ERPs 5 Flashcards
Write brief notes on ERPs and taste.
Compared water, sweet, salty, sour, and bitter stimuli. All stimuli showed an early component, makes sense as it is sensory registration. Only salty and sour showed a late wave.
Therefore it is not an oddball effect as the oddballs would be sour and bitter.
Why no late components to sweet and bitter?
Small surface area for these -> smaller cortical response
Methodologically challenging. Where do you deliver those stimuli if you want the same proportion of receptors?
Write brief notes on ERPs and attention.
Increased amplitude ERP to attended vs. ignored stimuli. However, stimuli presentation was regular, differences may be related to arousal.
New paradigm: unpredictable, random ISI, can’t predict when the stimulus is coming, high load (fast presentation rate). No ERP differences to relevant vs. irrelevant stimuli using this paradigm. With differential preparation controlled, no ERP difference
What is Nd
Negative difference= measure of attention (attended-unattended waveform)
What are the 3 late ERP components
RP, CNV, P300
Describe contingent negative variation (CNV).
CNV is what happens in the brain when somebody is getting ready to respond to a stimulus. Can occur in the absence of motor response so it is not purely due to motor activity
- Long lasting negative shift
- Develops between warning stimulus (S1) and second stimulus (S2)
- Reflects state of expectancy
- Reflects increased cortical excitability
Ability to see how people cortically prepare for the oncoming stimulus
- Early component – O wave (orientation)
- Late component – E wave (expectancy
There are two types of CNV wave shapes:
- Type A: fast rise time (when subject is unsure about when S2 would occur). Not very efficient, using up resources
- Type B: slow rise time (subject more certain).
Measure arousal through CNV-arousal relo (CNV amp decreased to very high or very low arousal)
Describe the readiness potential (RP).
It is the preparation to act.
Occurs 500-1000ms prior to voluntary and spontaneous movements.
It is a measure of activity in the motor cortex and supplementary motor area of the brain leading up to voluntary muscle movement.
Do the CNV and RP differ? If so, how?
- They have vastly different scalp topography. RP is more central and strongly lateralised. RP is not evident in the frontal area, which CNV is.
- Simple vs. complex movements – RP wider scalp topography for complex relative to simple movements. For complex movements= early frontal RP, indicating the planning of a skilled motor act
Also eliciting paradigm is diff
Write brief notes on the P300.
Occurs to significant info
Amp increase to:
- Second of two rapidly presented stimuli, if second stimulus allows decision to be made
- Stimuli detected with confidence vs. less so
- Infrequent vs. frequent stimuli
- Subsequently recalled words vs. words not recalled
Difference between p3a and p3b
p3a= infrequent novel stimuli, distraction stimulus, e.g. unpredictable shift in tone frequency regardless is paying attention (frontal) p3b= infrequent target stimuli, unaffected by background noise e.g. tone change when ur paying attention (parietal)
Describe context updating theory of P3 (Donchin, 1981)
Input -> different stimulus? (to whats in wm)
If yes -> neural representation, P300
If no -> N1/P2, N200
- If the stimulus is the same, neuronal model of the stimulus remains unchanged = sensory components
- If the stimulus is different = attentional resources allocated, NM is updated = P3b
Describe the model of resource allocation (Kahneman, 1973).
System is modulated by overall arousal level. This governs the amount of attention available for task performance. P3 represents allocation of attentional resources
- Undemanding task: amplitude is relatively large and latency short
- Demanding task: amplitude smaller and latency longer as processing resources are used for task performance
- Passive tasks: smaller P300 because stimulus and non-task events engage resources to reduce amplitude
