Abstract
The effect of altered occlusal force on masticatory-related neuromuscular control, which projects from the anterior part of the cortical masticatory area (A-CMA), during growth remains unclear. This study sought to evaluate the effect of occlusal hypofunction on neuromuscular development of jaw muscle activities and cortically-induced rhythmic jaw movements (RJMs) in growing rats. Sixty-four 2-week-old male albino Wistar rats were divided into the control (fed normal diet) and experimental (fed soft diet) groups soon after weaning. Electromyographic activity was recorded at 5, 7, 9, and 11 weeks from the right masseter and anterior digastric along with RJMs. We found a significantly longer onset latency and smaller peak-to-peak amplitude in the experimental group than that in the control group. The RJMs showed an increase in gape size and lateral excursion until up to 9 weeks in both groups. However, both the average gape size and lateral excursion were significantly smaller in the experimental group than that in the control group after 9 weeks. The jaw movement pattern also showed a significant decrease at the maximum opening period in the experimental group. Our findings indicate that inadequate occlusal function during growth alters neuromuscular control of masticatory behaviors and impairs the pattern of RJMs.
Highlights
The effect of altered occlusal force on masticatory-related neuromuscular control, which projects from the anterior part of the cortical masticatory area (A-CMA), during growth remains unclear
We have previously shown that an altered occlusal behavior by long-term feeding of soft diet affects the neuromuscular control of the jaw muscles induced by the P-CMA19
Typical EMG activity with jaw movement patterns during stimulation are shown in Fig. 1, and the inset enlargement of both EMG activity and jaw movement trajectories of the two groups are shown in Supp
Summary
The effect of altered occlusal force on masticatory-related neuromuscular control, which projects from the anterior part of the cortical masticatory area (A-CMA), during growth remains unclear. Our findings indicate that inadequate occlusal function during growth alters neuromuscular control of masticatory behaviors and impairs the pattern of RJMs. Locomotor activities, including walking, breathing, chewing, and swallowing, are guided under the full/partial control of brainstem neural circuits known as central pattern generators (CPGs) influenced by cortical motor outputs from higher brain areas. Motor outputs from cortical areas influence rhythmic motor behaviors in various parts of the body, including the orofacial region[1] These behaviors are important for motor activity and significantly contribute to sensory inputs as well as the structural and functional development of the brain. A study on rats has suggested that unloading activity of the hindlimb strongly modifies both motor behavior and skilled motor activity, producing alterations in locomotor a ctivity[4] Taken together, these results suggest that cortical mechanisms including sensorimotor integration play a critical role in the generation and control of locomotor behavior. A recent study has reported that a soft diet can lead to a variety of unfavorable health outcomes including changes in systemic, Scientific Reports | (2021) 11:7175
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