Understanding infant tongue kinetics

The tongue is an active muscle - and miracle of coordination. When we drink, the tongue prepares to swallow by gathering the liquid in our mouths by cupping. Then it quickly propels the liquid back, for swallowing. All while allowing us to continue breathing.

When we eat, the tongue functions by keeping the food in our mouths, moving it under our teeth for chewing (while being mixed with saliva) and forming the food into a bolus - which is then propelled back for swallowing. Both adults and infants use a peristaltic type of motion when swallowing.

Prenatal tongue training

Our tongue's training for all this work begins in the womb. Before birth, the tongue starts out by swallowing amniotic fluid. Once baby is born, the tongue ready to play its key role in helping extract milk from mother's breast - working in coordination with the jaw and lips.

As an infant latches onto its mother's breast, the nipple-areola is drawn into the mouth, so the nipple reaches the junction of the hard-soft palate. Nicely latched, the tongue gets to work, compressing the nipple rhythmically with peristaltic motion that squeezes milk from the breast to the back of the throat, ready for swallowing. Babies naturally coordinate between suckling, swallowing and breathing.

Bottle feeding

This dynamic changes somewhat when babies are fed by bottle. The rigidity of manmade material prevents nipples from extending and molding to the shape of the baby's mouth. Peristalsis also becomes more difficult, and milk flow may occur with little effort at all.

It's good for parents to remember that infants work to get their milk when they breast feed. When it comes to bottles, milk often flows very easily, and babies can drink the same amount of milk much faster (compared with breastfeeding). It may seem like a nice way to save time, but as with many things in life, slower is often better. By choosing a bottle that works more like a breast, with a slower flow - that allows the baby to stop and pause - baby enjoys a comfortable feed, and slowly develops the appropriate signals of satiety.

The challenge of research

Most often everything works smoothly. But from time-to-time babies have difficulties swallowing. This can be due to a variety of issues, which can be quite challenging for scientists to study (and fully understand).

At the start of the Atomic Age, diagnostics were done using cineradiology (filmed x-rays). For the first time in history, people could actually witness the amazing inner workings of the mouth, and watch the tongue as it helped carry out the act of swallowing. When concerns about exposing technicians and patients to radiation began to arise, this practice was stopped. Today, ultrasound and MRI video are often used. However, even with less invasive technology or technology, researchers are still challenged to find ways to study babies as they nurse, without influencing their actions.

Tongue kinetics study

In their 2020 study, Quantitative imagining of tongue kinetics during infant feeding and adult swallowing reveals highly conserved patterns, researchers used ultrasound video to reveal the action of the tongue.

"We saw the most organized and rhythmic tongue kinetics in infants who were exclusively breastfeeding, poorer motility in those with conditions that impede normal feeding such as tongue-tie and more disorganized motility in bottle-feeding than breastfeeding," the researchers reported. "This highlights the pivotal role of tongue kinetics in suckling from the breast or sucking from a bottle."

They were also able to observe differences in tongue motility before and after treatment for infants with tongue-tie and restrictive labial frenum. And for the first time, an infant with torticollis was imaged during breastfeeding and bottle feeding. The results revealed "slightly less rhythmic suckling than typical during breastfeeding, but arrhythmic suckling during bottle feeding."

Even though their study was limited, the use of ultrasound video proved effective in gaining objective information about tongue kinetics. As more scientists use this technique, more will certainly be revealed about the workings of the tongue, so we can gain more accurate information about normal feeding and how to manage disorders.