Scientists say a new study shows that the brain gradually develops to an adult-like state from 35 weeks in development.
Dr Rebeccah Slater, UCL Neuroscience, Physiology and Pharmacology, said: ‘Premature babies who are younger than 35 weeks have similar brain responses when they experience touch or pain.
‘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, 21 of which were born prematurely, for the study published online in the journal
Current Biology.
They measured 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.
The scientists measured electrical brain activity when they were undergoing a routine heel lance – a standard procedure which is essential to collect blood samples.
Premature babies reacted to the heel lance with non-specific general bursts of electrical activity in the brain.
But by 35-37 weeks, scientists recorded localised activity in specific areas of the brain, indicating the ability to differentiate between touch and pain.
Dr Lorenzo Fabrizi, lead author of the paper from UCL Neuroscience, Physiology and Pharmacology, said: ‘We are asking a fundamental question about human development in this study – when do babies start to distinguish between sensations?
‘In very young brains all stimulations are followed by bursts of activity, but at a critical time in development babies start to respond with activity specific to the type of stimulation.’
He added: ‘Of course, babies cannot tell us how they feel, so it is impossible to know what babies actually experience. We cannot say that before this change in brain activity they don’t feel pain.’
The research was funded by the Medical Research Council and the Wellcome Trust.
