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PHYSL 372 > Interneuron Network Connnectivity > Flashcards

Interneuron Network Connnectivity Flashcards

1
Q

What are 2 methods of visualizing neurons?

A
  1. golgi stain method
  2. fluorescent dyes
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2
Q

Describe how the golgi stain method allows us to visualize neurons.

A
  • fill cells with silver-chromate
  • cells appear black
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3
Q

Describe how fluorescent dyes are used to visualize neurons.

A
  • fluorescent dyes used to LABEL cells using GENETIC APPROACHES
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4
Q

What is the drawback of using golgi staining and fluorescent dyes to visualize neurons?

A

neurons have to be traced out either manually or with software

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5
Q

anterograde vs retrograde tracing neural connections. what kind of tracers are used?

A

anterograde:
- carry dyes through axons to be visualized
- tracers: dyes, viruses (AAVs)

retrograde:
- dye travels from AXON BACKWARD TO CELL BODY
- tracers: cholera toxin, fast blue, AAVs, rabies

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6
Q

What are 4 neuron stimulation techniques?

A
  • electrical stimulation
  • chemical stimulation
  • light stimulation
  • patch clamp single cell stimulation
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7
Q

How do neuron stimulation techniques allow us to visualize neural connectivity?

A
  1. stimulate neurons
  2. these neurons stimulate “the other neurons”
  3. record activities in “the other neurons” (that are part of the network)
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8
Q

Which neuron stimulation technique is the oldest?

A

electrical stimulation

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9
Q

Describe how to set up electrical stimulation technique.

A
  1. place wire into brain tissue and inject current to depolarize neurons near electrode
  2. record form other brain region to see if neurons respond to stimulation
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10
Q

pros of electrical stimulation

A
  1. easy to implement
  2. effective
  3. precise activation onset
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11
Q

cons of electrical stimulation

A
  1. indirect, UNINTENDED activation of other neurons close to stimulation electrode
  2. antidromic activation of post-synaptic cells
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12
Q

Describe how to set up optogenetic stimulation.

A
  1. light-sensitive RHODOPSIN is genetically expressed in neurons of interest
  2. light causes cell depolarization and activation
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13
Q

pros of optogenetic stimulation

A
  1. rapid control of spike timing
  2. specific neuron types can be activated WITHOUT UNINTENDED activation of nearby neurons
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14
Q

cons of optogenetic stimulation

A
  1. light can change the temperature of neural tissue
  2. must deliver light to the brain using BRAIN IMPLANTS
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15
Q

Describe how to set up chemogenetic stimulation.

A
  1. designer receptor is expressed in cells of interest using genetic approaches
  2. receptor is ACTIVATED by a SPECIFIC ligand/drug
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16
Q

pros of chemogenetic stimulation

A
  1. cells can be activated simply by applying a drug
  2. drug acts SEPCIFICALLY on designer receptors
  3. specific cell types can be activated
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17
Q

cons of chemogenetic stimulation

A

no precise control over timing of activation

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18
Q

Describe the setup of paired patch clamp recording

A

2 single neurons are recorded using INTRACELLULAR techniques (so that they can be depolarized with current injection)

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19
Q

pros of paired patch clamp recording

A

definitive test of connectivity between neurons in the brain
(i.e. ONLY TRUE WAY TO TEST CONNECTIVITY BETWEEN NEURONS)

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20
Q

cons of paired patch clamp recording

A
  1. challenging to implement (hard technique)
  2. high failure rate
  3. only useful for testing close connections
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21
Q

TRUE or FALSE: patch clamp recording can be used to test long connections between neurons

A

FALSE: only useful for testing CLOSE connections

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22
Q

Which neuron stimulation technique is the only true way to test connectivity between neurons?

A

paired patch clamp recordings

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23
Q

What is the basic connectivity rule within a brain region?

A

cells close to each other are more likely to connect to each other

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24
Q

What is the basic connectivity rule between brain regions?

A

no/weak relation between distance and connectivity

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25
Q

TRUE or FALSE: macro connections are mainly inhibitory and micro connections are mainly excitatory

A

FALSE:
- micro connection = inhibitory
- macro connection = excitatory

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26
Q

For excitatory cells:
- pyramidal cell or interneuron?
- NT released?
- what percentage of cells in the cortex?
- larger or smaller in diameter?
- project locally or to different brain regions?
- many or lacking in dendritic spines?
- apical or aspiny?

A
  • pyramidal cell
  • glutamate
  • 90% of cells
  • larger in diameter
  • project both locally AND to different brain regions
  • many dendritic spines
  • apical
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27
Q

For inhibitory cells:
- pyramidal cell or interneuron?
- NT released?
- what percentage of cells in the cortex?
- larger or smaller in diameter?
- project locally or to different brain regions?
- many or lacking in dendritic spines?
- apical or aspiny?

A
  • interneuron
  • GABA
  • 10% of cells
  • smaller diameter
  • project locally
  • lacking in dendritic spines
  • aspiny
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28
Q

What are the 4 types of interneurons and their connections?

A
  • IN with parvalbumin (PV)
  • IN with somatostatin (SST)
  • IN with vasoactive intestinal polypeptide (VIP)
  • IN with neuropeptide Y/neurogliaform cells (NG)
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29
Q

What kind of peptide is parvalbumin?

A

calcium-binding

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30
Q

Which interneuron is the main inhibitory cell?

A

parvalbumin (PV)

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31
Q

For parvalbumin INs:
- synapse on?
- which layers of the cortex?
- inhibition mediated by which NT?

DRAW

A
  • synapse on cell bodies
  • layer 2-6
  • GABA inhibition
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32
Q

For somatostatin INs:
- synapse on?
- which layers of the cortex?
- inhibition mediated by which NT?

DRAW

A
  • synapse on dendrites
  • layer 2-6
  • GABA inhibition
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33
Q

For vasoactive intestinal peptide INs:
- synapse on?
- which layers of the cortex?
- inhibition mediated by which NT?

DRAW

A
  • synapse on OTHER INs
  • layer 1-3
  • GABA inhibition
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34
Q

For neuropeptide/neurogliaform INs:
- synapse on?
- which layers of the cortex?
- inhibition mediated by which NT?

DRAW

A
  • synapse on OTHER INs AND EXCITATORY CELLS
  • layer 1-3
  • GABA and volume transmission
35
Q

Which type of IN is involved in disinhibition?

A

VIP

36
Q

Which type of IN inhibits all neuron types?

A

NG

37
Q

what is feedforward inhibition?

A

inputs activate INs (without necessary activation pyramidal cells)

i.e. only activate INs

38
Q

Which type of IN mediates feedforward inhibition?

A

PV

39
Q

What happens to pyramidal cell activity without PV cells?

A

no feedforward inhibition –> pyramidal cells fire like epilepsy

40
Q

What is feedback inhibition?

A

when excitation in one cell activates an IN to generate INHIBITION OF ITSELD

41
Q

which type of IN mediate feedback inhibtion?

A

PV and SST

42
Q

What type of inhibition provides stability?

A

feedback

43
Q

TRUE or FALSE: FEEDFORWARD inhibition arises from local excitation, whereas FEEDBACK inhibition can be generated by long-range excitation

A

FALSE:
- feedback inhibition = micro
- feedforward inhibition = macro

44
Q

What is lateral inhibition?

A

one pyramidal cell activates an IN to INHIBIT ANOTHER PYRAMIDAL CELL

45
Q

Which type of IN mediates lateral inhibition?

A

SST

46
Q

What type of inhibition generates segregation between neural groups?

A

lateral inhibition

47
Q

Without SST cells in lateral inhibition, what can happen?

A

OTHER pyramidal cells can fire when they are not supposed to

48
Q

What is disinhibition?

A

inhibitory cell –> inhibitory cell connectivity, creating net EXCITATION of ANOTHER CELL POPULATION

49
Q

Which 2 IN types mediate disinhibition?

A

VIP–> SST disinhibitory on pyramidal cells

50
Q

What happens to pyramidal cell activity if VIP cells are not present?

A

pyramidal cells fire LESS

51
Q

What is volume inhibition?

A

neurogliaform cells release GABA, and act on GABA-B and GABA-A receptors

52
Q

TRUE or FALSE: GABA-A is a slow receptor

A

TRUE

53
Q

Which IN type mediates volume inhibition?

A

NG

54
Q

TRUE or FALSE: disinhibition effects can be synaptic and extra-synaptic

A

FALSE: volume inhibition

55
Q

TRUE or FALSE: SST cells can influence activity in a non-synaptic way

A

FALSE: NG cells

(because volume inhibition has extra-synaptic effects)

56
Q

What is feedforward excitation?

A

excitatory cells mediate excitation of other cells

57
Q

which type of cortical circuit motif is an essential feature of communication within and between brain regions?

A

feedforward excitation

58
Q

What is the percentage of connections between pyramidal cells? Is this frequent or infrequent? Does this mean a large or small number of pyramidal cells are needed to exert a lot of excitation?

A

3-10%, infrequent, small number needed

59
Q

TRUE or FALSE: feedforward excitation is usually specific and not general

A

TRUE

60
Q

which layer of the visual cortex does the thalamus excite?

A

layer 4

61
Q

TRUE or FALSE: inhibition strength and excitation strength are NOT correlated

A

FALSE: they are correlated

62
Q

Describe how excitation and inhibition are balanced.

A

small increases in the excitation:inhibition ration generate APs

63
Q

Which type of inhibition mediates the “tuning-out” of self-generated sounds? Describe how it works (consider the type of IN involved)?

A

feedforward inhibition
- motor cortex is activated during movement
- excitatory neurons from motor cortex activate PV interneurons in auditory cortex
- KEY: PV INs suppress auditory cortex during movement

64
Q

TRUE or FALSE: gamma rhythms only require activity of pyramidal cells

A

FALSE: both pyramidal cells and INs

65
Q

When can gamma rhythms be recorded from the cortex?

A

during periods of increased attention

66
Q

What can control the frequency of firing of pyramidal cells?

A

decay of inhibitory potentials

67
Q

Which type of of inhibition can participate in gamma rhythm generation?

A

feedforward and feedback inhibition

68
Q

TRUE or FALSE: auditory stimuli evoke gamma rhythms in the auditory cortex

A

FALSE: VISUAL stimuli evoke gamma rhythms in the VISUAL cortex

69
Q

How does suppressing SST affect gamma rhythms? What does this imply?

A
  • decrease gamma rhythms in visual cortex
  • implication: feedback inhibition plays a role in regulating gamma rhythms
70
Q

what type of inhibition plays a role in generating gamma rhythms in the hippocampus?

A

feedforward inhibition (PV)

71
Q

Do pyramidal cells in V1 increase or decrease their firing with larger stimuli that are outside of their receptive field? What is the name for this phenomenon?

A

DECREASE FIRING; surround suppression

72
Q

Which type of IN’s activity is increased in surround suppression?

A

SST

73
Q

what kind of inhibition modulates surround suppression?

A

lateral inhibition

74
Q

What kind of inhibition may participate in perceptual ability to recognize CONTINUITY of objects in the visual field?

A

lateral inhibition

75
Q

TRUE or FALSE: in surround suppression, SST INs increase their activity, and pyramidal cells decrease their activity, as the size of the object becomes larger

A

TRUE

76
Q

TRUE or FALSE: during locomotion, V1 cells are only activated with visual stimuli

A

FALSE: V1 cells activated even with no visual stimuli

77
Q

How are V1 cells activated during locomotion even without visual stimuli? Which type of inhibition mediates this? Which INs are involved?

A
  • disinhibition of V1
  • VIP cells are activated during locomotion by ACh –> induce disinhibition of pyramidal cells

note: SST is also involved (VIP –> SST)

78
Q

Does VIP induce vasodilation or vasoconstriction? SST?

A
  • VIP = vasodilation
  • SST = vasoconstriction
79
Q

What is stimulus encoding, which type of circuit connectivity is involved?

A
  • neurons that “code” for 1 stimulus will synapse on each other
  • feedforward excitation
80
Q

When does the cortex exhibit global inhibition?

A

during sleep

81
Q

What does the immediate early gene c-fos indicate?

A

high AP firing rates

82
Q

How do we know that NG cells may cause decreased cortical activity during sleep?

A

AFTER SLEEP, neurogliaform cells show c-fos

(sleep-deprived, not much c-fos activation)

83
Q

Which IN shows c-fos?

A

NG

84
Q

TRUE or FALSE: Gabazine acts on GABA-B receptors and it is fast acting

A

FALSE: it acts on GABA-A, but yes it is fast-acting

PHYSL 372 (21 decks)

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