Humans can hear music long before we are born, and preterm babies in the intensive care unit have a particularly sensitive ear. With the mufflers removed far too soon, the sounds and silences of this world can be unexpected, stressful and downright harmful to their developing brains.

Today, roughly half of all children born before the 32nd week of pregnancy will later be diagnosed with a developmental brain disorder, including attentional or emotional disorders.

During this critical time of development, a number of studies have shown that music exposure can help stabilise a premature baby's heart rate and breathing, while also improving their appetite and sleep.

Music is the art of organising sound, and researchers in Switzerland are curious if it can also be used to protect the premature brain. Their double-blind study on the effects of music in the neonatal ICU is the first of its kind, and the initial results suggest they are on to an original solution.

Among very premature babies, some of whom were almost born four months ahead of schedule, those who were given daily doses of music written just for them had brain functions that appeared to be developing better than those who weren't exposed to the music.

"We wanted to structure the day with pleasant stimuli at appropriate times: a music to accompany their awakening, a music to accompany their falling asleep, and a music to interact during the awakening phases," explains co-author Lara Lordier, a neuroscientist at the University of Geneva (UNIGE) and the University Hospitals of Geneva (HUG).

The team recruited 24 full-term infants and 39 premature newborns for the study.

Among the preterm infants, only 20 actually underwent the musical intervention, receiving eight minutes of soothing background music, bells, harp, and the Indian snake charmer's flute five times a week five times a week. Incidentally, the snake charmer's flute was the most soothing sound to newborns.

The music was designed specifically for different parts of the babies day, such as a track for waking or another for feeding.

Neither the parents, the music intervention providers nor the caregivers had any idea which newborn was receiving what treatment. Headphones were placed on all babies during the trial when they were waking or noticed to be awake, but the control group's headphones lacked music and were open to external sounds.

Using functional MRI on all three groups of children, the researchers found what they largely expected. The neural networks of children who heard the music had greater functional connectivity had a brain network more similar to that of full-term infants.

The connections between the brain's salience network were especially notable. This is a system crucial for evaluating information and then passing it on to the appropriate area for action.

In those premature infants who listened to music on a daily basis, neural activity from this region was strengthened right across the board, spreading through the auditory, sensorimotor, frontal, thalamus and precuneus networks.

Unfortunately, the same was also true in reverse. Those premature babies who did not receive music therapy had poorer functional connectivity than full-term babies, and this was most obvious in the salience networks.

"During early postnatal life, the environment of preterm infants is vastly different from that of full-term (in utero) infants, with different solicitations and sensory stimuli," the authors explain.

In the intensive care unit, they continue, children are often overwhelmed and stressed out by the sounds of doors opening and closing and the sudden ringing of alarms. These abrupt events could be using up valuable energy reserves that are crucial for brain development in preterm infants.

Calming music might be the perfect way to drown it all out.

"At birth, these babies' brains are still immature. Brain development must therefore continue in the intensive care unit, in an incubator, under very different conditions than if they were still in their mother's womb," explains Petra Hüppi, the head of the HUG Development and Growth Division, who directed this work.

"Brain immaturity, combined with a disturbing sensory environment, explains why neural networks do not develop normally."

With the participants now reaching the age of six, researchers will finally be able to test whether the cognitive benefits of NICU music have stuck with them throughout the years.

The research is published in PNAS.