Craniofacial Muscles

122 B.J. Sessle et al.
Fig. 7.3 An example of a face MI neuron that fi red rhythmically during the jaw-opening phase of
chewing by an awake monkey. ( a ) Neuron’s activity in relation to a single masticatory trial. ( b )
Neuron’s activity in relation to 11 masticatory trials aligned to the point of maximum jaw closing
( vertical line in the fi gure) during the food-preparatory phase. The traces showing movements of the
mandible and the EMG activity of the masseter, genioglossus, and anterior digastric muscles are
derived from averaged data. ( c ) A neuron’s phasic activity in relation to 33 rhythmic chewing cycles
aligned to the point of maximum jaw opening ( vertical line in the fi gure) during the rhythmic-chewing
phase, but shown in prolonged time scale. ( d ) Neuron’s swallow-related activity by aligning seven
chewing trials to the point of the GG-de fi ned swallow onset (the vertical line shown in ( d )). Inset :
the orofacial mechanoreceptive fi eld of the neuron and the tongue movement direction ( arrow )
evoked by ICMS (threshold T for movement, 30 m A) applied at the neuronal recording (adapted
from Yao et al. 2002 ). (Reprinted with permission from The American Physiological Society)
swallowing vs. clenching or tapping the teeth together), in part re fl ecting whether the
movement does or does not involve evoked sensory inputs that project to and activate
the cortical area(s). Intracortical microstimulation (ICMS) and neural recording
studies in monkeys and subprimates (e.g., rats) have revealed consistent fi ndings
(Murray et al. 2001 ; Yao et al. 2002 ; Avivi-Arber et al. 2010 ; Figs. 7.3 and 7.4 ).
Thus, ICMS can evoke speci fi c movements from speci fi c cortical sites, and the