AW: [Eeglablist] alpha like noise

Sarnthein Johannes Johannes.Sarnthein at
Wed Oct 19 00:16:32 PDT 2005

Hi Maarten,
You are probably looking at real data, leave it in.
There are several reports of cognitive alpha processes,
for example in expectancy and also working memory.
See some references below.

Petsche H, Kaplan S, von Stein A, Filz O.
The possible meaning of the upper and lower alpha frequency ranges for cognitive and creative tasks.
Int J Psychophysiol. 1997 Jun;26(1-3):77-97.

Von Stein et al.

von Stein A, Sarnthein J.
Different frequencies for different scales of cortical integration: from local gamma to long range alpha/theta synchronization.
Int J Psychophysiol. 2000 Dec 1;38(3):301-13
Jensen et al

Klimesch Group

Basar Schurmann Group

and some others

-----Ursprüngliche Nachricht-----
Von: eeglablist-bounces at [mailto:eeglablist-bounces at] Im Auftrag von Maarten Mennes
Gesendet: Dienstag, 18. Oktober 2005 11:32
An: eeglablist at
Betreff: [Eeglablist] alpha like noise

Dear all,

During some of the tasks we used in our lab we encountered a sort of alpha-wave-like noise in our EEG-data (see figures in attachment).  
However, subjects were fully awake and had their eyes opened.

This alpha-noise was sometimes stimulus locked as in the attached figure, however, most of the time present in clear bursts. In addition this noise was not always limited to the posterior channels where you would expect the true alpha waves.

We did try a number of techniques in order to filter this noise out, but did not succeed. ICA for example could not confine this noise to one component.

Has anyone else on this group encounterd this kind of noise in your data and if so, what did you do in order to prevent or filter out these wave-patterns?

Would using more electrodes than the current 19 enable ICA to isolate this noise in more confined components?

yours sincerely,
Maarten Mennes

Maarten Mennes
Ph.D. Student
Laboratory for Neuropsychology
Department of Pediatrics
UZ Gasthuisberg, O&N
Herestraat 49
3000 Leuven


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