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• A new method for recording buccinator activity deep in the face has been tested. • The new electrode is small, can be easily set at the right place, and is contamination free. • The buccinator pulls at the corner of the mouth, assisting forceful closure. • Functional activity patterns were identical to those by intramuscular electrodes. • The new electrode can be utilized for studies on chewing. The buccinator (BUC) is an important muscle for oral function. Since it lies deep in the facial skin, recording its activity is difficult; thus, studies on its function are limited. We developed a method to access the deep facial muscles from the mucosal side. The aim of this study was to test the reliability of the new recording method for the BUC and to investigate the BUC behavior in typical facial functions. To evaluate the new method, BUC activities were recorded simultaneously with a gel-type electrode on the skin and the newly developed surface electrode on the buccal mucosa. Electromyographic (EMG) activities in function, such as chewing and swallowing, along with the activities of the lower orbicularis oris (OO), zygomaticus major, masseter, and digastric muscles, were compared using the two recording methods. EMG activities among various tasks were compared using normalized values based on those obtained during maximum lip closure (MaxLC). The new surface electrode was made of gold plates on a thin plastic fixed to a stainless-steel wire frame and weighed less than 1 g. The BUC activity recorded from the mucosa was the highest during a corner-pulling task and was low during clenching. The BUC was active during MaxLC, similar to the OO, and the BUC activity pattern among tasks recorded from the mucosa was identical to that reported by previous studies using intramuscular electrodes. The new electrode evaluated the BUC activities quantitatively, and the recordings by the new electrode were free from contamination. The findings of this study confirmed the reliability of the new BUC recording method. It could be easily placed correctly within seconds, without the need for cleansing or sterilizing the skin. The BUC and OO were active during a MaxLC task, indicating that the BUC assists lip closure by pulling the corners of the mouth. The basic facial functions evaluated, including chewing, were similar to those studied by intramuscular electrodes. [ABSTRACT FROM AUTHOR]

• Swallowing timings were evaluated by two barometers in oral cavity and oropharynx. • Anterior and posterior intrinsic tongue EMGs were also recorded. • Timings of nasopharyngeal closure could be measured by the sensor in oral cavity. • Durations of oral and pharyngeal stages of swallowing were measured as 0.4 and 0.6 sec. • The tongue begins the activity for swallowing before nasopharyngeal closure. : The exact timings associated with swallowing are difficult to measure with the currently available methods. In this study, we aimed to elucidate the timings of action of the swallowing organs in the oral and pharyngeal stages of swallowing by recording the barometric pressure (BP) and tongue muscle activities. : Dry and water swallows were studied in 10 adults using electromyography and small barometers. BPs were recorded during swallowing in the oral cavity (BP-o) and pharynx (BP-p), associated with muscle activities of the anterior (TA) and posterior (TP) parts of the tongue and of the suprahyoid (SHy) muscle. To analyze the temporal pattern of each activity, times of onset, cessation, and peak were measured. : Two characteristic waveforms were obtained. BP-o peaked immediately after onset and decreased to atmospheric pressure following a short plateau. However, BP-p gradually increased, reached a peak, and returned to the atmospheric pressure immediately before the end of BP-o. Since pressure increments indicated that the sensor was compressed in a closed space, onset and cessation of BP-p could correspond to the duration of nasopharyngeal closure. The onset of BP-p and the peak time of BP-o occurred in close succession. Thus, nasopharyngeal closure could be evaluated from BP-o. The sensor and EMG measured durations of oral and pharyngeal stages as 0.4 and 0.6 sec, respectively. TA activation began earlier than the TP. TA and TP peaks appeared before the BP-o peak, suggesting that the tongue begins the activity for swallowing before nasopharyngeal closure. : This study revealed movements of swallowing organs in the two stages with high temporal resolution. BP-o detected the duration of nasopharyngeal closure. [ABSTRACT FROM AUTHOR]