W2

Question 1

How does our visual experience appear to us?

Answer 1

High-definition, three-dimensional, colorful, and in motion.

Question 2

What is a common misconception about vision?

Answer 2

That we see a high-resolution, right-side-up image.

Question 3

What is the reality of the retinal image?

Answer 3

It is low resolution, upside down, and flipped side to side.

Question 4

How does the brain compensate for the limitations of the retina?

Answer 4

It constructs perception from compressed and incomplete data.

Question 5

What is the fovea, and what is its function?

Answer 5

The fovea is the high-resolution center of vision.

Question 6

What is the blind spot, and why does it exist?

Answer 6

It is an area with no photoreceptors due to the optic nerve exit.

Question 7

What are the two types of photoreceptors, and their functions?

Answer 7

Rods: night vision, motion detection, no color. Cones: daylight vision, color perception, detail.

Question 8

Why isn’t the entire retina high resolution?

Answer 8

It would require too many photoreceptors and a much larger optic nerve, creating a massive blind spot.

Question 9

What part of the retina is high resolution?

Answer 9

Only the fovea.

Question 10

How does the retina solve energy constraints?

Answer 10

By compressing data and prioritizing important changes in vision.

Question 11

What is a receptive field?

Answer 11

The area of the retina that a specific photoreceptor or neuron responds to.

Question 12

How do retinal ganglion cells process information?

Answer 12

They gather signals from multiple photoreceptors and detect small fragments of the image.

Question 13

How does each photoreceptor contribute to vision?

Answer 13

Each receives a small portion of visual information, which together forms the complete scene.

Question 14

What are the center-surround properties of receptive fields?

Answer 14

Some areas enhance signals while others inhibit them, helping with contrast detection.

Question 15

What is the output of the retina?

Answer 15

Retinal ganglion cells, which send visual information to the brain via the optic nerve.

Question 16

How is visual information processed through the retina?

Answer 16

Photoreceptors → Bipolar cells → Retinal ganglion cells → Optic nerve.

Question 17

What is lateral inhibition?

Answer 17

A process where certain cells suppress their neighbors to enhance contrast and compress data.

Question 18

Which cells are responsible for lateral inhibition in the retina?

Answer 18

Amacrine cells and horizontal cells.

Question 19

Why is lateral inhibition important for vision?

Answer 19

It enhances contrast and reduces unnecessary information.

Question 20

What is the role of retinal ganglion cells (RGCs) in the eye?

Answer 20

They serve as the output neurons, transmitting visual information to the brain.

Question 21

What are the two main types of RGC receptive fields?

Answer 21

On-Center, Off-Surround and Off-Center, On-Surround.

Question 22

How do On-Center, Off-Surround RGCs respond to light?

Answer 22

Center light → excitation; surround light → inhibition; no light → baseline; full-field → averages out.

Question 23

Why do On-Center, Off-Surround cells act like switches?

Answer 23

Their response depends on which part of the field is stimulated.

Question 24

How do Off-Center, On-Surround RGCs respond to light?

Answer 24

Center light → inhibition; surround light → excitation.

Question 25

Why does the brain prioritize transmitting only important visual information?

Answer 25

To save energy by focusing on changes across space (edges) and time (motion).

Question 26

What is lateral inhibition in vision?

Answer 26

A process where neighboring neurons inhibit each other, enhancing edges and contrast.

Question 27

How does lateral inhibition affect color perception?

Answer 27

Neurons inhibit neighbors with the same color input, making central colors appear darker or lighter.

Question 28

Why does a line appear darker against a lighter background and lighter against a darker background?

Answer 28

Due to center-surround antagonism altering inhibition levels.

Question 29

What is the simultaneous contrast illusion?

Answer 29

Brightness of an object appears different depending on its surrounding background luminance.

Question 30

What are the two types of ganglion cells, and how do they respond to light?

Answer 30

On-Center: center activation, surround inhibition. Off-Center: surround activation, center inhibition.

Question 31

Why does a grey bar appear lighter on a dark background and darker on a light background?

Answer 31

Background-dependent inhibition levels change perceived brightness.

Question 32

How does the visual system enhance contrast?

Answer 32

By emphasizing edges using center-surround antagonism in RGCs.

Question 33

What is "filling-in" in visual perception?

Answer 33

The brain’s process of completing missing information for seamless perception.

Question 34

Why do ganglion cells primarily respond to edges?

Answer 34

To optimize energy use and processing efficiency.

Question 35

How does the brain interpret sharp edges in an image?

Answer 35

It perceives them as gradual gradients, leading to shading illusions.

Question 36

What is the Craik-O’Brien-Cornsweet illusion?

Answer 36

An edge creates the perception of a gradient where none exists.

Question 37

Why does the Craik-O’Brien-Cornsweet illusion occur?

Answer 37

Ganglion cells detect only edges, so the brain fills in uniform areas.

Question 38

How does this illusion relate to efficient visual processing?

Answer 38

The retina prioritizes edge detection, letting the brain infer shading.

Question 39

How does the retina process images differently from conscious perception?

Answer 39

It enhances edges and discards uniform areas, requiring reconstruction.

Question 40

What is center-surround antagonism, and how does it contribute to edge detection?

Answer 40

Cells excited by center light and inhibited by surround light, sharpening edges.

Question 41

What happens to most ganglion cells when there is no significant light change?

Answer 41

They remain inactive, responding only to changes.

Question 42

What is the watercolor illusion?

Answer 42

Incomplete contours or colors appear filled in by the brain.

Question 43

Why is the Craik-O’Brien-Cornsweet illusion important for AI and image compression?

Answer 43

It shows perception can be reconstructed from minimal edge data.

Question 44

Why does the brain ignore information that stays constant over time?

Answer 44

To conserve energy by inhibiting neurons for unchanging stimuli.

Question 45

What is lateral inhibition’s role in after-effect illusions?

Answer 45

It reduces constant-stimulus neuron activity, causing afterimages when removed.

Question 46

Why do we see afterimages in complementary colors?

Answer 46

Fatigued neurons fail to respond, leaving opposite-color neurons active.

Question 47

What happens when you stare at red for a long time and then look at white?

Answer 47

Red-sensitive neurons are fatigued; white appears green/blue.

Question 48

What is Troxler fading?

Answer 48

A peripheral stationary stimulus fades over time due to neural adaptation.

Question 49

How does Troxler fading work?

Answer 49

Neural adaptation + filling-in effect + lack of sharp edges lead to fading.

Question 50

What causes negative after-images?

Answer 50

Previously inhibited neurons remain suppressed when stimuli are removed.

Question 51

What do after-effect illusions reveal about perception?

Answer 51

Vision relies on adaptation and contrast mechanisms, not absolute signals.

Question 52

Why is neural adaptation important for efficient vision?

Answer 52

It filters out redundant information, focusing on changes.

Question 53

What is the function of the Lateral Geniculate Nucleus (LGN)?

Answer 53

It relays retinal signals to V1 and processes color, motion, depth.

Question 54

How many layers does the LGN have?

Answer 54

Six layers, each mapping half the visual field.

Question 55

What is the function of the Parvocellular (P) layers in the LGN?

Answer 55

Color and fine detail from the fovea; slow response; red-green processing.

Question 56

What is the function of the Magnocellular (M) layers in the LGN?

Answer 56

Motion and depth from peripheral retina; fast response.

Question 57

What do Koniocellular (K) cells specialize in?

Answer 57

Blue-yellow color processing.

Question 58

How is visual information mapped in the LGN?

Answer 58

A 1:1 spatial mapping preserving retinal organization.

Question 59

Why does the LGN separate color and motion processing?

Answer 59

To deconstruct inputs and send specialized streams to V1.

Question 60

How is visual information divided at the optic chiasm?

Answer 60

Left LGN processes the right visual field; right LGN processes the left.

Question 61

Do individual LGN cells receive binocular vision?

Answer 61

No; each cell gets input from only one eye for one hemifield.

Question 62

How do signals from each eye project to the LGN?

Answer 62

Layers 2,3,5 receive ipsilateral input; layers 1,4,6 receive contralateral input.

Question 63

Where does visual information go after the LGN?

Answer 63

To V1, then splits into ventral (‘What’) and dorsal (‘Where’) streams.

Question 64

What is the function of the ventral (‘What’) pathway?

Answer 64

Object, face, and place recognition.

Question 65

What is the pathway of the ventral stream?

Answer 65

V1 → V2 → V4 → LOC → OFA → FFA → PPA.

Question 66

What does the Lateral Occipital Complex (LOC) do?

Answer 66

Process object recognition.

Question 67

What is the function of the Fusiform Face Area (FFA)?

Answer 67

Recognize faces (identity, not emotion).

Question 68

What is the function of the Occipital Face Area (OFA)?

Answer 68

Early facial feature detection.

Question 69

What is the function of the Parahippocampal Place Area (PPA)?

Answer 69

Scene and place recognition.

Question 70

What is the function of the dorsal (‘Where’) pathway?

Answer 70

Motion, depth, and spatial location processing.

Question 71

What is the pathway of the dorsal stream?

Answer 71

V1 → V2 → V3 → MT/V5 → MST → V6 → V7 → STS.

Question 72

What is the function of the Superior Temporal Sulcus (STS)?

Answer 72

Motion and social perception, including emotion.

Question 73

What is the function of MT/V5?

Answer 73

Motion processing.

Question 74

What is the function of MST?

Answer 74

Complex motion processing and spatial awareness.

Question 75

What is Prosopagnosia (Face Blindness) and what brain area is damaged?

Answer 75

Inability to recognize faces due to FFA damage.

Question 76

What is Capgras Syndrome and what brain area is damaged?

Answer 76

Inability to associate emotion with familiar faces due to STS damage.

Question 77

Why do optical illusions occur?

Answer 77

They result from retinal and cortical processing mechanisms.

Question 78

What is color constancy, and how does the brain achieve it?

Answer 78

Perceiving consistent colors under varying light via retinal and V4 mechanisms.

Question 79

How does mathematical modeling help explain illusions?

Answer 79

It shows illusions arise from efficient neural coding, not just cognitive interpretation.