Cortical control of movement

Question 1

location of primary motor cortex

Answer 1

precentral gyrus - brodmann’s #4

Question 2

organization of primary motor cortex

Answer 2

similar to homonculus for sensory cortex
cells that control the LE are primarily on the medial side of cortex
cells that control the UE and face are primarily are on the lateral side of the cortex

Question 3

function of primary motor cortex

Answer 3

execution of movement. Here is a more specific breakdown from the notes:

initiates and executes voluntary skilled complex movements
regulates force, direction, and speed of complex movements
isolates joint movement – i.e. FRACTIONATION
produces synergistic actions by activating multiple muscle groups and or movements at multiple joints at once
controls reciprocal movements by simultaneously activating a muscle while inhibiting the antagonist
mediates muscle co contraction (when agonists and antagonists need to contract together)
contributes to the establishment of postural stability required in anticipation of voluntary movements

Question 4

s/s associated with lesions in primary motor cortex

Answer 4

S/S will be contralateral to lesion
Affected portion of body will be determined by the location of the lesion in the cortex
lateral cortex = UE and face
medial cortex = LE

S/S include UMN syndrome s/s:

• weakness (paresis)
• spasticity (usually)
• no early atrophy (muscles may atrophy months later due to disuse)
• abnormal reflex activity (Babinski reflex, clonus)
• hyperreflexia
• decreased coordination
• abnormal muscle recruitment
• decreased muscular endurance
• loss of fractionation producing abnormal muscle synergies

Question 5

what arteries supply the primary motor cortex and what do disruptions in each cause

Answer 5

medial portion of the cortex = ACA
disruption will affect LE

lateral portion of the cortex = MCA
disruption will affect UE

Question 6

under what circumstances do lesions in the cortex produce exceptions to the rule that UMNs produce spasticity

Answer 6

may INITIALLY have flaccid paralysis due to cerebral shock for about 1 week
however this often will convert to spasticity after the period of cerebral shock

may occasionally see long term hypotonia if the lesion is very extensive

Question 7

where is the supplementary cortex located and what arteries supply it

Answer 7

Broadmans area 6, medial aspect of cortex
immediately anterior to #4
supplied by ACA

Question 8

2 main functions of supplementary motor cortex

Answer 8

planning internally guided movement that are goal oriented or complex sequences
that is, movement not guided by visual or auditory cues

also helps to control bimanual tasks

Question 9

lesions in supplementary cortex produce what s/s

Answer 9

ideomotor apraxia

difficulty with tasks requiring coordination of hands and feet

Question 10

where is the premotor cortex located and what artery supplies it

Answer 10

Broadmans area 6, lateral aspect of cortex

Supplied by MCA

Question 11

function of premotor cortex and how does it differentiate from supplementary

Answer 11

the premotor cortex plans movements that are guided externally
i.e. ones that require sensory guidance

this is different from the supplementary motor cortex which plans movements that do not require external stimuli

Question 12

deficits associated with lesion in premotor cortex

Answer 12

ideomotor apraxia when performing an action that relies on sensory stimuli

impaired bimanual coordination

Question 13

location/arteries of posterior parietal cortex

Answer 13

Broadmans areas 5 & 7

supplied by MCA (primarily) and PCA

Question 14

location/arteries of primary sensory area

Answer 14

Broadmans areas 3, 1, & 2 on the postcentral gyrus

supplied by MCA (lateral cortex) and ACA (medial cortex)

Question 15

motor deficits associated with a lesion in posterior parietal cortex

Answer 15

ideomotor apraxia, similar to that seen in the premotor cortex

Question 16

motor deficits associated with a lesion in primary sensory area

Answer 16

contralateral sensory motor ataxia (impairment of coordination)
contralateral impaired grip and load force synergies
impaired balance

Question 17

function of cingulate cortex

Answer 17

movement execution during complex behaviors and emotional control of movement

Question 18

function of prefrontal cortex

Answer 18

motor memory and motor learning

Question 19

function of frontal eye fields

Answer 19

activates eyes to look to contralateral side
i.e. left frontal eye field moves eyes to the right
important note: frontal eye fields (motor involvement) are located in the frontal lobe, NOT the occipital lobe where the primary visual cortex (sensory involvement) is
if there is a lesion here, eyes will drift to the side of the lesion - this is because such a lesion here will interrupt the innervation that moves the eyes to the opposite side and thus those muscles simply remain inactive

Question 20

where are the cell bodies whose axons form the corticospinal-corticobulbar pathway located

Answer 20

primary motor cortex - most lateral portion where the face is represented 
premotor cortex
supplementary area
primary sensory cortex
frontal eye field

Question 21

where do the cell bodies whose axons form the corticospinal-corticobulbar pathway terminate

Answer 21

alpha motor neurons, gamma motor neurons, and interneurons (highest density)
cranial nerve motor nuclei - corticobulbar
ventral horn of the spinal cord - corticospinal

Question 22

what is a brown-sequard lesion and what motor deficits are associated with it

Answer 22

Lesion in half of the spinal cord
Ipsilateral LMN symptoms at site of lesion
Ipsilateral UMN symptoms below site of lesion

Question 23

mixed UMN and LMN and vestibulospinal lesions in the spinal cord

Answer 23

Alpha or LMN: hypotonia, early atrophy, hyporeflexia, weakness to muscles at the lesion on ipsilateral side

Lateral corticospinal tract: ipsilateral UMN symptoms below the lesion

Lateral vestibulospinal tract: ipsilateral LMN symptoms below the lesion