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Dear Melodic experts,
I am trying to calculate indices of subject’s connectivity for subsequent quantitative
genetic analysis as suggested in Glahn et al., (2010) PNAS paper. The authors used Melodic toolbox to extract this value as follow: “Specifically, the individual (3D) subject-specific maps of the default mode network were collected into a single 4D data set, and the first principal Eigenvector representing the subject’s connectivity was calculated within a study-specific default-mode mask...." My question is whether such an index of connectivity was measure as the eigenvalue of the covariance matrix, something like:
[subject_loadings, ~] = eigs(cov(ics2), 1); % IC2 is a subject-specific SM for a specific component
I would appreciate if someone clarify on this issue or at least briefly describe how to extract such indices from Subject-specific SM? Does it matter how the components have been scalled(e.g. Z-score vs. percent signal changes)?
Thanks a lot!
Kami |