Pre-attentive biases in the early cortical processing of looming sounds

Objects approaching in space pose a potential threat to one’s existence. As a possible warning and avoidance mechanism, listeners are particularly sensitive to sounds indicating looming auditory objects. To be effective, triggering this warning mechanism should not rely on the listener's attention. We tested this hypothesis and looked into the role of attention by recording electroencephalographic (EEG) activity during passive and active listening conditions. To rule out stimulus specificity as a potential confound, we simulated looming and receding sounds using two complementary types of distance cues previously shown to elicit biases in favor of looms. Behaviorally, we found looming biases in terms of higher drift rates in sensory evidence accumulation. Neurally, the biases manifested in terms of magnified scalp potentials in both passive and active listening conditions and appeared as early as 50 ms after the sound change. The activity within the primary auditory cortex (PAC), inferred based on individual brain anatomies and electrode positions, was biased most consistently in the right hemisphere. Together, our findings exhibit pre-attentive and cue-generic biases in the early cortical processing of looming sounds, further supporting the protective potential of the underlying perceptual and neural mechanism.