Methods: EEG flashcards 1

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  • Created by: CanveySam
  • Created on: 02-05-15 11:31
List 5 advantages of EEG
1) Excellent time resolution 2) Direct indicator of neuronal activity 3) Multidimensional 4) Portability 5) Relatively inexpensive
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List 3 disadvantages of EEG
1) Not well suited for precise functional localisation 2) Not suited for deep brain structures e.g. putamen or thalamus 3) not suited for slow/fluctuating processes
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What does an EEG reflect?
Differences of electrical potential over time, created by the current flows from neuronal populations
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Name two types of neuronal electrical activity
Action potential (AP) and Post synaptic potential (PSP)
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What do chemical synapses do?
They cause local changes in postsynaptic membrane potentials, through neurotransmitters
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Name two types of post-synaptic potential (PSP)
Excitory PSP and Inhibitory PSP
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Name two types of summation
Spatial summation and temporal summation
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What is spatial summation? Describe in two sentences.
The summing of potentials that come from different parts of the cell. If the overall sum (of EPSPs and IPSPs) can depolarise the cell at the axon hillcock, an action potential will occur.
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What is temporal summation? Describe in two sentences.
The summing of potentials that arrive at the axon hillcock at different times. The closer together in time that they arrive, the greater the summation and possibility of an action potential.
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How is summation related to EEG?
EEG signals ar primarily produced by summation of postsynaptic potentials of millions of neurons.
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What can't EEG measure? (give 3)
1) all neural events 2) isolated synaptic events 3) very slow or very high fluctuations 4) deep brain structures
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What materials are used for EEG electrodes?
conductive: silver, tin, gold cap and electrode gel
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EEG placement: What do Fp, C, O, T, P stand for?
Frontal pole, Central, Occipital, Temporal, Parietal
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EEG placement: Are the LH numbers odd or even?
Odd
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EEG: Standard number of electrodes?
64 (32-64)
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3 step procedure of active electrode placement
1) place head cap 2) apply electrode gel 3) connect electrodes
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What are the names of the three electrodes used in differential amplifiers?
1) Active electrode (A) 2) Reference electrode (R) 3) Ground electrode (G)
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EEG: What does a ground electrode do?
Eliminate ambient noise
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EEG: Where is a reference electrode placed?
1) Neutral e.g. tip of nose, earlobes, mastoids, chin) 2) convenient/comfortable 3) no hemispheric bias
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Name four types of filters
1) Low pass (100 Hz) 2) High Pass (0.5 Hz) 3) Band pass 4) Band stop/notch (50 Hz)
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EEG: Why filter? (give 2 reasons)
1) Reduce artefacts 2) Avoid aliasing
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EEG: What is aliasing?
when sampling frequency (fs) is less than 2 x maximum frequency (fmax)
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EEG: when should sampling frequency occur?
should be fs> 2fmax. Usually fs > 5fmax
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Name two ways of dealing with artefact elimination?
Artefact rejection and artefact correction
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Expand on artefact rejection
ie 'brute force approach' (e.g. if over 75-100 uV) e.g. for blinking, eye movements, electrode shift
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Limitations of artefact rejection (3)
1) can lose large amount of data 2) some tasks call for artefacts 3) some participants are prone
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Name 2 simple and 2 advanced methods of artefact correction
simple: 1) subtraction method (variance based) 2) filtering; advanced: 1) dipole 2) Independent component analysis (ICA)
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List ways to minimise artefacts
1) Request no blinking or include blink pauses 2) ensure participants are relaxed 3) carefully apply electrodes 4) maintain cool temp and low humidity 5) electrical screening of testing space (Faraday cage)
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List the frequencies of 5 waves from Delta to Gamma
Delta 30Hz
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Name 2 applications of cognitive EEG research
1) Tasks with long duration stimuli 2) Monitoring sleep stages
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Name 4 applications of clinical EEG research
1) epilepsy investigation 2) diagnose sleep disorders 3) measure effect of drugs 4) detect brain death
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What do EP and ERP stand for?
Evoked potential and Event Related potential
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What is the difference between EP and ERP?
EP: perception and clinical research; ERP: experimental cognitive research
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What are ERPs?
Waveforms, characterised by a series of positive (P) and negative (N) deflections at different latencies
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What are the names of two ERP components?
Exogenous (external) and Endogenous (internal)
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5 Advantages of ERP
1) Simple and fast to compute 2) require few analysis/parameters 3) has high temporal precision/accuracy 4) provides a good quality check 5) mature literature
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What is the ERP hypothesis?
ERP is a signal (s) that appears superimposed and without interaction on the background or ongoing EEG which is considered random noise (n). After averaging across trials, noise will cancel out and only the event related EEG response will remain.
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Give 4 assumptions of ERP
1) ERP is uncorrelated with background EEG 2) Background EEG is random 3) Background EEG varies across trials 4) ERP is invariant across trials
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How many ERP trials?
As many as possible! Suggest 50 trials/condition/participant
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Describe 2 main limitations of ERPs
1) Interpretational issues e.g.null results, does not capture phase locked results 2) limited opp to link results to neurophysiological dynamics
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What are VEPs and how can they be applied?
Visual Evoked potentials eg clinically in assessing MS, optic legions
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Give 2 advantages and 2 disadvantages of time frequency representations
Ad: clear interpretations, covers more multidimensional space; Disad: decreased temporal precision, complicated analysis
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Name 4 measures of non-linear neuronal synchrony
1) nonlinear correlation 2) information theory 3) phase synchrony 4) generalised synchrony
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Name 2 measure of linear neuronal synchrony
1) linear correlation 2) coherance
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Other cards in this set

Card 2

Front

List 3 disadvantages of EEG

Back

1) Not well suited for precise functional localisation 2) Not suited for deep brain structures e.g. putamen or thalamus 3) not suited for slow/fluctuating processes

Card 3

Front

What does an EEG reflect?

Back

Preview of the front of card 3

Card 4

Front

Name two types of neuronal electrical activity

Back

Preview of the front of card 4

Card 5

Front

What do chemical synapses do?

Back

Preview of the front of card 5
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