Early-life vocalizations and adult auditory brainstem responses in California mice (Peromyscus californicus)

Mammalian infants rely on vocalizations to elicit care from their parents. In adult females, behavioral and neural responses to infant cries may change during the onset of motherhood; however, parenthood-associated plasticity in auditory processing is not well understood, especially in fathers. We characterized pup vocalizations from postnatal day (PND) 1 to PND 21 in biparental California mice (Peromyscus californicus) and assessed auditory brainstem responses to pure tones in adult virgins and parents of both sexes to test the hypothesis that auditory processing changes with the onset of parenthood, particularly in response to pup-relevant sound frequencies. Pups' call rate dropped sharply after PND 13, and pups from smaller litters vocalized more than pups from larger litters. Syllable duration was significantly shorter at PND 16-21 than all other ages. Overall, the minimum frequency of vocalizations and minimum, fundamental, and harmonic frequency power increased with age. Minimum frequency was highest after PND 10, and power for all frequencies peaked at PND 13-15. Hearing thresholds for 24 kHz stimuli were lower in parents than in virgins regardless of sex, and thresholds for 4 kHz were lower in females than in males. Auditory nerve response latencies were shorter in parents than in virgins at 4 kHz and shorter in females than in males at 8 kHz. In sum, our findings provide a spectral breakdown of early-life vocalizations and provide evidence that auditory processing can be influenced by reproductive status in both males and females in a biparental species.