Age-related and noise-induced hearing loss alters grasshopper mouse (Onychomys) vocalizations

California mice (Peromyscus californicus) adjust mouth movements for vocal production during early postnatal development

BACKGROUND

The order Rodentia is the largest group of mammals. Diversification of vocal communication has contributed to rodent radiation and allowed them to occupy diverse habitats and adopt different social systems. The mechanism by which efficient vocal sounds, which carry over surprisingly large distances, are generated is incompletely understood. Here we focused on the development and function of rhythmic mouth movements and laryngeal sound production. We studied spontaneously vocalizing California mice (Peromyscus californicus) through video and sound recordings. Mouth gape was estimated from video images and vocal characteristics were measured in synchronized sound recordings.

RESULTS

California mice coordinated their mouth movements with laryngeal sound production but differently in two call types. In high-frequency whistles ("USV syllables"), mouth movements were present on postnatal day 1 but were reduced within the first 2 weeks of life. Mouth movements were prominently present during sustained vocalizations ("SV syllables"), and movements became more and more adjusted to syllable beginning and end. Maximum mouth gape was correlated with sound intensity and fundamental frequency of SV syllables. The effect on sound intensity was the strongest during postnatal development and most predictable when the mouth was closed by temporarily immobilizing the mandible in an elevated position.

CONCLUSIONS

This study demonstrates that rhythmic orofacial behavior not only plays a critical role in determining acoustic features of the vocal behavior of California mice but also shows remarkable adjustments during early development.

Effects of Age on Responses of Principal Cells of the Mouse Anteroventral Cochlear Nucleus in Quiet and Noise

Older listeners often report difficulties understanding speech in noisy environments. It is important to identify where in the auditory pathway hearing-in-noise deficits arise to develop appropriate therapies. We tested how encoding of sounds is affected by masking noise at early stages of the auditory pathway by recording responses of principal cells in the anteroventral cochlear nucleus (AVCN) of aging CBA/CaJ and C57BL/6J mice in vivo. Previous work indicated that masking noise shifts the dynamic range of single auditory nerve fibers (ANFs), leading to elevated tone thresholds. We hypothesized that such threshold shifts could contribute to increased hearing-in-noise deficits with age if susceptibility to masking increased in AVCN units. We tested this by recording the responses of AVCN principal neurons to tones in the presence and absence of masking noise. Surprisingly, we found that masker-induced threshold shifts decreased with age in primary-like units and did not change in choppers. In addition, spontaneous activity decreased in primary-like and chopper units of old mice, with no change in dynamic range or tuning precision. In C57 mice, which undergo early-onset hearing loss, units showed similar changes in threshold and spontaneous rate at younger ages, suggesting they were related to hearing loss and not simply aging. These findings suggest that sound information carried by AVCN principal cells remains largely unchanged with age. Therefore, hearing-in-noise deficits may result from other changes during aging, such as distorted across-channel input from the cochlea and changes in sound coding at later stages of the auditory pathway.

Variation in responses to conspecific and heterospecific advertisement vocalizations in sympatric grasshopper mice (Onychomys)

Advertisement vocalizations that function in mate acquisition and resource defense within species may also mediate behavioral interactions among species. While olfactory signals play an important role in mate choice and territoriality in rodents, less is known about the function of acoustic signals in influencing interspecific interactions. In this study, we used playback experiments in the laboratory to assess the function of long-distance vocalizations within and among three sympatric species of grasshopper mice. We found that, within each species, individuals of both sexes varied widely in spontaneous vocal behavior and response to playback. The largest species (Onychomys leucogaster) was most responsive to conspecifics, but smaller O. arenicola and O. torridus exhibited no clear pattern in their vocal behavior and were even responsive to the white noise controls. Our results indicate that grasshopper mice are broadly responsive to a range of sounds that resemble calls and that long-distance vocalizations function primarily as signals that facilitate localization for subsequent close-distance assessment by both sexes in various social contexts. Variation in vocal responses among species may depend on competitive dominance, degree of interaction, acoustic similarity, or behavioral changes resulting from captivity. Replicating playback experiments in the field will help validate whether the observed variation in the laboratory reflects ecologically relevant patterns in nature.

Correlation between clinical characteristics and tinnitus severity in tinnitus patients of different sexes: an analytic retrospective study

PURPOSE

This study aimed to explore whether sex is influences tinnitus severity and whether the risk factors for tinnitus severity are the same in tinnitus patients of different sexes.

METHODS

This was a retrospective study of data from 1427 patients complaining of tinnitus in a local hospital otolaryngology clinic from November 2019 to January 2022. All patients were interviewed and assessed by otoscopy, pure-tone audiometry, tinnitus handicap inventory (THI), visual analogue scale (VAS), and tinnitus refinement test.

RESULTS

THI values were higher in females than in males (P = 0.00). Types of tinnitus sounds (OR 0.667, P = 0.000) and degree of hearing loss (OR 1.318, P = 0.000) were risk factors for tinnitus severity in males. Types of tinnitus sounds (OR 0.789, P = 0.005), sensation level (OR 1.023, P = 0.037), tinnitus types (OR 1.163, P = 0.041), tinnitus location (OR 1.198, P = 0.026), and the degree of hearing loss (OR 1.303, P = 0.000) were risk factors for tinnitus severity in females. Sex was an influencing factor for tinnitus severity. There were different risk factors for the tinnitus severity in different sexes.

CONCLUSION

The risk factors for tinnitus severity differed according to sex in tinnitus patients, and the risk factors for tinnitus severity were greater in women than in men. These findings add to the literature on sex differences in tinnitus and suggest that medical and psychological screening of affected individuals and customized tinnitus treatment for each individual with tinnitus are needed.

TRIAL REGISTRATION NUMBER/DATE OF REGISTRATION

ChiCTR2200057958, 2022/3/24 (retrospectively registered trials).