[Mne_analysis] Baseline calculation

Stephen Politzer-Ahles politzerahless at gmail.com
Fri Mar 30 05:18:37 EDT 2012
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Hi Vancelette,

Is the time between the beginning of a sentence and a given trigger always
the same across items? (That should be the case if the number of words is
always the same and you used serial visual presentation; if the position of
a given trigger varies across items and/or you used auditory presentation,
though, then the latencies probably vary.) If this latency is always the
same then you can just add that latency to what the baseline interval would
be for each trigger. For instance, if the baseline for the first trigger
were -100 to 0, and the second trigger always appeared 800 ms after the
first, then the baseline for the second could be -900 to -800.

Best,
Steve

On Thu, Mar 29, 2012 at 10:42 AM, Vancelette, Reid Vincent <
RVANCELETTE at partners.org> wrote:

>  Hi all,****
>
> ** **
>
> I am currently in the process of performing preprocessing on my MEG/EEG
> data and am trying to correctly calculate a baseline. I am working with
> whole sentences that have several triggers within each sentence to mark
> particular areas of interest (for example: the noun, the verb). The current
> way that we calculate the baseline is from 100 ms before each of the
> triggers. Is there any way that I can calculate the baseline from the first
> trigger of each of the sentences (which happens to correspond to the
> beginning of the sentence) and apply that to each of the triggers within
> that particular sentence instead of having to calculate it 100 ms before
> each of the triggers? I am asking this because as of right now we are
> basically forced to calculate the baseline while the subject is hearing the
> sentences, which can bias the data. ** **
>
> ** **
>
> Thanks in advance,****
>
> ** **
>
> Reid****
>
> ** **
>
> Reid Vancelette****
>
> Research Assistant to****
>
> Dr. David Caplan M.D., Ph.D.****
>
>  ****
>
> Massachusetts General Hospital****
>
> Neuropsychology Lab****
>
> 175 Cambridge Street, Suite 340****
>
> Boston, MA 02114****
>
>  ****
>
> Phone: (617) 724-8846****
>
> Email: rvancelette at partners.org****
>
> ** **
>
> ** **
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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