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Brain and Behavior Exam 3 > Lec 33 Basal Ganglia > Flashcards

Lec 33 Basal Ganglia Flashcards

1
Q

What are main functions of basal ganglia?

A
  • refine motor plan
  • regulate action selection
  • facilitate habit learning
  • reward seeking
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2
Q

What comprises the striatum?

A 
dorsal = caudate nucleus and putamen
caudate = medial; putamen = lateral
ventral = nucleus accumbens septi [NAS]
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3
Q

What separates caudate and putamen?

A

anterior limb of internal capsule

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4
Q

What are the major components of the basal ganglia system?

A 
neo-striatum [dorsal and ventral]
pallidum [external, internal, ventral]
substantia nigra [compacta, reticulata]
ventral tegmental area [VTA]
subthalamic nuclei
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5
Q

What comprises the lenticular nucleus?

A

putamen and globus pallidus

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6
Q

What are the striatal cell bridges?

A

cells that cross the internal capsule to link the caudate to the putamen

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7
Q

What 2 structs does the posterior limb of internal capsule separate?

A

thalamus [medial]

lenticular nucleus [lateral]

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8
Q

What are medium spiny neurons [MSNs]? function?

A

striatal projection neurons

    • cell bodies medium, dendrites have spines
    • receive major input to BG system and are major output cells of striatum
    • GABAergic
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9
Q

What are two types of medium spiny neurons?

A
  • those that co-localize substance P and have D1-like DA receptors = stimulate cAMP –> mediate post-synaptic excitation
  • those that co-localize enkephalin and have D2-like DA receptors = inhibit cAMP and post-synaptic activity
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10
Q

Where do MSNs project?

A

from striatum to globus pallidus and substantia nigra

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11
Q

What is nucleus accumbens septi?

A

major structure of ventral striatum

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12
Q

Where do major inputs to BG system arise from?

A 
cerebral cortex = but especially frontal lobe!
thalamus
midbrain
raphe nuclei
locus coeruleus
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13
Q

For each of the 5 major inputs of BG system, which type of NT?

  1. cerebral cortex
  2. thalamus
  3. midbrain
  4. raphe nuclei
  5. locus coeruleus
A
  1. cerebral cortex == glutamate
  2. thalamus == glutamate
  3. midbrain == DA
  4. raphe nuclei == 5HT
  5. locus coeruleus = NE
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14
Q

What is globus pallidus?

A

lateral to internal capsule and medial to putamen

3 parts: external, internal, ventral

dorsal pallidum = external + internal

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15
Q

What structures make up the dorsal pallidum?

A

external and internal globus pallidus together = dorsal pallidum

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16
Q

Where is ventral pallidum located?

A

ventral to anterior commissure?

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17
Q

What type of output cells of GP?

A

all GABAergic = inhibitor

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18
Q

What is the subthalamic nucleus [STN]? type of output?

A

rostral/lateral to substantia nigra

output = glutamatergic [excitatory]

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19
Q

What is substantia nigra pars compacta?

A

GABAergic
often considered part of GPi
mainly same projections
source of DA neurons to striatum MSNs

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20
Q

What is unique projection of substantia nigra pars compacta?

A

superior colliculus = coordination eye, head, neck movement

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21
Q

Where do VTA DA neurons go?

A

to ventral striatum and limbic structures and frontal lobes

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22
Q

What are VTA DA neuron dysfunction associated with?

A

schizophrenia
psychoses
drug addiction

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23
Q

Which thalamic nuclei give input directly to striatum?

A
  • ventral group [VA/VM; VL with Vop and Vim
  • intralaminar nuclei [CM]
  • medial dorsal nucleus [MD]
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24
Q

What is function of medial part of VPM?

A

taste VP-MMMMMM

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25
Q

Sensory-motor areas of cortex send input to which parts of striatum?

A

putamen

26
Q

limbic-related input from cortex goes to which part of striatum?

A

ventromedial part

27
Q

Where do GABA/substance P MSNs from striatum project?

A

to GPi and SNr

28
Q

Where do GABA/enkephalin MSNs from striatum project?

A

to GPe

29
Q

What is the basic cortex-striatal circuit?

A

cortex –> BG –> internal processing –> thalamus –> back to cortex

30
Q

What happens to SN pars compacta and VTA in parkinsons?

A

pars compacta DA neurons degenerate

VTA does not

31
Q

Where does ventral striatum receive inputs from? where does it project to?

A

input:
cortex
also: amygdala, hippocampal formation, most of 5HT input to striatum

output:
ventral pallidum

32
Q

What is path of ventral striatum input/output?

A

cortex/amygdala/hippocampus/5HT –> ventral striatum –> ventral pallidum –> STN –> thalamus

33
Q

What is the “nigrostriatal pathway”? importance?

A

DA projection from substantia nigra pars compacta to striatum

circuit of motor functions

  • degenerates in parkinsons disease
34
Q

Where do dopaminergic projects from VTA go? function?

A

to ventral striatum

circuit of emotions/motivation = mesolimbic reward path

35
Q

Where does GPe primarily project?

A

to subthalamic nucleus

36
Q

What is function of STN? inputs/outputs?

A
  • receives GABAergic input from GPe and ventral pallidum
  • receives glutamate input from cerebral cortex
  • receives DA from SNpc
  • projects glutamate to pallidum and substantia nigra
  • target for deep brain stimulation
37
Q

What are the instrinsic processing structures of basal ganglia?

A
  • subthalamic nucleus [STN]
  • SNpc
  • VTA
  • GPe
38
Q

What separates the ventral striatum from the olfactory tubercle?

A

anterior commissure

39
Q

What are the cell types that exist in striatum?

A

projection neurons = medium spiny neurons
2 kinds –> substance P [excitatory] and enkephalin localizing [inhibitory]; both GABA

interneurons = aspiny
- mostly GABAergic

40
Q

Where does dorsal striatum project to?

A

globus pallidus [ext and in]

substantia nigra [reticulata and compacta]

41
Q

Where does ventral striatum project to?

A

ventral pallidum

ventral tegmental area [VTA]

42
Q

What is best way to localize GPe and Gpi on picture?

A

start at putamen = wide part of funnel

then travel medial; next structure = external; after that all other segments are part of internal

43
Q

What are the 3 output structures of basal ganglia? their NT?

A

globus pallidus
substantia nigra pars reticulata
ventral pallidum

all GABAergic = inhibitor

44
Q

What is function of each of the 3 BG outputs?

A

SNpr output = motor control of eye, head, neck
GPi output = motor control of rest of body
Ventral pallidum = limbic

45
Q

Where do major outputs from BG system project?

A

Thalamus [VLa, VA, VM, MD, ILN]
Epithelamaus/midbrain/pons
- superior colliculus; pontine tegmentum

46
Q

Via what routes do GPi/SNr output axons travel?

A

mainly = pyramidal motor system = lateral, fine motor control

  • ansal lenticularis = loops around internal capsule
  • lenticular fasciculus = goes through internal capsule

the 2 fiber bundles join together rostral to red nucleus to form fiber bundle called “thalamic fasiculus”

also = extrapyramidal = medial, postural control

  • some GPi/SNr output goes to prontine + medullary reticular formation to influence reticulospinal tract
  • SNpr projects to superior colliculus and influences tectospinal tract
47
Q

Where do fibers in thalamic fasiculus come from?

A
  • BG output via ansa lenticularis and lenticular fasciculus

- fibers from dentate nucleus of cerebellum

48
Q

How does basal ganglia coordinate higher level behavioral planning

A

receives info from 5 parallel functional loops of cortical info that process different types of info

  • relay info back to thalamus and send to modulate motor planning and execution
  • info also looped back from thalamus to basal ganglia for further refinement
49
Q

What type of NT in striatal, pallidal, and SNpr projections?

A

GABA = inhibitors

50
Q

What type of NT in input [cortex, thalamic] to BG system?

A

excitatory = glutamate

51
Q

What is direct pathway in BG system?

A

cerebral cortex –> excitatory MSNs with GABA/substanceP/D1 DA receptors –> inhibit GPi –> thus thalamus is disinhibited –> cortical excitation

DA activates this path by acting on D1 receptors

52
Q

What is indirect pathway in BG system?

A

cerebral cortex glutamate –> inhibitor MSNs with GABA/enkephalin/D2 Da receptors –> inhibit GPe –> disinhibit STN –> increases glutamatergic excitation GPi –> thalamic inhibition –> decreased cortical excitation to suppress movement

DA inhibits this path by acting on D2 receptors

53
Q

How does the STN coordinate activity of the direct/indirect BG paths?

A

“center-surround” system
= direct path promotes desired motor programs
= indirect suppresses all alternative plans one might pursue

54
Q

How does dopamine affect balance of direct/indirect paths?

A

dopamine excites direct path and inhibits indirect path thus net excitatory effect on thalamus

55
Q

How does parkinson’s disease affect BG paths?

A

parkinsons = loss of dopamine in nigrostriatal path so less DA input to direct/indirect paths
–> less excitement of direct + less inhibition of indirect –> net inhibition of thalamus

56
Q

What is the hyperdirect path? function?

A

function = fast inhibitory surround

cortex –> excites MSNs in striatum –> project to GPe and SNpc –> as SNpc synalse on DA projection neurons and INHIBIT them

57
Q

What are major symptoms of PD?

A
  • tremor
  • rigidity
  • bradykinesia
58
Q

what is pathology of PD along direct and indirect paths?

A

due to degeneration of substantia nigra pars compacta DA neurons

  • -> loss of DAergic D1 –> disinhibition GPi –> excess inhibition thalamus
  • -> loss of DAergic D2 inhibition –> overactivity GABA/Enk –> inhibition GPe –> disinhibition STN-GPi –> excess inhibition thalamus
59
Q

What is pathology of huntingtons along direct and indirect path?

A

atrophy of dorsal striatum = loss of striatal MSNs

direct: decreased activity of GABA/subP neurons –> less disinhibition of thalamus
indirect: decreased activity of GAPA/Enk neurons –> less inhibition of thalamus

indirect is more affected than direct –> so balance swings toward more direct path = too much movement/excitation

60
Q

What are main symptoms of huntingtons?

A

initial fidgetiness, restlessness

abrupt jerky abnormal movements

Brain and Behavior Exam 3 (32 decks)

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