Auditory Pathway

As it ascends from the cochlea to the auditory cortex, the auditory pathway gives off collateral projections to the cerebellum, the oculomotor and facial nuclei, cervical motor neurons, and the reticular activating system, which form the afferent arm of the acoustically mediated reflexes.

Axons of the cochlear nerve originating in the cochlear apex and base terminate in the anterior and posterior cochlear nuclei, respectively. These nuclei contain the second neurons of the auditory pathway. Fibers from the posterior cochlear nucleus decussate in the floor of the fourth ventricle, then ascend to enter the lateral lemniscus and synapse in the inferior colliculus (third neuron). The inferior colliculus projects to the medial geniculate body (fourth neuron), which, in turn, projects via the acoustic radiation to the auditory cortex. The acoustic radiation passes below the thalamus and runs in the posterior limb of the internal capsule. Fibers from the anterior cochlear nucleus also decussate, mainly in the trapezoid body, and synapse onto the next (third) neuron in the olivary nucleus or the nucleus of the lateral lemniscus. This branch of the auditory pathway then continues through the lateral lemniscus to the inferior colliculus and onward through the acoustic radiation to the auditory cortex. The primary auditory cortex (area 41: Heschl's gyrus, transverse temporal gyri) is located in the temporal operculum (i.e., the portion of the temporal lobe overlying the insula and separated from it by the sylvian cistern). Areas 42 and 22 make up the secondary auditory cortex, in which auditory signals are further processed, recognized, and compared with auditory memories. The auditory cortex of each side of the brain receives information from both ears (contralateral more than ipsilateral); unilateral lesions of the central auditory pathway or auditory cortex do not cause clinically relevant hearing loss.

Cochlear duct

Cochlear duct

Tonotopicity

Auditory cortex

Migrating wave, spectral analysis, tonotopicity

Auditory cortex

Superior colliculus Inferior colliculus -Medial -

-Cochlea

- Oval window

Stapes

Vestibular system

Malleus, incus

Superior colliculus Inferior colliculus -Medial -

-Cochlea

- Oval window

Stapes

Vestibular system

Malleus, incus

Hearing Pathway Blood Vessel

Posterior cochlear nucleus

Trapezoid body —

Medullary striae

Auditory tube ian tube)

Auditory (eustachi

Conduction of Sound; auditory pathway

Posterior cochlear nucleus

Trapezoid body —

Medullary striae

Auditory tube ian tube)

Auditory (eustachi

Conduction of Sound; auditory pathway

Cochlear n.

Cochlear duct

Cochlear ganglion

Organ of Corti, basilar membrane, hair cell

Cochlear n.

Cochlear ganglion

Cochlear Tonotopicity

- Scala vestibuli

- Scala tympani

Cochlea

20 000Hz

20 Hz

Stretch Marks

Stretch Marks

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Responses

  • marco
    Which auditory reflexes are mediated by via inferior colliculus?
    7 years ago

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