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NSCI 201 > Basal ganglia > Flashcards

Basal ganglia Flashcards

1
Q

What are the two key roles of the basal ganglia?

A
  • Initiation of voluntary movements

- Suppression of unwanted movements

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2
Q

What are the two structures of striatum?

A
  • Caudate

- Putamen

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3
Q

What are the two structures of the pallidum?

A
  • Globus pallidus

- Substantia nigra pars reticulata

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4
Q

Does the basal ganglia have a direct pathway to spinal cord?

A

No.

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5
Q

From which structures is the basal ganglia receiving its inputs? To which structures is basal ganglia sending its outputs?

A
  • Receive from cortical structures.

- Send back computations to cortical structures.

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6
Q

What is the input zone of the basal ganglia? What kind of neuron is found there? What is the type of its neurons activity?

A
  • Striatum (caudate and putamen)
  • Medium spiny neurons
  • Phasic activity (voluntary activation)
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7
Q

Where do converge most medium spiny neuron axons?

A

Pallidum structures.

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8
Q

Give the specific input and output pathways of the striatum structures.

A

Caudate:

  • Input = receive connections from frontal lobe motor areas that control eye movements
  • Output = projections to substantia nigra pars reticulata -> superior colliculus (responsible for saccades and head and neck orientation)

Putamen:

  • Input = receive connections from SI and SII from parietal lobe, extrastriate visual cortices, premotor and motor cortices, auditory associate cortices
  • Output = projections to globus pallidus -> thalamus ->motor and premotor cortex
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9
Q

What is the type of output from MSNs of putamen and caudate to globus pallidus and substantia nigra pars reticulata?

A

Inhibitory through inhibitory GABAergic projections.

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10
Q

What is the consequence of neurons of globus pallidus and substantia nigra pars reticulata having an spontaneous discharge (inhibitory tonic activity) (against MSNs that are only phasic)?

A

Inhibition of unwanted movement by inhibiting neurons in superior colliculus and thalamus.

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11
Q

MSNs receive inputs from many structures. Name 4.

A
  • Cortical neurons
  • Local circuit neurons
  • Substantia nigra neurons (dopaminergic)
  • Raphe nulcei
  • Brainstem
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12
Q

True or false: MSNs receive thousands of inputs from a single cortical axon, but integrate the signals of only one cortical axon.

A

Faslse: receive few inputs from a single cortical axon, but integrate the signals of thousands of cortical axons.

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13
Q

Localize the inputs of the following structures on the MSNs:

  • Cortical structures
  • Local circuits
  • Thalamic neurons
  • Dopaminergic inputs from substantia nigra pars compacta
A
  • Cortical structures ->on dendritic spines
  • Local circuits ->on dendritic shafts and close to soma → modulate effects of cortical synapses
  • Thalamic neurons ->on dendritic shafts and close to soma → modulate effects of cortical synapses
  • Dopaminergic inputs from substantia nigra pars compacta ->on base of dendritic spines → modulate effects of cortical synapses
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14
Q

Why can we talk of gate-keeping in the neuronal circuitry of basal ganglia?

A

Neurons from pallidum structures are tonically inhibitory -> they prevent any unwanted movement to occur. They require to be inhibited to allow voluntary movements to be executed.

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15
Q

Consider the following basal ganglia circuitry:

A: medium spiny neuron from putamen
B: neuron from globus pallidus
C: neuron from VA/VL complex of thalamus
D: neuron from motor cortex

Assess the activity of each neuron when:

  • A is at rest
  • A is excited
A

A is at rest:

A: no activity
B: tonically inhibiting C
C: no activity
D: no activity

A is excited:

A: voluntary activity inhibiting C
B: Relieving inhibitory activity on C
C: transient activity
D: transient activity

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16
Q

What complex of the thalamus is implied in the initiation of movement by responding to inputs from basal ganglia?

A

VA/VL complex (ventral anterior nucleus and ventral lateral nucleus).

17
Q

What are the main central pathways of basal ganglia? What are their respective main outcomes?

A

Direct pathway: release upper motorneurons from tonic inhibition to allow movement.
Indirect pathway: increase tonic level of inhibition to prevent any movement.

18
Q

Describe activation of the direct pathway in basal ganglia.

A

Cerebral cortex activation (frontal lobe:primary motor cortex and premotor cortex) — + >caudate and putamen — - >globus pallidus, internal segment — less - > VA/VL complex of thalamus — + >frontal cortex.

19
Q

Describe activation of the indirect pathway in basal ganglia.

A

Cerebral cortex activation — + > caudate and putamen — - > external segment of globus pallidus — less - > subthalamic nucleus — + > internal segment of globus pallidus — more - > VA/VL thalamus — - >frontal cortex.

20
Q

True or false: activation of direct and indirect pathways will always make the pathways oppose to one another.

A

True.

21
Q

True or false: indirect and direct pathways of basal ganglia are voluntary.

A

True.

22
Q

Substantia nigra pars compacta can receive dopamine influxes at its D1 and D2 receptors. What are the consequences of such influxes on the direct and indirect pathways of basal ganglia?

A
  • Dopamine influx at D1 receptors enhances activity of the direct pathway
  • Dopmaine influx at D2 receptors suppresses activity of the indirect pathway
23
Q

What is the overall net effect of dopamine influx at D1 and D2 receptors of substantia nigra pars compacta?

A

Decrease inhibitory outflow from BG (favouring the outcome of the direct pathway).

24
Q

What is the theory of focus selection?

A

The hypothesis that direct and indirect pathways of basal ganglia are organized in a centre-surround fashion.

  • The direct pathway in the centre mediates a focused activation of a functional unit
  • The indirect pathway suppresses activity of surrounding functional units
25
Q

What does support the centre-surround model of direct and indirect pathways organization?

A

The “focused selection” theory.

26
Q

What does Parkinson’s disease cause on the level of basal ganglia structures?

A

Substantia nigra degenerates

27
Q

Parkinson’s disease is associated with impairment of voluntray movements. How is that symptom called?

A

Dyskinesia.

28
Q

Parkison’s disease results, amongst other symptoms, in difficulty to intiate and terminate voluntary movements. What is one possible cause?

A

Loss of dopamine in substantia nigra pars compacta.

29
Q

What does Huntington’s disease cause on the level of basal ganglia structures?

A

Caudate and putamen shrinkage.

30
Q

What syndrome concerning the neuropathology of basal ganglia produces ballistic and choreic movements?

A

Huntington’s disease.

31
Q

What syndrome concerning the neuropathology of basal ganglia is associated with the dysfunctional gate-keeping function of the globus pallidus?

A

Huntington’s disease.

NSCI 201 (14 decks)

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