Many thanks for that. Am I correct in thinking that the Gauss_Bonnet scheme is given by the "--discrete" option in mris_curvature_stats, while the latter option is given by the "--continuous" flag?

L

On Fri, Feb 26, 2010 at 1:46 PM, Bruce Fischl fischl@nmr.mgh.harvard.eduwrote:

Hi Lisa,

we actually provide a discrete estimate using Gauss-Bonnet (Rudolph can give you the details), and a slightly larger-scale estimate by fitting a quadratic patch to each neighborhood (5mm on a side I think). The curvature then comes from the Hessian of the height function of that patch.

cheers, Bruce

On Fri, 26 Feb 2010, Lisa Ronan wrote:

Hi All

...

I wonder could you tell me how Gaussian curvature values are computed at a vertex, i.e. Gauss_Bonnet scheme? Is there any way to vary the neighborhood over which the vertex curvature values are computed?

Thanks for your help,

Lisa Ronan

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Research Associate Brain Mapping Unit Sir William Hardy Building Department of Psychiatry University of Cambridge

Yes -- that's exactly right. The '--discrete' is also the default so doesn't need to be specified. The '--continuous' uses the old curvature engine.

You will notice that each engine option results in slightly different curvature values.

Sent via BlackBerry from T-Mobile

-----Original Message----- From: Lisa Ronan lisa.ronan@gmail.com Date: Fri, 26 Feb 2010 13:51:27 To: Bruce Fischlfischl@nmr.mgh.harvard.edu Cc: freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Gaussian Curvature Calculation

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