Hi Stan, the VBM results may be picking up changes in GM volume. These volume changes may be driven by differences in surface area and would not necessarily show up in a thickness analysis. Maybe the surface area is increasing with performance but the thickness is decreasing. You can do a surface-based analysis of surface area and/or volume (this is similar to a VBM analysis but on the surface). You can do this by specifying --meas area or --meas volume to mris_preproc. Make sure you have the mris_preproc patch (or are using 5.2).
doug On 02/05/2013 09:54 AM, Bruce Fischl wrote: > Hi Stan > > we have found positive correlations between performance (in this case > CVLT) and thickness, so it is certainly possible. And negative > correlations aren't necssarily false - you could certainly imagine > that successful pruning for example could help performance. Have you > visually inspected the surfaces for accuracy? > > cheers > Bruce > > > On Tue, 5 Feb 2013, Berg, S.F. van den wrote: > >> >> >> Dear Freesurfer experts, >> >> >> >> We investigated the relation between cortical thickness and >> performance on several cognitive tasks within a large group of >> Parkinson?s disease patients, but are slightly puzzled by the >> results. We obtained several, both in the vertex-wise analysis >> in qdec and in the SPSS analysis in the a-priori parcelated areas, >> negative correlations (i.e. better performance relates >> to a thinner cortical area) for all our neuropsychological tasks. >> These negative correlations were unexpected and we are >> having a hard time interpreting them. After correcting for multiple >> comparisons, all effects failed to reach the >> statistical threshold, rendering no results at all. When we compared >> our patient group on a structural level with healthy >> controls, we did find expected results that made sense. >> >> We also ran the exact same analyses (same group, same data) in VBM >> and there found several positive task-related >> correlations in expected areas. >> >> We noticed that in previous literature almost no studies investigated >> the relation between cortical thickness and >> cognitive task-performance. This made us wonder whether Freesurfer is >> suited for these correlation-based analyses, or is >> it better to be used in between group analyses? And do you have any >> idea on how to explain our negative correlations? Is >> it possible we might have done something wrong? >> >> >> >> Many thanks, >> >> >> >> Stan >> >> >> > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
