We rely on visual information to recognize food and carry it to our mouth. In contrast, many animals use olfactory information to locate food and take their mouth to the food. Moreover, animals eat to survive, while humans engage in feeding behavior for various reasons which include survival. This difference suggests that the role of the cerebral cortex in feeding behavior in animals is similar, but not identical, to that in humans. The motor cortex and somatosensory cortex, which include the cortical masticatory area play an important role in voluntary mastication in feeding. However, the role of the cerebral cortex in the anticipatory and preparatory stage in feeding behavior is not clear, even though the involvement of higher brain function has been suggested. Here, we discuss the functional role of the cerebral cortex in the anticipatory and preparatory stage of feeding based on our study results and previous neuroscientific findings regarding visual information processing as well as reaching and grasping movement.

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[Purpose] In electromyographic (EMG) examination of sleep bruxism (SB), the relative value against the burst at maximum voluntary contraction (MVC), i.e., %MVC value, is usually applied to standardize obtained data of EMG muscular activity. In this study, we investigated the correlation between %MVC value of SB bursts and maximum bite force that is exerted in an awake state to clarify their relationship.
[Methods] Twenty-nine sleep bruxers participated in this study. Polysomnography (PSG) including masseteric EMG with audio-video recordings was carried out, and SB bursts were classified into 4 categories:a burst judged as a true SB (SBB), one or two consecutive phasic bursts (POE), bursts originating in other movements (OMB) and bursts during transient awake periods after onset of sleep. The average of %MVC values of each category and %MVC value of the maximum burst in each category were calculated and designated as “average-%MVC” and “max-%MVC”, respectively. Maximum bite force during a awake period was measured using Dental Prescale®.
[Results] The smaller maximum bite force was, the larger was average-%MVC, and a significant negative correlation was found between maximum bite force and average-%MVC in SBB, POE, OMB, WB, and total bursts including all categories. The same tendency was found in max-%MVC, and there were significant negative correlations in SBB, POE, OMB, and total bursts.
[Conclusions] For assessment of SB based on %MVC values in an SB EMG examination, there is a possibility that bite force is assessed as being higher than the actual force in cases with less maximum bite force and assessed as being lower than the actual force in cases with stronger maximum bite force. We need to take these characteristics into consideration when interpreting EMG results expressed using %MVC values.

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[Purpose] To clarify the characteristics of the normal state of masticatory muscle activity during the night and day including meal times, activity of masseter muscles in an unconstrained condition in healthy subjects during a 24-hour period was measured by using an ultraminiature wearable electromyogram (EMG) system.
[Methods] Ten male and ten female young adults without any impairments participated in this study. Masseter muscle activities were measured during the whole day by using a data-logger-type EMG measuring system with built-in electrodes and memory. EMG bursts of more than three times the baseline amplitude (3-BL) or 20% of the amplitude of maximum voluntary contraction (20%MVC) were selected and classified into three categories: those during meal time, those during the daytime except for meal time (EM-daytime) and those during sleep.
[Results] EMG amplitude during meal time was larger than that during other time categories, but the duration was shorter and the standardized integral value per one wave pattern was smaller. The ratio of standardized integral value during sleep was approximately 5% under both conditions of amplitude threshold. The ratios during EM-daytime and during meal time were 41.1% and 53.3% at the 3-BL threshold, while the ratios at the 20%MVC threshold were 34.1% and 60.3%, respectively.
Totals of standardized integral values during meal time, EM-daytime and sleep time were equivalent to 387, 342 and 32 times that during 10-cycle chewing of softened gum, respectively.
In addition, high level correlations were found in the wave pattern amplitude and the standardized integral value per one wave pattern between meal and gum chewing.
[Conclusions] The relations among masseteric EMG activities during meal time, EM-daytime, sleep time and gum chewing were clarified. The data obtained in this study will be important as reference data in further investigations for elucidating characteristics of whole-day-long masticatory muscle activity in patients with disorders of stomatognathic function.

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Feeding behavior drastically changes from suckling to chewing during the postnatal period. Thus, it is possible that the firing properties of jaw-closing motoneurons (JCMNs), one of the final common pathways in the oro-motor system, are also altered during the postnatal period. We examined the repetitive firing properties of JCMNs in developing rats from an early postnatal stage to a post-weaning stage using intracellular recording techniques. Firing frequency adaptation was observed within the first four spikes in a spike train. The neurons were classified into two groups according to the firing patterns subsequent to the first four spikes: neurons with a constant or slightly decrementing firing pattern (type I) and neurons with an incrementing firing pattern (type II). The percentage of type I neurons increased with age. In more than 50% of the neurons in each age group except for the group at 10-15 days of age, an extra spike was produced from the post-spike afterdepolarization (ADP) of the 1st spike in a spike train, leading to a high firing rate for the first inter-spike interval (1st ISI). The incidence of an extra spike also increased with age. The firing rate for the steady-state was high in JCMNs, even at 4-9 days of age, and approximately 50% of the neurons at this age fired at higher than 50 Hz. These findings demonstrate that JCMNs can fire at a high rate, even in the early postnatal period, and the firing rate for the 1st ISI further increases with age. These changes may contribute to the transition from suckling to chewing.

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The purpose of this study was to elucidate the influence of two categories of auditory stimuli, pure tone and healing music, on sweet and salty gustatory sensitivity.
In experiment 1, 22 healthy subjects were recruited to determine the effect of pure tone on the gustatory thresholds of sweet and salty tastes. Pure tones at 10Hz, 4, 000 Hz, and 20, 000 Hz were used as auditory stimuli, and the intensity of the sounds was set to 50dB. The qualities of taste used in the experiment are sweet (sucrose) and salty (NaCl), and the concentration of each taste quality was 0.005M, 0.010M, 0.050M, and 0.100M. Each subject received auditory stimuli for 15 minutes, and the gustatory threshold was investigated using a whole-mouth gustatory test method.
In experiment 2, 22 healthy subjects were recruited to determine the effect of healing music on sweet and salty tastes intensity by utilizing visual analogue scaling (VAS). The music used as the auditory stimuli were as follows: (1) music CD 1 (Heartful Classics Mozart BEST), (2) music CD 2 (The Mozart Therapy), and (3) music CD 3 (Ultimate Sleeping CD). The gustatory threshold was investigated the same as it was in the experiment 1. Moreover, the subjective intensity of taste was scored by the VAS, and that score was evaluated as the sensitivity of gustation. In addition, the subjects were investigated regarding the effect of their music preference on their gustatory sensitivity.
In summary, pure tone auditory stimuli did not affect gustatory function. However, these results suggest that music, especially as a music preference, affects the sensitivity of sweet taste.

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