Action Flashcards
What cortical regions are involved in motor control?
Primary motor area (M1)
Premotor cortex (PMC)
Supplementary motor area
Parietal reach areas
What are effectors?
Parts of the body that can move
What are examples of effectors in the body?
Arms, legs, head, neck, tongue
What do muscles do?
They control the effectors
How are muscles arranged?
They are arranged in pairs
Agonist and Antagonist muscles (extensor and flexor)
What are alpha motor neurons?
They control muscles
What is involved in the stretch reflex (cycle)?
- Sensory signal stretch
- Spinal cord (dorsal root)
- Alpha motor neuron
- Contract quadriceps muscle
What does the stretch reflex do?
Helps maintain the stability of limbs
What are reflexes?
The simplest form of motor control - DON’T NEED BRAIN
What does decussate mean?
When axons cross over to the other side so each hemisphere controls the opposite side of the body
What is the corticospinal tract/pyramidal tract?
1) Motor cortex
2) Midbrain
3) Medulla - axons cross over at the medullary pyramids
4) Spinal cord
What is the lowest level of the motor hierarchy?
Spinal cord
What is the highest level of the motor hierarchy?
Prefrontal and parietal cortex
What is the prefrontal and parietal cortex involved in?
Intentions to do actions (planning)
What is the primary motor area involved with?
Tells the muscles what to do
How is the primary motor area arranged?
By a somatotopic map (motor homunculus)
- organized according to body part
How is the primary motor area organized?
Has a contralateral organization (left brain controls right side of body)
What are the secondary motor areas?
Pre-motor cortex (PMC) - lateral
Supplementary motor area (SMA) - medial
What do the secondary motor areas do?
They plan voluntary actions
Where are the association motor areas?
Parietal cortex
What are the association motor areas involved in?
Planning
Which brain region is involved in simple movements (fMRI study)?
Primary motor cortex
Which brain regions are involved in complex movements (fMRI study)?
Primary and supplementary motor areas
Which brain area is involved in imagining movements (fMRI study)?
only SMA
What did applying TMS over the motor cortex in the TMS study do?
Movement was halted or the wrong key was pressed
What did applying TMS over SMA in the TMS study do?
The effect was the same but delayed
What is the difference between the Premotor Area and the Supplementary Motor Area?
PMC:
- Externally-guided movement
- Connections with parietal lobe
SMA:
- Internally-guided movement
- Connections with frontal lobe
What are the similarities between the Premotor Area and the Supplementary Motor Area?
They both are involved in motor planning
What are the 3 subcortical motor structures?
Brainstem
Cerebellum
Basal Ganglia
What does the brainstem do?
Controls face/reflexes (breathing, eating, eye movements, facial expressions, etc.)
12 cranial nerves
What does the cerebellum do?
Balance and Hand-eye coordination
Works ipsilaterally (same side)
What are the 5 parts of the Basal Ganglia involved in action?
- Caudate nucleus - make up striatum
- Putamen - make up striatum
- Globus pallidus
- Subthalamic nucleus
- Substantia nigra
What does the Basal Ganglia do?
Selecting and initiating actions
How to M1 neurons code?
M1 neurons code for direction of movement
What is a population vector?
Summed activity over all neurons
What do M1 neurons tell us?
Individual neurons have preferred directions
Cells represent planned movement before execution of movement
What is the Human Brain-Machine Interface (BMI)?
Its an array of microelectrodes implanted into motor cortex and BMI is trained by imagining different movements
What is hemiplegia?
Loss of voluntary movement on 1 side
Where is the damage that causes hemiplegia?
Primary motor cortex (contralateral M1)
What is apraxia?
Loss of skilled action (motor planning, not muscle)
Coordination problem
Where is the damage that causes apraxia?
Parietal damage (left hemisphere) or secondary motor area damage
What is ideomotor apraxia?
When they have a rough sense of the desired action but have problems executing it
What is ideational apraxia?
It is more severe; there is a disrupted knowledge of action (appropriate use of tool)
What does the neocerebellum do?
Motor planning
What does the spinocerebellum do?
Motor execution
What does the vestibulocerebellum do?
Balance and eye movements
What is cerebellar ataxia?
Can select and initialize movement
Clumsy, irregular, erratic motions
Cannot smoothly terminate action
What is Parkinson’s?
Loss of dopamine neurons in substantia nigra
There is less input from basal ganglia to motor cortex which causes a reduction in movement
What is bradykinesia?
Slowness in execution of movements
What is hypokinesia?
Reduction in voluntary movements
What is Huntington’s?
Degenerative disease of striatum
Loss of inhibition –> too much input to motor cortex –> increase in movement
What is an increase in movement called?
Hyperkinesia
What is chorea?
Clumsiness, balance problems, increase in involuntary movements
What are some treatments for Parkinson’s?
L-dopa therapy - synthetic precursor to dopamine
Deep brain stimulation therapy - stimulate regions not getting enough dopamine
What is the Case of the Frozen Addicts?
Several young people suddenly presented with sever Parkinson’s-like symptoms because they had taken a contaminated batch of synthetic heroin that destroyed dopamine cells.
What did they find as a result of the Case of the Frozen Addicts?
Treated patients with L-dopa
Huge advance in understanding Parkinson’s
