Neuroscience Cortical Control of Movement Frank A. Middleton

Question 1

Direct cortico-motor innervation develops when?

Answer 1

Postnatally - increase in dexterity - increase in white matter tracts

Question 2

Which develops first– intrinsic fine motor control of individual fingers, or extrinsic hand control?

Answer 2

Extrinsic hand control

Question 3

Name the indirect descending pathways, projections to a midbrain or brain stem center, then to the spinal cord.

Answer 3

1. Tectospinal, aka cortico-colliculo spinal
2. Cortico-rubro spinal
3. Cortico-reticulo spinal
4. Cortico-vestibulo spinal

Question 4

Name the direct descending pathways, connections from large pyramidal cells in layer 3 and 5 to the ventral spinal cord.

Answer 4

1. Lateral cortico-spinal

2. Medial cortico-spinal

Question 5

The reticulospinal tract is involved with:

Answer 5

reflexes

Question 6

Antigravity muscles are supplied by what innervation?

Answer 6

Lateral and medial vestibulospinal tracts

Question 7

Axial and midline body operation is innvervated by:

Answer 7

Colliculospinal tract

Question 8

The rubrospinal tract innervated what muscles and actions?

Answer 8

Some distal control, mainly arm flexion

Question 9

Betz cells are what kind of cells?

Answer 9

pyramidal cells

Question 10

Why are Betz cells so big?

Answer 10

They have extremely long axons that project all the way down the spinal cord.

Question 11

Where can the most Betz cells be found?

Answer 11

Motor areas

Question 12

Where is the primary motor cortex?

Answer 12

Lateral and medial surfaces of the premotor cortex

Question 13

The lateral premotor cortex is made up of:

Answer 13

PMd, dorsal premotor area

PMv, ventral premotor area

Question 14

The medial premotor cortex is made up of:

Answer 14

SMA, supplementary motor cortex

CMA, cingulate motor areas

Question 15

T or F: The cortical motor area projects to motor neurons in the spinal cord, either directly or indirectly.

Answer 15

True

Question 16

T or F: The cortical motor area projects to the primary somatosensory cortex.

Answer 16

FALSE. the cma projects to the primary MOTOR cortex

Question 17

T or F: The cortical motor area contains Betz cells.

Answer 17

True, or other large layer V projection neurons

Question 18

T or F: The cortical motor area can be stimulated at low thresholds to produce movements of discrete muscles or muscle groups.

Answer 18

True

Question 19

T or F: The cortical motor area does not display changes in activity related to parameters of movement.

Answer 19

False. CMA do display changes in activity related to parameters of movement.

Question 20

Decerebrate posturing suggests a lesion above or below the red nucleus?

Answer 20

Below (could be brain stem or pontine stroke)

Question 21

Based on experimental data, two key features have emerged for understanding the role of the cortical motor areas in motor control:

Answer 21

1. Individual muscles are represented in multiple locations.

2. Individual corticospinal neurons diverge to influence multiple motor neuron pools, and hence multiple muscles.

Question 22

Cortical motor cells code for:

Answer 22

1. Direction. Individual neurons increase discharge rate for certain directions (ie finger pointing) more than others.
2. Force
3. Muscle activity

Question 23

T or F: The motor cortex does not act alone.

Answer 23

True - Prefrontel, Pre-SMA, SMA, CMA, PMd, PMv, M1, all play a role

Question 24

UMN or LMN: Loss of fine voluntary movements

Answer 24

UMN

Question 25

UMN or LMN: Clonus

Answer 25

UMN

Question 26

UMN or LMN: Decreased superficial reflexes

Answer 26

LMN

Question 27

Lesion above Red Nucleus might involve what structures, and what posturing?

Answer 27

Decorticate posturing, cortex or internal capsule

Question 28

In decorticate posturing, why are legs extended and feet turned inward?

Answer 28

Due to disinhibition of RST and loss of corticospinal flexor tone in legs