Lecture 9a, Open-Loop Control & Motor Programs

Question 1

Motor Program

Answer 1

a pre-structured set of neural commands, organized in advance, and capable of producing movement without influence of feedback
- movement carried out open-loop until enough time passed to allow closed-loop (feedback) processes to operate (assuming they can operate)
- representations of movements stored in memory (we are storing memory that allows us to enact movements that we done before and new movements)
- sometimes, once these commands are sent, they cannot be stopped (since they are not influenced by feedback)

Question 2

What are 3 mechanical examples of operating under open-loop control?

Answer 2

sprinkler: comes on particular time of day no matter the weather

traffic light: not dependent on traffic flow - turn to different colours at specific times as they are pre-planned and uninfluenced by what is actually going on in the environment

toaster: operate on timer

Question 3

Motor Programs & Open-Loop Control

Answer 3

advance instructions are generated (identification of operations, sequencing and timing) -> program is initiated ->x no mechanism and correction of error <until></until>

Question 4

Open-Loop Control: Feedback is not needed to guide/control movement (what are the stages?)

Answer 4

1. executive: 3 stages of information processing
2. effector: muscles (receive motor commands via the spinal cord to initiate movement)
   - the motor program is prepared in the executive and drawn from LTM. motor program is what is sent to effectors, essentially connects the executive & effector systems
   - motor programming has been placed in between stages of information processing and actual movement
   - capsulates the motor commands and being sent down spinal cord to muscles

Question 5

What is the evidence for such “motor programs”? (5)

Answer 5

empirical (research) evidence for motor programs
1. RT and movement complexity
2. inhibiting anticipatory actions
3. triphasic EMG pattern and movement blocking
4. RT and Startle effects
5. deafferentation studies: Ian Waterman & deafferentation work sometimes involve actual experimental studies, or just clinical /case-study observation

Question 6

Movement Complexity: what event should have the slowest RTs? 100m sprint or 100m hurdles?

Answer 6

• additional planning component to run and jump as compared to just run
• the hurdles take longer is an assumption we would make

Question 7

Inhibiting anticipatory actions

Answer 7

in baseball batting, there’s evidence that motor programs, once sent, cannot be inhibited
- step & swing seem to be coupled unit (motor program)
- hard to stop a swing once it is underway even though you are getting information to not swing, the action seems to have to run of once you have made a decision
- stopping a preplanned response requires sufficient time before response initiation

Question 8

When is the ‘Point of No Return’ (PONR)?

Answer 8

the ‘Point of No Return’ (PONR) is when the motor program is released
- during the anticipatory period, you have selected a motor program and you are waiting to initiate it
- after the PONR, your body executes the motor program in open-loop manner
- it is possible to stop or alter a motor program, but that requires slow, closed-loop control
- this point when you have released the motor program

Question 9

Blocked movements & the Triphasic pattern of Muscle Activation (agonist & antagonist)

Answer 9

if you stop a movement and we measure EMG, typically this triphasic burst of activity the agonist comes on to get the movement underway and antagonist come on to break the movement and the agonist burst is there again

Question 10

Why do we get this triphasic EMG pattern? Is it programmed or functions based on feedback?

Answer 10

1) agonist 1 (AG1)
* main impulse for the movement
* precedes movement onset (takes time to overcome inertia)
2) antagonist (ANT)
* represents “braking” (decelerate limb)
3) agonist 2 (AG2)
* helps to clamp limb at target
* co-contraction

• since it is part of motor program or it is based on feedback and we realize we have to slow the movement and turn on antagonist to break it to reach target
• if we stop the movement from completing we should not this triphasic activity, there is no reason for an antagonist burst to break or decelerate the limb if there is not movement but it could be that we expect to this triphasic activity if it is part of the motor program at least until particular point in time until feedback can kick in

Question 11

Still exhibited triphasic pattern - even when blocked!

Answer 11

• the triphasic pattern is still there even if the movement is blocked
• when the movement is blocked this first agonist burst looks almost the same
• the antagonist burst still comes on and looks the same until we get till 100 ms

Question 12

What caused the Antagonist muscle burst to “turn on” even though the movements were blocked?

Answer 12

the motor program - pre-planned set of muscle commands that seem to show up even though there was no need for it