Chewing-related hypofrontality in psychiatric disorders complaining occlusal dysesthesia

Objectives: Prefrontal cortex (PFC) involves in movement initiation, sensory processing, cognition, memory and learning. Preceding this study, we clarify the functional localization of chewing-related activity in the middle part of dorsal PFC by means of near infrared spectroscopy (NIRS) in healthy subjects. In a same time, dysfunction of dorsolateral prefrontal cortex and disruption of fronto-temporal integration is considerable to cause cognitive impairment in psychiatric disorders (Int Rev Psychiatry. 2007). In this study, we made an attempt to clarify the functional characteristics in the chewing-related PFC activity in psychiatric disorders complaining occlusal dysesthesia.

Methods: Seven psychiatric disorders (47.1±15.0 years old), such as somatoform, anxiety and depressive disorders and schizophrenia and 7 healthy subjects (34.0±13.8 years old) were participated in this study. NIRS system (HITACHI Medical Co, ETG-100) was used to detect hemoglobin concentration ([oxy-Hb]) in PFC. Bio-amplifiers (NEC) and Dental Prescale (Fuji Film Co) were also used to measure masseter muscle (Mm) EMG activity and occlusal contacts statuses. One session of chewing task was composed with 5 times chewing trials used chewing gum (Lotte Co, Freezone) and each chewing trial was 10 s duration. Measuring occlusal force and occlusal contact area using Dental Prescale was conducted under maximal jaw clenching condition. T-test (P<0.05) was used for the statistical comparison between psychiatric disorders and healthy subjects.

Results: Chewing-related PFC activities in psychiatric disorders were significantly (t-test, P<0.05) lower than that in healthy subjects. Chewing-related jaw muscle EMG activities and occlusal contacts statuses in psychiatric disorders were not significantly different from that in healthy subjects.

Conclusion: Chewing-related hypofrontality in psychiatric disorders complaining persisting occlusal dysesthesia might be related to disruption in cognitive process of occlusal sensation.