[Eeglablist] removal of event-related (time/phase-locked) variance from ongoing oscillatory activity (cf. Makeig '93)

[Alexander J. Shackman]

Hi --

We have an EEG dataset in which participants saw visual stimuli
approx. every 2 sec. In different blocks of the task, different
emotions were elicited. We're interested in examining emotion-related
(blockwise) changes in the tonic, ongoing alpha-band activity free
from the contributions of visual stimulus event-related (time and
phase-locked) activity.

One means of doing so would be to compute a mean ERP for each
combination of subject and emotion (block), and then perform a
regression to residualize the variance from each event-locked segment
that can be predicted by that individual's mean ERP during that block.
Examination of the pattern of correlations would also be infomative
about assumption violations (eg, changes in the single-trial ERP over
time might be revealed by a monotonic slope in the correlation coeff x
time plot).

My question is: Is this a reasonable means of removing event-locked
(time- and phase-locked) variance from the ongoing EEG record?

Thanks,
Alex Shackman
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Alexander J. Shackman
Laboratory for Affective Neuroscience | Waisman Laboratory for Brain
Imaging & Behavior
University of Wisconsin-Madison
1202 West Johnson Street
Madison, Wisconsin 53706

PH: +1 (608) 358-5025 (cell)
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EMAIL: ajshackman at gmail.com
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