JAW MOVEMENT KINEMATICS AND JAW MUSCLE (EMG) ACTIVITY DURING DRINKINGIN THE PIGEON (COLUMBA-LIVIA)

Movements of the maxilla and mandible were recorded during drinking in the head-fixed pigeon and correlated with electromyographic activity in representative jaw muscle groups. During drinking, each jaw exhibit s opening and closing movements along both the dorso-ventral and rostr o-caudal axes which may be linked with or independent of each other. A ll subjects showed small but systematic increases in cycle duration ov er the course of individual drinking bouts. Cyclic jaw movements durin g drinking were correlated with nearly synchronous activity in the pro tractor (levator) of the upper jaw and in several jaw closer muscles, as well as with alternating activity in tongue protractor and retracto r muscles. No EMG activity was ever recorded in the lower jaw opener m uscle, suggesting that lower jaw opening in this preparation is produc ed, indirectly, by the contraction of other muscles. The results clari fy the contribution of the individual jaws to the generation of gape v ariations during drinking in this species.