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Neuroanatomy > Basal Ganglia + Cerebellum > Flashcards

Basal Ganglia + Cerebellum Flashcards

1
Q

Basal Ganglia

A

Influence movement initiation, selection, & scaling

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2
Q

Cerebellum

A

Drive coordination, timing, postural reflexes, & adjustments

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3
Q

4 structures of basal ganglia

A
  1. Striatum
  2. Globus Pallidus
  3. Substantia Nigra
  4. Subthalamic Nucelus
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4
Q

basal ganglia function

A
  1. Procedural Learning
    -goal-directed behaviors
    - habitual behaviors
    - motor chunking
  2. Behavior Modulation
    -movement
    – selects particular movement
    – triggers initiation/termination
    – scales amplitude/speed/force
    - motivation
    – drives ideation/cognitive focus
    – magnifies impulses/apathies/obsesions/compulstions
    – w/ amygdala and nucleus accumbens – addiction/emot behavior
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5
Q

Striatum

A

“that which is striped”
striations are axon bundles. coronally presented as holes
2 nuclei:
1. caudate
2. Putamen

Interneurons (~5%):
– a few small gabaergic classes
– large, cholinergic, tonically active neurons (TANs)
Medium Spiny Neurons (~95%)

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6
Q

Medium Spiny Neurons (MSNs)

A

Inputs: spiny, dendritic inputs, from all corticies except primary sensory
Outputs: negligible spontaneous activity; gabaergic projections
Classes: two spatially intermingled classes (D1, D2)

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7
Q

D1 Spiny Neurons

A

Direct Pathway
Receptor Types: Dopamine: D1R
Adenosine: A1R

Neuropeptides:
Substance P
Dynophorin

Projects to:
GPi + SNr
(basal ganglia output)

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8
Q

D2 Spiny Neurons

A

indirect pathway

receptor types:
Dopamine: D2R
Adenosine: A2AR

Neuropeptides:
Enkephalin

projects to:
GPe
(basal ganglia intrinisic)

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9
Q

Globus Pallidus

A

primarly refers to dorsal

Primarily constitutively firing gabaergic projection neurons
Two segments:
– Globus Pallidus externus (GPe)
– Globus Pallidus internus (GPi)

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10
Q

GPe (lateral pallidum)

A

Striatal afferents from D2-MSNs along indirect pathway
Efferents to GPi, STN and SNr

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11
Q

GPi (medial pallidum)

A

Striatal afferents from D1-MSNs along direct pathway
Efferents to thalamus constitute primary basal ganglia outputs

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12
Q

Subthalamic Nuc

A

Only basal ganglia structure with glutamatergic efferents
Considered intrinsic structure
– branch of indirect pathway
* afferents from GPe
* efferents to GPi & SNr:
– reciprocal efferents to GPe yield negative feedback, e.g., enable pacemaker
Recently shown to receive substantial, largely cortical input: hyperdirect pathway

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13
Q

Substantia Nigra

A

Two Parts: SNr & SNc
Substantia Nigra pars reticulata
Similar to GPi in terms of: inputs, rates, outputs, & transmitter
Substantia Nigra pars compacta
Produces dopamine that it projects into striatum

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14
Q

Basic Connectivity

A
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15
Q

Gating & Selection

A

BG selects & gates actions (et al.)
Efferents are tonically active, inhibiting thalamus & movement
When a BG output is suppressed, its thalamic target is released to drive excitation into cortex

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16
Q

Negative Gating

A

Direct Pathway — Facilitation
— D1 firing disinhibits target loop
— Go: action via focal disinhibition

Indirect Pathway — Suppression
— D2 firing over-inhibits target loop
— Stop: inaction via focal inhibition

17
Q

Action Selection

A

Direct
— Focal Facilitation
— D1 firing disinhibits target loop

Indirect
— Diffuse Suppression
— D2 firing inhibits all loops
Coactivation selects target action via center-surround mechanism Propagates downstream

18
Q

Dopamine

A

from SNc

Overview
Tonic striatal dopamine relevant to activity level
Phasic striatal dopamine relevant to reward & learning

19
Q

Parkinson’s Disease Symptoms

A

Bradykinesia & Akinesia: suppression of movement, or inability to initiate movement
Rigidity & Tremor: disruption of action selection mechanism
Apathy, Depression, Anxiety: same deal, other loops

20
Q

Parkinson’s Disease Treatments

A

Levodopa (L-DOPA)
Restores tonic dopamine
Less effective for phasic
Over time, dyskinesias
Deep Brain Stimulation (DBS)
STN or GPi
Over-activate SNr/GPi ?

21
Q

Cerebellum function writ large

A

Drive coordination, timing, postural reflexes, & adjustments

22
Q
A
23
Q

3 Lobes of Cerebellum

A

anterior
posterior
flocculonodular

24
Q

Cerebellar Nuclei

A

Dentate, Interposed (Eboliform/Globose), Fastigial

25
Q

Cerebellar Zones

A

lateral, medial (vermis/ intermediate)

26
Q

anatomical cerebellar nuclei

A

dentate, interposed (eboliform/globose) fastigial

27
Q

Cerebellar Function

A

Computation
70-80% of human neurons
Independent, identical circuits repeated throughout
Thought to perform roughly the same computation in all domains: coordinate, time, smooth

Behavioral Tuning
Muscle actions
Coordination
Motor timing
Smooth moves
Involved in other domains, but the full effects remain unclear
Executive: verbal fluency, working memory, planning
Personality / Affect: focus, attention, impulsivity

28
Q

Vestibulocerebellum

A

Vestibulocerebellum
Flocculonodular Lobe
Oldest region of cerebellum: center nodulus flanked by 2 flocculi
Coordinate balance & oculomotor control
Inputs: vestibular, visual, & neck proprioceptive
Outputs: brain stem & fastigial nucleus into spine & motor cortex

29
Q

spinocerebellum

A

Vermis & Intermediate Zones
Coordinates motor control via somatotopic mapping
Inputs: broadly proprioceptive
… but also vestibulary, visual, auditory, & somatosensory
Outputs: fastigial & interposed* nuclei, to spine & motor cortex

30
Q

Cerebrocerebellum

A

Lateral Hemispheres
Newest region of cerebellum: very large in humans
Inputs: indirect, non-sensory, association corticies
Outputs: dentate nucleus, to largely non-motor corticies

31
Q

Components of cerebellar microcircuit

A

Purkinje Cells
Parallel Fibers
Climbing Fibers

32
Q

Purkinje Cells

A

Stacked, fan-shaped dendritic arbors
Gaba-ergic projections to deep cerebellar nuclei

33
Q

Parallel Fibers

A

(from granule cells)
substantial convergence/divergence onto each purkinje cell (~100k syns!)

34
Q

Climbing Fibers

A

(from inferior olive)
only one CF per purkinje cell; minimal divergence (a few)

35
Q

Results of cerebellar dysfunction?

A

uncoordinated movements
ataxia

36
Q

full cerebellar diagram 1

A
37
Q

full cerebellar diagram 2

A
38
Q

Dopamine Rate Model

A

D1-MSNs: dopamine increases rate, facilitating movement
D2-MSNs: dopamine decreases rate, facilitating movement
Loss of Dopamine
D1-MSNs: loss decreases rate, suppressing movement
D2-MSNs: loss increases rate, suppressing movement

Neuroanatomy (16 decks)

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