w6 ventral stream

Question 1

What are the two main cortical visual streams beyond V1?

Answer 1

The ventral stream (“what” pathway) for object recognition; colour; form; and the dorsal stream (“where/how” pathway) for motion; spatial awareness; visually guided action.

Question 2

Who proposed the two-stream model and when?

Answer 2

Ungerleider & Mishkin (1982).

Question 3

What are the destinations of each stream?

Answer 3

Ventral → inferotemporal cortex; dorsal → posterior parietal cortex (area 7a).

Question 4

Which cortical areas make up the ventral stream?

Answer 4

V1 (Primary Visual Cortex) → V2 (Secondary Visual Cortex) → V4 (Visual Area 4) → IT (Inferior Temporal Cortex)

Question 5

Which cortical areas make up the dorsal stream?

Answer 5

V1 (Primary Visual Cortex) → V2 (Secondary Visual Cortex) → MT (V5) (Middle Temporal Area) → MST (Medial Superior Temporal Area) → 7a (+ V6)(Posterior Parietal Cortex)

Question 6

What happens as we ascend the visual hierarchy?

Answer 6

Receptive fields get larger; retinotopic precision decreases; neurons respond to more complex and invariant stimuli.

Question 7

How many visual areas exist in the human brain?

Answer 7

Over 30 with more than 300 interconnections.

Question 8

What is meant by a hierarchical visual system?

Answer 8

Information is processed from simple features to complex shapes and object identity.

Question 9

How do receptive field properties change up the hierarchy?

Answer 9

Size increases; specificity decreases; feature complexity increases.

Question 10

What does invariance mean?

Answer 10

Recognising an object regardless of position; scale; rotation; lighting.

Question 11

What are the main features of V1 relevant to later processing?

Answer 11

Retinotopy; orientation columns; ocular dominance columns; simple/complex/end-stopped cells; blob/interblob organisation.

Question 12

What does the blob/interblob system contribute?

Answer 12

Blobs send colour to ventral stream; interblobs send form/orientation.

Question 13

Why is V1 called the gateway to vision?

Answer 13

It transforms retinal signals into cortical feature representations.

Question 14

What are the main inputs and outputs of V2?

Answer 14

Inputs from V1; outputs to V4 and MT.

Question 15

What is V2’s general function?

Answer 15

Integrating orientation; colour; depth; first stage of perceptual completion.

Question 16

What are the three CO (cytochrome oxidase) stripe types in V2 and their functions?

Answer 16

Thick stripes: binocular disparity/depth.
Thin stripes: colour (from V1 blobs).
Interstripes: form and orientation (from interblobs).

Question 17

What are illusory contours?

Answer 17

Edges perceived without luminance differences.

Question 18

Who demonstrated V2 responses to illusory contours?

Answer 18

Peterhans & von der Heydt (1991).

Question 19

Why are illusory contours important?

Answer 19

They show top-down filling-in for coherent shape perception.

Question 20

What is the overall function of the ventral stream?

Answer 20

Identifying what an object is - integrating colour, form, texture, and category.

Question 21

Which pathway does the ventral stream follow?

Answer 21

V1 (Primary Visual Cortex) → V2 (Secondary Visual Cortex) → V4 (Visual Area 4) → IT (Inferior Temporal Cortex)

Question 22

What are the main inputs to V4?

Answer 22

From V2 thin and interstripes. (colour and form).

Question 23

What are V4’s key functions?

Answer 23

Colour; form; curvature; colour constancy.

Question 24

What is colour constancy?

Answer 24

Perceiving same colour under different lighting.

Question 25

Who showed V4 responds to perceived colour?

Answer 25

Zeki (1983).

Question 26

How is V4 organised?

Answer 26

Columnar organisation with globs (colour-sensitive) and interglobs (form-sensitive).

Question 27

What stimuli do V4 neurons respond to?

Answer 27

Curves; angles; complex contours.

Question 28

What disorders occur with V4 damage?

Answer 28

Achromatopsia: loss of colour perception (V4 lesion). Chromatopsia: preserved colour but impaired form perception (interblob damage or CO poisoning).

Question 29

What is IT’s role in vision?

Answer 29

Final stage of object recognition — integrates complex visual features into meaningful categories (e.g., faces, hands).

Question 30

How do IT neurons respond?

Answer 30

To complex feature combinations.

Question 31

Who showed IT neurons encode feature combinations?

Answer 31

Tanaka (1992; 1993).

Question 32

What kind of receptive fields do IT cells have?

Answer 32

Very large; often bilateral; no clear retinotopy.

Question 33

What is columnar organisation in IT?

Answer 33

Neurons with similar preferences grouped vertically.

Question 34

What evidence supports population coding in IT?

Answer 34

Rolls & Tovee (1995). found that many neurons together encode faces, not single “grandmother cells.”

Question 35

Why is population coding efficient?

Answer 35

Allows combinatorial representation of many objects. a few neurons can encode thousands of objects through patterns of activation.

Question 36

What disorders are linked to IT damage?

Answer 36

Visual Agnosia: inability to recognise objects. Prosopagnosia: inability to recognise familiar faces (Fusiform Gyrus, part of IT).

Question 37

Why do experts or birdwatchers activate the face area?

Answer 37

Because it’s used for fine within-category discrimination, not just literal faces.

Question 38

What is the main function of the dorsal stream?

Answer 38

Motion analysis; spatial location; visually guided action. (e.g., reaching, grasping).

Question 39

Which cortical areas are in the dorsal stream?

Answer 39

V1 (Primary Visual Cortex) → V2 (Secondary Visual Cortex) → MT (Middle Temporal Area) → MST (Medial Superior Temporal Area) → 7a (Posterior Parietal Area) (+ V6)(Medial Motion Area).

Question 40

What are MT neurons specialised for?

Answer 40

Motion detection— nearly all MT cells are motion-selective.

Question 41

How are MT neurons organised?

Answer 41

Direction columns— grouped by preferred direction of motion.

Question 42

What is a pattern cell?

Answer 42

Neuron integrating multiple motion directions.

Question 43

What are MT’s inputs?

Answer 43

V1 magnocellular; V2 thick stripes.

Question 44

What disorder results from MT damage?

Answer 44

Akinetopsia (motion blindness).(cannot perceive smooth motion).

Question 45

What does MST encode?

Answer 45

Optic flow patterns (expansion; rotation; contraction).

Question 46

What is optic flow used for?

Answer 46

Self-motion perception and navigation.

Question 47

How do MT and MST receptive fields differ?

Answer 47

MST fields are much larger and integrate over wider areas of the visual field.

Question 48

What is the function of area 7a?

Answer 48

Integrates visual and proprioceptive information for Eye–hand coordination; spatial attention.

Question 49

What are gaze-locked neurons?

Answer 49

Neurons in 7a that fire only when the eyes are looking in specific directions — crucial for spatial mapping.

Question 50

What is special about V6 neurons?

Answer 50

Real-position cells responding to world-fixed objects.

Question 51

What does V6 maintain?

Answer 51

Stable world-centred spatial perception.

Question 52

What are V3’s main functions?

Answer 52

Dynamic form; boundaries defined by motion or luminance.

Question 53

What input does V3 receive?

Answer 53

Mainly magnocellular input (motion/form).

Question 54

What is dynamic form?

Answer 54

Perception of shape based on motion cues — “the form of things that move.”

Question 55

What condition is linked to V4 damage and what are the symptoms?

Answer 55

Achromatopsia. Loss of colour perception

Question 56

What condition is linked to interblob (V1/V2) damage and what are the symptoms?

Answer 56

Chromatopsia. Loss of form but colour preserved

Question 57

What condition is linked to IT(temporal) damage and the symptoms?

Answer 57

Visual agnosia. Can’t recognise objects

Question 58

What condition is linked to fusiform gyrus (IT) damage and symptoms?

Answer 58

Prosopagnosia. can’t recognise faces

Question 59

What condition is linked to MT damage and the symptoms?

Answer 59

Akinetopsia. Motion blindness

Question 60

What conditions are linked to dorsal/parietal damage and symptoms?

Answer 60

Balint’s syndrome - Poor eye control, spatial neglect Simultanagnosia - Can’t perceive multiple objects Optic ataxia - Poor visually guided reaching

Question 61

What condition is linked to V1 lesion and symptoms?

Answer 61

Blindsight. Unconscious visual awareness

Question 62

How do the retina and LGN feed into the streams?

Answer 62

Parvocellular → ventral; magnocellular → dorsal.

Question 63

How does V2 contribute to both streams?

Answer 63

Thin/interstripes → V4; thick stripes → MT.

Question 64

How is population coding a unifying concept across the hierarchy?

Answer 64

It explains how both simple (V1 orientation) and complex (IT objects) features are encoded by distributed neural activity

Question 65

How does Marr’s theory relate?

Answer 65

Ventral stream supports 3D object models; dorsal supports viewer-centred coordinates.

Question 66

What is the role of top-down feedback?

Answer 66

Enhances attention; expectation; context-driven interpretation.