Analysis of brain activity involved in chewing-side preference during chewing: an fMRI study.

The aim of this study was to investigate the activation characteristics of cerebral cortex in participants with CSP during rhythmic chewing movement. Sixteen right-handed participants with left (two males: 29·0 ± 8·4 years old, six females: 32·3 ± 4·8 years old) or right (four males: 31·0 ± 6·1 years old, four females: 30·8 ± 4·7 years old) CSP were scanned by functional magnetic resonance imaging during rhythmic chewing. The on-off sequence of scanning was 30 s of rhythmic chewing and 30 s of rest (off) a total of five times. The results showed that blood oxygen level-dependent signals in the contralateral (to the CSP) primary sensorimotor cortex increased more than in the ipsilateral primary sensorimotor cortex in participants with both left and right CSP (P ≤ 0·001). Moreover, the BOLD signal within the right substantia nigra of midbrain, brainstem was more significantly (P ≤ 0·001) activated than its left counterpart in participants with left CSP, while no activation was observed in those with right CSP. The similar activation of the cerebellum was in participants with right CSP. The inferior parietal lobule, inferior frontal gyrus and left insular cortex were significantly (P ≤ 0·001) activated in participants with CSP. These findings suggest a relationship between hemispheric dominance and CSP in the primary sensorimotor cortex responsible for rhythmic chewing movement. The brainstem and the cerebellum might also play important role in the regulation of CSP. Furthermore, the IFG, IPL and insular may contribute to higher cognitive information processing for participants with CSP.