Sound-evoked facial motion in ferrets: evidence for species differences in sensorimotor coupling

Abstract

Sensory stimuli elicit uninstructed movements in the mouse, and cortical activity covaries with these movements, raising the question of how much apparent sensory encoding reflects behaviorally driven signals. Still, whether sounds systematically elicit uninstructed movements in non-rodent species is an open question. Here we characterize sound-evoked facial motion and pupil dynamics in head-fixed ferrets, a carnivore species, passively exposed to broadband, natural, and synthetic auditory stimuli. Ferrets reliably produced facial responses to sounds, but unlike mice, these responses were dominated by a single onset-locked component scaling with sound loudness, tracked only temporal modulations below 2 Hz, and carried no information about sound identity or category. Paradoxically, synthetic sounds, which preserved spectrotemporal statistics but lacked higher-order natural structure, elicited stronger responses than their natural counterparts for several sound categories, suggesting that ferret behavioral responses reflect selective sensitivity to acoustic novelty rather than ecological salience. Pupil dynamics mirrored facial motion, consistent with a shared arousal mechanism. Together, these results show that sound-evoked facial motion in ferrets is less stimulus-specific than in mice, and suggest that the tight sensorimotor integration observed in rodents may reflect a species-specific organization rather than a general mammalian principle.