help > Threshold on the connectivity matrix
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Sep 2, 2013  10:09 AM | David Coynel
Threshold on the connectivity matrix
Hi, and thanks for this nice toolbox.

I'm working with tractography data from FSL's probtrackx. I usually apply a low threshold to get rid of spurious connections, based on the group-average connectivity matrix.

In the paper describing NBS, you propose to work directly with raw data in order to avoid systematic sparsity differences. In my case, some NBS networks could get significant even though they mainly consist of connections that I would normally not consider, as they are quite unlikely to be true.

What strategy would you advice ?

Thanks,
David
Sep 2, 2013  09:09 PM | Andrew Zalesky
RE: Threshold on the connectivity matrix
Dear David,

Applying a threshold to remove spurious connections may be useful. To omit a connection from consideration in statistical testing when using the NBS simply set that connection to zero in every connectivity matrix. Any connection with a value of zero for every subject will be automatically excluded from statistical testing.

I hope that helps.

Andrew

Originally posted by David Coynel:
Hi, and thanks for this nice toolbox.

I'm working with tractography data from FSL's probtrackx. I usually apply a low threshold to get rid of spurious connections, based on the group-average connectivity matrix.

In the paper describing NBS, you propose to work directly with raw data in order to avoid systematic sparsity differences. In my case, some NBS networks could get significant even though they mainly consist of connections that I would normally not consider, as they are quite unlikely to be true.

What strategy would you advice ?

Thanks,
David
Sep 3, 2013  06:09 AM | David Coynel
RE: Threshold on the connectivity matrix
Great, thank you Andrew.