Reproductive cycle-dependent plasticity of perception of acoustic meaning in mice.

How may perception, maternal motivation and behavior of female mammals change during different phases of their estrous cycle? Here, we show effects of estrous cycle phase on the perception of acoustic meaning and maternal behavior in virgin house mice (Mus musculus) during contact with young for which they were co-caring together with the mother. Cycling females in diestrus, proestrus, estrus or metestrus responded to mouse pup wriggling calls and two synthesized call models when they were in a "nursing" position on the pups. Independent of the phase of their estrous cycle, the virgin females' response rates to naturally vocalized calls and the rates of their spontaneous maternal behavior were about half of those of mothers in the same behavioral setting. This suggests that the maternal motivation of virgin females is generally half of that of mothers but rather constant during the estrous cycle. The response rates to the call models changed during the females' estrous cycles. During diestrus and proestrus (not in estrus and metestrus) they perceived acoustic differences between the call models and responded with different rates of maternal behavior. In estrus, they showed maternal behavior at a high rate and preferred the call models similar to the natural calls. In metestrus, response rates to the synthesized call models were low, so that only natural calls (not call models) released maternal behavior at a high rate. These behavioral data from house mice show remarkable similarities with perceptual plasticity and emotional and mood-dependent reactivity during the menstrual cycle in women.