Brain regions activated during the mandibular movement were evaluated by fMRI. Eight healthy right-handed volunteers as examinees were included in this study. Echo planar imaging of fMRI were obtained with the gradient echo sequence using 1.5 T MR scanner. All examinees were subjected to complete six tasks of mandibular movement ; simple mouth opening and closing movement, protrusive movement, retrusive movement, right lateral movement, left lateral movement, and imaginary mouth opening and closing movement. The stimulation paradigm consisted of 7 cycles of scans. Each cycle consisted of 10 repeated imagings during “on” and “off” periods of each 5 seconds.
The head of examinee in the supine position was fixed, to minimize involuntary motions during all functional measurements, before motions of the head were measured.
The following conclusions were obtained.
1. The examinations were achieved with minimal artifacts caused by motions of the head.
2. The region of motor cortex activation by the mandibular movements approximately agreed with those reported by electrophysiological methods in animals, such as cats and monkeys.
3. Activated area of motor cortex and the supplementary motor area were further extended according to the move complex mandibular movements.
4. Possible involvement of the parietal association area was indicated in the lateral movements.
5. Activation of the motor speech area was observed during lateral mandibular movement. Possibility of the involvement of the Broca's area was indicated in mandibular movement.
It was thus concluded that fMRI may be useful to analyze the brain regions activated by mandibular movement.