Effect of different phases of menstrual cycle on brainstem auditory evoked response

Expression profiling of cochlear genes uncovers sex-based cellular function in mouse cochleae

Sex is a pivotal biological factor that significantly impacts tissue homeostasis and disease susceptibility. In the auditory system, sex differences have been observed in cochlear physiology and responses to pathological conditions. However, the underlying molecular mechanisms responsible for these differences remain elusive. The current research explores the differences in gene expression profiles in the cochlea between male and female mice, aiming to understand the functional implication of sex-biased gene expression in each sex. Using RNA-sequencing analysis on cochlear tissues obtained from male and female mice, we identified a significant number of genes exhibiting sex-biased expression differences. While some of these differentially expressed genes are located on sex chromosomes, most are found on autosomal chromosomes. Further bioinformatic analysis revealed that these genes are involved in several key cellular functions. In males, these genes are notably linked to oxidative phosphorylation and RNA synthesis and processing, suggesting their involvement in mitochondrial energy production and regulatory control of gene expression. In contrast, sex-biased genes are associated with mechano-transduction and synaptic transmission within female cochleae. Collectively, our study provides valuable insights into the molecular differences between the sexes and emphasizes the need for future research to uncover their functional implications and relevance to auditory health and disease development.

Sex differences and the effect of female sex hormones on auditory function: a systematic review

Aims

First, to discuss sex differences in auditory function between women and men, and whether cyclic fluctuations in levels of female sex hormones (i.e., estradiol and progesterone) affect auditory function in pre-menopausal and post-menopausal women. Second, to systematically review the literature concerning the discussed patterns in order to give an overview of the methodologies used in research. Last, to identify the gap in knowledge and to make recommendations for future work.

Methods for the systematic review

Population, Exposure, Control, Outcome and Study design (PECOS) criteria were used in developing the review questions. The review protocol follows the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was pre-registered in the Prospective Register of Systematic Reviews (PROSPERO; CRD42020201480). Data Sources: EMBASE, PubMed, MEDLINE (Ovid), PsycINFO, ComDisDome, CINAHL, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL) via Cochrane Library, and scanning reference lists of relevant studies, and internet resources (i.e., Mendeley) were used. Only studies published between 1999 and 2022, in English, or in English translation, were included. The quality of evidence was assessed using the Newcastle-Ottawa Scale (NOS).

Results

Sex differences: Women had more sensitive hearing (measured at the level of peripheral and central auditory system) than men. Cyclic fluctuations: Auditory function in women fluctuated during the menstrual cycle, while no such fluctuations in men over the same time period were reported. Hearing sensitivity improved in women during the late follicular phase, and decrease during the luteal phase, implying an effect of female sex hormones, although the specific effects of estradiol and progesterone fluctuations on the central auditory system remain unclear. Hearing sensitivity in women declined rapidly at the onset of menopause.

Conclusion

The review has shown the following. Consistent sex differences exist in auditory function across the auditory pathway with pre-menopausal women often showing better function than age-matched men. Moreover, pre-menopausal women show fluctuations in hearing function across the menstrual cycle with a better function during the peak of estradiol or when the ratio of estradiol to progesterone is high. Third, menopause marks the onset of hearing loss in women, characterized by a rapid decline in hearing sensitivity and a more pronounced loss than in age-matched men. Finally, the systematic review highlights the need for well-designed and -controlled studies to evaluate the influence of estradiol and progesterone on hearing by consistently including control groups (e.g., age-matched man), using objective tests to measure hormonal levels (e.g., in saliva or blood), and by testing participants at different points across the menstrual cycle.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020201480, identifier CRD42020201480.

The effect of the menstrual cycle on dichotic listening

The purpose of this study was to determine the effect of the menstrual cycle on responses to a dichotic listening task. It was hypothesized that participants would exhibit a stronger right ear advantage during the menstrual cycle days when estrogen levels are at their peak. It was also hypothesized that the women not taking oral contraceptives would exhibit greater variations in ear advantage over the course of their menstrual cycle than those taking oral contraceptives. Finally, it was hypothesized that the error response rates would remain similar across different listening conditions and over the menstrual cycle. The participants were 30 women who took oral contraceptives and 15 who did not. They completed nine listening sessions comprised of three dichotic listening tasks: forced-left, forced-right, and open. The data were analyzed using a mixed effects models. The participants exhibited a reduction in right ear responses on the days that corresponded to when the level of estrogen would begin to increase. This response was different from what had been hypothesized. The analysis also indicated no response differences between the two groups of women. In addition, the women exhibited fewer errors over the course of the sessions, implying that they adapted to the task. The results indicate that the women’s hormone fluctuation across the menstrual cycle affected their responses to the forced-left, cognitive control, task only.

Central conduction time in auditory brainstem response and ear advantage in dichotic listening across menstrual cycle

The ovarian hormones fluctuate during the menstrual cycle in women. Such fluctuation of sex hormones, in particular estrogen, is believed to affect the central conduction time in auditory function as well as the language lateralization in cognitive function. However, findings are inconsistent. The underlying mechanisms are also unclear. This paper examined if there was any relation between the central conduction time and the language lateralization at different times during the menstrual cycle. Twenty young women with normal menstrual cycle were tested four times (5 to 7 days apart) across the menstrual cycle. The test battery included the electrophysiological measurement of auditory evoked response in brainstem and the speech performance in dichotic listening with monosyllables as stimulus pairs. The dichotic listening task was conducted under the non-forced, forced-right and forced-left attention. The central conduction time was defined by the time elapsed between two auditory elicited responses along the auditory pathway. The language lateralization in dichotic listening was expressed in ear advantage, which was the right-ear score minus the left-ear score. The results showed that the effects of test time were significant on both the central conduction time and the ear advantage under the forced-left attention. Overall, the interaural difference in the central conduction time correlates with the ear advantage (non-forced attention) at the beginning of the menstrual cycle. The change in central conduction time between two test times correlates significantly with the change in ear advantage under the non-forced and forced-left attention. Conclusively, the central conduction time depends on the time during the menstrual cycle, which in turn may affect the performance in dichotic listening.