White-Noise and the Developing Brain

Usually, we think of preventive medicine as a first-person experience, e.g. what we can do to keep ourselves healthy. But preventive medicine includes steps to keep our families healthy as well, as in the case of an elderly relative, or a newborn baby. My first postdoc stint was in a developmental neuroscience lab at UCSF, where many talented researchers spent years answering questions like, "How do different types of environmental noise affect the development of the auditory system?". So when a friend of mine sent me a message the other day, asking about using a white-noise generator to stop her crying, colicky baby, some red flags immediately went off in my head. Because I've been asked this question several times over the past few months, I decided to post my take here.

There's been a lot of anecdotal evidence that white-noise calms a crying baby. In fact, some parents swear by the method. But this is a clear case where the science disproves the hype. In 2003, our lab at UCSF published a study in Science Magazine with a striking finding. The auditory system of newborn rat pups, which normally progresses like clockwork, was under-developed after the pups were exposed to white noise compared to animals raised in normal conditions. But why would white noise cause a problem with the development of the brain?

First, let's look at what happens to the auditory system during normal development. When rats are born, the area of the brain responsible for making sense of sounds, the auditory cortex, undergoes constant changes. Scientists refer to this phenomenon as brain plasticity. Newborns are unique because brain plasticity occurs just by passive exposure to sounds during a very well-defined time in development called the "critical period", which lasts through several postnatal days in rats. A correlate in humans might be the fact that children learn new languages just by being exposed to sounds, while adults have to spend hours studying, memorizing, and practicing. This developmental period is a crucial time for a newborn, where the brain "sets" itself to efficiently process its native language.

When white-noise was played for the newborn rats, the lab found that the "critical period" remained open indefinitely, which means there was a delay in normal brain development. For this reason, members of the lab were against using white-noise generators on newborn babies. Theories suggest that the white-noise might interfere with a newborn's ability to grasp its native language, leading to progressive developmental problems.

Even if the results found in rats did not directly carry over to humans, I really feel that you just shouldn't screw with Mother Nature when it comes to brain development. I'm not a parent, and I can only imagine the empathy, or even frustration, that ensue when a baby is crying hours on end. But using white-noise generators just doesn't seem like the best answer. Our brains evolved to process biologically- and socially-relevant sounds, and exposing newborns to extremely unnatural sounds seems like an needless gamble.