Hi Dr. Beckmann,
I think there all the spatio-temporal ICs are orthogonal since FastICA
strictly constrains independent components to be orthogonal. That is:
(a1*c^Tc2*a2^T) = 0 because c1^Tc2=0, where a1 and c1 are time course
1 and spatial component 1, similar definition for a2 and c2. And the
noise subspace is orthogonal to the ICs due to PCA.
Where can we have non-orthogonality in this model?
Best,
Leo
On Wed, Aug 4, 2010 at 11:16 PM, Christian F. Beckmann
<[log in to unmask]> wrote:
> Hi
>
> in melodic this is a simple variance ratio test (using the spatio-temporal model with and without a component). Once calcualted these % variances get re-normalised (divided by their sum) due to the fact that non-orthogonality means that potentially a certain bit of variance can be explained mutliple times. For the 'uniquely explained' numbers the same thing is done, but partialling out all other N-1 components first.
> hth
> Christian
>
>
>
> On 5 Aug 2010, at 05:36, Jack Grinband wrote:
>
>> Hi Christian,
>> So how does one calculate the % variance explained?
>> thanks,
>>
>> jack
>
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