chapter 13: the occipital lobe and its functions

Question 1

What is the anatomical name of the primary visual cortex? Which Brodmann Area is it?

Answer 1

Calcarine sulcus, BA 17.

Question 2

What are ‘blobs’? What do they do?

Answer 2

Structures (different cell types) within V1 that process colour information.

Question 3

What structures in V1 process form and motion?

Answer 3

Interblobs.

Question 4

What function is each stripe in V2 responsible for processing?

Answer 4

Thin stripes: colour perception
Thick stripes: form information
Pale stripes: motion perception

Question 5

What are the three streams projecting from V2 to major visual areas? What are functions are they responsible for?

Answer 5

Dorsal stream: visual guidance of movement
Superior temporal sulcus (STS) stream: object perception and motion perception
Ventral stream: object perception and motion perception

Question 6

What are higher visual areas (V3-V5) responsible for processing?

Answer 6

V3: dynamic form, shapes in motion
V4: colour information
V5: motion processing; MT

Question 7

Which disorder is caused by damage to V4?

Answer 7

Achromatopsia.

Question 8

Which disorder is caused by damage to V5?

Answer 8

Akinetopsia.

Question 9

Damage to __ results in blindness, damage to __________ __________ results in deficits in specific functions.

Answer 9

V1, higher areas

Question 10

In patients with V1 damage, smaller projections from subcortical areas provide some limited vision. This is an example of what phenomenon?

Answer 10

Blindsight.

Question 11

The dorsal and ventral pathways are responsible for (perception/action) and (perception/action) accordingly.

Answer 11

action, perception

Question 12

The lateral occipital, fusiform face area, and extrastriate body area, are all regions belonging to the (dorsal/ventral) stream.

Answer 12

ventral

Question 13

the lateral intraparietal sulcus, ventral intraparietal sulcus, and parietal reach region, are al regions belonging to the (dorsal/ventral) stream.

Answer 13

dorsal

Question 14

What is egocentric space vs allocentric space? Which does/do the visual system guide movements by?

Answer 14

Egocentric space: objects organized in relation to the observer
Allocentric space: objects organized in relation to each other

Visual system encodes both perspectives to guide movement and to remember scenes.

Question 15

Visually guided movements project from __ to __________ __________ via __________ stream.

Answer 15

V1, parietal areas, dorsal

Question 16

Patients with damage to __________ occipital area could shape hand, could not consciously see.

patients with damage to __________ __________ can see objects, could not accurately reach.

Answer 16

lateral, dorsal stream

Question 17

Parietal lesions that impact visual areas typically characterized as __________ or __________.

Answer 17

visuospatial, visuomotor

Question 18

Posterior parietal visual neurons are only active when brain is __________, not __________.

Answer 18

acting, looking

Question 19

Comparison of faces is processed by the __________ __________ area in __________ lobe.

Answer 19

fusiform face area, temporal

Question 20

Imaging studies show increased activity in __ when subjects asked to detect motion, __ when asked to detect colour.

Answer 20

V4, V5

Question 21

What is the name of the site at which visual inputs (optic nerves) cross?

Answer 21

The optic chiasm.

Question 22

Where in the brain are binocular visual inputs combined?

Answer 22

V1, calcarine sulcus

Question 23

What is macular sparing?

Answer 23

The phenomenon of information in central part of visual field being spared in cases of visual cortex damage.

Question 24

What are scotomas?

Answer 24

Small blind spots in visual fields; are often unnoticed due eyes constantly moving, and brain performing compensation via previous inputs.

Question 25

H.M.’s bilateral lobotomy indicated the function of which brain region? What was the is the function of the region?

Answer 25

Hippocampus, memory.

Question 26

B.K.’s damage to their V1 resulted in what symptom(s)?

Answer 26

Temporary loss of vision in left visual field, permanent loss in lower-left field; blindsight in affected areas.

Question 27

D.B.’s damage to V1 resulted in what symptom(s)?

Answer 27

Blindsight: no conscious awareness of visual stimuli, but can accurately indicate descriptors.

Question 28

What is significant about B.I.’s childhood occipital lobe damage?

Answer 28

By age 6, not blind; can recognize faces and colours, navigate environment.

Plasticity to rearrange visual system and strengthen pathways from subcortical areas to V5.

Question 29

Describe J.I.’s achromatopsia.

Answer 29

World appeared in greyscale following accident. Lost ability to remember or imagine colours, even in dreams.

Implication that imagination is tied to perceptive capabilities.

Question 30

What is significant about P.B.’s blindness compared to J.I.?

Answer 30

Despite blindness, retained ability to imagine colour. Likely due different mechanism/location of damage.

Question 31

Describe L.M’s akinetopsia.

Answer 31

Lost ability to detect motion due damage to V5. Vision otherwise normal.

Question 32

Describe D.F.’s visual agnosia.

Answer 32

Inability to recognize objects, pictures of objects; inability to draw copy of objects. Due carbon monoxide poisoning damaging lateral occipital (LO).

Question 33

D.F’s visual agnosia affected which occipital stream? Which functions were retained?

Answer 33

Damage to ventral stream (visual recognition).

Dorsal stream reaching/grasping left intact.

Question 34

Describe V.K.’s optic ataxia. Which functions were retained?

Answer 34

Deficit in visually-guided movements, such as reaching due bilateral stroke in occipito-parietal regions.

Ventral stream visual recognition left intact.

Question 35

Describe D’s prosopagnosia.

Answer 35

Inability to recognize familiar faces due lesion to right occipitotemporal region.

Question 36

Describe T’s alexia.

Answer 36

Loss of ability to read due lesion to left occipitotemporal region.

Question 37

What is the significance of D and T’s lesions compared to each other?

Answer 37

Both have lesions to occiptotemporal regions, retention of each others’ lost functions indicates full lateralization of reading and facial recognition.

Question 38

Describe apperceptive agnosia.

Answer 38

Failure to recognize basic feature of object (e.g. colour or motion).

Question 39

Describe simultagnosia.

Answer 39

Inability to perceive more than one object at a time despite ability to perceive individual objects.

Question 40

Apperceptive agnosia and simultagnosia often result from damage to what areas?

Answer 40

Bilateral damage to lateral occipital.

Question 41

Describe associative agnosia.

Answer 41

Inability to recognize object despite ability to perceive it. Typically due damage to ventral stream (e.g. D.F.)

Question 42

Alexia is caused by damage to which areas?

Answer 42

Left fusiform gyrus and lingual area.

Question 43

Which area is responsible for mental rotation of visual images?

Answer 43

Right-hemisphere dorsal stream areas.