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. 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.
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?
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
