Lecture 20: Balint-Holmes Syndrome Flashcards
What is the other names given to Balint-Holmes syndrome?
Balint’s syndrome
What are the 3 symptoms of Balint-Holmes syndrome?
- Spatial restriction of attention/ simultagnosia
- Psychic paralysis of gaze/ oculomotor apraxia
- Optic ataxia
What does spatial restriction of attention/ simultagnosia mean?
Inability to combine visual details into a coherent whole.
What does Psychic paralysis of gaze / ocular apraxia/ oculomotor apraxia mean?
Inability to shift gaze voluntarily to objects.
Patients can move their eyes up, down, left, right on command but can’t look at an object.
What does optic ataxia mean?
Difficulty reaching under visual guidance.
Vision is good, they just can’t reach while looking at the object.
Where is the damage located in Balint-Holmes Syndrome patients?
Bilateral and nearly symmetric lesions in the posterior parietal lobe, upper temporal lobe an occipita lobe
What are the causes of the damage in Balint-Holmes syndrome?
- cerebrovascular disease
- tumour
- trauma
- prion disorders
- neurodegenerative conditions
What are the associated symptoms and deficits to Balint-Holmes syndrome?
- Left hemineglect syndrome
- Apperceptive agnosia
-
Visual disorientation
- fail to perceive distances between objects or between them and other objects.
Say examples of tasks that a patient with Balint-Holmes syndrome wouldn’t be able to do.
- Defect in reading and writing
- Falt to recognize position and distances between objects
- Unable to grasp or point accurately to objects
What is the cookie theft picture test?
- Stimuli:
- image
- Task:
- report all items in the picture
- Measurement:
- compare patient’s report to list of items
What can you test with the Cookie Theft picture?
Simultagnosia/ Spatial disorder of attention
What is optic ataxia?
It is the inability to reach and grasp an object based on visual guidance
- deficit in peripheral visual field
- lack coordination between visual and motor output
- Two effects:
- Hand effect
- Field effect
What is the letter test?
Recognition of double stimuli
What does the Letter Test allows you to find?
Simultagnosia and oculomotor apraxia
What is the hand effect?
It’s misreaching with one hand into any visual field
What is the field effect?
Difficulty reaching in the contralesional field with any hand
True or False
Optic Ataxia only happens with Baltin-Syndrome
False, it can happen on its own
What is isolated Optic ataxia?
- It’s optic ataxia but without any other deficit present
- rare
- intact visual fields and stereoscopic vision
- normal oculomotor control
- normal proprioception
- normal motor abilities except for misreaching
-
Lesion:
- discrete unilateral lesions
With what other deficits may optic ataxia appear?
- Balint-Holmes triad
- Deficit in proximal hand movements
Where is the lesion for optic ataxia? How about isolated optic ataxia?
- Optic ataxia
- Large bilateral posterior lesions involving multiple functional areas
- Superior parietal lobule
- Parieto-occipital region
- Areas around intraparietal sulcus (IPS)
- Large bilateral posterior lesions involving multiple functional areas
- Isolated optic ataxia
- discrete unilateral lesions
What is dysmetria?
It is the deficit in reaching under visual guidance.
No deficit when guidance is not visual
What are the two hypothesis that expain optic ataxia?
- disruption of an online correction mechanistm
- Failure to convert the location of the visual stimulus coded in eye coordinates into the appropriate action in motor coordinates
Note, there are not the only hypothesis there is
What test can we use to test the first hypothesis?
Jumping Targets
Explain the test called Jumping Targets
- Ask a patient to reach for an object
- When the patient is about to reach the object, move the object
- Patient has to change location of hand to the new location target
*
What is deficitent coordinate transformation?
It is when you have a problem going from eye coordinates when you see a visual stimulus to motor coordinates to reach for it.
True or False
Brain lesions which produce optic ataxia are quite extensive.
True
How do we figure out which brain area is critically involved in optic ataxia?
- Multiple sources of information
- ex) animal research
Give an example of an animal research that was done regarding optic ataxia.
- Process:
- Subdivided the posterior parietal cortex into functional areas in monkey:
- LIP
- AIP
- PRR
- Results:
*
What are the names of the subdivisions of the posterior parietal cortex?
- LIP: Lateral Intraparietal
- AIP: Anterior Intraparietal
- PRR: Parietal Reach Region
Where is the Lateral Intraparietal region?
Pink area
Where is the Anterior Intraparietal area?
The highlighted yellow region
Where is the Parietal Reach Region?
Yellow contour
What is the function of the LIP?
- motor plan for eye movement
- Saccadic eye movements
- Attention processing
What is the funciton of the AIP?
- Grasping movement
What is the function of the LIP and AIP together?
- Connect with inferotemporal areas
What is the function of the parietal reach region?
- Includes areas MIP, V6A
- Reach-related activity
- Plan of reaching movements
True or False
All of the three regions/areas explored in the animal research act independently and are not connected between each other.
False, there is extensive connections between the reach (PRR), saccade (LIP) and grasp (AIP) regions
Why would the PRR, LIP and AIP regions be connected or not?
- Coordination of complex behaviours such as reach-to-grasp and eye-hand coordination through inter-areal pathways
True or False
Once the information arrives to the PRR, AIP and LIP, the information is already in motor coordinate system.
False,
AIP, LIP and PRR seem to encode targets and actions mostly in eyes coordinates
Why may we think that this region (PRR, LIP, AIP) may be linked to optic ataxia?
Because optic ataxia seems to be represented largely in eye-coordinates as well.
Describe the fMRI studies of Reaches and Saccades
- Participants were asked to fixate the red dot and to point to the moving green dot on a screen
True or False
The fMRI studies for optic ataxia were only administered to animals.
False
Only to humans.
It studied the same areas that were previously studied in monkeys.
What where the results from the fMRI studies on humans on optic ataxia?
What are the reach areas in the human brain?
- Medial complex
- Lateral complex
What is the medial complex?
- Caudal intraparietal sulcus
- Reaching activity
- Parieto-occipital junction
- Superior Medial Parietal Occipital cortex
- Precuneus
What is the lateral complex?
- Medial bank of the intraparietal sulcus
- Middle part of the intraparietal sulcus
