Motor Systems II

Question 1

What is the pyramidal tract?

Answer 1

Corticobulbar (CN nuclei) and corticospinal tracts (spinal cord) of the nervous system

Question 2

Lesions of the pyarmidal tracts causes what deficit?

Answer 2

Deficits in control of the hand

You lose the ability to oppose the thumb and index finger.

Insead, you use the hand like a cup.

You can’t independently extend ONE digit so you use cupping and scooping movements.

Reaching, locomotion and other movments are still intact. you can still move the PROXIMAL parts of the limb.

Question 3

Lesions of the primary motor cortex cause what deficits?

Answer 3

1. Upper motor neuron syndrome

Paresis

Increased extensor tone/ stretch reflexes (reticulospinal tract)

Babinski reflex

2. Deficits in fine motor control of hand, foot mouth and tongue

3. Cortical Bulbar signs

Lower facial muscles: loss of smiling, baring of teeth symmeterically, puff out cheek on CONTRALATERAL side

Accessory nucleus: weakness of IPSILATERAL trapezius/SCM

Hypoglossal nucleus: weakness of CONTRATERAL tongue

Question 4

What does a positive Babinski sign indicate?

Answer 4

A lesion in the LEFT Primary Motor Cortex leads to a POSITIVE Babinski reflex (toes fanning up) on the RIGHT side.

It is indicative of corticospinal damage.

Question 5

What were Alf Brodal’s autobiographical observations on his stroke?

Answer 5

Early (30 days):

Paresis, but recovery of proximal joint function

No extension of fingers, thumb

2-5 months:

Butonningn clothes, holding a fork (difficult)

Clumsiness w/ finger movements (did not know next move–automaticity was lost)

Sense of “mental effort”–had to think about NEXT move

Question 7

What are the afferent projections to the premotor cortex (6)?

Answer 7

1. Prefrontal cortex

2. Supplementary motor area
3. Posterior parietal (Areas 5 and 7)
4. Cingulate motor area
5. Cerebellum and basal ganaglia via the thalamus

Question 8

What are the efferent projections to the Premotor cortex?

Answer 8

1. Area 4
2. Supplementary motor area
3. Posterior parietal
4. Prefrontal areas
5. Basal ganglia
6. Brainstem, red nucleus
7. Corticospinal

Question 9

What do stimulation studies show the premotor cortex is responsible for?

Answer 9

Coordinated turning of eyes and head (contralateral)

Sunergistic movements (contralateral hand seems to lead and head turns to watch)

Question 10

What is the funciton of the premotor cortex?

Answer 10

1. Involved with sensorimotor transofrmations- transforms a CUE into a MOTOR ACTION
2. Involves PLANNING and LEARNING
3. Dorsal premoror area for ARM movement
4. Ventral Premotor area for HAND movement

Question 11

What is the physiology of the premotor cortex?

Answer 11

The premotor cortex FIRES during PREPARATION for movement

and

in relation to the SENSORY information.

(instructor stimulus, trigger stimulus)

Question 12

What are the side affects of a lesion to the premotor cortex?

Answer 12

Can’t execute complex motor plans requiring visuomotor transofrmation (Inability to reach around barrier to obtain visible food reward)

Can’t steer arm correctly

Can’t learn new sensory motor assocaiations.

**NEED sensory information to plan/execute movement**

Question 13

What is the ventral premtor cortex?

Answer 13

PMv = HAND

1. Involved with control of GRASPING
2. Encodes higher level properties of grasping
3. Contains mirror neurons

Question 14

What are mirror neurons? What is the function of mirror neurons?

Answer 14

Mirror neurons discharge when a monkey grasps an object or watches another monkey or human grasp the same object.

Function:

Imitation- how neurons learn

Action understanding- how you understand another’s actions

Intention- how you understand whether or not movement is threatening

Question 15

What are the afferent projections to the supplementary motor area?

Answer 15

1. Area 4 (Premotor cortex)
2. Prefrontal cortex/pre-SMA
3. Posterior parietal
4. Basal Ganglia
5. Cerebellum

Question 16

What are efferent projections from the supplementary motor area?

Answer 16

1. Area 4
2. Straitum
3. Brainstem
4. Corticospinal

Question 17

Electrical stimulation of the supplementary motor cortex….

Answer 17

Evokes CONTRALATERAL limb movmenets invovling multiple joints, postural changes

Indicates that there is a homunculus.

Question 18

Rank from greater to lesser control of movements

Primary motor cortex

Premotor Cortex

Supplementary motor area

Answer 18

Premotor cortex (global movements) > SMA > Primary motor (single joint)

Question 19

What is the funciton of the supplementary motor area?

Answer 19

1. INTERANAL generation of movments
2. SEQUENCES of learned movements

Question 20

Large changes in SMA neurons are related to what type of movement?

Answer 20

Self- initiated movements!

(Also known as Bereitshaft potential)

CONTRALATERAL

Neurons in SMA discharge in relation to specific sequences of internally guided movements.

Question 21

What would a lesion to the supplementary motor area cause?

Answer 21

Deficits in internally guided and sequences of movements.

Question 22

You see a patient with a lesion to their Supplementary Motor Area. What deficits might you see?

Answer 22

1. Patient may become stimulus bound (They are DRIVEN BY STIMULI)

show them glasses- they put on glasses

show them toilet- they go to the bathroom

2. They may not recognize their has as their own and the hand may act in ways that are contralateral to what you want it to do (Alien hand syndrome)
3. They may have trouble executing learned sequences

Question 23

What happens to the SMA as tasks become proficient?

Answer 23

As tasks become proficient/habit…the SMA REDUCES its activity and the MOTOR CORTEX assumes control. (automatic movements)