VESTIBULAR SYSTEM DEFINED
Rocking, swaying, spinning, bouncing, carrying, and jiggling are techniques instinctively used by parents with baby to calm, soothe, and induce sleep. Why? Because of their effect on the vestibular system. Considered to be one of baby’s most highly developed senses at birth, the vestibular system is responsible for balance and motion perception. It also plays an essential role in maintaining the head and body posture.
ANATOMY OF THE VESTIBULAR SYSTEM
Located in the skull, in a small space called the vestibule, the vestibular apparatus consists of three semi-circular canals. Each canal is filled with fluid and lined with tiny hairs. When the fluid moves it stimulates the hairs and triggers a series of electrical signals which send information to the brain. The superior, horizontal, and posterior canals, as they are named, are situated in different directions or angles from one another. Thus, one canal may be stimulated more than another depending on our direction and plane of movement. This stimulation sends the signals to the brain which tell us our position in space and provide balance. The vestibule also houses the inner ear and the otolith organs. Some motion such as head tilts and linear movements are sensed by the otolith organs.
PRENATAL VESTIBULAR STIMULATION
In 1922, Minkowski identified the vestibular system as well-developed in early human fetuses. Minkowski became noted for his research and findings on fetal development. During the prenatal period, the fetus experiences a lot of moving around due to the constantly changing position within the warm amniotic fluid that cushions her from the outside world. The fetus experiences positional changes relative to gravity as well. When the mother is standing up the weight of the fetus shifts in response to gravity and when the mother is sleeping on her back the fetus moves in a different direction in response to this orientation. These are examples of the kind of passive motion stimulation the fetus receives during the prenatal period. All three canals in the vestibular system sense these changes in position and motion.
Later in the pregnancy the mother begins to feel the baby kicking and other reflexive movements, adding to the motion stimulation. Because the level of prenatal motion is particularly high, after birth the baby will probably not experience the same degree of vestibular stimulation until she starts independently walking.
POSTNATAL VESTIBULAR STIMULATION
Parents quickly learn that baby responds quite well to motion. From rocking baby to sleep to spinning in a circle with baby to thwart her fussiness, parents turn again and again to motion for inducing calm, quiet, and sleepy states of their infant. The vestibular system is stimulated with these activities and that is a familiar and welcome feeling to baby. The acquisition of motor skills that move the head and body in space offer a lot of vestibular stimulation that is self-induced. This is part of the pleasure in the movement for baby. Not only do they get the “feeling” of the movement, but they can create it for themselves whenever they want. For example, rolling across the floor moves the vestibular apparatus around and around with each roll. Another example is the skill of lifting the head up and down while in tummy time. Research suggests that these activities improve the brain and mind development.