Motor control (unit 1) Flashcards
Define motor control
The study of the neural, physical & behavioural aspects of human movement
Define Motor Learning
The study of the processes involved in the acquisition of a motor skill & the factors that enhance or inhibit an individuals capability to preform a motor skill
Define motor development
The study of the products & underlying processes of motor behaviour changes across the life span
What are the key issues in motor control?
- Degrees of freedom problem
- Serial order problem
- perceptual motor integration
What is the degrees of freedom problem?
How do we constrain degrees of freedom to produce coordinated movement; redundancy/ abundance
What is the Serial Order problem?
How do we sequence our time & movements appropriately
What is the issue of perceptual motor integration?
- How does perception influence behaviour?
- How does behaviour influence perception?
- Action slip: movement error in sequencing due to inattention
- coarticulation: accurate sequence + timing of movements in sequential tasks
how do we measure motor control?
Electromyography
What does electromyography show us?
movement patterns, amplitude of muscle activity & reaction time
What does the field of motor learning consider?
- how people acquire motor skills
- why do certain instructional procedures suit skills/ environments?
- What changes to performance might be observed when learning
What is coordination?
mastering the redundant degrees of freedom (movement possibilities of the musculoskeletal system)
coordination leads to ______, followed by____
as a result of….
control; skill; learning to refining those processes to move efficiently
How do we determine the number of degrees of freedom?
possible axes of rotation + directions of linear motion
What are affordances?
Opportunities for action within the environment
What are coordinative structures?
Functional relationships between parts of the motor system
What is redundancy?
There are meany different ways to achieve a task
What are the 4 main characteristics of human movement?
Flexibility
Uniqueness
Consistency
Modifiable
What is flexibility (a characteristic of human movement)?
Being able to achieve the same goal in a variety of ways (recruit different muscles & limbs; employ different postures & movements)
What is the principle of motor equivalence?
Left matches right (i.e. handwriting is the same no matter what limb)
What is uniqueness (a characteristic of human movement)?
Movement patterns are not rigidly constructed
No two movements are performed in exactly the same way (even if perfectly executed (subtle changes in posture & movement)
What is consistency (a characteristic of human movement)?
Stability of timing & spatial features across performances of the same task (movement pattern remains similiar)
What is modifiability (a characteristic of human movement)?
The capability to alter movement patterns in an unstable environment (modify movement to meet the ball in a better position)
What are the problems with consistency?
+ can’t adapt quickly want to be consist but flexible to adapt to environment
+ leads to overuse of specific muscle; joints; ligaments
What are 3 types of movement?
Timing mechanism: cyclic/ continuous movements
Discrete Movements: clear beginning & end
Sequential movement: group of discrete skills that form a complex movement
What are some perceptual- integration problems?
- Perception & action linked
- movement has ballistic & corrective phase
- Movement influences perception (& vice-versa)
What are some solutions to the degrees of freedom problem?
- Development of muscle synergies
- Taking advantage of the mechanical properties of limbs
3. Comfort & efficiency: use as little energy as possible (easiest) -> choose the most comfortable (end-state comfort)
What is the difference between control & coordination?
Coordination: process of constraining the degrees of freedom into a unit/ movement pattern
Control: fine tuning + scaling of a movement into our desired movement (manipulation of a situation to meet demands)
What is a scientific theory?
an explanation that has been tested and is widely accepted as valid (has to be supported & make predictions that are explained in future observations) made from past predictions
What are some paradigm shifts in theories of motor control?
1875-1900: ideomotor: emotional driven idea of movement
1900-1960: How people behaved in different contexts
1950-1975: Cognitivism: human & information processing
1975+: Holism: integrate all information as a whole
What are reflex theories?
Muscle reflexes are the basis of all movements
- afferent + sensory information from the environment determine movement
- Focus on nervous system & how it triggers, coordinates & activates muscles
How do Reflex theories explain complex movements?
Response chaining/ reflex chaining: external stimulus leads to a movement; leads to another… (William James 1842-1910)
What are the limitations of reflex theories?
+ anticipatory movements do not require any afferent input to initiate (no environmental input) so not explained by reflex theory
+ Doesn’t explain open loop control (cant require afferent input/ top down control)
What are Hierarchial theories?
Movement can happen without afferent movement (CNS directs lower centres; controller in cerebral cortex) John Hughlings Jackson 1835-1911)
What is the evidence that supports hierarchal theories?
- Deafferation studies
2. Experiments of movements of different complexities (complexity increases reaction time)
3. Antagonist still fired even if movement was blocked (so planned in advance) (trying to slow down a movement that hasn’t even happened)
What is generalised motor programme control theory?
Movement control is hybrid
initial = ballistic (no feedback)
During: feedback integrated, movement slows
What is the difference between open & closed control loops?
Open loop: no feedback
Closed loop: feedback integrated
What are the two components that movement is stored as a generalised motor programme?
Invariant parts (sequence; relative timing & relative forces) Variable parts (absolute timing & force & muscle selection)
What is the evidence of generalised motor programme control theory?
- feedback does not affect movement output in the last 150ms (basic RT for a simple movement) can’t inhibit movement after
- Relative timing of gait does not change with speed
- Writing style is transferred no matter method
What are the limitations of generalised motor programme control theory?
Cannot explain how direct perception works
“Optical flow; Affordances; Time-to-contact”
Cannot explain self-organizing systems (Hystheresis)
Why is it easier for our systems to perform anti-phase movement?
Creates a synergy
What are dynamic system theories?
system is capable to self-organising (adopt preferred patterns of movement; more stable; can change patterns fairly abruptly)
What are ecological psychology?
Environmental limitations create spontaneous designs
What is Hick’s law?
RT increases with the number of choices
What is Fitt’s Law’s?
speed- accuracy trade off
What is simple reaction time?
Minimal temporal & event uncertainty (one stimulus, one response)
what is choice reaction time?
Greater event uncertainty (Multiple stimulants & multiple responses)
What is discrimination reaction time?
Select from more than 1 stimuli; only 1 response
What variables influence reaction time?
Age, experience, caffeine, alcohol, intensity of stimulus, stimulus motility, response selection (simple vs choice vs discrimination); complexity of movement (response programming); accuracy demands; neurological & genetic disorders, developmental disorders, movement amplitude, inertial characteristics, memory
what is reaction time?
the time between a stimulus & movement initiation
what is movement time?
the time between movement initiation & movement completion
What is response time?
Reaction time + movement time
Only the initiation is planned for movements that last more than ____ms?
500ms
What are kinematic measures/ measurements of motion?
+ displacement
+ velocity
+ acceleration
+ Jerk (change in acceleration over time)
What is kinematic measurement?
the study of geometry pattern, or form of motion with respect to time
What is electromyography?
electrical activity of nerves (measure relative magnitude, timing, duration of muscle contractions)
What is the difference between agonist & antagonist muscles?
Agonist generates the movement
Antagonist slows down the movement
What is the Triphasic pattern?
First agonist burst -> antagonist burst -> second agonist burst
(Initiate -> slow down -> clamping)
What does kinetics measure?
Force on a body
How do we quantify coordination?
Compare limb segments = angle-angle diagram
Meausre ROM; movement quality, intralimb & interlimb relationships; used for cyclic movements
What is a phase diagram?
Joint angle vs Joint velocity
What does deviation of performance with respect to the goal of the task tell us about ?
accuracy & consistency of performance
What is constant error?
average error of performance; represents magnitude of error
(if make the same error repeatedly cancel each out) -
What is variable error?
measure of spread
What are the steps of motor planning & execution?
input -> deciding to act -> response selection -> scaling/ fine tuning -> execution) -> Feedback -» repeat
Where does the decision to act occur?
limbic system (Includes amygdala, cingulate gyrus, parts of hypothalamus, hippocampus)
what are the roles of the limbic system?
motivation, emotion, learning + memory, influences endocrine & autonomic nervous system (creates intent to act)
What does a decision to perform a move depend on?
goal, abilities, tendencies, subconscious/ conscious desicions
Where does response selection happen?
Association cortex
What is the role of the association cortex?
integrates sensory & motor functions; association cortexes are near primary sensory cortex of the same type
What is scaling & where does it occur?
What: selecting appropriate parameters (force; displacement; velocity; body segment; posture; muscle Groups) depending on input (environment/ body/ task goal)
Where: Projection system (Cerebrum: cerebral cortex (motor cortex; premotor cortex; supplementary motor area; parietal cortex); basal ganglia; cerebellum)
What the cerebellums role in movement?
Significant role in timing & motor learning (activates in advance of EMG trace – indicates involvement in planning, timing, learning
Involved in regulation of muscle tone & coordination (shown damage to cerebellum leads to hypotonia & ataxia)
What are the roles of the basal ganglia?
+ activation or retrieval of movement plans
+ scaling of movement parameters (velocity , amplitude, direction)
+ Movement preparation
What is the role of the motor cortex?
trigger centre (controls muscle activity, force & direction) -> receives feedback from the movement it triggers
What is the role of the premotor cortex?
Controls proximal muscles: trunk & shoulders & coordinates anticipatory postural adjustments (adapts the body position for movement & prepares postural muscles to stabilise for movements)
What is the supplementary motor area responsible for?
High level planning & production of complex movement sequences
What is the role of the parietal cortex?
association between sight & sound, movement & sensory, consequence, etc…
(Damage is associated with apraxia & spatial neglect)
What is the role of the brain stem?
Transports signals from spinal cord to brain; transport motor commands to spinal cord
What causes muscles to contract
Acetylcholine being released by motor nerves
What are the role of alpha motor neurons?
To innervate skeletal muscle & cause muscle contractions
What % of neutrons cross the midline at the medulla?
75%
What corcospinal tract do motor neurone that cross the medulla travel in?
Lateral
What muscles do motor neurone in the lateral corticospinal tract control?
Distal muscles on the opposite side
What do motor neurone that travel via the ventral corticospinal tract control?
Axial muscles on both sides of the body
What is the major function of the vertebral column
Protection of the spinal cord
What is the size principle
smaller more fatigue resistant motor units are recruited first (have lower thresholds)
What is the path of an afferent nerve?
Takes sensory info from the skin through the dorsal root
What is the path of efferent nerve
exits spinal cord via the dental root, taking information to muscles
Define proprioception:
Info provided by the sensory receptors within muscles, tendons, joints & skin
What is the role of muscle spindles?
Give feedback of length of muscle (muscle stretch)
What are the role of 1a afferent neurons?
Neurons that carry information up to spinal column
What are the role of gamma motorneurons?
Gamma motoneurons carry neural impulse from CM}NS to muscle spindles
What do Golgi tendon Organ’s do?
Give feedback of tendon stretch
What are Joint receptors?
Sensory endings in the joint; provide information of the joint angle
What are the Cutaneous receptors?
receptors in skin that measure deformation
What is the stretch reflex pathway?
- Muscle is stretched, muscle spindle fires
- Impulse from afferent neuron (1a) to spinal column
- 1a synapse on agonist motor neuron & antagonist inhibitory motor neuron
- Agonist Alpha MN is stimulated
Antagonist muscle in inhibited - muscle contracts, spindle organ stops firing
What is the Golgi tendon reflex pathway?
- muscle contracts -> Golgi tendon organ dires
- Afferent neuron synapses into inhibitory interneuron
- Interneuron synapses onto a motor neuron
- inhibits agonist
what is the role of the association cortex?
integrates functions, recognises & makes sense of & integrates response
what are spinal reflex (long reflex loops)
subconscious adjustments in limb/ body position (40-80ms)
what does damage to the cerebellum cause?
Disruption of coordination
What is a sensation?
Physical stimulus registered by a sensory organ, which decode & create electrical signal (transduction)
What is the threshold intensity dependant on?
- Location & surface area
- Activation threshold
- Frequency & spatial summation
- Sensory adaption
What do interreceptors show?
State of internal organs
What do proprioceptors show?
Information about our movements/ position, muscle receptors, joint receptors, cutaneous receptors & vestibular system
What is sensory adaption?
Over time get used to stimulus & stop registering
What do exteroceptors show us?
Info about the movement of objects in the environment
What are joint receptors
sensory endings in the joint to provide info on the joint angle
What are cutaneous receptors?
Mechanoreceptors in the skin to measure deformation & give info about touch, pressure & displacement
What is the role of the vestibular system?
Gives info about the balance & position of head triggered by linear & angular acceleration
What is the vestibular system?
3 semicircular canals filled with liquid & hairs that give orientation in every direction
How are signals sent in vestibular system?
Hair moving depolarises nerve
What are otolithic organs?
Move on top of fluid membrane to help move hair (can detect 0.1 sec acceleration)
What is vertigo caused by?
otolithic crystals getting stuck in canals & overstimulating hair cells
What do gamma neurons do?
Send info to muscle spindles to desensitise to expected executed movements
What is the pathway of a neural signal?
spinal nerves -> spinal column -> thalamus -> primary somatic-sensory cortex -> association area
touch proprioceptors ______ & crossover at ________. This takes _____.
dorsal column pathway
Medulla
80-100ms
Pain/ temp enter ____________ & cross __________. This takes _____
spinothalamic pathway
Immediately
1-40 ms
What does damage to the dorsal pathway cause?
Loss of tactile discrimination & kinaesthetic sensation
What does damage to the spinothalamic pathway cause?
Loss of Pain & Temp sensation
What does the damage to thalamus cause?
Thalamic syndrome/ central pain syndrome
What is the role of the thalamus?
Filters out irrelevant inputs & directs others to specific area in cortex
What is the role of the primary somatosensory cortex?
Provides meaning
What % of sensory info comes from vision?
80-90%
What are the roles of vision in motor control?
- Monitor position of objects
- Maintain upright posture & navigation
- Evaluating performance quality
- Interact with/avoid objects
- Assist with motor prep
What anatomical structures are involved in vision?
\+ light \+ retina \+ transduction \+ Electrical impulses \+ Brain (visual cortex; occipital lobe)
What are the role of rods?
Peripheral vision (very sensitive to light)
What does the visual cortex respond to?
light/ dark edges, orientation, length & movement of edge
What are the 5 types of eye movement?
Vestibular- ocular reflex: stabilises eye when head moves
Optokinetic reflex: maintains stable image on retina
Smooth pursuit: track slow moving objects in space
saccades: shift gaze between interest points
Vergence: brings objects of different depths into focus
What is the ventral visual stream responsible for?
Object identification & recognition
What is the dorsal visual stream responsible for?
Spatial awareness & Guided actions
The temporal lobe receives the _______ visual stream and is responsible for perception
Ventral
The Parietal lobe recieves the ________ visual stream and is responsible for action
Dorsal
What is some evidence of perception-action coupling?
+ visual illusions decieve both perception & action
+ There is a positive association with the heaviness of an object & perception of the distance of a target
+ People with broad shoulders percieve doorways to be narrower
What are the two physiological views of visual perception?
- Cognitive (indirect view)
2. Ecological (direct view)
What is the cognitive (indirect view) of visual perception?
Visual info is only sensible by interference
What is the ecological (direct view) of visual perception?
Perception & action are tightly coupled
What roles does vision have in motor control
- Balance (soure of postural stability)
- Locomotion (optical flow uptake causes adjustments, prepares motor system for movement & feed forward role for vision)
- Interception of moving targets (time to contact variable –> Tau/T)
How much time does visual feedback processing require?
215-250ms
What is looming?
Increase in circumferences as an object approaches (directly proportional to T)
What are 3 vision & movement disorders?
- Optic Ataxia: Hand movement accuracy to object impaired
- Visual agnosia: Object recognition impaired but grasp okay
- Hemiplegia: vision assists performance
What is the goal of the visual system?
Object identification & location (give directional guidance)
What is the goal of the gaze system?
To bring images onto the Retina (through eye & head movements)
How can we measure eye movement?
Eye Tracking
+ light is directed to eye and the light reflection is recorded
+ eye rotation is extrapolated
+ from this we can deduce the direction of gaze
What are fixations
Rest on a single object (within 3 deg for 100ms +)
What are saccades
Rapid eye movement (no information picked up)
What is smooth pursuit?
slower tracking eye movements
Why do we track eye movement?
- Lab & Field testing
- Identify underlying mechanisms
- Practice history profiling, training interventions
What is expert-like gaze behaviour?
Efficient Visual Search:
- Attention is guided to target immediately (rest of scene irrelevant)
- Extended Visual Span: Pre-attentive processing of the scene before selective attention is directed to specific locations
- Selective attention: guided by long term memory
Experts have ____ & _____ fixations on relevant areas; _____ scattered gaze behaviour, identify ________ & extract info from _____ vision
less & longer
less
Task-relevant info
Peripehral
Anxiety definition:
unpleasant psychological state in response to perceived stress/ threat
Fear Definition:
increased arousal to a threatening stimulus (anxiety more enduring & undifferentiated)
What are the three components of anxiety:
- Cognitive:
Negative expectations & concerns about self, situation & consequences - Somatic:
Physiological response - Behavioural:
face tension, rapid speech, agitation, restlessness, jerky & inefficient movements
Cognitive anxiety is experienced ____ before.
Somatic anxiety is experienced _____ before an event.
48hours, ~a couple hours
What is choking under pressure?
Acute decrement in performance ability despite ability + motivation
What are some causes of choking under pressure?
- evaluative udience
- rewards
- Competition
What are the 2 attentional theories?
- Distraction theories
+ focus on task & worrying thoughts competing for attention - Self-focus theories
+ un-automate movements
What model are self focus theories based on?
learning model of skill acquisition:
- cognitive stages
- association stage
- Autonomous stage
What is quiet eye an indicator of?
efficient visual attention control
At what point do skilled athletes supress their vision?
When the ball occludes the target as all nessecary info is processed
What is the quiet eye duration?
Portion of final fixation from onset to first observable movements of hands
The quite eye is associated with _____ performance & ______ fixations before initiation
Better
Long
