The electromyographic activities of jaw and hyoid musculature in different ingestive behaviours in the cat.

Electromyographic (EMG) activity in the muscles moving the jaw, hyoid and tongue of the cat was recorded during the intake of solid and liquid foods; the nature of the movements of the jaw, hyoid, tongue and food were recorded and identified cineradiographically. Synergy was evident in muscles with similar anatomical orientation. However, most muscles were activated more than once during each jaw cycle and some of these additional periods of activation occurred at times not predicted by the anatomical arrangement of the muscles. The pattern of EMG activity was the same during all lapping cycles (excluding lap/swallow cycles) but was characteristically different from that occurring during the ingestion of solid food. With solid food the EMG pattern changed during the course of the ingestive sequence and was characteristic for each of the four successively different types of jaw cycle, i.e. transport cycles moving food back from the front of the mouth to the cheek teeth, chewing cycles, transport cycles moving food through the fauces and, following the accumulation of a bolus in the vallecula, swallowing cycles. In these data, provided that the EMG activities of a complete ingestive sequence were available (from food pick-up to swallow), the cycle type could be identified from the intracycle timings and amplitudes of the bursts of EMG activity occurring in the fibres of temporal, posterior digastric and geniohyoid muscles alone. Two variable components of the cyclical EMG pattern could be identified, one relating to tongue movement, the other to jaw movement.