Modular EEG Differential Channels

Hi,
I'm planning to buy the Olimex EEG-SMT, but before that I want to understand 
the design better. I'm not a Neuroscience person, and I don't know much 
about EEGs, so bear with me if I've missed something obvious.

The Channels seem to be differential in that they measure the difference 
between a pair of electrodes. I'm confused about the rationale behind this. 

If it's only for noise reduction won't a common reference (for all 
channels,) or something like the DRL itself, be good enough? 

And what do I get if for example one electrode is at Fp1 and another at Fp2? 
It's not simply the difference in left and right hemisphere activity because 
from what I understand of the problem of source localization, there is a lot 
of mixing. Isn't there an analogy about a cocktail party?

The design doesn't seem optimal for what they call a daisy-chain 
configuration either. A simple shorting option between neighboring electrode 
sockets would have helped if that was the intent.

I am not complaining about the design at all, the folks at openEEG have 
clearly put in a lot of hard work. It's just that I'm convinced that there 
is a logic behind this design feature, and I'm not able to understand it.

The way I'll probably end up using it is by using a common reference for the 
-ve sockets of each channel, but that seems to be a waste of electrodes. Of 
course I could use a common electrode and split the signal, but that might 
just weaken it too much.

Any help would be awesome.
Cheers,
Nishant




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