Chapter 14: Brain Movement Flashcards by Carissa Garcia

What are the three levels of hierarchical motor control? What is their main function? What are the structures involved?

LEVELS:

High
Middle
Low

FUNCTION:

strategy
tactics
execution

STRUCTURES:
1. association areas of neocortex, basal ganglia

motor cortex and cerebellum
brain stem and spinal cord

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Quick movements cannot be altered by sensory feedback.

Why is it that obtaining sensory information during the movement crucial?

not for the movement at hand but for improving subsequent similar movements

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Lateral pathways are involved in […] of the […] and are under […] control.

Ventromedial pathways are involved in […] and […] and are under […] control.

voluntary movement; distal musculature; direct cortical control

control of posture; locomotion; brain stem control

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What is the most important component of the lateral pathways?

corticospinal tract/pyramidal tract

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Describe the corticospinal tract (2):

longest and largest in the CNS

2. two-thirds of the axons originate in areas 4 & 6 of the frontal lobe (motor cortex)

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Along the corticospinal tract, where does decussation occur?

at the junction of the medulla and spinal cord (pyramidal decussation)

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Along the rubrospinal tract, where does decussation occur?

in the pons (almost immediately)

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Describe the pathway of the corticospinal tract:

CORTICAL:

motor cortex (3/4) — inter capsule [telencephalon and thalamus] — cerebral peduncle — midbrain [pons] — medulla [medulla pyramid] — *** — lateral column of the spinal cord

*** = decussation occurs

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Describe the pathway of the rubrospinal tract:

RUBRO:

red nucleus [midbrain] — *** — lateral column of the spinal cord

*** = decussation occurs

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What is the effect of lesions in both corticospinal and rubrospinal tracts?

unable to make fractioned movements of the arms and hands
could not move shoulders/elbows/wrists/fingers independently
voluntary movements were slower and less accurate

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What is the effect of lesions in the corticospinal tract?

temporary– movement deficient
permanent– flexor weakness and inability to move fingers independently

Summary: immediate paralysis on contralateral side but considerable recovery

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If there were only lesions in the corticospinal tract and then later a subsequent lesion in the rubrospinal tract, what would occur?

recovery would reverse

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The ventromedial pathways contain […] tracts that originate in the […] and terminate among the […] controlling […] and […] muscles.

4 descending; brain stem; spinal interneurons; proximal; axial

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What are the 4 tracts in the ventromedial pathway?

vestibulospinal tract
tectospinal tract
pontine reticulospinal tract
medullary reticulospinal tract

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What sensory information does the ventromedial pathway use (3)?

balance
body position
visual environment

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Using sensory information, what does the ventromedial pathway maintain (2)?

balance

2. body posture

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Which tracts function to:

Keep the head balanced on the shoulders as the body moves through space and to turn the head in response to new sensory stimuli.

vestibulospinal and tectospinal tracts

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Where does the vestibulospinal tract originate?

Where does the tract relay information?

vestibular nuclei of the medulla

relay from the vestibular labyrinth (inner ear)

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Vestibular labyrinth consists of […] and […] in the […] bone that are closely associated with the […].

fluid-filled canals; cavities; temporal; cochlea

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Movement of the head and motion of the labyrinth leads to

fluid movement of the labyrinth activates the hair cells

2. hair cells signal vestibular nuclei via CN VIII

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Components of the vestibulospinal tract projection (2):

projects bilaterally down the spinal cord

2. projects ipsilaterally as far down as the lumbar spinal cord

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Vestibulospinal tract:

Bilateral projection helps with…

Ipsilateral projection helps with…

B–
1. activates the cervical spinal circuits that control neck and back muscles

guide head movement

I–
1. maintain upright and balanced posture

facilitates extensor motor neurons of the legs

Tectospinal tract originates in the […] of the […], which receives direct input from the […].

superior colliculus; midbrain; retina

The reticulospinal tracts arise mainly from the […].

reticular formation of the brain stem

What are the two descending tracts of reticular formation?

1. pontine (medial) reticulospinal tract | 2. medullary (lateral) reticulospinal tract

Pontine reticulospinal tract:

enhances the antigravity reflexes of the spinal cord

How does the pontine reticulospinal tract enhance antigravity reflexes?

1. facilitate extensors of the lower limbs | 2. help maintain a standing posture by resisting the effects of gravity

Medullary reticulospinal tract:

liberates the antigravity muscles from reflex control ** opposite of pontine reticulospinal tract

Where is the motor cortex located?

frontal lobe area 4 lies just anterior to the central sulcus on the precentral gyrus area 6 lies just anterior to area 4

What area is known as the primary motor cortex or M1?

area 4

Area 4 vs area 6:

4-- motor cortex 6-- evoke complex movements on either side of the body

What are the two somatotopically organized motor maps of area 6?

1. LATERAL: premotor area (PMA) | 2. MEDIAL: supplementary motor area (SMA)

PMA vs SMA:

perform similar functions but on different muscle groups P-- connects primarily with reticulospinal neurons that innervate proximal motor units S-- send axons that innervate distal motor units directly

Area 5:

a target of inputs from the primary somatosensory cortical areas 3, 1, and 2

Area 7:

a target of high-order visual cortical areas such as MT

Lesions in posterior parietal cortex causes:

1. bizarre abnormalities of body image and the perception of spatial relations 2. neglect the side of the body opposite of the lesion

What are two particular interests in the posterior cortex?

1. area 5 | 2. area 7

These [...] areas, along with the [...], represent the highest levels of motor control hierarchy.

prefrontal; posterior parietal cortex

Prefrontal and posterior parietal cortex converge their axons on what area? This junction is where the signal transform to what?

area 6 transforms from what actions are desired to how these actions will be carried out

What areas would become active on a PET monitor if the two following orders were given? 1. Subjects asked to perform a series of finger movements from memory. 2. Subjects asked only to mentally rehearse the movement without movement.

1. areas 4 and 6 | 2. area 6 only

What area plays an important role in the planning of the movement?

area 6

Cells in the SMA typically increase their discharge rates...

a second before the execution of hand or wrist movement

A lesion of the SMA on one side leads to? What does this mean about the SMA connections?

movement deficient pronounced for tasks requiring the coordinated actions of the two hands SMA is closely linked via the corpus callosum

Apraxia:

selective inability to perform complex motor acts

Cells in the PMA typically increase their discharge rates...

when instructions were given and continued until the trigger stimulus came on and the movement was initiated

The major subcortical input to area 6: Hint-- located in a nucleus of the dorsal thalamus

ventral lateral (VL) nucleus

The input of the VL arises from the [...] buried deep within the [...].

basal ganglia; telecephalon

The basal ganglia is a target for...

cerebral cortex (prefrontal/frontal/parietal cortex)

What is the function of the following loop: Basal ganglia, thalamus, cortex (supplementary cortex)

selection and initiation of willed movements

What does the basal ganglia consist of?

1. caudate nucleus 2. putamen 3. globus pallidus 4. subthalamic nucleus 5. substantia nigra

Substantia nigra location:

midbrain structure that is reciprocally connected with the basal ganglia of the forebrain

The striatum consist of the...

putamen and caudate together

The striatum is a target of the [...] input to the [...].

cortical; basal ganglia

The globus pallidus is the source of the [...] to the [...].

output; thalamus