M7, T2, apraxia Flashcards
What is Apraxia?
- Higher order disorder of skilled movement not due to sensory or motor deficits, weakness, abnormal tone or posture, movement disorders, poor comprehension or uncooperativeness
- Loss of the ability to perform well learned purposeful movements
- Patients still have the desire and the physical ability to perform the movements
- Can occur for transitive (with objects/tools) and intransitive (without objects/tools) gestures
- Due to stroke, Alzheimer’s Disease or Corticobasal degeneration
Voluntary-automatic dissociation
Apraxia patients may spontaneously perform gestures that they cannot perform on command
Context dependence
patients are successful/unsuccessful at executing a movement based on whether they are in a natural or clinical setting
Subtypes of Apraxia: Ideational Apraxia
- Disturbance in the conceptual organization of actions
- May demonstrate an inappropriate use of objects and may fail in gesture discrimination and matching tasks.
Example:
- patient eats with a toothbrush and brush his teeth with a spoon
- patient could name tools he was shown, but couldn’t match the tools with the objects you would use them with
Subtypes of Apraxia: Ideomotor Apraxia
- Disorder of sensorimotor action programs that help generate and control motor activity
- Impacts timing, sequencing and spatial organization of gestural movements
- Conceptual knowledge of actions intact, objects should be used for their correct function and in correct serial order
Assessing ideational versus ideomotor apraxia
Gesture tasks:
- With or without tools
- Meaningless gestures
- Meaningful gestures
- Complex movements with multiple objects
- Gestures relative to body position
- Gestures tested different modalities
These different tests revealed different subtypes of Apraxia
Roy and Square (1985) model of Apraxia
- Two components (conceptual system and production system)
-> Conceptual system = abstract representation of the action
-> Production system = incorporates sensorimotor representation of the action and mechanisms for movement control
*look up image
ideational = dysfunction of conceptual system
ideomotor = dysfunction of production system
Patient GW, ideomotor apraxia
- 61 year old RH woman with ideomotor apraxia
- Damage to parietal lobes
- Critically, she could comprehend and discriminate gestures with objects that she herself could not perform
- This dissociation suggests two separate systems
Limitation of Roy and Square 1985 model
the model is somewhat limited in that it cannot predict a number of modality-specific dissociations
Cubelli et al (2000) model of Apraxia
- Semantic and non-semantic route for meaningful and meaningless gesture can be modelled
- Specific modules allow for a more nuanced understanding of apraxia
*look up image
Cubelli model, part A
Action input analysis
problems understanding seen gestures, but intact ability to perform gestures on verbal command + able to imitate gestures via VMC
Cubelli model, part B
Action semantic system
problems understanding gestures with inability to perform gestures based on semantic route, but able to imitate gestures via VMC
Cubelli model, part C
Action output lexicon
problem executing actions when directed to do so, but would still be able to understand actions and imitate gestures via VMC.
Cubelli model, part D
Visuo-motor conversion mechanism
Would not be able to imitate meaningless gestures via the non semantic VMC, but would be able to perform actions on command/understand them
Cubelli model, part E
Gestural buffer
Impairment in all execution tasks either on command or on imitation. Would still understand various actions via the action semantic system etc
