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The motor nucleus of the facial nerve in the opossum ( Didelphis marsupialis virginiana ). Its organization and connections
Author(s) -
Dom Richard,
Falls William,
Martin George F.
Publication year - 1973
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901520405
Subject(s) - anatomy , biology , opossum , reticular formation , tegmentum , nucleus , neuroscience , hypoglossal nucleus , zona incerta , facial nerve , medial longitudinal fasciculus , midbrain , central nervous system
The organization of the facial nucleus was studied in the opossum by localizing neurons which stin poorly for acetylcholinesterase activity following transection of identified facial rami. The caudal auricular representation is limited to the ventromedial extreme of the nucleus, whereas the neurons contributing to the cervical ramus are situated dorsally and medially. The zygomatic representation extends throughout the intermediate portion of the nucleus, apparently overlapping with that of the palpebral and rostral auricular muscles which is limited to the ventral extreme of the intermediate zone. The buccolabial area is particularly large in the opossum and encompasses most of the lateral facial enlargement. Midbrain‐facial projections were identified from the superior colliculus, the midbrain tegmentum (particularly caudal ventromedial areas) and the red nucleus. The location of terminal degeneration in the facial nucleus following lesions within each of these areas was plotted and interpreted in light of facial organization. Of particular note is the fact that the fibers of rubral origin distribute preferentially to the zygomatic and, to some extent, buccolabial areas, whereas the ventromedial tegmental system distributes most strongly to the areas of caudal auricular, cervical, palpebral and rostral auricualar representation. The medial and intermediate regions of the facial nucleus receive a denser midbrain projection than does the lateral (buccolabial) area. In contrast, evidence was obtained for an extensive facial projection from the parvocellular reticular formation and the caudal spinal trigeminal nucleus which strongly favors the buccolabial enlargement. The possibility exists that the medial pontine and medullary reticular formation as well as portions of the dorsal column nuclei also have a facial projection. Spino‐facial fibers arise rostral to the cervical enlargement and show a predilection for the medial facial enlargement (cervical and caudal auricular areas). Although some systems distribute preferentially to specific areas of the facial nucleus, overlap is present suggesting considerable integration.