Re: EEG While Meditating

Hi Michael

What type of LightStone have you got, is it the blue one?  I
reverse-engineered the blue one many years ago and know for a fact that it
uses DC to do the GSR, or the more modern term is SCL, measurement.  But
there is a IOM interface that is more expensive and uses galvanic
isolation.  It is possible that this IOM unit uses AC excitation for it's
GSR/SCL measurement.

If you use DC, it shouldn't interfere with your EEG recordings, but if it
is AC you an possibly expect interference.

AC excitation for GSR is obviously the best method to use but because it is
technically more difficult few people bother.

Talking about interference, one should also be careful of using AVE
equipment with EEG.  The sound is no problem because it runs typically at a
few 100Hz which is outside the EEG range.  But what **CAN** be problematic
is running the wires of the LED goggles close to EEG wires.  The LEDS are
normally pulsed at highish currents of perhaps 100mA or even more.  They
are also pulsed in exactly these low brain-wave frequencies.  The the
induced voltages lie exactly in the middle of the EEG spectrum.

I don't say you can't use AVE with EEG amps, all I am saying there is the
potential for interference and one should check for this.

Regards
Stefan

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