Premature babies in incubators grew larger brains after being exposed to the recorded sounds of their mothers’ voices and heartbeats, a study has found.
Tests also showed that they were better at focusing on sounds than premature babies receiving routine care.
The findings highlight the fact that an incubator is a “neurodevelopmental dungeon” where a baby’s natural brain development is stunted, said lead researcher Dr Amir Lahav, from Harvard Medical School in the US.
Previous studies had shown that children born prematurely often have difficulty listening and paying attention in noisy environments.
In the classroom, for instance, they might find it hard to pick up on what the teacher is telling them.
Dr Lahav’s research suggests that much of the problem stems from their early experience in the neonatal intensive care unit (Nicu).
Instead of the muffled low frequency womb sounds of their mothers, their primary sound source is the noisy fan of the incubator.
“What inspired us to go into this work was the fact that when we look at how premature babies are doing later in life .. those babies too often will have a wide variety of developmental issues down the road that are all related to auditory function in some way or another,” said Dr Lahav.
“We see a very high likelihood in those premature babies of having language deficits, auditory processing disorders, and attention deficits.
“This has made us wonder if the hospital environment in the neo-natal intensive care unit (Nicu) is indeed optimal for the brain development of these babies.”
His experiment involved recording the heartbeats and voices of mothers of premature babies and playing them back to the infants for three hours a day during the first month of life. The sounds included the mothers singing, reading a story, and speaking “baby talk” as if engaging with their infants.
Those babies turned out to be significantly advantaged over other premature babies looked after in the normal way and not exposed to the sounds.
Not only did they weigh more – putting on an extra two grams per kilogram of bodyweight per day – but head ultrasounds showed the sound-processing region of their brain, the auditory cortex, was larger.
They were also better than non-sound exposed babies at focusing on human voices – and not just those of their mothers.
This ability was tested by looking at how their pupils dilated, a sign of mental attentiveness in babies.