Simultaneous recording of ultrasonic vocalizations and sniffing from socially interacting individual rats using a miniature microphone
Vocalizations are pivotal in mammalian communication, especially in humans. Rodents accordingly rely on ultrasonic vocalizations (USVs) that reflect their internal state as a primary channel during social interactions. However, attributing vocalizations to specific individuals remains challenging, impeding internal state assessment. Rats emit 50 kHz USVs to indicate positive states and intensify sniffing during alertness and social interactions. Here, we present a method involving a miniature microphone attached to the rat nasal cavity that allows to capture both male and female individual rat vocalizations and sniffing patterns during social interactions. We found that while the emission of 50 kHz USVs increases during close interactions, these signals lack specific behavioral associations. Moreover, a previously unreported low-frequency vocalization type marking rat social interactions was uncovered. Finally, different dynamics of sniffing and vocalization activities point to distinct underlying internal states. Thus, our method facilitates the exploration of internal states concurrent with social behaviors. MotivationHere, we sought to solve the problem of identifying the emitter of a specific vocalization during free social interaction of animal models. The use of a miniature microphone carried by the subject and connected to its nasal cavity solved this challenge and allowed for assignment of any vocalization recorded during a social interaction to a specific individual. Moreover, the miniature microphone enabled simultaneous recording of sniffing and vocalization activities of an individual, thus facilitating recognition of the internal states underlying these traits.