That New Baby Smell

New moms’ brains show a stronger response to infant body odor than do the brains of women who aren’t mothers.

By | September 25, 2013

WIKIMEDIA, IMPERIAL WAR MUSEUMS COLLECTIONAnyone who has snuggled a clean, new baby probably also noticed the child’s distinctive, pleasing smell. In a study published this month (September 5) in Frontiers in Psychology, researchers used functional magnetic resonance imaging (fMRI) to show that the brains of new mothers are more responsive to this scent than the brains of women who are not mothers.

Scientists from Germany, Canada, Sweden, and the U.S. recruited both women who had never had a baby and women who had recently become mothers (three to six weeks prior to enrollment). They also collected cotton undershirts worn by newborns unfamiliar to the women during the babies’ stay at a Dresden nursery . The researchers passed clean air over the undershirts and delivered that air to the adult participants’ nostrils, studying their responses via fMRI. All of the women ranked the odors’ familiarity, pleasantness, and intensity comparably, and their brains responded to the scents in the same regions: the putamen, and the dorsal and medial caudate nuclei. But the new mothers’ brains showed significantly increased neuronal activation in those areas compared with the nulliparous participants, suggesting that maternal status may regulate brain responses to infant body odor.

“The olfactory—thus non-verbal and non-visual—chemical signals for communication between mother and child are intense,” said author Johannes Frasnelli of the University of Montreal in a statement. Frasnelli explained that the brain areas activated in both groups of women are related to reward and motivation, and suggested that the higher level of activation in these brain regions among the mothers may be the result of an adaptation that ensures the mother will take good care of her baby.

“For those first few months babies are mostly just needing to be cared for and we don’t get much positive feedback from them,” maternal health psychologist Diane Sanford told NBC’s Today. “So the fact that the pleasure centers are activated makes it more rewarding at a time when parenthood is very intensive and depleting,” she added.

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Avatar of: James V. Kohl

James V. Kohl

Posts: 481

September 25, 2013

These authors provide even more evidence of epigenetic cause and effect, which links olfactory/pheromonal input directly to de novo creation of olfactory receptor genes and non-random experience-dependent adaptive evolution via conserved molecular mechanisms in species from microbes to man. For example, in all other mammals, food odors and complex mixtures of body odors, which are called pheromones in all other species, elicit psychobiological processes that are clearly attributed to nutrient-dependent pheromone-controlled adaptive evolution in my model. See: Socioaffective Neuroscience & Psychology 2013, 3: 20553

This newer report uses tentative phraseology like "A direct and strong causal link between biological reward... remains to be demonstrated...." However, the newer report clearly links ecologically salient odors (e.g., food odors) and social odors called pheromones to the molecular epigenetics of hormone-organized and hormone-activated biological embedding in species from microbes to man. That is the power of brain imaging when it addresses the foundations of physiology and behavior at a deep causal level. It makes possible the meaningful interpretation of results in the context of a model of cause and effect.

It will be interesting to see whether experiments continue to support the role of nutrient-dependent single amino acid substitutions in morphogenesis and pheromone-controlled reproduction, which has already been detailed in microbes, nematodes, insects, other mammals and in a human population that appears to have adaptively evolved during the past ~30K years in what is now central China, as reported in my last published work (linked above).

However, given the importance of the extant literature to adaptive evolution, which is clearly not akin to unsubstantiated reports of mutation-driven evolution, I was somewhat surprised to not see a citation to Human breast areolae as scent organs: morphological data and possible involvement in maternal-neonatal coadaptation which would have added a contextual basis for the brain imaging as does A pheromone to behave, a pheromone to learn: the rabbit mammary pheromone. Would citations to works like those make the development of human behavior appear to be too animalistic, or is the nutrient-dependent pheromone-controlled infant - mother bond less important than the role of complex mixtures of body odors in the mother-infant bond?

Avatar of:

Posts: 23

September 28, 2013

I do not understand why males, fathers and otherwise, were not tested in this manner. It would have been an excellent opportunity to see if this was a gender mediated phenomenon.

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