req code

[Robert Oostenveld]

Dear Shivaprakash

On 9 Mar 2005, at 13:01, Shivaprakash wrote:
> I am a student trying to implement in C the work done by-
>  Lehmann, D. and Michel, C.M. (1990). Intracerebral dipole source 
> localization for FFT power maps. Electroenceph. Clin. Neurophysiol. 
> 76, 271-276.
>   
> some how my programs are not working as explained in the paper. the 
> following web ID has the codes but not in source code.
>  http://www.puk.unibe.ch/tk2/Software.htm
>  
> if any one has done the implementation send a copy of the source code 
> to my ID. so that I can understand where I have gone wrong.

FieldTrip does implement frequency based source reconstructions using 
beamformer approaches, and frequency based dipole fitting in the way 
described by Lehman (1990) is not implemented in FieldTrip. Howvere, 
the method described by Lehman has subsequently been improved by 
Lutkenhoner and I suggest that you first look into that work:

Lutkenhoner B.
Frequency-domain localization of intracerebral dipolar sources.
Electroencephalogr Clin Neurophysiol. 1992 Feb;82(2):112-8.

If the implemented beamformer approach (see refs below) is not suitable 
for your data, then it would not be too difficult to implement a 
frequency based dipole fit algoritm based on the FREQANALYSIS and the 
DIPOLEFITTING code that is already present in our toolbox. However, 
FieldTrip is completely implemented in Matlab and not in C, and it will 
be a lot of work to reimplement it in C.

My old and unsupported MSA library does contain a  C-code 
implementation of the frequency dipole fit for EEG and MEG as described 
by Lutkenhoner, maybe you also want to take a look at that 
(http://oase.uci.kun.nl/~roberto/msa/)


best regards,
Robert


refs:
Gross J, Kujala J, Hamalainen M, Timmermann L, Schnitzler A, Salmelin R.
Dynamic imaging of coherent sources: Studying neural interactions in 
the human brain.
Proc Natl Acad Sci U S A. 2001 Jan 16;98(2):694-9.

Van Veen BD, van Drongelen W, Yuchtman M, Suzuki A.
Localization of brain electrical activity via linearly constrained 
minimum variance spatial filtering.
IEEE Trans Biomed Eng. 1997 Sep;44(9):867-80.