Premature babies-even those born a week or two early-are more likely to suffer brain development problems that affect memory and learning skills later in life, Australian researchers have found.
Researcher Julia Pitcher from the University of Adelaide's Robinson Institute said the study of 40 people, including 28 children aged between 13 and 14, found virtually all of those born at 37 weeks or less had brains with reduced levels of "plasticity", which helps the brain reorganise itself and improves memory.
"Plasticity in the brain is vital for learning and memory throughout life," Dr Pitcher said.
"It enables the brain to reorganize itself, responding to changes in environment, behavior and stimuli by modifying the number and strength of connections between neurons and different brain areas. Plasticity is also important for recovery from brain damage.
"We know from past research that preterm-born children often experience motor, cognitive and learning difficulties. The growth of the brain is rapid between 20 and 37 weeks gestation, and being born even mildly preterm appears to subtly but significantly alter brain microstructure, neural connectivity and neurochemistry.
"However, the mechanisms that link this altered brain physiology with behavioral outcomes - such as memory and learning problems - have remained unknown," Dr Pitcher said.
The researchers compared preterm adolescents with those born at term, and also with term-born adults. They used a non-invasive magnetic brain stimulation technique, inducing responses from the brain to obtain a measure of its plasticity. Levels of cortisol, normally produced in response to stress, were also measured to better understand the chemical and hormonal differences between the groups.
"Teenagers born preterm clearly showed reduced neuroplasticity in response to brain stimulation," Dr Pitcher said.
"Surprisingly, even very modest preterm birth was associated with a reduced brain response. On the other hand, term-born teenagers were highly 'plastic' compared with adults and the preterm teens.
"Preterm teens also had low levels of cortisol in their saliva, which was highly predictive of this reduced brain responsiveness. People often associate increased cortisol with stress, but cortisol fluctuates up and down normally over each 24-hour period and this plays a critical role in learning, the consolidation of new knowledge into memory and the later retrieval of those memories. This might be important for the development of a possible therapy to overcome the neuroplasticity problem," she added.
The study was recently published in the Journal of Neuroscience. (ANI)