Cortical motor areas

Question 1

Where is the motor cortex located?

Answer 1

Immediately rostral to central sulcus

Question 2

What is the role of the primary motor cortex?

Answer 2

Area critical for execution of voluntary movements

Control of precise, independent movement of the extremities

Question 3

What is the motor association cortex?

Answer 3

Area involved in planning and preparation for action

Rostral to motor cortex

Question 4

What are the symptoms of a unilateral mild stroke?

Answer 4

Contralateral hemiparesis (one-sided weakness)

Partial paralysis

Question 5

What are the symptoms of a unilateral severe stroke?

Answer 5

Contralateral hemiplegia (one-sided paralysis)

Abnormal expression of spinal reflexes

Babinski’s sign

Question 6

What is affected by an anterior cerebral artery infarction?

Answer 6

Lower limbs

Question 7

What is affected by a middle cerebral artery infarction?

Answer 7

Upper limbs and face

Middle cerebral artery infarctions that affect the outflow of the motor cortex thought the internal capsule are devastating

Question 8

What is the corticospinal tract?

Answer 8

Crossed pathway arising mainly from primary motor cortex

Fibres descend through ventral part of brainstem

1. Internal capsule in forebrain
2. Cerebral peduncle in midbrain
3. Pyramid in medulla

Question 9

What do corticobulbar fibres do?

Answer 9

Branches from cortex terminate in regions that control brainstem motor nuclei

Control cranial nerve motor function

Question 10

Where do the corticospinal fibres cross the midline?

Answer 10

Motor decussation in low medulla

Question 11

How do the corticospinal fibres continue in the spinal cord?

Answer 11

As the lateral corticospinal tract in the dorsolateral funiculus of the spinal cord

Question 12

What is the uncrossed ventral corticospinal tract?

Answer 12

In humans, 10-20% of fibres descend ipsilaterally

Ultimately either cross or provide control for axial muscles

Question 13

What is the result of lesions to the corticospinal tract?

Answer 13

Permanent deficits most extreme in finger movement and manipulation - loss of dexterity

Question 14

When do direct cortico-motorneuronal connections develop?

Answer 14

Post-natally at about 9 months

Question 15

What are the sources of input to the motor cortex?

Answer 15

1. Motor association areas
2. Cerebellum
3. Basal ganglia
4. Sensory afferents

Question 16

How is grip force controlled?

Answer 16

1. Motor cortex estimates appropriate force
2. Cutaneous sensory afferents detect slippage
3. Output of corticospinal neurons corrects for slip by strengthening grip

Feedback control system

Question 17

What is a long latency stretch reflex?

Answer 17

Proprioceptive information projects to motor cortex

Permits precisely controlled movements

Question 18

What are the inputs to motor association areas?

Answer 18

1. Prefrontal cortex
2. Parietal cortex
3. Cerebellum
4. Basal ganglia

Question 19

Where do the motor association areas project to?

Answer 19

1. Primary motor cortex
2. Spinal cord
3. Cerebellum
4. Basal ganglia

Question 20

What do the cingulate motor areas control?

Answer 20

Expression of emotions via motor systems

Facial expression

Question 21

What kind of movement is the lateral premotor cortex important for?

Answer 21

Movements dependent on sensory trigger signal

Interaction with an external object

Question 22

What kind of movement is the supplementary motor area important for?

Answer 22

Internally-generated movement

Bimanual movement

Question 23

What are mirror neurons?

Answer 23

Neurons that fire in relation to making a movement as well as observing the same movement being performed by others

Question 24

What area of the brain is involved in mental rehearsal?

Answer 24

Supplementary motor area

Helps predict the sequence of movements needed to achieve a particular end point and in understanding their consequences, a critical element of feedforward motor control using forward models

Question 25

Which area of the brain is associated with planning, cognitive and decision-making skills?

Answer 25

Prefrontal cortex