Aversive (22 kHz) ultrasonic vocalization playback as translational assay of anxiety in rats: Evidence from both neural and behavioral studies

Affective disorders in humans such as anxiety are difficult to study in animal models. There is potential for development of a translational assay to study negative affect through playback of negatively valanced 22 kHz ultrasonic vocalizations which serve as alarm calls in rats. Many studies with varying USV playback parameters show anxiety like behaviors in response to playback in assays including observation in a cage, the 8-arm radial maze, place preference tests, the open field, and among others. Some literature, however, disputes the use of 22 kHz USV playback to leverage innate fear and anxiety responses in rat subjects. Regardless, some studies have shown brain affective processing activity unique to 22 kHz USV playback and lesion experiments suggest that altered functionality of emotional circuitry corresponds to differential behavioral output in response to playback. Though other literature points to the presence of sex differences, little to no research with 22 kHz USV playback has examined affective processing in male and female subjects. This method shows promise in producing analogous affective states to human anxiety, however many gaps within the field remain.