Shh! Baby's Asleep...And He's Listening

By R.T. Ripley


The old saying, “Little pitchers have big ears,” has long referred to our awareness that infants and children are listening far more to their surroundings than we often give them credit for. But new research surprisingly shows that not only is a baby’s brain development affected by what he hears when he is awake, the baby’s brain development is changing in response to what he hears while he is sleeping.

Sleeping infants and arguing voices

Researchers at the University of Oregon most significantly found that the brains of sleeping infants change the way they are developing when they hear arguing noises. By using noninvasive MRI technology and headphones with 20 sleeping infants, a voice then uttered a nonsense series of words in four different tones: neutral, happy, somewhat angry, and very angry. The result was an astounding new awareness of the complexity and mystery of childhood development. All 20 of the sleeping babies who were monitored showed highly lit up areas of the brain that involve memory, stress adaptation, and emotion regulation when the angriest tones were heard. The bottom line: Their little brains light up when they hear angry tones, and they don’t have to be awake to hear you.

How did this work? The MRI machine simply shows an area of the brain to “light up” when it is activated. This occurs because of increased blood flow to the area. An activated area of the brain then processes information based on the function of that area. Different areas process the five senses, muscle movement, biological reflexes such as hunger and thirst, and moods such as anger and stress. Since a baby’s brain is so malleable, processing stressful stimuli easily affects sleeping patterns, blood pressure, irritability, and crying responses. 

Newborn stress and brain development

Doctors have long known (and many parents) that babies hear sounds in utero. It has also been known that babies, children, and adults are affected by surrounding sounds which may be positive or negative. Previous studies have showed in animals, including humans, that several areas of the brain develop poorly when there is stress in early life. And we have known that the sound of the human voice has the power to both soothe as well as to agitate. The most negative of human voices are those that are argumentative, and the very sound of them affect the way an infant’s brain develops and processes his earliest stages of stress. 

However, these new findings are significantly different in that they demonstrate changes and adaptive mechanisms going to work in the presence of argumentative noises even when the baby is sound asleep. Pediatricians are concerned that when babies should be developing areas of cognition, sensory perception, and motor development, negative sounds such as arguing voices force their brains development to gear itself to stress adaptation too early in their little lives. With the brain areas that cope with stress not yet wired for such adaptation, physical and emotional problems in the infants result instead. 

In addition to the study showing the developing changes in response to arguing sounds during sleep, researchers asked mothers to state whether the sleeping babies’ environments were typically quiet or typically full of loud noises. The babies whose mothers reported parental conflict during sleeping hours were more agitated, colicky, and sleepless. 

Researchers believe that arguing within earshot of your baby, sleeping or not, sensitizes the infant’s brain to stress. Since early life experiences clearly influence a person’s response to events later in life, the implications of these new studies are far-reaching. We know that babies’ brains are highly responsive, which allows them to quickly learn how to adjust to the environments and people around them. This is usually a positive sign of human development, but these highly responsive brains are also affected by abuse and mistreatment, which can significantly damage babies’ brain development.

Nurseries: Quiet zones

Besides the sounds of quarreling voices, there are other noises that adversely affect infants and their brain development. Infants who have been exposed to high levels of noise because of hospital equipment such as incubators have been found to suffer hearing loss and problems with sleep and stress. Environmental sources of noise such as rock concerts, boom boxes in cars, and airport jet traffic add to occupational sources of noise with negative results in infants. 

Pediatricians recommend that nurseries remain essentially “quiet zones” in the home or areas with soothing, pleasant sounds. There are simple strategies parents can take to reduce nursery noise such as wearing soft shoes on hard floors, carefully closing drawers and doors, and making other family members respect the nursery as a quiet zone. Some doctors even suggest signs such as “Shhh, baby is sleeping,” on doors that lead to the nursery when there are visitors present in the home. 

 With all the excitement that comes with bringing an infant home, there is also the stress. And one thing parents forget to check along with the long list of items they need to ensure when baby comes home is NOISE. Unmoderated noise is dangerous in an infant whose delicate hearing and brain is developing. 

Changing neonatal units

In the last year, hospitals are responding to the growing awareness that the noise in neonatal units can actually be damaging to infants. In neonatal intensive care units (NICUs), for example, babies in large rooms side-by-side are exposed to the sound of alarms that sound when an infant’s vital signs signal danger. In an NICU, alarms may frequently occur. As a result, Woman’s Hospital in Baton Rouge redesigned their NICUs so that infants are in single patient rooms where they are not exposed to the almost continual sounds of alarms, voices, footsteps, and computer clicking that occurs in non-private group rooms. 

As Dr. Steven Spedale, President of Infamedics in Baton Rouge explains, “This has all emerged from a concept known as ‘Family-Centered Care’ in which parents are included as part of the care team. The design of the NICU at Woman’s was the result of multiple site visits to other NICUs as well as multiple discussions amongst the existing care team (medical, nursing, respiratory therapy, ancillary staff such as Occupational/Physical Therapy, social services and administration). It has been a major step for many institutions to go this route because of the expense of putting one baby in one room. The “old way” for taking care of NICU patients had been to have them in open bays (i.e. four to six patients in a large open room). Obviously, this was noisy, had no privacy for parents, had some concerns for infection control, and didn’t help with developmental care.”

 Additionally, “Nurses at Woman’s Hospital’s NICU may write ‘auditory comfort given’ in charts of infants who undergo painful procedures, which may consist of soft lullabies or soothing voices,” states Tiffany Saloom, RN. “We make the infants’ rooms as quiet and soothing as possible, decreasing the stimulation that is often so important especially with babies who weigh only one to two pounds. We also alternate the lighting cycle, and unless there is a life-threatening code situation, we do not chart inside the baby’s room or work on computers,” states Ms. Saloom. 

Redesigning the neonatal units to reflect quieter, less stimulating environments has been the result of pediatricians conducting research and getting involved in the planning of the architecture. Baton Rouge pediatrician Dr. Alston Dunbar III has researched tirelessly to implement construction of neonatal units based on scientific research, including his own.

Newborn hearing development

From birth to six months, newborns are developing auditory discrimination, or the difference between sounds. And those sound differences are changing the way a baby reacts to stimuli, stress, and sleep. 

An infant doesn’t need to understand what a parent is saying for the tone to come through loud and clear.  The message for quarreling parents is clear: Shhhhh. Your babies are asleep. And they’re listening.

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05 Aug 2016

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