Cerebellum Flashcards
what two structures surround the cerebellum
the midbrain and brainstem
what is the purpose of the cerebellum
-the cerebellum coordinates motion helps us distinguish between important and unimportant stimuli and coordinate movements
spinocerebellum
-middle of the cerebellum, contains the vermis plus two intermendiate areas
-part of the cerebellum which receives info from the spinal cord via the Dorsal node of Clark
cerebrocerebellum
-large lateral hemispheres on either side of the paravermis regions of the spinocerebellum
-receives information from the thalamus via the pons
vestibulocerebellum
-bow tie shaped part of the cerebellum containing the nodulus and the floculus
-relays information from the vestibular system(relating to balance) via the vestibular nuclei
types of information that the cerebellum receives
-somatosensory (touch)
-visual
-auditory
-vestibular
-proprioceptive
which cortex projects to the cerebellum most
-the cerebral cortex (via the pons)
how is information from the vestibular pathway integrated into the cerebellum
information travels from the vestibular nuclei in the medulla to the vestibulocerebellum via the inferior cerebellar peduncle
middle cerebellar peduncle
transports information from the pons to the cerebrocerebellum
-aids in the integration of information from the frontal-motor/parietal lobes to the cerebellum
mossy fibers
-include the pontine nuclei(middle peduncle), vestibular nuclei, and dorsal nuclei of clarke(inferior peduncle)
-provide consistent ongoing information to the cerebellum during movement
type of information relayed through the mossy fibers of the inferior peduncle
-sensory information via medulla, cranial viii, and spinal cord
granule cells
-types of cells which mossy fibers synapse on
-send parallel inputs to the purkinje fibers (send divergent information)
climbing fibers
-different input to the cerebellum
-originate from the inferior olive (inferior peduncle)
-direct synapse to purkinje cells, one climbing fiber to one purkinje cell
climbing fibers
-different input to the cerebellum
-originate from the inferior olive (inferior peduncle)
-direct synapse to purkinje cells, one climbing fiber to one purkinje cell
-do not go through granule cells first
compare the resistance for inputs via mossy fibers and climbing fibers
-much less resistance for moss fibers which synapse via granule cells through parallel pathways
-mossy fiber info may travel faster because of this
action potential spikes of mossy fibers
simple (due to parallel paths and constant current flow)??
action potential spikes of climbing fibers
complex spikes (due to single paths: less distance for action potentials to travel to reach the purkinje soma causes summation of action potentials instead of distinct ones)
understand why climbing=complex and parallel=simple more
deep cerebeller nuclei
-receive collateral information from the mossy or climbing fibers and relay it back to the thalamus
cerebellar outputs
purkinje cells project to the deep cerebeller nuclei
-purkinje cells of different parts of the cerebellum are associated with different deep cerebeller nuclei
total cerebrocellular pathway
-motorfrontal/parietal cortex to thalamus to pontine nuclei to cerebrocerebellum via medium peduncles to granule cells via mossy fibers to purkinje cells via parallel pathways AND to deep cerebellar nuclei via collateral branches
-from deep cerebellar nuclei (dentate nucleus) to premotor cortex upper motor neuron pathway
dentate pathway
nuclei in the deep cerebellum which cerebrocerebellum purkinje neurons project to
interposed and fastigial nuclei
receive purkinje inputs from the cerebrospinal purkinje neurons
what kind of inputs are climbing and mossy fibers
excitatory
where in the deep cerebeller nuclei do cerebrocerebellum purkinje cells synapse
dentate nuclei
where in the deep cerebeller nuclei do spinocerebellum purkinje cells synapse
interposed and fastigial nuclei
where do vestibulocerebellum purkinje cells synapse
back to the vestibular nuclei
where is the overall cerebellar output of the cerebrocerebellum
upper motor neuron pathways to the premotor cortex
where is the overall cerebellar output of the vestibulocerebellum
back to the lower motor neurons part of the vestibular system (controlling balance and vestibuloocular regulation)
where is the overall cerebellar output of the spinocerebellum
upper motor neuron pathway to the motor cortex and brainstem (executing motor functions)
how does the cerebellum integrate inputs from mossy and climbing fibers
-the mossy fibers tell you about what is happening during movement
-the climbing fibers tell you if this needs to be changed
-this circuit relates to negative learning
what is the climbing fiber input to the dcn when negative learning is not taking place
excitatory but decreasing (will be highest at first)
how does climbing fiber input to the dcn change when learning is taking place
excitatory input increases to the purkinje neuron
what goes through the superior peduncle
axons from the dcn back to the cortex
procedural learning
-uses different reflexes which integrate sensory and motor information
-you are learning the which reflexes help you not fall off the bike
-procedural=learning from experience
how are simple purkinje neuron spikes mediated at slower intervals
AMPA receptors establish a certain refractory period when you have glutamate which stays in the synapse
do climbing fibers have AMPA/NMDA receptors at their synapses?
eye example: which fibers are increasing firing to signal the air released onto the eye
the climbing fibers via the inferior olive because these are initiating cerebeller learning, the purkinje neuron will receive complex spikes at this time
eye example: which fibers are released to signal the other conditions of what is happening in the body
the mossy fibers (specifically the ones projecting from the cerebeller cortex) are firing inputs about the tone, vestibular inputs signal about balance being thrown off, spinal inputs are signaling about which reflexes occured, and these are all conveyed to the purkinje neuron excitatory inputs
describe the initial firing frequencies when learning is initiated
-you have peak mossy fiber inputs signaling change in the body and the greatest rate of increase of climbing fiber firing
describe the firing frequencies when behavior begins to change
complex spiking has reached its peak, and simple spiking via mossy fibers decreases. Complex spiking tells us there is still something wrong with our body’s movement and response. Moss fibers decrease as a result because “unhelpful” movements are now stopping
what happens after conditioning has occurred
all of the “unhelpful” mossy fiber firing has stopped and climbing fiber firing has come back to its original levels. This is because there is no longer motor error because the response has been fine tuned
why doesn’t mossy fiber fall to zero again after conditioning
because some mossy fiber firing must be occurring in order to retain the conditioned response to the stimuli
what is the relationship between mossy fibers and climbing fibers
climbing fibers modulate the effectiveness of mossy fiber synapses onto the purkinje cell
how do climbing fibers modulate the effectiveness of mossy fiber inputs
climbing fibers which fire at the same time as mossy fibers will deem the mossy input “unhelpful” because the input of the climbing fiber will still overpower whatever the mossy fiber is trying to convey
how does the purkinje cell modulate its response during learning
long term depression: internalization of the AMPA receptors on the parallel granule/mossy synapses which are not usefull and continually lead to motor error
Marr Albus theory of motor learning
-indicates that long term depression, synaptic plasticity, etc. only occurs when there is a simultaneous synapse on the purkinje fiber by the mossy and climbing fibers
-AMPA internalization is not a long term thing and can easily change
how does AMPA receptor internalization occur when you have dual synaptic inputs
secondary messenger cascade results in AMPA internalization at the parallel fiber synapse
are dcn inhibited by default or are they neutral? are dcn nuclei tonically or transiently firing when they are active
they are neutral by default and dcn are not tonically active
