Lecture 4: Motor Control pt. I Flashcards by Braden Talbert

what is motor control

process of initiating, directing, and grading purposeful volitional movement

responding actions to environmental stimuli (most of the nervous system components for sensory and integrative function)

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top down vs bottom up motor control

top down = do not need external stimuli

bottom up = respond to external stimuli

CPGs = still work w/o CNS control

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how do reflexes work with motor control

stimulus is sent to the CNS

instead of getting interpreted with cognition, CNS directly interacts with motor neurons causes immediate action

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describe the hierarchial organization of motor control

4 levels

all levels above level 1 = UMN system

neurons in level 1 = LMN system (SC)

2 side loops = basal nuclei and cerebellum

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what are the 4 levels of hierarchy of motor control

level 1 = SC
level 2 = brain stem
level 3 = motor cortex
level 4 = association cortex

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what is functional segregation related to motor control

various functional regions in nervous system for motor control

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what are the components of level 4 of motor control hierarchy (multimodal association cortex) (6)

cingulate motor area (part of limbic system)

posterior parietal cortex (Brodmann 5, 7)

Frontal eye field (Brodmann 8)

Language areas
-Broca’s (Brodmann 44,45)
-Wernickes (Brodmann 22)

prefrontal cortex for functional execution

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what is the function of the cingulate motor area in motor control

reciprocal projections with many structures that have different functions/send different information

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what are the reciprocal projections of the cingulate motor area and their function

L dorsolateral prefrontal cortex = motor planning and execution (working memory)

oribitofronal cortex = collecting/summarizing results of motor programs

cingulate motor area = calculating reward of motor program

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describe how the cingulate motor area calculates “reward” of a motor program performed

emotion related behaviors; motivation vs aversion

making the decision of if it is worth doing something or not

alternate motor control theory = invest and reward

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what are the functions of the posterior parietal cortex in motor control related to vision

Dorsal visual pathways
- process context and spatial rep of objects (where)
-visuomotor transformations = how to respond to visual stimuli (integration of perception to action)

specialized area for reach and grasp (lateralized to L hemisphere)
- process object size
-orientation
-hand matching

saccadic eye movements = hand eye coordination

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functions of the posterior parietal cortex in regard to motor control

functions are lateralized

R = bilateral attention scanning and spatial cognition
- L side hemineglect occurs when R side is damaged; ischemic vs hemorrhagic stroke

L = praxis and language
- L side damaged = apraxia

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what are the components of level 3 motor control

unimodal association cortex made up of:
-supplemental motor area - Brodmann 6
-premotor cortex - Brodmann 6 dorsal/ventral

primary motor cortex (M1) - Brodmann 4

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where is the SMA

medial frontal lobe

anterior to M1

has a gross topographic distribution

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What areas of the brain does SMA “talk to” in regard to motor control; what guides its function?

directly “talks” with cingulate motor area

performance is guided by internal cues - OPEN LOOP/top down; no sensory input required

coordinates sequential tasks

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what areas of the brain are activated in the brain when performing simple motions, complex motions, and imagery of complex motions respectively

simple motion = unilateral M1/S1 activation

complex motion = unilateral M1/S1 and bilateral SMA

imagery of complex motion = bilateral SMA

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functions of SMA in motor control

coordination of bimanual movements during complex movements

active during motor imagery (mental rehearsal of bimanual and sequential tasks)

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locations of primary motor area

dorsal to ventral along brodmann area 6

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functions of premotor cortex in motor control

signals the preparation for movement - via motor set neurons
signals correct and incorrect actions
signals various sensory aspects associated with motor actions - via mirror neurons
distinguishes the same movement based on behavioral context (i.e. picking up full vs empty cup)
relies on external sensory input for movement (conext) - CLOSED LOOP
motor imagery WITH external stimuli; bottom up

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what are mirror neurons

where perception and action integrates

NOT in occipital lobe

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sensorimotor pathway of mirror neurons and it’s function

somatic motor

different neuron for different movement patterns
- strictly congruent = only respond to 1 stimuli
- broadly congruent = respond to multiple

function = understanding intention of the movement (learning)

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emotion pathway of mirror neurons

self and social cognition

recognizing cultural conflict

individualism vs collectivism

helps humans understand one another

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what happens if the sensorimotor and emotion pathways of mirror neurons are not integrated in daily life

autism spectrum disorder

functional impairment of the association cortex results in what

apraxia

apraxia definition

cant perform skilled or learned movements with intact sensory or motor system (loss of mirror neiron connections)

ideational apraxia; it is a loss of what

know the tools but cant use them loss of action sequencing

ideomotor apraxia

know how to perform an activity but cant perform the actual activity

limb kinetic apraxia

unable to make precise, independent but coordinated movx ements

apraxia is mainly related to what 2 parts of the brain

left premotor (6) and posterior parietal cortex (5) compromised mirror neurons

classic model of the homunculus of M1

lower limb to tongue in an inverted representation

updated model of the homunculus of M1 as well as the clinical significance of this new model

3 symmetric concentric topographic representation spaced by 3 cognitive control regions clinical significance: - poor foot, hand, and tongue fine motor control recovery - all UMN neurons control patterns of motion, not contraction of a single mm

describe the motor neuron distribution in M1

chimeric distribution of M1 gross order with gradient distribution (overlap) not like S1 which is still strictly represented in homunculus

describe the neuronal firing in M1

fire 5-100msec before onset of movement fastest region when stimulated = existing mechanisms for direct LMN control

M1 neurons encode what info

force of movement extent of movement speed of movement direction of movement

what defines the intention of the movement in M1

pyramidal cells columnar of neurons oversee specific behavior

describe the S1 homunculus

strictly follows topographic representation of body

function of S1 in motor control

direct projection to M1 adjusts movement constantly

What are the components of the corticobulbar and corticospinal tracts

monosynaptic M1 neurons disynaptic neurons **S1 does NOT contribute much to human corticobulbar and corticospinal tracts

describe monosynaptic M1 neurons and their function

develop postnatally located caudal to M1, anterior bank of central sulcus directly synapse with LMN for fine motor control

describe disynaptic neurons and their function

developed prenatally, through interneurons to LMN located in: -rostral M1 -dorsal and ventral PM/SMA (brodmann 6) -2 from cingulate gyrus -posterior parietal lobe (Brodmann 5)

describe the path for the descending cortical tracts for motor control

through the posterior limb of the internal capsule rotates while descending gross topography maintained above the pons somatotopy = face to LE from anterior to posterior; rotation from medial to lateral

where are the nuclei of the corticobulbar tract and their function with motor control

motor nuclei in brainstem 6 nuclei = w/o CN III/IV/VI for neck/head mm brainstem motor control function = red/reticular/vestibular nuclei; generally inhibition

describe the path for the corticospinal tract

travels all SC levels has collateral terminals for brainstem motor nuclei

where are the decussations for the corticospinal tract and where do the fibers continue afterward

70-90% decussate in pyramid (caudal medulla) = for contralateral body control these tracts descend in the lateral funiculus and form the lateral corticospinal tract for extremity flexors and fine motor control the rest do not decussate and continue ipsilaterally some go to anterior funiculus and form the medial corticospinal tract for bilateral trunk mm and postureal control the rest go to the ipsilateral funiculus to form the ipsilateral lateral corticospinal tract for extremity flexors and fine motor control

level 2 of motor control is made up of what areas of the brain and what are their associated tracts

brainstem midbrain = rubrospinal tract pons = pontine reticulospinal tract and vestibulospinal tract (lateral and medial) medulla = medullary reticulospinal tract

function of rubrospinal tract in motor control and general pathway

fine motor control; flexors of UE and trunk decussates in midbrain descends into lateral funiculus of SC

learning a new skill goes through what circuitry and involved what fibers

through the red nucleus-inferior olivary nucleus-cerebellum circuitry climbing fibers are involved

general functions/path of reticular nuclei in motor control

generally bilateral projections through anterior funiculus pontine reticulospinal tract = all spinal levels, controls extensors (posterior control) medullary reticulospinal tract = all splinal levels, controls flexors (anterior control)

paths of the vestibulospinal tracts and what they control

lateral vestibulospinal tract = ipsilateral anterior funiculus for proximal extremity extensors medial vestibulospinal tract = bilateral anterior funiculus for neck/upper trink extensors

which tracts descend the whole SC

pontine reticulospinal tract lateral vestibulospinal tract medullary reticulospinal tract

how far does the medial vestibulospinal tract descend

into C/S (neck)

how far does the rubrospinal tract descend

to UE

what is decerebrate posture

** without cerebral peduncle; lesion BELOW RED NUCLEUS no functional rubrospinal tract and corticospinal tract no flexor tones no inhibition of level 2 motor control system UE and LE both in EXTENSION synergies

what is decorticate postire

** without cerebral cortex; lesion ABOVE RED NUCLEUS upper limb flexors activated by rubrospinal tract without cerebral cortex inhibition UE in FLEXION synergies LE in EXTENSION synergies

why do both decerebrate and decorticate postires have extension synergies in LEs

in both cases the vestibulospinal tracts are active BLEs are in extension