the larynx has been implicated in the production of ultrasonic vocalizations. a constriction within a rat’s larynx is thought to be the source of their ultrasonic vocalizations. as well, brain areas such as the medulla oblongata, the cortex, the amygdala, and the dorsal hippocampus, among others, play a role in 22-khz calls specifically. many of these brain areas/structures have been implicated in studies involving fear and anxiety, and can be associated with a larger network which deals with aversive emotions.