Can short-term oral fine motor training affect precision of task performance and induce cortical plasticity of the jaw muscles?

Abstract

The aim was to test the hypothesis that short-term oral sensorimotor training of the jaw muscles would increase the precision of task performance and induce neuroplastic changes in the corticomotor pathways, related to the masseter muscle. Fifteen healthy volunteers performed six series with ten trials of an oral sensorimotor task. The task was to manipulate and position a spherical chocolate candy in between the anterior teeth and split it into two equal halves. The precision of the task performance was evaluated by comparing the ratio between the two split halves. A series of "hold-and-split" tasks was also performed before and after the training. The hold force and split force along with the electromyographic (EMG) activity of jaw muscles were recorded. Motor-evoked potentials and cortical motor maps of the right masseter muscle were evoked by transcranial magnetic stimulation. There was a significant effect of series on the precision of the task performance during the short-term oral sensorimotor training (P < 0.002). The hold force during the "hold-and-split" task was significantly lower after training than before the short-term training (P = 0.011). However, there was no change in the split force and the EMG activity of the jaw muscles before and after the training. Further, there was a significant increase in the amplitude of the motor-evoked potentials (P < 0.016) and in the motor cortex map areas (P = 0.033), after the short-term oral sensorimotor training. Therefore, short-term oral sensorimotor task training increased the precision of task performance and induced signs of neuroplastic changes in the corticomotor pathways, related to the masseter muscle.

Bite or brain: Implication of sensorimotor regulation and neuroplasticity in oral rehabilitation procedures

“…The slope of the curve is interpreted as the measure of cortical excitability. Figure shows a schematic representation of the protocol implemented in these studies which demonstrate an increased performance with facilitation of MEPs and MI map areas after oral motor training paradigm . However, one may note that the relationship between excitability and the activity of the region is quite complex and the factors determining MI plasticity are not yet clear .…”

“…Several recent studies have focused on our ability to improve oral motor performance during various oral motor tasks . These studies have primarily investigated the effects of the repeated performance of the task on behavioural learning and skill acquisitions during well‐coordinated oral motor tasks.…”

“…These studies have primarily investigated the effects of the repeated performance of the task on behavioural learning and skill acquisitions during well‐coordinated oral motor tasks. These tasks have varied from simple tongue protrusion and clenching tasks to more complex tongue training and biting of chocolate candies or force control with absolute accuracy . Mainly, the training‐related changes in particularly these studies have been assessed at the behavioural level by quantifying the performance and at the cortical level by assessing the changes in motor evoked potentials (MEPs) and cortical representations in relation to the trained muscle with either TMS or other non‐invasive imaging techniques such as fMRI .…”

“…It was suggested that the applied jaw muscle training was inadequate to induce or detect cortical excitability changes in the masseter muscle cortex or neuroplasticity occurred at other levels not detected by TMS. Subsequently, when the complexity of the task was increased from a simple biting task to a more complex manipulation and split task which involves precision biting of a sugar‐coated chocolate candy into 2 equal halves; there were signs of neuroplasticity in the corticomotor pathways of the masseter muscle . Therefore, the available literature on oro‐facial motor skill acquisition (summarised in Table ) clearly demonstrates an increase in motor performance with signs of cortical neuroplasticity in healthy adults.…”

“…Several recent studies have focused on our ability to improve oral motor performance during various oral motor tasks. 82,84,[88][89][90][91][92] These studies have primarily investigated the effects of the repeated performance of the task on behavioural learning and skill acquisitions during well-coordinated oral motor tasks. These tasks have varied from simple tongue protrusion 82,83,93 and clenching tasks 94,95 to more complex tongue training 91 and biting of chocolate candies or force control with absolute accuracy.…”