Functional Anatomy of the Auditory System: From Cochlea to Cortex
 
 
 
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Chapter 10. Functional Anatomy of the Auditory System: From Cochlea to Cortex

Demonstration 10.1
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Functional Anatomy of the Auditory System: From Cochlea to Cortex

Interact with depictions of the structures and pathways from the cochlea to the auditory cortex

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This fMRI image shows neural activity within two regions of the auditory cortex, in the upper part of the temporal lobe.
Photo: Ahveninen, J., Jääskeläinen, I.P., Raij, T., Bonmassar, G., Devore, S. Hämäläinen, M., Levänen, S., Lin, F.H., Sams, M., Shinn-Cunningham, B.G., Witzel, T., Belliveau, J.W. (2006). Task-modulated "what" and "where" pathways in human auditory cortex, Figure 3. Proceedings of the National Academy of Sciences USA, 103, 14608–14613. © 2013 National Academy of Sciences, U.S.A.

What Is the Functional Anatomy of the Auditory System?

Type I auditory nerve fibers carry signals from inner hair cells in the cochlea to the ipsilateral cochlear nucleus in the brain stem. From there, the main pathways carry signals to the contralateral side of the brain, but signals in the secondary pathways remain mostly on the ipsilateral side. The structures on these pathways include the contralateral trapezoid body and both the ipsilateral and contralateral superior olivary complex, inferior colliculus, medial geniculate body (MGB), and auditory cortex.

The auditory cortex is tucked into the lateral sulcus on top of the temporal lobe. The primary auditory cortex (or A1) is one of three areas that constitute the auditory core region (the other two are the rostral core and the rostrotemporal core). Signals from the auditory core flow to two regions wrapped around it, the belt and the parabelt, each of which also contains distinct subareas.

Neurons within each of the three areas that constitute the auditory core region are arranged into a tonotopic map, as are neurons in each of the subcortical structures in the ascending auditory pathways. In the auditory core, the characteristic frequencies of neurons in the rostrotemporal core and A1 gradually shift from low at the anterior end of the region to high at the posterior end; in the rostral core, the shift is in the opposite direction.
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These illustrations depict the contralateral and ipsilateral flows of neural signals from the cochlea of the right ear to the auditory cortex. To show that you understand these flows, drag the labels on the anatomical illustration into the correct blank boxes in the schematic diagram. You may use each label more than once.

Contralateral
Ipsilateral
Main pathways
Secondary pathways
Cochlea
Auditory cortex
Medial geniculate body
Inferior colliculus
Cochlear nucleus
Auditory nerve
Superior olivary complex
Trapezoid body
Auditory cortex
Medial geniculate body
Inferior colliculus
Superior olivary complex
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Drag and drop the labels into the correct blank boxes on these illustrations of the auditory cortex.

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Characteristic Frequency
Rostrotemporal core
High
Auditory core region
Rostral core
A1
Occipital lobe
Low
Frontal lobe
Parabelt
Parietal lobe
Lateral sulcus
Auditory cortex
Belt
Temporal lobe
explain_text

What Is the Functional Anatomy of the Auditory System?

Type I auditory nerve fibers carry signals from inner hair cells in the cochlea to the ipsilateral cochlear nucleus in the brain stem. From there, the main pathways carry signals to the contralateral side of the brain, but signals in the secondary pathways remain mostly on the ipsilateral side. The structures on these pathways include the contralateral trapezoid body and both the ipsilateral and contralateral superior olivary complex, inferior colliculus, medial geniculate body (MGB), and auditory cortex.

The auditory cortex is tucked into the lateral sulcus on top of the temporal lobe. The primary auditory cortex (or A1) is one of three areas that constitute the auditory core region (the other two are the rostral core and the rostrotemporal core). Signals from the auditory core flow to two regions wrapped around it, the belt and the parabelt, each of which also contains distinct subareas.

Neurons within each of the three areas that constitute the auditory core region are arranged into a tonotopic map, as are neurons in each of the subcortical structures in the ascending auditory pathways. In the auditory core, the characteristic frequencies of neurons in the rostrotemporal core and A1 gradually shift from low at the anterior end of the region to high at the posterior end; in the rostral core, the shift is in the opposite direction.

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Based on the flows of neural signals depicted in this demonstration, which structures do NOT receive signals carrying information the cochlea of the right ear?

A.
The left cochlear nucleus and the right superior olivary complex.
B.
The right inferior colliculus and the right auditory cortex.
C.
The left trapezoid body and the right medial geniculate body.
D.
The right trapezoid body and the left cochlear nucleus.
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Incorrect. The correct answer is D. Click EXPLAIN if you want to review this topic.
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What are the components of the auditory core region?

A.
The auditory cortex and A1.
B.
The belt and parabelt.
C.
A1, the rostral core, and the rostrotemporal core.
D.
A1 only.
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Incorrect. The correct answer is С. Click EXPLAIN if you want to review this topic.
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Which statement correctly describes the tonotopic organization of neurons within the auditory core region?

A.
Neurons in the rostral core and rostrotemporal core all have the same characteristic frequency, whereas neurons in A1 have a different characteristic frequency.
B.
Neurons in the rostrotemporal core and A1 have characteristic frequencies that shift from low to high in the same direction; neurons in the rostral core have characteristic frequencies that shift in the opposite direction.
C.
Neurons in the rostral core and A1 have characteristic frequencies that shift from low to high in the same direction; neurons in the rostrotemporal core have characteristic frequencies that shift in the opposite direction.
D.
Neurons in A1, the rostral core, and the rostrotemporal core have characteristic frequencies that shift from low to high in the same direction.
Correct! Click EXPLAIN if you want to review this topic.
Incorrect. The correct answer is B. Click EXPLAIN if you want to review this topic.
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