MEG Findings of Cerebellar Activity Immediately Before Teeth Clenching

Objectives: This study used magnetoencephalography (MEG) to determine how the cerebellum is involved in intracerebral activity immediately before teeth clenching.

Methods: The subjects were five right-handed males with no history of neurological disorders. MEG recordings were obtained with a whole-head 151-channel system. A single trial consisted of maintaining clenching for 2 seconds followed by a semirandomized interval of 2-4 seconds, with 25 trials performed in a single session. Each subject performed a total of 125 trials over 5 sessions. The subjects performed 5 more sessions as a control session without teeth clenching task. Visual cues for interval and for clenching were presented to each subject. We used magnetic field tomography (MFT) to obtain a tomographic reconstruction of brain activity for each time slice of the average signal for each subject and session. Regions of interest (ROI) were defined for each subject in motor, premotor, cerebellum and visual cortices. An ROI activation curve was computed from the MFT results for each ROI. To determine the threshold, the algorithm computed a threshold amplitude value exceeding ±3SD of the integrated activation curve in the 300 msec preceding the visual cues. The difference in the peak amplitude of the cerebellum area between the base line (interval) and main session, and between the control session and main session was statistically analyzed using paired t-test.

Results: Cerebellar activations were identified in all five subjects, bilaterally in three subjects, and unilaterally in two subjects. The peak amplitudes for left and right cerebellar hemispheres in the main session were greater than those at the baseline (P<0.001). Additionally the peak amplitudes for left and right cerebellar hemispheres in the main session were greater than those in the control session (P<0.01).

Conclusion: Our findings suggest that the cerebellum is part of the signal pathway immediately before teeth clenching.