Motor Control Part 1 Theories of Motor Control

Question 1

What is the Reflex Theory?

Answer 1

A theory of motor control saying that complex behavior could be explained through the combined action of individual reflexes that were “chained” together (stimulus → reflex → stimulus → reflex, etc.)

Question 2

What are some limitations of the Reflex Theory? (5)

Answer 2

• If both spontaneous and voluntary movements are recognized as behavior then reflex alone cannot be the basic unit of behavior
• Does not explain movements that happen too quickly to allow for sensory feedback from preceding movement to trigger the next
• Does not explain movement that occurs without sensory stimulus (voluntary movement can occur by thought alone)
• Does not explain how a single stimulus can result in varying responses depending on the context and descending commands (many ways to accomplish same goal)
• Does not account for “novel” experiences

Question 3

What is the Hierarchical Theory?

Answer 3

The brain has higher, middle, and lower levels of control
• Higher = association areas of cortex
• Middle = motor cortex
• Lower = spinal levels of motor function

Question 4

True or False: There is never bottom up control

Answer 4

True

Question 5

True or False: In the hierarchical theory, reflexes are not the sole determinant of motor control, but can be part of it.

Answer 5

True

Question 6

Motor Programming Theories are moving away from what in terms of the CNS?

Answer 6

Moving away from CNS as only a reactive system to it being also an active system.

Question 7

When we stand upright, activity _________ in ________ postural muscles to counteract the force of gravity.

Answer 7

Increases; antigravity

This definition is: Postural Tone

Question 8

What type of input is critical for postural tone? (2)

Answer 8

Sensory –> somatosensory and vestibular especially.

Question 9

Quiet stance is characterized by what 4 things?

Answer 9

1. Body alignment/sway
2. Postural tone
3. Mm tone
4. Passive skeletal alignment

Question 10

Depending on the frequency of sway movement, what two strategies might one use to keep upright?

Answer 10

Ankle or hip strategies

Question 11

Perturbation is defined as:

Answer 11

A cause of disturbance or upset.

A secondary influence on a system that modifies behavior.

Question 12

Which movement strategy is most common; A/P or M/L?

Answer 12

A/P

Question 13

Which part of the CNS selects the specific movement patterns used to recover stability following displacement of the COM?

Answer 13

The higher level cortex.

Question 14

True or False: Muscles cannot belong to more than one synergy.

Answer 14

False.

Question 15

What is the ankle strategy?

Answer 15

A postural strategy that keeps the body upright. First the gastrocnemius is activated to keep the body from falling fwd, then the hamstrings, then the paraspinal mm.

Question 16

What is the hip strategy?

Answer 16

A postural strategy that keeps the body upright. It comes in after the ankle strategy. It is a large, rapid motion at the hips and comes in response to larger and faster perturbations.

Question 17

When do we use a stepping strategy?

Answer 17

When ankle or hip strategies are not enough.

Question 18

What senses contribute to postural control? (3)

Answer 18

Vestibular
Visual
Somatosensory

Question 19

What do each of the three senses contribute in respect to postural control?

Answer 19

Vestibular: Position of head in respect to gravity and inertial forces.
Visual: Position of head in respect to vertical.
Somatosensory: Position of body and its segments in respect to its supporting surfaces as well as each body segment with another.

Question 20

Quiet stance is characterized by:

Answer 20

small amounts of spontaneous postural sway

Question 21

What sensory strategies are used in quiet stance? (2)

Answer 21

Visual
Somatosensory
(we don’t use vestibular b/c we’re not moving)

Question 22

What sensory strategies are used in perturbed stance? (2)

Answer 22

Somatosensory

Vestibular

Question 23

The Intermodal Theory of Sensory Organization states:

Answer 23

All 3 senses contribute equally to postural orientation at all times.

Question 24

The Sensory Weighting Hypothesis states:

Answer 24

The postural control system is able to reweight sensory inputs in order to optimize stance in altered sensory environments.

Predicts that each sense provides a unique contribution to postural control.

The CNS has to resolve sensory conflicts by changing the relative weight of a sensory input to postural control.

Question 25

During postural control, what do attentional requirements depend on? (3)

Answer 25

1. Task
2. The age of the individual
3. The individual’s balance abilities.

Question 26

What is the Motor Programming Theory?

Answer 26

Exploring the physiology of actions, rather than the physiology of reactions. Moving away from CNS as only a reactive system to it being also an active system. (You don’t have to have a reflex to have a movement).

Question 27

What are some limitations to the Motor Programming Theory?

Answer 27

• The central motor program cannot be considered to be the sole determinant of action
• Does not take into account the nervous systems interactions with the musculoskeletal and environmental variables in achieving a movement

Question 28

What is the Systems Theory?

Answer 28

Need to understand the characteristics of the system you are moving in, and the internal and external forces acting on the body, to understand neural control

Question 29

The Systems Theory says synergies show both stability against ______, and flexibility to solve _________.

Answer 29

Perturbations; concurrent tasks.

Question 30

What is the Dynamic Systems Theory?

Answer 30

Human movement system is a highly intricate network of co-dependent subsystems that are composed of a large number of interacting components

Question 31

What are some limitations to the Dynamic Systems Theory?

Answer 31

May minimize the role of the nervous system too much

Question 32

What are some limitations to the Hierarchal Theory?

Answer 32

• Cannot explain the dominance of reflex behavior in certain situations in normal adults (i.e. Crossed extension & Withdrawal reflexes)
• Need to be cautious about assuming that all low-level behaviors are primitive, immature, and that all higher level behaviors (cortical) are mature

Question 33

What is the Ecological Theory?

Answer 33

o The way in which our motor systems allow us to interact most effectively with the environment in order to perform goal-oriented behavior
o The organization of action is specific to the task and the environment in which the task is being performed

Question 34

What are some limitations to the Ecological Theory?

Answer 34

• Gives less emphasis to the organization and function of the nervous system
• Research has shifted from the nervous system to the organism/environment interface