Babies experience pain before they can comprehend it

A study led by University College London used brain scans of newborn premature babies to investigate how the brain develops pain processing in the early stages of development. 

The results show that the three neural networks responsible for sensing, understanding and responding to pain develop at different rates in infants leading them to experience pain before their brains can make sense of it.

“Pain is a complex experience with physical, emotional, and cognitive elements,” says lead author Professor Lorenzo Fabrizi. 

“In adults, pain processing relies on a functional network of brain regions called the ‘pain connectome’, with different regions working together to help us experience pain, each part responsible for different aspects of it.”

The study focused on the three main subnetworks of how people feel and understand pain.

The first subnetwork is about noticing the pain and physically sensing it, this is known as the sensory-discriminative aspect. The affective-motivational subnetwork is about how the pain makes some feel emotionally and the cognitive-evaluative subnetwork is how people interpret the pain.

“In newborn babies, this network is underdeveloped, which could mean that pain experience in newborns is totally different from the way we, as adults, understand it,” says Fabrizi. 

To outline how these three pain subnetworks mature in babies, the researchers used brain MRI data from two of the largest datasets available, the Developing Human Connectome Project and the Human Connectome Project. 

From these data sets, the research team analysed 372 infants, who were anywhere from less than 32 weeks up to 42 weeks. A baby is considered premature if it is born before 37 weeks of pregnancy. 

The scans were all taken when the infants were all less than 2 weeks old. 

The results found that the first subnetwork of pain to develop is the sensory-discriminative network, which develops at around 34-36 weeks after conception.

What this means is that babies born prematurely can sense pain, but since the other aspects of the pain network have not developed, they might not be fully capable of understanding or responding to the pain. 

 “Our results suggest that preterm babies may be particularly vulnerable to painful medical procedures during critical stages of brain development,” says Fabrizi. 

The findings revealed that babies can emotionally respond to pain around the 36–38-week mark when their affective-motivational network matures. 

However, the research shows that the infants can understand pain only after the cognitive-evaluation subnetwork matures, which is after at least 42 weeks since conception. 

The findings support the research team’s previous study from 2023 that had found that premature babies do not reduce their reaction to repeated pain over time. 

These new findings suggest this might be because preterm babies have not fully developed their pain networks and therefore cannot emotionally or cognitively understand the pain they are experiencing. 

“The findings therefore emphasise the importance of informed paediatric care, including the role of tailored pain management and carefully planned timing of medical interventions for newborns, particularly those born preterm,” says Fabrizi.

The research, which was funded by the Medical Research council, is published in Pain.

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