evoked potentials (ep) (a.k.a. event related potentials, erp)

Evoked potentials (EP)(a.k.a. Event related potentials, ERP)

• Raw signal is “noisy” so we reduce noise by repeating stimulus and averaging potentials

• A time domain analysis

Time-locked presentations, repeated with EEG

EPs to test sensory pathway integrity

Letter = Positive or negative deflection

Number = milliseconds (or 100s ms) • Examples

– P300 can occur between 300-800 ms

– N400 may occur prior to it.

task deviant stimuli

Presentations and Responses

• Oddball

Oddball paradigm

• We habituate to regular stimulation– Any sound, image, pattern

• Oddball is the rare event

A A A A C A A [odd=C]

C C C A C C C [odd=A]

• Positive deflections

– P300

• Negative deflections– N100– N400

Atypical housing of language functions in autism

ERP reveals age, diagnoses

Kayser et al, in press

ERD – Event related desynchronization(frequencies may tell us more about mental

operations)

CSA – compressed spectral array

Time domain (ERP)vs Frequency domain (ERD)

task deviant stimuli

• Fewer trials needed than ERP

Assess extent of info processing

Diagnosing with ERD

Effect of sleep deprivation

Different neurophysiological operations reflected in different rhythms (thalamocortical, intracortical)

Topography reveals specific de/activation patterns

Leveraging functional laterality

ERD & PRS

Lie detection

Neuroimaging of Lie detection