L23 - Classic Basal Ganglia Model Flashcards

1
Q

Rapid decision making is based upon our ________

A

Past Experiences

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2
Q

What factors about our past experiences influence our decision making?

A

Consequences: Rewards or Punishments

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3
Q

Decision making is based on what ability (or inability)

A

to delay gratification

(if we cant we become impulsive, this is ADHD)

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4
Q

The “classical basal ganglia model” of decision making is what type of model?

A

Neurobiological

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5
Q

What part of our brain is responsible for “transmitting messages”

A

Neurons

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6
Q

What happens when a neuron receives a message that is strong enough for it to be transmitted?

A

An action potential is generated

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7
Q

A neurotransmitter does what?

A

Transmits a chemical message from the presynaptic neuron to the postsynaptic neuron

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8
Q

Do neurons “touch” each other?

A

No, there is a gap in between them

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9
Q

How might a “message” from a presynaptic neuron be broken?

A

If the postsynaptic neuron does not have the appropriate receptors or it is blocked somehow.

e.g. neurotransmitter is dopeamine but receptor does not have dopeamine receptors or is blocked

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10
Q

What is GABA?

A

Gamma-Aminobutyric Acid (GABA)

The major inhibitory neurotransmitter in the central nervous system

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11
Q

What is Glutamate?

A

Major excitatory neurotransmitter in the central nervous system

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12
Q

What are the names of the major inhibitory and excitatory neurotransmitters?

A

GABA - inhibitory

Glutamate - Excitatory

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13
Q

If a postsynaptic neuron has GABA receptors and GABA is released from the presynaptic neurons, what happens?

A

The effect of the neurotransmitter will be to make the neuron less likely to perform an action potential

inhibitory neurotransmittor

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14
Q

If a postsynaptic neuron has Glutamate receptors and Glutamate is released from the presynaptic neurons, what happens?

A

It will excite the postsynaptic neuron

Excitatory

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15
Q

If you want to inhibit a postsynaptic neuron, what chemical can you use to do this?

A

GABA

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16
Q

According to the classic basil ganglia model

Does a neuron which recieves an excitatory message pass on the excitatory message to other neurons?

A

Not necessarily, some neurons recieve an excitatory neuron (glutamate) and get excited, but then they release GABA to stop other ‘messages’ coming from the presynaptic neuron after it

some neurons are design to inhibit other neurons, even when recieving excitatory neurotransmitters

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17
Q

Describe the classical basal ganglia model of action selection

A
  1. Pre-motor cortex generates pre-action plans
  2. Send action plans to the basal ganglia through excitatory connections
  3. basal ganglia decides whether to accept/reject action plan
  4. If accepted, basal ganglia sends output to the thalamus, which disinhibits the thalamus
  5. Motor command is then performed
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18
Q

What is the basal ganglia?

A

a collection of interconnected nuclei in the midbrain) that ‘select’ or ‘inhibit’ a motor plan

acts as a gate that can say yes or no to the action plans that the cortex generates

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19
Q

When is a motor command performed according to the basal ganglia action model?

A

When the basal ganglia disinhibits the thalamus

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20
Q

What is the normal state of the thalamus?

A

Constant ‘Tonic’ Inhibition

Constantly inhibited - this prevents any motor command being performed

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21
Q

Cortex Creates Potential Actions - Basal Ganglia Selects Actions - Basal Ganglia Disinhibits Thalamus

What does this do?

What model are these three steps from?

A

Generates an action

The classical basal ganglia model of action selection

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22
Q

What would happen if the thalamus was not constantly inhibited?

A

We would constantly be doing random actions

We would have no control over our bodies

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23
Q

What does the basal ganglia do to the thalamus to generate a motor command?

What is this pathway called that is responsible for this?

A

Disinhibits the thalamus

The Direct Pathway

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24
Q

What does the indirect ‘no-go’ pathway do?

A

If this pathway is activated, it further inhibits the thalamus, to make certain that the action is not performed

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25
Q

What region of the brain is responsible for the ‘no-go’ pathway?

A

Basal Ganglia

same as direct pathway

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26
Q

The direct pathway 1)_____ the thalamus, while the indirect pathway 2)_____ the thalamus.

A

1) disinhibits

2) further inhibits

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27
Q

What level of inhibition is the thalamus typically at without the influence of the basal ganglia?

A

weak inhibition

28
Q

Name the two pathways of the classical basal ganglia model and what they are responsible for

A

Direct “go” pathway - select motor command

Indirect ‘no-go’ pathway - inhibit motor command

29
Q

In the classical basal ganglia model, what is the “critical point of difference” of each pathway?

A

The Striatum

30
Q

What is the importance of the Striatum?

A

This is where the two pathways diverge in the basal ganglia

31
Q

How does the striatum operate?

A

It has two distinct populations of neurons (excitatory and inhibitory)

When the cortex sends a message to the striatum, the type of neuron that is released from the striatum will determine whether the action is performed.

The neurons are competing with each other, one trying to make it happen and one trying to inhibit it

32
Q

How does the striatum determine what population of neurons are released?

A

Our previous experience

These neurons have learnt from our previous experiences

33
Q

Where are our memories of what has happened in the past stored according to the classic basal ganglia model for action?

A

In the population of neurons in our striatum

34
Q

How does the striatum learn from our previous experiences to generate motor actions?

A

If we recieve a reward we recieve an increase in dopamine - this strengthens direct pathway connections - actions are more likely to be repeated in the future

35
Q

How does the striatum learn from our previous experiences to inhibit motor actions?

A

If we recieve punishment we get a decrease in dopamine activity - this strengthens the indirect pathway connections - actions are less likely to be repeated in the future

36
Q

What happens to the stratium when you recieve a drop in neurons?

When does this happen and what is the likely future outcome?

A

Indirect pathway connections are strenghtened

You have been punished and are less likely to perform that action

37
Q

What happens to the stratium when you recieve a increase in neurons?

When does this happen and what is the likely future outcome?

A

Direct pathway connections are strenghtened

You have been rewarded and are more likely to perform that action

38
Q

How many dopamine receptors are there?

A

5

(D1-D5)

39
Q

Dopamine D1 receptors have what type of sensitivity to dopamine?

What does this mean?

A

Low sensitivity

(They have low affinity to dopamine)

In order for them to be activated they need to recieve a large burst of dopamine

40
Q

What is the primary use of the D1 receptors?

A

To detect dopamine bursts from reward

Critical for learning in the direct pathway neurons

41
Q

What is D1-mediated long-term potentiation?

A

A type of neuroplasticity that strengthens the synapses, or connections, between neurons, so ‘messages’ between them are transmitted more efficiently

42
Q

What does a burst in dopamine result in?

A

D1-mediated long-term potentiation

43
Q

What is long-term potentiation?

How does it work?

A

Long-term potentiation is a type of synaptic plasticity that increases the efficacy of neurotransmission.

Repeated synchronous firing increases the strength of the connections between two neurons.

44
Q

What is synaptic plasticity?

A

Presynaptic transmitters and postsynaptic recievers can increase in strength if it is used repeatedly, allowing for more information to pass through.

After repeated firing the presynaptic and postsynaptic neurons change to allow for more information to pass through (long-term potentiation)

45
Q

What type of affinity (sensitivity) do dopamine D2 receptors have?

What does this mean

A

High affinity for dopamine

Low levels of dopamine activate them; high levels inhibit them

46
Q

What happens to dopamine D2 receptors when a high amount of dopamine is recieved?

A

They shut off

only responsive to low levels of dopamine

47
Q

Repeated dopamine dips result in what?

A

D2-mediated long-term potentiation

less likelihood to perform action

48
Q

When you are punished, which dopamine receptors are activated and why?

A

D2 receptors

When you are punished it results in a dopamine “dip” and release less dopamine - D2 receptors are the only receptors that will activate then due to their high sensitivity to dopamine

49
Q

Where is DNA located?

A

Inside every cell contains a nucleus

In the nucleus is DNA

50
Q

What is a good metaphor for DNA and genes?

A

They are a recipe book

Cells open up the recipe book to find the gene it needs to use and uses it

51
Q

How many genes in our DNA?

A

Roughly 20,000

52
Q

How does a cell produce a protein?

A

Unfold our DNA, read the DNA (like a book) and produce the protein it needs

53
Q

How does a neuron replace a receptor or increase a receptor?

A

Unfold the DNA for the receptor, produce the relevent gene, create the receptor

54
Q

The DRD1 gene is a gene that contains the recipe for what?

A

The dopamine D1 receptor

55
Q

The DRD2 gene is a gene that contains the recipe for what?

A

Dopamine D2 receptor

56
Q

Are all cells able to express DRD1 and DRD2 genes?

A

No

Not all cells use the recipes to produce these types of receptors

57
Q

What does “cells having a preference for genes” mean?

A

That some cells are more likely to express genes than others

e.g. some are more likely to express DRD1 whereas others DRD2

58
Q

The indirect pathway has more __ receptors

A

D2 receptors

59
Q

The direct pathway has more __ receptors

A

D1

60
Q

What is the benefit of the indirect and direct cells having preferences for DRD1 or DRD2 genes?

A

That they become more efficient at detecting the dopamine levels and better at producing/inhibiting actions

61
Q

What basal ganglia pathway is responsible for “impulsivity”

A

Direct pathway

62
Q

Which striatum pathway is responsible for the delay of gratification and resisting impulses?

A

indirect ‘no-go’ pathway

63
Q

Everyone is similar when it comes to our ability to learn from reward and punishment.

True or False

A

False

Some people learn more from punishment than from reward and vice versa

64
Q

“Punishment learners” are _____ at resisting temptation

A

Better

65
Q

“Go” pathway learners learn better from 1)______ than 2) ______

A

1) Rewards
2) Punishment
* “Go” pathway learners learn better from 1)______ than 2) ______*