HIS 120 Afferent Deprivatrion and Efferent Influence

Afferent Deprivation & Efferent InfluenceAfferent Deprivation & Efferent Influence

Superior Olivary complexSuperior Olivary complex

This is the auditory point furthest from the This is the auditory point furthest from the auditory cortex in the temporal lobe where auditory cortex in the temporal lobe where information from both ears’ cochlea is information from both ears’ cochlea is processed. processed.

In other words, it receives information to In other words, it receives information to process from both cochlea.process from both cochlea.


Superior Olivary ComplexSuperior Olivary Complex

It controls reflex activity of both middle ear It controls reflex activity of both middle ear muscles (tensor tympani and stapedius). muscles (tensor tympani and stapedius).

It takes information from both ears and It takes information from both ears and codes it into auditory localization.codes it into auditory localization.


Inferior ColliculusInferior Colliculus

Most of the information processed by the Most of the information processed by the Superior olivary complex is received here. Superior olivary complex is received here.

At this level, auditory information is At this level, auditory information is synthesized and coordinated with visual, synthesized and coordinated with visual, vestibular, and somatosensory systems.vestibular, and somatosensory systems.



Just above, is the Just above, is the superior colliculussuperior colliculus which which controls visual localization. The proximity controls visual localization. The proximity of these two nerve centers, facilitates of these two nerve centers, facilitates localizing and identifying the source of any localizing and identifying the source of any sound. sound.



This is where the “startle reflex” is This is where the “startle reflex” is initiated. It is the primary path leading to initiated. It is the primary path leading to the medial geniculate bodies of the the medial geniculate bodies of the thalamus. The Thalamus is, of course, the thalamus. The Thalamus is, of course, the “routing center” for the higher motor and “routing center” for the higher motor and sensory areas of the brain and midbrain.sensory areas of the brain and midbrain.


Auditory CortexAuditory Cortex

The auditory cortex in the left temporal The auditory cortex in the left temporal lobe is larger than the right side. It has lobe is larger than the right side. It has been found that it processes most of the been found that it processes most of the complex speech information.complex speech information.


Olivocochlear Bundle (OCB)Olivocochlear Bundle (OCB)

This is an important portion of the This is an important portion of the EFFERENT path. It moves information EFFERENT path. It moves information from the superior olivary complex down to from the superior olivary complex down to the Organ of Corti.the Organ of Corti.


Olivocochlear Bundle (OCB)Olivocochlear Bundle (OCB)

There are two primary components to this There are two primary components to this neural pathway. They are:neural pathway. They are:

1.1. Crossed olivocochlear bundle (COCB)Crossed olivocochlear bundle (COCB)2.2. Uncrossed olivocochlear bundle (UOCB)Uncrossed olivocochlear bundle (UOCB)


Crossed Olivocochlear Bundle (COCB)Crossed Olivocochlear Bundle (COCB)

Its efferent pathway inhibits the intensity of Its efferent pathway inhibits the intensity of sound needed to initiate a response to a sound needed to initiate a response to a stimulus. stimulus.

In other words, it reduces afferent In other words, it reduces afferent cochlear output. cochlear output.

It affects the It affects the inner hair cellsinner hair cells of the of the contralateralcontralateral cochlea. cochlea.


Uncrossed Olivocochlear Bundle (UOCB)Uncrossed Olivocochlear Bundle (UOCB)

Its efferent pathway also inhibits the Its efferent pathway also inhibits the intensity of sound needed to initiate a intensity of sound needed to initiate a response to a stimulus. response to a stimulus.

However, its affect is upon the three rows However, its affect is upon the three rows of of outer hair cellsouter hair cells on the on the ipsilateralipsilateral cochlea. cochlea.


UCOB & COCB PurposeUCOB & COCB Purpose

These two olivocochlear bundles may be These two olivocochlear bundles may be considered as “gatekeepers” for acoustic considered as “gatekeepers” for acoustic sensory input. They may be why we can sensory input. They may be why we can “tune out” certain auditory information. In “tune out” certain auditory information. In other words, allow certain sounds to come other words, allow certain sounds to come to consciousness while excluding others.to consciousness while excluding others.


Efferent InhibitionEfferent Inhibition

Activation of the efferent auditory system Activation of the efferent auditory system depends on the depends on the AFFERENT inputAFFERENT input from from other sensory systems.other sensory systems.


Efferent InhibitionEfferent Inhibition

The thalamus collects and distributes The thalamus collects and distributes sensory information. Its response to sensory information. Its response to various sensory systems will influence the various sensory systems will influence the efferent information received by the efferent information received by the superior olivary complex. superior olivary complex.

This efferent information is then This efferent information is then distributed through the olivocochlear distributed through the olivocochlear bundle to each respective cochlea.bundle to each respective cochlea.

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HIS 120 Afferent Deprivatrion and Efferent Influence