Meta-analysis of brain mechanisms of chewing and clenching movements

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.