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31st January 2024
11:57am GMT
It doesn't even have to be their own child, as soon as a little one starts sobbing some mothers begin to lactate seemingly out of nowhere.
Now researchers at NYU Grossman School of Medicine looked at the brain circuits of a dozen female mice and are believed to have discovered the reason for the phenomenon.
Hearing the sound of a newborn’s wail can trigger the release of oxytocin, a brain chemical that controls breast milk release in mothers.
Scientists found that upon hearing these wails the flood of hormones continues for roughly five minutes before tapering off to allow mothers to feed their babies and calm them down again.
Though it has been observed for centuries that crying infants cause milk letdown, the exact mechanism in the brain wasn't yet understood.
According to the findings, published in the journal Nature, when a mouse pup starts crying, sound information travels to an area of its mother’s brain called the posterior intralaminar nucleus of the thalamus (PIL).
This sensory hub then sends signals to oxytocin-releasing brain cells in another region called the hypothalamus, a control centre for hormone activity.
Most of the time these hypothalamus neurons are “locked down” by proteins that act as gatekeepers to prevent false alarms and wasted milk.
However, after 30 seconds of continuous crying, signals from the PIL were found to build up and overpower these inhibitory proteins, setting off oxytocin release.
According to one of the authors of the study, Habon Issa, they found "how a crying infant primes its mother’s brain to ready her body for nursing.
"Without such preparation, there can be a delay of several minutes between suckling and milk flow, potentially leading to a frustrated baby and stressed parent."
Interestingly, their results also revealed that the oxytocin boost only occurs in mother mice and not in females who have never given birth.
