Week 10 Lecture 10 - motor control part 1 Flashcards
What do most actions require?
- Multiple muscles
- Precise timing (e.g. between the 2
hands) - Multiple components of movement
What do “higher” cognitive aspects of motor control include?
- Planning and timing
- Sequencing
- Imagery (cf mirror neurones)
- Expertise (e.g. sport, musical instrument)
What are some applications of understanding motor control?
- How to best learn motor skills
- Rehabilitation of patients with difficulties
with movement - Using knowledge of human movements to create artificial limbs/robots
What are the key cortical motor areas?
see summary sheet
What motor function is the primary motor cortex responsible for?
execution
What motor function is the premotor cortex responsible for?
preparation of actions
What motor function is the prefrontal cortex responsible for?
higher level of planning
What motor function is the parietal cortex responsible for?
sensory-motor links
Where is the primary motor cortex (M1) located?
In pre-central gyrus
How is the primary motor cortex organsied?
Somatotopic organisation (from soma
“body” and topos “place”)
Activation in particular parts of M1 causes
movement of what?
particular body parts on opposite side
What is hemiplega?
paralysis of one side
What is hemiparesis?
weakness of one side
Do cells in M1 have a preferred direction of movement?
yes
What is vector coding?
populations of cells code the direction of movement
What has new research suggested about the Somatotopic organisation of the primary motor cortex?
2 parallel systems in M1 forming an integrate-isolate pattern
a.) body-part specific for fine motor control of foot hand and mouth
b.) somato-cognitive action netwotk (SCAN) for integrating goals and whole body movement
Where does info inputted into motor and somatosensory areas of the brain output?
spinal cord –> control of muscles
What is the premotor cortex split into? What are these sections responsible for?
- Lateral Premotor Cortex – externally
generated actions - Supplementary Motor Area – (medial PC)
internally generated actions e.g. well learnt sequences
What brain areas are involved when coordinating movement (bimanual)?
- cerebellum
- supplementary motor area
- premotor area
Areas more active in more difficult bimanual tasks (Swinnen & Wenderoth, 2004)
What happens when people learn a sequence?
- Faster and more accurate movements
- Change from effortful to automatic
When learning sequences, what areas of the brain change over time –> Toni et al. (1998)
- Dorsolateral prefrontal ↓
- SMA ↑
- Lateral premotor cortex ↓
(becoming more internally generated) - Primary motor ↓
Also subcortical - cerebellum
and basal ganglia
Gerloff overret al., 1997 used repetitive TMS to block activity over SMA
What was found?
SMA only interfered with performing the
most complex sequence
Frith et al. 1991 conducted a study where ppts chose which action to perform e.g., which finger
What did they find?
prefrontal cortex was involved in this process
What is the prefrontal cortex involved in?
- Attention to action – when difficult or
learning - Longer term goals and intentions
- Not specific to action, e.g. generating
random numbers - choosing what action to perform
What can prefrontal lesions produce?
- Perseveration – repeat same action when no longer relevant
- Utilisation behaviour – act on irrelevant
(or inappropriate) object in environment - Disinhibition e.g. antisaccade task
- Frontal apraxia – not able to follow steps
in routine tasks (e.g. making tea)
What is the antisaccade task?
- Required to look in opposite direction to
the target - Must inhibit (pre-potent) tendency to
look at target
What is the Norman and Shallice model?
Contention scheduling – selects appropriate schema (to complete a task)
Supervisory attentional System (SAS) –
required for novel/less automatic actions
How can action error be explained?
- Perseveration – unable to change
schemas when no longer appropriate - Utilisation behaviour – schemas activated by environment without SAS suppressing them
What can damage to the parietal cortex lead to?
apraxia
What is apraxia?
inability to perform skilled purposeful movement
What is 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)
- Can perform sequence but not components
What are 2 subcortical motor areas?
- basal ganglia
- cerebellum
What can lesions in the cerebellum lead to?
- Action tremor
- Dysmetria – over and undershooting of
movements
Deficits in:
– coordinating across joints
– Motor learning
– Timing
What is Parkinson’s disease characterised by?
- Bradykinesia – slow movement
- Tremor (resting)
- Rigidity
Shuffling
Death of dopaminergic cells in substantia nigra pars compacta
What is writing like in Parkinson’s?
- Small in size
- May reduce while writing - fatigue
What disease deficits occur in Parkinson’s?
- Internal/external – more problems with
internally generated movements - Difficulties with Complex movements – bimanual,
sequences - Difficulties with Cognitive effects – attention shifting,
everyday cognitive failures
What task is used to look at tremors?
finger-to-nose test
For patients with a cerebellar tremor, what happens in the finger-to-nose test?
tremor amplitude increases as the finger nears the target
For patients with Parkinson’s disease, what happens in the finger-to-nose test?
the tremor may be present at the beginning of movement and smooth out near the nose
