Anatomy of the Auditory and Visual Pathways

Question 1

Where are the organs of hearing and balance located?

Answer 1

In the inner ear within the temporal bone

Question 2

What nerve is responsible for hearing?

Answer 2

Cochlear nerve = CN VIII

Question 3

What does the organ of Corti contain?

Answer 3

Outer and inner hair cells

Question 4

What does the spiral ganglion contain?

Answer 4

Bipolar neurons stimulated by hair cells and carrying APs from organ of Corti to cochlear nuclei of pons

Question 5

Why is input above the cochlear nuclei essentially bilateral?

Answer 5

Some fibres are crossed and some are not

Question 6

What are the superior olivary nucleus and nucleus of the lateral lemniscus important in?

Answer 6

Sound location and as relays for stapedial and tensor tympani reflexes

Question 7

Where is the auditory cortex located?

Answer 7

Medial geniculate nucleus of the thalamus

Question 8

What is Wernicke’s area known as?

Answer 8

Auditory association cortex

Question 9

What kind of organisation is present in the auditory cortex?

Answer 9

Tonotopic organisation

Question 10

Where do fibres carrying low frequency sound information end?

Answer 10

In the anterolateral part of the auditory cortex

Question 11

Where do fibres carrying high frequency sound information end?

Answer 11

In the posteromedial part of the auditory cortex

Question 12

What is aphasia?

Answer 12

Inability to use language

Question 13

What are the potential mechanisms for aphasia?

Answer 13

Damage to Broca’s area or to Wernicke’s area

Question 14

What are some features of aphasia caused by damage to Broca’s area?

Answer 14

Also termed motor or expressive aphasia
Have difficulty in producing language
Do not usually have difficulty comprehending language

Question 15

What are some signs of expressive aphasia?

Answer 15

Often use few words

Only say most important word in a sentence

Question 16

What are some features of aphasia caused by damage to Wernicke’s area?

Answer 16

Also known as sensory or receptive aphasia
Have difficulty comprehending language
Can say words out of order or meaningless words

Question 17

What does maintenance of balance require?

Answer 17

Uses info from vision, proprioception and the vestibular apparatus

Question 18

What nerve is responsible for balance?

Answer 18

Vestibular nerve = CN VIII

Question 19

What are the connections of the vestibular nuclei?

Answer 19

Thalamus, cerebellum and spinal cord

Nuclei of CNs III, IV and VI

Question 20

How is vestibular info projected onto the cerebral cortex?

Answer 20

Bilaterally = less well defined than for other senses

Question 21

What are the areas that vestibular info has been found to converge?

Answer 21

Area of parietal cortex just posterior to area of postcentral gyrus that represents hand and mouth
Area just rostral to primary auditory cortex
Posterior insular cortex

Question 22

Is there an agreed region of the brain responsible for vestibular stimulation?

Answer 22

No

Question 23

What causes objects to be projected onto the retina reversed and upside down?

Answer 23

The lens

Question 24

Where would something present in the temporal visual field of the right eye be projected onto?

Answer 24

The nasal part of the right retina

Question 25

Where does each optic tract look?

Answer 25

At the contralateral visual field

Question 26

What makes up the visual pathway?

Answer 26

Optic tract, lateral geniculate nucleus, optic radiation, visual cortex

Question 27

Where is the lateral geniculate nucleus located?

Answer 27

In the visual cortex of the thalamus

Question 28

Where is the primary visual cortex located?

Answer 28

Posterior pole of the occipital lobe

Question 29

Where is the lower visual field projected?

Answer 29

To the gyrus superior to the calcarine sulcus

Question 30

Where is the superior visual field projected?

Answer 30

To the gyrus inferior to the calcarine sulcus

Question 31

Where does the macula project?

Answer 31

Posterior pole of the visual cortex = occupies a much greater proportion of cortex relative to the size of the visual field it covers

Question 32

What do the fibres of the geniculocalcarine tract form initially?

Answer 32

Part of the internal capsule

Question 33

What happens to fibres of the geniculocalcarine tract that are carrying visual info from the upper half of the visual field?

Answer 33

First loop anteriorly around the temporal part of the lateral ventricle in Meyer's loop = ends below the calcarine sulcus

Question 34

How does the visual cortex relate to eye movements?

Answer 34

Provides movements in response to visual stimuli

Question 35

What movements does the frontal eye field control?

Answer 35

Movements of command = movements that are independent of moving visual stimuli

Question 36

What are some characteristics of different eye movements?

Answer 36

Tracking movements tend to be smooth | Movements of command tend to be jumpy (saccadic)

Question 37

What happens in the pupillary light reflex?

Answer 37

Direct light reflex = pupil of eye light is shone into constricts Consensual light reflex = other pupil constricts

Question 38

How do pretectal fibres project into the Edinger-Westphal nucleus?

Answer 38

Bilaterally

Question 39

What does the accommodation reflex require?

Answer 39

Input to oculomotor and Edinger-Westphal nucleus from the visual cortex

Question 40

What is an hemianopia?

Answer 40

Blindness for half the field of vision in one or both eyes

Question 41

What is a homonymous visual defect?

Answer 41

Vision lost in same visual field in both eyes

Question 42

What is a heteronymous visual defect?

Answer 42

Vision lost on different visual fields in each eye?

Question 43

What is a dominant hemisphere?

Answer 43

Hemisphere that take the lead in a higher function, despite both hemispheres receiving similar inputs

Question 44

What functions is dominance high for?

Answer 44

Language functions

Question 45

For truly right handed people, what hemisphere is usually dominant for language?

Answer 45

The left hemisphere

Question 46

How are fibres in the white matter classified?

Answer 46

By origin and destination

Question 47

What are association fibres of white matter?

Answer 47

Connect cortical sites lying in the same hemisphere

Question 48

What are commissural fibres of white matter?

Answer 48

Connect one hemisphere to the other = usually connecting areas of similar function

Question 49

What are projection fibres of white matter?

Answer 49

Connect hemispheres to deeper structures including the thalamus, corpus striatum, brainstem and spinal cord