Newborn babies’ brains develop rapidly in response to sensory stimuli, and even though they have been found to respond to their mother’s voice and heartbeat before birth, little has been known about how and to what extent this prenatal auditory stimulation shapes the brain.
Now, a study by HMS researchers shows that the human brain is capable of forming neural connections in response to maternal stimuli even at a very early gestational age. Amir Lahav, an HMS assistant professor of pediatrics, is senior author of the paper, published in the January issue of the Proceedings of the National Academy of Sciences.
The researchers set out to determine whether enriching the environment of prematurely born infants with sounds that mimicked what a full-term baby would have “heard” in the womb would result in structural changes in the auditory cortex.
Forty extremely premature infants (25 to 30 weeks’ gestation) in the newborn intensive care unit at Brigham and Women’s Hospital were randomized into two groups. Twenty-one of the infants were exposed inside their incubators to low-frequency recordings of their own mother’s voice and heartbeat, similar to what a baby would hear in the womb, for three hours each day. Nineteen other infants, the control group, were exposed to the noises commonly occurring in the NICU. After about 30 days, the researchers used cranial ultrasonography to determine the size of each infant’s auditory cortex. They found that the auditory cortices of infants in the maternal sound group were significantly larger compared with those of infants in the control group.
The authors suggest that the high plasticity of the auditory cortex in response to maternal sounds at this critical prenatal stage might provide the “auditory fitness” necessary to help shape postnatal brain development, somewhat akin to priming a pump. In addition, recorded maternal sounds may be especially helpful for medically fragile premature babies, whose exposure to live maternal stimulation is often limited because the infants spend so little time outside the incubators.
The authors note that although exposing preterm infants to biologically authentic recordings of their mother’s voice and heartbeat does not begin to address all the challenges facing these babies, it could negate some of the deleterious environmental effects of the NICU and, potentially, ready the brain for hearing and language development.