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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.
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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
Letter = Positive or negative deflectionNumber = 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] CCCA CCC [odd=A]
Positive deflections • P300 • Negative deflections • N100 • N400
ERD – Event related desynchronization(frequencies may tell us more about mental operations)
Time domain (ERP)vs Frequency domain (ERD) task deviant stimuli
Different neurophysiological operations reflected in different rhythms (thalamocortical, intracortical)