Cerebellum

Question 1

4 Functions (and associated circuits) of the cerebellum

Answer 1

Planning movements
Afferents from premotor/supplementary motor ctx (contra)
Efferents to the thalamus, to cortex

Limb and postural adjustments
Afferents from spinocerebellar tracts and motor ctx
Efferents to the

Equilibrium and eye movements

Motor Learning
Afferents from CN VIII, inferior olivary nucleus
Efferents to reticular formation, cranial nerve nuclei controlling extraocular muscles

Question 2

cerebellar lobes defined by fissures and longitutdinal zones

Answer 2

Vermis, paravermis, and lateral zone

anterior and posterior lobes plus the flocculonodular lobe (very ancient)

Question 3

Cerebellum is also defined by evolutionary emergence and function

Answer 3

vestibulocerebellum– make sure saccades go to the right spot, also sense of equilibrium.

spinocerebellom

cerebrocerebellum- neocerebellum, newest part. Do our motor planning and difficult coordination. Higher order stuff, comparing things.

Question 4

3 Cerebellar peduncles attach cerebellum to brainstem

Answer 4

Inferior: (aka restiform +juxtarestiform body) Ipsilateral info from vestibulocerebllar and spinocerebellar tracts as well as olivocerebellar
ALSO efferents to vestibular nuclei

Middle: (aka brachium pontis) Contralateral cortical input “cortico-ponto-cerebellar”

	  - synapse in pontine nuclei
		- Part of “basis pontis”

Superior: (aka brachium conjuctivum) contralateral info from ventral spinocerebellar tracts and sends efferent info to contralateral red nucleus and thalamus (primarily VL nucleus)
Major output pathway of the
cerebellum

Question 5

all fibers entering the cerebellum are called

Answer 5

mossy. they synapse on granule–> parallel–> deep

Question 6

cerebellum has 3 layers

Answer 6

graular layer- has granule cells (synaps between mossy and granule happens here) plus golgi type 2 cells (circuit modifier)

purkinje cell layer contains purkinje cell bodies as well as basket cells (circuit modifier)

molecular layer– synapse bewteen parallel fibers and the dendrites of the purkinje cell. Also has stellate cells (another circuit modifier)

Question 7

Fractured somatotopy exists in the cerebellum due to

Answer 7

the arrangement of mixed input connectivity

Question 8

Types of cells found in the cerebellum

Answer 8

Granule cells
Parallel fibers

Purkinje cells
2 targets (mostly to DCN, some directly to vestibular nuclei)

Stellate cells
Input from parallel fibers, inhibit Purkinje cells

Basket cells
Local inhibitory interneurons on Purkinje cells

Golgi II cells
Input from parallel fibers, inhibit granule cells (negative feedback)

Question 9

Layers of the cerebellum

Answer 9

Molecular layer
Parallel fibers, Purkinje dendrites, stellate cells

Purkinje cell layer
Cell bodies of purkinje cells, basket cells

Granule cell layer
Densely populated layer containing granule cells, cell bodies of golgi cells

Question 10

The basic cerebellar circuitry is defined by GABA and glutamate

Answer 10

The circuit allows for the comparison of ongoing movement and sensory feedback derived from it

Question 11

The inferior olivary nucleus provides

Answer 11

important, tonic input to cerebellum

Inferior olive sends contralateral projections to cerebellum
Olivary neurons use electrical synapses/gap junctions
OLIVOCEREBELLAR TRACT
Inferior cerebellar peduncle
Climbing fibers
Tonic oscillations for complex activity
Necessary for motor learning
(muscle memory will die if you lose the olivary nucleus)

Question 12

Deep cerebellar nuclei are organized in columns

Answer 12

Dentate

• Most fibers in superior peduncle originate from here
• Most lateral cerebellar nucleus

Interposed (globose and emboliform)

Fastigial
-Most medial cerebellar nucleus

Question 13

Longitudinal organization of cerebellar ins and outs: Vestibular

Answer 13

Input through inferior peduncle as mossy fibers
These can be axons direct from Scarpa’s ganglia or after first synapse in vestibular nuclei
To flocculonodular lobe (hence “vestibulocerebellum”)
To Fastigial nucleus
Output to vestibular nuclei and reticular formation
Affects eye movements and equilibrium

Question 14

longitudinal organization of cerebellar ins and outs: trunk and limb postural adjustments

Answer 14

Input through inferior peduncle as mossy fibers
From spinocerebellar tracts (hence “spinocerebellum”)
Input to vermis, paravermal region
To Fastigial nucleus and interposed nuclei
Output to vestibular nuclei and reticular formation, red nucleus (interposed)
Walking, posture, some eye movements

Question 15

longitudinal organization of cerebellar ins and outs: cortical input, “processed” and coordinated info

Answer 15

Input through middle peduncle as mossy fibers
Cerebro-ponto-cerebellar (hence “cerebrocerebellum”)
To lateral zones and intermediate zones
To dentate and interposed nuclei
Output to red nucleus and inferior olivary nucleus, also to the VA/VL Thalamus (dentate)
Affects planning and programming of voluntary movements, motor learning

Question 16

spinocerebellar ataxias

Answer 16

intention tremor– can do it without shaking

dysmetria– metrics are off; muscle movements don’t match up with the measurements

dysdiadochokinesia- quick repeated movement troubles

Question 17

Anterior lobe syndrome

Answer 17

Malnutrition from chronic alcoholism
Predominantly around the vermis
Legs most strongly affected (spinocerebellum)

Broad, staggering gate, dysarthria (difficulty speaking– hiccuping in the middle of the word; any kind of cerebellar syndrom at advanced stages) AND ataxia

Question 18

Neocerebellar syndrome

Answer 18

More common in upper limbs
Hypotonia
Ataxia
Dysmetria
Overshooting and undershooting targets
Intention tremor
Dysdiadochokinesia
Rapid, alternating movements impaired

Question 19

localizing cerebellar lesions

Answer 19

limb ataxia, hypotonia, dysdiadochokinesia– lateral lobe

disturbed equilibrium, truncal ataxia, nystagmus– flocculonodular lobe

gait ataxia, inability to do tandem walking- anterior lobe

When lesions are particularly diffuse or severe, may also show dysarthria