Fig. 14. (A,B) Schematic representation of neural and muscular activations during biting and swallowing cycles. Extracellular recordings from nerve and muscle in intact, behaving animals were scanned from several different sources. Simultaneous recording from BN2 and RN were taken from Morton and Chiel (Morton and Chiel, 1993a). Simultaneous recordings from BN1, BN2 and BN3 were taken from unpublished observations (D. W. Morton and H. J. Chiel). Simultaneous recordings from I2 and from BN2 were taken from Hurwitz et al. (Hurwitz et al., 1996). Extracellular recordings from I5 (ARC) were taken from Cropper et al. (Cropper et al., 1990b), and were aligned with BN3 activity (which carries the axons of the B15/B16 motor neurons). Recordings from I10 (which are representative of activity in 17, I8, I9 and I10) were taken from Evans et al. (Evans et al., 1996). The lengths of the scanned recordings were scaled relative to one another using the duration of the opening of the jaws to the closing of the jaws during a bite, and aligned by peak protraction. Boxes were then drawn around the resulting extracellular recordings, providing a schematic representation of the relative sizes of the extracellular units and their timing relative to one another. The data in the swallowing part of the figure are based on fig. 20 of Neustadter et al. (Neustadter et al., 2002b). (C) Schematic representation of roles of motor neurons and multi-action neuron B4/B5 in controlling the transition from biting to swallowing. During biting, activity in the B4/B5 neurons is reduced [(Warman and Chiel, 1995); B4/B5 are shaded]. During swallowing, activity in the B4/B5 neurons increases (Warman and Chiel, 1995), inhibiting the onset of activity in the motor neurons for the I1/I3/jaw complex, B10, B6, B3 and B9 (Gardner, 1993).