[Eeglablist] Channel location and reference

[Brittany Alperin]

Hi Hoorisa

You'll need to create your own channel locations file and apply that to the data before referencing. If there are any extra channels showing up that you didn't record from, just delete them, but make sure you're deleting the right channels. The biosemi website has the coordinates for each electrode. That should be a good starting point. The eeglab wiki has some information on how to create these files. 

The reference is extremely important for analysis. You'll need to know where the mastoid electrodes are being plugged in on the amp itself during recording. If they are plugged into the EXG7 and 8 spots, then reference to EXG7 and 8. 

I hope this was somewhat helpful.

Brittany

> On Jun 23, 2015, at 2:21 AM, Hoori Sa <hoorisa33 at gmail.com> wrote:
> 
> Hi 
> 
> Sorry for long email but this is because I couldn't attach photos and also very confused!
> 
> I'm new to EEGlab and can't see channel labels because the data I'm analyzing gathered with 32 channel cap and BIOSEMI but there are extra channels up to 45 and I don't know if my analysis would be OK if I drop some of channels. 
> 
> my problem starts when I go to ''dataset info'' in menu and want to add ''channel location'' which is in the sample folder of eeglab.
> 
> I don't have enough information abou the data just I know reference is ''mastoid electrodes'' and while importing I choose channel 37 & 38 (As for EXG7 & 8), tho I'm not sure if it can be EXG5 & 6 or how important is the reference for analysis. 
> 
> Now I don't know which electrode to put as reference, as in EEGLAB in the start the reference should be defined. Then when I choose 37 & 38 at first as reference I can't see channel location and I receive an error ''edit dataset info'' and the only thing missing is there is ''channel location file or info''. The real problem starts when I choose the 32 channel location in the ''sample_data'' and after that, in my data set info I see ''unknown'' as for my reference and also ''channel location'' in ''plot'' menu turn to disabled.
> 
> Then I want to do ''re_reference'' and channel info close to ''Re-reference data to channels'' doesn't give me channel list and I put 37 & 38 as reference and of course I check the ''retain old ...'' box, then I have again ''unknown'' for my reference!
> 
> Then I gave up and continue with disabled items in my plot menu such as ''channel location'', ''channel ERP image'', etc. 
> 
> Again while I plot channel spectra and maps (the very few items available to me), I have a saw like signal not like normal signal without 2-D head maps (just power-frequency graph) and I can not edit frequency ranges to plot.
> 
> Please help me with this. I got stuck and can't go forward. 
> 
> Best,
> Hoorisa
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