Is anyone out there using a non cephalic reference for EEG recordings using Biosemi and Brain Vision?
Many thanks for any comments.
Dan Zajdel
Oregon Health & Science University
Portland OR, USA
Implementing Non Cephalic Reference
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John Lumsden
- Posts: 2
- Joined: Fri Jul 09, 2004 1:55 pm
- Location: West London MH Trust
Lnked mastoid reference
I am hoping to use a linked mastoid reference on BIOSEMI and do the Analysis on Brain Analyzer.
At the moment I have 32 channels referred to right mastoid. Also record left mastoid referred to right mastoid and a channels below the right eye. In formula evaluation in BA I derive the 32 channels to linked mastoids (by subtracting 1/2 the signal between the mastoids from each channel) and the VEOG (Fp2-below eye) and HEOG (F7-F8 in 10:20 nomencalture).
To adapt this for a non-cephalic reference you would record to C7 (seventh cervical vertebra) amd also record betweem the sternum and C7. In BA you would subtract different proportions of the signal between sternum and C7 (measure the amplitude of the R wave component of ECG to get an idea of the amount of sternum-C7 signal to subtract) and use this in your formula to derive the non-cephalic reference
I would be interested in comments on my procedure
JL
At the moment I have 32 channels referred to right mastoid. Also record left mastoid referred to right mastoid and a channels below the right eye. In formula evaluation in BA I derive the 32 channels to linked mastoids (by subtracting 1/2 the signal between the mastoids from each channel) and the VEOG (Fp2-below eye) and HEOG (F7-F8 in 10:20 nomencalture).
To adapt this for a non-cephalic reference you would record to C7 (seventh cervical vertebra) amd also record betweem the sternum and C7. In BA you would subtract different proportions of the signal between sternum and C7 (measure the amplitude of the R wave component of ECG to get an idea of the amount of sternum-C7 signal to subtract) and use this in your formula to derive the non-cephalic reference
I would be interested in comments on my procedure
JL
Derived NC reference in BA
Yes, I've tried this procedure as well. I have found so far that the proportion of anterior electrode to posterior electrode that best minimizes the ECG artifact may differ from subject to subject or even from recording to recording. It is a bit of a headache right now in that I am experimenting with many different proportions for each subject in order to find the optimal balance. At some point we're going to write a function to do this in code.