Meta‐analysis of brain mechanisms of chewing and clenching movements

Abstract

Functional magnetic resonance imaging (fMRI) is widely used for investigating brain activation patterns associated with chewing and clenching movements. Whether studies consistently identify similar brain loci engaged in these movements remains unknown. We investigated the consistency with which specific brain loci were reported to be activated during teeth-occluding movements, using the activation likelihood estimation (ALE) meta-analysis. Twenty fMRI studies that used fMRI to investigate brain activation during a chewing or clenching task in healthy participants were included. Data from the selected studies were pooled, and ALE methods were used to estimate the likelihood of finding a locus associated with the movements. We found that (i) The bilateral primary motor cortex/supplementary motor area/thalamus, the right primary somatosensory cortex (S1)/secondary somatosensory cortex and the posterior cerebellum (lobule VI) have been identified as reliable loci that show consistently activation when teeth occlude. (ii) The right S1 showed a significant likelihood of activation associated with both chewing and clenching, while the left S1 showed a greater likelihood of activation in chewing than in clenching. (iii) Both younger and older participants showed a significant likelihood of activation in the cerebellum. No significant cluster was identified in the contrast analysis. The fMRI studies reliably identified the sensorimotor cortex, the thalamus and the cerebellum as brain loci associated with chewing and clenching and illustrated a differential activation pattern between chewing and clenching. These findings support the use of fMRI as a potential tool for assessing brain activation patterns related to oral sensorimotor functions in humans.

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“…These findings have been further replicated in different studies . By evaluating multiple studies of the same kind, a meta‐analysis confirmed the previous hypothesis that the primary motor and somatosensory cortices are the key regions where activation corresponds to the chewing movement . The findings also corroborate evidence from animal models, which revealed that activity of the masticatory motor area and sensory input from the facial somatosensory area are necessary for mastication …”

“…Earlier research began by asking the “where” question, as shown in the pioneering work by Onozuka et al, who identified the activation of multiple brain regions, primarily the sensorimotor area, corresponding to the chewing movement. These findings have been further replicated in different studies . By evaluating multiple studies of the same kind, a meta‐analysis confirmed the previous hypothesis that the primary motor and somatosensory cortices are the key regions where activation corresponds to the chewing movement .…”

“…Co‐activation of loci found in neuroimaging studies of mastication and dental fear/anxiety, based on a previously published systematic review and meta‐analysis that combined (A) 13 studies of chewing tasks, (B) 7 studies of clenching tasks and (C) 7 studies of dental fear/anxiety tasks . The percentage of co‐activation across all the included studies is also shown in the association matrix in the right panels.…”

“…Visualisation of the loci of brain activation related to oral sensorimotor functions, based on the published meta‐analytic findings . The loci of activation extracted from five imaging meta‐analyses are projected on a sagittal view (upper panel) and an axial view (lower panel) using the software BrainNet Viewer ( https://www.nitrc.org/projects/bnv).…”

“…Coupled with clinical and animal research, neuroimaging methods can also expand our knowledge about the association between the brain, the stomatognathic system and oral sensorimotor functions, in human subjects. MRI‐based neuroimaging methods have been widely used in clinical investigations on oral sensorimotor functions, including mastication, swallowing, gustation, acute and chronic oro‐facial pain, and dental anxiety and fear . Therefore, an increased amount of neuroimaging research has been reported in the field of oral neuroscience in recent years (Figure ).…”