For retinotopy, I find it convenient to use the sphere surface.  It does not require a cut down the middle of V1 and it is flat enough to easily draw ROIs.  Also, in my experience, the patch flattening algorithm often produces poor results (e.g. large distortions, twisting).

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Date: Thu, 28 Apr 2011 23:03:50 -0400
From: liu.yang76@gmail.com
To: freesurfer@nmr.mgh.harvard.edu
Subject: [Freesurfer] distortion of flat map

Hi surfers,

I am working on generating surface ROIs from the retinotopy surface.
We cut the occipital lobe and draw paths on the flattened map to create labels. However, I found that there are distortions on the flat map that cause large errors when drawing these paths. I attached two pictures. The path_example2_dots.jpg are the dots that I selected to draw a path. Basically it is the method we use to demarcate the boundaries of visual areas.
 And the path_example2_line.jpg are the line that is supposed to connect the dots and to be the correct boundary.
Notice the dots and the line do not overlap!
so when I draw a line on the flat map, Freesurfer actually doesn't draw the line I want it to be.

Has anyone met this problem before? Is there a better solution to create surface ROIs? Drawing the boundary on inflated surface?

Yang

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