Thanks Christian. That really helps
Xuelin
****************************************
Xuelin Cui
Department of Electrical Engineering
University of Hawaii-Manoa
Honolulu HI 96822
Tel: 1-808-349-0983
Email: [log in to unmask]
****************************************
----- Original Message -----
From: Christian Beckmann <[log in to unmask]>
Date: Saturday, March 3, 2007 7:50 am
Subject: Re: [FSL] Are ICs orthogonal to each other?
To: [log in to unmask]
> Hi,
>
> nope, when using spatial ICA (as implemented in melodic) the time
> courses are not restricted to be orthogonal. The spatial maps,
> however, are not only orthogonal but are being optimised to be as
> statistically independent as possible. This is different from a
> PCA
> decomposition where both the time courses and the spatial maps are
>
> orthogonal and temporal ICA, where the time courses but not the
> spatial maps are orthogonal.
> The fact that time courses from spatial ICA are not restricted to
> be
> orthogonal presents a major advantage over PCA and temporal ICA as
>
> this makes it possible to extract effects like stimulus-related
> maps
> and separate these from temporally correlated effects like
> stimulus-
> correlated motion.
> hope this helps
> christian
>
>
>
> On 2 Mar 2007, at 19:58, Xuelin Cui wrote:
>
> > hi :
> >
> > I ran Melodic to fMRI data, which gave me a bunch of independent
>
> > components(ICs). I thought these ICs should be orthogonal to
> each
> > other since they are the eigenvectors of the covariance matrix.
> But
> > when I applied dot product to these ICs, I found the resaults
> are
> > not actually 0, which means these ICs are not orthogonal to each
>
> > other. I couldn't understand this. Are they supposeed to be
> > orthogonal? How do we get these ICs?
> >
> > Thanks a lot
> >
> > Xuelin
> >
> > ****************************************
> > Xuelin Cui
> > Department of Electrical Engineering
> > University of Hawaii-Manoa
> > Honolulu HI 96822
> >
> > Tel: 1-808-349-0983
> > Email: [log in to unmask]
> > ****************************************
>
> --
> Christian F. Beckmann
> Oxford University Centre for Functional
> Magnetic Resonance Imaging of the Brain,
> John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
> Email: [log in to unmask] -
> http://www.fmrib.ox.ac.uk/~beckmann/ Phone: +44(0)1865 222551
> Fax: +44(0)1865 222717
>
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