continuous caudally with the *central canal of the spinal
cord. The lateral, third and fourth ventricles have a promi-
nent *choroid plexus.Ventricles, embryonic –The ventricular system is proportionally
larger during embryonic and fetal development than in the
mature central nervous system. Initially it is lined through-
out by the stem cells of the *neuroepithelium. As neu-
rogenesis declines, the ventricles shrink considerably, and
altogether disappear in many locations. At some sites, the
proliferative *subventricular zone replaces the neuroepi-
thelium, while at others the enduring ventricles are lined by
the specialized cells of the *ependyma.Ventromedial nucleus (hypothalamus) – Large spherical nucleus
that flanks the third ventricle and is surrounded by a fibrous
shell. It has reciprocal connections with the *amygdala,GLOSSARY
An asterisk in front of a term indicates that it has a separate entry in the Glossary with additional
information. Terms referring to transient developmental structures are underlined.
the *bed nucleus of the stria terminalis, the *septum, and
the *subiculum. It has been implicated in motivational
functions related to feeding and sexual behavior.Vermis – See Cerebellum (vermis).
Vestibular nuclear complex – A large area in the dorsal medulla,
composed of the *medial, the *lateral, the *superior, and
the *inferior vestibular nuclei. These nuclei get primary
sensory input from the vestibular ganglion; their efferents
join the *medial longitudinal fasciculus and form the ves-
tibulospinal tract.Visual radiation – Thalamocortical fibers beneath the cerebral
*white matter that originate in the *lateral geniculate body
and terminate in the *striate cortex of the occipital lobe.W
White matter – General term for extensive regions in the brain and
spinal cord composed of myelinated fiber tracts but few or
no neuronal cell bodies. In histological preparations with
myelin stains, the white matter appears black. In laminated
brain regions, as in the *cerebral cortex and the *cerebellar
cortex, the white matter is called the medullary layer.Z
Zona incerta – Sheet of *gray matter at the base of the *thalamus.
It is generally considered to be a rostral extension of the
*tegmentum. *Forel’s fields are contiguous with the zona
incerta.