phase

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This leads me to a question I've had for awhile, might belong on the BioExplorer list. What do the phase data results in BioExplorer mean? For example, a score of -7.

Is that channel 2 subtracted from channel 1?

And what is being subtracted from what? Is channel 2, seven somethings behind channel 1?

What is the signficance, if any, of a plus score vs. a minus score?

What kind of score indicates very out of phase (180?), very in phase?

Are there any indications as to what are desirable phase scores at particular sites or in particular situations?

Foxx

-----Original Message-----From: [mailto: ] On Behalf Of Van DeusenSent: Friday, February 03, 2006 9:00 PM Subject: Re: Re: Increasing coherence?Larry,I'm far from being an expert in this area myself, but a few comments:> What said seemed basically correct to me; but I would add that inter-hemispheric training, or for that matter any form of bi-polar recording, is likely to affect coherence - but also may not even when the similarity between two sites is affected. Actually what the bipolar training, interhemispheric or not, is most likely to affect is PHASE, not coherence. When two signals are in phase, subtracting one from the other will result in a very low value; when they are 180 degrees out of phase, it will result in a large value. So, in addition to training down the difference in raw amplitude, it is highly likely that downtraining bipolar signals will move the signals IN phase and uptraining them will move them OUT of phase. Since coherence is independent of phase, it will not necessarily be affected.> I think one factor that favors the use of bi-polar, one channel recording is that it by-passes the contaminating effect of the 2 reference recording sites that are used in 2 channel coherence training, one for each of the 2 "active" recording sites. . These effects can be large. One particularly huge effect that should be totally avoided is using a linking connector to provide the same reference to each channel. This greatly elevates coherence values because the linkage of the references automatically makes the two signals more similar.Here I would disagree and say that when comparing two sites against a common reference actually INCREASES the quality of the reading, since we are truly comparing what is happening at the two sites, independent of what might be happening differently at the two reference sites.Pete