Motor System 3: Cerebellum Flashcards
What, broadly, is the role of the cerebellum?
It compares the intention of a motion with the outcome, and sends out predictive and corrective signals.
Does the cerebellum have direct output to the muscles?
No.
What do lesions to the cerebellum broadly cause / not cause? (3 things)
Loss of spatial accuracy, coordination (ataxia)
Impairment of muscle tone and balance
Do NOT cause sensory loss or loss of strength
What are the folia of the cerebellum?
Thin gyri…
Is there a midline groove (or other structure) that divides the cerebellum into two halves?
No.
What function do the (deep) cerebellar nuclei serve?
Sources of output from the cerebellum.
What are the 3 lobes of the cerebellum? What fissures divide them?
Anterior, posterior, and flocculonodular lobes.
Primary fissure divides anterior from posterior lobe.
Posterolateral fissure divides posterior from flocculonodular lobe.
What characteristic defines the functional regions of the cerebellum?
Source of inputs.
What are the 2 systems of input to the cerebellum?
Climbing fiber system and the mossy-fiber, parallel-fiber system.
Where do climbing fibers come from? Where do they travel in the brain stem? Where do they go in the cerebellum? Type of synapse?
Origin: Inferior olivary nucleus
Path: Cross midline, travels up inferior cerebellar peduncle (ICP)
Destination: Purkinje cells (wrap all around their dendrites)
Synapse: Excitatory glutamatergic
Where do mossy fibers come from? Where do they travel in the brain stem? Where do they go in the cerebellum? Type of synapse?
Origin: “All sensory modalities” (including sensory nuclei)
Path: Up the inferior cerebellar peduncle (ICP)
Destination: Granular cells
Synapse type: Excitatory glutamatergic
How do the axons of granular cells run relative to the axis of the folia?
Parallel.
How do axons of Perkinje cells run relative to the axis of the folia?
Peripendicular - straight down (normal, if you will, to the surface) headed toward the deep cerebellar nuclei
What’s the destination of Perkinje cell axons? Are the excitatory or inhibitory?
Deep cerebellar nuclei. Inhibitory.
What are the 3 functional divisions of the cerebellum?
The vesibulocerebellum, the spinocerebellum, and the cerebrocerebellum.
Where do most of the vestibular inputs go in the cerebellum?
The flocculonodular lobe (a.k.a. the vestibulocerebellum)
What anatomical regions constitute the spinocerebellum? What information does it receive?
Vermis and adjacent swathes of the hemispheres.
Receives proprioception from spinocerebellar tracts etc.
What anatomical regions constitute the cerebrocerebellum? From where does it receive inputs, and how does that info get there?
Lateral parts of the cerebellar hemispheres. Gets info from the cortex (esp. about the intended motion). Cerebral peduncles -> pontine nuclei -> middle cerebellar peduncles -> cerebrocerebellum.
What are “deep cerebellar nuclei” to which the vestibulocerebellum sends efferent information? Where are they?
Vestibular nuclei. They’re outside the cerebellum, in the brainstem.
What are “deep cerebellar nuclei” to which the spinocerebellum sends efferent information? Where are they? Where do the nuclei send stuff?
Fastigial nuclei - in the vermis -> medial descending systems
Interposed nuclei - in the medial hemispheres -> lateral descending sytems
What are “deep cerebellar nuclei” to which the cerebrocerebellum sends efferent information? Where are they? Where do the nuclei send stuff?
Dentate nuclei, at the medial edge of the cerebrocerebellum. Sends info to motor and premotor cortices.
Do the dentate nuclei send information directly to the motor and premotor cortices? What specific path is taken?
No, information is relayed through the ventral lateral (VL) nucleus of thalamus. (he also mentioned the ventral anterior (VA) nucleus… but..)
How does the somatotopic map look in the cerebellum? Is population encoding more or less important here than in the motor cortex?
Axial musculature is in the vermis, limbs ipsilaterally in the proximal (medial) hemispheres. Population encoding is more important here (it’s even less like a switchboard).
Without an intact cerebellum, what happens in a bicep stretch reflex? Does the same thing happen in voluntary movements?
Reflex overshoots resting position -> stretch reflex in opposite direction -> oscillations. Yes, this happens with voluntary movements too.
Might you have an easier time karate-chopping through a piece of wood with a lesioned cerebellum? Why or why not?
Probably. Because the cerebellum makes your arm brake before reaching the target location. (Yeah, I’m making this up. For those of you who haven’t fantasized about karate-chopping through things, apparently it’s all about aiming past the target.)
If you had to pick between feedforward and feedback, which is more lost in a lesion to the cerebellum?
Feedforward is lost. Intact feedback causes oscillations.
Is the cerebrocerebellum involved in cognitive tasks? Is it important for the memory of learned movements?
Yes, and yes.
