Week 11 motor control

Week 11 motor control

1. motor control

   • most actions require multiple muscles, precise timing, multiple components of movement
     • higher cognitive aspects of motor control include planing and tying, sequencing, imagery, expertise
       • listen to brain parts song by Aaron wolf

2. execution

   • primary motor cortex M1 - pre central gyrus - somatoptopic organisation (from body parts) - activation in particular parts of M1 causes movement of particular body parts on opposite side
     • stroke affecting one side of the brain can affect movement on the opposite side of the body - hemiplegia - paralysis of one side - hemiparises - weakness of one side
       • In M1 cells have a preferred direction of movement - populations of cells code for direction of movement - vector coding
         • primary somatosensory cortex - sends info to primary motor cortex - output to spinal cord - control of muscles

3. preparation of actions

   • premotor cortex - lateral premotor cortex = externally generated actions (responding to something that happens in outside world e.g someone randomly throwing a ball at you) - supplementary motor area (medial PC) internally generated actions e.g well learnt sequences
     • coordinating movements - cerebellum, SMA, pre motor area - all these areas more active on more difficult bimanual tasks
       • sequence learning - faster and more accurate movements - change from effortful to automatic - Toni et al 1998 - learning to produced sequence of 8 key presses - go down to almost 0 errors after a while
         • found that SMA increases use over time in sequence learning whereas lateral premotor cortex and primary motor went down
           • Gerloff et al 1997 - repriritve TMS to block activity SMA only interfered with performing the most complex sequence

4. higher level of motor planning

   • choosing what action to perform (e.g which finger, Frith et al 1991) - attention to action - when difficult or learning - longer term goals and intonations - not specific to action e.g generating random numbers
     • prefrontal lesions (e.g phines gage) - can produced preservation - repeat same action when no longer relevant - utilisation behaviour - act on irrelevant (or inappropriate) object in environment - disinhibition - e.g anti saccade task (required to look in opposite direction to the target - must inhibit tendency to look at target) - frontal apraxia - not able to follow steps in routine tasks (e.g making tea)
       • normal and shallice model - contention scheduling - selects appropriate scheme - supervisory attentional system - required for novel/less automatic actions
         • normal and shallice can explain action errors - preservation - unable to change schemas when no longer appropriate - utlilsation behaviour - schemas are activated by environment but don't have SAS to suppress them

5. sensory motor links

   • higher motor areas - damage to the parietal cortex can lead to apraxia - inability to perform skilled purposeful movement
     • ideomotor apraxia - idea and execution of action disconnected - retain knowledge of action - can recognise action performed by another - fail in pantomiming action (miming the action) - can perform sequence but not components

6. subcortical areas

   • cerebellum damage - cerebellar patients - can lead to action tremor - dysmertia - over and undershooting of movements - deficits in coordinating across joints, motor learning, timing
     • random saccade task - follow moving target moving randomly - cerebellar patients overshoot or undershoot on the looking
       • finger to nose test - in cerebellar patients they start to move the finger but tremor a lot - people with Parkinson's often do better on this task as they tremor more when they are relaxed but cerebellar parents don't as they have essential tremor which is consistent
         • Parkinsons disease - basal ganglia - bradykinesia - slow movement - tremor (resting) - rigidity - shuffling - death of dopaminergic cells in substantia nigra pars compacta
           • writing - in Parkinson's their writing gets smaller and may reduce while writing - fatigue - internal/external - more problems with internally generated movements than external - complex movement difficulties (bimanual sequences) - cognitive effects = attention shifting, everyday cognitive failures