Hi - there are many factors that affect overall scaling - more below:
> On 10 Apr 2015, at 14:22, Nomi, Jason <jxn...@miami.edu> wrote: > > Dear Experts, > > I have noticed that the time-series for individual subjects from the dual > regression output in the parcellated connectome (100 comp ICA) has a much > larger range than I am used to seeing. > > The range for time series values are approximately -800 to 800 while dual > regression outputs that I have conducted myself are usually around -5 to 5. > > I also notice that I can set the threshold much higher for the independent > components when isolating activation compared to dual regression analyses > that I have done myself. This "cleans up" the component representation > substantially. > > My questions are: > > 1) Is there a particular reason for this large increase in ranges? > In this case most likely because we set the max of the group maps used in dualreg stage 1 to be 1. This causes output timeseries to have larger scaling - but the overall scaling is arbitrary anyway. > > 2) Does the larger threshold for component activation have any influence on > the time series that is being produced? Does the time series from the dual > regression output only represent the areas from the independent component > with the most intense activation? I would like to ensure that my > presentation of component images using a much higher threshold is actually > representative of the time series that I am analyzing. > Do you mean the group-ICA spatial maps or maps output by diualreg stage 2? The group-ICA maps have high peaks (compared with the background scaling) for a couple of reasons: a) because there are so many subjects being combined that the ICA components are strong, and b) the group-PCA reduction has removed a lot of unstructured noise before the PCA+ICA step. But despite the maps having strong "CNR", they are still valid maps. Cheers, Steve. > > Thanks! > > Jason > > > > _______________________________________________ > HCP-Users mailing list > HCP-Users@humanconnectome.org > http://lists.humanconnectome.org/mailman/listinfo/hcp-users --------------------------------------------------------------------------- Stephen M. Smith, Professor of Biomedical Engineering Associate Director, Oxford University FMRIB Centre FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) st...@fmrib.ox.ac.uk http://www.fmrib.ox.ac.uk/~steve <http://www.fmrib.ox.ac.uk/~steve> --------------------------------------------------------------------------- Stop the cultural destruction of Tibet <http://smithinks.net/> _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users
