Auditory and visual pathways

Question 1

Name the auditory ossicles from lateral to medial

Answer 1

Malleus, incus and stapes (MIS)

Question 2

The ____ ____ has bipolar neurons stimulated by hair cells and carrying action potentials from organ of Corti to cochlear nuclei in the pons

Answer 2

Spiral ganglion

Question 3

Why is the input above the level of the cochlear nuclei essentially bilateral?

Answer 3

Superior to the cochlear nuclei some fibres are crossed and some are not, therefore input above this level is essentially bilateral

Question 4

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

Answer 4

Sound localisation and and as relays for stapedial and tensor tympani reflexes

Question 5

Name the areas labelled A-C

Answer 5

A - primary auditory cortex B - Wernicke’s area (auditory association cortex) C - Broca’s area

Question 6

Where do fibres carrying low frequency sound end in the auditory cortex?

Answer 6

Anterolateral part of the auditory cortex

Question 7

Where do fibres carrying high frequency sound end in the auditory cortex?

Answer 7

Posteromedial part of the auditory cortex

Question 8

How would a patient present with damage to their Broca’s area?

Answer 8

Patient’s have difficulty in producing language, often using few words and only saying the most important words in a sentence. They do not usually have difficulty comprehending language. Termed: Broca’s, motor or expressive aphasia

Question 9

How would a patient present with damage to Wernicke’s area?

Answer 9

Patient’s have difficulty comprehending language. These patients can manifest defects ranging from words out of order to meaningless words. Termed: Wernicke’s, sensory or receptive aphasia

Question 10

Maintenance of equilibrium/balance uses information from where?

Answer 10

Vision, proprioception and the vestibular apparatus (labyrinth)

Question 11

There is no agreed region of brain that is activated exclusively by vestibular stimulation (i.e. no primary vestibular cortex). However areas upon which vestibular information has been found to converge include …?

Answer 11

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

Question 12

Identify labels 1-3

Answer 12

1 = ciliary body 2 = choroid 3 = fovea centralis

Question 13

How are objects projected onto the retina?

Answer 13

Because of the lens, objects are projected onto the retina reversed and upside down

Question 14

Where in the visual field does each optic tract ‘look’?

Answer 14

Contralateral visual field

Question 15

Identify labels A-C

Answer 15

A = primary visual cortex B = visual association cortex C = primary visual cortex

Question 16

Where is the lower visual field projected to in relation to the calcacrine sulcus?

Answer 16

Projected to the gyrus superior to the calcacrine sulcus

Question 17

Where is the upper visual field projected to in relation to the calcacrine sulcus?

Answer 17

Projected to the gyrus inferior to the calcacrine sulcus

Question 18

Where does the macula project to in the visual cortex?

Answer 18

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

Question 19

Describe Meyer’s loop

Answer 19

Fibres of the geniculocalcacrine tract initially form part of the internal capsule. Those carrying visual information from the upper half of the visual field first loop anteriorly around the temporal part of the lateral ventricle in Meyer’s loop ending below the calcacrine sulcus

Question 20

What do the frontal eye fields control (in relation to eye movement)?

Answer 20

Control movements of command, that is movements that are independent of moving visual stimuli

Question 21

What is the difference between tracking eye movements and movements of command?

Answer 21

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

Question 22

Desribe the pupillary light reflex

Answer 22

Shine light into right eye, right pupil constricts = direct light reflex

Left pupil constricts = consensual light reflex (note that the pretectal fibres project bilaterally to the Edinger-Westphal nucleus)

Question 23

Describe the accomodation reflex

Answer 23

The accomodation reflex = convergence of gaze, contraction of ciliary muscles, pupillary constriction

It requires input to oculomotor and Edinger-Westphal nucleus from the visual cortex

Question 24

If a patient had blindness in the left temporal and right nasal fields, what would this lesion be called?

Answer 24

Right homonymous hemianopia

Question 25

If a patient had a lesion in their right optic nerve how would they present?

Answer 25

Right monocular blindness

Question 26

Define hemianopia

Answer 26

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

Question 27

In some higher functions one cerebral hemisphere takes the lead and is referred to as the dominant hemisphere. Which function is generally high in terms of dominance?

Answer 27

Language functions - for most truly right-handed people, the left hemisphere is usually dominant for language

Question 28

Name the 3 types of fibre in the white matter of the cerebral hemispheres

Answer 28

Association fibres (blue), commissure fibres (green) and projection fibres (red)

Question 29

What do each type of white matter fibre do?

Answer 29

Association fibres (blue) connect cortical sites lying in the same hemisphere

Commissural fibres (green) connect one hemisphere to another, usually connecting areas with similar function

Projection fibres (red) connect hemispheres to deeper structures including thalamus, corpus striatum, brain stem and spinal cord