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

1
Q

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

Kolb&Wishaw H13

A
  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.

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2
Q

monocular blindness

Kolb&Wishaw H13

A

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

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3
Q

Bitemporal hemianopia

Kolb&Wishaw H13

A

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.

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4
Q

Nasal hemianopia

Kolb&Wishaw H13

A

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

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5
Q

Homonymous hemianopia

Kolb&Wishaw H13

A

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.

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6
Q

Quadrantopia

Kolb&Wishaw H13

A

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.

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7
Q

Macular sparing

Kolb&Wishaw H13

A

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

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8
Q

Scotomas

Kolb&Wishaw H13

A

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.

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9
Q

Visual agnosia

Kolb&Wishaw H13

A

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.

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10
Q

Visual object agnosia

Kolb&Wishaw H13

A

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

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11
Q

Visual object agnosia

Apperceptive agnosia

Kolb&Wishaw H13

A

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.

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12
Q

Visual object agnosia

Associative agnosia

Kolb&Wishaw H13

A

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.

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13
Q

Other visual agnosias

Kolb&Wishaw H13

A
  1. Prosopagnosia
  2. Alexia
  3. Visuospatial agnosia
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14
Q

Porspagnosia

Kolb&Wishaw H13

A

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.

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15
Q

Alexia

Kolb&Wishaw H13

A

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.

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16
Q

Visuospatial agnosia

Kolb&Wishaw H13

A

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.

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17
Q

Postcentral gyrus lesions often result in:

Kolb&Wishaw H14

A
  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.

18
Q

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

Kolb&Wishaw H14

A
  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.
19
Q

Blindsight

Kolb&Wishaw H14

A

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

20
Q

Numb touch

Kolb&Wishaw H14

A

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.

21
Q

Asomatognosia

Kolb&Wishaw H14

A

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.

22
Q

Bálint’s syndrome

Kolb&Wishaw H14

A

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.

23
Q

Contralateral neglect

Kolb&Wishaw H14

5

A

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.

24
Q

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

Kolb&Wishaw H14

A
  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.
25
Q

Recovery from neglect occurs in 2 stages:

Kolb&Wishaw H14

A
  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.

26
Q

Two main theories argue that neglect is caused by either:

Kolb&Wishaw H14

A
  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.
27
Q

Object recognition

Kolb&Wishaw H14

A

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.

28
Q

Gerstmann syndrome

Kolb&Wishaw H14

A

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.

29
Q

What are other symptoms that are characteristics of left parietal lesions?

Kolb&Wishaw H14

6

A
  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
30
Q

Apraxia

Kolb&Wishaw H14

2 types

A

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.

31
Q

Drawing

Kolb&Wishaw H14

A

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.

32
Q

Spatial attention

Kolb&Wishaw H14

A

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.

33
Q

Disorder of spatial cognition

Kolb&Wishaw H14

A

Spatial cognition= mental rotation & map reading

Injuries= PG and superior temporal sulcus

34
Q

How od left and right hemisphere injuries differ in spatial cognition impairments?

Kolb&Wishaw H14

A

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.

35
Q

What is an explanation for the overlapping symptoms between right-left?

Kolb&Wishaw H14

A

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.

36
Q

Neuro assessment

Two-point discrimintation test

Kolb&Wishaw H14

A

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.

37
Q

Neuro assessment

Sequin-Goddard form board test

Kolb&Wishaw H14

A

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.

38
Q

Neuro assessment

Line bisection test

Kolb&Wishaw H14

A

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.

39
Q

Neuro assessment

Mooney closure faces test and Gollin incomplete figure test

Kolb&Wishaw H14

A

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

40
Q

Neuro assessment

Right-left differentiation test

Kolb&Wishaw H14

A

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

41
Q

Neuro assessment

Token test

Kolb&Wishaw H14

A

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.