Re: question about 10-20 map

Bias and reference electrodes are typically placed on the ears with ear clip electrodes, or behind the ears on the left and right mastoids.

An EEG measures the volume conduction of a large amount of (mostly) pyramidal neurons, mostly located in the cortex.

You are measuring the voltage difference between the reference electrode and the channel electrode. You are not measuring "across" anything; you are "comparing" the voltages at two specific points. Across would imply that there was some sort of current flow between those two points when in fact there is not, it's merely measuring voltage at two separate points. Do a little more research into voltmeters, volume conduction, and the 10-20 system.

Regarding your bonus question, measuring at O1 and O2 are generally good locations to test if your system is working well - try detecting alpha waves when you close your eyes.

Cheers,
John Ruelas

> On Aug 5, 2015, at 12:16 PM, wikitronic <[email protected]> wrote:
> 
>  I am not sure about where to place electrodes. Do you pick any two positions for each measurement are there preferred electrode locations for certain measurements? Would it be beneficial to put one electrode where you want to measure and try different locations for the second? From what I understand I am trying to measure the polarity of the cells so this would mean I want to measure across the target location. This could mean vertically or horizontally too though. 
> 
> 
> Bonus question. 
> 
> What are some interesting electrode position measurements for a beginner?
> 
> Thanks
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