Visuospatial Disorders Flashcards
Anterior parietal lobe
- Somatosensory cortex (cytoarchitectonic areas 3, 1, 2)
* Processes information about touch, pressure, vibration, joint sense
Posterior parietal lobe
–> sense of space
• Superior and inferior parietal lobules
• Integrates somatosensory information from the postcentral gyrus and visual information from the occipital lobe
• Codes for organization of body in space
• Allows to interact with objects and tools in the environment/space
• Allows to produce movements and postures in space
• Lesions: patients lose a sense of where their body parts (e.g., a hand) are situated in space
Supramarginal gyrus (area 40)
• Lesions produce deficits in body schema and deficits in
integrating information about position of the body in space
Angular gyrus (area 39)
• Responsible for integrating visual information with body
schema
Visuospatial disorders
- Difficulty in remembering spatial information and/or using it to guide behavior and perform mental spatial operations
- Low-level sensory processing is normal (sense of touch, hearing, sight, etc. are normal)
- Cognitive processing of visual and spatial information is impaired
- Common: damage to the dorsal, occipito-parietal projections of the visual system
Disorders of Sensory Analysis and Elementary Perception
• Impairment in perception of orientation, position, distance, and depth
• Patients do not need to suffer from the sensory loss to be impaired
• Damage to the posterior brain regions
Types of disorders covered in class:
• Localization
• Depth perception
• Line orientation
Disorder of Localization
Impairment in localization:
• Difficulty in estimating location of objects in pericorporal space (space near the body, within an arm reaching distance)
Perceptual matching tasks
• Patients are asked to compare pairs of visual stimuli with each other and make same/different judgements
Disorder of Depth Perception
Testing the impairment:
• Estimate distance in the natural environment
• Judge the relative distance of real, three-dimensional objects
• Measure the acuity of stereoscopic vision (professional tests and random-element stereograms)
Depth perception requires monocular cues (color perception and shading) and binocular cues (stereopsis)
–> see like a poster
Disturbance of stereopsis
Damage in the dorsal occipito-parietal area and the ventral occipitotemporal area
Color vision abnormalities
Damage in the ventral occipito-temporal area
Disorder of Line Orientation
Human visual system:
• Easier to discriminate horizontal lines from vertical lines, rather than oblique lines (“oblique effect”)
• Judgment of Line Orientation test
• A failure on this test is strongly associated with
damage in the right posterior parietal and
occipitoparietal regions within the dorsal visual stream
Judgment of Line Orientation (JLO) test can be useful to
• Assess subject’s performance on complex tasks of visual reasoning and visual
construction
• Evaluate complex abilities such as driving-related skills
• Study aging
• Discriminate between normal elderly and
demented subjects:
• Normal elderly make the majority of errors when
they need to compare the oblique lines from the
same quadrant
• Demented patients make errors in comparing
oblique sample lines to vertical and horizontal
lines, or lines from another quadrant
Disorder of visual disorientation
- Large lesions to the posterior brain regions (including the occipital lobes)
- Misjudging the relative and absolute distances of objects from the body
- Misjudging lengths and sizes of objects
- Misjudging relative positions of objects
- Difficulty avoiding obstacles when walking
- BUT Sufficient visual acuity and stereoacuity
Disorders of Spatial Cognition
Types of disorders covered in class:
• Mental rotation
• Memory for location and spatial memory
• Maze learning
Disorder of Mental Rotation
Mental rotation is the ability to imagine “movements, transformations, or other changes in visual objects”
• Sensory perception and memory are normal
• Damage to the posterior brain region
–> In some studies, damage is in the parietal region of the right hemisphere
Memory for location and spatial memory
• Ability to remember the location of a stimulus (e.g., object) in space
• Short-term aspect is measured by:
1. Corsi block span
2. Recall location e.g. position of a circle on a line
• Long-term aspect is measured by:
1. Kim’s game (objects)
Topographical Disorders
Topographical orientation:
• “ability of individuals to find their way from one location to another in large-scale environments such as home, workplace or neighborhood”
• “ability to orient and navigate in the environment”
Topographical disorders = disorders of topographical orientation and memory
• Common in adults with acquired brain damage and dementia
Specific examples of topographical deficits
• Loss of memory for familiar surroundings
• Inability to draw, use and interpret maps (relates to geographical knowledge/skills)
–> Inability to locate countries, cities, prominent landmarks on a map
• Inability to find one’s way in the own home
• Inability to find one’s way in the external environment (i.e., inability to learn new topographical information)
Cognitive aspect of navigation requires
- Recognition of landmarks (e.g., buildings, monuments, etc.)
- Mental representation of spatial relationships between the landmarks (e.g., Montreal Museum of Fine Arts is located south-west from the Stewart Biology building)
topographical disorientation includes
• Recognition (perceptual) component -> perceptually-based inability to recognize landmarks (buildings, monuments, neighborhoods, etc.) which have distinctive orienting features
• Spatial relations component -> loss of topographical memory for spatial information (layout) of familiar surroundings, routes; inability to form new mental spatial
representations
Egocentric disorientation
inability to represent the relative location of objects with respect to self
Heading disorientation
preserved landmark recognition, but inability to derive directional information from recognized landmarks; loss of “sense of direction/heading”
Landmark agnosia
inability to recognize and use prominent features of landmarks for the purposes of orientation in the familiar and novel environments
• Ability to distinguish different classes of landmarks (e.g., living room from a bedroom, school from hospital), but inability to identify specific landmarks by their salient features (e.g., one museum from another)
Route based representation
• Relies on procedural learning -> learn a specific route from point A to point B as a sequence of instructions or movements (displacements in space)
–> E.g. go straight, turn right at third intersection, etc.
• Environment is represented as a series of steps to get from starting location/landmark A to target location/landmark B
–> ~ Linear representation
Map based representation
“Cognitive map” = mental spatial representation of the environment
- Environment is represented as a mental map which contains spatial relationships, orientations
and distances between landmarks “in our minds eye”
• Map-like ability to select flexibly any route to reach any location in the environment
• Critical for orienting within the environment
• Becomes assessed when deviating from a habitual route
Brain structures involved in relation to cognitive map:
- Hippocampus -> acquiring and forming a cognitive map
- Retrosplenial cortex bilaterally -> forming and using a cognitive map
- Frontal, parietal, temporal cortex -> navigating the environment
egocentric (or body-centered) coordinate system
- Route-based representation requires this
We need to know the position of salient landmarks with respect to our own body - involves the posterior parietal region
exocentric or allocentric coordinate system
- Map-based representation requires this
• Global invariant (fixed) spatial relationship between landmarks which does not depend on where our body is in this space - processed in the ventral, posterior temporal and occipital cortex.
Body schema
General term for the personal awareness of one’s body, including the location and orientation of its various parts and their relative motion in space and time, as well as its
functional integrity
- unconscious neural representation of body
- involved in action
Body image
Conscious representation of the body coded by its sensory characteristics of quality, form
and intensity
- involved in perception
Bodily and auditory hallucinations
- Can happen in the absence of sensory inputs
* Mainly, disruption of body image
Phantom limb
- Patients can feel it moving and, sometimes, interacting with objects (e.g., coffee mug)
- Sense of control and presence of the limbs in some people born without limbs
Alice in Wonderland syndrome
Disruption of body image (mainly)
• Change in perception of the size of a body part
-> Experience of body/limbs being longer or smaller than they really are
• No motor deficit observed (movements remain normal)
• Occurs in psychiatric and neurological conditions (epilepsy, migraine with aura, and schizophrenia, etc.)
• Hallucinations happen spontaneously and unpredictably
Anosognosia
verbal explicit denial of illness
Anosodiaphoria
lack of genuine concern about the deficit/ indifference
Symptoms of anosognosia
- Neglect or denial of paralysis
- Lack of appreciation of the extent of the defect
- Experience of a phantom limb
- Failure to distinguish between one’s own body and that of another
Why is anosognosia a problem?
- Impair a patient’s desire to seek medical help
* Impair desire to seek therapy or to benefit from therapy
Hypochondriasis
a physically healthy person is convinced of being ill
Anton’s syndrome
denial of cortical blindness
Patient’s pupils respond to light, BUT the patient cannot demonstrate functional sight:
• Cannot count fingers or discriminate objects, shapes, or colors
• Typically deny having any visual difficulty
• Guess the answer to questions
• When confronted with their errors -> make excuses (“The lights are too dim”)
• Often have visual hallucinations (simple or complex)
• Can have loss of memory and be in a confused state
Hemiplegia
paralysis of one side of the body
Autotopagnosia
inability to localize (e.g., identify, point, describe specific
location) body parts on oneself and others with preserved ability to name body parts
Pure autotopagnosia
concerns only one’s own body and not the body of others
• Egocentric coordinate system
• Suggests to involve the superior parietal lobule in the left hemisphere
Finger agnosia
•inability to differentiate the individual fingers or apply them individually as tools
- Highly automatized activities are preserved
–> For example, patients can thread a needle and sew, can paint, can point to objects, etc.
–> BUT Patients cannot use a specific finger (e.g. their thumb, index finger) on
instruction.
–> For example, patients cannot point with their index finger to an object when specifically
instructed to do so.
Right/left disorientation
inability to distinguish right from left on self, on the
examiner, or on a schematic figure
