Lecture 10 - Motor Control + Disorders of Action Flashcards
How do we control our movements?
Most actions require multiple muscles, precise timing, multiple components of movement
What are the higher cognitive aspects of motor control?
Planning/timing, sequencing, imagery (mirror neurons), expertise
What are the key brain areas + their functions in motor movement?
Primary motor cortex - execution
Premotor cortex - preparation of actions
Prefrontal cortex - higher level of planning
Parietal cortex - sensory-motor skills
What does the primary motor cortex (M1) do?
In pre-central gyrus, somatotopic organisation (soma=body, topos=place)
Activation in particular parts of M1 causes movement in particular body parts on opposite side
What can brain lesions do to movement?
Stroke affecting one side of brain can affect movement of opposite side of body
Hemiplegia – paralysis of one side, hemiparesis – weakness of one side
How are movements coded in M1?
Cells in M1 have preferred direction of movement, populations of cells code direction of movement (vector coding)
M1 gets input from supplementary motor area/premotor area/primary somatosensory area + output to spinal cord (control muscles)
What did Gordon et al study?
2 parallel systems in M1 form integrate-isolate pattern
Body part specific for fine motor control of foot/hand/mouth
Somato-cognitive action network (SCAN) for integrating goals + whole body movement
What does the premotor cortex do?
Lateral premotor cortex – externally generated actions
Supplementary motor area (medial PC) - internally generated actions (eg. Well learnt sequences)
Areas more active in difficult bimanual tasks (cerebellum, SMA, pre-motor area)
What is sequence learning?
Faster/more accurate movements, change from effortful to automatic
Lower dorsolateral, higher SMA, lower lateral premotor cortex, lower primary motor activation
Repetitive TMS to block activity –> SMA only interfered with performing most complex sequence
What does the prefrontal cortex do?
Higher level, choosing what action to perform with which finger
Attention to action –> difficult/learning, longer term goals/intentions, not specific to action (generating random numbers)
What can lesions in the prefrontal cortex do?
Perseveration – repeat same action when no longer relevant
Utilisation behaviour – act on irrelevant object in environment
Disinhibition – Anti saccade task (look at opposite side than dot)
Frontal apraxia – not able to follow steps in routine tasks
What are antisaccades?
Study where people required to look opposite direction to target
Must inhibit tendency to look at target
What is Normal and Shallice model?
Contention scheduling – selects appropriate schema
Supervisory attentional system (SAS) - required for novel/less automatic actions
Why do perseveration/utilisation behaviour happen?
P: unable to change schemas when not appropriate
U: schemas activated by environment without SAS suppressing them
What can damage to parietal cortex (sensory motor links) do?
Damage to parietal cortex can lead to apraxia (inability to perform skilled purposeful movement)
