Cytoarchitecture and musculotopic organization of the facial motor nucleus in Cebus apella monkey

Abstract

The architecture and musculotopic organization of the facial motor nucleus in the Cebus apella monkey (a New World primate) were investigated using histological techniques and a multiple labelling strategy, in which horseradish peroxidase-conjugated neuroanatomical tracers (CTB-HRP and WGA-HRP) and fluorescent tracers were injected into individual facial muscles. The facial motor nucleus was formed by multipolar motoneurons and had an ovoid shape, with its rostrocaudal axis measuring on average 1875 µ m. We divided the nucleus into four different subnuclei: medial, intermediate, dorsal and lateral. Retrograde labelling patterns revealed that individual muscles were innervated by longitudinal functional columns of motoneurons. The columns of the orbicularis oculi, zygomaticus, orbicularis oris, auricularis superior, buccinator and platysma muscles were located in the dorsal, intermediate, lateral, medial, lateral and intermediate subnuclei, respectively. However, the motoneuron columns of the levator labii superioris alaeque nasi muscle and frontalis muscle could not be associated with a specific subnucleus. The present results confirm previous studies regarding the musculotopic organization of the facial motor nucleus. However, we observed some particularities in terms of the relative size of each column in C. apella , which might be related to the functional and behavioral importance of each muscle in the particular context of this primate.

Anatomical Characterization of a Rabbit Cerebellar Eyeblink Premotor Pathway Using Pseudorabies and Identification of a Local Modulatory Network in Anterior Interpositus

“…Labeled neurons were located in the dorsolateral and dorsal portions of the intermediate and lateral subdivisions of the nucleus forming a cap-like distribution in agreement with the location of motor neurons innervating the OOM found in previous studies (Radpour, 1977; Komiyama et al, 1984; Klein et al, 1990; VanderWerf et al, 1998; Horta-Junior et al, 2004; McNeal et al, 2008). Importantly, the same region of the nucleus was labeled in all rabbits.…”

On the Role of the Pontine Brainstem in Vocal Pattern Generation: A Telemetric Single-Unit Recording Study in the Squirrel Monkey

“…In contrast to MV, NVII neurons only rarely were activated by mastication, in addition. This is in harmony with the innervation field of NVII, which comprises mainly the facial muscles and only to a very small degree jaw-moving muscles (Welt and Abbs, 1990;Horta-Junior et al, 2004). NVII, in the present study, contained a relatively large number of neurons (69.6%) that were vocalization specific in the sense that they did not change their activity during mastication, quiet respiration, or acoustic stimulation.…”

“…In the squirrel monkey, a very common articulatory gesture is retracting of mouth corners during high-pitched vocalization (Marriott and Salzen, 1978). This gesture is controlled by NVII (Horta-Junior et al, 2004). Approximately two-thirds of VM neurons of NVII did not show any call specificity.…”

Direct and indirect connections between cochlear root neurons and facial motor neurons: Pathways underlying the acoustic pinna reflex in the albino rat

“…The Mot7 presents a common musculotopic organization among mammals. As observed in cats (Henkel and Edwards,1978; Populin and Yin,1995), Old World monkeys (Welt and Abbs,1990), New World monkeys (Horta‐Junior et al,2004), rats (Watson et al,1982; Hinrichsen and Watson,1984; Friauf and Herbert,1985), and other mammals (Sherwood,2005), the auricular muscles are innervated by motoneurons (auricular motoneurons) of the medial subnucleus.…”