Cerebellum - Lecture 5

Question 1

What is the vermis (cerebellum)?

Answer 1

The vermis is a worm like band that runs down the midline connecting the two hemispheres of the cerebellum

Question 2

What is the folia (cerebellum)?

Answer 2

The area around the vermis. Has folds that increase the surface area. Allows for a greater number of neurons to be located within the cortical layers

Question 3

What/where is the cerebrocerebellum?

Answer 3

From outside edge to in line with the floculus. Receives input directly from the cerebral cortex. Concerned with regulation of highly skilled movement

Question 4

What/where is the spinocerebellum?

Answer 4

At the tip of the cerebellum. The only part that receives direct input from the spinal cord. Concerned with regulating movement of distal/proximal muscles as well as certain eye movements

Question 5

What/where is the vestibulocerebellum?

Answer 5

Bottom part of cerebellum contains nodulus and flocculus. Receives input from the vestibular nuclei in the brainstem. Primarily concerned with the vestibular-ocular reflex and regulation of balance

Question 6

Where is gray matter found in the cerebellum?

Answer 6

Found in the outer cortex and in the deep cerebellar nuclei within the white matter

Question 7

What are the 3 deep cerebellar nuclei?

Answer 7

Fastigial nucleus, interposed nuclei, dentate nucleus

Question 8

What does the superior cerebellar peduncle do?

Answer 8

Connects the deep cerebellar nuclei to the midbrain, diencephalon and cerebrum.
Consists mainly of motor fibres leaving for the brain

Question 9

What does the middle cerebellar peduncle do?

Answer 9

The largest peduncle, and connects the cerebellar hemispheres to the pons.
They consist of both motor and sensory tracts leading to the cerebellum

Question 10

What does the inferior cerebellar peduncle do?

Answer 10

Connects the cerebellar cortex to the medulla oblongata. Is the smallest and most complex peduncle.
Consists of both motor and sensory fibres; ascending and descending tracts from the spinal cord

Question 11

What are the cerebellar inputs (see diagram for reference)

Answer 11

Pons/Pontine nuclei (via middle cerebellar peduncle)

Red nucleus -> Inferior olive, spinal cord, vestibular nuclei (via inferior superior cerebellar peduncle)

Question 12

Discuss the cerebellar somatotopic maps??

Answer 12

Two maps of the body, one in the anterior lobe and one in the posterior lobe

Cerebrum concerned with contralateral representation
Cerebellum concerned with ipsilateral representation

Question 13

What are the 3 cerebellar output pathways?

Answer 13

Cerebrocerebellum -> dentate nucleus -> pre-motor cortex (motor planning)

Spinocerebellum -> interposed and fastigial nuclei -> motor cortex and brainstem (motor execution)

Vestibulocerebellum -> vestibular nuclei -> lower motor neurons in spinal cord and brainstem (balance and VOR)

Question 14

Describe the pathway from the cerebellar cortex to the primary and premotor cortex

Answer 14

Cerebellar cortex -> deep cerebellar nuclei (dentate/interposed) -> VL complex -> primary motor and premotor cortex

Nuclei to VL complex by superior cerebellar peduncle, up VL and can also go down to superior colliculus (see diagram)

Question 15

What is a purkinje cell?

Answer 15

Consists of a cell body and a huge dendritic tree that is perpendicular to the surface

The sole output of the cerebellar cortex

Question 16

What is a climbing fibre?

Answer 16

One of the two ways afferent information reaches the purkinje cells
Climbs up the efferent axon of the purnkinje cell and then clambers over the dendrites
Originates from the inferior olive in the brainstem

Question 17

What are mossy fibres?

Answer 17

Second type of afferent system to deliver information to the purkinje cells
Incoming fibres enter the lower levels of the cortex and branch go form large terminal structures - these synapse with granule which send axons to the surface where they bifurcate to form parallel fibres

Question 18

What are parallel fibres?

Answer 18

Thin linear axons that run perpendicular to the dendrites of the purkinje cells
Form side connections (contrasts to the climbing fibres) as each parallel fibre comes in contact with large numbers of purkinje cells

Question 19

How is the climbing fibres anatomy suited to its function?

Answer 19

Extraordinarily precise, allows for the integration of specific and real errors

Question 20

How is the anatomy of the mossy fibre influencing its function?

Answer 20

Non specific, allows for the association with of general patterns of activity (motor learning

Question 21

What are the two types of interneurons present in the cerebellum?

Answer 21

Basket cells - parallel fibres that inhibit the purkinje cells

Golgi cells - parallel fibres that inhibit granule cells, therefore acting at the input rather than the output

Question 22

What are some classical cerebellar impairments?

Answer 22

Ataxia

Asynergia - dysmetria, intention tremor, decomposition of movement, dyschiadokinosis, scanning speech

Impairment of execution

Hypotonia

Rebound

Question 23

What is ataxia?

Answer 23

Shaky and unsteady movements of body, and limbs lacking overall coordination

Question 24

What is asynergia?

Answer 24

Lack of coordination of all kinds of movement

Question 25

What is dysmetria?

Answer 25

The inability to place limb at correct location

Question 26

What is vestibular ocular reflex gain? Use example with minifying glasses.

Answer 26

In normal case, the head and the eyes move in a coordinated manner to keep image on the retina

When the VOR is out of register, the eyes move too far in relation to the image movement on the retina when the head moves

VOR gain reset occurs after a certain amount of time - the eyes now move smaller distances in relation to head movement to compensate