Babies can probably distinguish painful stimuli as different from general touch from around 35 to 37 weeks gestation, just before an infant would normally be born, according to new research.

“Premature babies who are younger than 35 weeks have similar brain responses when they experience touch or pain,” said Dr. Rebeccah Slater, of UCL Neuroscience, Physiology and Pharmacology, in a university press release. “After this time there is a gradual change, rather than a sudden shift, when the brain starts to process the two types of stimuli in a distinct manner.”

Scientists looked at the brain activity of 46 babies at the University College London Hospital. Twenty-one babies in the study were born prematurely, giving scientists the opportunity to measure activity at different stages of human brain development, from babies at just 28 weeks of development through to those born ‘full term’ at 37 weeks, according to the press release.

“Of course, babies cannot tell us how they feel, so it is impossible to know what babies actually experience,” said Lorenzo Fabrizi, lead author of the paper. “We cannot say that before this change in brain activity they don’t feel pain.”

However, previous studies have shown that there is a similar shift from neuronal bursts to evoked potentials in the visual system at this time, suggesting that 35-37 weeks is a time when important neural connections are formed between different parts of the brain.

The study was published online in the journal Current Biology.

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