Rodent ultrasonic vocal interaction resolved with millimeter precision using hybrid beamforming

Abstract

Ultrasonic vocalizations (USVs) fulfill an important role in communication and navigation in many species. Because of their social and affective significance, rodent USVs are increasingly used as a behavioral measure in neurodevelopmental and neurolinguistic research. Reliably attributing USVs to their emitter during close interactions has emerged as a difficult, key challenge. If addressed, all subsequent analyses gain substantial confidence. We present a hybrid ultrasonic tracking system, HyVL, that synergistically integrates a high-resolution acoustic camera with high-quality ultrasonic microphones. HyVL is the first to achieve millimeter precision (~3.4-4.8mm, 91% assigned) in localizing USVs, ~3x better than other systems, approaching the physical limits (mouse snout ~ 10mm). We analyze mouse courtship interactions and demonstrate that males and females vocalize in starkly different relative spatial positions, and that the fraction of female vocalizations has likely been overestimated previously due to imprecise localization. Further, we find that when two male mice interact with one female, one of the males takes a dominant role in the interaction both in terms of the vocalization rate and the location relative to the female. HyVL substantially improves the precision with which social communication between rodents can be studied. It is also affordable, open-source, easy to set up, can be integrated with existing setups, and reduces the required number of experiments and animals.

Mountable miniature microphones to identify and assign mouse ultrasonic vocalizations

“…Our findings are consistent with some found in array microphone systems [10,11,12], namely that female-assigned vocalizations often occur at very close range. As the largest proportion of unassigned USVs is in the similar close range, it is possible that some of them were produced by the females.…”

“…Males do demonstrate some flexibility in their vocal usage and repertoire depending on social context [8], and signatures of individual identity across different individuals [9], which suggests that USV production is a dynamic and complex social behavior. While much of the study of mouse ultrasonic vocal behavior is centered on male courtship song, females are also capable of producing USVs, both in male-female [10,11,12] and female-female interactions [13].…”

“…In order to study the complex behavioral interactions between two or more vocalizing animals, it is necessary to parse which vocal syllables are produced by which individual, which is impossible with a traditional recording setup, using a single overhead microphone (Fig 1a). USVs are produced at close range [11] and at high frequency [14]. Recently, to overcome this credit-assignment problem, several labs have developed array systems of microphones surrounding or above a recording arena [10,11,12].…”

“…USVs are produced at close range [11] and at high frequency [14]. Recently, to overcome this credit-assignment problem, several labs have developed array systems of microphones surrounding or above a recording arena [10,11,12]. Complex mathematical and computational tools are then used to sort out which vocalizations belong to whom.…”

A cooperatively breeding mouse shows flexible use of its vocal repertoire according to social context

“…Thus, all of our data reflect behaviour of dyads as opposed to specific individuals. But recent technical developments (69,70) may allow us to overcome this drawback in future studies of R. pumilio . Another recent development with this species is the assembly of a high-quality reference genome (71) of this wild mouse species.…”