Unbalanced Occlusion Modifies the Pattern of Brain Activity During Execution of a Finger to Thumb Motor Task.

Maria Paola Tramonti Fantozzi,Daniele Chiesa,Barbara Castagna,Carlo Tessa,Diego Manzoni,Ugo Faraguna,Giulio Ravenna,Stefano Diciotti,Massimo Barresi,Vincenzo De Cicco,Claudio Vignali

doi:10.3389/fnins.2019.00499

Abstract

In order to assess possible influences of occlusion on motor performance, we studied by functional magnetic resonance imaging (fMRI) the changes in the blood oxygenation level dependent (BOLD) signal induced at brain level by a finger to thumb motor task in a population of subjects characterized by an asymmetric activation of jaw muscles during clenching (malocclusion). In these subjects, appropriate occlusal correction by an oral orthotic (bite) reduced the masticatory asymmetry. The finger to thumb task was performed while the subject’s dental arches were touching, in two conditions: (a) with the teeth in direct contact (Bite OFF) and (b) with the bite interposed between the arches (Bite ON). Both conditions required only a very slight activation of masticatory muscles. Maps of the BOLD signal recorded during the movement were contrasted with the resting condition (activation maps). Between conditions comparison of the activation maps (Bite OFF/Bite ON) showed that, in Bite OFF, the BOLD signal was significantly higher in the trigeminal sensorimotor region, the premotor cortex, the cerebellum, the inferior temporal and occipital cortex, the calcarine cortex, the precuneus on both sides, as well as in the right posterior cingulate cortex. These data are consistent with the hypothesis that malocclusion makes movement performance more difficult, leading to a stronger activation of (a) sensorimotor areas not dealing with the control of the involved body part, (b) regions planning the motor sequence, and (c) the cerebellum, which is essential in motor coordination. Moreover, the findings of a higher activation of temporo-occipital cortex and precuneus/cingulus, respectively, suggest that, during malocclusion, the movement occurs with an increased visual imagery activity, and requires a stronger attentive effort.

Highlights

There is a debate as to whether trigeminal sensorimotor signals may affect posture and movement
The present data indicate that the increase in cerebral blood flow elicited by a motor task involving the fingers can be influenced by the occlusal condition
When subjects wore a bite that balanced the occlusion, the increase in blood oxygenation level dependent (BOLD) signal elicited by finger movements was significantly reduced at the level of frontoparietal sensorimotor regions, cerebellum, temporo-occipital, and midline posterior regions

Summary

Introduction

There is a debate as to whether trigeminal sensorimotor signals may affect posture and movement. Postural control seems to be influenced by the occlusal condition (Ohlendorf et al, 2014; Julià-Sánchez et al, 2015; see, Perinetti, 2006), temporomandibular joint (TMJ) disorders (Chaves et al, 2014) and orofacial motor activity (Kushiro and Goto, 2011; Ringhof et al, 2015). These data are consistent with the observation that sensorimotor signals elicited during isometric clenching are very effective in increasing the excitability of spinal motoneurons (Miyahara et al, 1996). The BOLD signal increased in the prefrontal, temporal, parietal, and occipital lobes, as well as in the cerebellar network (Lotze et al, 2012)

Methods

Results

Conclusion