EEG

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What do neurons do?
Align perpendicular to cortical surface, dendrites closer to the surface and axons to unite matter
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When is their firing of large neurons?
They can be recorded non invasively
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What is EEG generated by?
Post synaptic potentials
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When must activity occur?
In neurons where dendrites are closer to the surface, these neurons must fire together, this is when the signal is strongest
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What is the Berger effect?
The suppression of amplitude in response to eyes opening
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What are the Beta waves?
Most evident frontally dominant rhythm when subject is alert: eyes open
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What are alpha waves?
Occipital maximum dominant, when subject is relaxed with eyes open or the onset of mental effort
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What are theta waves?
Slow activity: Rare in adults when awake but perfectly normal in children (up to 13 years) and sleep
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What are delta waves?
Dominant rhythm in infants (up to 1 year olds) 3 and 4 of sleep
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What are event related oscillations?
Stimulus or task related changes in EEG oscillations in terms of frequency or amplitude: Temporal resolution tens to hundreds of milleseconds
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What are event related potentials?
Waveforms in terms of latency relative to an event such as a sensory stimulus
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When is it obtained?
Through time locked averaging of EEG; temporal resolution in tens of milleseconds
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What is the example of event related oscillations?
Lateralised occipito parietal alpha oscillations dining visual spatial attention regionally specific change to ongoing alpha oscillations
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What are ERPs?
Averaged EEG epochs
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What is recorded?
EEG trials, time locked to the event of interest
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What does each trial contain?
ERP and voltage fluctuations that are not time locked to an event
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What does Averaging increase?
the signal to noise ratio of the ERP signal
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Artifacts to be excluded from averaging are?
Movement of the eyeballs and muscle activity
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What are exogenous ERPS?
Automatic responses of the brain, controlled by physical properties of the stimulus
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When is it elicited?
Whenever modality - specific sensory pathway (auditory, somatosensory) is intact
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What is it influenced by?
Intensity/frequency of stimuli
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What is it important for?
Neurological diagnosis
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what do endogenous ERPS reflect?
Interaction between subject and event
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What is mesogenous?
Semi automatic but modulated by cognitive processes
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What is N100 connected to?
Selective attention
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What do stimuli differ along?
Two dimensions (Left, right ear) and pitch (low,high,tone)
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What is attended to?
Low tones in right ear
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What is the effect of attention?
Subtract respnses to standard tones in attended ear from resp. to standard tones in unattended ear
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What is concluded?
Effect of selective attention emerges as early as 100ms after stimulus
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What does N1p2 depend on?
Stimulus intensity Increase intensity and amplitude
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What is the rate of stimulus presentation?
Rate slowed increase amplitude
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What is topography?
Scalp distribution
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What is mismatch negativity?
Preattentive processing of deviant features, sensory memory or echoic memory
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What is shorter?
MMN latency, larger MMN amplitude
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What is MMN in patients with schizophrenia?
Decrease in MMN amplitude
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What is attenuation stronger for?
Duration deviants that for frequency deviants
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When else was there attenuated MMN?
In first degree relatives of schizophrenic patients who are at risk of developing schizophrenia
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What was found for MMN in children with dyslexia?
Decrease in amplitude and decreas in correlated to severity of dyslexia
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What are endogenous P300s related to?
Classic P3, 3B response to task relevant oddball stimulus
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What is it sensitive to?
Stimulus probability
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What is reflected?
Categorisation of stimuli
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What are novelty P3?
Responses to unexpected deviant stimulus
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What is an ommitted stimulus?
When expected stimuli do not occur
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What is endogenous ERPS?
Infrequently occuring targets, equally infrequent novel, environmental sounds
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p300 found in schizophrenics?
Reduced auditory P300 amplitude, reflecting impairment in sustained attention
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What is attenuated P300 also in?
First degree relatives of schizophrenic patients
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What is a task that will activate N400?
The pizza was too hot to drink, cry, eat, semantically incongruent
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What are movement related potentials?
Preceding voluntary movement RP, readiness potential
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What is contingent negative variation?
CNV in S1-2 paradigm, orienting wave, expectancy wave
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What is MEG stand for?
Magnetencephalography
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What is this?
Electricall activity in the brain generates magnetic fields
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They can be measured what?
Outside of the head
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Skull is what in magnetic field?
Transparent
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Better spatial resolution than what?
EEG, ERP
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MEG responses to stimuli through?
Averaging
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What does it require?
Low noise environmental, magnetic shielding
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Card 2

Front

When is their firing of large neurons?

Back

They can be recorded non invasively

Card 3

Front

What is EEG generated by?

Back

Preview of the front of card 3

Card 4

Front

When must activity occur?

Back

Preview of the front of card 4

Card 5

Front

What is the Berger effect?

Back

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