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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 >