Hi Sean,
I presume you want a map which shows the visual areas V1, V2, V3 etc. in
Template space.
You have to be very careful doing this, and in fact it is not clear that is an
appropriate thing to do.
Many anatomical studies have shown that major visual cortex landmarks, such
as the calcarine sulcus, vary greatly in length, position and orientation in
Talairach space.
In addition, the boundaries between visual areas are highly variable and are
unlikely to be matched in any template space that is defined by non-linear
"warping" of the gross shape of the brain. The boundaries do not always match
any well defined sulcul landmarks either, so averaging based on sulcul anatomy
will probably also fail.
I can tell you that about 5 years ago there was a paper that showed Talairach
coordinates for retinotopically mapped visual areas. It is a really nice paper
by DeYoe et al. (Proc Natl Acad Sci U S A 1996 Mar 19;93(6):2382-6). I
actually used these Talairach maps to try and identify which visual area my
activation was in, and it seemed to be in V2 dorsal. However, later
retinotopic mapping for each of the individuals in my study revealed that the
activation was actually in V3A, so you have to be really careful doing this
kind of thing.
If you look at Tootell et al's paper on V3A (J Neurosci 1997 Sep
15;17(18):7060-78), you can see a 3D-rendering of V3A (their Figure 8),
delineated using retinotopic mapping, for several subjects. It gives a good
indication of how variable these areas are in 3D space.
It looks like, at least for now, you have to do retinotopic mapping for each
of your subjects and then do single subject analyses.
Unless someone has calculated a probabilistic map of V1, V2, V3, V4 etc.? You
never know...
All the best,
Krish
Sean Colloby wrote:
> Dear SPM'ers,
>
> I wonder if anaybody can help. I am looking for a ROI map in
> Talairach space of the active visual area (cortex) of the brain of which
> I can overlay together with my SPM{t} map onto a the structural T1 image.
>
> As in my analysis I see occipital changes, and would like to see them in
> relation
> to the visual cortex regions. As anybody got such an image file in Analyze
> or can somebody suggest to me how I could obtain or indeed create one.
>
> I hope I've made some sense.
>
> Cheers
>
> Sean Colloby
> Research Associate
> Wolfson Research Centre
> Newcastle General Hospital
--
Dr Krish D Singh
Department of Vision Sciences
Aston University
Aston triangle
Birmingham
B4 7ET
ENGLAND
tel: +44 (0)121 359 3611 ext 5176/5190
fax: +44 (0)121-333 4220
email: [log in to unmask]
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