Corticospinal and Cerebellar Systems

Question 1

What are the 2 streams of descending information to the spinal cord?

Answer 1

Ventromedial group

Dorsolateral group

Question 2

Which pathways make up the ventromedial group of spinal cord inputs?

Answer 2

Reticulospinal
Tectospinal
Vestibulospinal

Question 3

Which pathways make up the dorsolateral group of spinal cord inputs?

Answer 3

Corticospinal

Rubrospinal

Question 4

What do medial MNs control?

Answer 4

Axial muscles - balance and posture

Question 5

What do lateral MNs control?

Answer 5

Distal muscles - fine movements

Question 6

What is a corticomotoneuronal cell?

Answer 6

Cortical neuron that projects directly to MN

Question 7

What are the component of the motor cortex?

Answer 7

Primary motor cortex (M1)
Supplementary motor area (SMA)
Premotor area (PM)

Question 8

Which aspects of muscle force do M1 cortical neurons code for?

Answer 8

Direction

Amplitude

Question 9

What is the evidence against M1 cortical neurons as controllers and how could this be dismissed?

Answer 9

Fire during range of movement directions - bell-shaped directional tuning curve - not precise enough
Direction could be encoded by cooperation of cells with overlapping tuning curves - M1 neurons encode direction as population

Question 10

What is the role of Purkinje cells in the cerebellar cortex?

Answer 10

Select relevant information for movement control from inputs (from granule cells)

Question 11

Which NT do cerebellar Purkinje cells release?

Answer 11

GABA

Question 12

Where do cerebellar Purkinje cells receive inputs from?

Answer 12

Granule cells

Climbing fibres

Question 13

Where do cerebellar granule cells receive inputs from?

Answer 13

Mossy fibres

Question 14

Where do cerebellar mossy fibres receive inputs from?

Answer 14

Most sensory modalities
Motor efference copy
Vestibular

Question 15

Where do climbing fibres originate from?

Answer 15

Medullary olive

Question 16

What is the role of climbing fibres in the cerebellar cortex?

Answer 16

Fires when sensory feedback different to predicted - signals error

Question 17

Where do Purkinje cells in each cerebellar hemisphere project to?

Answer 17

Ipsilateral cerebellar nuclei

Question 18

Where do interneurons in the cerebellar nuclei project to?

Answer 18

Inferior olive - same region climbing fibres for that zone originated from

Question 19

What are the circuit loops in the cerebellum called?

Answer 19

Olivo-cortico-nuclear modules

Question 20

What are the ascending cerebellar outputs?

Answer 20

Major - from lateral cerebellum - to thalamus, motor cortex

Minor - from intermediate cerebellum - to red nucleus

Question 21

What are the descending cerebellar outputs?

Answer 21

Major - from medial cerebellum - to vestibular nuclei

Question 22

What does the flocculonodular lobe control?

Answer 22

Balance and eye movements

Question 23

What do the vermis and pars intermedia control?

Answer 23

Adjust ongoing whole-body movements

Question 24

What do the cerebellar hemispheres control?

Answer 24

Coordinate planning of limb movements

Question 25

What is the effect of conjuctive activation of climbing fibre and parallel fibre inputs to Purkinje cells?

Answer 25

LTD of parallel fibre-Purkinje cell synapses

Reduced Purkinje cell response to parallel fibre stimulation

Question 26

Explain the mechanism of cerebellar LTD

Answer 26

Climbing fibre input depolarises Purkinje cell
VGCCs open in Purkinje cell - Ca2+ influx
Glutamate release by parallel fibre - binds to mGluRs on Purkinje cell - increases PKC
Ca2+ activates PKC - phosphorylates active AMPARs in parallel fibre-Purkinje cell synapse - decreases AMPAR conductivity
LTD