Dr. Witelson said the findings indicate further research is needed to try to understand what mechanisms in utero are missing after birth that are essential for the normal process of neuro development.
When a fetus's brain is developing during pregnancy in utero, very little patterned sensory stimulation reaches the brain, she explained. The eyelids are closed, the infant is bathed in fluid and minimal sounds are perceived.
In contrast, once the premature infant is born, he is necessarily bombarded by a complex environment full of sights, sounds, touches and unnatural loss of movement.
"This research suggests that stimulation of the brain while it is still under construction may not be beneficial," said Dr. Witelson. "The prefrontal regions appear particularly vulnerable. Is it because they are the most premature at birth?"
The prefrontal regions of the brain that were most affected by the lack of development are important for numerous intellectual functions, including attention, planning and social judgment.
Dr. Witelson said more research is needed to consider what in utero mechanisms are essential for brain maturation and the optimal conditions and treatment needed to foster brain development for very premature infants who are treated in neonatal intensive care units early in life.