Somatotopic Representation of Facial Muscles Within the Facial Nucleus of the Mouse. A Study Using the Retrograde Horseradish Peroxidase and Cell Degeneration Techniques

The somatotopic representation of facial muscles within the facial nucleus was investigated by means of the retrograde horseradish peroxidase and cell degeneration techniques in the mouse. The nasolabial muscle is represented in the dorsolateral, lateral, and dorsal intermediate subnucleus; the mentalis muscle, in the ventral intermediate subnucleus; the platysma, in the dorsomedial part of the dorsal intermediate subnucleus and along the lateral border of the dorsomedial and ventromedial subnucleus; the orbicularis oculi and frontalis muscle, in the dorsal portions of the dorsolateral, dorsal intermediate, and dorsomedial subnucleus; the rostral and caudal auricular muscles, in the dorsomedial and ventromedial subnucleus, respectively; and the caudal belly of the digastric muscle, in the suprafacial nucleus. The present study shows that the facial muscles are represented in an orderly fashion in seven subnuclei of the facial nucleus, as in other animal species.