Event-related potentials (ERPs)
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Event-related potentials (ERPs)
Jarrod Blinchmotorbehaviour.wordpress.com
May 31st, 2011
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Type of electrodes
• Non-polarised silver-chloride (Ag/AgCl)• Tin• Gold or platinum
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How many trials?
• EEG 50 uV• ERPs – 60 trials for large component (~10 uV, P300,
RP/LRP)– 150 medium (~5 uV)– 400 small (~1-2 uV)
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Overview• Event-related potentials (ERPs)• Advantages and disadvantages• ERP components and waveform peaks• Strategies to interpret ERP components• Quantifying noise• Components
– Readiness potential (RP, LRP)– P300 (P3a, P3b)
• Fractionating information processing– Osman and Moore, 1993 (LRP)– Luck, 1998 (P3b)
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Event-related potentials (ERPs)
• Averaging to generate ERPs• Tiny effects• Relying on previous ERPology• Reliability– Low within-participant variability– High between-participant variability
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Advantages and disadvantages
Advantages• Continuous measure of
processing• Independent of a
behavioural response• Evoked or emitted
potentials• Noninvasive• Temporal resolution
Disadvantages• Functional significance• Tiny effects• Spontaneous or induced
potentials• Spatial resolution• Peaks versus components…• Latency jitter…
Stimulus identification
Response selection
Response programming
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Imperativestimulus
Responseinitiation
Reaction time
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ERP components and waveform peaks
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Strategies to interpret ERP components
1. Focus on a specific component2. Use well-studied experimental manipulations3. Focus on large components4. Isolate components with difference waves5. Focus on components that are easily isolated6. Use component-independent experimental
designs7. Hijack useful components from other domains
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Quantifying Noise
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Overview• Event-related potentials (ERPs)• Advantages and disadvantages• ERP components and waveform peaks• Strategies to interpret ERP components• Quantifying noise• Components
– P300 (P3a, P3b)– Readiness potential (RP, LRP)
• Fractionating information processing– Osman and Moore, 1993 (LRP)– Luck, 1998 (P3b)
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P300
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Readiness potential (RP)
Early RP
Late RP
MP
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Lateralised readiness potential (LRP)
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Stimulus identification
Response selection
Response programming
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Imperativestimulus
Responseinitiation
Reaction time
P300 LRP
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Psychological refractory period
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Bottleneck
Stimulus onset asynchrony (SOA)
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Osman & Moore, 1993
Stimulus identification
Response selection
Response programming
LRP
Stimulus identification Bottleneck Response
selectionResponse
programming
Stimulus identification
Response selection Bottleneck Response
programming
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* *L
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Luck, 1998
Stimulus identification
Response selection
Response programming
P300
Stimulus identification and Bottleneck Response selection
Response programming
Stimulus identification Response selection and Bottleneck Response
programming
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Event-related potentials (ERPs)
Jarrod Blinchmotorbehaviour.wordpress.com
May 31st, 2011
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