Motor Control in Mammals I

Question 1

What are the 3 distinct categories of movement?

Answer 1

1. Reflexive - stereotyped responses to specific stimuli
2. Rhythmic - timing and spatial organisation largely controlled autonomously by spinal cord/ brain stem
3. Voluntary - conscious control by brain

Question 2

What is the type of nerve fibre that co-ordinates motor activity?

Answer 2

Efferent

Question 3

What is the motor control hierarchy and how does it go?

Answer 3

It’s an analysis of the motor system
High: strategy goal of movement - neocortex, basal ganglia and cerebellum
Middle: Tactics - which muscle contraction required to achieve strategic goal - motor cortex, cerebellum
Low: execution - brainstem, spinal cord, activation of MN and interneurons

Question 4

What does the neocortex do?

Answer 4

Provides information on the body position in egocentric space: vision, audition, somatic sensation, proprioception, perception or awareness of body position

Question 5

Where does the brainstem provide input to prevent falling?

Answer 5

Thoracic and lumbar spinal cord

Question 6

What are ballistic movements?

Answer 6

Can’t be altered once initiated (no sensory feedback)

Question 7

What type of sensory information goes into each hierarchy of motor control? (3 marks)

Answer 7

High - mental image of body in egocentric
Middle - memory and sensory information from past movements
Low - maintenance of posture and muscle length and tension before and after voluntary movements

Question 8

What is sensorimotor transformation and what is it dependent on? (3 marks)

Answer 8

• Sensory stimuli converted into motor commands
  Dependent on 2 things:
  1. Extrinsic information about the world around us
  2. Intrinsic information about our body - kinematic and kinetic information

Question 9

How do sensorimotor information generate movement to a desired location? (4 marks)

Answer 9

1. Target localised in egocentric space
2. Planning of movement (path and trajectory) and initial location of endpoint and endpoint trajectory
3. Innerve kinematic transformation. Joint trajectories to achieve hand path are determined
4. Inverse dynamic transformation, joint torques or muscle activities to achieve joint trajectory are determined

Question 10

How do fixed length limbs help with the mathematical relationship between joints and limbs?

Answer 10

Allows the CNS to estimate the hand position if joint angles and segment lengths are known

Question 11

What is the difference between kinetic information and kinematic information?

Answer 11

Kinetic information is focused on the cause of motion in different objects and different types of movement. Whereas kinematics is more focused on the acceleration, velocity of a movement

Question 12

What are internal models?

Answer 12

Neural circuits that compute sensorimotor transformations

Question 13

What is the forward model? (what does it represent)

Answer 13

An internal model that represents relationships between actions and their consequences

Question 14

What does the forward model (a). estimate (b). anticipate?

Answer 14

a. Future sensory inputs based on motor outputs
b. How motor command is acting on sensorimotor system and is passed into forward model that acts as neural stimulator. Copy of the motor command is known as efference copy

Question 15

What is the inverse model?

Answer 15

It calculates motor outputs from sensory outputs (desired behaviour)

Question 16

What does the speed accuracy trade off show?

Answer 16

That we have a limited ability to move both quickly and accurately. Shows that the variability in movement increases proportionally with speed

Question 17

What is feed forward control? (2 marks)

Answer 17

Controller generates motor command based on desired state. Movement is not monitored for errors so there is no sensory feedback