Chewing side preference and prefrontal cortex activity

Objectives: Prefrontal cortex (PFC) involves in movement initiation, sensory processing, cognition, memory and learning. Especially concerning chewing-related PFC activity revealed in previous f-MRI study (Onozuka, 2003), still incompletely understanding was remained in its critical participation for orofacial sensorimotor functions. In this study, we made an attempt to clarify PFC involvement in chewing side preference.

Methods: Seven adults (26-55 years old) were subjected in this study. Near-infrared spectroscopy (HITACHI Medical Co, ETG-100) and Bio-amplifiers (NEC Co) were used to detect the hemoglobin concentration ([oxy-Hb]) in PFC and masseter muscle (Mm) EMG activity in preference side chewing and non-preference side chewing. Occlusal contact statuses, such as force and occlusal contact area were also measured with Dental Prescale (Fuji Film Co). Chewing task used chewing gum (Lotte Co, Freezone) was composed with 5 times chewing trials and each trial was 10 s duration. Statistical analysis with paired t-test was applied to compare preference side chewing to non-preference side chewing.

Results: Chewing-related PFC activity was indicated in the middle part of dorsal PFC. Activities of middle part of dorsal PFC in preference side chewing (0.0294±0.0291 mMmm) were significantly (p<0.05) higher than that in non-preference side chewing (0.0017±0.0231 mMmm). Concerning Mm EMG activity, only burst duration was significantly (p<0.05) elongated in preference side chewing (279.7±51.3 ms) by comparison with non-preference side chewing (269.2±59.6 ms). Occlusal contact statuses were not significantly different between preference chewing side and non-preference chewing side.

Conclusion: It is assumed that middle part of dorsal PFC may involve in side preference of chewing. In contrast, occlusal contact statuses may have an insignificant effect in side preference of chewing.