Vision

Question 1

% of the cerebral cortex plays a direct role in processing visual information

Answer 1

20

Question 2

energy detectable to human eye

Answer 2

electromagnetic

Question 3

3 layers of retina

Answer 3

• photoreceptors (rods and cones), at back of retina
• bipolar cells (transparent)
• ganglion cells (transparent), surface of retina, sends axons out of eye

Question 4

photoreceptors: rods

Answer 4

• more numerous
• more in periphery
• sensitive to small changes in light intensity/shading
• mediate vision in dim illumination
• more outlines and contours than details

Question 5

photoreceptors: cones

Answer 5

• fewer
• concentrated in central area (fovea)
• sensitive to color
• higher resolution visual discrimination, fine details

Question 6

fovea

Answer 6

central area of retina that contains only cones and has greatest visual acuity

Question 7

optic disk

Answer 7

where ganglion cell axon exit eye in optic nerve; contains no photoreceptors and creates a blind spot

Question 8

main pathway of visual stimuli

Answer 8

eye > 
optic nerve > 
optic chiasm > 
optic track > 
lateral geniculate nuclei in thalamus, sends optic radiations to >
primary visual cortex / striate cortex >
association visual cortex

Question 9

second pathway of visual stimuli

Answer 9

eye > 
optic nerve > 
optic chiasm > 
superior colliculus > 
thalamus > 
secondary visual cortex (V5)
- for orientation of head and eyes toward new stimuli in periphery

Question 10

third pathway of visual stimuli

Answer 10

eye > 
optic nerve > 
optic chiasm > 
hypothalamus
- for control of circadian rhythms

Question 11

receptive field

Answer 11

the area in the visual field a neuron responds to

Question 12

photoreceptors-to-ganglion cell ratio

Answer 12

• nearly one-to-one correspondence in fovea

- many receptors connect with single neuron in periphery

Question 13

optic chiasm

Answer 13

• neurons carrying information from medial half of visual field (inner / nasal) cross to contralateral hemisphere
• ipsilateral visual info from each side crosses and goes to other hemisphere
• contralateral visual info from each side stays in same hemisphere

Question 14

left visual field

Answer 14

• left half of visual field in each eye
• seen by right half of retina
• processed by right hemisphere

Question 15

right visual field

Answer 15

• right half of visual field in each eye
• seen by left half of retina
• processed by left hemisphere

Question 16

lateral geniculate nucleus (LGN)

Answer 16

• in thalamus
• 6 layers
• receptive field organization is reflected in LGN organization
• segregates visual information
• optic radiations project from LGN to primary visual cortex
• segregation of information transmitted is preserved in the cortex

Question 17

optic radiations

Answer 17

info projected from LGN to primary visual cortex

Question 18

map of primary visual cortex

Answer 18

visual field is represented in a topographic map on the cortex

1. Contralaterally represented
2. Upside down
   - Upper visual field processed in inferior primary cortex
   - Lower visual field processed in superior visual cortex
3. Central – peripheral
   - Central visual field processed in posterior primary visual cortex
   - Peripheral visual process in anterior primary visual cortex

Question 19

% of primary visual cortex process info from fovea

Answer 19

25

Question 20

primary visual cortex / striate cortex / V1

Answer 20

color, form, and movement are processed separately
Composed of 1000s of modules, which consist of:
- blobs: color
- interblobs: orientation, movement
Some neurons are sensitive to orientation and only respond to certain line angles

Question 21

cortical blindness

Answer 21

aka blind sight
conscious blindness is in the part of the visual field that damaged part of the cortex corresponds to
visually mediated bx still possible

Question 22

V2

Answer 22

V1 projects to V2, an area of extrastriate cortex (region of visual association cortex that surrounds striate cortex)
Information segregation (color, form, movement) happens in V1 then projects to V2
V2 maintains segregation of info (important)

Question 23

association visual cortex

Answer 23

Fragmented component processing of primary visual cortex and V2 is transmitted to visual association areas where it is integrated into perception

Question 24

Two visual pathways after primary visual cortex (V1 and V2)

Answer 24

1. dorsal – WHERE – parietal lobe, perception of spatial location and self-movement
2. ventral – WHAT – temporal lobe, perception of objects and color, identification of things

Question 25

V4

Answer 25

- visual association cortex in occipital lobe - part of ventral stream of visual info (V2 to V4) - processes color and form - neurons respond to specific color - some to color in a specific orientation, indicating this area mediates form and color perception - damage to V4 in humans results in impaired color perception and color constancy

Question 26

V8 (or TEO)

Answer 26

- area in temporal lobe anterior to V4 - also involved in color discrimination - Damage to V8 in humans results in loss of color vision but not form perception - neuron receptive fields are larger than V4 and smaller than TE - primary input from V4 - primary output to TE - damage impairs monkeys’ ability to make even simple visual discriminations of form, size, orientation, color or brightness

Question 27

location of integration for 3-D, object, and background perception

Answer 27

TEO and TE | inferior temporal lobe

Question 28

TE

Answer 28

usually referred to as inferior temporal lobe - 2nd level of visual assoc cortex, involved in processing most complex visual information - recognition of objects is based on patterns - neurons respond best to 3-D objects or photos of them, poorly to spots, lines, etc. and continue to respond if object is moved or changed in size, shape, brightness, etc. - neurons are arranged in columns with neurons in adjacent regions responding to slightly different versions of the same object (tiger perception separated out into more basic shapes/color) - largest receptive fields, often an entire contralateral half of visual field

Question 29

visual agnosia

Answer 29

1. Visual acuity intact 2. No dementia 3. Cannot identify objects by sight 4. Can identify objects by other sensory modalities

Question 30

apperceptive visual agnosia

Answer 30

failure in higher level perception a. perceptual impairment and visual agnosia (can’t copy figures or recognize objects) b. bilateral lateral occipital damage

Question 31

associative visual agnosia

Answer 31

disconnect btwn perception and verbal systems a. perception intact (can copy figures) with visual agnosia (can’t recognize objects) b. damage in the anterior ventral/temporal stream

Question 32

lateral occipital cortex

Answer 32

large region of ventral visual association area that responds to a large variety of objects and shapes

Question 33

fMRI study found only three regions that showed greater activation to specific categories

Answer 33

faces bodies scenes

Question 34

fusiform face area (FFA)

Answer 34

- visual association area on inferior surface of temporal (and occipital) lobes in R hemisphere - part of ventral stream - Separate specialized neural circuits that mediates face recognition - FFA is influenced by experience; activated in people who are experts in viewing something: bird experts, car experts, dog judges - People are better able to recognize faces of their own race

Question 35

prosopagnosia

Answer 35

impaired ability to recognize familiar faces and learn new faces - Developmental prosopagnosia

Question 36

extrastriate body area (EBO)

Answer 36

- posterior to FFA - most activated to bodies and parts of bodies and not other objects - intermediate activation to faces

Question 37

parahippocampal place area

Answer 37

activated by scenes and backgrounds

Question 38

V5 (MT)

Answer 38

- V5 (or MT for medial temporal) mediates perception of movement - receives input from primary visual cortex, other areas of visual association cortex, superior colliculus - neurons are more heavily myelinated and input arrives faster to V5 than to V4 - V5 neurons responded best to movement and many are sensitive to movement in a particular direction - bilateral damage in humans results in impaired perception of movement; disruption of V5 with TMS impairs perception of movement without affecting perception of form - Patterns of movement can also give rise to perception of 3-D form - these abilities can be dissociated in brain injury in humans, with V5 damage can have: - impaired perception of movement without impairment of form perception based on movement - or accurate perception of movement but impaired perception of form based on movement

Question 39

V5a (MST)

Answer 39

V5a or MST (medial superior temporal) adjacent to V5 receives input from V5 and is sensitive to complex movements i.e. circular, radial, spiral - MST also important in analysis of optic flow

Question 40

analysis of optic flow

Answer 40

- V5a or MST important - analysis of the relative movements of visual elements in the environment; e.g. when walking, some objects move to the R, L, up or down in your visual field - analysis of optic flow allows you to determine what direction you are going, how fast you are approaching objects and if they will pass on the R, L, above or below

Question 41

dorsal visual stream

Answer 41

- posterior parietal - V5 projects to the posterior parietal area (intraparietal sulcus), area mediates visually guided movements, about where things are located a. extensive connections with frontal eye fields and areas controlling hand and arm movements b. bilateral damage impairs person’s ability to assume the proper hand position when reaching for an object - posterior parietal also involved in mental construction of 3-D images, along with visual association cortex (extrastriate) and dorsal prefrontal (planning movements)

Question 42

blobs

Answer 42

in V1 modules, process color

Question 43

interblobs

Answer 43

in V1 modules, process orientation, form, movement

Question 44

processing pathway, starting with V1

Answer 44

V1, primary visual cortex, blobs and interblobs > to V2, extrastriate cortex, segregation is maintained then to V4 or V5 > V4, visual association cortex, color and form, beginning of perception, then ventral stream (what): - to V8/TEO, integration of color/form for 3D, object, and background perception - to TE, second level of visual assoc cortex, involved in processing most complex visual info, 3D objects > V5, detects/distinguishes movement, then dorsal stream (where) to V5a/MST and to posterior parietal, interparietal sulcus, mediating visually guided movements