Hi Mishkin,

basically, yes. The spherical mapping energy function is pretty much a subset of the spherical registration one (with the folding geometry correlation term taken out).

Inflation = spring term + distance term spherical mapping = distance term + topology term (oriented area) spherical registration = distance term + topology term + correlation term

the other difference is that the spherical mapping uses long range (1-2cm) distances, while the others are all local distances (nbrs). The registration also sometimes includes a small area preservation term. cheers, Bruce

On Mon, 25 Feb 2008, Mishkin Derakhshan wrote:

Hi, After reading the wiki and the references on the wiki, specifically [1] and [2], I'm still a little confused about how the inflation and registration to a sphere occurs. ie. what energy functions are being minimized at each step.

I think it is a 3 step process, where

1. Surfaces are inflated by minimizing the energy function Js. This

creates ?h.inflated. Js = 1/2V (EE ||xi-xn||^2) + lambda-d*Jd (8) in [1]

2. The inflated surfaces are then projected to a sphere by minimizing

the energy function J. This creates ?h.sphere J = ???

3. The sphere is registered to the average by minimizing the energy

function J. This creates ?h.sphere.reg. J = Jp + lambda-d*Jd + lambda-a*Ja (5) in [2]

Is there a step I am missing? Are my energy functions correct?

thanks, mishkin

[1] Cortical Surface-Based Analysis II: Inflation, Flattening, and a Surface-Based Coordinate System, Fischl, B., Sereno, M.I., Dale, A.M., (1999). NeuroImage, 9(2):195-207.

[2] High-resolution inter-subject averaging and a coordinate system for the cortical surface, Fischl, B., Sereno, M.I., Tootell, R.B.H., and Dale, A.M., (1999). Human Brain Mapping, 8:272-284(1999). _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer