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Neuroscience > Lecture 6: Motor and Premotor Cortex > Flashcards

Lecture 6: Motor and Premotor Cortex Flashcards

1
Q

what are the 3 sections of the motor cortex

A

Primary motor cortex (M1)

Premotor cortex

Supplementary motor
area

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2
Q

which area of the motor cortex has somatotopic organization

A

the primary motor cortex (M1)

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3
Q

which areas are enlarged in the primary motor cortex’s somatotopic organization?

A

motor maps for movements are requiring fine motor control are enlarged (fingerers, face, etc)

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4
Q

what kind of movement is the primary motor cortex involved with

A

voluntary movements of contralateral body parts

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5
Q

what about movement does the primary cortex encode

A

force, direction, distance, and speed of movement

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6
Q

what is alien hand syndrome

A

only contralateral primary motor cortex is activated

involuntary uncontrollable movement of the upper extremity

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7
Q

where is the premotor cortex

A

anterior to the M1 (primary motor cortex) in frontal lobe

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8
Q

what is the function of the premotor cortex?

A

Motor planning - select the appropriate movement to perform

  • Mirror neurons for action observation (watching something we want to learn)
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9
Q

how does the premotor cortex influence motor behaviour

A

primarily via connections with M1

less commonly via axons projecting though the pyramidal tracts

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10
Q

what do premotor cortex lesions cause

A

Impaired:
Speed and automaticity of
reaching/grasping

Sequential movements

Gait and posture

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11
Q

what is the function of the Supplementary Motor Area (SMA)

A

Programming complex sequences and coordinating bilateral movements

  • Selects movements based on previous experience
  • Active during motor imagery practice (imagining doing an action)
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12
Q

what does an unilateral lesion of the supplementary motor area cause

A

complete lack of contralateral movement and impaired ipsilateral movement

Antiphase movements can be affected (arms or legs doing different motions like typing or walking)

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13
Q

what are the 3 inputs to the motor cortex to create movement?

A

intention - prefrontal cortex

planning - premotor cortex +SMA

programming and execution - primary motor cortex

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14
Q

LMNs receive instructions from which 3 sources?

A
  • Upper Motor Neurons
    – Descending pathways
  • Local Circuit Neurons/Interneurons
  • Sensory inputs
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15
Q

how are LMNs organized in the anterior horn

A

▪ Medial = proximal muscles

▪ Lateral = distal muscles

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16
Q

what are interneurons / local circuit neurons?

A

the “middle man” that branches locally to innervate other neurons

primarily inhibitory towards unwanted movement

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17
Q

do interneurons / local circuit neurons project contra laterally or ipsilaterally?

A

both

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18
Q

what are the two types of interneurons / local circuit neurons?

A

long distance

short distance

both link to anterior horn in spinal cord

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19
Q

what are long distance interneurons?

A

activate medial aspect of anterior horn

span multiple levels of spinal cord and can cross sides

bilateral control of Proximal muscles for balance and postural control

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20
Q

what are short distance interneurons?

A

Activate lateral aspect of anterior horn

Span few spinal levels and ipsilateral

Distal muscles for fine motor control

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21
Q

what are the 2 kind of tracts of the descending motor pathways

A

Pyramidal tracts

Extrapyramidal tracts

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22
Q

what are the pyramidal tracts responsible for

A

skilled, voluntary movements of the limbs

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23
Q

where do extrapyramidal tracts originate

A

in the brainstem

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24
Q

what are the extrapyramidal tracts responsible for

A

posture balance, gait

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25
Q

what are the 3 pyramidal pathways

A

lateral corticospinal pathway

anterior corticospinal pathway

corticobubar pathway

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26
Q

what are the 4 extrapyramidal pathways

A
  • Vestibulospinal Tract
  • Reticulospinal Tract
  • Tectospinal Tract
  • RubrospinalTract
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27
Q

where are the extrapyramidal pathways located?

A

most are in the medial part of spinal cord

28
Q

where does the lateral cortocospinal tract originate?

A

motor cortex, mostly M1

29
Q

where does 85% of the corticospinal tract cross

A

the pyramidal decussation

30
Q

what is the destination of the lateral corticospinal tract

A

lateral LMN of spinal cord or short distance interneurons

31
Q

what would a lesion on the lateral corticospinal tract cause

A

Impairments on contralateral side

32
Q

does the anterior corticospinal tract cross to the other side?

A

not at the medulla, but most of it crosses in the spinal cord

33
Q

what is the destination of the anterior corticospinal tract

A

Terminates bilaterally in spinal cord

  • via long distance interneuron networks
34
Q

what is the function of the anterior corticospinal tract

A

Gross control of proximal postural muscles

35
Q

what happens if there is a lesion on the anterior corticospinal tract

A

there is minimal clinical effect

36
Q

do most corticospinal fibers synapse directly with LMNs

A

some do that are involved with finer muscle control

most synapse with spinal interneurons that in turn synapse with LMNs

37
Q

where does the corticobulbar tract originate?

A

motor cortex

38
Q

what is the function of the corticobulbar tract?

A

Controls efferent activation of cranial nerves

38
Q

what is the destination of the corticobulbar tract

A

Most terminate bilaterally on local circuit neurons in brainstem

LMN nuclei of cranial nerves

39
Q

What region of the face is the primary motor cortex responsible for?

A

lower face (contralateral)

40
Q

what would an UMN injury (in the corticobublar tract) cause

A

Weakness in contralateral inferior facial
muscles

very concerning

41
Q

what would a LMN injury in the facial nerve cause

A

Weakness in ipsilateral superior and
inferior facial muscles

injury is outside of brain so less concerning

42
Q

If there is a lesion to the right facial nerve, where would you expect there to be weakness?

A

inferior and superior right side of face

43
Q

what happens with a transverse cord lesion

A

both sides of the level of spinal cord

Bilateral loss of pain/temperature, vibration/position sense, and voluntary motor function at and below lesion

43
Q

What part of the brain would you expect to have a lesion if you have difficulty tapping your head and rubbing your belly at the same time?

A

Supplementary motor
area

44
Q

what happens with a hemicord lesion (Brown-Sequard Syndrome)

A

damage to one half of spinal cord

Ipsilateral loss of vibration/position sense and voluntary motor function

Ipsilateral loss of pain and temperature over 1-2 segments near lesion

Contralateral loss of pain and temperature

45
Q

what is the destination of the extrapyramidal pathways

A

Innervates bilateral local long interneuron circuits

46
Q

what is the function of the rubrospinal tract

A

Modulation of flexor muscle tone

47
Q

what is the function of the Vestibulospinal tract

A

posture and balance

48
Q

what is the function of the Reticulospinal tract

A

gait, posture, excites/inhibits muscle tone

49
Q

what is the function of the Tectospinal tract

A

Eye/head motion

50
Q

what are the 4 clinical presentations of extrapyramidal disorders?

A

Slowing or loss of voluntary and automatic movements

Postural instability

Abnormal movements

Usually bilateral deficits

51
Q

which system controls volitional control

A

pyramidal tracts

52
Q

which system controls automatic control

A

extrapyramidal tracts

53
Q

do the pyramidal systems have more long or short local circuit neurons

A

Mostly short distance local circuit neurons (except anterior corticospinal tract)

54
Q

do the extrapyramidal systems have more long or short local circuit neurones

A

Long distance local circuit neurons

55
Q

What is the function of the Lateral Corticospinal Tract

A

Main voluntary motor pathway

  • Skilled, voluntary movements of the limbs
56
Q

Consider the lateral corticospinal tract originating from the left motor cortex. If this tract was injured below the pyramidal decussation, where would you expect to see motor deficits?

A

In the extremities on the right side of the body

57
Q

Which part of the brain is active while you watch Serena Williams hit a tennis serve?

A

Premotor cortex

58
Q

If there is damage to the primary motor cortex, which deficits might you observe?

Difficulty swallowing

Weakness in the contralateral hand

Weakness in the lower face

All of the listed answers are correct

A

All of the listed answers are correct

59
Q

Link the following descending pathway to the appropriate interneuron network

Anterior Corticospinal Tract and short distance interneuron network

Vestibulospinal Tract and long distance interneuron network

Lateral Corticospinal Tract and long distance interneuron network

Reticulospinal Tract and short distance interneuron network

A

Vestibulospinal Tract and long distance interneuron network

60
Q

Which part of the brain is active when you are imagining yourself performing a motor task?

A

Supplementary Motor Area

61
Q

what is the Cingulate Motor Area responsible for

A

the upper face, bilaterally

62
Q

_______ motor neuron injuries typically cause more wasting than ________ motor neuron injuries

A

Lower, Upper

63
Q

If there was damage to short distance local circuit neurons in the spinal cord, what would you expect to see?

A

Problems with fine motor control

Neuroscience (20 decks)

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