Brain scans of children who were born prematurely have revealed differences in the connectivity of key regions that may play a role in developmental disorders.
Previous studies have already highlighted that children who are born preterm are more at risk of autism and other behavioural conditions, such as the poor attention that is associated with ADHD, or attention deficit hyperactivity disorder.
The new findings could help doctors understand why preterm children are so often affected, and work out whether medications or different styles of care could help the children reach their full potential.
Researchers at King’s College London scanned the brains of 66 infants on average 42 weeks after their mothers’ last period before the birth. Forty seven of the babies were born prematurely, at less than 33 weeks. The other 19 babies were born on average after 40 weeks gestation.
In their final weeks in the womb, babies’ brains are building connections at an incredible rate, which makes them particularly sensitive to changes in the last trimester. If a baby is born prematurely, the crucial period of brain growth happens in the radically different environment of the neonatal unit.
From the MRI scans, the scientists found that infants born prematurely had increased connectivity in only one part of the brain they tested. A region called the thalamus, a kind of neural relay station, was better connected to a part called the lateral sensory cortex, which handles signals from the mouth, lips and jaw. The result might be explained by pre-term babies breast or bottle feeding much earlier, or being given dummies while on supportive breathing machines.
Other parts of the brain were the same between the two groups of infants. The scans showed similar connectivity between the visual, auditory and sensorimotor areas and the thalamus in both the premature children and those born at term.
But stark differences were spotted elsewhere in the brain. The most striking involved the connectivity of a group of brain areas known collectively as the salience network. In the pre-term infants, the neural connections were reduced between the thalamus and the prefrontal, insular and anterior cingulate regions of the brain.
“In studies of adolescents and adults, these areas form the salience network, and that network is found to be disrupted in conditions such as ADHD and autism. Premature infants are at greater risk of both of these,” Hilary Toulmin, a clinical research fellow at King’s, told the Guardian.
“In the case of ADHD, it is particularly inattention which is associated with preterm birth. They are not hyperactive, but have poor concentration and perhaps therefore go unnoticed more easily.”
All of the information we receive from the outside world, including vision, sound and touch, passes through the thalamus and onwards to specific parts of the cortex for processing. The sight of a car, for example, will pass from the eyes and retina to the thalamus and then to the visual cortex.
“The areas affected in the premature infants are the areas of the thalamus which are connected to many areas of the cortex,” said Toulmin, whose study appears in Proceedings of the National Academy of Sciences.
“There are enormous differences between being in the womb and being in a neonatal unit. As parents of preterm infants know very well, first learning to breathe unassisted, then learning to breast or bottle feed so that they don’t have to be fed milk through a tube, and be able to maintain their body temperature without an incubator to help, are among the first challenges.
“In the womb, there is perfect nutrition delivered into the baby’s bloodstream, regulation of temperature, and protection against infection delivered from the mother in the last trimester. So there are many influences before they have their MRI scan,” Toulmin said.
“In the future, it will help us to test whether changes in care, or different medications during the preterm period improve the outcome of these children. It is important to remember that the effects of prematurity persist into adulthood,” she said.
A stimulating play environment is beneficial for preterm children, and parents of children who have cognitive and social problems at the age of two are encouraged to read to their children, point out objects, and encourage the children to join in. Trials are ongoing with computer games that encourage cognitive development in eight-year-olds who were born prematurely.
guardian.co.uk © Guardian News & Media Limited 2010