10 - motor control 1 Flashcards
how do we control our movements?
most actions require
- multiple muscles
- precise timing - between the two hands
- multiple components of movement
what are the higher cognitive aspects of motor control
Include: • Planning and timing • Sequencing • Imagery (cf mirror neurones) • Expertise (e.g. sport, musical instrument)
applications of understanding motor control
Include: • Planning and timing • Sequencing • Imagery (cf mirror neurones) • Expertise (e.g. sport, musical instrument)
key cortical motor areas
prefrontal cortex premotor cortex supplementary motor cortex primary motor cortex central sulcus primary somatosensory cortex posterior parietal cortex
what does the primary motor cortex control
execution
what does the premotor cortex control
preperation of actions
what does the prefrontal cortex control
higher level of planning
what does the parietal cortex control
sensory-motor links
primary motor cortex - organisation
• Pre-central gyrus
• Somatotopic organisation (from soma “body” and topos “place”)
• Activation in particular parts of M1 causes movement of particular body parts on opposite
side
tms - moving sccross motor cortex effects movement
what happens in brain lesions
Stroke affecting one side of the brain can affect movement of the opposite side of the body
what is Hemiplegia
paralysis of one side
what is Hemiparesis
weakness of one side
how does M1 code movements
- Cells in M1 have a preferred direction of movement
* Populations of cells code the direction of movement - vector coding
what happens in M1
somatotopic activation
how is the primary somatosensory cortex mapped
somatotopic mapping
what is M1
primary motor cortex
what are the connections in M1
input from supplementary motor area, premotor area and primary somatosensory area
output to spinal cord - control of muscles
frontal eye fields
Eye movements are controlled by a different cortical area
what do bodily movements rely more on
proprioreception - need to know where your body is in space
what are the two main types of eye movement
- Saccades
2. Smooth pursuit
what are saccades
- Fastest movement we make, up to 1000 deg/sec Right
- Duration 20-200 ms
- Perception is suppressed during the movement - otherwise wed see a lot of blurring
very fast eye movements make all the time
degrees of visual angle
as explore visual scene drawn to different parts on the screen
what is smooth pursuit
• Smooth tracking movement
• Up to approx 50 deg/sec
• Not usually observed in the absence of a stimulus
- cant move eyes smoothly unless theres something to follow
Slower than saccadic eye movements E.g. following a finger
what happens in the lateral premotor cortex
- Lateral Premotor Cortex – externally generated actions
E.g. metronome going - tap finger in time with it
Something is telling you timing of what you ought to be doing
what happens in the supplementary motor area
• Supplementary Motor Area – (medial PC) internally generated actions e.g. well learnt
sequences
Voluntary initiations - you decide when going to go - dont wait for green man just go when ready to go
what is the premotor cortex important for
importan for coordinating actions between different limbs or muscles
which are the areas more active in more difficult bimanual tasks
cerebellum - sub-cortical area
SMA - supplemementary motor area
pre-motor area
good at cooridnating between the hands
People who are drummers often learn to dissociate between the hands to do more complex rhythms
what happens in sequence learning
faster and more accurate movements change from effortful to automatic practiced over and mover - less errors learned to produce sequence e.g. piano, touch type, driving
what happens in sequence learning
changes over time
what brain areas decrease activation with changes over time
dorsolateral prefrontal
lateral premotor cortex
primary motor
what brain areas increase activation with changes over time
supplementary motor area
TMS in SMA
Repetitive TMS to block activity
• SMA only interfered with performing the most complex sequence
is prefrontal higher level
Choosing what action to perform (e.g. which finger, Frith et al. 1991)
• Attention to action – when difficult or learning
• Longer term goals and intentions - deciding what and what not to do
• Not specific to action, e.g. generating random numbers
what can prefrontal lesions produce
perseveration
utilisation behaviour
disinhibition
frontal apraxia
what is perseveration
Perseveration – repeat same action when no longer relevant
utilisation behaviour
Utilisation behaviour – act on irrelevant (or inappropriate) object in environment
Patient with prefrontal damage - picks up glasses and puts them on - neurologists glasses - glasses invite you to put them on
E.g. take someone elses drink - socially unacceptable
Doing actions when shouldn’t be done
disinhibition
e.g. antisaccade task
frontal apraxia
Frontal apraxia – not able to follow steps in routine tasks (e.g. making tea)
what is antisaccades
Required to look in opposite direction to the target
• Must inhibit (pre-potent) tendency to look at target
Look in opposite direction - dont look at target - move in opposite direction
In patient with prefrontal lesions - more errors - look in direction of target when should be looking in other direction
normal and shallice model - what is contention schedulling
selects appropriate schema
automatic
dont pay any attention
what is supervisory attentional system
normal and shallice model
required for novel/less automatic decisions
need when learning a new system
tired- more likely to make errors when SAS doesnt kick in
what is perseveration as an action error
unable to change schemas when no longer appropriate
what is utilisation behaviour as an action error
schemas activated by environment without SAS suppressing them
what can damage to the parietal cortex lead to
apraxia
inability to perform skilled purposeful movement
posterior parietal cortex
Representing where things are mapped out in world - important
Performing and understanding movements
ideomotor apraxia
Idea and execution disconnected – retain knowledge of action
• Can recognise action performed by another
• Fail in pantomiming action (e.g. body part as tool) - e.g. hand as toothbrush rather than person doing brushing
• Can perform sequence but not components
what are the subcortical motor areas
basal ganglia
cerebellum
cerebellar patients can lead to
• Action tremor - tremor of body during action - contrasts with parkinsons disease
• Dysmetria – over and undershooting of movements - movements are too big or small for whats needed
• Deficits in:
– coordinating across joints
– Motor learning
– Timing
overshoort in random saccade task
finger to nose test
how many people have parkinsons disease
1 in 1000, 1 in 100 over 65
issues in the basal ganglia
what are the 3 cardinal motor systems
bradykinesia - slow movement
tremour - resting
rigidity - stiffness when moving joint
shuffling
what causes parkinsons
death of dopaminergic cells in the substantia nigra pars compactica
writing in parkinsons
Small in size
• May reduce while writing - fatigue
micrographia - smaller in size
