Neuroanatomy 5: Visual and Auditory Pathways

Question 1

Which CN is involved in hearing?

Answer 1

CN VIII - Cochlear nerve

Question 2

What route is taken by the cochlear nerve to reach the thalamus?

Answer 2

ECOLI
Cochlear nerve (EIGHTH CN) -->
Cochlear nucleus (C) -->
Superior olivary nucleus (O)-->
(LATERAL LEMNISCUS)
Inferior collicus (I) -->
Medial geniculate body (in thalamus)

Question 3

A unilateral hearing problem is typically an issue with the cochlea. True/ False?

Answer 3

False
Typically, a brainstem issue
Superior to cochlear nuclei, some fibres are crossed and some are not = bilateral input

Question 4

What are the auditory ossicles of the middle ear?

Answer 4

Malleus, incus and stapes

Question 5

What is contained within the organ of corti in the cochlea?

Answer 5

Inner and outer hair cells

Question 6

What is the role of the spiral ganglion within the cochlea?

Answer 6

Bipolar neurones that are stimulated by hair cells and carry action potentials from organ of corti to cochlear nuclei in pons

Question 7

Where is the primary auditory cortex in the brain - in terms of lobes and fissures?

Answer 7

Temporal lobe

Close to lateral fissure

Question 8

What area of the auditory cortex do low frequency fibres end, versus high frequency fibres?

Answer 8

Anterolateral

Posteromedial

Question 9

What is the function of the superior olivary nucleus and lateral lemniscus in hearing?

Answer 9

Sound localization and relays info for stapedial and tensor tympani reflexes

Question 10

What is aphasia? Which side of the brain is dominant for language?

Answer 10

Inability to use language

Left predominantly

Question 11

What would we expect to happen if there was damage to Broca’s area? Where is Broca’s area?

Answer 11

MOTOR/ EXPRESSIVE APHASIA
Difficulty in producing language - typically few words/ most important (‘broken’)
Frontal lobe

Question 12

What would we expect to happen if there was damage to Wernicke’s area? Where is Wernicke’s area?

Answer 12

SENSORY/ RECEPTIVE APHASIA
Difficulty comprehending language - words out of order/ meaningless words
Temporal lobe

Question 13

Which CN is involved in balance?

Answer 13

CNVIII - vestibular nerve

Question 14

Which part of the inner ear is involved in balance?

Answer 14

3 semicircular canals

Question 15

What are the main connections of vestibular nuclei?

Answer 15

Thalamus
Nuclei of CN III, IV, VI (Eye control)
Cerebellum (flocculonodular lobe)
Spinal cord

Question 16

There is no ‘vestibular cortex’, where does the projection of vestibular information typically converge?

Answer 16

Parietal cortex/ posterior to postcentral gyrus that represents hand and mouth)
Anterior to primary auditory cortex
Posterior insular cortex

Question 17

What part of the thalamus is involved in processing visual information?

Answer 17

Lateral geniculate nucleus

Question 18

Each optic tract, LGN, optic radiation and visual cortex deals with visual information from the contralateral/unilateral field.

Answer 18

Contralateral

Question 19

What is the role of the superior cocculi in vision?

Answer 19

Recieve inputs and outputs to nuclei of CN III, IV, VI and motor nucleus of VII and spinal cord
Mostly involved in ‘automatic vision’

Question 20

Where is the primary visual cortex located in the brain - in terms of lobes and fissures?

Answer 20

Occipital lobe

Above and below the calcarine sulcus

Question 21

Which visual field is projected to gyrus superior to the calcarine sulcus?

Answer 21

Lower visual field

Upper projects to inferior

Question 22

Which pole of the cortex does the macula project to?

Answer 22

Posterior pole (occupies large proportion)

Question 23

What is Meyer’s loop?

Answer 23

Fibres of geniculocalcarine tract that form part of the internal capsule
Visual information from upper half of field first loop anteriorly around temporal part of lateral ventricle

Question 24

What type of eye movement is the visual cortex involved in?

Answer 24

Movements in response to visual stimuli (tracking moving objects) - SMOOTH

Question 25

What type of eye movement is the frontal eye fields involved in?

Answer 25

Movements of command (no moving visual stimuli) - JUMPY

Question 26

In the consensual light reflex, what is the mechanism behind the constriction of the contralateral pupil?

Answer 26

Pretectal fibres project bilaterally to EW nucleus

Question 27

In the accommodation reflex, what receives inputs from the visual cortex?

Answer 27

Oculomotor nerve

EW nucleus

Question 28

What is the route for sympathetic nerve supply to the eye?

Answer 28

T1 sympathetic trunk ganglion --->
Superior cervical sympathetic ganglion --->
Internal carotid plexus --->
Ciliary ganglion --->
Short ciliary nerve

Question 29

Why is the macula spared in occipital lobe lesions affecting vision?

Answer 29

There is dual blood supply from posterior and anterior cerebral arteries

Question 30

Where are the medial and lateral olives located?

Answer 30

Two small ovals on the medulla