Motor Control

Question 1

What is the main function of the primary motor cortex?

Answer 1

directs movement by controlling muscle contraction

Question 2

Where is the primary motor cortex locates?

Answer 2

precentral gyrus in the frontal lobe

Question 3

What does the primary motor cotex spatial map show?

Answer 3

disproportions
Hands and lips have a larger area dedicated to them

Question 4

What is the influence of a single cortical upper motor neurosn on muscle activity?

Answer 4

individual cortical motor neurons can drive numerous motor neuron pools from a group of different muscles involved in moving a limb toward a desired goal
*organized movement

Question 5

How are movements generated by the primary motor cortex characteristized?

Answer 5

coordinated and purposfully organized

Question 6

What are the three key takeaways from neuronla population coding of movement direction?

Answer 6

1. much of motor cortex is active for every movement
2. activity of each cell represents a singe “vote” for movement direction
3. direction of actual movement is deteremined by tally averagibg all the votes of the population

Question 7

What does a poplulation vector represent?

Answer 7

the movement direction encoded by the simultaneous activity of the entire population of recorded units

Question 8

What does damage at the C1-7 level cause?

Answer 8

quadrilegia (tetraplegia)
loss of normla function in all four limbs

Question 9

What does damage at the T1-12 and L1-5 level cause?

Answer 9

paraplegia
loss of normla function in legs
full control and feelikng in the arms and hands

Question 10

What does damage at the S1-5 level cause?

Answer 10

loss of feeling in the genital arae

Question 11

Explain a brain-machine interface

Answer 11

a population vector algorithm translates brin waves inot intended movement commands
allows a paralysed person to manipulate objects

Question 12

What is the result in rats when a motor nerve is cut?

Answer 12

the cortical regions that previously evoked that movment now causes muscle movment somewhere else
*motor map reorganized

Question 13

What can occur in rats training for a task requiring precise reaching and grasping?

Answer 13

the respresentation of the digits and wrist has epxanded into areas previously associayed with the shoulder and elbow
*younger at the start of training the larger the re mapping

Question 14

What are the firing patterns of supplementary motor area neurons?

Answer 14

tey response only during a pulling response that was to be followed by a rushing response in a ready set go task

Question 15

What is the nonprimary motor cortex?

Answer 15

frontal lobe regions adjacent to the primary motor cortex that contribute to motor control and modulate the activity of the primary motor cortex

Question 16

What is the supplementary motor area?

Answer 16

a region of the nonprimary motor cortex that receives input from the BG and modulates the activity of the primary motor cortex
*internally generates stimuli

Question 17

What is the premotor cortex?

Answer 17

a region of the nonprimary motor cotex just anterior to the primary motor cortex
*external cues (sensory information)

Question 18

Where are many mirror neurons found?

Answer 18

ventral portion of the premotor cortex F5

Question 19

When does a mirror neuron fire the most?

Answer 19

activation is increased most strongly in response to scense of action with clear intention
*movement has a goal - grasping an object vs no object

Question 20

How doe mirror neurons distinguish between possible intentions?

Answer 20

they response more intensely to the basic biological function of drinking than to cultrally acquired act of cleaning

Question 21

How are mirror neruons a survival advantage?

Answer 21

understanding the intention of others is fundamental to human social behaviour

Question 22

What are mirror neurons?

Answer 22

a neuron that is active both when an individual makes a particular movement and when that individual sees another make that same movement

Question 23

What was found when fMRI’s were done to image disgust?

Answer 23

feeling disgust activated similar parts of the brain when human volunteers experiences the emotion while smelling a disgusting odor or when the smae subjects watched a film clip of someone else digusted

Question 24

What may overalpping neuron groups represent?

Answer 24

a physical neural mechanism for human empathy that permits understanding the emotions of others

Question 25

How might underactivation of mirror neurons affect autism?

Answer 25

the pars opercularis region is less actiavtes in children with autism than in controls contains mirror neurons deficits in activating brain regions underlying imitation and empathy contribute to the social impairments of autism

Question 26

What do the lower motor neurons in the medial ventral horn govern?

Answer 26

posture, balance, locomotion, and orienting movements of the head

Question 27

What do the lower motor neurons in the lateral ventral horn govern?

Answer 27

mediate the expression of skilled voluntary movements of the distal extremities

Question 28

Where does the lower motor neuron in the medial ventral horn receive descending input from?

Answer 28

pathways that originate in the brainstem -> through anterior white matter of the spinal cord, then termination bilaterally

Question 29

Where does the lower motor neuron in the lateral ventral horn receive major descending projections from?

Answer 29

the contralateral motor cortex via the main (lateral division) of the corticospinal tract (crosses midline) - runs in the lateral white matter of the spinal cord

Question 30

How is the ventral horn somatotopically organized?

Answer 30

in the grey matter - medial white controls proximal muscles - lateral controls distal muscles

Question 31

What is the pathway of the lateral corticospinal tract?

Answer 31

upper motor neurons in the primary cortex sends axon downward to cross over at the pyramidal decussation the axon then continues downward in the contralateral spinal cord before synapsing on the lower motor neurons in the anterior horn

Question 32

What is the pathways of the corticospinal tract?

Answer 32

motor cortex -> internal capsule -> midbrain -> pons -> meduallry pyramids -> pyramidal decussation -> lateral column of the spinal cord

Question 33

What is the somatic organization of the posterior limb of the internal capsule?

Answer 33

leg trunk arm face (post to ant)

Question 34

What does the right motor cortex control?

Answer 34

the left side of the body

Question 35

What is a common way for the corticospinal tract to be damaged?

Answer 35

by stroke -> large pathway result in contralateral paralysis recovery can occur but fine motor movements are usually least preserved

Question 36

What are the possible injury sites for a fall that results in paraplegia?

Answer 36

bilateral medial frontal lobes (leg region) nerve roots peripheral nerves muscles spinal cord below T10 - likely because only deficits in both left and no weakness anywhere else

Question 37

What are the possible injury sites for an injury that results in quadriplegia?

Answer 37

bilateral frontal lobes (leg and arm region) spinal cord (C7-T1) - likely peripheral nerves

Question 38

What are the possible injury sites for an injury that results in pure motor hemiparesis? (no sensory deficits)

Answer 38

contralateral spinal tract - posterior limbs of the internal capsule or ventral pons * leg, arm, and face axons converge and has not crossed over midline yet

Question 39

What is the function of the vestibulospinal tract and tectospinal tracts?

Answer 39

To keep the head balanced as our body moves and to turn our heads in response to new sensory stimuli

Question 40

What is the pathway of the medial vestibulospinal tract?

Answer 40

projects bilaterally down the spinal cord and activated cervical spinal circuits that control the neck and back muscles to guide our head movements

Question 41

What is the pathway of the lateral vestibulospinal tract?

Answer 41

projects ipsilaterally as far down as the lumbar spinal cord helps maintain an upright and balanced posture by facilitating extensor motor neurons of the legs

Question 42

What is the pathway and function of the tectospinal tract?

Answer 42

superior colliculus -> deccussation -> contralateral termination - orientation response of head and eyes in response to primarily visual stimuli

Question 43

What is the function of the pontine reticulospinal tract? (medial)

Answer 43

enhances the antigravity reflexed of the spinal cord - activation facilitated extensors of the lower limbs to help maintain a standing posture by resisting the effects of gravity

Question 44

What is the function of the medullary reticulospinal tract? (lateral)

Answer 44

liberates the antigravity muscles from reflex control - opposite of pontine

Question 45

What is the feedforward mechanism of postural control?

Answer 45

programmes and typically precede the onset of limb movement

Question 46

What is the feedback mechanism of postural control?

Answer 46

initiates by sensory inputs that detect postural instability

Question 47

What are the indirect pathways from the motor cortex to the spinal cord?

Answer 47

neurons that supply the lateral ventral horn to initiate distal limb movements also terminate on the neurons in the reticular formation to mediate postural adjustments that support the movement

Question 48

What occurs with the activation of the motor cortex with inactivation of the reticular formation?

Answer 48

there will be no postural adjustment * feedforward control

Question 49

What is the cross-extensor reflex?

Answer 49

reflex in response to pain detected by nociceptors caused the ipsilateral (pain) flexor muscles to activate the opposite limb extensor muscles are activated to support the body

Question 50

What is the cross-extensor reflex an example of?

Answer 50

coordinated movement without commands from the brain

Question 51

What are central pattern generators (CPG)?

Answer 51

circuits that give rise to rhythmic motor activity

Question 52

Explain the rhythmic activity in a spinal interneuron

Answer 52

glutamate caused NMDA receptor channels to open - the cell membrane depolarizes, and Ca2+ enters the cell intracellular rise in Ca2+ causes Ca2+ activated K+ channels to open - K+ leaves hyperpolarizing the membrane hyperpolarization allows Mg2+ to enter and clog the channel, stopping the flow of Ca2+ causes the K+ channel to close, resetting the membrane potential

Question 53

What are the primary rhythmic driving force for cyclic behaviours?

Answer 53

spinal interneurons due to their intrinsic pacemaker activity and interconnections

Question 54

What are the stages of walking?

Answer 54

swinging and stance

Question 55

How do the stages of walking change when the speed of walking increases?

Answer 55

decreased cycle time by decreasing the time spent in the stance phase

Question 56

When a cat is trotting, how do the stages of walking change? (LH, LF, RH, RF)

Answer 56

LH and RF are synched LF and RH are synched

Question 57

When a cat is pacing, how do the stages of walking change? (LH, LF, RH, RF)

Answer 57

LH and LF synched RH and RF are synched

Question 58

When a cat is galloping, how do the stages of walking change? (LH, LF, RH, RF)

Answer 58

LH and RH synched LF and RF synched * large decrease in stance phase

Question 59

With a transection of the spinal cord in a cat, what occurs relative to walking?

Answer 59

remains coordinated reflex response (CPG) CPG is a critical pre-cursor that excites the descending pathway to get movement without sensory control (doesn't need top-down control) * movement is not perfect and does not work well in humans (biped)

Question 60

Explain the circuit for the CPG of locomotion

Answer 60

neuronal modules for flexion and extension antagonism are composed of excitatory neurons and reciprocally connected inhibitory interneurons - the received input from excitatory rhythm generator interneurons (reciprocally inhibited)