The sounds babies hear during sleep have a huge impact on their brains. Here’s why.
A substantial amount of brain development occurs in response to outside stimuli
At birth, the infant brain is stocked with billions and billions of neurons, but the connections among those neurons that form the foundation of lifelong cognitive and physical processes are developed largely after birth.
In fact, although genes are the primary determinant of the prenatal structure of the brain, postnatally, it is largely the babies’ “experience” with the environment that creates the neuronal connections that will make up their brain’s many networks and systems. This propensity of the brain to develop, change, and adapt in response to external stimuli is called plasticity.
Different stimuli are important at different times
Scientists have identified periods in the very early years of life when the brain is especially sensitive to certain kinds of stimuli that help it develop specific neural networks. Those periods occur at different times for the auditory, visual, and somatosensory (perception of touch, heat, pain, body position) senses.
During each of these periods, the young brain expects and needs to be exposed to the particular input it’s seeking to shape the processes that are the focus of that critical period. Said another way, during these windows, the brain has a preference for certain stimuli over others that causes it to respond more strongly to those favored stimuli. We call that preference “tuning,” and it is this tuning that influences which subsets of neurons wire together in connections and networks.
Importantly, being exposed to the preferred stimuli during one of these windows is developmentally crucial because the absence of that exposure at the right time may not be easily correctable later in life. That’s why these are critical periods!
During the first year, the brain expects and needs supportive auditory stimuli
The first year of life is a critical period for the auditory system when the infant develops the neural connections used to acquire and process language. To do that, the infant brain focuses on sound variation in its environment, especially acoustic cues that are properties of speech, like rapid changes in timing, frequency, pitch, or duration. The infant brain analyzes all those variations to identify the ones that occur most often – which will be the sounds (phonemes) of its native language – and develop connections among the neurons that process each of those sounds.
By the end of the first year, the baby brain should have built its acoustic map, the network of connections that process all of its native language phonemes. A well-formed acoustic map increases the infants’ ability to quickly and accurately process the sounds in an incoming language stream, allowing them to begin to identify words and attach meaning to those words.
If, however, a baby’s experience during this critical period is disrupted for some reason, for instance, the baby doesn’t receive exposure to the sound variation their brain expects because of noise, or hearing loss, those maps may not develop correctly. The disrupted critical period may not only lead to fuzzy acoustic maps that negatively affect the child’s ability to learn language, but it also may cause issues with cognitive activities that build on language, such as literacy and even the organization of memories.
As a result, it is crucial that babies receive the experiences their brains need during critical periods. Here at RAPTbaby, we are doing our best to help, creating the Smarter Sleep sound machine to provide auditory input that supports the baby’s development of acoustic maps and language networks during the first year of life and beyond.