ERP Averaging









Auditory Oddball

EEG/ERP sweeps of vertex surface potentials (gif file 322 kB)

EEG activity [µV] of one healthy individual, recorded at the vertex electrode (site Cz) with a nose tip reference (positivity is plotted downwards). The task was to listen to a series of complex tones, and to press a button after infrequent (target) events and to ignore frequent (nontarget) events. Shown are data of 64 consecutive trials in each condition, time-locked to stimulus onset (sweeps of 1,280 ms length, including a 200 ms pre-stimulus baseline). The brown lines represent the raw EEG activity recorded for each event, the blue lines are the running ERP averages, which include all previous events. EEG sweeps were low pass filtered at 20 Hz (24 dB/Oct). For this recording, it took about 10-20 trials to establish a fairly stable ERP component structure, consisting of N1 (peak latency approximately 100 ms), P2 (180 ms), N2 (220 ms), and P3 (300 ms). N2 and P3 are typically found only for the target condition. Note that unsystematic EEG activity (e.g., during the pre-stimulus baseline period) averages to zero with a suffcient number of recorded sweeps. © Kayser 11/29/2001

EEG/ERP sweeps of right parietal surface potentials (gif file 240 kB) To view similar running averages for visual stimuli, click here.


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