[Eeglablist] eBridge Implementation Question

[Matthew Stief]

Hello Everyone,

I am seeking some advice of using the eBridge algorithm developed by Daniel
Alschuler and others at the New York State Psychiatric Institute
psychophysiology lab.  I tried to contact Daniel by e-mail but can't find
any current contact information.

http://psychophysiology.cpmc.columbia.edu/software/eBridge/

http://sccn.ucsd.edu/pipermail/eeglablist/2013/007148.html

Has anyone else used this algorithm to detect bridging?  Does anyone have
any particular views on the strengths or weaknesses of this method for
flagging bridged electrodes?

described here:
http://psychophysiology.cpmc.columbia.edu/software/eBridge/tutorial.html

Applying it to my data I am finding extremely high hit rates for most of my
participants, in the range of 30-50% for most.  Unfortunately I find this
sad result plausible, as I used a high density 128 channel array, and think
I probably did apply gel too liberally.

One specific question that I would appreciate input on is that for some of
my participants eBridge flags zero channels as bridged when it is applied
to the continuous data.  I found this suspicious, so I tried to apply it
after extracting epochs, and for that data it returns the typical ~35% of
electrodes bridged.  I am not well versed enough in EEG theory to have any
intuition about why this might be the case.  Does this sound plausible?
Why might eBridge fail to flag any electrodes on the continuous data, and
flag a bunch on the epoched data?  I re-ran eBridge on several other
datasets where eBridge returned substantial bridged electrodes on the
continuous data, and re-running it on the epoched data for those
participants returned the expected identical bridged electrodes.

Any suggestions would be appreciated!  Thanks for your time in advance!
_________________________________________________________________
Matthew Stief
Human Development | Sex & Gender Lab | Cornell University
http://www.human.cornell.edu/hd/sexgender

One ought to know that on the one hand pleasure, joy, laughter, and games,
and on the other, grief, sorrow, discontent, and dissatisfaction arise only
from the brain. It is especially by it that we think, comprehend, see, and
hear, that we distinguish the ugly from the beautiful, the bad from the
good, the agreeable from the disagreeable.
-Hippocrates

Is the blood the element with which we think, or the air, or the fire? or
perhaps nothing of the kind--but the brain may be the originating power of
the perceptions of hearing and sight and smell, and memory and opinion may
come from them, and science may be based on memory and opinion when they
have attained fixity.
-Plato
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