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MC > Task 7 > Flashcards

Task 7 Flashcards

1
Q

Explain the assumptions of fNIRS:

A
  1. Active areas need Oxygen
  2. Oxygen is carried by Hemoglobin
  3. Hemoglobin absorbs light in a banana shaped way
  4. Oxygenated HB and deoxygenated HB blood have different optical properties -> They absorb different wavelength
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2
Q

What are the different optical properties of Oxygenated and Deoxgynated blood ?

A
  • > Oxygenated = 850
  • > Deoxyenated = 760
  • > in general it is the range bewteen 700 -900 nm
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3
Q

Describe the Method of fNIRS:

A
  • > 2 types of wavenlgth inform of near infrared light are introduced by the brain
  • > Photons pass trough tissues and are then absorbed by Oxy or Deoxy hemoglobin
  • > After absorption the rest of the photons will be refelected
  • > The more Oxy is present the less 750 wavelength will be reflected
  • > Based on the difference (how much came in and how much came out) we can estimate which regions were active
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4
Q

What is an important rule of fNIRS ?

A

-> When less Oxy will be reflected then more deoxy will be reflected

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5
Q

What are the limitaions of fNIRS?

A

-> Does only measure surface brain tissues 2-3 mm

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6
Q

What is an optode ?

A

= light source of fNIRS

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7
Q

What do you need for an fNIRS scan ?

A

-> Optode + detector

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8
Q

What happens if we vary the distance between optode and detector ?

A
  • > Higher distance = more depth
  • > Higher distance = less quality signal
  • > Usually placed 2-7cm away from Optode
  • > best is 3 cm
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9
Q

What is meant by event related optical signal ?

A

-> Measure change in optical properties at cell membranes themselves
-> more a direct meassure (better temporal resolution)
BUt lower SNR

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10
Q

What are more preceise fnirs method and why ?

A
  1. Frequency domain systems
  2. Time-resolves systems
    - > both use leaser (more dangerous and expensive larger)
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11
Q

What is a less preceise fnirs method and why ?

A
  • > Continuous wave (CW)
  • > Since it uses light instead of leaser
  • > Cheaper / smaller / less dangerous
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12
Q

Name some Pro of fNIRS:

A
  • > Two Dependent variables
  • > Save / non invasive
  • > Low coast
  • > Portable
  • > Can be integrated with other technologies
  • > No vulnerability to electromagnetic environment
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13
Q

Name some Con of fNIRS:

A
  • > Light scattering / absorption by Skin / hair
  • > Limited spatial resolution only reaching surface
  • > Can not do comparisons of fNIRS data between subject
  • > Limitations in the use of cranial reference points
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14
Q

What does fNIRS and fMRI have in common ?

A
  • > Indirect meassurments

- > Both achived similar outcomes

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15
Q

Why is fNIRS worse then fMRI ?

A
  • > Lowers spatial resolution

- > Limited to outer cortex

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16
Q

Why is fnirs bettern then fMRI ?

A
  • > Portable / People can do whatever they want
  • > Cheap and quiet
  • > Can be intergreatd with other methods
  • > Can use metal
  • > Ecological validity (real world environment testing)
17
Q

What is BCI ?

A

-> System connects a brain with a computer without involving any peripheral nerves and muscles

18
Q

What can BCI systems do ?

A

-> Allows for controlling external devices trough brain activity , assisting, replacing cognitive sensory or motor functions

19
Q

What is the Method of BCI ?

A
  • > Measure brain activity via EEG or fMRI
  • > Feature / Signal extraction
  • > Signal are translated into a set of rule based algorithm -> Into a machine command
  • > Command then gets passed on to the computer
20
Q

What is a danger to BCI ?

A
  • Low SNR can lead to wrong commands
21
Q

How do we overcome a low SNR ?

A
  • > Via neurofeedback training -> learn in realt time to change brain activity in desired direction
  • > Machine learning algorithms improve accuracy of prediction
22
Q

Name the two methods which are used as signals

A
  • > Direct encoding (worse)
  • > Indirect encoding (better)
  • > Both make use of Spatial features/temporal features and magnitude features (certain lvl of brain actvity)
23
Q

What is meant by direct encoding?

A
  • > brain activity of answering yes or no

- > Bad because = they are heavily correlated therefore not differentiated

24
Q

What is meant by indirect encoding ?

A
  • > Subsitude Yes resopnse with a mental motor actvity
  • > subsitute no response with a inner speach
  • > Basically making use of higher order cognitive processes
25
Q

What is currently the accuracy of BCI ?

A

-> 70 %

26
Q

What are some applications of BCI ?

A
  • > locked in syndrome = detecting conscious awareness in non-responsive patient
  • > brain signals that an individual can intentionally generate to encode an intention
27
Q

What is meant by the univariate general linear model ?

A
  • > Single channel of interest is determined

- > Has to calculate a cut of value

28
Q

What is meant by the multivaraite General linear Model ?

A

-> Uses all channels
-> Doe not require calculation of cut of value
-> Uses a support vector machine as classifier of a signal
o Which needs to be trained

29
Q

How can the BCI be used in combination with EEG ?

A
  • > Can use P 300 component

- > Can use Slow cortical potentials & steady state visual-evoked potentials

30
Q

How can the BCI be used in combination with MEG ?

A

Real time BCI

  • > Can use P 300 component
  • > Can use Slow cortical potentials & steady state visual-evoked potentials
31
Q

How can the BCI be used in combination with fMRI?

A
  • > Automated interpretation & classification of activation maps
  • > Neuronfeedback
32
Q

How can the BCI be used in combination with NIRS ?

A

-> motor imager or P 300

33
Q

How to claculate the concentration of Oxygenated and deogynated blood ?

A

-> via the Lambert beer law

34
Q

What is one unique benefit of fnirs over fMRI ?

A

-> Fnirs meassures both oxygenated and deoxygenated concentration while fmri only meassures oxygenated concentration

35
Q

What is BCI used for ?

A
  • > Repearing
    -> supporting
    -> Replacing
    cognitive function !
36
Q

Method of BCI 2.0

A 
Signal acquisution (EEG / FMRI) 
Signal processing (Signal extraction + transforming algorithm)

MC (9 decks)

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