Sensorimotor Dysfunction Flashcards
Hierarchical organization of motor system
- Association cortex
- Secondary motor cortex
- Primary motor cortex
- Brainstem motor nuclei
- Spinal motor circuits
First is abstract plan, middle is refining movement, last is specific motor sequencing
Parallel timing and sequence
- Basal ganglia
- Cerebellum
Manage the timing and the sequence of movements
How does practice help movements?
Response chunking - sequence is treated as a unit
Shifts control to lower levels. The activation of upper levels isn’t needed because you don’t need to think about how to do things anymore.
Motor Equivalence
There is more than one way to carry out a movement
Writing out a sentence using a different part of body holding the pencil
2 Parts of sensory association cortex
Posterior parietal association cortex
Dorsolateral prefrontal association cortex
Posterior parietal association cortex
Integrates information about current position of body parts with information about external objects you may act upon
Input is felt by this section of brain, then it sends output to other things that either create movement or to other sensory cortices
Damage to Posterior Parietal association cortex
Contralateral neglect
Apraxia: impaired voluntary movement. inability to initiate correct movements
Apraxic errors: imitation of gestures, performance of gestures on command, use of tools and objects in unusual contexts (cannot pretend to use screwdriver as paint brush)
Dorsolateral prefrontal association cortex
involved in evaluation of external stimuli and initiation of voluntary reactions.
Planning and inhibiting inappropriate movements
First neurons to fire when anticipating motor activity
Damage to Dorsolateral prefrontal association cortex
Wide variety of effects suc as with cognition, planning, and inhibiting inappropriate movements
Mirror neurons
In ventral premotor cortex
May be related to theory of mind and empathy
Secondary motor cortices
Produce and guide movements in space
Primary motor cortex
Somatotopically organized (point to point correspondence of area on body to specific point on CNS)
Initiate voluntary movement
Lesions on primary motor cortex
Disrupt person’s ability to move one body part independently of others
potential astereognosia
May reduce speed, accuracy, and force of movements
Cerebellum damage leads to:
Loss of ability to precisely control direction, force, velocity and amplitude of movements
Loss of ability to adapt patterns of motor output to changing conditions
impairment in learning new motor sequences
difficulty maintaining steady posture
ex. Prism goggles and throwing darts. people with cerebellar damage cannot adapt their throwing. Therefore they will always throw as if not inhibited by the goggles.
Cerebellum function
receives input from primary and secondary motor cortex
compares intended movements to actual movement
Basal ganglia functions
two pathways.
At rest, it inhibits the motor/premotor areas = no movements (stop pathway)
To activate motor cortex, we must inhibit the inhibition (disinhibition) via dopamine signalling from substantia nigra (go pathway)
Parkinson’s disease
Too much STOP
Death of the substantia nigra neurons (creating less GO)
Diminished movements, mainly movement initiation
Makes it harder to start movements and then change them later on.
Parkinson’s treatment
L-dopa
Stimulates substantia nigra
Huntington’s disease
Affects neurons across the brain, particularly the striatum
Decreases inhibition (STOP), leading to excessive movement
no strong treatment options
