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Reflex Control Of Extrinsic Tongue Muscle Activities By Lingual Mechanoreceptors.
Published 1974 · Medicine
An attempt has been made to clarify the exteroceptive control mechanism of extrinsic tongue muscles in cats. For this purpose, excitatory and inhibitory receptive fields of extrinsic tongue muscle motor units on the tongue surface have been investigated in urethanechloralose anesthetized or decerebrate cats.1. Styloglossal motor units responded with spike discharges to gentle stroking of the anterior part of the tongue dorsum. The receptive field of this reflex response has been classified into 5 types; ipsilateral filiform type (iF type), ipsilateral nonfiliform type (iNF type), bilateral nonfilifbrm ype (bNF type), ipsilateral filifbrm plus ipsilateral nonfliform type (iF+iNF type) and ipsilateral filifbrm plus bilateral nonfiliform type (iF+bNF type). The majority of styloglossal motor units were of the bNF type in urethane-chloralose anesthetized cats. On the other hand, motor units of the iF type dominated in decerebrate cats.2. Hyoglossal motor units were divided into two groups; ventral and dorsal. Ventral hyoglossal motor units responded with spike discharges to gentle stroking of the ipsilateral posterior part of the tongue dorsum, while dorsal hyoglossal motor units to that of the ipsilateral filiform area of the anterior tongue dorsum.3. Only a minority of genioglossal motor units responded with spike discharges to tactile stimulation of the filiform area of the anterior tongue. In most responsive genioglossal motor units, the excitatory receptive fieldwas located in the ipsi-or bilateral filiform area of the anterior tongue. In a few cats, however, the excitatory receptive field was in the ipsilateral Dosterior part of the tongue dorsum.4. Some styloglossal and hyoglossal motor units responded with spike discharges to tactile stimulation of the ventral surface of the tongue, but none of the genioglossal motor units responded to it.5. Some genioglossal and ventral hyoglossal motor units exhibited nonrespiratory spontaneous discharges, but no styloglossal and dorsal hyo-glossal motor units showed them. However, the majority of styloglossal motor units responded with spike discharges to jaw opening.6. Inhibition of spike discharges was demonstrated with styloglossal and genioglossal motor units. The inhibitory receptive field of styloglossal motor unit was located on the ipsilateral posterior part of the tongue dorsum. In most genioglossal motor units, the inhibitory receptive field was on the ipsi-, contra- or bilateral posterior part of the tongue dorsum.