Newborns feel pain before they fully understand it

Newborns feel pain before they fully understand it

Brain networks responsible for detecting, understanding and responding emotionally to pain develop in infants in infants, with conscious understanding of pain not fully developed until after birth, a new study led by UCL (University College London) researchers reveals.

The authors of the study, published in the journalpainexamined how different ways of processing pain develop very early by scanning the brains of prematurely born infants.

Pain is a complex experience with physical, emotional and cognitive elements. In adults, pain processing relies on a functional network of brain regions called the “pain connectome,” where different regions work together to help us experience pain, with each part responsible for different aspects.

In newborns, this network is underdeveloped, which could mean that the pain experience in newborns is completely different than we understand as adults. “

Lorenzo Fabrizi,lead author, professor,UCL -Neuroscience, Physiology and Pharmacology

The scientists, based at UCL, UCLH and King's College London, looked at three different components of pain processing: sensory-discriminative (identifying and localizing the intensity and quality of pain), affective-motivational (leading to the emotional response to pain) and cognitive-evaluative (the assessment and interpretation of pain).

Using advanced brain imaging data from two of the largest available brain magnetic resonance imaging (MRI) databases in the world – the evolving Human Connectome Project and the Human Connectome Project – the researchers mapped how these networks appeared in a group of 372 infants, mostly born from less than 32 weeks to 42 weeks after conception. The infants were all less than two weeks old when the scans took place, ensuring the results reflected the brain's intrinsic maturation without being influenced by various postnatal experiences.

The researchers compared these results to brain data from adults, as the mature pain processing networks have previously been brought out in other studies. The researchers analyzed how much the brain networks known for processing pain were functionally connected in infants at different ages.

The scientists found that the first subnetwork to reach strength and connectivity in adults is the sensory discriminative network, at around 34 to 36 weeks after conception, so babies can detect pain but are not yet fully capable of responding emotionally or interpreting the pain. Before this point, infants may have difficulty identifying which part of their body is in pain. At around 36 to 38 weeks, the affective-motivational subnetwork reaches maturity, allowing infants to identify pain as unpleasant and threatening.

The cognitive-evaluative subnetwork does not reach maturity until more than 42 weeks after conception, meaning that babies born in full terms have not yet fully developed the brain networks necessary to understand pain.

The research team previously found in a 2023 study that premature babies do not habituate (i.e., their response to repeated pain does not decrease over time) after repeated experiences of pain in medically necessary procedures. The new finding that premature babies have not fully developed the brain connections responsible for evaluating pain may help explain this.

Professor Fabrizi said: "Our findings suggest that premature infants may be particularly vulnerable to painful medical procedures at critical stages of brain development. The findings therefore highlight the importance of informed pediatric care, including the role of tailored pain management and carefully planned medical interventions for newborns, particularly those born."

The study was funded by the Medical Research Council.

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