Voluntary Movement

Question 1

Describe Voluntary Movement and the impact of the Motor Cortex

Answer 1

• Organized around a purposeful task in the motor cortex
• Can be varied and improved with practice/motor learning
• Can be generated internally or by external sensory information

Question 2

Describe the difference between voluntary movement and a reflex

Answer 2

When external sensory information or stimulus is received…

A reflex will always be elicited if the threshold is met

Voluntary movement can “decide” whether or not to respond to the stimuli and what to do in the response

Question 3

List 3 other names for the Primary Motor Cortex

Answer 3

1. M1
2. Broadmann’s Area 4
3. Precentral gyrus

Question 4

Area: Planning speech production

Answer 4

Broca’s Area (BA 44, 45)

Question 5

2 Pre-Motor Areas (PMA)

Answer 5

1. Premotor Cortex (PMC)
2. Supplementary Motor Area (SMA)

Together are BA 6

Question 6

Describe the 6 Layers of Cellular Organization of the Motor Cortex

Answer 6

Layers 1 & 2 = input from MOTOR and some from SENSORY cortex

Layers 3 & 4 = Input from the THALAMUS

Layer 5 = MAJOR OUTPUT (corticospinal neurons)

Layer 6 = local output

Question 7

Describe the effect of stimulation in the motor cortex vs. the c-spine

Answer 7

Stimulation occuring in the c-spine will result in mm contraction sooner than stimulation occuring in the cortex b/c the pathway is shorter in the c-spine

Question 8

Describe what has been understood from mapping grids of M1

Answer 8

1. A given muscle may have multiple areas of the cortex that when stimulated will produce varying amount of contraction
2. Overlap exists in the cortex (i.e. two muscles could be stimulated by one area)

Question 9

Describe the connections of the corticospinal axons and its effect on function

Answer 9

The corticospinal axons DIVERGE to motor neurons innervating more than 1 mm

Function: produces and controls simple joint movements as opposed to individual mm movement

Question 10

Describe the effect of redundacy in the mm representation

Answer 10

Allows different combinations of mm acitivity for different tasks

Also allows compensation after injury due to mutliple tracts with similar functions

Question 11

Describe the Inputs to the Motor Areas

Answer 11

They are reciprocal

• S1, S2
• Frontol Cortex
• Premotor
• SMA
• Cingulate motor area
• Thalamus, Basal ganglia, Cerebellum

Question 12

Describe the function of the (pre)frontal cortex in regards to voluntary movement

Answer 12

It reminds you why you’re doing what you’re doing

Question 13

Cortex Properties:

• Primary simple movements of hand and face

Answer 13

M1

Question 14

Cortex Properties:

• Highly plastic somatotopic organization
• Allows for motor learning and recovery following injury

Answer 14

M1

Question 15

Cortex Properties:

• Direct relationship between cell firing rate and force

Answer 15

M1

Can modulate the amount of force needed for a given task

Question 16

Cortex Properties:

• Direction of movement is encoded by neurons (creates a population vector)

Answer 16

M1

Controls the direction of movement needed for a given activity

Question 17

Describe the properties of M1

Answer 17

1. Controls voluntary movement - primarily simple movements of the hand and face
2. Has highly plastic somatotopic organization
3. A direction relationship modulates the amount of force needed
4. Controls the direction of activity for a given task

Question 18

Area: Critical for planning movement and preparatory activity

Answer 18

PMA – PMC & SMA

Question 19

Describe the location of the corticospinal tracts in the cortex

Answer 19

The majority are located in M1

Some are located in the PMA but required stronger stimulation to result in movement

Question 20

Area: Stimulation evokes more complex movements involving mutiple joint and resembling coordinated movements

Answer 20

PMA

Question 21

Area: Projects to M1 and directly to SC

Answer 21

PMA

Question 22

Describe the difference in deficts to M1 and PMA

Answer 22

Deficits to the PMA cause more complex deficits than damage to M1 alone

Question 23

Cortex Properties: Projects largely to proximal mm, fires during the delay between cue and action

Answer 23

PMCd (dorsal)

Question 24

Cortex Properties: Externally driven movements

Answer 24

PMCd

Question 25

Describe the Properties of PMCd

Answer 25

• Externally driven
• Fires during delay between cue and action
• Projects largely to proximal mm

Question 26

Cortex Properties: Projects to hand/digits to control hand shape

Answer 26

PMCv (ventral)

Question 27

Cortex Properties: Active whether the subject watches or performs the task

Answer 27

PMCv

Question 28

Cortex Properties: Fires only during planning of specific hand movements

Answer 28

PMCv

Question 29

Describe the Properties of PMCv

Answer 29

• Fire only during planning of hand movement
• Active whether performing or demonstrating
• Projects to hand/digits

Question 30

Area: Projects to M1 and SC (largely to mm of hand and digit)

Answer 30

SMA

Question 31

Cortex Properties: Heavily involved with planning sequential movements

Answer 31

SMA

Question 32

Cortex Properties: Internally driven movements

Answer 32

SMA

Question 33

Cortex Properties: Mental rehearsal of movements

Answer 33

SMA

Question 34

Cortex Properties: Stimulation evokes bilateral movements – coordinates movement

Answer 34

SMA

Question 35

Describe the Properties of SMA

Answer 35

• Sequential movements
• Mental Rehearsal
• Internally Driven
• Coordination due to bilateral projection

Question 36

Describe synergy

Answer 36

A highly stereotyped and obligatory movement

With lesions movements that were once controlled individually are now lumpted together and performed as one movement due to synery

Inhibition fractionated movement due to damage to corticospinal tract