Ultrasonic vocalizations in mice and rats: New applications and recent developments from sender to receiver.

Mice and rats emit ultrasonic vocalizations (USV) above the human hearing range. Such USV are widely regarded as reliable indicators of the animal's affective state. Moreover, USV serve important communicative functions. Given their prominent role in social communication, this review adopts a reciprocal framework that considers both sender and receiver, with particular emphasis on both the production and perception of USV. The review focuses on sex differences and subtype variations in the sender, and explores the communicative value of USV through playback studies, revealing their role in regulating social interactions from the receiver's perspective. It also examines recent applications, including the use of isolation-induced USV during the homing test, USV as measures of expectation, and their relevance in modeling mania and emotional contagion. Furthermore, this review takes into account advancements in sender identification and live tracking in semi-natural environments, which have enhanced our understanding of USV. These insights offer valuable perspectives on rodent social communication and emotional processes, with implications for studying human disorders.