Abstract
The purpose of the present study was to observe and investigate the coordination among tongue and jaw movement, perioral muscle activity, and sucking pressure during nutritive sucking in infants.
The subjects comprised 25 healthy infants, born normally at full-term pregnancy. The mean age was 13.0±4.5 wks after birth. A feeding bottle equipped with CCD videocamera and pressure sensor was devised to show the inside of the baby's mouth and record the sucking pressure. Muscle activity was examined by unilateral surface electromyography from the temporalis (TM), masseter (MM), orbicularis oris (OM) and suprahyoid muscles (SM). Mandible and tongue movement, muscle activity and sucking waves during the intake of the glucose solution (10%) were recorded simultaneously on video tape.
The results are as follows:
1) The tongue movements were peristaltic. When the infant began to suck, the tip of the tongue rose. The central part of the tongue then became a bell shaped bulge which moved backward toward the root of the tongue. At the final stage, the tongue receded quickly and reversed forward; i. e. the sucking cycle.
2) High correlation was recognized among tongue movement, sucking pressure and jaw movement. While the mandible pulled up until the bell shape appeared in the tongue and the nipple diameter was reduced, and sucking pressure was positive. After mouth closure the bell shape on the tongue moved backward, and the pressure was negative; the jaw also moved backward and the mouth opened.
3) The TM and MM were most active when the sucking pressure became positive and the mandible was closing. The OM and SM were active in both the positive and negative sucking phases, OM activity being most intense in the positive pressure phase, SM showing highest activity in the negative pressure phase.
4) Regarding muscle activity relating to sucking, the SM was the most active, followed by OM, MM and TM.
It was concluded that tongue movement, perioral muscle activity and sucking pressure are highly coordinated during nutritive sucking in all infants.
