Cortical Control of Movement

Question 1

Three tasks for proper motor control

Answer 1

• Produce accurately timed commands to many muscle groups
• Take into account current position of body and distribution of body mass
• Take into account and compensate for the physical characteristics of the body and the muscles

Question 2

Short distance interneurons

Answer 2

• Lateral intermediate gray

- Distal limbs

Question 3

Long distance interneurons

Answer 3

• Medial intermediate gray

- Proximal limbs

Question 4

Direct and indirect terminations on ventral horn motoneurons

Answer 4

• More direct terminations means greater dexterity
• Intrinsic fine motor control develops later than extrinsic hand control
• Correlation: babinski’s

Question 5

Vestibulospinal tracts

Answer 5

• Changes gain of axial and proximal limb reflexes

- Facilitates anti-gravity muscles

Question 6

Reticulospinal tract

Answer 6

• Changes gain of axial and proximal limb reflexes

- Central pattern generator

Question 7

Colliculospinal tract

Answer 7

-Axial and midline body orientation

Question 8

Rubrospinal tract

Answer 8

-Some distal control, mainly arm flexion

Question 9

Cell dominating motor areas

Answer 9

• Large pyramidal cells

- Betz cells

Question 10

Main cortical motor areas

Answer 10

• Primary motor cortex (M1)
• Premotor cortex: Lateral (Dorsal premotor area PMd, and ventral premotor area PMv) and Medial (supplementary motor cortex SMA, and cingulate motor areas (CMA))
• Frontal eye field (FEF)
• Supplementary eye field (SEF)

Question 11

Definition of a cortical motor area

Answer 11

• Projects to motor neurons in the spinal cord
• Projects to the primary motor cortex
• Contains Betz cells or equivalent large layer V projection neurons
• Can be stimulated at low thresholds to produce movements of discrete muscles or muscle groups
• Displays changes in activity related to parameters of movement

Question 12

What accounts for recovery of dexterity?

Answer 12

• Likely due to signaling by spared interneurons to bypass the lesion
• Branch connections above and below the site of injury

Question 13

Cortical control of movement key features

Answer 13

• Individual muscles are represented in multiple locations

- Individual corticospinal neurons diverge to influence multiple motor neuron pools and hence multiple muscles

Question 14

What do cortical motor cells actually code for?

Answer 14

• Direction: flex or extend in a certain way by individual neurons altering discharge rates
• Muscle activity: agonists and antagonists, alpha and gamma motoneurons
• Force: recruit additional motor units if needed

Question 15

Specialization of M1

Answer 15

-Execution of simple movements

Question 16

Specialization of lateral premotor area (PMd, PMv)

Answer 16

-Selection of motor responses based on externally-cued (sensory) inputs

Question 17

Specialization of medial premotor area (SMA, CMA)

Answer 17

• Executing learned sequences

- Internally cued movements

Question 18

Specialization of Pre-SMA

Answer 18

-Learning of sequences

Question 19

Specialization of prefrontal area

Answer 19

• Decision for action and working memory

- Monitoring outcomes