[Eeglablist] Question regarding color interpretation

Pål Gunnar Larsson pall at ous-hf.no
Mon Sep 21 00:47:10 PDT 2015

The image is indeed from Besa Dipoel simulator. I used this to give a simple model example of the possibility of opposite polarity over the two hemispheres. I think it would be worth while to sit down and play with the simulator, and even move the results to Besa Research.

I thought about pointing to the video (http://sccn.ucsd.edu/eeglab/TwoSourceEEG12.mp4 )  on EEGLabs front page (http://sccn.ucsd.edu/eeglab/ ), but the video has a more complex content.

Pål G. Larsson M.D., PhD.
Head of Clinical Neurophysiology
Department of Neurosurgery
Division of Surgery and Clinical Neuroscience

Oslo University Hospital
Po.box 4950 Nydalen
0424 Oslo
Tel:  (+47) 23074407
Mobile: (+47) 93429791
E-mail: pall at ous-hf.no<mailto:pall at ous-hf.no>
not sensitive

Fra: Frank Duffy [mailto:fhd at sover.net]
Sendt: 20. september 2015 21:50
Til: Pål Gunnar Larsson; 'Fang-Yu Chang'; eeglablist at sccn.ucsd.edu
Emne: Re: [Eeglablist] Question regarding color interpretation

The image provided was created artificially in the BESA dipole simulation program which I believe may be downloaded from the BESA.de website if you would like to pursue your own dipole simulations.

The "source dipole" is shown by a red dot with a line. A dipole is like a small battery with positive and negative ends. The line represents the positive end and the line also shows the source orientation/direction. As different ends project to different hemispheres, the hemispheres show different polarities (red positive, blue negative). As the source is placed near the midline, source voltage projects to both hemispheres. Source projections are also shown as waveforms upon the scalp to the right. Note that the display polarity is positive up, unlike standard EEG which shows negative up.

Most sources are near cortex with greatest amplitude over the nearby scalp. Projected activity to the other hemisphere is low amplitude, usually hidden by other activity in that hemisphere BUT sources always project in opposing directions, one end positive and one end negative.


Frank H. Duffy, MD
fhd at sover.net<mailto:fhd at sover.net>

[cid:image001.png at 01D0F449.D53B5610]

Dr. philos. Pål G. Larsson
Seksjonsleder Klinisk nevrofysiologi
Nevrokirurgisk avdeling
Oslo Universitetssykehus
Postboks 4950 Nydalen
0424 Oslo

Tlf.:  23074407
Mobil: 93429791

E-mail: pall at ous-hf.no<mailto:pal.gunnar.larsson at ous-hf.no>

Denne meldingen innholder ikke sensitiv informasjon som bryter med Ous sine regler for taushetsplikt

Fra: eeglablist-bounces at sccn.ucsd.edu<mailto:eeglablist-bounces at sccn.ucsd.edu> [mailto:eeglablist-bounces at sccn.ucsd.edu] På vegne av Fang-Yu Chang
Sendt: 14. september 2015 14:28
Til: eeglablist at sccn.ucsd.edu<mailto:eeglablist at sccn.ucsd.edu>
Emne: [Eeglablist] Question regarding color interpretation

Dear EEGLAB users,

I have a question regarding the scalp map color bar. I have read the following webpage:


Based on my understanding, red and blue both indicate activation, but opposite polarity. My question is, if there's an event that results in one side of the brain having red readings while the other side has blue readings, how would this data be interpreted?


Stella Ling


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