NOVEMBER 2024
Neuroscience in the Nursery
We’ve written about white noise before, highlighting its potential risks in early childhood due to its lack of the acoustic variation young brains rely on to construct language maps. It turns out that adults, too, may want to think twice about white noise, as recent research suggests exposure to white noise may be associated with brain changes related to tinnitus, an auditory condition affecting both adults and children.
Today’s Topic: White Noise and Tinnitus
What is Tinnitus?
Tinnitus is characterized by the perception of sounds that do not exist in the external environment. Those phantom sounds can vary widely, presenting as ringing, roaring, buzzing, and clicking, and can be high or low-pitched and constant or intermittent. Tinnitus is quite common, affecting anywhere from 10 to 30% of the US population, with prevalence increasing with age. While many find it mildly annoying, for others, it can be highly debilitating. The causes of tinnitus are not yet fully understood, but excessive noise exposure, hearing loss, ear and nerve disease, high blood pressure, head injuries,genetics and drug and chemical exposure are all believed to be potential contributing factors.
Where Does White Noise Enter the Picture?
To understand the potential link between white noise and tinnitus, it is important to recognize how sound – and external stimuli in general – affect the brain. At birth, the brain consists of generally unconnected neurons. Over the first few years of life, millions of synaptic connections must form through interaction with the environment to create the networks responsible for basic and higher-level cognitive, physical, and emotional processes. For example, a newborn’s vision is blurry at birth, but as they are exposed to faces, light, and movement, their visual cortex strengthens its connections, allowing the baby to recognize shapes, colors, and patterns. Similarly, when a baby is learning how to reach for a toy, connections in the motor cortex and cerebellum strengthen, facilitating coordinated movement. Rolling over, sitting up, crawling, and walking are all milestones that occur as synaptic connections are repeatedly activated and refined through trial and error. And hearing variation in sounds helps babies recognize – and build connections to process – the sounds of language.
Scientists once believed that brain wiring only occurred during early childhood, but research over the past few decades has shown that the brain continues to rewire and reshape itself in response to internal and external stimuli and experiences throughout life. However, establishing new connections in older brains requires more time, effort, and resources compared to the rapid adaptability seen in newborns and young children. Importantly, this continuous reshaping does not always move in a positive direction, which is where the concerns arise regarding white noise, particularly given the frequency with which many adults use it for sleep or as a tinnitus therapy.
Efficient auditory processing relies on the specialization of individual cells, allowing them to focus on relevant signals and avoid being overwhelmed by trying to attend to every sound in the environment. This specialization enhances response accuracy and speed while conserving energy, as not every cell needs to respond to every auditory stimulus. To achieve this specialization, the brain must be exposed to structured, information-rich signals that vary in distinct features such as frequency, pitch, tone, and rhythm with clear patterns or variations. Such signals help shape the auditory system to process language and other complex sounds effectively. For instance, one of the brain’s early developmental goals is tonotopic mapping, the process by which individual cells become specialized as to the frequencies to which they will respond and are arranged in the cochlear (where sounds first enter via the ear) and auditory cortex from very low frequencies to very high. This specialization and organization, which occurs as the neurons are repeatedly exposed to different frequencies of sound, help the brain efficiently distinguish different musical notes or speech sounds and establish the neuronal connections necessary to process them.
Why White Noise May Be Problematic
White noise, which comprises all frequencies played at the same intensity, lacks the information-rich qualities of natural sounds. Instead, it is random and unstructured, making it difficult for auditory cells to respond selectively. Prolonged exposure to white noise could lead to a loss of cell specialization and a reduction in the inhibitory control needed to prevent cell responses to irrelevant sounds. This, in turn, can result in increased spontaneous firing rates and excessive neural synchrony (where many neurons fire simultaneously but in an undifferentiated, non-specific manner), reducing the brain’s ability to differentiate between different sources of information and leading to reactions to sounds that are not actually present – one of the hallmarks of tinnitus. Indeed, animal studies have demonstrated that exposure to white noise can induce brain changes associated with tinnitus, even at levels that do not cause hearing loss, raising concerns that the use of white noise may potentially contribute to the development or worsening of tinnitus.
Point / Counterpoint
Some researchers argue that the concerns about white noise and tinnitus are overblown. They note that animal studies may not directly translate to human experience and point to decades of clinical practice where tinnitus patients have been advised to use white noise to mask phantom sounds. Additionally, they highlight the absence of reported cases linking white noise to harm.
However, the absence of clinical evidence does not confirm that white noise is safe. The brain changes caused by white noise may be subtle and take time to manifest as symptoms, which could mean the connection between white noise and tinnitus has simply been overlooked.
The Takeaway
Our advice regarding white noise for adults remains the same as it is for children: why take on the potential risk? There are many alternative solutions for masking noise (whether as a sleep aid or to alleviate tinnitus) that contain the structured signals that white noise lacks – music and spoken word tracks, for instance. Why not choose one of those?
A Source for More #1
This article, from a team that includes Dr. Michael Merzenich, one of the world’s leading authorities on brain plasticity, provides a clear explanation of how white noise might cause maladaptive changes in the adult brain and why adults might want to reconsider its use.
A Source for More #2
If you’re interested in learning more about tinnitus, who it affects and how it’s treated, you might want to take a look at this article. Though a little dated, it reflects the results of a very large population survey so gives a flavor for how pervasive the condition was 15 years ago. One might expect tinnitus to be even more prevalent today, given the increased use of earbuds and headphones at high volumes, higher general stress levels and an aging population which is why it’s worth getting educated on what you can do to prevent it.
RAPTbaby Recommendation: A Song That Soothes
In these fractious times, the calming power of music may be just what we all need. Here’s one of our favorites: Israel “Iz” Kamakawiwoʻole’s mash-up of “Somewhere Over the Rainbow” and “What a Wonderful World.”