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Psychophys EXAM > ERPs > Flashcards

ERPs Flashcards

1
Q

How do you measure ERPs and what are the assumptions of signal averaging?

A

derived from EEG recordings. Averaged brain electrical responses to a stimulus or cog event
Brains response to a stimulus is time-locked

Assumptions: the signal and noise sum to produce recorded activity
The signal is constant for each presentation
the noise is random

Averaging: trying to bring the signal forwards and get rid of noise

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2
Q

What are components and how are they quantified?

A

Waveforms have characteristic peak and troughs (components)
Quantified and taken as scalp level markers of underlying neural activity generating sensory and cog processes (used to process stem presented)

Quantified by:
Latency: interval between stimulus onset and peak
Baseline to peak: voltage diff, baseline= pre-stimulus activity
Also mean amplitude

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3
Q

How do characteristics of components differ?

A 
Modality stimulated: aud/vis/somat
Polarity: positive or neg deflection (AUS pos= DOWN)
Latency: time of peak
Scalp topography 
Experimental manipulation
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4
Q

What is the difference between exogenous and endogenous components?

A

Exogenous: sensory, automatic, occur early, linked to external stimulus (e.g. different depending on loud or soft)
Endogenous: cognitive, controlled, later =, linked to cog processing of stimuli

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5
Q

What are the advantages of ERP?

A

temporal resolution, spatial resolution, relatively low cost, administration simple, non-invasive

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6
Q

What is the N2 component and what does it represent?

A

Large negative deflection at about 200ms, occurs to stimulus requiring restraint/inhibition

Quantifiable phys marker of inhibition process. Allows for investigation of clinical groups, normal development

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7
Q

What is Mismatch Negativity?

A 
Negative component elicited automatically, detected even in absence of attention 
New stimuli (deviant) may differ from standard that precede in pitch, duration, intensity
Calculated by finding difference: ERP to standard- ERP to deviant

2 subcomponents/generators: supra temporal, frontal (main one)
Generated by oddball paradigm or roving paradigm

No. of standards increase= MMN increase
Sorter ISI decreases MMN

May reflect function of NMDA glutamate receptors as NMDA antagonists decrease MMN

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8
Q

What is a theory explaining Mismatch negativity and how can it be applied?

A

Regularity-violation interpretation: standard= not repetitive but regular relationship, deviant= regularity violation-> this new info needs MMN filter (represented by P3a- essentially shows attention switching)

Applied: Endophenotype for psychiatric disorders? Prodromal schiz (diff duration of MMN), chronic shiz (different frequency)

Coma recovery: present= 100% will wake up

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9
Q

What is the P50 component?

A

Positive component - represents inhibition of irrelevant input, paired click paradigm

Nicotinic acetylcholine receptors increase P50

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10
Q

How/when are ERPs represented in motor activity?

A

Voluntary movements: slow ne wave prior (readiness potential, large positive following movement

No pre-motion components with passive motor activity (therefore, related to voluntary prep)

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11
Q

What is the relationship between ERPs and reaction time?

A

Light flash stimuli-> press button
Larger amp P3 assoc with faster RT
Replication: stimuli not requiring motor response= larger P3 (P3 not due to motor requirement)

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12
Q

How does visual stimulation show hemispheric differences and what is inter hemispheric transfer?

A

Visual stimulation: amplitude increase in left hemisphere if stimulus presented in right visual field
Also shorter latency in contralateral hemisphere (contralateral processing idea)

Inter hemispheric transfer= time taken for signals to cross over from primary to secondary hemisphere (via corpus callous) Estimated 10-20ms according to ERP measures (more accurate than RT studies)

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13
Q

What are sleep spindles and the K complex?

A

Sleep spindle: inhibitory process to stay asleep: non-threatening env stimuli

K complex: suppress cortical arousal in response to stimuli sleeping brain evaluates as not dangerous, aids sleep-based memory consolidation

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14
Q

What is the String Hypothesis relating ERPs to intelligence and is it credible?

A

Hendrickson and Hendrickson
IQ positively related to complexity of ERP trace, stretch like a string and measure length (longer= higher IQ)

No its dumb af
oversimplified, relies on amplitude too heavily

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15
Q

How does P300 relate to intelligence?

A

GPA increase = shorter P3 latency (timing of P3 related to cog ability) used aud oddball (attention but not intellectually demanding)

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16
Q

Explain olfactory ERPs and how they may be applied.

A

Smell stimuli-> small ERP (from stim)
As concentration of odour increases so does ERP amp

Aud processes in Alzheimers no different by Olfactory are (could be helpful)

17
Q

Explain gustatory ERPs and why their unusual.

A

control (water), sweet, salty, sour, bitter all show early components. Salty and sour show late wave but not in sweet and bitter (why?) -> possibly due to smaller surface area (distribution) of sweet and bitter receptors -> smaller cortical response

Methodologically challenging

18
Q

How have ERPs and Attention been assessed using different paradigms?

A

Previous: ^ amp to attended vs ignored stimuli but stimuli presentation was regular (know it was coming) so differences may have been related to arousal/anticipation

New paradigm: unpredicted delivery, random ISI, high load (no ERP differences between relevant/irrelevant atom)

Selective attention paradigm: found Nd (negative difference)

MMN functionally linked to attention

19
Q

What are late components and what are their proposed functional values?

A

Take longer to develop than sensory/motor, are endogenous (attribute meaning)
RP (intention to move)
CNV (expectancy regarding occurrences of stimulus)
P300 (decisions, ?)

20
Q

What is Contingent Negative Variation, what does it reflect and what does it look like?

A

Long lasting negative shift, develops between warning stimulus (s1) and second stimulus (s2)

Reflects state of expectancy (how brain prepares for s2 they know is coming)

If there is a long interval between stimuli then CNV show early and later portions: Early (O wave/orientation), Later (E Wave/Expectancy)

Two wave shapes: A fast rise (when uncertain about timing of s2/early prep), B Slow rise time (more certain, know when to get ready)

21
Q

How may CNV be applied?

A

CNV can occur in absence of motor response-> not purely due to motor activity
inverted U -CNV and arousal (lowered at high aousal due to distraction)

Presented male, female and neutral silhouettes - overall larger CNV to opposite sex or neutral
Use to assess sexual object preference of sex offenders?

22
Q

What is the Bereitsachaftspotential (readiness potential) and how is it different form CNV?

A

500-1000ms prior to voluntary and spontaneous movements
RP: initiating vol movement, CNV: prep for stem know is coming
Different scalp topography: RP= central and strongly lateralised

23
Q

What is the P300?

A

most investigated, late positive ERP to task-relevant stimulus. Latency mediated by processing attributes of stimulus high=late
Largest deflection in waveform-> initial interest , functionally important, cog process indicator
Primary driver of presence= task relevance from experimental stimulation

24
Q

For the P300 what paradigms are used/do they all show the same thing?

A

Many different ones can show P3 but we don’t know if they are all functionally indicative of same thing.

Large P3 associated with many diff things including stimuli detected with confidence, memory recalling things etc. Function would have to include all

25
Q

What is Donchin’s Context updating theory of P3?

A

QUANTIFIABLE INDICATION OF MEMORY UPDATING
P3 about context updating and WM related process
-Attributes of standard stimulus in oddball context are maintained in working memory and comparison of any incoming to that- if different then contexts needs to be updated and neuronal representation will occur as P3

26
Q

What is Kahneman’s Resource allocation theory of P3?

A

ALLOCATION OF ATTENTIONAL RESOURCES
Primary driver of amp and latency= arousal- influences ability to engage and allocate attention/resources, interaction between arousal and attention allocation and demands of task which lead to variations in P3 amplitude (and latency to small extent)
Undemanding task: amp large, latency short
Demanding: amp smaller, latency longer as processing resources are used for task performance as task demands more

Psychophys EXAM (6 decks)

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