Organization of the facial nucleus and corticofacial projection in the monkey

Abstract

The somatotopic organization of the facial nucleus and the distribution of the corticofacial projection in the monkey were studied by the use of retrograde and anterograde transport of horseradish peroxidase. Facial motor neurons innervating lower facial muscles were primarily found in the lateral part of the nucleus, those supplying upper facial muscles in the dorsal part of the nucleus, and those innervating the platysma and posterior auricular muscles in the medial part of the nucleus. Descending corticofacial fibers innervated the lower facial motor nuclear region bilaterally, although with contralateral predominance. The upper facial motor nuclear regions received scant direct cortical innervation on either side of the brain. Our results indicate that upper facial movement, like that at the shoulder, is relatively preserved in upper motor neuron palsy because these motor neurons receive little direct cortical input. By contrast, the lower facial muscles, like those of the hand, are more severely affected because their motor neurons normally depend upon significant cortical innervation.

Characterization of some morphological parameters of orbicularis oculi motor neurons in the monkey

“…Our study confirms that the somata of OO motorneurons reside in a restricted location of the facial nucleus that corresponds to the intermediate subnucleus (Fig. 2) and the observation that these neurons collectively form a longitudinal column in the rostrocaudal dimension, (Jenny and Saper, 1987;Porter et al, 1989;Welt and Abbs, 1990;Morecraft et al, 2001). We also found OO motor neurons to be multipolar and aspiny (Figs.…”

“…We also found OO motor neurons to be multipolar and aspiny (Figs. 2,3) and to occupy most of the facial nucleus in the rostrocaudal dimension with the exception of the inferior pole, as has been previously observed (Jenny and Saper, 1987;Welt and Abbs, 1990;Faulkner et al, 1997;VanderWerf et al, 1998;Morecraft et al, 2001).…”

“…With the same data collection system the adjacent Nissl stained tissue sections were charted by outlining the peripheral border of the facial nucleus and the respective subnuclei (i.e. intermediate, dorsalmedial, medial and lateral subnuclei) according to the criteria of Jenny and Saper (1987). The electronic files containing the charted LY profiles and the files containing the cytoarchitectonic boundaries were merged using the NeuroLucida software to determine the location of the LY labeled somata and dendritic fields in direct relation to the structural boundaries of the facial nucleus.…”

“…For example, brainstem innervation arises from the red nucleus, mesencephalic tegmentum, olivary pretectal nucleus, dorsolateral pontine tegmentum, principle trigeminal nucleus, ventrolateral pontine tegmentum and medullary tegmentum (Travers and Norgren, 1983;Holstege et al, 1984;Holstege et al, 1986;Isokawa-Akesson and Komisaruk, 1987). Additional studies have shown that several regions of the cerebral cortex directly innervate the intermediate subnucleus, including the face region of the primary motor cortex, lateral premotor cortex, supplementary motor cortex, rostral cingulate motor cortex and caudal cingulate motor cortex (Kuypers, 1958;Jenny and Saper, 1987;Morecraft et al, 2001;Gong et al, 2005). Therefore, our findings indicate that terminal projections from extrinsic sources have a high probability of establishing contacts with OO motor neuron somata and their dendrites within the boundaries of the intermediate subnucleus (Figs.…”

“…The nucleus is located in the lower ventrolateral pontine region of the brainstem and is musculotopically organized (Papez, 1927;Szentagothai, 1948;Crosby et al, 1963;Friauf and Herbert, 1985;Jenny and Saper, 1987;Satoda et al, 1987;Welt and Abbs, 1990;Morecraft et al, 2001;Sherwood, 2005). In the non-human primate, cell bodies innervating the orbicularis oculi muscle, which is the focus of this report, are localized in the dorsocentral portion of the nucleus, in an anatomical region designated by most authorities as the intermediate subnucleus (Kuypers, 1958;Jenny and Saper, 1987;Porter et al, 1989;Welt and Abbs, 1990;VanderWerf et al, 1998;Morecraft et al, 2001;Gong et al, 2005).…”