Abstract
In humans, females process a sound’s harmonics more robustly than males. As estrogen regulates auditory plasticity in a sex-specific manner in seasonally breeding animals, estrogen signaling is one hypothesized mechanism for this difference in humans. To investigate whether sex differences in harmonic encoding vary similarly across the reproductive cycle of mammals, we recorded frequency-following responses (FFRs) to a complex sound in male and female rats. Female FFRs were collected during both low and high levels of circulating estrogen during the estrous cycle. Overall, female rodents had larger harmonic encoding than male rodents, and greater harmonic strength was seen during periods of greater estrogen production in the females. These results argue that hormonal differences, specifically estrogen, underlie sex differences in harmonic encoding in rodents and suggest that a similar mechanism may underlie differences seen in humans.
Highlights
In humans, females process a sound’s harmonics more robustly than males
The change in harmonic encoding is greater than would be expected by differences in tract length between the sexes[1,8], implicating hormonal differences emerging during adolescence
The goal of this study was to determine whether male and female rodents show differences in harmonic encoding, similar to that seen in humans, and whether the magnitude of these differences vary with changes in hormone levels across the female estrous cycle
Summary
Females process a sound’s harmonics more robustly than males. As estrogen regulates auditory plasticity in a sex-specific manner in seasonally breeding animals, estrogen signaling is one hypothesized mechanism for this difference in humans. Female rodents had larger harmonic encoding than male rodents, and greater harmonic strength was seen during periods of greater estrogen production in the females These results argue that hormonal differences, estrogen, underlie sex differences in harmonic encoding in rodents and suggest that a similar mechanism may underlie differences seen in humans. In support of a hormonal influence on harmonic encoding, estradiol treatment of non-breeding female midshipman fish amplifies their peripheral sensitivity to the harmonics of the male fish’s calls, akin to the enhanced harmonic response seen in breeding midshipman females[9] These systematic fluctuations with piscine estrogen level provide evidence of a link between hormone levels and harmonic encoding in seasonally-breeding animals. The goal of this study was to determine whether male and female rodents show differences in harmonic encoding, similar to that seen in humans, and whether the magnitude of these differences vary with changes in hormone levels across the female estrous cycle
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