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

Andre Achim achim.andre at uqam.ca
Tue Dec 20 11:48:56 PST 2005


I think you could perform ICA and remove the components that have a response
time locked to the visual stimuli.  This seems the most adapted solution to
your problem, assuming that the alpha modulation of interest is not from the
sources that respond to the stimuli.  This is unlikely the case.

A.Achim

-----Message d'origine-----
De : eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] De la part de Adrian Guggisberg
Envoyé : 16 décembre 2005 14:08
À : eeglablist at sccn.ucsd.edu
Objet : AW: [Eeglablist] removal of event-related
(time/phase-locked)variancefrom ongoing oscillatory activity (cf. Makeig
'93)

Hi

You can use intertrial variance described in:

Kalcher J and Pfurtscheller G. Electroencephalogr Clin Neurophysiol
1995;94:381-384
and
Klimesch W et al., Electroencephalogr Clin Neurophysiol 1998;108:123-130

Greetings
Adrian


-----Ursprüngliche Nachricht-----
Von: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] Im Auftrag von Alexander J.
Shackman
Gesendet: Donnerstag, 15. Dezember 2005 10:25
An: eeglablist at sccn.ucsd.edu
Betreff: [Eeglablist] removal of event-related (time/phase-locked)
variancefrom ongoing oscillatory activity (cf. Makeig '93)


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
------------------------------------------------------------------
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)
FAX: +1 (608) 265-2875
EMAIL: ajshackman at gmail.com
WWW: http://psyphz.psych.wisc.edu/~shackman |
http://brainimaging.waisman.wisc.edu/~shackman/

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