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Re: Request for information on ICA-Maximum likelihood approach

Doesn't that kind of negate the whole purpose of ICA?  It's supposed to find the dimensions that PCA might miss.  But if you do a PCA first, all you will get out are subsets of the dimensions the PCA finds in the first place.
Brian Gygi, Ph.D.
Speech and Hearing Research
Veterans Affairs Northern California Health Care System
150 Muir Road
Martinez, CA 94553
(925) 372-2000 x5653
-----Original Message-----
From: Linda Seltzer [mailto:lseltzer@xxxxxxxxxxxxxxxxxx]
Sent: Friday, April 9, 2010 09:47 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: Request for information on ICA-Maximum likelihood approach

I should add that when ICA is used in fMRI (e.g. the use of fast ICA in Brain Voyager), PCA is used first for dimensionality reduction. Linda Seltzer > Hi Vijay, > > I'm not sure you could start a Matlab script from scratch to do ICA > with Maximum likelihood approach. As far as I've gathered, there's > quite a lot of (heavy) maths involved to find equivalent ways to write > the initial ICA assumptions - like minimizing the maximum likelihood > contrast function. Most of the different ICA implementations start > from maximum likelihood (or similar criteria) and differ in the > strategies they've used to actually allow calculation. (Does it make > sense?)... > > That said, apart from the link given by Taylan and Linda, Tony Bell > has interesting demos and papers (I'd recommend Bell and Sejnowski, > 1995) available on his website: > http://cnl.salk.edu/~tony/ica.html > You might also find JADE (see Cardoso, 1999) or Fast-ICA (see > Hyvarinen & Oja, 2000) Matlab implementations interesting "to play > with" : > > http://www.tsi.enst.fr/icacentral/algos.html > http://www.cs.helsinki.fi/u/ahyvarin/papers/fastica.shtml > > Best regards, > Idrick > > Quoting Vijaykumar Peddinti : > >> Dear All, >> >> This is might be a silly question. But I am trying to do a small >> project on separating signals using Independent Component Analysis >> (ICA) Maximum likelihood approach for my class. So far the articles >> I found leave me with more questions than answers. I have never done >> anything with ICA before. I am lost in the process of finding the >> information. >> >> It would be of great help if anybody could point me in the correct >> direction or send me an basic Introductory paper/tutorial (if >> possible) on ICA (Maximum likelihood approach). I am not trying >> anything fancy, I am trying to get a basic simulation working in >> MATLAB. >> >> Thank you very much. >> >> Best Regards, >> Vijay >> >