[FieldTrip] Beamformer confusion

Tyler Grummett tyler.grummett at flinders.edu.au
Thu Jun 26 10:00:31 CEST 2014

?Hello Fieldtrip,

I have been using the LCMV beamformer in fieldtrip for some time now, so I have experience with it.

I am facing an issue where whatever data I process I get an image identical to attachment 'sourceplot.png'. We have tried visual SSR, memory tasks, tactile tasks etc.

Also, whatever I do with the data, the same issue occurs (filtering etc).

Attachment 'original_data.png' shows the data before going into the beamformer, and 'virtual_data.png' shows the data after it has run through beamformer.

We have tried filtering in every possible combination ie lowpass = 40/30/20, highpass = 1/10/20, we even did a highpass of 100 and it

was still identical.

We dont think this is a fault of the beamformer, but we cant work out how to get rid of the issue. It is overpowering the other data.

We have also had a look at some spectra of the brain region with the high power and a brain region that doesnt have the high power and it appears

as though there is higher power over all frequencies.

Before asking:

-There isnt any muscle, the data was recorded from a paralysed person.

-We have tried it on CAR'd data and data that hasnt been CAR'd

We are all out of ideas.

Kind regards,



Tyler Grummett ( BBSc, BSc(Hons I))
PhD Candidate
Brain Signals Laboratory
Flinders University
Rm 5A301
Ext 66124
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