology and neuroimaging, we provide convergent human evidence for an auditory pathway that is sensitive to fast temporal acoustic cues, previously linked to salient alarm signals and coarse auditory processing. Threatening sounds with fast temporal cues elicited rapid neural and autonomic responses at early post-stimulus latencies. Notably, right amygdala responses to these cues covaried with individual differences in strength of a direct auditory thalamo-amygdala pathway. Together, these findings identify a previously uncharacterized "low road" for auditory threat processing in humans, and establish fast temporal acoustic structure as a key feature supporting rapid affective responses.