The ability for a baby’s cry to trigger the release of breastmilk has been observed for many years—but how exactly this happens, has long been a mystery.
However, new research has brought us one step closer to understanding the mechanisms at play at breastfeeding, and the changes that occur within a postpartum woman’s brain.
A new study, published in Nature, has found that 30 seconds of continuous crying by mouse pups triggers the release of oxytocin, the chemical which controls the milk-release response in mothers.
According to the study, the mouse pup’s cries send information to an area of the mother’s brain called the posterior intralaminar nucleus of the thalamus (PIL). This brain area then sends a signal to the oxytocin-releasing brain cells (neurons) in a different region called the hypothalamus.
Usually, the hypothalamus neurons are locked to prevent false alarms that can waste milk. However, the study shows that after 30 seconds of continuous crying, the signals from the PIL build up enough to unlock the neurons and trigger the release of oxytocin. The study also found that this hormone surge continues for five minutes before slowly stopping, allowing the mother mice to feed their young until they are full or start crying again.
The research doesn’t only provide important new insights into the changes that occur in the postpartum brain but also valuable understandings for those women facing breastfeeding challenges.
The study’s co-lead author and graduate student at NYU Langone Health, Habon Issa says, “Our findings uncover 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.”
The study also discovered just how important the communication between the PIL and oxytocin neurons actually are, finding that when the communication was disrupted, the mothers displayed decreased motivation to care for their pups. However, when the system was reactivated, the mothers continued, despite their exhaustion.
“These results suggest that the crying-prompted brain circuit is not only important for nursing behavior, but also for maintaining a mother’s attention over time and encouraging effective care of her young even when she is exhausted,” the study’s senior author Dr. Robert C. Froemke said.
Froemke also emphasised the importance of applying the study to human mothers, stating “A mouse mom is different from a human mom, but in broad strokes we’d expect it to be similar,” he said. “It’s baffling. We can put a robot on mars and don’t understand the basics of how we feed our children and breastfeed.”
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