Brain activities related to jaw movement were investigated to clarify the relationship between mandibular motion and magnetic fields of the primary sensorimotor cortex using a magnetoencephalography (MEG) system. Two adult volunteers were asked to conduct movements, that is, jaw opening and jaw closing including bilateral or unilateral biting, lateral jaw movement, tongue protrusion, and forefinger abductive movement. A total of 100 trials were performed for each session.
The results were as follows:
1. Readiness fields related to jaw opening, unilateral or bilateral biting as jaw closing, lateral jaw movement, tongue protrusion, and unilateral forefinger abduction bilaterally appeared in the primary sensorimotor cortices.
2. Motor fields related to opening and tongue protrusion appeared in the bilateral primary sensorimotor cortices, while motor fields related to lateral jaw movement and unilateral forefinger abduction dominantly appeared in the contralateral primary sensorimotor cortex to the working side.
3. Source analysis of readiness and motor fields related jaw, tongue, and finger movements indicated anteriorly directed 2 dipoles in the bilateral primary sensorimotor cortices.
From these findings, it was concluded that bilateral primary motor cortices play a role in preparing jaw movement regardless of the type of movement, while contralateral primary motor cortex to the working side dominantly controls asymmetrical jaw movement.
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