Communication plays an integral role in human social dynamics and is impaired in several neurodevelopmental disorders. Mice are used to study the neurobiology of social behavior; however, the extent to which mouse vocalizations influence social dynamics has remained elusive because it is difficult to identify the vocalizing animal among mice involved in a group interaction. By tracking the ultrasonic vocal behavior of individual mice and using an algorithm developed to group phonically similar signals, we show that distinct patterns of vocalization emerge as male mice perform specific social actions. Mice dominating other mice were more likely to emit different vocal signals than mice avoiding social interactions. Furthermore, we show that the patterns of vocal expression influence the behavior of the socially-engaged partner but no other animals in the cage. These findings clarify the function of mouse communication by revealing a communicative ultrasonic signaling repertoire.

These changes facilitated the acquisition of larger and more comprehensive data sets that better represent the vocal activity within an experiment. Furthermore, this system will allow more thorough analyses of the role that vocal signals play in social communication. We expect that such advances will broaden our understanding of social communication deficits in mouse models of neurological disorders.

Adult mice emit ultrasonic vocalizations (USVs), sounds above the range of human hearing, during social encounters. While mice alter their vocal emissions between isolated and social contexts, technological impediments have hampered our ability to assess how individual mice vocalize in group social settings. We overcame this challenge by implementing an 8-channel microphone array system, allowing us to determine which mouse emitted individual vocalizations across multiple social contexts. This technology, in conjunction with a new approach for extracting and categorizing a complex, full repertoire of vocalizations, facilitated our ability to directly compare how mice modulate their vocal emissions between isolated, dyadic and group social environments. When comparing vocal emission during isolated and social settings, we found that socializing male mice increase the proportion of vocalizations with turning points in frequency modulation and instantaneous jumps in frequency. Moreover, males change the types of vocalizations emitted between social and isolated contexts. In contrast, there was no difference in male vocal emission between dyadic and group social contexts. Female vocal emission, while predominantly absent in isolation, was also similar during dyadic and group interactions. In particular, there were no differences in the proportion of vocalizations with frequency jumps or turning points. Taken together, the findings lay the groundwork necessary for elucidating the stimuli underlying specific features of vocal emission in mice.

Cannabis and alcohol co-use is common, and the trend may increase further given the current popularity of cannabis legalization. However, the metabolic consequences of such co-use are unclear. Here, we investigated how co-administration of alcohol and ∆ 9 -tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, affects body weight and visceral adiposity, and glucose and insulin homeostasis in rats. For 16 consecutive days during adolescence, male rats drank saccharin or alcohol after receiving subcutaneous oil or THC injections in Experiment 1 and voluntarily consumed alcohol, THC edible, or both drugs in Experiment 2. Experiment 1 showed that following abstinence, drug co-exposure reduced visceral fat and the amount of insulin required to clear glucose during an oral glucose tolerance test (OGTT). In Experiment 2, rats received a high-fat diet (HFD) after 3-week abstinence. Although adolescent drug use did not interact with the HFD to worsen hyperglycemia and hyperinsulinemia during an OGTT, HFD-fed rats that co-used alcohol and THC had the lowest insulin levels 75 min after an insulin injection, suggesting an altered rate of insulin secretion and degradation. These results suggest that THC and alcohol co-exposure can distinctly alter the physiology of glucose and insulin homeostasis in a rodent model.

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