lecture 8 - motor system Flashcards
functions of motor system during hand movement (8)
- visual info - locate target
- frontal-lobe motor area - plan
- spinal cord carries info
- MN to muscles
- sensory
- sensory cortex receives message
- BG judges, cerebellum corrects
- spinal carries sensory to brain
roles of brain areas in motor control posterior cortex prefrontal cortex premotor cortex motor cortex
PC - sensory info to frontal cortex
PFC - plan movement
PMC- organizes movement
MC - produces specific movement
lateral brain araes
frontal eye field premotor cortex primary motor cortex broca's area parietal cortex
medial brain areas
supplementary motor area
primary motor cortex
anterior cingulate
Macaque single cell recording - flex & extend -- findings firing weight direction
hold bar, when cued - flex or extend. increased resistence with pulley.
- frequency of firing increases before movement = planning.
no resistance: MN active before and through action
with resistance: more activity in planning, more activity in action. - neurons code for direction
movement coding by neurons in the neocortex
monkey cortex, different directions
- maximal firing? further from?
findings: each M1 neuron is maximally activate to a particular direction.
- activity decreased in proportionn to displacement form preferred direction
conclusion: MN calculate distance and direction of movement
- move lever in different directions with electrode motor-cortex neuron. fire maximally at 180 degree in front of body. further from that = less firing = spatial gradient
naming tools & brain
increase blood flow to hand region of motor cortex = relationship btw tool and idea of action
listening to music & motor cortex
pianist = activation in motor cortex, specifically hand area. “thumb” portion may be added for certain songs.
audition related to manual training
rolling ball on table
- overt vs imagery
overt - evoke activity in cerebellum, sensory and motor areas.
imagery - no cerebellum activity, more activity in prefrontal cortex
Primary motor cortex - M1
neuronal population vector model
neurons are limited - need to work together to add/subtract to get desired “direction” that’ll lead to correct motor movement
motor plan
- 5 elements.
plan goal info neuromuscular control info sensory? coarticulation? - vocal and face muscles, prepare for word before you speak.
how far in advance in motor plan mad?
few steps ahead - plans phrase before speaking
on the fly? no..
entirely planned before action = whole two line phrase probably not planned, one line at a time.
longer phrase = slower to start.
cerebellum - organized? - most medial part? what happens when lesioned? intermediate zone - lesion? lateral zone - fxn? floccular lobe
organized ipsilaterally
medial = vermis. lesion = fall ipsilaterally to lesion.
inter = for smooth movements. tremors if lesion
lateral - motor planning; multi-joing movement
flocc - needed for eye movements and balance.
2 types of tremors
intentional tremor = at start and end of movement
action tremor = on the way to target
ballistic movement vs multi-joint
ballistic = one quick movement - overshoot? = hypermetria. issue w motor planning.
cerebellar damage and hypermetria
2 key differences
overshoot
- agonist and antagonist have multiple firing peaks
- peak between agonist and antagonist is 2x as long as normal.
cerebellar damage & prism goggles
trying to see if cerebellar damage patients can learn do motor learning.
goggle shift foveal representation.
neuro intact = prism goggles = poor accuracy, but readjust motor so it hits. after prism - take time to get back to normal
cerebellar damage - high variance in initial throws pre-goggle. with goggle, no adaptation of motor = consistently poor. remove goggles - immediately same as pre-goggle. no mtoro learning
what is motor learning
motor system learns new skills.
supplementary motor area
- motor planning?
what else is it involved with?
like in M1, SMA active before start of action.
- state of readiness for action, action initiation, complex movements, motor imagery
SMA proper vs pre- SMA
proper - main, more posterior
pre- more anterior.
what splits brain into front & back
anterior commisure
- splits SMA
when does pre-SMA peak?
when does proper SMA peak
pre - visual peak is large and motor response is weak
proper - dampened visual peak, greater motor peak
- nc visual is smaller peak , probs dampened bc going through hippocampus.
mirror neurons
- fire when?
- encode what?
- used for ?
- part of movement is absent =
- fire when we see others make a movement.
- encode complete action. -used for imitating, understanding others.
- fill in the blanks. PMC holds mirror cells. MN in premotor doesnt respond when absent, but responseds when it’s absent or hidden. neuron fires with understanding of action
where are human mirror neurons?
-role? importance for?
left hemisphere - maybe overlap w broca’s.
- self action, perception of self-awareness, awareness of actions of others.
- important for gestures & verbal language
BG - 3 important areas.
pathway?
caudate putamen, amygdala, subs nigra.
non linear, cooperation and reciprocity.
disorders of BG
huntingtons chorea - destroy caudate putamen.
involuntary exaggerated movement
-chorea: twitching, related to action, initiation, extremity problem
-athetosis (writhing) - midline problem
PD - loss of DA in subs nigra - muscular rigidity and difficulty initiating and performing movement. akinesia - no spontaneous movement bradykinesia - slow tremors
PD handwriting profile
normal patient: even sequence btw acceleration/deceleration
PD: components dissimilar - interrupted, longer to complete.
Anterior cingulate cortex ACC
-function in?
motor modulation
topographic organization with different effectors
attention, emotion, vigilance, novel/cognitive actions
- A->B; M->L. then switch A->L, M->B. saw ACC activate upon new task
- eye = anterior (frontal eye field); speech = medial ACC (brocas); actions = posterior (PC)
stroop task - incogruent, harde to say words, evoke activtiy in ACC
parietal lobe & motor control
- AIP
anterior intraparietal culcue - gauge grip, automatic. mouth gauge too.
cortical motor disorders
apraxia
callosal apraxia
apraxia =
lesions in
- oral
- limb
problem w actions that are skilled, sequential, purposeful.
- oral = frontal- temporal lesion. rarely presents w broca’s aphasia
- limb = left parietal- temporal lesions
limb apraxia
- lesions
- presentation
lesion in parietal-temporal areas.
- pantomme difficulty - cant mime with object.
imitation
symbolic action - trouble understanding
effector selection - choosing hand when asked is hard
callosal apraxia
problem performing action w left hand in response to verbal command.
- assoc with damage to crossover. info to use left hand needs to cross to right hemisphere - unable or incorrect crossing due to lesion or tumor.
degradation of info - action not the same
