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Models of Brain Function > Week 3: Working Memory Model = CHECKED > Flashcards

Week 3: Working Memory Model = CHECKED Flashcards

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1
Q

Taxonomy of memory diagram:

A
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2
Q

declarative memory

A

It refers to memories which can be consciously recalled/declared such as facts (semantic memory) and events (episodic memory)

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3
Q

short-term memory (STM) is

A

Keeping a small amount of information in mind and making it accessible for a short time.

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4
Q

Example of STM (working memory/WM)

A

As an example of working memory, a new phone number is kept in mind until it is dialed and then immediately forgotten.

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5
Q

capacity of short term memory

A

7 +/- 2

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6
Q

STM and WM often used

A

interchangeable but defined differently

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7
Q

The mechanism of loss in STM is

A

Primarily decay

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8
Q

We are consciously aware of STM meaning we can

A

We can cognitively manipulate the contents of STM in our head and actively rehearse them

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9
Q

Capacity of LTM

A

High

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10
Q

Mechanism of loss in LTM is

A

interference

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11
Q

interference theory is theory

Due to structure (2)

A

the theory that people forget not because memories are lost from storage but because other information gets in the way of what they want to remember

It is due to the structure of brain (e.g., overlapping representations of the memory in the brain

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12
Q

According to the interference theory,

A

Individuals forget LTM memories caused by memories interfering and disrupting one another (Baddley, 1999)

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13
Q

Are we consciously aware of LTM?

A

Yes

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14
Q

Decay

A

When information is immediately forgotten when it is no longer needed/relevant in that moment

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15
Q

Working Memory Model was made by

A

Baddeley and Hitch (1974)

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16
Q

central executive maintains and manipulates STM in WM model

A

memory contents

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17
Q

More specifically,

central executive drives

directs (2)

A

drives the whole WM system

It directs attention and processing to the different subsystems its connected to: visuospatial sketch pad and phonological loop

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18
Q

phonological loop is where information is

WM model

A

acoustically coded

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19
Q

phonological loop is part of WM

WM

A

the part of working memory that holds and processes verbal and auditory information

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20
Q

visuospatial sketchpad where info is stored and processed in WM

A

visually or spatially.

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21
Q

Information in visuospatial sketch pad is visually in WM

A

coded

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22
Q

In a task, where letters are presented visually, participant’s show errors that indicate information is acoustically coded, for example:

A

they replace T for G (both sound similar) instead of Q for G (appearance of letters look similar)

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23
Q

Similarly, pps found recalling a wordlist more difficult for similar sounding words and not semantically related words, for example: (after research replace T for G)

A

recalling ‘rice’ instead of ‘ice’ instead and not recalling ‘frost’

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24
Q

Research of replcating T with G and pps difficulty recalling ‘rice’ instead of ‘ice and repeating nonsense syllables disrupts phonological memory implies that (2)

A

WM system is not unitary

is a multi-component system with modality specific components , each can be damaged separately.

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25
Q

Each component of WM can be damaged separately:

Phonological WM deficits

For example, damage to Brodman areas 44 and 40 means that (2)

A

individuals can not hold strings of word in their memory/mind
there will be deficit in the rehearsal process of phonological loop

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26
Q

Each component of WM can be damaged separately:

Visuospatial sketchpad WM deficits

Damage (i.e., lesions) to parieto-occipital causes deficits in visuo-spatial WM for example:

A

pps with that damage have difficulties in memorising and repeating a sequence of blocks experimenter has touched

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27
Q

Support for the dissociation of both visual (i.e., visuospatial sketch pad) and auditory (i.e., phonologcial loop) WM - (3) in PET scans

A

This is because there is changes in local cerebral blood flow (PET) in different areas of the brain when participants doing verbal and spatial WM tasks in healthy participants

For Auditory WM tasks: activity in infero-lateral

For Spatial WM tasks: occipital, pariteral, inferior frontal (most RIGHT of the brain)

28
Q

In Lisman-Idiart Model, neural model of WM, they put forward that

A

a neural mechanism called ADP helps to carry out WM maintenance

29
Q

ADP stands for

A

afterdepolarisation

30
Q

Purpose of the model

In Lisman-Idiart Model, we do not need to think about

A

which ion channel is in charge of ADP

31
Q

Purpose of the model:

In Lisman-Idiart Model, they want to model

we don’t care about (2)

A

ADP effect on MP

we don’t care about the ion channels

32
Q

Equation of the model

In previous lecture we introduced: integrate and fire model equation as:

if u = urest then…

A

if u = urest (inputs are 0) then rate of change is 0 so stay at resting M

33
Q

Equation of the model

In Lisman-Idiart Model,

u =… (change of MP over Dt)

They have other

(2)

A

V

they have other contributions of voltage in change of MP/dt

34
Q

Equation of the model

In Lisman-Idiart Model, Vinh is

A

The input from inhibitory interneuron which is assumed and not modelled explicitly

35
Q

Equation of the model

In Lisman-Idiart Model, Vinh is added

A

every time an AP (i.e. spike) is fired by the pre-synaptic neuron

36
Q

Equation of the model

In Lisman-Idiart Model, Vosc is

A

a sin function to cause some membrane potential fluctuation in the background (as observed in real neurons)

37
Q

Equation of the model

In Lisman-Idiart Model, Vrest is

A

Resting MP

38
Q

Purpose of the model and equation

For the Lisman-Idiart neural model, it does not

simplify say after integrating inputs into the equation whether

(2)

A

calculate the (shape) AP

AP is fired or not

39
Q

ADP hump in MP diagram

A
40
Q

ADP

In depolarisation, (3)

A

the membrane potential (voltage) increases (e.g.., -70 to 64 mV)

More likely to emit a new spike

Excitatory inputs have this effect

41
Q

ADP

Hyperpolarisation is when (3)

A

membrane potential (voltage) decreases and becomes more negative (e.g., -70 to -75 mV)

The neuron is further away from the firing threshold

AHP and inhibitory synapses have this effect

42
Q

The ADP is a positive ‘hump’ in MP after

A

each spike

43
Q

ADP

Lisman and Idiart model ADP as (2)

A

being similar to a weak synaptic input

Modelled mathematically as an alpha function

44
Q

ADP

The ADP hump is not due to the (2)

produces after

A

product of synaptic activity

Produces after each AP and is due to a specific ion channel (we don’t care what channel that is in this model) that operates late.

45
Q

ADP and Purpose of the model

Lisman and Idiart model:

But did you not say we need HH model to model ion channels? (2)

A

This is because model does not give us an explanation of ADP

In this model, however, they use ADP use this to explain a higher-level phenomena

46
Q

Purpose of the model

The aim of the Lisman and Idiart model is to (after saying not use HH model)

A

demonstrate what ADP can be used for and its effect on MP

47
Q

Purpose of the model

A full HH model would be completely unnecessary for Lisman and Idiart model as (2)

A

this complexity does not fulfil the aim of Lisman and Idiart’s model

This is because would not add how ADP functions in terms of networks of neurons

48
Q

Research working on source of ADP in terms of ion channels will need what model?

A

HH model

49
Q

Research working on what ADP is useful for in a neuron, what model will they use?

A

Integrate and fire model = Lisman-Idiart model

50
Q

Purpose of the model

Lisman and Idiart model is like a modified

A

integrate and fire model

51
Q

In Lisman and Idiart model, threshold and V rest (resting MP) is… (2)

A

Threshold = -50 mV
Vrest = -60 mV

52
Q

Diagram of input terms (V rest, VOSC, VADP, Vinh) effect on MP:

A
53
Q

Lisman-Idiart model network (4)

A

Activity of each prefrontal neurons is calculated by the equation change of MP over time

VOSC provides excitatory oscillatory input to the neurons

Vinh has feedback inhibition circuit

If vOSC neuron fires a spike exciting all the prefrontal neurons, eventually transmitted to Vinh neuron which inhbits all neurons including itself

54
Q

Assume that the firing of each neuron in the Lisman -Idiart model network represents one item in the WM

HOW….?

For example,

In other words…

(2)

A

These neurons can quickly create a synaptic connection with neuron in phonological loop which encodes and represents the letter ‘G’

In other words, part of phonological loop that represents ‘G’ makes a particular neuron

55
Q

Assume firing of each neuron in Lisman-Idiart model network represents one item in WM? HOW….? = Synaptic connection with neuron in phonological loop which encodes G so

Both oscillatory inputs and ADP maintains (after example of letter G that create synaptic connection)

A

spiking

56
Q

part of the phonological loop that represents ‘G’ makes a particular neuron in the network fire AP and the neuron fires another AP after a while due to

A

due to both oscillatory inputs and ADP mainting spiking

57
Q

Assume Firing of each neuron in the Lisman-Idiart model network represents one item in WM

(after osciliatory inputs in combination of neuronal properities maintain spiking)

HOW…

It can only (2)

A

fire so many spikes in an oscillation cycle

suggesting WM has limited capacity

58
Q

Assume Firing of each neuron in the Lisman-Idiart model network represents one item in WM HOW…

(after osciliatory inputs in combination of neuronal properities maintain spiking, can only fit so many spikes)

Once activity of neurons (i.e., spiking) in Lisman-Idiart neural network is absent, the content of the STM (item)

A

cannot be recovered

59
Q

Proposed mechanism of
Lisman-Idiart Model Network of WM
(4)

Combination of oscillatory input + ADP to maintain letter ‘G’

Neural mechanism for active rehearsal for content of WM

A
  1. There is background oscillations in neural network
  2. A particular neuron in network representing letter’ G’ fires AP due to an external input (e.g., presented with letter G)
  3. That neuron inhibits itself and all other neurons in network (feedback inhibition circuit)
  4. Next peak of oscillation comes around, ADP has raised MP high enough for that neuron to fire another AP
60
Q

With the Lisman-Idiart model network we have the neural mechanisms

for example…

A

for active rehearsal of content of WM –> repeating firing of neuron represring ‘G’, F,S,W,A,M,R for example

61
Q

The Lisman-Idiart model provides a neural mechanism for the active rehearsal of WM content using the

each on its own is…

(2)

A

neural properties (ADP) and network properties (feedback inhibition circuit and oscillatory input among different cells) that make this possible

each on its own is insufficient

62
Q

We can not add more and more neurons that have the capacity to hold long strings in WM promptly because

The background oscillation has a fixed frequency, which means that… (2)

A

. the distance in time between two peaks of the oscillatory input (Vosc) is fixed

only fit so many spikes and ADP into one oscillatory cycle

63
Q

The background oscillation having fixed frequency meaning we can only fit so many spikes and ADP into one osciliatory cycle

Therefore..

A

WM capacity is limited in this model, as it should be.

64
Q

An example of WM is limited (7+/- 2 items, Miller et al., 1956)

Trying to memorise a list of words: GPSWAMR then the letter X is added before G

If you try to fit another spike (i.e., AP) that represents the letter ‘X’ then the feedback inhibition circuit will silence the

A

previously active neuron that spikes for letter ‘R’

65
Q

Advantages and benefits of Lisman-Idiart model of WM (2)

A

The model demonstrates how neuronal prosperities (ADP) and network structure (feedback inhibition and oscillatory input) work together to implement function

A criticism is that the authors chosen parameters (e.g., oscillation frequency) to make the number 8 for capacity.

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