evoked potentials (ep) (a.k.a. event related potentials, erp)
Post on 02-Jan-2016
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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
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