L7 Motor Cortex and Voluntary Movements

Question 1

What percentage of the corticospinal axons cross at the pyramidal decussation and travel in the lateral Corticospinal tract?

Answer 1

About 90%

Question 2

What percentage remain in an ipsilateral ventral corticospinal tract and project bilaterally to medial motor neurons serving axial muscles

Answer 2

About 10%

Question 3

What structures are the subcortical motor projections to the spinal cord from?

Answer 3

• Reticular formation
• Vestibular nuclei (medial and lateral)
• “Red” nucleus (Rubrospinal pathway is well known in non-human primates – preliminary
  evidence in human beings).

Question 4

What is the purpose of the feedforward mechanism of postural control?

Answer 4

for anticipated postural instability

(essentially keeps you from falling the examples was the calfs bracing for the biceps to contract)

Question 5

What is the purpose of the feedback mechanism of postural control?

Answer 5

for unanticipated postural instability

Question 6

Which somatotropic region of the primary motor cortex is assoc. w ankle control?

Answer 6

Medial

Question 7

Which somatotropic region of the primary motor cortex is assoc. w face, mouth, mastication control?

Answer 7

lateral

Question 8

Why are the face and finger representation of the haemophilus larger than the other areas?

Answer 8

Bc there is a greater degree of control to these areas

Question 9

T/F somatotopic organization of moto cortex is not plastic

Answer 9

False

(The brain can be retrained to have more refined control at other body parts depending on how those body parts are exposed to movement)

Question 10

What three thing can alter neron properties?

Answer 10

• Pathology or trauma
• Normal experience (e.g., motor-skill learning)
• Therapy

Question 11

What does the primary motor cortex control?

Answer 11

simple features of movement

Question 12

What encodes Direction of Movement?

Answer 12

• Neurons in motor cortex have a “preferred direction”

Question 13

What guides movement?

Answer 13

Internal models and are learned with practice

Question 14

In the theory of “optimal” feedback control, what adjusts sensory feedback?

Answer 14

an efferent “copy” of the motor command

Question 15

Damage to which motor area is assoc. w complex motor dysfunctions?

Answer 15

premotor area

Question 16

T/F outputs of the primary motor cortex and premotor areas overlap in the spinal cord.

Answer 16

True, However, inputs to the two cortical regions have differences, and

Question 17

When are the premotor and posterior parietal cortical areas active?

Answer 17

during mental rehearsal of a movement

Similar same patterns of activity occur during such planning and during the actual movement. Example: reaching for and grasping an object.

Question 18

What info. does reaching require?

Answer 18

• visual information abt target location proprioceptive info about the limb being used

Question 19

What is the relationship b/n peak velocity of a movement and the distance of the target?

Answer 19

Peak velocity of a movement to a target is proportional to target distance

(meaning the longer the distance the faster the speed)

Question 20

What determines grasping of an object?

Answer 20

mostly shape of the target object

(That is, the “kinematics of grasping … depend on the object itself and not on its location.” )

Question 21

What are the steps of grasping?

Answer 21

• Hand preshapes as it moves toward target object
• Grip size first increases and then decreases as object approached
• Precision grip requires more cortical circuitry (briaon power)

Question 22

What regulates reaching and grasping?

Answer 22

parallel parietal cortex premotor pathways

Question 23

reaching and grasping are goal-directed movements that require what?

Answer 23

transformation of sensory information about the environment into signals that control muscles.

Question 24

Where are mirror neurons primarily located?

Answer 24

ventral premotor area

Question 25

T/F mirror neurons discharge only when the monkey does the action

Answer 25

Fasle,

they also discharge when the monkey observes another primate (monkey or human) making the same movement.

Question 26

Studies of motor control include the following protocol: Stand and upon command pull an object toward you by flexing your arms. In this experiment, “upper” motor neurons are most likely to do which of the following?

a. Only activate arm muscles (e.g., biceps)
b. First activate arm muscles (e.g., biceps) followed by leg muscles (e.g., gastrocnemius)
c. First activate leg muscles (e.g., gastrocnemius) followed by arm muscles (e.g., biceps)
d. Activate arm (e.g., biceps) and leg muscles (e.g., gastrocnemius) at the same time

Answer 26

C

Question 27

Explain the results of robot-based motor hand therapy

Answer 27

Your are able to train the brain post stroke to repeat movement. Those who used this therapy experienced a better recovery of motor neuron function than those who didn’t.

This only targeted very small movements not in simple movements like supination

Question 28

What does the babinski sign indicate?

Answer 28

an upper motor neuron injury

Question 29

Who would you not use the babinski sign test on?

Answer 29

Babies under the age of 2

this is because they have not yet developed enough of their neuronal system to give a conclusive response to the foot stimulus.