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MC > Task 3 > Flashcards

Task 3 Flashcards

1
Q

Name facts about EEG:

A
  • measures electrical activity of the brain revealing some properties about mental stats (sleep memory attention)
  • High temporal resolution poor spatial resolution
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2
Q

Name The Set up of an EEG

A
  • Non invasive electrodes are placed on the scalp
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3
Q

What does the EEG meassure ?

A
  • Synchronized synaptic activity

- > activity of large group neurons that acre active at the same time

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4
Q

What is the EEG used for?

A
  1. Detects abnormalities in brain function
  2. Ongoing EEG
    - > Subjects are usually not doing anything
    - > It is the search of a particular state (dowsiness)
    - > Neurofeedback (sport)
  3. EEG response to stimuli
    - > ERP
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5
Q

What are limitations of EEG ?

A
  • > Reveals little information about cognitive processes

- > because the recording tends to reflect the brain’s global electrical activity

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6
Q

What are certain measurement issues off EEG ?

A
  • Noise / artifacts
  • > External noise / Extraphysiological artifacts
  • > Internal noise / Physiological artifacts
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7
Q

What is meant by noise ?

A

-> Voltage that reflects sources outside the brain

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8
Q

How is the noise level being meassured ?

A
  • Signal to noise ratio

- The higher the SNR the better the Signal

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9
Q

What is meant by external noise ?

How can it be reduced ?

A

Defintion:
-> Noise produced outside the body ( wires in wall or fly)
Reduced:
-> Shielding: a piece of metal surrounding the region to be measured which cancels out electromagnetic radiation
-> Active electrodes: Using an amplifier close to the electrodes

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10
Q

What is meant by internal noise ?

How can it be reduced ?

A

Defintion:
-> Noise produced inside the body (eyeblink)
Reduction:
-> Can not be eliminated just minimized via controlling the environmental factors

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11
Q

Whar are other method to reduce noise ?

A

-> Remove very slow & very fast voltage changes, as they are likely to be due to noise (against internal noise)
-> Use an active and a reference electrode to identify how much noise exist
• Reference electrode should always be placed on the mastoid bone
-> Use a pre stimulus baseline period

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12
Q

Name facts about ERP:

A
  • > Electrical potentials generated by the brain which are related to specific internal or external event
  • > ERPs are extracted from the EEG signal over many trails and averaged
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13
Q

What are ERP being used for ?

A
  • > identifies how brain activity changes in response to a particular task
  • > temporal resolution
  • > Identify cognitive processes
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14
Q

Where should ERP not being used?

A
  • > Does not answer neruroanatomical questions
  • > No deception
  • > Averaging process must be doable
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15
Q

Where is a ERP Method in particularly used ?

A
  • > infants and young children
  • > these individuals have relatively poor control over their behavior, ERPs can reveal mental processes that are difficult to assess behaviorally
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16
Q

Which synaptic potentials are being meassured within an EEG?

A
  • > Postynaptic potentials

- > Action potentials are to fast to be meassured

17
Q

Explain how we meassure an EEG signal

A

-> Look at the task sheet

18
Q

What is a dipole ?

A

-> oriented flow of energy (looks like a cycle)

19
Q

Is one dipole enough for an EEG signal ?

A
  • > no it is about summation of many dipoles

- > linear superpostion

20
Q

How is a dipole constructed ?

A
  • > Source: region of positive (extracellular) charge /negatively intracellular charged
  • > Sink: region of negative (extracellular) charge / positive intracellular charged
21
Q

What do the electrodes meassure ?

A
  1. The activity of the active electrodes in voltage = the weightes sum of activity from all dipoles
  2. The activity of the reference electrodes in volatge
    - > mostly placed on mastoid bone to have no brain actvity
22
Q

What are the assumption which must be met in order for an electrode to detcet the activity of a dipole ?

A
  1. Neurons must be synchrously active / have similar input
    - > All neurons are negtaivley charged on the dendrites and positively charged on the cell body
  2. Neurons must be arranged in a parallel fashion
23
Q

What two types of orientaion exist ?

A
  • Radial dipoles
  • > are located in the cerebral cortex, they are perpendicular to the cortex
  • Tangetial dipoles
  • > are oriented parallel to surface
24
Q

What and How does the signal reach the electrode ?

A
  • Tissues of the brain, skull, and scalp passively pass on the electrical impulse
25
Q

What are ERP components?

A
  • > Are voltage deflections seen as peaks
    1. Exogenous sensory components
    2. Endogenous components
    3. Motor components
26
Q

What is meant by Exogenous sensory component ?

A
  • > triggered by the presence of a stimulus
  • > everything below 150 ms
  • > N1 P 1
  • > Prior to 100 ms is sensory processing
27
Q

What is meant by Endogenous compoents ?

A
  • neural processes that are entirely task dependent
  • Everything above 150 ms
  • P2 P3 N4
28
Q

What is meant by motor components ?

A
  • execution of given motor response

- RP = readiness potential

29
Q

Name two additional components ?

A
  • MMN = mismatch negativity

- ERN = error related negativity

30
Q

How is a component constructed ?

A
  • The polarity = P I N

- Number indiacting peak latency (ms) or number indicating the corresponding order

31
Q

What is meant by volume conduction ?

A
  • It is the process of passing on electrical currents (ions) trough extracelluar space
  • > Rule: Pool of positive ions repeal pool of negative ions and visas versa
32
Q

What is meant by capacitive conduction ?

A
  • > It is the process of passing on electrical currents (ions) trough insulating layers
  • > The positive ions at the one side of the insulating layer repel positive charges on the other side of the insulating layer
33
Q

How is each EEG signal meassured ?

A
  • Look at waveforms
    -> Speed = slow vs fast
    -> Amplitude = High vs Low
    Example:
    -> The more exited = the smaller and faster are the waves

-> The less excited = the larger and slower are the waves

34
Q

Explain a Topographic Map:

A
  • > Positive voltage is indicated as red
  • > Negative voltage is indicated as blue
  • > Tiny black dots represent the electrodes
  • > The stronger the color the closer the dipole or the stronger the signal
35
Q

How are the electrodes placed ?

A

According to the 10 & 20 System:

  • > nasion (deepest point just above the nose),
  • > inion (small bony bump at the back of our head
  • > Divide distance in 10 & 20 % parts
36
Q

What do the letters / Numbers represent in a topographic Map ?

A
  • > The letter stands for the Lobes or central sulcus
  • > Number represent the distance from midline ( 1 is close 5 is far)
  • > odd numbers = left Hemisphere
  • > even number = right hemisphere
  • > Z = Zero electrode is on the midline
37
Q

What is meant by overt attention

A

-> attending to a stimuli with moving head

38
Q

What is meant covert attention

A

-> attending a stimuli without moving head

39
Q

Which two components reval that attention follows an early selection method ?

A

-> N1 and P1 !! = selective attenttion

MC (9 decks)

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