Lecture 7a: Closed-Loop Motor Control

Question 1

Closed-Loop Control

Answer 1

the control of movement has been conceptualized as closed-loop or open-loop
closed-loop control:
online/moment-to-moment control of movement - involving constant processing of feedback
- feedback, error detection and error correction used to achieve a desired goal (process of detecting and correcting)
- this type of system is very useful when the body needs to control itself for longer periods of time (longer actions are more dependant on sensory information)

Question 2

Four Key Closed-Loop Components

Answer 2

1. executive
2. effector
3. comparator
4. error signal
   all closed-loop control systems have these 4 components!

Question 3

Closed-Loop Component: Executive (1)

Answer 3

determines the actions to be taken to achieve the desired goal state (decision making)
A. in some closed loop tasks it
is just to be balanced
3 stages of information processing

Question 4

Closed-Loop Component: Effector (2)

Answer 4

carries out the decision/desired action
- muscles (receive motor commands via the spinal cord to initiate movement)

Question 5

Closed-Loop Component: Comparator (3)

Answer 5

compares feedback of desired goal state to feedback of actual state (the error detection mechanism/reference of correctness)
A. is what we are doing
different to what we wanted
to be doing (error detection)
- compares intended/expected movement with actual movement (feedback)

Question 6

Closed-Loop Component: Error Signal (4)

Answer 6

information acted on by the executive
A. if there is discrepancy in
sensory information, you
can update the ongoing
movement

Question 7

Closed-Loop Control: continuous processing of feedback for action success

Answer 7

• you might to make some corrections or carry on if you are at your desired state
• error correction is the executive system
• feedback of what is actually happening (feedback/sensory information)
• when something we expect do are violated then the system wants to act to correct it

Question 8

Open-Loop Control

Answer 8

movement is pre-programmed fully in advance and does not rely on feedback
◦ less or not dependant on
feedback in a way that is
programmed
- feedback, error detection and error correction are NOT needed to achieve a desired goal
- this type of system is very useful in predictable environments when the movement is short
-> there is no loop in open loop system (not continually monitoring in order to make quick movement
in predictable environment)

Question 9

moving a cursor, walking a beam and retrieve a fumbled football: what are these examples of?

Answer 9

closed-loop control
- continuous
- fine/precision
- open

Question 10

key press, jab in boxing and kick a punch bag: what are these examples of?

Answer 10

open-loop control
- discrete
- gross
- closed/predictable

Question 11

3 main factors which affect whether CNS will act in an open vs. closed-loop fashion

Answer 11

1. time: how long will the action take?
2. precision: how much tolerance is there for error? (information will be more important if you need accuracy)
3. predictability: how constant/familiar is the environment? (less need to monitor with predictable stable environment)

Question 12

(1) Time: How long will the action take to be completed?

Answer 12

• closed-loop, longer, more continuous
  ◦ swimming - processing
  information
• open-loop, shorter, ballistic (not dependant on information), discrete
  ◦ jab in boxing

Question 13

(2) Precision: How much tolerance is there for error?

Answer 13

• closed-loop, fine/precise
  ◦ accuracy is information in
  gymnastics
• open-loop, gross, less precise
  ◦ shotput - that include power
  and strength is a little less
  about precision

Question 14

(3) Predictability: How constant is the environment and how often has it been done before?

Answer 14

• closed-loop: open skills, new skills (low in predictability)
  ◦ basketball skills in open
  environments
• open-loop: closed skills, well practiced (predictable)
  ◦ penalty shot in soccer (could
  be relatively programmed
  and not include much
  monitoring)

Question 15

All stages of information processing represent the EXECUTIVE component of closed-loop control

Answer 15

• stimulus identification, response selection and response programming
• have to continually re-identify, re-select and re–program which is time consuming

Question 16

2 primary sources of response-produced sensory (intrinsic) feedback

Answer 16

1. exteroception (external environment): information about movement (you or objects) in environment primarily vision, audition (hearing), olfaction (smell)
2. proprioception (within the body): information about our own movements
   - example: length of muscles (muscle spindles), forces produced by muscles (golgi tendon organs/GTOs), orientation of head in space (vestibular apparatus)

both are intrinsic