Hi Bruce,
I chose a random subject from the ADNI dataset and computed the mean and
variance for the left and right hemispheres separately. It looks like the mean
is close to 0, however the variance is not 1. Do you think it is possible that
the surfaces are demeaned, but the units are still something meaningful (i.e.
not unitless)?
sulc = read.table('rh.sulc.asc', header=FALSE, col.names=c('v', 'x', 'y', 'z',
'sulc'))
> mean(sulc$sulc)
[1] -1.236923e-08
> var(sulc$sulc)
[1] 0.3276958
> quantile(sulc$sulc)
0% 25% 50% 75% 100%
-1.72503 -0.42128 -0.03963 0.40072 1.80980
Thanks again,
Simon
Hi Simon
they are originally mm, but I believe we z-score normalize them so that
the sulc file is 0 mean and unit variance.
cheers
Bruce
On Wed, 21 Oct 2015, Simon
Vandekar wrote:
> Dear Freesurfer experts,
>
> I am reading the manuscript "Cortical Surface-Based Analysis II: Inflation,
> Flattening, and a Surface-Based Coordinate System" by Fischl, Sereno, and
> Dale (1999) where the estimation of sulcal depth is described on page 199,
> however from the description I am still unsure of the exact units of sulcal
> depth.
> Are the units for sulcal depth in mm or are they in arbitrary units?
>
> Thanks in advance,
> Simon
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>
>
>
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