Hi Freesurfers,

I'm running a brain stimulation (TMS) study and wish to stimulate points on the pial surface that correspond most closely to known Talairach points (from fMRI studies). I'm wondering the best way to find these points using the beautiful Freesurfer cortical reconstructions. I've extracted pial surfaces for 44 brains using recon-all. I'd like to be able to create a label on the point of the pial surface that corresponds most closely to the Talairach point.

I've tried creating a label on the inflated surface and dilating it until it becomes visible on the pial surface. But this method highlights adjacent parts of cortex rather than those closest to the Talairach point.

I've also tried importing the pial surface into Matlab using mris_display, increasing the transparency of the pial surface, and superimposing the Talaraich points using a scatterplot...

(Incidentally, I've been unable to figure out how to transform from Talaraich space to Freesurfer RAS space. I've tried multiplying TT' x tal, where TT = the Talairach transform matrix from talairach.xfm and tal = the Talairach point. But the points are way off where they should be. What am I doing wrong? In the meantime I've solved this problem by working out the Talairach point within Freesurfer)...

Using Matlab to display the pial surface and superimposing the scatterplots is producing the best results so far, but it can be very difficult to recognise different parts on the transparent pial surface and this procedure is far from automated.

Any ideas?

Thanks so much for your time,

David Painter, PhD

Queensland Brain Institute University of Queensland Australia