Motor system Flashcards
motor cortex M1
initiating, and directing commands for voluntary movements to lower level circuits
basal ganglia tov motor action
gating proper initiation of movement, selecting and inhibiting motor actions, simple learning
cerebellum tov motor action
sensory motor coordination, smoothing of movements -> error correction.
brainstem tov motor action
relaying motor signals, basic movements and postuur
hoe gaat motor actie in het brein
motor cortex <- basal ganglia
brainstem <- cerebellum
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local circuit neurons and lower motor neurons
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sensory input skeleton
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dus wat beinvloedt de motor cortex
basal ganglia
dus wat beinvloed de brainstem
cerebellum
spinal cord tov motor action
direct activation of single muscle fibers
reflex organisation
do lower motor neurons in grey matter of spinal cord and brainstem directly innervate muscles
yes (some are simple neuron contractions, meaning no delay)
wat doen local circuit neurons
they connect sensory information to the motor neurons directly -> reflexes
what kind of movements does the spinal cord influence
rythmic movements (walking, swimming, cat: swing and stance, kan dit ook met alleen zijn spinal cord zonder brain)
motor invariance + begrip dat hierbij hoort
produce the same motor actions with different body parts.
(complex movements preserve distinctive features (shape style) even when performed by different muscle groups
motor programs zijn dus…
commands that specify a sequence of movement, independent of the actual muscle group carrying them out!
Supplementary Motor Area function
planning of sequences learned from memory (guitar playing)
premotor function
learning complex movements from sensory input/external cues (tijdens gitaarles). hier zit ook broca’s area bij voor speech
primary motor cortex M1
initiation of a single, but coordinated multijoint movement (bijvoorbeeld duwen van een deur)
activation of lower structures
posterior parietal cortex
location-based movement (grasping, reaching) -> keys or scissors
descending pathway from M1
upper motor neurons in M1 - medullary pyramid - cross the midline at the caudal end of the medulla - lateral corticospinal tract in spinal cord - grey matter of the cord and brain stem
only a little bit of the motor neurons does not cross
oke
neurons for facial expressions branch off in the …
brainstem
which cortical regions have topographical maps
supplementary motor area SMA, premotor, M1, the basal ganglia, and specific parts of the thalamus, and the cerebellum
what does M1 not do?
it does not activate individual muscles directly. but it sends motor programs downwards, to create complex movements
what is the specific function of motor neurons in M1
they fire to a subset of movements (bv alle push movements) and code the direction of these movements
wat hangt samen met de strenght of the movement
the neuron firing rates.
dus zit er een delay tussen M1 neurons en de movement?
ja, M1 neurons fire well before the movement occurs.
hoe zit dit bij de FEF en SC?
ook die firen veel eerder dan dat je eye movements ziet
FEF naam
frontal eye fields
SC naam
superior colliculi
dus wat zijn de upper motor systems
M1, FEF, SC -> define what to do and how to do it.
wat zie je in een tuning curve
dat elke neuron een PREFFERED motor action heeft waarop je maximale activatie ziet. however, other directions also produce activity, but lower.
population vector
de richting waarin de neuronen gemiddeld naar toe firen. (= population coding)
the neurons DO NOT only code for a specific direction! they do have preferred ones.
oke
When monkeys are cued to reach towards a target but forced to delay
movement initiation: Anticipatory activity in premotor cortex reflecting
the intention to move.
oke
waar begint planning related movement het eerste
in premotor cortex, dan pas na M1
waar kan je de intention to move eerst zien voordat de movement wordt uitgevoerd
premotor, SMA, parietal, prefrontal cortex
readiness potential is..
je ziet dat de firing heel erg omhoog gaat voordat de movement wordt uitgevoerd -> accumulation of evidence
anosognosia
loss of awareness of one’s inability to move intentionally (je denkt dat je nog kan bewegen, maar dat kan niet). bij damage to premotor cortex and M1
Libet
role of awareness in motor planning:
there is activation in the brain 1000 ms before the movement,
and the urge to act occurs 200 ms before the movement.
Libet met letters experiment
10 seconden voor de urge to move is er al activation in the frontal en parietal cortex.
coherent motion task
aangeven naar welke kant de meeste puntjes gaan.
hard - low coherence - niet duidelijk
easy - high coherence - bijna alle dots gaan in dezelfde reactie
Monkeys have activation in the posterior parietal cortex PCC, FEF, supplementary eye fields, dorsolateral prefrontal cortex, and even superior colliculi, before they move.
–> evidence accumulation of sensory evidence for a movement.
Microstimulation in FEF during evidence
accumulation (before response) evokes eye
movements (up/down) that are biased by the
presented motion direction (up/down)
This bias is much stronger with high coherence →
Planned eye movement is “leaking through” when
the structure is activated by microstimulation
dus high coherence is more bias in FEF!
high motivation for the task is…
more activity in posterior parietal cortex
SMA is internally/externally driven
internally (from memory, what you learned). Het kan ook soms door visual cues die action guiden.
premotor cortex is internally/externally driven
externally driven, werkt met cues -> able to guide movement sequences based on sensory cues.
damage SMA
geen movements van memory terughalen, maar wel movements uitvoeren gebaseerd op sensory information.
damage premotor cortex
geen movements kunnen uitvoeren op basis van sensory cues, maar wel dingen van memory kunnen halen.
welk gedeelte van het brein voor location based movements (kopje koffie pakken)
posterior parietal cortex
waarom is de PPC de goede plek voor location based movements
omdat je input vanaf beiden ogen nodig hebt, alle muscles, en body posture etc.
patient DK, damage in visual region LO
cannot perceptually match and does not know what the object is, but can put the object in the slot. = visual agnosia
patient VK, damage in posterior parietal cortex + hoe heet het
cannot put the object in the slot, but does know what it is and what its function is. = optic ataxia.
ventral stream
what -> object recognition
dorsal stream
where/how -> using objects
welke mensen kunnen niet goed meer graspen en reachen, en hoe heet dit?
optic ataxia -> damage in PPC
apraxia
inability to execute voluntary movements, especially complex movements (wel motivation and physical ability to do so)
ideomotor apraxia
inability to perform a learned action, follow verbal instructions or imitate someone.
ideational apraxia
inability to use objects in their proper order
verbal apraxia
difficulty producing speech
which areas are damaged in apraxia
parietal and premotor cortex, mainly left hemisphere
basal ganglia function
they inhibit most motor actions, but when they select an action they start/gate this one. therefore they start and stop actions.
welk gedeelte van de basal ganglia inhibeert wat
globus pallidus + substantia nigra inhiberen de thalamus en subthalamic nucleus
wat gebeurt er bij activation van basal ganglia
striatum (caudate en putamen) inhibteert de globus pallidus en substantia nigra –> inhiberen de thalamus niet meer –> thalamus kan de cortex activeren voor movement.
balans tussen excitation en inhibition van basal ganglia leidt tot …
het coordineren van movement
release van basal ganglia inhibition leidt ook tot..
eye movements!
- Neurons in caudate nucleus fire just
before eye movement initiation - Immediately after, neurons in substantia
nigra pars reticulata (analogue of
globus pallidus output for eye
movements) cease firing - Resulting in burst of action potentials in
superior colliculus → horizontal eye
movement
task met monkey is belangrijk, misschien nog opzoeken
oke
direct vs indirect pathways in basal ganglia
direct: activation/gating of motor responses.
indirect: inhibition of motor responses
parkinson waar damage?
direct pathway (kan niet goed bewegen)
huntington en chorea waar damage
indirect pathway (te veel bewegen)
wat zijn nog meer functies van de basal ganglia
motor, emotion, cognitive, motivational processes (vormen loop met cortex)
hoeveel % van neuronen in cerebellum
80
main function cerebellum
error correction, smoothening of movements
vestibulocerebellum
balance and eyemovements
spinocerebellum
smoothing movements on the fly (net als gewone spine!)
cerebrocerebellum
planning, timing, attention, speech, learning, working memory
goals and planning of sequences of movement door..
SMA, premotor, prefrontal
activation of the body is more anterior/posterior
posterior
planning of movement and activating muscles
M1
basal ganglia
selecting and inhibiting motor actions, simple learning
cerebellum
adjusting and smoothing ongoing movements
brainstem
relaying motor signals and adjusting posture
spinal cord
direct activation of single muscles and reflexes
monkey study Libet
forced to delay movement initiation (ze mochten nog niet gelijk bewegen, wait in order to get a reward due to conditioning) -> anticipatory activity in the premotor cortex. we show readiness potential in EEG (local field potential) –> evidence accumulation.
anticipatory activity in premotor cortex
readiness potential in EEG
evidence accumulation
anosognosia (wat is het en waar damage)
loss of awareness of one’s inability to move intentionally, damage to SMA + M1
waar zie je readiness potential in humans
premotor, SMA, prefrontal, parietal cortex.
libet
they had to tell the researcher when they decided to move -> brain prepares the action a considerable period before the participant becomes aware of the intention.
optic ataxia
damage PPC -> cannot put object in slot
visual agnosia
damage visual area -> does not know what object is
