Occipital lobes

Question 1

Anatomical location and regions

Answer 1

posterior part of the brain:

occipital gyri with streams reaching into the temporal and parietal lobes

Question 2

3 main regions divided into 6 subregions

Answer 2

BA 17, 18, 19
divided into
V1, V2, V3 (dorsal and ventral), V4 and V5 (middle temporal visual area MT)

Question 3

Anatomy V1

Answer 3

10 cortical layers

staining cytochrome oxidase (enzyme largely involved in areas that process colour) to reveal various cell functions

Question 4

blob

Answer 4

darkly stained cells in layers 2-3 of V1

- high activity of cytochrome oxidase: cells involved in colour perception

Question 5

interblob

Answer 5

white cells after staining in layers 2-3 of V1

- little activity of cytochrome oxidase: no involvement in colour perception

Question 6

Visible spectrum

Answer 6

relatively small for humans but nevertheless allows the distinction of a vast amount of colours based on light wave frequency

Question 7

Colour cells

Answer 7

involved in colour perception, distinguish light wavelengths

Question 8

Simple cells

Answer 8

involved in perceiving sources of light, different neurons fire for specific locations

Question 9

Orientation cells

Answer 9

involved in orientation of light, different neurons fire for specific orientations

Question 10

Direction cells

Answer 10

involved in motion perception, different neurons fire for different directions of motion

Question 11

Features of staining V2 with cytochrome oxidase

Answer 11

reveals stripes:

1) thin stripes: majority of colour cells
2) thick stripes: majority of orientation cells
3) pale stripes: majority of direction cells

Question 12

V4

Answer 12

part of the ventral stream
mostly orientation and colour cells
involved in recognition of colour and form

Question 13

V5/MT (middle temporal visual area)

Answer 13

part of the dorsal stream
mostly direction cells
involved in processing motion

Question 14

MST (medial superior temporal lobe)

Answer 14

located in the parietal cortex
includes selective cells for
- linear motion
- radial motion (in and out)
- circular motion (anti and clockwise)

Question 15

Case of bk (effect of damage to V1)

Answer 15

• after lesion to right occipital area bk was blind in their upper left visual field
• blindness developed as dark, followed by “visual noise”, movement being perceived as waves and no perception of form or pattern
• later blindness improved but “snow” remained and impaired colour and motion perception and reading difficulties

Question 16

Case of db (effect of damage to V1): blind sight

Answer 16

• reports no vision in left visual field but when prompted can locate exactly the source of light

Question 17

Case of JI (effect of damage to V4)

Answer 17

complete colour blindness

no colour perception in dreams

Question 18

Case of LM (effect of damage to V5)

Answer 18

loss of movement vision

cannot perceive fluidity of movements

Question 19

Case of VK (damage to the parietal lobe)

Answer 19

difficulty reaching for objects, impaired egocentric representation

Question 20

Case of DF (damage to the inferotemporal lobe)

Answer 20

unable to copy drawings of objects but no memory impairment

could draw objects correctly from memory