Section 1 - Sensorimotor Control Introduction

Question 1

How is motor behaviour controlled?

Answer 1

Motor behaviour is a combination of feedforward and feedback control. A continuum from one to the other.

Question 2

Define Feedforward control & give an example

Answer 2

Uses control information PRIOR to the execution of movement rather than during the movement

Is rapid

ex) Movement to swat a mosquito - may be too fast for you to make corrections based on where you see or feel your arm.

Question 3

Define Feedback control & give an example

Answer 3

uses sensory information DURING the execution of movement

Allows for error detection and thus movement correction

This type of control is often slower

ex) correcting the trajectory of your arm/hand based on visual feedback to catch a ball that is curving away from you because of the wind

Question 4

What are the 4 sensorimotor control problems that the nervous system must deal with

Answer 4

• Degrees of freedom (DOF) problem
• Serial-order problem
• Sensorimotor integration problem
• Motor learning problem

Question 5

Define Degrees-of-freedom (DOF) problem

Answer 5

The DOF problem relates to the fact that the nervous system must control (and coordinate) many neurons, muscles, and joints to perform a particular motor behaviour

Question 6

Define DOF & what they are controlled by

Answer 6

DOF refers to all the independent variables in a system

DOF are controlled by groups of neutrons that can fire in different patterns

Question 7

Give 1 advantage & 1 disadvantage of DOF

Answer 7

Having so many DOF makes control complex, but it is also an advantage, as it provides greater flexibility.

ex) you can perform the same action in different ways. This might be important if you suffer an injury, or if you are an athlete.

Question 8

What are 4 solutions to the DOF problem that the nervous system can use & describe them

Answer 8

1) ensure efficiency : by avoiding extreme joint angles (thus reducing movement range of motion) and moving smoothly

2) use muscle synergies : A muscle synergy is a group of muscles activated by a common command (and thus working together) to perform a movement

3) Determine the task-relevant DOF : Thus, rather than reducing the number to control, the nervous system can coordinate only the DOF that are most relevant to the motor behaviour

4) can exploit the mechanics of the joints and muscles : (e.g., inertia, gravity).

Question 9

Give an example of muscle synergy (a solution to DOF problem of sensorimotor control problem)

Answer 9

“freeze out” a portion of the DOF ; which means introducing a temporary, rigid couplings between multiple DOF, which reduces the number of DOF to control

ex) Beginner ice skaters : Locking the knee joint means that the nervous system doesn’t have to worry about complex coordination of the knee with the rest of the leg joints.

Question 10

Give an example of exploiting the mechanics of the joins and muscles (a solution to DOF problem of sensorimotor control problem)

Answer 10

The nervous system might be able to activate the muscles less if inertia causes a limb to move (or continue moving). As for gravity, if you have an arm out to the side, why activate muscles to bring it back down when you can use gravity to assist (and thus use less muscle activity)

Question 11

Define Serial-Order problem

Answer 11

The nervous system must sequence a movement or series of movements

• Must activate the correct muscles in the correct order

Question 12

What are 2 solutions to the Serial-order problem that the nervous system can use & describe them

Answer 12

1) Form a motor plan

2) Co-Articulation : This entails simultaneous motions of different effectors (i.e., body parts; limb, trunk, head, eye) that help to achieve a task that unfolds over an extended period. This means that the activity of one muscle begins before the other ends to allow smooth movement at different joints.

Question 13

Define Sensorimotor integration/Perceptual-motor integration problem & explain why it is an issue & which question is important to ask

Answer 13

It relates to the fact that the nervous system needs to integrate sensory information (from a variety of sources) to form a perception, which it can then use to act on (i.e., execute a motor behaviour).

• sensory information is encoded by different receptors in different parts of the body and thus, in different coordinate systems
• which spatial co-ordinate system is used, body-centred verses world-centred

Question 14

Define & compare body-centered vs world-centered

Answer 14

Whether the signal is related to:

the body - as in the visual distance between a handle and your hand

-> This breaks down further within the body, eye/head/hand/arm/etc

the world - as in comparing between two areas outside of the body, like the visual distance between a handle and a nearby desk

Question 15

Define motor behaviour

Answer 15

Includes individual movements and motor skills

Question 16

Define Motor Learning problem

Answer 16

*To what extent are we born with a selection of motor skills and to what extent are motor skills learned?

*How do we acquire skills that we must learn?

*How do we adapt our movements to changes in the sensorimotor system?

*How is motor memory represented and maintained?

Question 17

Define motor skill

Answer 17

• A goal-directed task that requires voluntary head, body, and/or limb movement
• made up of a series of movements

ex) Shooting a basketball into a hoop

Question 18

Define Movement

Answer 18

• Is a component of a motor skill and is defined by the behavioural characteristics of the limb or a combination of limbs
  ex) extending at the elbow when shooting a basketball