Suckling infants trigger surges of trust hormone in mothers' brains

Researchers from the University of Warwick, in collaboration with other universities and institutes in Edinburgh, France and Italy, have for the first time been able to show exactly how, when a baby suckles at a mother's breast, it starts a chain of events that leads to surges of the "trust" hormone oxytocin being released in their mothers' brains.

The study, published on 18th July in the journal PLoS Computational Biology, focuses on the role of oxytocin, a very important hormone recently found be involved in the enhancement of "trust" and love in humans and animals. Oxytocin has long been known to be the trigger that, when released into the blood, causes milk to be let down from the mammary gland. When oxytocin is released within the brain, it also helps to strengthen the bond between mother and child, but to have these effects, a very large amount must be released abruptly to cause a wave of the hormone that can spread through the brain.

What was not known before this study is exactly how the few thousand neurones, which are specialized to release oxytocin, are marshalled together to produce a sufficiently intense burst of activity to do all of that. In fact, even when a child is not suckling these neurons are continually producing oxytocin but in small amounts and in a much more uncoordinated way. Previous studies on individual neurons have found no obvious way of modifying their behaviour to get the coordinated response needed to produce the large, regular pulses of oxytocin that are needed.

Now this University of Warwick led team of experimental neuroscientists and theoreticians have found a likely answer. The neuroscientists have found that in response to suckling the neurons start releasing oxytocin from their "dendrites" as well as from their nerve endings - this was unexpected because dendrites are usually thought as the part of a neurone which receive, rather than transmit information.

The dendrites usually create a weak network of connections between neurons. However the researchers have now shown that the release of oxytocin from the dendrites allows a massive increase in communication between the neurons. This co-ordinates a "swarm" of oxytocin factories, producing massive intense bursts of oxytocin release at intervals of around 5 minutes or so.

The synchronous activation of the few thousand oxytocin producing neurons is an example of "emergent" process. It develops in just the same way as a flock of birds or insects - closely coordinated action developing without a single leader.

University of Warwick computational biology researcher Professor Jianfeng Feng said:

"We knew that these pulses arise because, during suckling, oxytocin neurons fire together in dramatic synchronized bursts. But exactly how these bursts arise has been a major problem that has until now eluded explanation. This research has allowed us to incorporate all the latest research in a large computational model of the whole population of oxytocin cells."

"In this model we have shown that the dendritic interactions are enhanced enough to trigger a massive positive-feedback on activity. The model gives us a possible explanation of an important event in the brain that could be used to study and explain many other similar brain activities."

Source: University of Warwick

Related stories:

Natural childbirth linked to stronger baby bonding than C-sections
The bonds that tie a mother to her newborn may be stronger in women who deliver naturally than in those who deliver by cesarean section, according to a study published by Yale School of Medicine researchers in the October issue of Journal of Child Psychology and Psychiatry.
Natural childbirth makes mothers more responsive to own baby-cry
A new study has found that mothers who delivered vaginally compared to caesarean section delivery (CSD) were significantly more responsive to the cry of their own baby, identified through MRI brain scans two to four weeks after delivery.
A hormone that enhances one's memory of happy faces
Oxytocin was originally studied as the "milk let-down factor," i.e., a hormone that was necessary for breast-feeding. However, there is increasing evidence that this hormone also plays an important role in social bonding and maternal behaviors. A new study scheduled for publication in the August 1st issue of Biological Psychiatry now shows that one way oxytocin promotes social affiliation in humans is by enhancing the encoding of positive social memories.
Reflecting on values promotes love, acceptance
No one enjoys being told that their behavior is harmful to themselves or others. In fact, most people respond defensively when confronted with evidence that their behavior is irrational, irresponsible, or unhealthy. Fortunately, research has shown that just a few minutes of writing about an important value can reduce defensiveness. Previous research by David Sherman at the University of California at Santa Barbara and his collaborators have shown that coffee drinkers are more willing to accept information that drinking coffee harms their health if they first write a few sentences about their most important value.
Placenta removal -- a safer method after Caesareans
In Caesarean deliveries the placenta is usually removed by hand or by a technique known as 'cord traction'. A recent systematic review by Cochrane Researchers shows that cord traction poses less risk to the mother than manual removal.
Brain's 'trust machinery' identified
The brain centers triggered by a betrayal of trust have been identified by researchers, who found they could suppress such triggering and maintain trust by administering the brain chemical oxytocin. The researchers said their findings not only offer basic insights into the neural machinery underlying trust; the results may also help in understanding the neural basis of social disorders such as phobias and autism.
Genetic links to impaired social behavior in autism
Individuals with autism spectrum disorders (ASD) show profound deficits in social interactions and communications, and display repetitive behaviors and abnormal responses to sensory experiences. One aspect of an autistic child’s impaired social abilities is their lack of affiliative behaviors, i.e., behaviors such as touching and hugging that strengthen social bonds. On May 15th, Biological Psychiatry is publishing an article that reports new findings on genetic bases of these behaviors.
'Love Hormone' Promotes Bonding
Gazing into your lover’s eyes isn’t only romantic; it may also mimic early attachments that forever alter your brain and body.

News discussion:

General Science news