AUTO-REGULATORY NEUROMECHANISM OF THE TONGUE MUSCLE ACTIVITY

The neural feedback system controlling tongue muscle activities was studied in the decerebrate cat.Spontaneous activities were detected from some muscular fibers of the tongue. The discharges of some fibers in the tongue retractors were increased and those in the tongue protruders were decreased by forward stretch of the tongue. These responses were not affected by anesthesia of the tongue surface. However, the responses completely disappeared after dissection of the lingual or glossopharyngeal nerve.In the lingual and glossopharyngeal nerves, a few fibers were detected to respond to stretch of the tongue. This response was slowly adaptive and the frequency of impulses from the nerve fibers was increased in proportion to the intensity of tongue stretching.The activity of several spots in the sensory nucleus of trigeminal nerve, in the nucleus of solitary tract, in the dorsal nucleus of vagal nerve, in the bulbar reticular formation and in the nucleus of hypoglossal nerve was activated by stretch of the tongue. On the contrary, the activity of some spots in the hypoglossal nucleus was inhibited.