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The tympanic membrane (ear drum) separates the
external ear (pinna, ext. auditory meatus) from the
middle ear (contains ossicles: malleus, incus, stapes).
From Noback & Demarest,
The Human Nervous System
The vestibulocochlear nerve (C.N. VIII) enters the
brainstem at the pontocerebellar angle. It has two
divisions: auditory and vestibular.
Abducens
nerve
Facial nerve
Flocculus
Auditory fibers in CN VIII first synapse in the cochlear
nuclei in the dorsolateral medulla.
Inferior Cerebellar
Peduncle
Dorsal Cochlear
Nucleus
Ventral Cochlear
Nucleus
Pontocerebellar
Angle
Vestibulocochlear Nerve
(C.N. VIII)
The medial
geniculate
nucleus projects
to the superior
transverse
temporal gyri
(primary
auditory cortex)
via the
sublenticular
part of the
posterior limb of
the internal
capsule
(“auditory
radiations”).
Primary Auditory Cortex: Sup. Transverse Temporal Gyri
Brodmann’s Areas 41, 42
The efferent cochlear bundle originates from the superior
olivary nucleus and projects thru the VIIIth nerve to the
auditory receptor organ (Organ of Corti) to focus auditory
attention.
From: Carpenter, Human Neuroanatomy
Dorsal Cochlear Nucleus
Inferior
Cerebellar
Peduncle
Ventral
Cochlear
Nucleus
Superior
olive
Lateral
lemniscus
Trapezoid
body
Lateral Lemniscus
ML
Commissure of the
inferior colliculus
Inferior Colliculus
Most of the fibers
in the lateral
lemniscus synapse
in the inferior
colliculus, and
then auditory
information is
conveyed thru the
brachium of the
inferior colliculus
to the medial
geniculate nucleus.
SC
Brachium of the
Inferior Colliculus
Carries fibers from
the inferior colliculus
to the medial
geniculate nucleus
IC
Medial geniculate
nucleus
The medial geniculate nucleus projects to
the primary auditory cortex (superior
transverse temporal gyri, areas 41, 42).
Descending
feedback
pathways at all
levels within the
auditory system
function in sound
localization.