Maheshwar Kruthika V, Stuart Abigail E, Kay Leslie M
Master of Arts Program in the Social Sciences, The University of Chicago, Chicago, Illinois, United States.
Institute for Mind and Biology, The University of Chicago, Chicago, Illinois, United States.
J Neurophysiol. 2025 Jan 1;133(1):257-267. doi: 10.1152/jn.00222.2024. Epub 2024 Dec 19.
In many species, olfactory abilities in females are more acute than those in males. Studies in humans show that women have lower olfactory thresholds and are better able to discriminate and identify odors than men. In mice, odorants elicit faster activation from a larger number of olfactory bulb glomeruli in females than in males. Our study explores sex differences in olfaction in Long Evans rats from a behavioral and electrophysiological perspective. Local field potentials (LFPs) in the olfactory bulb (OB) represent the coordinated activity of bulbar neurons. Olfactory gamma (65-120 Hz) and beta (15-30 Hz) oscillations have been functionally linked to odor perception. Spontaneous and odor-evoked OB LFPs were recorded from awake rats at the same time for 12 days. Odors used included urine of both sexes and monomolecular odorants characterized previously for correlation of volatility with behavior and OB oscillations. Sampling duration in a habituation context, baseline gamma and beta power, and odor-elicited beta and gamma power were analyzed. We find that females sample odorants for a shorter duration than males (just over 1-s difference). Although baseline gamma and beta power do not show significant differences between the two sexes, odor-elicited gamma and beta power in females is significantly lower than in males. Neither sampling duration nor beta and gamma power in females varied systematically with day of estrus. We further verify that variance of these behavioral and physiological measures is not different across sexes, adding to growing evidence that researchers need not be concerned about often-claimed additional variance in female subjects. Olfaction plays a large role in evolutionary processes. However, we know little about sex differences in olfactory bulb neurophysiology, and many scientists believe that females are more variable because of estrus. We show that female rats sniff odors for shorter durations than males and have lower power in neural oscillations related to cognition. Estrus was not related to variance in any measures. Finally, males and females show equal variance on these behavioral and physiological processes.
在许多物种中，雌性的嗅觉能力比雄性更为敏锐。对人类的研究表明，女性的嗅觉阈值更低，比男性更善于辨别和识别气味。在小鼠中，与雄性相比，气味剂能在雌性小鼠的更多嗅球肾小球中引发更快的激活。我们的研究从行为和电生理角度探索了长 Evans 大鼠嗅觉中的性别差异。嗅球（OB）中的局部场电位（LFP）代表了球部神经元的协同活动。嗅觉γ（65 - 120 赫兹）和β（15 - 30 赫兹）振荡在功能上与气味感知相关。在 12 天的时间里，同时从清醒的大鼠身上记录自发的和气味诱发的 OB LFP。所使用的气味包括两性的尿液以及先前已表征其挥发性与行为和 OB 振荡相关性的单分子气味剂。分析了在适应环境中的采样持续时间、基线γ和β功率以及气味诱发的β和γ功率。我们发现，雌性对气味剂的采样持续时间比雄性短（相差仅 1 秒多一点）。虽然基线γ和β功率在两性之间没有显著差异，但雌性中气味诱发的γ和β功率明显低于雄性。雌性的采样持续时间以及β和γ功率均未随发情期天数呈现系统性变化。我们进一步证实，这些行为和生理指标的方差在两性之间并无差异，这进一步证明了研究人员无需担心常被提及的雌性受试者中额外的方差问题。嗅觉在进化过程中起着重要作用。然而，我们对嗅球神经生理学中的性别差异知之甚少，许多科学家认为由于发情期，雌性的变异性更大。我们表明，雌性大鼠嗅闻气味的持续时间比雄性短，并且在与认知相关的神经振荡中功率较低。发情期与任何指标的方差均无关。最后，雄性和雌性在这些行为和生理过程中表现出相等的方差。
