[Eeglablist] Incorrect singal amplitude after loadavg

[Stephen Politzer-Ahles]

Hi Sanket,

EEGLAB's loadavg() function automatically scales the data into some units
other than microvolts; Neuroscan, on the other hand, represents the data in
microvolts. To load the data without scaling it (which is usually desirable,
since graphs in publications typically represent data in microvolts), you
can use Yang Zhang's loadavg_bcl() function, which is attached. Just save it
in the same folder where your EEGLAB functions are (I think it's the folder
called "sigprocfunc"), and then use it instead of loadavg().

Hope this helps,

Steve Politzer-Ahles


On Sat, Sep 3, 2011 at 2:00 PM, Sanket Jain <jainsanket1 at gmail.com> wrote:

> Hello experts,
>
> Yesterday, I downloaded the latest stable version of EEGLAB. I would like
> to read some .avg files from Neuroscan into MATLAB. I tried using the
> following loadavg function in EEGLAB. But there is a mismatch of signal
> amplitude between neuroscan and loadavg. Below are links to figures from
> both the software.
>
> EEGLAB-loadavg
>
> http://www.adrive.com/public/816d021415ff14b4ad2989ea39140523c1c55b98f533db1e650d33bddefbb66c.html
>
> Neurscan
>
> http://www.adrive.com/public/ab62848ced78e0a3b325033084c5691e02498e1d7be9f93578521c7bcc42c260.html
>
> It is possible that the header in the .avg file might be incorrect which
> could lead to incorrect amplitude interpretation by EEGLAB.
> Can some one help me figure out if the bug is within loadavg function or in
> my header information?
> Which header fields could cause this problem?
>
> Thank you in advance,
> Sanket
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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