Lecture 18 and 19: Visuospatial Disorders Flashcards
What are the Posterior Regions of the brain?
- Posterior Parietal
- Posterior Temporal
- Occipital lobes
Where is the anterior parietal lobe?
- It is the somatosensory cortex (Brodmann areas 3,1,2)
What are the functions of the anterior parietal lobe?
- Processes information about touch, pressure, vibration, joint sense
Where is the posterior parietal lobe?
- It contains the superior and inferior parietal lobules and is composed of all the parietal lobe that is not the anterior parietal lobe.
- In purple
What are the functions of the posterior parietal lobe?
- Integrates somatosensory information and visual information
- Codes for the organization of the body in space
- Allows for interaction with objects and/or tools in the environment
- Allows to produce movements and postures in space
What happens is a patient has a lesion on the posterior parietal lobe?
- Lose sense of where their body parts are situated in space
True or False
The anterior parietal lobe contains the supramarginal gyrus (area 40) and the angular gyrus (area 39).
False, these are located in the posterior parietal lobe
What happens if a patient has damage on their supramarginal gyrus?
- Develop
- deficits in body schema
- deficits in integrating information about position of the body in space
What is a Neuropsychologival evaluation?
- Used whenever a patient shos an specific deficit/symptom
- Interview and observation of behaviour using standard tests
- Provides normative quantitative data
What are the goals of a neuropsychological evaluation?
- Goals:
- Determine which problems bother the patient the most
- Understand the context in which the issue arises
- What is the patient’s attitude towards the problem
- What is the core issue
- Exclude competing diagnoses
What is a visuospatial disorder?
- They have to do with:
- Vision
- Space
- The affect spatial relationships between an observer and an object
What are some of the symptoms displayed by patient with visuospatial disorders?
- Some of the symptoms are:
- Difficulty in remembering spatial information and/or using it
- to guide behaviour
- perform mental spatial operations
- Low-level processing is normal
- Cognitive processing of visual and spatial information is impaired
- Difficulty in remembering spatial information and/or using it
Where do we commonly find the lesions in patients with visuospatial disorders?
- Dorsal, occipito-parietal projections of the visual system
What are the visuospatial disorders that we saw in class?
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What are the characteristics of disorders of sensory analysis and elementary perception?
- Impairment in the perception of orientation, position, distance and depth
- Not necessarily an impairment at the sensory level
- Lesions:
- posterior brain regions
What are the types of disorders covered in class that have to do with sensory analysis and elementary perception?
- Localization
- Depth perception
- Line orientation
- Visual disorientation
What is the disorder of localization?
- Difficulty in estimating location of objects
- Near the body, arm reaching distance
How can we test for impairments in localization?
-
perceptual matching task
- Patients are asked to compare pairs of visual stimuli with each other and make same/different judgements
What is the disorder of depth perception?
- Difficulty estimating depth
What is necessary to perceive depth?
- Requires monocular cues (colour perception and shading) and binocular cues (stereopsis)
- Binocular depth perception depends on the disparity between views of three-dimensional objects projected to each eye.
- Two images are used in the cerebral cortex and experienced as a single three-dimensional representation under normal circumstances
Case study on disorder of depth perception
- Photographer
- Symptoms:
- Difficulty discriminating depth, shade, colour/gray scale saturation perception
- Couldn’t look at objects clearly
- Damage:
- left occipital visual cortex
- subcortical area
- corpus callosum
- Tests:
- Color blindness (good)
- Spatial motion perception (good)
- Shape perception by shade (bad)
- Colour saturation perception (bad)
- Other
-
Prosopagnosia
- could discriminate outline of the face, he could not distinguish the different parts of the face
-
Prosopagnosia
From the MRIs of the case study involving the photographer, we noticed that the damage was in the “what” visual pathway. What does this mean?
That the “what” visual pathway may have some role in depth perception
What is the shape perception test by shade?
- Use shade to distinguish shape of objects
- Find the outline
What is the colour saturation perception test?
- Select the correct colour saturation grade in the color and gray scale images
Case study #2 in disorder of depth perception:
- Diagnosis:
-
Disturbance stereopsis
- Lesion:
- dorsal occipito-parietal region
- ventral occipito-temporal region
- Lesion:
-
Colour vision abnormalities
- Lesion:
- ventral occipito-temporal region
- Lesion:
-
Disturbance stereopsis
What is the disorder of line orientation?
Impairment discriminating between line orientation.
How does a normal human visual system behave with line orientations?
It is usually easier to discriminate horizontal lines from vertical lines (rather than oblique lines)
What is the oblique effect?
The fact that it is more difficult to discriminate oblique lines than vertical and horizontal lines for humans with normal visual system.
How can we test for line orientation disorder?
- Judgement of Line Orientation (JLO)
If a patient fails the JLO test, where do you think the damage is?
- Right posterior parietal and occipito-parietal regions within the dorsal visual stream
Describe the procedure of the JLO test
- Show card A
- Ask the patient to find the line(s) in card A in the template
What else can be assessed with the JLO test?
- Assess the patient’s performance on complex tasks of visual reasoning and visual construction
- This is since it deals with lines
- Evaluate complex abilities such as driving-related skills
How can JLO test be useful to study aging?
- Differentiate between normal elderly and demented subjects
- Demented:
- More problems with oblique lines compare with vertical, horizontal and oblique lines in other quadrants
- Demented:
What is a disorder of visual disorientation?
- Symptoms:
- Misjudging
- relative and absolute distances of objects from the body
- lengths and sizes
- Difficulty avoiding obstacles
- Misjudging
- Conserved:
- visual acuity and stereoacuity (can see depth)
- Lesions:
- Large lesions to the posterior brain regions (including occipital lobes)
What are the types of disorders of spatial cognition covered in class?
- Mental rotation
- Memory for location and spatial memory
- Maze learning
What is mental rotation?
- Ability to imagine movements, transformations or other changes in visual objects
What are the characteristics of disorder of mental rotation?
- Sensory perception and memory are normal
- Lesion:
- posterior brain region
- In some studies: right parietal region
How can we test mental rotation disorders?
- 32 stimuli
- 8 for each A, B, C and D
- Half black disc on right hand, other half black disc on left
- Question:
- Which hand is black disc
NOTE: Patients with right hemisphere lesions are selectively impaired in the inverted condition.
What is memory for location and spatial memory?
Ability to remember the location of a stimulus in space.
How can we measure short-term aspect of spatial memory?
- Corsi block span
- Recall location
What is the procedure in Corsi block span test?
- The experimenter taps a sequence of cubes
- The patient is asked to reproduce the same sequence
Note: patient do not see the numbers on the cubes
If a patient has problems with the Corsi block span test, which brain areas do you think are damaged?
- Parietal lobe
- Hippocampus
What is the procedure in the Recall location test?
- Patient is given card A
- Then, card A is put away and the patient is given a blank card. They are then asked to draw the dot at the same position as in card A
Note:
- This is a hard task.
- People without disorder are not very precise
- With disorder will be very imprecise
If a patient does poorly in the recall location task, where do you think the damage is?
Parietal damage
How can we test for long-term spatial memory?
- Kim’s game
What is the procedure of Kim’s game?
- Set dollar store items in random order, position and orientation on a table
- Ask the patient what each of the objects are and what their price might be
- Move the patient to another room
- Ask which objects they remember
- Ask to replace the same objects as they were in the other table
- 24 hours after repeat 4 and 5