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Systems Neuroscience > Basal Ganglia and Cerebellum > Flashcards

Basal Ganglia and Cerebellum Flashcards

1
Q

T/F The basal ganglia and cerebellum directly influence lower motor neurons.

A

FALSE The basal ganglia and cerebellum do NOT directly influence lower motor neurons. They influence movement by regulating activity in upper motor neuron circuits.

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2
Q

Basal Ganglia

-most known for

A

Not ganglia
Definitely basal
*Most known for role in movement but functions not limited to movement

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3
Q

Parts of the Basal Ganglia

A

Striatum (aka corpus striatum): caudate and putamen

Pallidum: globus pallidus and substantia nigra (pars reticulata)

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4
Q

Pallidum:

-made up of ?

A

globus pallidus and substantia nigra (pars reticulata)
Main source of output from basal ganglia to other parts of brain
Where the medium spiny neurons send their axons

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5
Q

Striatum (aka corpus striatum):

-neurons

A
  • caudate and putamen
  • Main area of input
  • Contains medium spiny neurons with large dendritic trees***
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6
Q

caudate and putamen make up

A

make up the Striatum (part of the basal ganglia)

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7
Q

Caudate:

-where sends projects?

A

sends projections to the substantia nigra pars reticulata (and internal portion of globus pallidus)

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8
Q

Putamen:

-where sends projections

A

Putamen: sends projections to the external and internal globus pallidus

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9
Q

what areas of the basal ganglia are defs true basal ganglia structure

A
  • caudate, putamen, and globus pallidus ARE FOR SURE

Note: Not everyone agrees on which structures are a part of the basal ganglia or not. however they argree on the above

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10
Q

Input to Basal Ganglia

A

-mostly from cortex

  • Nearly all regions of the cortex send direct projections to the striatum
  • Therefore, the cortex is the largest source of input
  • Mostly from association areas and the temporal, insular, and cingulate cortices
  • Collectively refer to these pathways as the CORTICOSTRIATAL PATHWAY

*The cortical input to the caudate and putamen are NOT equal

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11
Q

*The cortical input to the caudate and putamen are NOT equal, explain

A
  • Caudate receives projections mostly from multimodal association cortices and motor areas in the frontal lobe that control eye movement
  • Putamen receives projections from the primary and secondary somatosensory cortices, extrastriate visual cortex, premotor and primary motor cortices, and auditory association areas
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12
Q

Multiple Parallel Pathways

A
  • to the caudate and the putamen

*The caudate and putamen receive different streams of information from different regions of the cortex
*This suggest that the corticostriatal pathway is composed of multiple parallel pathways and that the caudate and putamen have different functional roles
The output from the caudate and putamen is also segregated, which reinforces this idea
*Some of the projections to the basal ganglia are topographically mapped (visual and somatosensory) and some are overlapped (those from more interconnected or association regions)
There are rostrocaudal bands of cells that seem to be concerned with different parts of the body and the movement of that part

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13
Q

Striatum: Patch and Matrix

A

*If you look for acetylcholinesterase (inactivator of acetylcholine), you see that there is compartmental organization of the striatum
*Patch: lightly stained
Makes up less of the striatum
Receives most of input from the prefrontal cortex
Caudate patches project mostly to the substantia nigra pars compacta (dopaminergic cells)
*Matrix: densely stained
-Makes up the bulk of the striatum
-Receives input from most of the regions of the cortex
-Projects mostly to globus pallidus and substantia nigra pars reticulata

see slide 11

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14
Q

Substantia Nigra

-the parts

A

*Pars compacta- most of DA neurons are from here; projects to basal ganglia and cortex
These are the cells containing neuromelanin that you see when looking at the brain specimens

*Pars reticulata- where the dendrites go to get info; GABAergic interneurons; projects to basal ganglia

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15
Q

Pars reticulata

-projects to:

A
  • of the Substantia Nigra

* where the dendrites go to get info; GABAergic interneurons; projects to basal ganglia

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16
Q

Inputs to Striatum

A

information from the cortex:
or
From other inputs: from medium spiny neurons via axon collaterals, Local circuit interneurons in the striatum, Multiple brainstem nuclei, Midline and intralaminar nuclei of thalamus

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17
Q

explain how each medium spiny neuron can integrate the information from thousands of cortical cells

A

-inputs to striatum from the cortex

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18
Q

the other inputs, besides from the cortex to the striatum:

A

Local circuit interneurons in the striatum
Multiple brainstem nuclei (using biogenic amine neurotransmitters like histamine and serotonin)
Including the substantia nigra pars compacta (dopamine)
Midline and intralaminar nuclei of thalamus

Cortical and substantia nigra inputs synapse on the dendritic spines. Thalamic and local circuit synapses happen on the dendritic shaft or near the soma.
Better at modulating the activity that is induced or not by the cortical synapses

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19
Q

inputs to striatum from the cortex

A

Lots of glutamatergic input from corticocortical, corticothalamic, and corticospinal collaterals
Few contacts between each axon and each medium spiny neuron
One axon, however, makes contact with lots of medium spiny neurons and each medium spiny neuron receives input from lots of different axons
****Therefore, each medium spiny neuron can integrate the information from thousands of cortical cells

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20
Q

Nonspecific Nuclei

-probs involved in:

A

Many of the intralaminar nuclei and midline nuclei have diffuse projections to the cortex and have been termed “nonspecific”.
Project broadly to the cortex
Also project to more ‘nonspecific’ regions of the cortex
These nuclei are probably mostly involved in arousal and alertness.

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21
Q

Medium Spiny Neuron Activity

A

*Due to various Cell Neuro things (inward-rectifier potassium conductances), they rarely display spontaneous activity
*Almost always only activity right before and during movement
*Increase firing rate before movement (even by several seconds)
Putamen- discharge in anticipation of limb and trunk movements
Caudate- discharge in anticipation of eye movement
Some vary based on destination of movement
Overall, suggests that these cells encode the decision to move
Also fire again after a movement is complete
Usually another motor program will follow (reinstitution of stable posture)

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22
Q

_____ Neuron encode the decision to move

A

Medium Spiny Neuron
Due to various Cell Neuro things (inward-rectifier potassium conductances), they rarely display spontaneous activity
Almost always only activity right before and during movement
Involved in the planning process
Increase firing rate before movement (even by several seconds)
Putamen- discharge in anticipation of limb and trunk movements
Caudate- discharge in anticipation of eye movement
Some vary based on destination of movement
Overall, suggests that these cells encode the decision to move
Also fire again after a movement is complete
Usually another motor program will follow (reinstitution of stable posture)

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23
Q

Outflow of the basal ganglia

A
  • Caudate –> substantia nigra pars reticulata –> superior colliculus (head and eye movements)
  • Putamen –> external globus pallidus –> subthalamic nucleus –> internal globus pallidus (and substantia nigra)
  • Putamen –> internal globus pallidus –> ventral anterior and ventral lateral nuclei of dorsal thalamus –> frontal cortex (premotor and primary motor)
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24
Q

Subthalamic nucleus:

A

receives input from motor areas of the cerebral cortex, projects to the substantia nigra, and is reciprocally connected with the globus pallidus.

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25
Q

Ventral Anterior Nucleus

A

*Receives most of input from the basal ganglia
Especially the medial globus pallidus and substantia nigra, parts reticulata.
Projects to premotor cortex including the supplementary motor area of the frontal lobes
**Involved in planning and initiating movements.

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26
Q

Ventral Lateral Nucleus

A

*Receives input from the CEREBELLUM
Small input from the basal ganglia to the rostral part of the VL, as well.
Projects to the primary motor area, area 4, of the precentral gyrus and also has a smaller projection to premotor areas.
*Thus involved in MOTOR FEEDBACK from the cerebellum and basal ganglia to the cerebral cortex
-Along with ventral anterior nucleus
**Coordination, planning, learning of movement

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27
Q

motor nucleus of the thalamus

A

Ventral Anterior Nucleus, Ventral Lateral Nucleus …. idk some other stuff?

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28
Q

Outflow- Disinhibition

A
  • substantia nigra pars reticulata –> superior colliculus (head and eye movements)
  • external globus pallidus –> subthalamic nucleus –> internal globus pallidus
  • internal globus pallidus –> ventral anterior and ventral lateral nuclei of dorsal thalamus –> frontal cortex (premotor and primary motor)

The medium spiny neurons of the caudate and putamen release GABA onto their targets when they are excited by inputs

Inhibiting the inhibitors = disinhibition

Caudate –> substantia nigra pars reticulata –> superior colliculus (head and eye movements)

Putamen –> external globus pallidus –> subthalamic nucleus –> internal globus pallidus

Putamen –> internal globus pallidus –> ventral anterior and ventral lateral nuclei of dorsal thalamus –> frontal cortex (premotor and primary motor)

slide 23! look at the colors of the arrows

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29
Q

T/F Globus pallidus and substantia nigra pars reticulata lack spontaneous activity

A

FALSE
Globus pallidus and substantia nigra pars reticulata have lots of spontaneous activity

Are constantly and tonically inhibiting their target structures because they release GABA

(-caudate and putamen are NOT spontaneously active, have to wait to be activated)

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30
Q

explain the double GABA thing slide 24

A

Remember, in the absence of movement intention, the medium spiny neurons are silent
If you are not intending to move, you do not want to be moving
So the baseline state is inhibition of upper motor neuron circuitry
When you want to move, the medium spiny neurons get all firey and tell the inhibitory cells to stop it –> disinhibition of motor thalamus, superior colliculus, other things –> disinhibition of upper motor neurons  movement permitted to occur
Also probably why the medium spiny neurons start getting active BEFORE you execute a movement

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31
Q

summarize the globus pallidus and movement

A

At Baseline:
Globus pallidus –> prevents movement by inhibiting the motor thalamus (which is fundamentally good)

Time to Move:

Cortex- “I like to move it, move it”
Striatum- “You like to move it, move it”
Globus pallidus- “If you insist… I will just be quiet.”
Motor thalamus- “I like to move it, move it”
Upper motor neurons: “I like to move it, move it”
Lower motor neurons: “I like to MOVE IT”

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32
Q

Globus pallidus at baseline

A

Globus pallidus –> holding back the movement party by inhibiting the motor thalamus (which is fundamentally good)

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33
Q

Globus pallidus at Time to Move:

A

Cortex- “I like to move it, move it”
Striatum- “You like to move it, move it”
Globus pallidus- “If you insist… I will just be quiet.”
Motor thalamus- “I like to move it, move it”
Upper motor neurons: “I like to move it, move it”
Lower motor neurons: “I like to MOVE IT”

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34
Q

summary of ouflow

A

*Superior colliculus- influence head and eye movements
Secondary influence on eye movement comes from substantia nigra pars reticulata connections to relay neurons in the mediodorsal and ventral anterior thalamic nuclei, which project to the frontal eye field regions of the premotor cortex
This connection through the thalamus is a mechanism to facilitate or suppress inputs to circuits of upper motor neurons

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35
Q

Circuits Within the Basal Ganglia - names

A

Direct Pathway and indirect pathway

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36
Q

Direct Pathway

A
  • medium spiny neurons of striatum –> internal globus pallidus
    JOB: release tonic inhibition of the thalamic neurons connected to upper motor neurons
    Way for basal ganglia to initiate intentional movement
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37
Q

Indirect Pathway:

A

Indirect Pathway: select group of medium spiny neurons of striatum –> lateral division of globus pallidus (external segment)
External segment –> internal segment and subthalamic nucleus
Subthalamic nucleus also gets excitatory projections from cortex
Subthalamic nucleus –> internal segment of globus pallidus and substantia nigra pars reticulata

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38
Q

Indirect Pathway of the Basal ganglia

-job

A

Job: ANTAGONIZE the activity of the direct pathway to help open and shut the gates that start and stop movements

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39
Q

the direct and indirect pathways of the basal ganglia

A
  • Subthalamic neurons use GLUTAMATE in their synapses with the globus pallidus and substantia nigra
  • Activate indirect pathway –> excitation of globus pallidus and substantia nigra cells –> release GABA in response –> INCREASES INHIBITION WITHIN THE BASAL GANGLIA

Helps to:
Suppress competing motor programs
Select proper motor program

Still do not fully understand how this all works together

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40
Q

Direct and Indirect Pathways

A

Remember:
The caudate and putamen receive different streams of information from different regions of the cortex
The output from the caudate and putamen is segregated
Some of the projections to the basal ganglia are topographically mapped (visual and somatosensory) and some are overlapped (those from more interconnected or association regions)
There are rostrocaudal bands of cells that seem to be concerned with different parts of the body and the movement of that part

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41
Q

dopamine

-released by :

A

*Substantia nigra pars compacta cells release dopamine
Receive direct inputs from medium spiny neurons of striatum
Sends dopaminergic projections back to the medium spiny neurons
End result? Complex and depends on type of dopamine receptor expressed
*D1: increase cAMP and increases excitability (basically excitatory)
*D2: work with inhibitory G-proteins to decrease cAMP (basically inhibitory)
Receptors are on the shafts of the dendritic spines, which is a good place to modulate responses to cortical input

Dopamine to spiny cells that project to internal globus pallidus as part of the direct pathway is excitatory through D1
Dopamine to spiny cells that project to the external globus pallidus as part of the indirect pathway is inhibitory through D2

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42
Q

Substantia nigra pars compacta cells release ?

A

dopamine

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43
Q

Hypokinetic Movement Disorders

A

Parkinson’s disease:

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44
Q

Parkinson’s disease **

A

degeneration of the dopaminergic neurons in the substantia nigra pars compacta

  • Symptoms: bradykinesia (slowness of movement), rigidity of neck and extremities, minimal facial expression. Hypokinetic = decreased voluntary movement
  • Lose the effects of dopamine on movement (which was enhancing direct pathway and decreasing responsiveness of indirect pathway
  • Direct pathway  results in disinhibition of motor thalamus
  • Indirect pathway  reinforces inhibition of motor thalamus
  • Results in abnormally high inhibitory outflow to the motor thalamus
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45
Q

Hyperkinetic Movement Disorders

A

Huntington’s disease is what type of movement disorder

Insufficient tonic output from pallidum –> unwanted movement

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46
Q

Huntington’s disease

A
  • gradual onset of defects in behavior, cognition, and movement; genetic, progressive, and results in death
    While it is a movement disorder, the first symptoms are usually an increase in irritability, suspiciousness, and/or impulsive behavior
    Movement symptoms: rapid, jerky (“dancelike”) motions with no purpose; no weakness or ataxia
    Selective atrophy of the caudate and putamen (medium spiny neurons), with some additional degeneration in the frontal and temporal cortices
    External globus pallidus loses inhibitory input  reduces subthalamic nucleus excitatory input to internal globus pallidus –> reduced inhibitory outflow
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47
Q

nickname for the cerebellum and why

A

The Little Brain:
-it is pretty big
*Approximately 10% of the brain’s volume
Contains over 50% of the total number of neurons in the brain

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48
Q

Is the cerebellum considered a motor structure

A

Yes, but she is confusing me

-Considered a motor structure

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49
Q

Motor Functions of the Cerebellum

A
  • Maintenance of Balance and Posture
  • Coordination of Voluntary Movements

Majority of the cerebellum’s outputs are to parts of the motor system.
Motor commands are not initiated in the cerebellum
The cerebellum MODIFIES the motor commands of the descending pathways to make movements more adaptive and accurate.

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50
Q

Motor Functions- Maintenance of Balance and Posture

A

Important for making postural adjustments in order to maintain balance.
Input from vestibular receptors and proprioceptors
Modulates commands to motor neurons to compensate for shifts in body position or changes in load upon muscles.

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51
Q

damage to cerebellum:

A

Cerebellar damage leads to impairments in motor control and posture

Patients with cerebellar damage suffer from balance disorders, and they often develop stereotyped postural strategies to compensate for this problem (e.g., a wide-based stance).

52
Q

Motor Functions- Coordination of Voluntary Movements

A

Most movements are composed of a number of different muscle groups acting together in a temporally coordinated fashion.
Coordinate the timing and force of these different muscle groups to produce fluid limb or body movements.
-example: doing a cartwheel

53
Q

Motor Functions of the cerebellum: name them

give some examples

A
  • Coordination of Voluntary Movements
  • Maintenance of Balance and Posture- a cartwheel
  • Motor Learning- hitting a baseball
54
Q

Cerebellum: Motor Functions- Motor Learning

A

Plays a major role in adapting and fine-tuning motor programs to make accurate movements through a trial-and-error process (e.g., learning to hit a baseball).

55
Q

Anatomy of the Cerebellum

Two major parts:

A

slide 43

Cerebellar deep nuclei and cerebellar cortex

56
Q

Two major parts of the Cerebellum

A

Two major parts: Cerebellar deep nuclei and cerebellar cortex

57
Q

Cerebellar Deep Nuclei

A

-of the Cerebellum

the deep nuclei are the main way info gets OUT of the cerebellum

*Sole output structures of the cerebellum, as a whole
Axons leave the cerebellum
Almost all of the output of the cerebellum is through the deep nuclei

58
Q

T/F a lesion to the Cerebellar Deep Nuclei is better than an entire cerebellum lesion

A

FALSE

*Lesions of cerebellar deep nuclei are the same as complete lesion of the entire cerebellum

59
Q

Output from the fastigial nucleus of the cerebellar cortex influence:

A
  • orienting
  • vigilance
  • positional-autonomic
  • oromotor
  • posturomotor

slide 46

60
Q

Interposed nuclei:

A

-of the Deep Cerebellar Nuclei

*input from the intermediate zone and from cerebellar afferents that carry spinal, proximal somatosensory, auditory, and visual information.
They project to the contralateralred nucleus(rubrospinal tract).

61
Q

Dentate nucleus:

-projects to:

A

-of the Deep Cerebellar Nuclei

largest of the cerebellar nuclei; input from the lateral hemisphere and from cerebellar afferents that carry information from the cerebral cortex (via the pontine nuclei).
It projects to the contralateralred nucleusand theventrolateral (VL) thalamic nucleus.

62
Q

Vestibular nuclei:

location

A

outside the cerebellum in the medulla; functionally equivalent to the cerebellar nuclei because their connectivity patterns are identical to the cerebellar nuclei.

63
Q

which of these nuclei is not found in the cerebellum?

A

Vestibular nuclei

64
Q

Cerebellar Cortex

A

Highly convoluted sheet of tissue that encases the cerebellar deep nuclei
Contains almost all the neurons in the cerebellum.
Intricate pattern of folds and fissures that characterize the cerebellar cortex

65
Q

the part of the cerebellum that see from the outside

A

Cerebellar Cortex

66
Q

Functional Subdivisions of the cerebellum : name them

A

Vestibulocerebellum

Spinocerebellum

Cerebrocerebellum

67
Q

Vestibulocerebellum(flocculonodular lobeand its connections with thelateral vestibular nuclei):

A

-a Functional Subdivision of the cerebellum

the oldest part of the cerebellum
Involved in vestibular reflexes (such as the vestibuloocular reflex) and in postural maintenance.

68
Q

Spinocerebellum

A

-a Functional Subdivision of the cerebellum

(VERMISand theintermediate zones, as well as thefastigialandinterposednuclei):

major inputs from the spinocerebellar tract.
Its output projects to rubrospinal, vestibulospinal, and reticulospinal tracts
Involved in the integration of sensory input with motor commands to produce adaptive motor coordination.
Only part to get direct input from spinal cord

69
Q

Vermis

A

-falls under the Spinocerebellum

Most medial portion
Concerned with movements of proximal muscles
Regulates certain types of eye movements

70
Q

Cerebrocerebellum

A

(lateral hemispheresand thedentatenuclei): largest subdivision
*Extensive connections with the cerebral cortex, via the pontine nuclei (afferents) and the VL thalamus (efferents)

71
Q

Cerebellar Peduncles (Tracts)

A

Three fiber bundles carry the input and output of the cerebellum.

72
Q

Cerebellar Peduncles (Tracts)- name them

A

Three fiber bundles carry the input and output of the cerebellum.

73
Q

Theinferior cerebellar peduncle

A

Theinferior cerebellar peduncle(also called therestiform body) primarily contains afferent fibers from the medulla, as well as efferents to the vestibular nuclei.
Most complex

74
Q

Themiddle cerebellar peduncle

A

(also called thebrachium pontis) primarily contains afferents from the pontine nuclei.
One of the largest pathways in the brain (>20 million axons on each side)

75
Q

Thesuperior cerebellar peduncle

A

(also called thebrachium conjunctivum) primarily contains efferent fibers from the cerebellar nuclei, as well as some afferents from the spinocerebellar tract.
Axons coming mostly from the deep cerebellar nuclei and go to motor thalamus and upper motor neurons in the superior colliculus

76
Q

Cerebellar Peduncles: Inputs

A

Inputs to the cerebellum are conveyed primarily through the inferior and middle cerebellar peduncles
Arise ipsilaterally

77
Q

Cerebellar Peduncles: Outputs

A

Outputs are conveyed primarily through the superior cerebellar peduncle.
Outputs go ipsilaterally

78
Q

Projections to the Cerebellum

A

*indirect: from one side of the cortex to the other side of the cerebellum

*Also gets lots of sensory information
Axons from vestibular portion of CN8, and axons from vestibular nuclei in the pons and medulla
Go to vestibulocerebellum
Somatosensory relay neurons in the dorsal nucleus of Clarke in the spinal cord and external cuneate nucleus in medulla
Relay neurons carrying proprioceptive info from the body
Go to spinocerebellum
Face proprioceptive info sent via the mesencephalic trigeminal nucleus
Helps cerebellum figure out where your body and body parts are in space
Visual and auditory signals also relayed to cerebellum to supplement the proprioceptive information

*Somatosensory input is somewhat topographically mapped in the spinocerebellum
Maps are fractured, in that, each small area of the body is represented multiple times by spatially separated clusters of cells rather than on a single, continuous map

*Vestibular and spinal inputs remain ipsilateral
-Right cerebellum concerned about the right…
Cerebellum is generally concerned about same side things

*Receives modulatory inputs from the inferior olivary nucleus (inferior olive)

79
Q

Largest source of input to the cerebellum

A

cerebral cortex

80
Q

*Major destination of the projections to the cerebullum:

A

*Major destination: cerebrocerebellum

81
Q

Projections from the Cerebellum

-outputs

A

*the deep nuclei are the main way info gets OUT of the cerebellum
*Cerebellar cortex projects to deep cerebellar nuclei
Deep nuclei also get input from different part of the cerebellar cortex

Basically, outputs are to the cerebral cortex, upper motor neurons, and sometimes lower motor neurons

Dentate nuclei
Fastigial Nuclei
Interposed Nuclei
Vestibular nuclei:(outside the cerebellum in the medulla)
(MIGHT HAVE MISSED SOME)
82
Q

Dentate nuclei

A

-a projections from the cerebellum

*Input: Mostly info from cerebrocerebellum
Output: premotor and association cortices involved in planning and initiating movement
Output exits through the superior cerebellar peduncle, crosses the midline, and relays first in VL thalamus
*On the way to the thalamus, sends axons to eye-movement-related upper motor neurons in superior colliculus and to the red nucleus
Red nucleus –> inferior olive
Serves as feedback onto cerebellar inputs
Important for adaptive functions of motor learning

83
Q

Fastigial Nuclei

  • input:
  • output:
A

-a projection from the cerebellum

Fastigial Nuclei
Input: spinocerebellum
Output: nuclei of the reticular formation and vestibular complex
Outputs sent through the inferior cerebellar peduncle
*Influence pathways controlling axial and proximal limb musculature

84
Q

Interposed Nuclei

  • input:
  • output:
A

-a projection from the cerebellum
Interposed Nuclei
Input: spinocerebellum
Output: thalamic circuits that project to motor regions concerned with volitional movement of the limbs
Outputs sent through the superior cerebellar peduncle
In non-human primates, also send axon collaterals to the rubrospinal tract
Also output to superior colliculus to modulate eye movement (crosses midline)

85
Q

Vestibular nucleus

A

-a projection from the cerebellum

Vestibular nucleus
Input: vestibulocerebellum
Output: vestibular nuclei in the brainstem, which govern movement of eyes, head, and neck in response to changes in head placement
Outputs sent through the inferior cerebellar peduncle

Vestibulocerebellum also sends out direct projections to the vestibular nuclei

-NOT technically in the cerebullum
(I THINK!)

86
Q

Projections from the Cerebellum: closed loops

A

Also have closed loops where outputs are sent through the thalamus to non-motor areas of the cortex that provided initial inputs
These closed loops permit the cerebellum to regulate its own input
May influence coordination of non-motor programs (ex- problem solving)

87
Q

Circuits within the Cerebellum

Inputs to the cerebellar cortex synapse on the _____

A

Inputs to the cerebellar cortex synapse on the Purkinje cells… eventually
Largest of these pathways: cerebral cortex –> pontine nuclei –> contralateral cerebellum

*MOSSY FIBERS

  • Axons of granule cells = parallel fibers
  • Parallel fibers form excitatory synapses on the dendritic spines of Purkinje cells
  • The granule cells send axons up toward the cortical surface and each axon bifurcates in the molecular layer, sending a collateral in opposite directions.
  • Parallelfibers, run parallel to the folds of the cerebellar cortex, where they make excitatory synapses withPurkinjecellsalong the way.
88
Q

Mossy fibers

A

(Circuits within the Cerebellum)

  • Originate in thepontinenuclei, the spinal cord, the brainstem reticular formation, and the vestibular nuclei
  • Collateral branches that form excitatory connections on neurons in the deep nuclei AND on the granule cells of the cerebellar cortex
  • Each mossy fiber innervates hundreds of GRANULE CELLS.
89
Q

parallel fibers*

A

Axons of granule cells =

90
Q

Purkinje Cells

-structure

A

*Big cells with massive dendritic trees
*Essentially the only output from the cerebellar cortex
GABAergic
Each Purkinje cell has dendrites positioned to receive input from ~200,000 parallel fibers
Each parallel fiber can contact tens of thousands of Purkinje cells
*Purkinje cells also receive direct input onto their dendrites (not dendritic spines) from climbing fibers

91
Q

Climbing Fibers

A

Called climbing fibers because their axons climb and wrap around the dendrites of the Purkinje cell like a climbing vine and make multiple synapses
**Each Purkinje cell receives a single, extremely powerful input from a single climbing fiber. ****
*Each climbing fiber contacts only 10 Purkinje cells on average, making ~300 synapses with each Purkinje cell.
Restricted, but extremely powerful, excitatory input onto Purkinje cells.
*Purkinje cells are primary output of cerebellar cortex, so climbing fibers have a lot of power on what comes out

*So, what do Climbing Fibers do?
-Error signals
-May serve to provide a “motor clock” function in the initiation and timing of movements
“Climbing fibers evoke complex spikes immediately, which fits perfectly the high temporal precision required for the cerebellum to initiate or coordinate muscles” (Zang and Schutter, 2019)
Drive cerebellar learning

92
Q

Purkinje cells send ___ input to the _____

A

Purkinje cells send inhibitory input to the deep cerebellar nuclei
Deep cerebellar nuclei also get excitatory input from collaterals of mossy and climbing fibers

The inhibitory projections of Purkinje cells help to sculpt the discharge patterns of the deep nuclei

93
Q

also have…

A

Inhibitory (GABAergic) interneurons which modulate the inhibitory activity of Purkinje cells
Inhibiting inhibition
Basket cells: most powerful of the inhibitory interneurons
Stellate cell: another local circuit neuron; receives input from parallel fibers and can also inhibit Purkinje cells
Golgi cells: receive input from parallel fibers and provide an inhibitory feedback to the granule cells that gave rise to the parallel fibers

94
Q

Circuits within the Cerebellum

A
  • Deep excitatory loop:

* Cortical inhibitory loop:

95
Q

*Deep excitatory loop:

A

*Deep excitatory loop: mossy fiber and climbing fiber collaterals drive activation of neurons in the deep cerebellar nuclei
Input converging on the source of the final output

96
Q

How do we use the cerebellum?

A

The modulation of the cerebellar cortex on the output of the cerebellum may be important for motor learning

Learned adjustments to movement amplitude and timing
Lots of evidence from eyeblink conditioning
Inactivate cerebellum  no learning
Belief that procedural memories are formed in the cerebellum

97
Q

Cerebellum and Coordination of Ongoing Movement

A

Cerebellum: monitors and adjusts motor behavior
Activity changes constantly during the course of movement
Cells tonically active and rest, but firing frequency increases during movement
Responses influenced by relaxation/contraction of muscles, position of joints, direction of next movement

98
Q

What if your cerebellum is dysfunctional? 2 things

A

Bottomline: always have problems making smooth, precisely directed movements*

Deficits can be quite specific.
Site specific damage:
Vestibulocerebellum: problems standing upright and controlling direction of gaze
Nystagmus: eyes drift from target and then jump back to it with a corrective saccade
Spinocerebellum: difficulty controlling walking movements, shuffling walk.
Dysdiadochokinesia: difficulty performing rapid alternating movements
Dysmetria: over- or under-reaching
Intention tremors: due to disruption of the mechanism for detecting and correcting movement errors
Cerebrocerebellum: impairments in highly skilled sequences of learned movements (speech, playing music)

Cerebellar ataxia:

Appendicular ataxia

99
Q

Cerebellar ataxia:

A

sort of a hallmark symptom that something is wrong with your cerebellum; movements are jerky and imprecise instead of smooth and well-coordinated
Why? Cerebellum is important for correcting errors to ongoing movements and adapt to changing circumstances.
Movement errors are on same side of the body as damage
Alcohol abuse  degeneration of the anterior portion of the cerebellar cortex (which affects movement of lower limbs)
Results in staggering gait. No issues with arm or hand movement.

100
Q

Bird versus Humans

A

Birds have a very different shaped cerebellum (round vs spherical)
Bird cerebellum greater in size and weight
Cerebellums in different places
Vermis is larger in birds
Larger in birds that can fly than not
Center of equilibrium while flying?
Differences in sulci
Cytoarchitecture very similar between the two
Beak control?

101
Q

elephant Cerebellum

A

Largest cerebellum of all mammals relative to brain

Trunk-eye coordination

102
Q

Cerebellums are overrated

A 
Started walking late (at age 7)
Walks unsteadily as an adult 
Slurred speech
Mild intellectual impairment
Has normal word comprehension and was “fully orientated”
103
Q

Contains medium spiny neurons with large dendritic trees

A

Striatum (aka corpus striatum): caudate and putamen

104
Q

corticostriatal pathway

A
  • Nearly all regions of the cortex send direct projections to the striatum
  • Therefore, the cortex is the largest source of input
  • Mostly from association areas and the temporal, insular, and cingulate cortices
  • Collectively refer to these pathways as the CORTICOSTRIATAL PATHWAY
105
Q

basal ganglia is most known for what function?

A

Most known for role in movement but functions not limited to movement

106
Q

what does the striatum look like?

A

Striped because thin strips of gray matter that pass through the internal capsule to connect the caudate and dorsal putamen

107
Q

Subthalamic nucleus: *

A

Subthalamic nucleus: receives input from motor areas of the cerebral cortex, projects to the substantia nigra, and is reciprocally connected with the globus pallidus.

108
Q

T/F Medium Spiny Neuron display spontaneous activity

A

FALSE

Due to various Cell Neuro things (inward-rectifier potassium conductances), they rarely display spontaneous activity

109
Q

*Thalamus

A

*Thalamus- in general, talks back to regions of the cortex and serves as a modulator of cortical… decisions

110
Q

Globus pallidus and substantia nigra pars reticulata release ____

A

GABA

Globus pallidus and substantia nigra pars reticulata have lots of spontaneous activity

Are constantly and tonically inhibiting their target structures because they release GABA

111
Q

nonspecific nuclei are probs mostly involved in…

A

These nuclei are probably mostly involved in arousal and alertness.

112
Q

Hypokinetic

A

Hypokinetic = decreased voluntary movement

113
Q

anticipation of movement

-the specific parts of the basal ganglia:

A

Medium Spiny neurons increase firing rate before movement (even by several seconds)
Putamen- discharge in anticipation of limb and trunk movements
Caudate- discharge in anticipation of eye movement
Some vary based on destination of movement
Overall, suggests that Medium Spiny neurons encode the decision to move

114
Q

release GABA

A

caudate and putamen, Globus pallidus, substantia nigra pars reticulata

115
Q

explain the outflow of the basal ganglia that impacts head and eye movements

A

*Caudate –> substantia nigra pars reticulata –> superior colliculus (head and eye movements)

116
Q

*Fastigial nucleus:

A

*Fastigial nucleus: medial; input from the vermis and from cerebellar afferents that carry vestibular, proximal somatosensory, auditory, and visual information
Projects to the vestibular nuclei, thalamus, and the reticular formation.

117
Q

name the Deep Cerebellar Nuclei

A

Dentate nuclei
Fastigial Nuclei
Interposed Nuclei
Vestibular nuclei:(outside the cerebellum in the medulla)

118
Q

vestibular nuclei

  • inputs
  • project
A

The vestibular nuclei receive input from the flocculonodular lobe (vestibulocerebellum) and from the vestibular labyrinth.
They project to various motor nuclei and originate the vestibulospinal tracts.

119
Q

which Deep Cerebellar Nuclei carry spinal, proximal somatosensory, auditory, and visual information ?

A

Interposed nuclei

120
Q

Cerebrocerebellum function

A

*Well developed in primates
*Involved in the PLANNING AND TIMING of movements.
Involved in the cognitive functions of the cerebellum.
Includes the flocculus and nodulus

121
Q

indirect projections to the cerebellum

A

Projections are not direct
They synapse on ipsilateral pontine nuclei
Pontine nuclei receive input from a wide variety of sources, including most areas of cortex and the superior colliculus
Axons from the pontine nuclei (transverse pontine fibers or pontocerebellar fibers) cross the midline and enter contralateral cerebellum via the middle cerebellar peduncle
How we get info from one side of the cortex to the other side of the cerebellum

122
Q

Which pair of cerebellar peduncles are the primary inflow pathways into the cerebellum?

A

middle and inferior

123
Q

Climbing Fibers : originate

A

*Originate exclusively in the INFERIOR OLIVEand make EXCITATORY PROJECTIONS onto the cerebellar nuclei and onto thePurkinjecellsof the cerebellar cortex

124
Q

modulatory inputs to the cerebellum

A

*Receives modulatory inputs from the inferior olivary nucleus (inferior olive)
Important for the learning and memory functions of the cerebellum
Inferior olive gets input from a wide variety of structures including: the cortex, red nucleus, reticular formation, and spinal cord
These olivo-cerebellar axons exit the inferior olive, cross the midline, and enter the contralateral cerebellum via the inferior cerebellar peduncle

125
Q

The arrangement of Purkinje cells and parallel fibers

A

The arrangement of Purkinje cells and parallel fibers resembles telephone lines running between telephone poles.
Each parallel fiber makes contact with hundreds of Purkinje cells so the firing of each Purkinje cell can be influenced by thousands of mossy fibers.

Systems Neuroscience (24 decks)

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