The paramedian reticular nucleus (in
Terminologia Anatomica
''Terminologia Anatomica'' is the international standard for human anatomical terminology. It is developed by the Federative International Programme on Anatomical Terminology, a program of the International Federation of Associations of Anatomis ...
, or paramedian medullary reticular group in
NeuroNames
''NeuroNames'' is an integrated nomenclature for structures in the brain and spinal cord of the four species most studied by neuroscientists: human, macaque, rat and mouse. It offers a standard, controlled vocabulary of common names for struct ...
) sends its connections to the spinal cord in a mostly ipsilateral manner, although there is some decussation.
It projects to the
vermis
The cerebellar vermis (from Latin ''vermis,'' "worm") is located in the medial, cortico-nuclear zone of the cerebellum, which is in the posterior fossa of the cranium. The primary fissure in the vermis curves ventrolaterally to the superior s ...
in the anterior lobe, the pyramis and the
uvula
The palatine uvula, usually referred to as simply the uvula, is a conic projection from the back edge of the middle of the soft palate, composed of connective tissue containing a number of racemose glands, and some muscular fibers. It also conta ...
.
The paramedian nucleus also projects to the contralateral PRN, the
gigantocellular nucleus
The gigantocellular reticular nucleus (Gi) is a subregion of the medullary reticular formation. As the name indicates, it consists mainly of so-called giant neuronal cells.
This nucleus has been known to innervate the caudal hypoglossal nucleus, ...
, and the
nucleus ambiguous.
The paramedian reticular formation is adjacent to the abducens (VI)nucleus in the pons and adjacent to the oculomotor nucleus(III) in the midbrain.
The paramedian nucleus receives afferents mostly from the
fastigial nucleus
The fastigial nucleus is located in the cerebellum. It is one of the four deep cerebellar nuclei (the others being the nucleus dentatus, nucleus emboliformis and nucleus globosus), and is grey matter embedded in the white matter of the cerebell ...
in the cerebellum and the cerebral cortex; however, the projections from the spinal cord are very sparse.
The descending afferent connections come mostly from the frontal and parietal lobes; however the pontine reticular formation also sends projections to the paramedian reticular nucleus.
There are also very sparse innervations from the
superior colliculus
In neuroanatomy, the superior colliculus () is a structure lying on the roof of the mammalian midbrain. In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe. The adjective form ''tectal'' is commonly ...
.
Lesions in the paramedian reticular nucleus have been shown to cause a stereotyped increase in the random patterns of motion in rats.
[Lee EH, et al. Multiple inhibitory actions of the paramedian reticular nucleus—effects on blood pressure and motor activities in rats. Chin J Physiol. 1990;33(1):49–61.] The paramedian nuclei on either side of the brain stem have been shown to mediate the horizontal
eye movements
Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of inte ...
on their
ipsilateral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
sides. It seems possible that the random motion patterns of the above rats were caused by an inability to mediate their horizontal eye movements.
See also
*
Paramedian pontine reticular formation
The paramedian pontine reticular formation, also known as PPRF or paraabducens nucleus, is part of the pontine reticular formation, a brain region without clearly defined borders in the center of the pons. It is involved in the coordination of eye ...
Notes
References
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Medulla oblongata