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DPT > MOTOR: Exam I > Flashcards

MOTOR: Exam I Flashcards

0
Q

Fitts and Posner

    • Cognitive stage
    • Associative stage
    • Autonomous stage
A

Cognitive
– Thinking about learning
– Experimenting with strategies
= Most basic stage of motor skill acquisition

Associative

    • Refining selected strategy
    • Skill develops and improves with practice

Autonomous
– Automaticity of skill
– Attention diverted to scanning environment or multi-tasking
= Expert stage

NOTE: Not truly autonomous if performance declines when distracted

    • May still be highly skilled/”expert”, but not totally automatic
    • Truly “perfect” performance is rare; usually some error due to distraction
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1
Q

Theories of Motor Learning and Performance

    • Fitts and Posner
    • Newell
    • Schmidt and Lee
    • Gentile

NOTE: Basic elements

A

Fitts and Posner

    • Cognitive stage = thinking
    • Associative stage = refining
    • Autonomous stage = automaticity

Newell

    • Novice stage = basic patterns
    • Advanced stage = coordination
    • Expert stage = controlled

Schmidt and Lee

    • Short-term, implicit memory
    • Schema: Recall, Recognition

Gentile

    • Closed to open skills
    • Demands of environment
      • Context vs. Regulatory Variability
    • Requirements of action
      • Object manipulation
      • Body transport
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2
Q

Newell

    • Novice stage
    • Advanced stage
    • Expert stage
A

Novice

    • Understanding basic patterns of movement
    • Few degrees of freedom
    • Highly variable movements trial to trial

Advanced

    • Coordination
    • Increasing degrees of freedom
    • Adds cognitive element
    • Increasing consistency of movement

Expert

    • Controlled
    • Modifying movement to perform desired task (as needed)
    • Variability is a sign of skill
      • Consistent outcome, but pattern of movement may vary
      • Ability to adapt to changes in environment

NOTE: Difference in variability between novice and expert

    • Novice variability in outcome
    • Expert variability in pattern to achieve outcome
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3
Q

Schmidt and Lee

    • Development of schema
    • Components of schema
A

Schema = set of rules for performing a movement

Development of schema: All add to our memory of movement
– Short-term, implicit memory of movement components
– Initial movement conditions (e.g., body position, object weight)
– Motor program parameters = patterns of muscle activity
– Knowledge of results (KR) = outcomes or goals of movement
NOTE: Need to decide what error range is acceptable for successful outcome
– Goal of training is to narrow range, but experiencing error critical to learning
– Even experts never perform same task same way every time
– Sensory consequences = experience or perception of movement
– Feedback from multiple sensory systems (e.g., sight, feel, sound)

Components of schema:
– Recall = Set of rules for movement under different conditions
– Common elements of action and organization (i.e., temporal, rhythmic)
– Memory of movement in different environments/conditions
– Expert has ability to adapt to ensure successful outcome
– Recognition
= Rules of movement coupled w/ current conditions
&raquo_space; Expected outcome
– Expert element of schema
– Recognizing what to do under different conditions

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4
Q

Gentile

    • Two-dimensional classification system
      • Demands of environment
        • Regulatory variability
        • Context variability
      • Requirements of action
    • Closed skill
    • Open skill
A

Two-dimensional classification system:
= Matrix combining demands of environment X requirements of action
– Spectrum of complexity from closed to open skills

– Demands of environment:
– Regulatory variability = stability of environment
Ex: Moving escalator vs. stairs
– Context variability = persons movement in environment
Ex: Standing still vs. balancing on opposite legs
– Progression: Low to high complexity
– Neither RV nor CV
&raquo_space; Only CV&raquo_space; Only RV
&raquo_space; Both RV and CV
– Requirements of action:
– Progression: Low to high complexity
– Neither body movement nor object manipulation
&raquo_space; Only object manipulation&raquo_space; Only body movement
&raquo_space; Both object manipulation and body movement

Closed skill = Performed in stable and predictable environment
Open skill = Performed in unstable and unpredictable environment
– Must use perception and decision-making to adjust movement

NOTE: Most skills somewhere between totally open or closed

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5
Q

Definition of terms:

    • Motor learning
    • Motor performance
    • Motor control
A

Motor learning = acquiring skilled movement as result of practice
= Internal process that determines capability
– Practice = process of squiring skilled movement via repetition
– Characteristics:
– Improves with practice and experience
– Assessed by observing performance for several trials
– Stable under varied circumstances (repeated trials)

Motor performance = observable action or skill

    • Fluctuates day-to-day and trial-to-trial
    • Characteristics:
      • Influenced by:
        • Fatigue, pain, and conditioning
        • Motivation
        • Attention (distraction)
        • Physical conditions
        • Environment

Motor control = study of neural, physical, and behavioral aspects of movement

    • How our brains and bodies and behaviors relate to this movement
    • How we control the movement skill: brain, muscles, and behaviors
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6
Q

Types of skill:

    • Motor skill
    • Cognitive skill
    • Discrete skill
    • Serial skill
    • Continuous skill
A

Motor skill = success determined by quality of movement
– Knowing “how” to do the movement
– Emphasis placed on correct performance
– Decision making is minimized and motor performance is maximized
Cognitive skill = having a strategy for movement
– Knowing “what” to do
– Movement less important than decision guiding movement
– Decision making is maximized and motor performance is minimized

NOTE: Most skills are a combo of motor and cognition
– Usually new skills require more cognition than more proficient skills

Discrete skill = distinct beginning and end
Serial skill = discrete actions linked together
Continuous skill = no distinct beginning and end

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7
Q

Feedback:

    • Intrinsic
    • Extrinsic or Augmented
    • Knowledge of Performance (KP)
    • Knowledge of Results (KR)
A

Intrinsic = info about movement from sensory systems
– Can be confusing since we get input from many systems
Extrinsic = supplemental info from command or cue
NOTE: Manual and verbal cueing would be both intrinsic and extrinsic

KP = info about movement or movement pattern used to achieve outcome
– Compared to intended movement
KR = info about outcome of movement
– Compared to intended outcome

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8
Q

Practice:

    • Massed
    • Distributed
    • Constant
    • Variable
    • Whole
    • Part
    • Guidance
    • Discovery
    • Random
    • Blocked
    • Transfer of practice
    • Mental practice
A

NOTE: Easier&raquo_space; Harder

Massed = time in trial > interval time
Distributed = time in trial < interval time
– More difficult with longer interval between trials (requires recall)

Constant = static or stable conditions for practice
Variable = differing conditions for practice
– Changing surfaces, external environment, etc.

Part = break task into components or interim steps 
Whole = practice entire task as is

Guidance = physical or verbal instructions through task
Discovery = trial and error
– Discovery can be frustrating, unsafe, time-consuming
– Try to become more efficient in discovery

Blocked = practice one task for period of time, then move to other
Random = practice different tasks in random order
Transfer = better transfer between similar skills/movements
Mental = thinking about task (w/o doing) may improve performance
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9
Q

Recovery of function

    • Compensation
    • Spared function
    • Stages of recovery
    • Factors affecting recovery
A

Recovery = regaining motor skill
Compensation = learning new way to achieve same outcome
Spared function = some ability remaining that can be used

Stages:

    • Spontaneous = suddenly able to perform skill
    • Forced = prolonged process of recovery

Factors:

    • Age
    • Injury or lesion (type, extent, location)
    • Pre-injury motor skills (e.g., child still developing)
    • Post-injury factors (e.g., PT, meds, tissue healing)
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10
Q

Problem-Based Approach

    • Who?
    • What? Why?
    • Where?
A

= Key to learning is ability to ask right questions:

Who = characteristics of learner

    • Abilities
    • Experience
    • Motivation

What/Why = goal of task

Where = target context

    • Environment task will take place
    • Attempt to make practice setting as close to actual
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11
Q

Levels of sensory input

    • Interoception
    • Exteroception
A

Interoception = internal sensory feedback

    • Information from inside the body
    • Hunger, fullness, thirst, and pain

Exteroception = sensory feedback from outside body (external environment)
– Vision = dominant source
– Hearing = “audio flow” indicates location, direction, and directs attention
– Olfaction = may trigger movements or reactions
– Proprioception
= Info about body’s position and orientation in space
– From vestibular system, muscle, joints, and cutaneous receptors
– Vestibular = orientation of head relative to gravity
– Other receptors = location of body parts in space
Kinesthesia = Info about limb movements and muscle contractions

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12
Q

Proprioceptive sensory mechanisms

    • Muscle spindle
    • GTO
    • Joint receptors
    • Cutaneous receptors
A

Muscle spindle:
– Located within skeletal muscle fibers (extrafusal)
– Detects muscle lengthening
– Rapid length change&raquo_space; Stretch reflex = Muscle contracts
– Slow length change&raquo_space; No reflex
– Afferent fibers carry signal to spinal cord
– Motor neurons signal spindle fibers to reset length (intrafusal)
&raquo_space; Remains sensitive to length changes

GTO: Golgi Tendon Organ

    • Located in musculotendinous junction
    • Detects changes in muscle tension (force generation)
    • Inhibits muscle force (damps) to protect muscle and tendon

Joint receptors:

    • Free nerve endings
    • Pacinian corpuscles
    • Ruffini endings
    • Golgi type endings

Cutaneous receptors:

    • Free nerve endings
    • Pacinian corpuscles
    • Ruffini endings
    • Meisners corpuscles
    • Merkels discs
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13
Q

Joint receptors:

    • Free nerve endings
    • Pacinian corpuscles
    • Ruffini endings
    • Golgi type endings

Cutaneous receptors:

    • Free nerve endings
    • Pacinian corpuscles
    • Ruffini endings
    • Meisners corpuscles
    • Merkels discs
    • Krauses end bulbs
    • Hair follicle receptors
A

Joint receptors:

    • Free nerve endings = pain and non painful stimuli, biochemical stimuli
      • Ligaments, synovium, fat pad, joint capsule
    • Pacinian corpuscles = vibration (high freq.), acceleration, high vel. change in joint position
      • Fibrous layer of joint capsule
    • Ruffini endings = vibration (low freq.), amplitude, stretch of capsule
      • Fibrous layer of joint capsule
    • Golgi type endings = compression of capsule, tension, stretch of ligaments
      • Ligaments, joint capsule

NOTE: All provide info to central processes, but none are conscious except pain

Cutaneous receptors:

    • Free nerve endings = pain and non painful stimuli, biochemical stimuli, temp
    • Pacinian corpuscles = vibration (high freq.), pressure (deep touch)
      • Located in dermis (deeper), resets itself
    • Ruffini endings = vibration (low freq.), stretch of skin
    • Meisners corpuscles = light touch (not sustained), vibration (freq. < 50Hz), speed of stimuli
    • Merkels discs = light touch (sustained, very sensitive)
    • Krauses end bulbs = touch, pressure
    • Hair follicle receptors = movement of hairs on skin

NOTE: Incredibly rich, sensitive, and important source of info
– Respond to chemical, thermal, and inflammatory stimuli

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14
Q

Sensory pathways

    • Spinothalamic pathway
    • Spinoreticular pathway
    • Dorsal column pathway
A

Spinothalamic = pain and temperature
– Dorsal root > Dorsal horn (synapse 1)
> Cross in anterior cord > Ascend in anterolateral tract
> Thalamus (synapse 2) > Sensory cortex

Spinoreticular = pain
– Dorsal root > Dorsal horn (synapse 1)
> Cross in anterior cord > Ascend in anterolateral tract
> Reticular activating area (multiple synapse)
> Sensory cortex (multiple areas)

Dorsal column = touch, pressure, vibration, and proprioception
– Dorsal root > Ascend in dorsal column
> Cuneate or gracile nucleus (synapse 1)
> Cross in anterior medulla
> Thalamus (synapse 2) > Sensory

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15
Q

Visual system:

    • Focal vision
    • Ambient vision
    • Visual dominance
    • Visual capture

– Optical flow

A

Focal vision = identifies objects in center of visual field
– Conscious and affected by light (center of retina = fovea centralis)
– “What is it?”
– Slow, exteroceptive loop (via cerebellum to info processing) = conscious
Ambient vision = detects orientation of body in environment
– Non-conscious and peripheral (light moves across retina)
– Used a lot in movement control
– “Where am I?” or “Where is it?”
– Fast, inner loop (output to motor program) = nonconscious

Visual dominance = visual info dominates info from other senses
– Primary source of sensory input
Visual capture = visual info captures attention more easily than other sources of info

Optical flow = detects patterns of light moving across retina (ambient vision)
– Perceives:
– Motion
– Direction (left or right, towards or away)
– Velocity (across, towards, or away)
– Position
– Stability
– Size of object
NOTE: Perception of movement can be confusing (you moving in environment vs. environment moving around you); optical flow perceives movement of environment, vestibular system helps you determine if visual info is real (vs. you are moving)

16
Q

Compensations for muscle movements

    • Mechanical
    • M1
    • M2
    • Triggered response
    • M3
A

Compensations = corrections for error in movement

Mechanical = tissue stiffness helps stabilize
M1 = monosynaptic reflex
– Latency = 30-50 ms
– Very rapid, unconscious, limited muscles
– Inflexible, little environmental impact
– No adaptability, effect of instructions or effect of alternatives
M2 = polysynaptic reflex
– Latency = 50-80 ms
– Longer pathway, still unconscious
– Not voluntary, but can be modified/inhibited consciously (involves higher brain centers)
– Low adaptability, effect of instructions or effect of alternatives
Triggered response = rapid, learned, well-practiced response
– Latency = 80-120
– “Wineglass effect”, subcortical but conscious, cutaneous receptors
– Moderate adaptability, effect of instructions or alternatives
M3 = voluntary reaction
– Latency = 120-180 ms
– Much longer pathway (> sensory cortex > motor cortex > muscles)
– Very large adaptability, effect of instructions or alternatives
– Influenced by instruction, anticipation, and stimulus responses
NOTE: Any additional demands on attention will slow reaction time even further

17
Q

Closed-Loop Control System

    • Characteristics
    • Components

Open-Loop Control System

    • Characteristics
    • Components
A

Closed-Loop = Ongoing modification of movement using peripheral feedback

    • Uses feedback, error detection, and correction processes during movement
    • Slow, deliberate movements (Requires sensory input to guide movement)
    • > 200 ms (M3 voluntary reaction time): Corrections occur a few 100 ms after error
    • Effective in unpredictable and unstable environments
    • Components:
      • Input = Environment or desired action
      • Executive = Determines actions (motor planning areas of brain)
      • Comparator = Error detection (cerebellum)
        • Compares efferent copy of motor plan from brain w/ sensory feedback
      • Effector = Carries out movement (spinal cord, motor tracts, muscles)
      • Output = Outcome of action
      • Feedback = Info about current state (sensory receptors, afferent pathways)

Open-Loop = Rapid, automatic movements w/ no correction during movement
– Response selection and programming occur before movement (preplanning)
– Triggered as a whole; No error detection or sensory input during movement (too quick)
– < 200 ms (only reflex corrections M1 and M2)
– Effective in stable and predictable environments
– After movement (subsequent trials): Error signal processed (stimulus ID stage)
&raquo_space; Movement correction chosen (response selection)
&raquo_space; Modifications organized and initiated (response programming)
– Components: Input&raquo_space; Executive&raquo_space; Effector
– NO COMPARATOR
– Output&raquo_space; Feedback only after movement is complete

NOTE: Closed and open loop do not act in isolation

18
Q

Motor Program as Open-Loop System

    • Components
    • Characteristics
      • Attention
      • Practice
      • Learning
      • Storage
A

Components
– Input = Stimulus (e.g., ball is thrown) (sensory systems)
– Executive (cortical areas: frontal, parietal, temporal, occipital)
– Stimulus Identification (e.g., see ball thrown)
– Response selection (e.g., decision to swing bat)
– Response programming (e.g., how fast and hard, where to swing)
= Preplanning based on sensory inputs and past experience
– Motion and force predetermined
– Effector
– Motor program = code for movement (premotor/motor areas, basal ganglia)
– Spinal cord (and motor tracts) = signal for movement
– Muscles = perform movement

Characteristics

    • Stages of processing used to develop motor program (executive)
    • Little attention needed for movement once program starts
    • Effect of practice
      • Program can control longer sequences
      • Movements become more elaborate
    • Effect of learning
      • Less time needed for programming
      • More focus on higher-level cognitive function
    • Stored in long-term memory for use in short-term memory PRN
19
Q

Support for Motor Program Theory:

    • Reaction time
    • Deafferentiation
    • EMG activity
A

Reaction time:
– Reaction time is longer when followed by more complex movement
= More time needed to organize system
– More elements or more limbs involved
– Example: finger lift followed by simple or complex sequence

– Deafferentiation
= Severing sensory nerves (no sensory input)
– Monkeys still able to perform learned activities (gross motor)
– Indicates sensory feedback not needed for motor program (open loop)
– Example: able to swing from branches but not do fine motor

    • EMG activity
      • Electrical activity same for muscles when limb movement is blocked
      • No feedback from limbs (not moving) but program remains in muscles
20
Q

Motor Programs:

    • Attributes
    • Roles
A

Attributes

    • Specific muscles to perform action
    • Order of muscle activation
      • Proximal before distal (postural modifications first)
    • Force of contractions
    • Timing and sequencing
    • Duration of contractions

Roles

    • Define and issue commands
      • Require commands (both for closed and open)
    • Organize DoF of movement
      • How body will move (sequence, timing, etc.)
    • Make postural adjustments
      • Proximal muscles first for stability
    • Adapt reflexes for goal
      • Reflexes used to correct movements
21
Q

Central Pattern Generator

    • Differences with motor program
    • Examples
    • Reflex reversal phenomenon
A

CPG = Centrally located control mechanism

    • Produces repetitive, genetic movements; Triggered by stimulus (environmental input)
    • Complex reflex reaction, but v. rudimentary motion
    • Stimulation at level of cord, not cortical control needed

Difference with motor program:

    • CPG = Genetically defined (NOT learned)
    • Motor program = Learned activities; Developed w/ practice; Used to control learned activities

Examples:
– Locomotion in animals, Swimming in fish, Chewing in hamsters, Slithering in snakes
NOTE: Some elements of human gait, otherwise too complex for CPG only

Reflex reversal:
= Reflex response differs depending on phase of movement
Example:
– Pressure on dorsum of foot:
– Contact w/ surface (heel strike) = Stance phase&raquo_space; Limb EXT (PF)
– Leaving surface (toe-off) = Swing phase &raquo_space; Limb FLEX (DF)
NOTE: Increase stimulus causes increase motion
– Tactile cue during swing increases FLEX
– Tactile cue during stance increases EXT

22
Q

Generalized motor program

    • Definition
    • Modifications
      • “Surface features”
A

= General movement pattern stored in long-term memory
– Defines pattern of movement not specific movement
– Modified for use in specific movements
– Adapted to meet demands of task by selecting different parameters
– Selecting different parameters produces different surface features
NOTE: Solves problem of storage space

Surface features:
= Easily changeable components of movement pattern
– Result from changing parameters/constraints of movement
– Parameters set by demands of task

    • Timing or speed (e.g., throwing fast or slow)
      • Similar pattern of movement regardless of speed
      • Change movement time while preserving fundamental timing structure
      • Same timing and sequence of events that can run at different speeds
    • Amplitude (e.g., writing large or small)
      • Patterns of acceleration same for large or small movements
      • Vary amplitude of movement by changing acceleration (force)
      • Same movement structure just big or small
    • Direction (e.g., throw left or right)
      • Same movement structure directed high, low, R or L
    • Limb and muscles used (e.g., writing on blackboard vs. check)
      • Same movement structure w/ different effectors
23
Q

Coordination:

    • Definitions
    • Temporal organization
    • Scientific theories
A

Coordination
= Behavior w/ two or more DoF in relation to each other
= Organization of different elements of complex body/activity
– Produces effective, skilled activity

Temporal organization
= Timing or rhythms of movement patterns
– Different timing or rhythm increases difficulty
– Easier if beats are the same (even if out of phase)

Theories:
– Motor program concepts
– Discrete tasks of short duration (only open loop)
– Preplanning is critical, feedback is not
– Examples: flipping switch, swinging bat
– Self-organizing systems
= Movement pattern or rhythm dominates, regardless of intent
– Continuous, rhythmical tasks of long duration (closed and open loop)
– Examples: swimming, running, driving, walking

24
Q

Reach-and-grasp

    • Type of task
    • Components
    • Effects of:
      • Moving block farther away
      • Moving arm faster
      • Closing eyes
      • Adding second limb
      • Adding limb w/ different movement
A

= Discrete, mostly open-loop
– Components
– Transport: Ballistic arm movement (temporal process)
– Grip-formation: Prepares hand to capture object
– Hand opens prematurely, Refines movement as it approaches object
– Widest grip at peak deceleration of arm (Spatial process)
NOTE: Temporal component coordinates movement
– Relative timing does not change despite speed or size of object

    • Effects of:
      • Moving block farther away
        • Arm movement changes (has to go farther)
        • Hand movement stays same (grip formation same) = Widest at peak deceleration
      • Moving arm faster or closing eyes = Hand opens wider
        • Compensates for anticipated error (increased spatial variability)
        • Still widest at peak deceleration
      • Adding second limb
        • Difference distances
          • Temporal measures same for both arms = Widest grip and grab objects at same time
          • Slower than unilateral (More to preplan and more to coordinate)
            • Closer limb slows down to match farther limb movement
      • Adding second limb w/ complex movement
        • Grasp object at same time
        • Arm w/ simple movement slows or slightly mirrors complex movement
        • Hard to temporally dissociate two arms (Pattern of complex mvmt detected in mvmt of other arm)
25
Q

Human gait: Walking and running

    • Type of task
    • Triggers for shift from walk to run
A

Type of task:

    • Continuous, self-organizing
    • Two generalized motor programs (walk vs. run)

Triggers:
– Energy = Inefficiency in metabolic costs
– May be primary catalyst for transition
– Stability = Instability causes transition
– Increasing speed while walking COM shifts forward
– Limbs dissociate&raquo_space; Transition to run
– Vision = Gait speed increases when perceived speed increases
NOTE: Most likely transition occurs based on multi-sensory inputs

NOTE: Self-selected walking speed most efficient (healthy people)
– Other factors may limit speed in impaired people (e.g., pain, fear)

26
Q

Coordination in Continuous Tasks:

    • Timing (in-phase vs. anti-phase)
    • Speed (frequency)
    • UE w/ LE
      • Contralateral vs. Ipsilateral
      • Direction of movement

Self-organizing basis

A

Timing:
– In-phase = same time
– Anti-phase = alternating
= Same kinematics (forces) and timing regardless

Speed:
– As speed increases stability decreases:
– Switch from in-phase to anti-phase
= System moves toward greater stability
Example: Alternating finger tap
– Switches to in-phase tap at 2.25 Hz

UE and LE:
– Easier to coordinate contralateral limbs
– Easier to coordinate movements in same direction
Example: PF (extension) and wrist extension w/ palm up

Self-organizing = systems moves toward stability
– Switch to in-phase as speed increases
– Easier to switch from anti-phase to in-phase
– Contralateral movements have less error
= Continuous actions modified due to decrease in stability
– Phase transition
– Changes basic form of pattern

27
Q

Invariance or invariant features

    • Relative timing
    • Surface features
    • Parameters
A

Invariance
= Constant characteristics of a movement
– Despite changes in surface features
– Relative timing ~ Fundamental timing structure of movement
– Ratios of durations of movement features
– Ex) Rel. contribution of ind. mm same regardless of movement time

NOTE: Applies to walking, running, reach and grasp

– Surface features
= Easily changeable components of movement
– Modified as a result of changing parameters
– Speed of movement
– Size of action (amplitude)
– Trajectory of movement
– Forces used to produce action
– Parts of limb used for action
– Parameters
= Variable inputs to a generalized motor program
– Same as above

28
Q

Spatial accuracy

    • Speed-accuracy tradeoff
    • Closed vs. open loop
    • Fitts Law
A 
Spatial accuracy
= Measure of variability in movement's endpoint
-- Decreases with increases in 
   (1) Movement distance
   (2) Movement speed (decreased time)

Speed-accuracy trade off
= Substitution of accuracy for speed or vice versa
– Closed loop: Accuracy is goal
– Time for feedback and correction during task
– Open loop: Speed is goal
– No feedback or correction during task
– Tradeoff applies to both open- and closed loop

Fitts Law
= Movement time (MT) linearly related to index of difficulty (ID)
– MT = log (2A/W)
A = movement amplitude (distance to target)
W = target width
– Changing size of target
NOTE: Applies to combined open- and closed-loop tasks
– Blend of programmed actions and feedback
– Initial part of movement is open-loop
– Later part involves error detection and correction (200-1000 ms)

29
Q

Violations of Speed-Accuracy Tradeoff

    • Timing accuracy
    • Forceful movements
A

Timing accuracy
= Measure of variability in movement time
– Target time for task to take place
– End of movement occurs close in time to another event
***Variability INCREASES as MT INCREASES (speed decreased)

Force of movement
– Fastest but most forceful movement = less spatial variability
– Inverted V relation between force/MT and spatial error
– Highest force = fastest (shortest MT)
– Slowest and least forceful = lowest variability
– Second slowest at 50% max torque = highest variability
– Reason? Large forces (>70% max torque) have lower force variability
– Force production is more consistent for near maximal force
– Resultant trajectory is consistent spatially
NOTe: Limited number of studies, simple linear arm movements

30
Q

Sources of Error in Rapid Movements

    • CNS
    • Reflexes
    • Nerve impulses
    • Muscle force
A

NOTE: Errors can occur at all points in system

CNS:
– Noisy or inconsistent central processes
– Converting nerve impulses to muscle contractions
– Movement planning processes (response selection)
– Stimulus identification
**Errors in commands for motor program
Reflexes:
– Contribute variability to muscle contractions
Nerve impulses:
– Errors in efferent and afferent signals despite same input
Muscle forces:
– Up to 70% max force force variability increases
– > 70% max force variability levels off and decreases near max
– Multiple mm contribute to single movement
– Error in any or all increases error in resultant movement
– Minimize # mm (degrees of freedom) to decrease error
– Minimize gravity
– Gait train on knees

31
Q

Movement variability: Good or bad?

    • Evidence for good
    • Evidence for bad
A

– Depends on goal of task

Good:

    • Postural sway in developmentally delayed children < normal children
      • Ability to move COM outside BOS allows exploration of environment
    • Post-concussion less variability in sophisticated measures of postural sway

Bad:

    • Dysmetria:
      • Finger-to-nose test for cerebellar injury&raquo_space; Problems with endpoint accuracy
    • Gaze instability:
      • Overshooting saccades when trying to fix gaze on target
32
Q

Theories of motor control (in brief)

    • Reflex theory
    • Hierarchical theory
    • Motor programming theory
    • System theory
    • Dynamical action theory
    • Ecological theory
A

– Reflex theory = All movements (simple or complex) due to reflex response
&raquo_space; Clinical utility: Reflexes influence movement
– Hierarchical theory = Higher level CNS centers control lower levels
– Higher levels inhibit lower level reflexes; brain pathology&raquo_space; persistent of primitive reflexes
– Motor program theory = Generalized motor programs for movement patterns
– Based on evidence (still used today):
– Still move without sensory input
– Similar patterns among individuals
– Several variations of patterns
– Complex movement from single stimulus
&raquo_space; Clinical utility: Innate and learned programs do exist
– Focus on self-initiated movements, synergies, task and action (not discrete movements)
– Modify old programs for new skill (train new effectors or retrain old effectors)
– Systems theory = internal and external forces on body predict movement
&raquo_space; Clinical utility: Physical properties of body predict movement kinematics
– Dynamical action theory = All movement is self-organized (no influence of CNS)
– Movements arise from demands of task and environment (physical principles, not neural)
&raquo_space; Clinical utility: Manipulate environment to allow movements to self-organize
– Ecological theory (“Perception action”) = Perception of environment drives movement
– Emphasizes exploration and adaptability more than consistency in behavior
&raquo_space; Clinical utility: Perception of environment can influence movement kinematics
– Ability may be impaired due to fear despite innate ability

DPT (8 decks)

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