IADR Abstract Archives
Rhythmic Masticatory Muscle Activity During Sleep in Animals and Humans
Objectives: Rhythmic masticatory muscle activity (RMMA) can occur during sleep in 60% of normal humans. RMMA is a clinical significant motor event since the occurrence of RMMA is exaggerated in patients with sleep bruxism. Experimental animals were found to exhibit various patterns of masticatory muscle activity during sleep. However, no animal models have been established for investigating neurophysiological mechanisms of RMMA. This study aimed to investigate the occurrence of RMMA in naturally sleeping animals and clarify whether experimental animals had common electromyographic, cortical and cardiac features found in humans.
Methods: Polygraphic and masseter electromyographic recordings were done in the 30 freely-moving guinea pigs and 8 normal subjects. After RMMA episodes were visually scored, burst cycle, duration and integrated activities were calculated and compared to those during chewing. Power spectral analysis was done for electroencephalogram and RR-intervals were calculated from electrocardiogram. The changes of cortical and cardiac activity were quantified in relation to the occurrence of RMMA.
Results: RMMA occurred at 6.6 ± 5.3 times/hr of NREM sleep in guinea pigs and at 1.3 ± 0.65 times/hr of sleep in humans. In animals and humans, RMMA showed common electromyographic characteristics when compared to chewing: it had longer burst duration, lower mean burst activity and larger variability of burst cycles than chewing. The occurrence of RMMA was associated with transient changes of cortical and cardiac activities in animals and humans. In addition, a significant decrease in RR-intervals preceded the onset of RMMA.
Conclusions: These results showed that RMMA during NREM sleep would be generated by the neural combinations distinct from those for chewing. In addition, RMMA in animals and humans shares common physiological features, proposing the possibility in developing the applied and basic science research perspectives in sleep bruxism research.
Methods: Polygraphic and masseter electromyographic recordings were done in the 30 freely-moving guinea pigs and 8 normal subjects. After RMMA episodes were visually scored, burst cycle, duration and integrated activities were calculated and compared to those during chewing. Power spectral analysis was done for electroencephalogram and RR-intervals were calculated from electrocardiogram. The changes of cortical and cardiac activity were quantified in relation to the occurrence of RMMA.
Results: RMMA occurred at 6.6 ± 5.3 times/hr of NREM sleep in guinea pigs and at 1.3 ± 0.65 times/hr of sleep in humans. In animals and humans, RMMA showed common electromyographic characteristics when compared to chewing: it had longer burst duration, lower mean burst activity and larger variability of burst cycles than chewing. The occurrence of RMMA was associated with transient changes of cortical and cardiac activities in animals and humans. In addition, a significant decrease in RR-intervals preceded the onset of RMMA.
Conclusions: These results showed that RMMA during NREM sleep would be generated by the neural combinations distinct from those for chewing. In addition, RMMA in animals and humans shares common physiological features, proposing the possibility in developing the applied and basic science research perspectives in sleep bruxism research.