Rock-n-roll or rock-a-bye? When a baby’s musical tastes form.
Although your newborn’s central nervous system has undergone remarkable changes during the nine months before birth, she still has a way to go in terms of brain development once she enters the world. In fact, a newborn’s brain is still very small—only one quarter the size of an adult’s.
The brain grows very differently from the rest of the body. Rather than new cells forming, the neurons your baby is born with grow larger and sprout branches called axons and dendrites. Each neuron’s cell body serves as the control center, while the dendrites receive incoming signals from other neurons and the axons relay outgoing signals. As this messaging network is forming, a process called myelination is taking place, in which a dense, fatty substance coats the axons, allowing signals to pass between neurons with greater speed. It’s the expansion of this elaborate network of neurons that accounts for the brain’s growth.
Here’s a look at the ways in which you’ll see this growth come to life in your baby’s development.
During the first three months, you’ll notice your baby’s powers of auditory recognition gradually improving. This progress happens along with significant growth in the hippocampus, the region of the brain associated with recognition memory. Where initially your baby’s reactions to sounds were largely reflexive—startling in reaction to a loud noise, being soothed by the sound of your voice—by 3 months, she’s beginning to recognize and store a growing library of sounds. She’s able to make finer distinctions between scary, pleasant, and unfamiliar sounds, for instance, and to react in more nuanced ways. Toward the end of this period, you’ll probably notice her paying more attention to music, and she may even find a way to convey to you that she likes certain types of music more than others.
Your newborn’s cerebellum—the region of her brain responsible for movement, coordination, and balance—triples in size during the first year, bringing about rapid advances in her motor abilities. Her earliest movements are reflexive, as opposed to deliberate, coming in response to certain stimuli and generally helping your baby get her needs met during her earliest days, before she can communicate them to you. Every movement she makes exercises certain neuronal connections, which stimulates those neurons to form even more connections. This activity, in turn, strengthens her motor functions and gradually allows for more coordinated, complex, and deliberate movements. During the course of the first three months, you can observe changes in your baby’s gross motor skill development; for example, when you lay her on her stomach, she’ll gradually become able to lift her head. Eventually she’ll turn it from side to side, as well. She’ll also grow more adept at fine motor movements, such as batting a toy she’s interested in to bring it closer to her and loosely grasping an object with her hand.
It will be months before the regions in your baby’s brain responsible for language comprehension and speech production are developed enough to allow her to communicate in words, but she can convey a great deal through the varying sounds of her cries. And soon you’ll begin to recognize her hungry cry, her angry cry, her frightened cry, and her wail of discomfort when she needs a diaper change. Likewise, her gurgles and coos will let you know when she’s happy.
Through signals received in the auditory cortex, she’s already beginning to distinguish between different sounds of speech. Listening is the first step to picking up language, and eventually the neurons in the auditory cortex will start to relay those incoming signals to other regions of the brain, including Wernicke’s area in the left temporal lobe (where word recognition and language comprehension take place) and Broca’s area in the left frontal lobe (where the movements necessary for forming speech are coordinated).
Your baby came into the world completely dependent on you to meet her most basic needs (which you’ll do now and during much of her infancy). As a matter of survival, her brain is more fully developed in areas that enable her to connect with you, her parents. For instance, at birth, your baby’s visual cortex is just mature enough to allow her to focus on objects 8 to 15 inches away, the distance to your face when she’s feeding. Her distance vision improves in these early months, and more remarkably, she’ll soon be able to look at your eyes and follow your gaze to see what you’re looking at. This ability (referred to as shared or joint attention) involves an area of the prefrontal cortex associated with complex cognitive and social behaviors. It’s considered a vital social skill and a cornerstone of human cognitive development.