Functional magnetic resonance imaging of human jaw movements.

This study used functional magnetic resonance images (fMRI) to examine brain activity during clenching, gum chewing, and tapping tasks. It has been considered difficult to obtain sufficient fMRI data during jaw movement because the head motion associated with the jaw movements creates artifacts on the images. To avoid these artifacts, larger pixels were used, thus allowing some head motion of the subjects, and data from subjects where the heads were evaluated to have moved more than 0.5 mm were discarded. Further, all pixels obtained by fMRI were evaluated and pixels positively synchronized with the task, which were considered to show brain activity, were selected. Sufficient fMRI data was obtained from 30 experiments, 10 sets for each task. During the clenching and tapping tasks, the activated pixels were in the sensory, motor and pre-motor cortexes, and in the sensory and motor cortexes but not in the pre-motor cortex during the gum chewing task. There appears to be no significant differences between right- and left-hemispheres. It is conceivable that there are differences between voluntary jaw movements (clenching and tapping tasks) and mastication (gum chewing task) concerning the control of jaw movements.