[Mne_analysis] Grand Averaging from Text Events Files

[Hari Bharadwaj]

Hi Brian,
   Is the normal averaging (as opposed to grand averaging) working as
expected for the individual runs with the behavioral corrected event
files?

Regards,
Hari


On Wed, January 25, 2012 12:37 pm, Brian Coffman wrote:
> Hello MNE users,
> I am having an odd issue that I am having trouble conceptualizing.
>
> I am averaging data that is split into 3 raw data files, then taking the
> events files generated from these averages and modifying these events
> files
> to include only events where the subject responded correctly. I am then
> taking these corrected events files and grand averaging the raw data to
> end
> up with a single .fif average which is corrected for our behavioral data.
>
> The issue I am having is related ot the initial offsets in the events
> files. In all cases, there is an initial offset greater than zero for the
> 2nd and 3rd raw data files. In some cases, there is also an initial offset
> of a few seconds in the events file for the first of the three raw data
> files. It seems from the log files that the offset is being utilized
> differently for the two cases (a few seconds offset vs a whole dataset
> offset). For the log from the first file, the offset is added to the
> times,
> while for the other files, the offset is not added. For example, with an
> initial offset of 4 seconds, the log for the uncorrected average starts at
> 29.555 seconds, while for the corrected data, the log starts at 33.555
> seconds. The logs are identical for the second and third data files. This
> is also apparent in the averages, as there is no signal in the corrected
> average of the first raw file. It seems that the offsets are necessary for
> the later files (data files 2 and 3), however, as I get no averages
> without
> them.
>
> My question is: Should I eliminate these offsets from the first text
> events
> file when averaging from events files? Is there something I have not
> considered here?
>
>
> Thanks in advance!!
>
> -Brian Coffman, M.S.
> Research Associate, The Mind Research Network
> Doctoral Candidate, The University of New Mexico
>
> Phone: (505) 336-0606
> Fax: (505) 272-7011
>
> "I used to think that the brain was the most wonderful organ in my body.
> Then I realized who was telling me this."
>   - Emo Phillips
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-- 
Hari Bharadwaj