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