New research at the University of Adelaide has demonstrated that
teenagers born prematurely may suffer brain development problems that directly
affect their memory and learning abilities.
The research, conducted by Dr
Julia Pitcher and Dr Michael Ridding from the University of Adelaide's Robinson
Institute, shows reduced 'plasticity' in the brains of teenagers who were born
preterm (at or before 37 weeks gestation).
The results of the research are
published today in the Journal of Neuroscience.
"Plasticity in the brain is
vital for learning and
memory throughout life," Dr Pitcher says. "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 says.
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 says. "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 says.
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