The trapezoid body or ventral acoustic stria is a structure in the
pontine tegmentum formed by the
crossing-over (decussation) of a portion of the
efferent second-order fibers of the
ventral cochlear nucleus (anterior cochlear nucleus). After decussating, some of these fibres proceed to ascend in the contralateral
lateral lemniscus
The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. Three distinct, primarily ...
to reach and terminate in the dorsal nucleus of lateral lemniscus, and inferior colliculus.
The trapezoid body is part of the
auditory pathway
The auditory system is the sensory system for the sense of hearing. It includes both the sensory organs (the ears) and the auditory parts of the sensory system.
System overview
The outer ear funnels sound vibrations to the eardrum, increas ...
. It is one of three distinct decussating second-order efferent fiber pathways of the cochlear nuclei (the other two being the
dorsal acoustic striae, and
intermediate acoustic striae).
Not all efferents of the cochlear nuclei decussate though; the partial decussation of the cochear nuclei afferents is thought to be functionally important for sound localization.
Anatomy
The trapezoid body is formed by horizontally-oriented,
commissural fibers
The commissural fibers or transverse fibers are axons that connect the two hemispheres of the brain. Huge numbers of commissural fibers make up the commissural tracts in the brain, the largest of which is the corpus callosum.
In contrast to ...
which are readily identifiable.
Projections
The fibres of the trapezoid body terminate (synapse) in the (contralateral):
*
medial nucleus of trapezoid body (which in turn projects third-order fibres to medial
superior olivary nucleus),
* medial superior olivary nucleus,
*
dorsal nucleus of lateral lemniscus,
*
inferior colliculus
The inferior colliculus (IC) (Latin for ''lower hill'') is the principal midbrain nucleus of the Auditory system, auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the aud ...
.
Relations
It is situated in (the caudal portion of
) the ventral
pontine tegmentum at the level of the pontomedullary junction.
It is situated immediately dorsal/posterior to the
pontine nuclei, and ventral/anterior to the
medial lemnisci.
References
Pons
Auditory system
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