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Hi Matt, 1) I have been running group level ICA using MELODIC on a dataset of 130 > subjects with a relatively high number of components (d > 60). > but I see a lot of quite similar spatial maps in each run. For example, > each time I get 3 or 4 components as primary visual network. > or 2 or 3 default mode networks. Is it expected to have such multiple > similar maps? or could it be something that I have missed to set in my > configurations? > Potentially, yes. If you have enabled automatic dimensionality estimation, then the number of components you will get is entirely data driven. It is much more common to specify the number of components you want out of a group ICA, depending on the type of analysis you are planning to do. > 2) Are such components still considered to be independent from each other? > Yes, the spatial maps are independent. This does not necessarily mean that they are non-overlapping, nor does it mean that they are not functionally/temporally related. > 3) How MELODIC calculates the automatic number of components to be > discovered, when we do not specify the model order? MELODIC uses an initial PCA to find a threshold above which all components are explaining more than gaussian noise. It then uses this number of PCA components in the ICA decomposition. Paul On Sat, 30 May 2020 at 18:44, Matt <[log in to unmask]> wrote: > Hello, > > 1) I have been running group level ICA using MELODIC on a dataset of 130 > subjects with a relatively high number of components (d > 60). > but I see a lot of quite similar spatial maps in each run. For example, > each time I get 3 or 4 components as primary visual network. > or 2 or 3 default mode networks. Is it expected to have such multiple > similar maps? or could it be something that I have missed to set in my > configurations? > > 2) Are such components still considered to be independent from each other? > > 3) How MELODIC calculates the automatic number of components to be > discovered, when we do not specify the model order? > > Thank you very much, > Matt > > ######################################################################## > > To unsubscribe from the FSL list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1 > > This message was issued to members of www.jiscmail.ac.uk/FSL, a mailing > list hosted by www.jiscmail.ac.uk, terms & conditions are available at > https://www.jiscmail.ac.uk/policyandsecurity/ > ######################################################################## To unsubscribe from the FSL list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1 This message was issued to members of www.jiscmail.ac.uk/FSL, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/