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PHYSL 372 > Lecture 9 - The Wiring of the Cortex > Flashcards

Lecture 9 - The Wiring of the Cortex Flashcards

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1
Q

how does the Golgi stain work?

A

fills cells with silver chromate, making them appear black (creates contrast)

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2
Q

in 1906, Santiago Ramon y Cajal won the Nobel Prize for determining:

A

how brain cells communicate (unidirectional flow)

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3
Q

fluorescent dyes can be used to:

A

label cells using genetic approaches

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4
Q

what is the most common fluorescent protein for brain labelling?

A

green fluorescent protein (GFP)

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5
Q

what is the drawback to using Golgi stains and fluorescent dyes?

A

neurons have to be traced out either manually or with software

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6
Q

what are anterograde tracing neural connections?

A

carry dyes/fluorescent proteins through axons, to be visualized

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7
Q

how are anterograde tracing neural connections visualized?

A

using dyes and viruses (adenoassociated viruses (AAVs))

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8
Q

what are retrograde tracing connections?

A

dye or compound gets incorporated into the axon and travels backward to the cell body

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9
Q

how are retrograde tracing connections visualized?

A

using cholera toxin, fast blue, adenoassociated viruses (AAVs), and rabies

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10
Q

what are the four main types of neuron stimulation techniques?

A
  • electrical stimulation
  • light stimulation (optogenics)
  • chemical stimulations (pharmacogenetics)
  • patch clamp single cell stimulation
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11
Q

what is the earliest neurons stimulation technique?

A

electrical stimulation

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12
Q

neuronal stimulation technique where wires are inserted into brain tissue and current is passed into the tissue to depolarize neurons near the electrode, then record from other brain regions to see if neurons respond to stimulation

A

electrical stimulation

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13
Q

what are the pros of electrical stimulation?

A

1) easy to implement (stick a wire into the brain)
2) effective (repeatable across days)
3) precise activation onset

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14
Q

what are the cons of electrical stimulation?

A

1) indirect, unintended activation of other neurons close to the stimulation electrode
2) antidromic activation of post-synaptic cells

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15
Q

occurs when an impulse travels opposite to the normal direction to that in a normal nerve fiber

A

antidromic activation of post-synaptic cells

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16
Q

neuronal stimulation technique where a light sensitive rhodopsin is genetically expressed in neurons of interest. in the prescence of certain wavelengths of light, cells are depolarized and can be activated

A

optogenic stimulation

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17
Q

the first light dependent depolarization opsin used to activate neurons

A

channelrhodopsin (ChR2)

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18
Q

what are the pros of optogenic stimulation?

A

1) rapid control of spike timing
2) specific (genetically defined) neuron types can be activated without unintended activation of nearby neurons in the brain

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19
Q

what are the cons of optogenic stimulation?

A

1) light can change the temperature of neural tissue (have to be very careful when applying light pulses)
2) must deliver light to the brain, using brain implants (very invasive)

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20
Q

neuronal stimulation technique where a bioengineered receptor is expressed in cells of interest using genetic approaches. the receptor is designed to be activated by a specific, exogenous ligand

A

chemogenetic stimulation

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21
Q

when using chemogenetic stimulation, the cells will depolarize when:

A

exposed to their specific ligand

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22
Q

what are the pros of using chemogenetic stimulation?

A

1) cells can be activately by simply applying a drug
2) the drug acts specifically on the designer receptors
3) specific cell types can be activated

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23
Q

what are the cons of using chemogenetic stimulation?

A

1) no precise control over the timing of activation (cell just does its thing)

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24
Q

within a brain region, cells close to each other are more likely to:

A

connect to each other

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25
between brain regions, there is little to no relation between:
distance and connectivity
26
long range connections in the brain are:
mostly excitatory
27
micro connections are mainly:
inhibition
28
true or false: local connectivity in the brain is very strong
true
29
- release glutamate - excite post-synaptic cells - 90% of neurons in the cortex - larger in diameter (8-15 um) - project locally to nearby cells and to different regions of the brain - have many dendritic spines these are all characteristics of:
excitatory cells
30
excitatory cells are also known as:
pyramidal cells
31
- release GABA - inhibits the post-synaptic cells - 10% of neurons in the cortex - smaller in diameter - mainly project locally (within 0.2mm) - generally lacking spines these are all characteristics of:
inhibitory cells
32
inhibitory cells are also known as:
interneurons
33
what are the four main types of interneurons in the cortex?
- parvalbumin (PV) - somatostatin (SST) - vasoactive intestinal polypeptide (VIP) - neuropeptide Y/neurogliaform cells (NG)
34
type of interneuron that synapses onto cell bodies, is found in cortical layers 2-6, and work by GABA-A mediated inhibition
parvalbumin (PV) interneurons
35
what is parvalbumin?
a calcium binding protein
36
type of interneuron that synapses onto dendrites, is found in cortical layers 2-6, and works by GABA-A mediated inhibition
somatostatin (SST) interneurons
37
somatostatin interneurons allow for:
fine tuning and control of dendrites
38
type of interneuron that synapses onto other interneurons, is found mainly in cortical layers 1-3, and works by GABA-A mediated inhibition
vasoactive intestinal polypeptide (VIP) interneurons
39
vasoactive intestinal polypeptide (VIP) interneurons allow for:
cells to pass signals to other cells and cortical layers
40
type of interneuron that synapses onto other interneurons and excitatory cells, is found in cortical layers 1-3, and works by GABA-B and volume transmission
neuropeptide Y/neurogliaform (NG) interneurons
41
what compounds do neurogliaform cells express?
nitric oxide synthase and neuropeptide Y
42
what is feedforward inhibition?
inputs activate interneurons which inhibit the activity of pyramidal cells
43
what types of cells mediate feedforward inhibition?
parvalbumin (PV) cells
44
what is the purpose of feedforward inhibition?
acts to filter inhibition
45
with no PV cells, pyramidal cells fire:
in excess (similar to epilepsy)
46
what is feedback inhibition?
when excitation in one cell activates an interneuron to generate inhibition of itself
47
what types of cells mediate feedback inhibition?
parvalbumin (PV) and somatostatin (SST) cells
48
feedback inhibition provides:
stability
49
feedback inhibition arises from:
local excitation in neural circuits (in contrast with feedforward inhibition which can be generated by long range excitation)
50
what is lateral inhibition?
one pyramidal cell activates an interneuron to inhibit another pyramidal cell
51
what types of cells mediate lateral inhibition?
somatostatin (SST) cells
52
lateral inhibition generates ______ between neural groups
segregation
53
without somatostatin (SST) cells, other pyramidal cells can:
fire when they aren't supposed to
54
what is disinhibition?
inhibitory --> inhibitory cell connectivity, creating "net" excitation of another cell population (basically inhibiting the inhibitory cells)
55
the ______ connection is disinhibitory with respect to pyramidal cells
VIP --> SST
56
without vasoactive intestinal peptide (VIP), pyramidal cells:
fire less
57
what is volume inhibition?
neurogliaform cells release GABA and act on both GABA-B and GABA-A receptors
58
the effects of neurogliaform (NG) activation can be ______, therefore NG cells can influence activity in a _____ way
synaptic and extra-synaptic, non-synaptic (non-specific)
59
what is feedforward excitation?
excitatory cells mediate excitation of other neurons
60
an essential feature of communication within and between brain regions
feedforward excitation
61
connections between pyramidal cells is ______, so connectivity is relatively ______. however, most neurons are excitatory, so a small number of pyramidal cells can ______
~3-10%, infrequent, exert a lot of excitation
62
feedforward excitation is usually:
specific (neurons that "code" for one stimulus will communicate)
63
the thalamus excites _____ of the visual cortex
layer 4
64
can interneurons be excited by thalamic input?
yes
65
there is a strong positive correlation between ____ and ____
inhibition, excitation
66
small increases in the excitation:inhibition ratio generate:
action potentials
67
when you move, you generate:
"self-generated" sounds
68
why is it important for the brain to tune out "self-generated" sounds?
so that other sounds can be heard while moving
69
how does feedforward inhibition work with self-generated sounds?
- the motor cortex is activated during movement (running) - excitatory neurons from the motor cortex activate PV itnerneurons in the auditory cortex - PV interneurons suppress auditory cortex during movement
70
how does lateral inhibition work with surround suppression of the visual cortex?
pyramidal cells in layer V1 decrease their firing with larger stimuli that outside their receptive field, and SST interneurons increase their activity
71
surround suppression arises from:
lateral inhibition
72
surround suppression may participate in perceptual ability to:
recognize continuity of objects in the visual field
73
why do pyramidal cells prefer small stimuli?
because they are supressed by cells that like bigger stimuli (like SST interneurons)
74
during locomotion, V1 cells become:
active, even with no visual stimuli
75
VIP cells are activated during locomotion, which induces:
disinhibition of pyramidal cells
76
which neurotransmisster activates VIP cells?
acetylcholine
77
induces vasodilation and increases blood flow
vasoactive intestinal polypeptide (VIP)
78
induces vasoconstriction and decreases blood flow
somatostatin (SST)
79
describe the experiment to determine sync-fire chains
the preferred orientation of V1 cells was recorded. following the experiment, the same neurons were recorded in brain slices to test the connections between cells using patch clamp physiology
80
an immediate early gene that indicates neurons with high action potential firing rates
c-fos
81
following sleep, neurogliaform cells show:
c-fos in the cortex
82
neurogliaform cells may cause:
decreased cortical activity during sleep

PHYSL 372 (18 decks)

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