1.3 To link lesions of the parietal and occipital lobes to motion and perception disorder

Question 1

Two key elements in the way the brain organises the visual fields

Kolb&Wishaw H13

Answer 1

1. The left half of each retina sends projections to the right sight of the brain, right half sends its projections to the left side of the brain. The representation of each side of the visual world seen by each eye is sent to the same place in area V1, and damage to V1 affects vision in both eyes.
2. Different parts of the visual field are represented in different parts of area V1. Thus, injury to a specific region of V1 produces a loss of vision in a specific part of the visual world.

PLAATJE met verschillende soorten blindness.

Question 2

monocular blindness

Kolb&Wishaw H13

Answer 2

Due to destruction of the retina or optic nerve of one eye –> which is the loss of sight in that eye.

Question 3

Bitemporal hemianopia

Kolb&Wishaw H13

Answer 3

Lesion of the medial region of the optic chiasm severs the crossing fibers –> the loss of vision of both temporal fields.

Buitekanten van visueel veld, dus rechts-rechts en links-links

This dificit can occur when a tumour develops in the pituitary gland. As the tumour grows, it can put pressure on the medial part of the chiasm and produce the loss or disurbance of lateral vision.

Question 4

Nasal hemianopia

Kolb&Wishaw H13

Answer 4

A lesion of the lateral chiasm –> results in a loss of vision of one nasal field

Question 5

Homonymous hemianopia

Kolb&Wishaw H13

Answer 5

Complete cuts of the optic tract, lateral geniculate body or area V1 –> which is the blindness of one entire visual field.

Dus bv 2 keer aan linkerkant waardoor je heel visueel veld mist

In field 5 the disturbance affects info coming from both eyes, because of this we know that the visual field defect is present in both eyes.

Question 6

Quadrantopia

Kolb&Wishaw H13

Answer 6

Lesions in the eye or optic tract –> produce visual disturbance in one eye.

Lesions to the optic nerve or brain affect both eyes. If lesion is partial only a part (quadrant) of the visual field is destroyed.

Question 7

Macular sparing

Kolb&Wishaw H13

Answer 7

Helps to differentiate lesions of the optic tract or thalamus from cortical lesions because macular sparing occurs only after unilateral lesions to the visual cortex.

Macular sparing does not always occur, however, many people with visual-cortex lesions have a complete loss of cision in one-quarter or one-half of the fovea.

macular= gele vlek

Question 8

Scotomas

Kolb&Wishaw H13

Answer 8

Are small blind spots in the visual field, produced by small occipital lobe lesions.

People are often totally unaware of scotomas because of constant tiny involuntary eye movements and “spontaneous filling in” by the visual system.

Question 9

Visual agnosia

Kolb&Wishaw H13

Answer 9

Difficult to describe due to the variety of pat’s and the lack of agreement on the taxonomy.
We seperate visual agnosias into object agnosias and other agnosias.

Question 10

Visual object agnosia

Kolb&Wishaw H13

Answer 10

Distinguishes 2 broad forms:
1. Apperceptive agnosia
2. Associative agnosia

Question 11

Visual object agnosia

Apperceptive agnosia

Kolb&Wishaw H13

Answer 11

Failure of object recognition in which basic visual functions (colour and motion) are perserved.

Fundamental deficit: inability to develop a percept of the structure of an object or objects.

Simultagnosia: pat’s can perceive the basic shape of an object, but they can’t perceive more than one object at a time. So, if 2 objects are presented together, only one is perceived.

Apperceptive agnosia doesn’t result from a restricted lesion but usually follows gross bilateral damage to the lateral parts of the occipital lobes. including regions sending outputs to the ventral stream.

Question 12

Visual object agnosia

Associative agnosia

Kolb&Wishaw H13

Answer 12

Inability to recognize an object despite its apparent perception. Thus, the associative agnosic can copy a drawing rather accurately, indicating a coherent perception, but cannot identify it.

Associative agnosia is more likely with damage to regions in the ventral stream that are farther up the processing hierarchy, such as the anterior temporal lobe.

Question 13

Other visual agnosias

Kolb&Wishaw H13

Answer 13

1. Prosopagnosia
2. Alexia
3. Visuospatial agnosia

Question 14

Porspagnosia

Kolb&Wishaw H13

Answer 14

Pat’s cannot recognize any previously known faces, including their own as seen in a mirror or photograph. They can however recognize people by face information, birthmark, moustache, characteristic hairdo.

(They may not accept that they don’t recognize themselves in the mirror, probably because they know who must be in the mirror and thus they see themselves.)

Most facial agnostics can tell humans from nonhuman faces and can recognize facial expression.

Due to bilateral damage centred in the region below the calcarine fissure at the temporal junction.
These findings indicate that facial recognition is probably a bilateral process, but assymetrical.

Question 15

Alexia

Kolb&Wishaw H13

Answer 15

Inability to read. Often a symptom complementary to facial-recognition deficits.

Most likely to result from damage to the left fusiform and lingual areas.

It can be conceived as a form of object agnosia, in which there is a perceptual inability to construct wholes from parts, or as a form of associative agnosia in which word memory is either damaged or inaccessible.

Question 16

Visuospatial agnosia

Kolb&Wishaw H13

Answer 16

Topographic disorientation, in this condition the pat had the inability to find one’s way around familiar environments uch as one’s neighbourhood.

The critical area for this disorder lies in the right medial occipitotemporal region, including the fusiform and lingual gyri.

Question 17

Postcentral gyrus lesions often result in:

Kolb&Wishaw H14

Answer 17

1. Elevated sensory threshold,
2. comprised position sense,
3. impairments in stereognosis (tactile(tastbaar) perception)

Additionally, it may lead to: afferent paresis, characterized by the loss of kinesthetic feedback stemming from postcentral gyrus lesions.

As a consequence, finger movement may become clumsy due to the individual’s inability to accurately perceive their positions.

Question 18

Even if individuals have typical somatosensory thresholds, they may still experience other types of somatosensory abnormalities or disorders, like:

Kolb&Wishaw H14

Answer 18

1. Astereognosis: the inability to recognize objects by touch.
2. Simultaneous extinction: failure to report one stimulus when pressing two tactile stimuli simultaneously to the same or different bodyparts. Is linked with lesions in the secondary somatosensory cortex (PE and PF), particularly in the right parietal lobe.

Question 19

Blindsight

Kolb&Wishaw H14

Answer 19

Ability of visually impaired individuals to identify the location of a visual stimulus without consciously seeing it.

Question 20

Numb touch

Kolb&Wishaw H14

Answer 20

Occurs when there is injury to areas PE, PF and partially PG, resulting in complete numbness on the right side of the body.

Despite being unable to feel touches, the individual can accurately indicate with the left hand which spots on the right hand were touched.

Clear resemblance to blindsight.

Question 21

Asomatognosia

Kolb&Wishaw H14

Answer 21

Involves a loss of awareness or understanding of one’s own body and bodily condition. Various forms:
1. Anosognosia: unawareness or denial of illness
2. Anosodiaphoria: indifference of illness
3. Autopagnosia: inability to localize and name body parts
4. Asymbolia for pain: absence of typical reactions to pain

Can affect both sides of body, although left side is typically more affected, due to lesions in right hemisphere.

Question 22

Bálint’s syndrome

Kolb&Wishaw H14

Answer 22

Arises from bilateral parietal lesions and is characterized by intact visual recognition but three peculiar symptoms:
1. Inability to fixate on specific visual stimuli
2. Simultanagnosia restricting attention to one object at a time
3. Optic ataxia affecting reaching under visual guidance. It stems from lesions in the superior parietal region (PE), with no. occurence alongside lesions in the inferior parietal region.

Question 23

Contralateral neglect

Kolb&Wishaw H14

5

Answer 23

Stemming from right parietal lesions. It had various symptoms:
- inability to attend to left arm
- Distorted placement of numbers when drawing a clock (all on right side)
- Selective reading, where only parts of words on the left side are recognized as in “apple pie” being read as “pie” and “football” as “ball”.
- Dressing apraxia, leading to the neglect of the left side of clothing.
- Shaving only the right side of the face, coupled with a lack of awareness of bodily issues (anosognosia), collectively defining contralateral neglect.

Question 24

What are additional difficulties pat’s experience with contralateral neglect?

Kolb&Wishaw H14

Answer 24

1. Combining blocks to form designs (constructional apraxia)
2. Engaging in free drawing with both hands, copying, and cutting out figures, often omitting the left side.
3. Drawing maps of familiar areas from memory, indicating a topographic disability.

Question 25

Recovery from neglect occurs in 2 stages: | Kolb&Wishaw H14

Answer 25

1. **Allesthesia**: individual begins to respond to stimuli on the neglected side as if they were on the non-affected side. *VB: they may react and orient to visual, tactile, or auditory stimuli on the left side of the body as if they were on the right side* 2. **Simultaneous extinction**: person starts responding to stimuli on the previously neglected side, unless both sides are stimulated simultaneously. In such cases, the only notice the stimulation on the side of the lesion. Contralateral neglect requires damage to both the right intraparietal sulcus (which divides PE and PF) and the right angular gyrus.

Question 26

Two main theories argue that neglect is caused by either: | Kolb&Wishaw H14

Answer 26

1. **Defective sensation or perception**: injury to the parietal lobe, which receives input from all sensory areas, can disrupt the integration of sensation into perception. Even though stimuli are perceived, their location is unclear to the nervous system so they are ignored. Neglect is thought to be **unilateral** because in the absence of right gemisphere function, the left hemisphere id thought to be capable of rudimentary spatial synthesis that prevents neglect of the right side. This cannoit compensate for the behavioural disturbances that come from right parietal injury. 2. **Defective attention or orientation**: refers to the inability to process input that has indeed been registered. Neglect manifests as a lack of orientation to stimuli, the lack comes from the disruption of a system with the task of arousing the person when there are new sensory stimuli.

Question 27

Object recognition | Kolb&Wishaw H14

Answer 27

Recognize objects shown in familiar views, but are badly impaired at recognizing objects that are shown in unfamiliar views. It is a defect in perceptual classification. The overall image of an object must be spatially rotated to match the new image.

Question 28

Gerstmann syndrome | Kolb&Wishaw H14

Answer 28

Occurs mainly due to lesion in the left parietal lobe, corresponding to the angular gyrus (PG) and it consists of 4 symptoms: 1. **Finger agnosia** in which the fingers cannot be named or recognized. 2. Right-to-left confusion 3. **Agraphia**: inability to write 4. **Acalculia** in which mathematical operations cannot be performed becuase of their spatial nature.

Question 29

What are other symptoms that are characteristics of left parietal lesions? | Kolb&Wishaw H14 ## Footnote 6

Answer 29

1. Disturbed language function: difficulties with writing, reading, speaking and grammar 2. Apraxia 3. Dyscalculia 4. Problems with recall 5. Right-left discrimination 6. Right hemianopia

Question 30

Apraxia | Kolb&Wishaw H14 ## Footnote 2 types

Answer 30

Is a movement disorder characterised bu the inability to perform skilled movements despite intact strength, muscle function and comprehension. 2 noteworthy types: 1. **Ideomotor apraxia**: pat's struggle to imitate movements or perform gestures, such as waving hello. 2. **Constructional apraxia**: this disrupts spatial organization, making tasks like assembling puzzles drawing, or copying facial movements challanging. Both stem from disruptions in the parietofrontal connections responsible for movement control. Parietal lobe plays crucial role in integrating sensory and spatial info for precise movements and guiding actions near the body. Dysfunction in this guidance system underlies the manifestation of ideomotor and constructional apraxia.

Question 31

Drawing | Kolb&Wishaw H14

Answer 31

Can come from injury to both left and right hemisphere, but more often comes from injury to the **right hemisphere**, mainly **right parietal** injury. The right hemisphere may play a more dominant role in spatial abilities. Disturbances in drawing seem to differ depending on whether the lesion is in the right or left.

Question 32

Spatial attention | Kolb&Wishaw H14

Answer 32

**Selective attention**: we attend only to particular stimuli. One function of parietal cortex is to allow attention to shift from one stimulus to another = **disengagement**. An aspect of disengagement is that we must reset our visuomotor guidance system to form the appropriate movements for the next target. We can extend this ide to mental manipulation of objects and spatial info too: we must reset the system for the next operation.

Question 33

Disorder of spatial cognition | Kolb&Wishaw H14

Answer 33

Spatial cognition= **mental rotation & map reading** Injuries= **PG and superior temporal sulcus**

Question 34

How od left and right hemisphere injuries differ in spatial cognition impairments? | Kolb&Wishaw H14

Answer 34

Mental rotatios involve two distinct mental processes: forming an imaged stimulus and manipulating the mental image. The **left** is responsible for generating the mental image, while the **right** performs operations on this image. Lesions in the right are more strongly associated with deficits in topographical info processing compared to lesions in the left.

Question 35

What is an explanation for the overlapping symptoms between right-left? | Kolb&Wishaw H14

Answer 35

**Cognitive preference**: many problems can be solved by a verbal, spatial or non-verbal cognitive mode. Genetic, maturation and environmental factors lead people to use different cognitive modes.

Question 36

# Neuro assessment Two-point discrimintation test | Kolb&Wishaw H14

Answer 36

Involves a blindfolded subject determining whether they felt one or two points toch their skin, gradually reducing the distance between points until they can no longer perceive two.

Question 37

# Neuro assessment Sequin-Goddard form board test | Kolb&Wishaw H14

Answer 37

A blindfolded subject manipulates blocks of different shapes and tries to place them in similarly shaped holes on a form board, then redraws the borad from memory.

Question 38

# Neuro assessment Line bisection test | Kolb&Wishaw H14

Answer 38

Is sensitive to contralateral neglect. The subject marks the middle of each of 20 lines of varying lengths and positions, with neglect typically seen on the left side of the page.

Question 39

# Neuro assessment Mooney closure faces test and Gollin incomplete figure test | Kolb&Wishaw H14

Answer 39

Assess visual perceptial capacity by presenting incomplete representations of faces or objects for the subject to identify.

Question 40

# Neuro assessment Right-left differentiation test | Kolb&Wishaw H14

Answer 40

Requires identifyin the left or right body part from drawings presented in different orientations, sensitive to left parietal lobe damage.

Question 41

# Neuro assessment Token test | Kolb&Wishaw H14

Answer 41

Assesses language comprehesion by progressively difficult tasks involving tokens of different shapes and colours. There are no standardised tests analogous to the Token test for apraxia assessment.