Cerebellum/Basal Ganglia/Motor Cortices Flashcards Preview

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Flashcards in Cerebellum/Basal Ganglia/Motor Cortices Deck (56)
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1

three main functions of cerebellum

1. monitor and adjust ongoing motor behavior (precision and smoothness is poor without the cerebellum)
2. contribute to motor learning
3. participate in cognitive functions

2

four types of experiments to ID cerebellum function

1. lesions give problems with coordination and balance, problems with learning new motor skills, and problems with some "higher functions"
2. tract-tracing
3. neural recording. Cerebellar neurons change firing frequency when limb is moved or you touch the skin
4. fMRI, PET

3

three parts of cerebellar cortex

cerebrocerebellum
spinocerebellum (the part receive sensory inputs, somatotopic mapping)
vestibulocerebellum

4

three deep cerebellar nuclei

dentate nuclei
interposed nuclei
fastigial nuclei

5

three cerebellar peduncles

superior
middle
inferior

cerebellum talks to CNS through peduncles;
the lateral part of the cerebellar cortex communicate with dentate, the largest nuclei, and run in the middle pedunculi which receives axons from, and distribute axons to the cerebral cortex

6

define: vermis, additional name?

midline of cerebellum
spinocerebellum

7

define: flocculus, additional name?

bottom part of cerebellum
vestibulocerebellum (balance)

8

define: Foli, additional name?

folds of cerebellum
cerebrocerebellum

9

what are the inputs to the cerebellum?

1. cortical input (frontal + parietal cortex -> pontine nuclei)
2. vestibular nuclei
3. cuneate nucleus (spinal cord, medial lemniscal pathway)
4. non-sensory input: climbing fibers, exclusively arising from inferior olive

10

what are the outputs of the cerebellum?

via (large) deep cerebellar nuclei to cerebral cortex (via thalamus), spinal cord (through reticular formation), and center for eye control

one exception is fibers from flocculus go out of the cerebellum without contacting the deep cerebellar nuclei

11

input from cerebral cortex goes to_in cerebellum
input from pons goes to_ in cerebellum
input from vestibular organs goes to_ in cerebellum
input from spinal cord goes to_in cerebellum
(not in the lecture)

cerebrocerebellum
cerebrocerebellum and spinocerebellum
vestibulocerebellum
spinocerebellum, vermis

12

cerebrocerebellum outputs to_
spinocerebellum projects to_
vermis projects to_
(not in the lecture)

dentate nucleus-> thalamus
interposed nucleus
fastigial nucleus -> reticular formation

13

what are the 3 layers of cerebellar cortex?

molecular, purkinje, granular

together they form gray matter, white matter is myelinated axons

14

purkinje cell (output)

1.inhibitory cell in cerebellum that inhibits deep cerebellar nuclear cell
2. only purkinje cell project out from the cerebellar cortex to the deep cerebellar nuclei
3. the dendritic tree of Purkinje cells lie in one place, perpendicular to the parallel fibers

15

climbing fiber (input)

1. excitatory cell in cerebellum that originates in inferior olive
2. STRONGly excites multiple purkinje cell, each PC receives only one climbing fiber
3. all from inferior olivary nucleus, connect exclusively to Purkinje cells

16

mossy fiber (input)

1. originates from many different sources. several mossy fibers synapse to a single granule cell
2. excitatory

17

granule cell

1. neuron within cerebellum. Receives excitatory input from mossy fibers. Bifurcates into parallel fiber
2. a parallel fiber can synapse only on a specific purkinje cell, but one purkinje cell to five fibers
3. forms weak excitatory synapse onto purkinje cell, thus many granule celle are needed to fire a Purkinje cell
4. the only excitatory type in cerebellar cortex, converging on purkinje cell
5. thre are no excitatory synapses onto other excitatory cells, preventing information and excitation from spreading

18

basket cell

inhibits purkinje cell in cerebellum, may regulate precise time output

19

where do the inputs to the basal ganglia come from?

1. limb cortex
2. motor cortex
3. associative cortex

20

what are the outputs of the basal ganglia and what are their functions?

1. superior colliculus: head and eye mvt
2. thalamus: motor control
3. pedunculo-pontine nucleus: spinal cord processing + locomotion

21

striatum
inputs, kinds of cells in it. DIfference between primates and rodent?

1. dorsal: caudate nucleus and putamen
ventral: accumbens
2. glutamatergic input from all areas of cortex + thalamus
3. dopaminergic input from substantia nigra compacta
4. intrinsic connections: gabaergic and cholingergic
5. medium sized spiny neurons and striatal interneurons

In rodents, caudate and putamen are a single structure. In primates, they are separated by internal capsule.

22

striatal projection cells: MSNs

1. 90% of cells in striatum
2. GABAergic (inhibitory)
3. main output of striatum
4. slow activity at rest but active during movement/learning
5. MSNs considered "phasically active neurons"

23

striatal interneurons

1. 10% of cells in striatum
2. cholinergic: tonically active neurons in primates
3. GABAergic

24

what kind of terminals are highly expressed in striatum?

dopamine (DOPA terminals)

spines of spiny neuron are the main sites of functional interactions between glut and dopaminergic inputs to the striatum

25

what are the three differences between the direct and indirect pathway?

indirect:
uses enkephalins
expresses D2 receptors
MSN project to GPe -> STN -> GPi/SNr

direct:
use substance P and dynorphins
express D1 receptors
MSN projects to GPi/SNr directly

26

GPe
Name inputs, outputs and comparative anatomy
characteristic of GPe cells

1. inputs: STN (glut), striatum (GABAergic), intrinsic (local) collaterals (GABAergic)
2. outputs: STN (GABAergic), GPi/SNr
3. called globus pallidus in rodents

1.highly GABAergic
2. glut inputs are less abundant and distal
3. despite the abundant GABAergic innervation, GPe neurons present tonic high freq discharge
(due to GPe neuron intrinsic activity & lots of the GABA innervations are silent)

27

sub-thalamic nucleus (STN)
overall, inputs, outputs

1. mostly glutamatergic (the only excitatory neurons in basal ganglia). Strongly excited by cortex. Lots of spontaneous activity
2. inputs: glutamatergic: cortex and thalamus GABAergic: GPe
3. outputs: GPe (+), GPi/SNr (+)
4. reciprocal connection with GPe and STN - pacemaker activity

28

GPi/SNr (inner part)
inputs, outputs, how does it fire? what is it called in rodents? function?

1. inputs: STN(glut), striatum + GPe (GABA)
2. outputs: thalamus, brainstem
3. fires at high freq
4. in rodents it is called entopeduncular nucleus (EPN)
5. function: have GABAergic projections to thalamus. Strong inhibition of thalamo-cortical cells

29

SNc (outer part)
inputs, outputs, function

1. inputs: STN(+), PPN (+), striatum(-), SNr(-)
2. outputs: striatum (excites D1/direct, inhibits D2/indirect), STN, GPe/GPi/SNr
3. function: predict reward. i.e. fire when reward occurs and after conditioning fire when they think reward will occur. If no reward occurs, their firing is depressed
4. SNc dopaminergic neuron
slow spontaneous activity;
phase activation in response to reward;
after conditioning, response to the presentation of the reward-signaling stimulus

30

how does direct pathway of basal ganglia facilitate movement?

cortex excites D1 in striatum > D1 inhibits GPi/SNr > GPi/SNr weaken inhibition of thalamus > motor activity strengthened