Central Contributions To Motor Control (1+2)

Question 1

What two basic things do we do when making an action?

Answer 1

• plan a goal or intention

- guide the action to achieve the goal

Question 2

What is closed loop control?

Answer 2

The use of sensory information during action allows for movement guidance or correction - this type of movement is called closed loop control

Question 3

How is an action goal achieved?

Answer 3

Achieved by modifying behaviour with use of incoming sensory information

Question 4

The output cycle refers to what??

Answer 4

The sensory inputs (vision, proprioception, auditory etc.)

Question 5

What did Woodworth (1899) consider?

Answer 5

That an action plan would first execute, and once underway, would be guided by the senses to achieve the goal.
Also considered that feedback for correction would be dependent on capacity and time.

Question 6

What did Woodworth (1899) test and what did he find?

Answer 6

Tested the effects of making actions with and without visual guidance, and measured performance error.

The results showed that 200-400ms of vision reduced error, and 400-1000ms of vision showed stable performance

Question 7

What did Keele and Posner (1968) find to back up the data of Woodworth (1899)?

Answer 7

Showed there was no difference between vision conditions with 200ms, hence more than 250ms of vision was required to increase the chances of hitting the target

Question 8

What are some problems with closed-loop control?

Answer 8

We can execute some movements without sensory feedback

The sensory feedback loop may be too long to control fast movements

Question 9

What is the sequence of events in the sensory feedback loop?

Answer 9

Goal - reference mechanism - executive/effectors - environment

Question 10

How did Schmidt (1988) define a motor program?

Answer 10

“A motor program as a prestructured set of central commands capable of carrying out movement essentially open-loop”

The motor programme is an open-loop process, meaning no need for sensory feedback

Question 11

Describe the sequence of events in a motor program (open loop)

Answer 11

Input Instructions Output

-> executive -> effector

Question 12

What does reference refer to??

Answer 12

A feedforward or efferent copy mechanism , which is a copy of the motor programme

Question 13

What is ‘efferent copy’ used for?

Answer 13

To compare the state of ongoing action through the senses with that originally intended.
In addition it appears to prepare the sensory feedback systems

Question 14

What are the 2 main problems of the theoretical model of open and closed loop motor control??

Answer 14

The storage problem : questions whether there are set programs that we learn and execute for every type of response

The novelty problem : this questions how we adapt the set programs to make new responses

Question 15

What is a generalised motor program?

Answer 15

An abstract memory structure that governs a class of movement pocessing a common movement pattern

Question 16

What does the GMP consist of?

Answer 16

Certain characteristics of an action that are invariant, such as the order of events, relative time and relative force.

For a particular class of action, a motor program is stored in memory, a unique pattern of activity will result if the program is executed.

At the time a specific action must be produced, the abstract program must be parametrised to accommodate the demands of the specific situation

Question 17

What are the main invariants of a GMP?

Answer 17

Relative duration, relative force and order of events

Question 18

What are the two main parameters are?

Answer 18

Overall duration and overall force

Question 19

What did Schmidt propose that a motor response consists of?

Answer 19

Fixed and modifiable patterns.
Similarly there is an overall force parameter that controls the relative action forces contained in the movement sequence. Increasing the force of the muscles over the same time makes bigger movements

Question 20

What are the 2 types of movement error ?

Answer 20

• Programme selection (incorrect action selection)

- Programme execution (incorrect execution)

Question 21

What are some examples of errors in programme selection?

Answer 21

Typically involve catching a ball instead of heading it, moving right instead of left.

To correct selection errors, a completely new plan must be generated, therefore these errors cannot be corrected online

Question 22

Timing of movement correction depends upon the nature of the error. How do selection and execution errors differ ?

Answer 22

Selection errors require a new plan and so can take as long as 120-200ms to correct
Execution errors can modify the ongoing plan with 30-50ms of detecting the error

Question 23

What is the sequence of events in the open-loop control system?

Answer 23

Movement commands

Movement control centre -> Movement effectors

Question 24

What is the sequence of events in the closed loop control system?

Answer 24

Movement commands

Movement control centre ->. Movement effectors

Question 25

Referring to diagram of the motor programme, what does plan, feedforward correction and guidance include?

Answer 25

Plan includes executive, stimulus identification and response selection

FF correction includes reference

Guidance involves muscles, movement, changes in environment and feedback

Question 26

What is an internal model (Kawato, 1999)

Answer 26

Internal models are neural mechanisms that can mimic the input/output characteristics , or their inverses, of the motor apparatus.

Question 27

What are the two types of internal models?

Answer 27

Internal forward models

Internal inverse models

Question 28

What do internal forward models do?

Answer 28

Capture the forward or causal relationship between the inputs to the system and the outputs (Kawato et al,1997)

‘Forward internal models can predict sensory consequences from efference copies of issued motor commands’ (Kawato, 1999)

Provides predicted sensory feedback / states of movements
Motor -> sensory information
Forward models act as the predictors (Miall et at, 1993)

Question 29

What’s the basic premise of inverse dynamic models?

Answer 29

Inverts the forward models

A motor command that will cause a desired change in state

Sensory to motor information

Inverse models act as the controllers (Miall et all, 1993) amd as the motor command

Question 30

What did Kawato (1999) state about inverse internal models?

Answer 30

” inverse internal models can calculate necessary feedforward motor commands from desired trajectory information “

Question 31

Describe the sequence of events in an inverse dynamic model?

Answer 31

Desired trajectory Feedforward motor command Realised trajectory
->. Inverse model. ->. Controlled object. ->.

Question 32

The cerebellar cortex is highly regular and densely packed, what are the effects of cerebellar damage??

Answer 32

• coordination of movements
• some effects on posture/muscle tone
• no effect on muscle strength, sensory perception or higher order processes

Question 33

How does the cerebellum affect motor coordination?

Answer 33

Corrects ongoing movements when they deviate from the intended course and modifies descending output and central motor programs

Cerebellum could be inverse model?