It has long been possible to observe very premature babies pull away from painful stimuli and react physically as though they were in pain by crying, showing faster pulses and breathing rates and even changes in their blood hormone levels that mimic pain response in older human beings. But that pain has been dismissed as mere "animal reflex," most recently by the Journal of the American Medical Association. (Never mind that we do not encourage anyone to cause pain in animals or that the authors of that last article are connected to the actual practice of elective abortion and could have motives other than the study of pure science. Such as justifying the procedure itself.)
However, there is now evidence by means of functional scans that show that the structures of the brain that are known to process pain are involved as young as 24 weeks. The on-line news service, Medical News Today, discusses the methods for measuring the pain response of premature babies in the nursery, as they undergo a heel stick for a blood test:
Brain scans taken while babies were having blood tests registered a surge of blood and oxygen in the sensory area in babies' brains, which indicates that the pain was processed in the higher levels of the brain. The somatosensory cortex is involved in processing sensations from the body surface and is known to be linked to pain sensation in adults.
The results were found using near-infrared spectroscopy, which - like fMRI scans - works by measuring blood levels and oxygenation in the brain. During clinical care work, essential for ensuring a premature baby's stability, eighteen babies aged between 25 and 45 weeks from conception were studied. Scientists registered the brain activity in the babies at the moments before, during and after nurses performed routine blood tests using a heel lance.
Professor Fitzgerald added: “The importance of this is clear. The UK has the highest rate of low birth-weight babies in Western Europe; 12% all babies born need some level of special care at birth (~ 80,000 per annum) and 2.5% need neonatal intensive care (~ 17,000 per annum). Estimates show that in intensive care each baby is subjected to an average of 14 procedures per day, many of which are considered by clinical staff to be painful, such as heel lancing for blood tests and inserting chest tubes. Furthermore there is evidence that these repeated painful procedures are a significant stressor and lead to increased sensitivity to other non-painful procedure. Since pain information is transmitted to the preterm infant cortex from 25 weeks there is the potential for pain experience to influence brain development from a very early age as the brain is highly malleable at this stage of development.”
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