Differential neural decoding of alarm and avoidance information from vocal alarm calls in humans.

Many animals and humans use scream calls to signal imminent threats, which typically evoke alarm and escape responses in recipients. Compared to animals, human scream calls are more diversified with varying levels of alarm signaling. Certain low-alarm human screams thus might not elicit full neural alarm cascades and threat avoidance actions. Here we investigated the neural circuits for decoding alarm and avoid-approach information from positive and negative scream calls in humans. Alarm and avoid-approach decisions showed minimal neural overlap, with alarm decisions recruiting neural cascades of sensory-affective decoding for action preparation, whereas avoid-approach judgments recruited neural systems for spatio-affective decoding for social decision-making. Furthermore, decision patterns revealed both an alarm quotient and an avoid quotient for risk arbitration, which linked the likelihood of an urgent response (alarm, avoid) to a slowing of choosing a potential safe option in response to scream calls. While the avoid quotient positively predicted neural activity in a broad cortico-limbic network, the alarm quotient predicted neural suppression with increasing alarm levels, especially in the amygdala as part of a presumed limbic alarm system. This points to a critical involvement of the amygdala at neural levels of choice arbitrations rather than in threat evaluations signaled by screams.