How can motor control be described?
Functional hierarchy with 3 levels
What is high level motor control?
Strategy
What is strategy?
The goal and movement best to achieve goal
What controls high level motor control?
Association neocortex, basal ganglia
What is middle level motor control?
Tactics
What are tactics?
Sequence of events to achieve a goal smoothly and accurately
What is involved in middle level motor function?
Motor cortex, cerebellum
What is low level motor control?
Excecution
What is execution?
Activation of neurones to generate movement
What is involved in low level motor control?
Brainstem
Spinal cord
How is the brain connected to the spinal cord?
Lateral and ventromedial pathways
What are the lateral pathways connecting the brain to the spinal cord?
Corticospinal and rubrospinal tracts
What is controlled in the lateral pathways?
Voluntary movements of distal muscles
Where does the corticospinal tract originate?
Areas 4 and 6 in frontal motor cortex and somatosensory
What is the pathway of the corticospinal tract?
At spinal cord junction, tract crosses over
Axons synapse with motor neurones to control muscles
Where does the rubrospinal tract originate?
Midbrain
What do lesions of the corticospinal and rubrospinal tracts cause?
Loss of fine movements of hands and arms
Cannot move any part of upper limbs independently
What do the ventromedial pathways control?
2 control posture and locomotion
2 control trunk and antigravity muscles
What are the 2 pathways that control posture and locomotion?
Vestibulospinal and tectospinal tracts
What does the vestibulospinal tract do?
Stabilises head and neck
What does the tectospinal tract do>
Ensures eyes remain stable as body moves
What are the 2 pathways that control trunk and antigravity muscles?
Pontine and medullary recticulospinal tracts
Where do the pontine and medullary reticulospinal tracts originate?
Brainstem
How do the pontine and medullary reticulospinal tracts work?
Use sensory information about balance, body position and vision
What do voluntary movements require?
Inputs from motor cortex via lateral pathways
How are skilled movements carried out?
Upper motor neurones from the cerebra cortex travel down lower motor neurones in the lateral spinal cord to control distal limb muscles
How is posture and balance maintained?
Upper motor neurones from brainstem travel down lower motor neurones in the anterior medial spinal cord to control axial and proximal limb muscles
What is area 4?
Primary motor cortex in pre central gyrus
Where do premotor areas lie?
Anterior to central gyrus
What is area 6?
Premotor area, connecting reticulospinal neurones and supplementary motor area
What is the function of area 6?
Drive complex motor movements by connecting the innervation of proximal and distal motor units
Where are decisions about actions and movements made?
Prefrontal and parietal cortexes
Where does information about the position of the body and the action to be taken converge?
Area 6
When do neurones in the cortical premotor area fire APs?
Before a movement, then increasing and continuing throughout the action
When do neurones in area 6 fire APs?
When movement is made or imagined, or view someone else making a movement
How is a population vector produced?
Responses of all neurones, which have different preferred directions, are combined
What in the brain initiates feedwaryd adjustments?
Brainstem reticular foramen nuclei
What are feedforward adjustments used for?
Stabilise posture
What initiates feedback messages to the brain and what do they cause?
Change in body position
Stabilise posture
Where do feedback messages travel from and to?
From brainstem vestibular nuclei to spinal cord motor neurones
What does cortical damage cause?
Immediate flaccidity of contralateral muscles
What does deprivation of cortical inputs to the spinal circuits cause?
Spinal shock and hypotonia
How is function regained after damage to descending pathways?
Spared connections strength and new connections form
What is the function of the basal ganglia?
Select and initiate voluntary movements