Hi Longchuan,
It would be sufficient to use the cortical mask as a target only, to get the
result you desire.
Tracts are not necessarily the same when tracked in the opposite direction.
For one thing, your cortical mask is probably much larger than the cerebral
peduncle mask, and thus many more samples will be sent out when you use it
as the seed. Also, tracts may split off and depending on how you approach
the split you might take one or both of the branches (approaching from a
branch you might only continue into the portion before the branch, whereas
if you approached from that side, you might take both branches). I
typically use a symmetric method when tracking white matter pathways from
white matter ROIs.
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Longchuan Li
Sent: Wednesday, June 18, 2008 4:18 PM
To: [log in to unmask]
Subject: [FSL] tractography regarding cortical mask
Hi, FSL users
I drew a seed mask on the cerebral peduncle and a cortical mask on the
precentral gyrus to see how the precentral pyramidal tracts go from
brainstem to primary motor area. I want to show only the tracts that reach
my cortical masks. Now I am using the cortical mask as the waypoint mask as
well as target mask to show only those tracts that reach the cortical mask.
My questions are:
1) Is this the correct way to do?
2) Is there any difference in interpreting the result as compared to the
case when I use cortical mask as the seed mask and cerebral peduncle mask as
the cortical mask?
Thank you in advance
Longchuan
----- Original Message -----
From: "Christina Hugenschmidt" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, June 18, 2008 6:51 AM
Subject: [FSL] TICA on resting state
> Hi all (and Christian in particular),
>
> I am interested in running a TICA analysis comparing resting state and
> also video watching between two groups. From reading the posts and
> information on the FSL website, I think I should be using the same
> methodology described in the Damoiseaux 2007 Cerebral Cortex paper, where
> the data is fourier transformed prior to running the TICA analysis. I was
> wondering if you could tell me the process used to transform the data
> prior to running the TICA?
>
> I would also like to be sure that I understand exactly what is being
> compared between groups in this analysis. When the data is transformed,
> does this mean there is power spectrum information in each voxel? Are
> networks then identified by shared power spectra? And when group
> differences are evaluated in contrasts, a significant difference means
> that the spatial maps identified within the power spectrum for that
> component are different between groups?
>
> Thanks for any insights you can offer,
>
> Christina
>
>
>
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