CHP. 3 - Visual Perception

Question 1

Points of refraction in eye

Answer 1

1. Cornea
2. Lens
   * Contacts/glasses add an extra refraction point

Question 2

Where is the focal point of light in the eye?

Answer 2

Fovea

Rods & cones

Question 3

Pathway of light into the eye

Answer 3

1. Light
2. Cornea
3. Lens
4. Retina

Question 4

Rods

Answer 4

• Color-blind
• Sensitive in low light levels
• Lower acuity
• None in fovea

Question 5

Cones

Answer 5

• Color-sensitive
• Can’t function in dim light
• Higher acuity
• Mostly in/near fovea

Question 6

Color perception problems

Answer 6

Color “blindness” or deficiency
* Due to overlap in cone sensitivities
* More common in males

Question 7

Retina visual pathway

Right up to optic nerve

Answer 7

1. Photoreceptors (rods & cones)
2. Bipolar cells
3. Ganglion cells
4. Optic nerve

Question 8

Brain visual pathway

Answer 8

1. Optic nerve
2. Optic chasm (optic nerves cross over)
3. Optic tract to LGN of thalamus
4. Optic radiations to V1 (visual cortex) in occipital lobe

Question 9

Primary visual cortex

Answer 9

(aka) V1
* receives info from LGN in thalamus
* in occipital lobe

Question 10

Emmetropia

Vision

Answer 10

Happy condition of no refractive error

Question 11

Myopia

Vision

Answer 11

Near-sightedness
* When the light entering the eyes is focused in front of the retina & distant objects can’t be seen sharply

Question 12

Hyperopia

Vision

Answer 12

Far-sightedness
* When light entering the eye is focused behind the retina

Question 13

Presbyopia

Vision

Answer 13

“Old sight”
* Hardening of the crytal lens
* Lens becomes harder & capsule that encircles the lens loses its elasticity
* Can’t focus on things as closely

Question 14

Astigmatism

Answer 14

Visual defecting involving unequal curving of 1 or more of the refractive surfaces of the eye (usually the cornea)

Question 15

Cataracts

Answer 15

Cloudy lens - loss of transparency in lens

Question 16

Lateral inhibition

Answer 16

When cells are stimulated, they inhibit the activity of neighboring cells
* Results in edge enhancement

Question 17

Visual field

Answer 17

External stimuli
* Field of view
* Divided into left & right

Question 18

Receptive field

Answer 18

The area that causes an increase/decrease in a firing rate of a cell when stimulated

Question 19

Retinal receptive fields

Answer 19

Smaller in fovea (cones)
Larger in periphery (rods)
* Organized into Center-Surround
* On-Center
* Off-Center

Question 20

Parallel processing

Answer 20

1. Brain divides stimuli into separate components
2. Processes each component separately
3. Perception if formed by integrating them together

Question 21

Summary of visual info processing

Answer 21

1. Scene
2. Retinal processing
3. Feature detection
4. Parallel processing
5. Recognition

Question 22

Advantages of parallel processing

Answer 22

1. Speed & efficiency
2. Mutual influence among multiple systems

Question 23

Serial processing

Answer 23

Steps are done one at a time (bottom-up)

Question 24

What system (Ventral pathway)

Answer 24

Connects occipital lobe & inferotemporal cortex
* Aids in ID of visual objects (object)
* Damage = visual agnosia

Question 25

*Where* system (Dorsal pathway)

Answer 25

Connects occipital lobe & posterior parietal cortex * Aids in perception of object's location (spatial) * Damage = difficulties reaching for objects

Question 26

Binding problem

Answer 26

Task of reuniting elements of a stimulus that were addressed by different systems in different brain regions

Question 27

Elements that help with the binding problem

Answer 27

1. Spatial position 2. Neural synchrony 3. Attention

Question 28

Reversible (ambigous) figures

Answer 28

One set of visual features results in multiple interpretation | ex. young woman vs. old woman, duck vs. bunny

Question 29

Perceptual constancy

Answer 29

We perceive constant object properties (sizes, shapes, etc) even though sensory info can change viewing circumstances change * Brightness/size/shape constancy

Question 30

Accomodation | Depth

Answer 30

Eye changes its focus (lens gets fatter as gaze is directed toward nearer objects)

Question 31

Convergence | Depth

Answer 31

Ability of the 2 eyes to turn inward (used to focus on nearer objects)

Question 32

Divergence | Depth

Answer 32

Ability of the 2 eyes to turn outward (used to focus on farther objects)

Question 33

Monocular depth cue | Depth/distance

Answer 33

Cue available even when the world is viewed with only 1 eye

Question 34

Binocular depth cue | Distance/depth

Answer 34

Cue that relies on info from both eyes

Question 35

Motion cue

Answer 35

Cue available when object is moving

Question 36

Binocular disparity | ex. finger exercise

Answer 36

Difference between each eye's view of a stimulus * Can lead to perception of depth in absence of other cues

Question 37

Motion parallax

Answer 37

Projected images of nearby objects move more than distant ones across retinas

Question 38

Optic flow

Answer 38

As you move toward/away from an object, the pattern of stimulation across the entire visual field changes

Question 39

Akinetopsia

Answer 39

Inability to detect motion, causing moving objects to appear as if they are jumping from one stationary position to another * "Motion blindness" * Linked to Area V5