The human tongue during sleep: electromyographic activity of the genioglossus muscle.

The bilateral genioglossi muscles of the tongue, by virtue of their protrusive action, play an important role in the mechanics of maintaining an open air passage in the oropharyngeal region. Electromyographic studies of the genioglossus muscle during sleep were conducted in six healthy human volunteers. The principal results are the following: In quiet waking and in quiet sleep (stages I–IV), the genioglossal EMG is characterized by continuous discharges with substantially augmented activity during inspiration. When the subject enters REM sleep, the tonic genioglossal activity almost ceases except for small bursts during the inspiratory phase of respiration. During REM sleep, genioglossal motor units may become inactive for periods of up to 90 sec. However, these silent periods are regularly interrupted by three to six vigorous inspiratory genioglossal bursts. Genioglossal EMG with substantially augmented discharges during inspiration are best recorded from indwelling electrodes placed close to the origin of the muscle. During snoring, the genioglossal activity related to certain phases of the respiratory cycle is vastly increased. The results are discussed in context with problems encountered in hypersomniac patients with the sleep apnea syndrome.