Electromyography of the oral phase of deglutition in the rhesus monkey ( Macaca mulatta)

Abstract

Patterns of activity of selected muscle groups which function during the oral phase of swallowing were analysed electromyographically in 33 monkeys ( Macaco mulatta) during a total of 113 recording sessions. Salivary, water and masticatory swallows were studied. The activity of the suprahyoid muscle group was relatively constant in each animal during all types of swallows. However, three patterns of muscle activity of the other masticatory muscles were identified. In the first pattern (pattern A), the suprahyoids usually fired concurrently with the superior head of the lateral pterygoid muscle with little or no elevator activity evident. In the second pattern (pattern B), the temporal muscle, masseter muscle and superior head of the lateral pterygoid muscle fired concurrently with the suprahyoids. In the third pattern (pattern C), elevator and lateral pterygoid activity preceded the suprahyoid burst. The inferior head of the lateral pterygoid was not active in any swallowing pattern. About 60–70 per cent of the salivary swallows were of pattern A. Most water-swallows were of patterns B and C, while those swallows associated with mastication were entirely of pattern C.