They also found that that they are also likely to experience delay in the development of the auditory cortex, a brain region essential to hearing and understanding sound.
Lead researcher Brian Monson from the University of Illinois said, "We have a pretty limited understanding of how the auditory brain develops in preterm infants".
"We know from previous research on full-term newborns that not only are fetuses hearing, but they're also listening and learning", Monson added.
To better understand how the auditory cortex matures in the last trimester of gestation, the team of researchers turned to a large dataset collected at the St. Louis Children's Hospital Neonatal Intensive Care Unit between 2007 and 2010.
The 90 premature infants in the study had undergone magnetic resonance imaging one to four
times in the course of their stay in the NICU.
Another 15 full-term babies were recruited from the Barnes-Jewish Hospital in St. Louis and scanned within the first four days of life.
The team focused on the primary auditory cortex, which is the first cortical region to receive auditory signals from the ears via other parts of the brain and the nonprimary auditory cortex, which plays a more sophisticated role in processing those stimuli.
The results revealed that by 26 weeks of gestation, the primary auditory cortex was in a much more advanced stage of development than the non-primary auditory cortex.
Both regions appeared less developed at 40 weeks in the preterm infants than in the full-term babies.
The team also found an association between the delayed development of the nonprimary auditory cortex in infancy and language delays in the children at age two, suggesting that disruptions to this part of the brain as a result of premature birth may contribute to the speech and language problems often seen later in life in preemies, Monson noted.
The research appears in a journal eNeuro. (ANI)