Lecture 5-Higher Visual Processing

Question 1

What are the critical features of the Primary Visual Cortex?

Answer 1

The critical features of the Primary Visual Cortex include three major vertically-oriented systems: orientation columns, blobs in upper layers concerned with color, and ocular dominance columns.

Question 2

What are orientation columns?

Answer 2

Orientation columns consist of neurons that respond selectively to light bars oriented in particular directions.

Question 3

What are blobs in the Primary Visual Cortex concerned with?

Answer 3

Blobs in the upper layers of the Primary Visual Cortex are concerned with processing color information.

Question 4

What are ocular dominance columns?

Answer 4

Ocular dominance columns receive inputs from one eye or the other, contributing to depth perception and visual processing.

Question 5

How are units in the Primary Visual Cortex organized?

Answer 5

Units in the Primary Visual Cortex are organized into hypercolumns, representing small areas of the visual field.

Question 6

What are the critical functions of the Primary Visual Cortex?

Answer 6

1. It represents every part of the visual field with line segments (edges) in all orientations, which is important for recognizing shapes.
2. It combines the visual input from both eyes through ocular dominance coloumns, which helps with depth perception.

Question 7

What is the role of the P pathways in the primary visual cortex?

Answer 7

P pathway essential for:
1. colour vision
2. high spatial frequency sensitivity (fine form discrimination)
3. low temporal frequency sensitivity (detecting slow changes in visual stimuli)

Question 8

What is the role of the M pathways in the primary visual cortex?

Answer 8

Lower spatial (larger features or patterns in an imag) and higher temporal frequency (faster changes or movements in visual stimuli)

Question 9

What are the two perspectives in visual processing proposed by Ungerleider and Mishkin?

Answer 9

Ungerleider and Mishkin proposed the “What” and “Where” perspectives, suggesting that object recognition relies on visual information processed in the inferior temporal cortex (IT), while spatial perception depends on information processed in the posterior parietal cortex (PP).

Question 10

What were the observations from studies on monkeys with lesions in IT and PP?

Answer 10

Monkeys with lesions in the inferior temporal cortex (IT) showed deficiencies in perceiving objects, while those with lesions in the posterior parietal cortex (PP) were deficient in perceiving spatial relations between objects.

Question 11

What theory was proposed by Livingstone and Hubel regarding the “What” and “Where” perspectives?

Answer 11

Livingstone and Hubel theorized that the “What” and “Where” visual processing streams are direct extensions of the Magnocellular (M) and Parvocellular (P) pathways, respectively.

Question 12

Which cortical regions are associated with the perception of faces and location in the ‘What’ and ‘Where’ pathways?

Answer 12

The ventral temporal cortex is associated with face recognition (‘What’), and the dorsolateral cortex is associated with location (‘Where’).

Question 13

What perspective on visual processing is proposed by Goodale and Milner? (Vision in action perspective)

Answer 13

Propose perspective emphasizing vision in action, suggesting that visual processing streams evolved to transform incoming visual information for different purposes: perception or action.

Question 14

What are examples of cortically-based visual disorders involving upstream visual deficits?

Answer 14

Examples include achromatopsia (deficts in color perception), and akinetopsia (involving deficits in motion perception)

Question 15

What are examples of cortically-based visual disorders involving downstream visual deficits in the ventral stream?

Answer 15

Examples include apperceptive agnosia (unable to recognize objects) and associative agnosia (Difficulty linking objects with their meaning)

Question 16

What is visual agnosia and what is it caused by?

Answer 16

The inability to recognize objects; results from damage to secondary visual areas, usually along ventral visual stream.

Question 17

What are two basic types of agonisa?

Answer 17

1. Apperceptive: Difficulty perceiving and discriminating objects
2. Associative: Difficulty linking perceived objects with their meaning or significance.

Question 18

What is the focus of the ventral visual processing system according to Goodale and Milner?

Answer 18

The ventral system encodes enduring object characteristics, essential for long-term object recognition and significance (What).

Question 19

What role does the dorsal visual stream play in visual processing according to Goodale and Milner?

Answer 19

The dorsal visual stream is tuned to visually guided actions, processing moment-to-moment changes to mediate the control of goal-directed actions (Where).

Question 20

What is Apperceptive Agnosia?

Answer 20

Apperceptive Agnosia is characterized by the inability to form a perceptual understanding of objects, despite intact sensory functions (You have trouble even seeing or understanding what the object is, so recognizing its purpose becomes difficult)

Question 21

What are the key features of Apperceptive Agnosia?

Answer 21

Individuals with Apperceptive Agnosia can describe basic features of objects but struggle to integrate these features for recognition, copying, or matching of simple shapes.

Question 22

What brain damage is associated with Apperceptive Agnosia?

Answer 22

Apperceptive Agnosia is associated with bilateral damage to the lateral occipital lobes.

Question 23

What is associative agnosia?

Answer 23

involves the inability to recognize objects despite intact perception. (You see the object clearly but can’t remember what it is or what it’s used for.)

Question 24

What abilities are preserved in individuals with Associative Agnosia? (2)

Answer 24

1. Individuals with Associative Agnosia can copy objects and match simple, similar-looking objects.
2. They can also define what an object is based on a label, indicating that it’s not a language or memory problem.

Question 25

What brain damage is associated with Associative Agnosia?

Answer 25

Associated with damage to the anterior portion of the ventral stream, particularly the anterior temporal cortex.

Question 26

What is Prosopagnosia?

Answer 26

Prosopagnosia is the inability to recognize faces, including previously known faces and even one’s own in a mirror.

Question 27

What is Color Agnosia? Damage to which area causes it?

Answer 27

The inability to associate colors with objects, often resulting from damage to the right Brodmann areas 18 and/or 19.

Question 28

What is Alexia? What areas is damage associated with?

Answer 28

The inability to read, where someone can see letters but can’t understand words due to damage to the left fusiform and lingual gyri, including Brodmann areas 18 and 19.

Question 29

What brain areas are typically damaged in Prosopagnosia?

Answer 29

Associated with damage to the bilateral occipital-temporal junction, lateral mid-fusiform gyrus, with the right hemisphere typically more affected than the left.

Question 30

What abilities are preserved in individuals with Prosopagnosia?

Answer 30

Individuals with Prosopagnosia can recognize facial expressions normally, distinguish between human and non-human faces, and recognize other objects.

Question 31

What did Kanwisher et al. (1997) discover in their fMRI study regarding face perception?

Answer 31

They discovered that face perception activated the right lateral mid-fusiform gyrus, indicating a specialized region of the brain for recognizing faces, known as the Fusiform Face Area (FFA).

Question 32

What is double dissociation, as demonstrated by patient CK?

Answer 32

Double dissociation is evidenced by patient CK’s ability to recognize upright faces despite a brain injury but severe impairment in recognizing inverted faces and objects, indicating separate neural systems for face and object recognition.

Question 33

How do the face and object processing systems interact according to patient CK’s case?

Answer 33

The face and object processing systems appear to compete, where damage to the object system reduces interference with the face system, potentially enhancing face recognition.