[FieldTrip] No backprojection following ICA

[Peter Lyons]

Hello Jan-Mathijs,

Thank you for your response, I am glad to know that I needn't worry, and
really appreciate your time!

If at a later stage in my project I needed to compute leadfield matrices
for source localization, what steps would I need to take in order to do so?

Thanks,
Peter

On Fri, Jun 12, 2015 at 2:35 PM, Schoffelen, J.M. (Jan Mathijs) <
jan.schoffelen at donders.ru.nl> wrote:

>  Dear Peter,
>
>  Depending on what you want to do, you need or need not worry about the
> warning you get. Since you mention that in first instance you want to look
> at connectivity at the channel level, I think you are safe. The warning
> pertains to the application of the spatial transformation to the low-level
> description of the channel array (the elec-structure), and not to the
> actual data. In short, the back projection *is* applied to the data
> itself, but there is insufficient information available in the sensor
> description to be able to apply the same projection to this as well. The
> latter would be needed if at a later stage you want to do source
> reconstruction, for which you need to compute leadfield matrices, where the
> forward model should include information about the spatial topographies
> that have been removed.
>
>  Best,
> Jan-Mathijs
>
>  On Jun 10, 2015, at 2:00 AM, Peter Lyons <plyons at udel.edu> wrote:
>
>  Hello All,
>
>  My name is Peter Lyons, and I am a researcher at the University of
> Delaware.  Currently, I am conducting resting state EEG research with the
> intention of using Fieldtrip to calculate the power of different frequency
> bands as well as phase lag index between various sensors.
>
>  I have come across a problem when I attempt to call ft_rejectcomponent
> following an ICA of my data.  The ICA was performed using
> ft_componentanalysis, and the data was viewed using ft_databrowser to
> determine unwanted components.  Following these steps I ran this code:
>
>  cfg = []
> cfg.component = [3 5]
> data_clean = ft_rejectcomponent(cfg,data_ica)
>
>  which returned the following message:
>
>  "not applying the backprojection matrix to the sensor description"
>
>  My question is how do I proceed to allow the application of the
> backprojection matrix?
> I assume I am leaving some vital piece of code out?
>
>  Prior to calling ft_componentanalysis my continuous data was
> bandpass filtered using ft_preprocessing, and the reference was removed
> using the code:
>
>  cfg = []
> cfg.channel = {'all','-E65'}
> data_64 = ft_preprocessing(cfg,data_filt)
>
>
>  I am using an EGI Hydrocel 64 electrode Sensor Net and sampling at 1000
> hz.
>
>  Any advice would be greatly appreciated!
>
>  Thanks,
> Peter
>
>
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