Pheromone from mother's milk may rapidly promote learning in newborn mammals

The findings, which deepen our understanding of pheromone function and how learning occurs in the earliest days of life, are reported in the October 10th issue of the journal Current Biology, published by Cell Press, by a team including Gérard Coureaud and Anne-Sophie Moncomble and colleagues from the Centre Européen des Sciences du Goût in Dijon, which is supported by the Centre National de la Recherche Scientifique, and the Université de Bourgogne and Inra. Benoist Schaal, another author of the study, is the director of the Centre Européen des Sciences du Goût.

Newborn mammals are highly dependent on their mother's milk for survival, and they typically exhibit a defined sequence of actions when searching for milk. This searching behavior rapidly becomes increasingly directed, showing that mammalian newborns are efficient learners. Past studies of this very early learning in the European rabbit (Oryctolagus cuniculus) have shown that newborn pups engage in typical food-searching movements in response to olfactory signals that include the mammary pheromone secreted in mother's milk. The ability of newborns to rapidly improve their milk-finding skills likely involves learning that “new” odors–for example, those from the mother's abdomen, or of milk itself–are associated with food.

In the new work, the researchers investigated whether the mammary pheromone plays a role in the ability of newborns to learn to associate other odors with the availability of milk. By presenting newborns with the pheromone in combination with an otherwise “neutral” odor and subsequently testing whether the neutral odor alone would later elicit the typical food-searching behavior in the pups, the researchers were able to show that the pheromone is indeed effective at promoting the ability of the newborns to learn the significance of new odors. The researchers showed that this pheromone-induced learning is efficient from the time of birth and is capable of promoting the learning of successive different odorants presented to newborn pups.

Given its ability to promote the learning of new olfactory cues, the mammary pheromone may act as a kind of organizing signal that boosts the brain's ability to associate new odors with milk availability. This would in turn facilitate an essential skill: the ability of newborn pups to rapidly hone their suckling instincts during the first days of life.