HIGHER CORTICAL LEVELS INVOLVED IN MOTOR CONTROL

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HIGHER CORTICAL LEVELS INVOLVED IN MOTOR CONTROL

• RETICULAR FORMATION
• CEREBELLUM
• BASAL GANGLIA
• MOTOR CORTEX

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CEREBELLUM

• Common Belief Response to FB from
  proprioceptors after movement has begun
• Changes have also been shown to occur in advance
  of movement initiation - Control of rapid
  movements
• Damage Disequilibrium, tremor (severe during
  rapid movements), disturbances in timing and
  coordination (movts slow to start, inaccurate
  direction, wild, jerky movements)

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BASAL GANGLIA

• Generation of slow movements
• Damage difficulty in starting slow movements,
  tremor and hesitancy when approaching obstacles
  or changes, extreme tremor during slow movements

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MOTOR CORTEX

• Closely aligned to sensory cortex and sometimes
  referred to as sensorimotor area)
• Formulates overall plan of action and initiates
  the motor commands
• Involved with both slow and fast movements
• Damage
• Causes paralysis

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PreMotor Cortex

• Concerned with refinement and integration of
  complex motor actions
• Voluntary movements require temporal organization
  (sequential linking) - responsibility belongs to
  this portion of motor cortex
• Damage disintegration of many skilled
  movements lose ability to make transition among
  the links involved in skilled movements

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CLOSED LOOP/ OPEN LOOP MOTOR CONTROL SYSTEMS
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FOUR DISTINCT PARTS TO CLOSED LOOP SYSTEM

• AN EXECUTIVE FOR DECISION MAKING ABOUT ERRORS
• AN EFFECTOR FOR CARRYING OUT DECISIONS
• A REFERENCE OF CORRECTNESS/GOAL
• AN ERROR SIGNAL

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CLOSED LOOP SYSTEM

• 1. System goal is defined
• 2. Sensory information is compared to actual
  information about movement
• 3. Executive is informed about an error
• 4. Executive sends command to the effector
• 5. Match is made, error is zero
• 6. Executive sends command to turn off heater

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REFLEX BASED RESPONSES

• M1 gt
• Monosynaptic stretch reflex
• Muscle spindle level
• Small EMG burst
• 30-50 ms
• M2gt
• Functional stretch reflex, long loop reflex
• Contributes to movement modulation
• 50-80 ms
• TRIGGERED REACTION
• Learned
• 80-120 ms latencies
• Wineglass effect
• M3gt Voluntary - 1 RT
• 120-180 ms latency

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CONTROL OF LONG-DURATION SKILLS

• MAINTENANCE OF POSTURE
• VISUAL TRACKING
• MAINTENANCE OF RUNNING SPEED
• IF CORRECTIONS FASTER THAN 200 MS, HOW DO THEY
  OCCUR?

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Error
Conceptual Model
Muscle length, force
Joint position, body position
Vision, audition
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Error
Conceptual Model
M2
M1
Muscle length, force
Joint position, body position
Vision, audition
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OCULOMOTOR SYSTEM

• CRANIAL NERVES
• EXTRAOCULAR MUSCLES

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VISUAL ACUITY (VA)

• STATIC VA
• Schnellen Chart
• DYNAMIC VA
• Rotational Disc
• Improves with practice

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TYPES OF EYE MOVEMENTS

• SACCADIC
• Ballistic
• Voluntary
• SMOOTH PURSUIT
• Tracking
• Not voluntary

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FIELD OF VISION

• CENTER
• (FOVEAL)
• SHARPEST
• CONES ARE DENSEST
• PERIPHERAL
• CONE DENSITY DIMINISHES
• RECEPTORS SENSITIVE TO MOVEMENT
• HORIZONTAL PV - ABOUT 170 DEG FOR BOTH EYES
• VERTICAL PV
• ABOUT 45-47 DEG ABOVE
• ABOUT 65-70 DEG BELOW

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TWO VISUAL SYSTEMS

• FOCAL SYSTEM
• Specialized for object identification
• AMBIENT SYSTEM
• Specialized for movement control
• Involves entire visual field
• Operates non-consciously
• Functions to detect motion and position of
  objects--and ones relation to them

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AMBIENT VISION AND MOVEMENT CONTROL

• OPTICAL FLOW
• A FLOW OF LIGHT ACROSS THE RETINA.
• CHANGES WHEN EYE CHANGES POSITION.

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INFORMATION FOR MOVEMENT PROVIDED BY OPTICAL FLOW

• STABILITY AND BALANCE
• VELOCITY OF MOVEMENT THROUGH THE ENVIRONMENT
• DIRECTION OF MOVEMENT RELATIVE TO ENVIRONMENT
• MOVEMENT OF OBJECTS IN ENVIRONMENT RELATIVE TO
  OWN MOVEMENT
• TIME BEFORE CONTACT BETWEEN PERFORMER AND OBJECT
  (TAU)