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Why do babies born prematurely experience more developmental delays? iStock

Babies born prematurely show abnormal responses to new experiences and difficulties in using past experiences to predict what is likely to happen. This may explain why they are more at risk of developmental delays and learning disabilities later in life.

Every year globally, around 15 million babies are born too early – that is, before 37 weeks of pregnancy are completed. Prematurity is the leading cause of death globally among children under the age of five, and for survivors it can result in a lifetime of disability.

Lauren Emberson, the author of a new study on the subject published in Current Biology, told IBTimes UK:

"Each week of prematurity is associated with reductions in IQ level, and infants born extremely prematurely are three to six times more likely to experience learning disabilities once they reach school. Prematurity before 32-week gestations also significantly increases the risk of autism, language delays, and motor difficulties".

Prematurity is associated with medical complications, and there has already been a good amount of research done on the effects of those medical complications on developmental outcomes. Additionally, care for premature infants has improved in recent years, and some babies have no complications.

"However, it is only in the last few years that doctors and researchers have realised that prematurity on its own, independent of medical complications, predict these deficits. This is not well studied and not well understood", added Emberson, an assistant professor of psychology at Princeton University.

Her study is therefore one of the first to look at development in these at-risk infants early and to observe differences in how their brains are learning and developing. It investigates whether premature but otherwise healthy babies use what they have learnt previously to shape their expectations about the world, like 'normal' babies do. They showed that premature babies demonstrate an altered type of brain response to expectations, known as top-down processing.

Baby stimuli and brain scans

The scientists tested the neural capacity of 100 infants aged six months to predict upcoming stimuli. Half of them were born at full term and the other half born prematurely.

The babies were presented with associations of a sound — such as a honk from a clown horn or a rattle — and an image of a red cartoon smiley face. Using a technique known as functional near-infrared spectroscopy, which measures oxygenation in regions of the brain, the researchers were able to assess the level of brain activity they experienced during the experiment.

learning language
Babies in the experiment were exposed to sound and visual stimuli iStock

After exposing all the infants to these sound and image patterns, the researchers conducted the experiment again, but in a number of babies, they omitted showing then the image after the sound. In full-term babies, brain activity was detected in parts of the brain responsible for vision, even when the image didn't appear as expected.

Such top-down sensory predictions would suggest that these babies learned from previous trials, and expected to see the image associated with the sound as a result. However, no activity in these visual areas of the brains of premature babies were registered in these trials.

The findings indicate that prematurity may disrupt top-down processing. This brain ability is essential in quickly and effectively processing and predicting information for both infants and adults, and efficiently detecting when something unexpected happens. The disruption could partly explain the developmental problems that babies born too early often face as they grow up.

"It means that those born prematurely are not benefiting from their learning and are not getting better at understanding or processing the world as a result. This lack of top-down processing also can impact learning because it reduces abilities to detect unexpected situations", Emberson explained.

A major goal of this research is early identification and the children would now be followed up until the age of two years to see if these early neural deficits predict language and learning difficulties later in life.

"If all of these deficits might stem from a more central and fundamental difference in how their brain is learning and developing, we could potentially help infants much earlier and focus on these central deficits. With this work it is even possible to intervene so early and so effectively that infants would never miss a milestone or struggle in their development", the scientist concluded.