Babies born prematurely show differences in brain connections that may put them more at risk of neurodevelopmental problems including autism, a study suggests.

Brain scans of premature babies, when compared with scans of full-term infants, showed less connectivity between the brain's thalamus and specific regions of the cortex supporting higher mental functions, researchers at King's College London say.

The researchers used functional magnetic resonance imaging (fMRI) to focus on specific connections in the brains of 66 infants, 47 born prematurely and at high risk of neurological impairment, and 19 who were born at full term.

The full-term babies showed a remarkably similar structure to adults in their connectivity among brain regions involved in higher cognitive functions, whereas the premature babies showed less connectivity, the say.

The finding supports previous research strongly suggesting a link between premature birth and an elevated risk of developing autism or ADHA, attention deficit hyperactivity disorder, they report in the Proceedings of the National Academy of Sciences.

The final weeks of development within the womb are vital to babies as they build brain connections at an accelerated rate, the researchers point out, and if the baby is born prematurely that critical period of brain development takes place in a neonatal unit, a radically different environment.

"There are enormous differences between being in the womb and being in a neonatal unit," says study leader Hilary Toulmin.

The most striking difference in premature babies was a reduced connection between the thalamus and parts of the brain in the prefrontal, insular and anterior cingulate regions. The thalamus is involved in sensory perception, the regulation of motor functions and of consciousness and sleep, among other functions.

Information received from the outside world - touch, vision and sound - passes through the thalamus to these other regions for processing by 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," Toulmin says. "Premature infants are at greater risk of both of these."

The brain scans of the premature babies bore this out, she says.

"The areas affected in the premature infants are the areas of the thalamus which are connected to many areas of the cortex."

The more premature the birth, the more apparent were differences in patters of brain connectivity, the researchers found.

Further studies may help in understanding how these differences relate to the difficulties in concentration, learning and social interaction many premature children will face as they grow older, Toulmin says, and ways to possibly mitigate some of the differences. A stimulating play environment helps encourage cognitive connections, and researchers will study whether possible changes in preterm medications and care might help improve outcomes as well.

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