Darren Weber wrote: > > Hi Doug et al, > > from looking at the help on mris_surfglm it appears that vertices in the > analyses are not as dense as those from the subject surfaces.
It should be quite comparable, and the ico/average7 has 163842 vertices, which is often more then individual surfaces. > I'm guessing > that using the ico surface with 7 iterations of refinement (lots of > vertices!), you then locate the nearest vertex in each subject for each ico > vertex. So, the GLM analyses for any given ico vertex use data from > different vertex numbers across subjects - are these vertex indices and ico > vertex correspondence available as an output option or are they stored in a > temp file or something? Say, for each vertex number of ico, a row vector of > subject vertex indices, in the order they are input to mris_surfglm. You've basically got the method right. For each subject, I use the ?h.sphere.reg. For each vertex in average7/ico7, I find the vertex in ?h.sphere.reg which is closest. I don't have a way to save the mapping, however. I'll keep that in mind for the next iteration. > Also, if the above assumption is correct, the implication may be that some > slight variations in registration (alignment accuracy might vary to within > 1 - 10 vertices, perhaps) could have an impact on the results? Is there any > local vertex neighbourhood averaging of thickness values when extracting the > individual subject values for the GLM? Yes, you can specify smoothing on the surface using the the --nsmooth option. This does iterative nearest-neighbor smoothing before resampling to the sphere. doug > Cheers, Darren > > ----- Original Message ----- > From: "Doug Greve" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Friday, October 11, 2002 2:13 AM > Subject: Re: mris_surfglm > > > > > Hi Darren, > > > > the ico and average7 are about the same computationally. However, it is > > more convenient to use average7 it has a surface that you can directly > > render the results on. With ico, you'd still have to run mri_surf2surf > > to convert it to another surface. > > > > I'm not sure what you're trying to do in terms of the surface > > registration... > > > > doug > > > > > > Darren Weber wrote: > > > > > > Dear Doug et al, > > > > > > surfglm looks good. I have processed 10 controls and 8 patients such > that > > > each surface contains a whole cortical surface, without the usual split > > > through the corpus callosum. How would I use the surface registration > > > process? Should I use 'ico' as the average or can I use one of the > > > subjects? > > > > > > Take care, Darren > > > > > > -- > > > Darren Weber, PhD Student > > > Cognitive Neuroscience, School of Psychology > > > Flinders University of SA, GPO Box 2100, Adelaide, SA 5001, Aust. > > > Ph: (61 8) 8201 3889, Fax: (61 8) 8201 3877 > > > http://203.3.164.46/~dlw/homepages/index.html > > > > -- > > Douglas N. Greve, Ph.D. > > MGH-NMR Center > > [EMAIL PROTECTED] > > Phone Number: 617-724-2358 > > Fax: 617-726-7422 > > -- Douglas N. Greve, Ph.D. MGH-NMR Center [EMAIL PROTECTED] Phone Number: 617-724-2358 Fax: 617-726-7422
