[FieldTrip] Beamformer for ERP data

[Johanna Zumer]

Dear Imali,

In addition to Stan's good advice, you might also find better results by
computing the covariance matrix from the unaveraged timelocked data, rather
than the averaged ERP data.

Cheers,
Johanna


2013/3/28 Pelt, S. van (Stan) <stan.vanpelt at fcdonders.ru.nl>

> Dear Imali,
>
> What you could do is the following:
> 1. determine the source of your activation by beamforming your 50ms
> time-interval data, or by doing a dipole fit on your ERP.
> 2. compute spatial filters at that location based on the covariance matrix
> of the data of the entire epoch you're interested in (e.g., 500ms pre until
> 500ms post stimulus onset). You could consider first bandpassing this data
> for the part of the spectrum that you are interested in (e.g. 13-28Hz for
> beta).
> 3. create the virtual waveforms by multiplying the spatial filters with
> the band-passed data
>
> Hope that helps.
>
> Best, Stan
>
> --
> Stan van Pelt, PhD
> Postdoctoral Scientist, Ernst Strüngmann Institute (ESI) for Neuroscience
> in Cooperation with Max Planck Society
> Deutschordenstr. 46, D-60528 Frankfurt
> Phone:  +49 (0)69 96769 517
> Fax:      +49 (0)69 96769 555
> www.esi-frankfurt.de<https://email.gwdg.de/owa/redir.aspx?C=DWQc6llvR0GmBNf16RzxtXd9GZAf_88IQCBDBgVoq2hPZhfpSS2vw1Gyk8XqewAjG7dhzVLAIBs.&URL=http%3a%2f%2fwww.esi-frankfurt.de%2fpublications%2ffries-lab%2fdr-stan-van-pelt%2f>
>
> ------------------------------
>
> *Van: *"IMALI THANUJA HETTIARACHCHI" <ith at deakin.edu.au>
> *Aan: *fieldtrip at science.ru.nl
> *Verzonden: *Donderdag 28 maart 2013 01:04:34
> *Onderwerp: *[FieldTrip] Beamformer for ERP data
>
>
>  Dear Fieldtrippers,
>
>
>
> I am trying to do a LCMV beamformer analysis using the ft_sourceanalysis
> for a ERP data set.  Finally I intend to extract the source waveforms using
> virtual electrodes.
>
>
>
> But as we can only do meaningful source localisation for a small time
> interval say (50ms), how can I construct the source time course for a
> longer  post stimulus period (say 500ms)after doing beamforming for shorter
> (50ms) time intervals?
>
>
>
> Many thanks in advance
>
>
>
> Kind regards
>
> Imali
>
>
>
> *Imali Thanuja Hettiarachchi*
>
> PhD Candidate
>
> Centre for Intelligent Systems research
>
> Deakin University, Geelong 3217, Australia.
>
>
>
> Mobile : +61430321972
>
> Email: ith at deakin.edu.au
> www.deakin.edu.au/cisr
>
>
>
> [image: Description: Description: Description:
> cid:1216BE20-1800-4A47-8B9F-E7B9D94831CD at deakin.edu.au]
>
>
>
>
>
>
>
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