Fig. 4.
B38 bursting is associated with the jaws closing on food. A: a recording of a swallowing pattern in the suspended buccal mass. B38's characteristic large-unit activity is indicated in the gray box: note that the B38 burst (gray box, 3rd trace) begins before and then overlaps the I2 protraction activity (1st trace). The jaw width, normalized to the top-to-bottom length of the jaws, is shown at bottom. The anterior jaws began to close ∼1 s after the beginning of the B38 burst and fully closed on the seaweed at the end of the B38 burst, during the protraction phase. During the retraction phase, the anterior jaws exhibited relaxation (jaw width increased) as the seaweed was pulled inward. In the example shown, the jaws did not relax fully before the subsequent swallow; this varied from swallow to swallow. B: a series of 14 swallowing patterns from 1 suspended buccal mass experiment was analyzed, and the B38 burst duration and minimum jaw width during protraction were measured. There was a strong and highly significant (P < 0.001) correlation between B38 burst duration and decreasing jaw width; i.e., longer B38 bursts were associated with more closure of the anterior jaws. We consistently observed, in experiments using the suspended buccal mass preparation, that whenever very intense B38 bursting occurred during the protraction phase, it was associated with anterior jaw closure.