Neuroplastic changes in the sensorimotor cortex associated with orthodontic tooth movement in rats

Area of Science:

• Neuroscience
• Oral Biology
• Motor Control

Background:

• Orthodontic tooth movement (OTM) alters oral sensory input and chewing patterns.
• Understanding the brain's response to OTM is crucial for managing associated discomfort and functional changes.

Purpose of the Study:

• To investigate neuroplastic changes in the rat's primary motor cortex (face-M1) and somatosensory cortex (face-S1) during OTM.
• To analyze changes in motor representations of specific jaw muscles, including the anterior digastric (AD), masseter, buccinator, and genioglossus (GG).

Main Methods:

• Utilized intracortical microstimulation (ICMS) and electromyographic (EMG) recordings in Sprague-Dawley rats.
• Compared experimental (OTM induced), sham, and naive groups over 28 days.
• Analyzed changes in the number of ICMS-responsive sites and response onset latencies.

Main Results:

• Significant neuroplastic changes were observed in the number of ICMS-responsive sites for left/right anterior digastric (LAD/RAD) and genioglossus (GG) muscles in both face-M1 and face-S1.
• Increased ICMS sites simultaneously evoking responses in combinations of LAD, RAD, and GG muscles were noted in face-M1.
• No significant differences in the onset latencies of ICMS-evoked responses were found between groups or cortical areas.

Conclusions:

• OTM induces significant neuroplastic adaptations in the sensorimotor cortex related to jaw muscle control.
• These changes likely represent adaptive responses to the altered oral environment created by orthodontic forces.
• The findings provide insights into the neural mechanisms underlying adaptation to OTM.