Program for z-transformation?

Submitted by yanka on Sat, 11/30/2013 - 00:13

Hello everybody!

We need some help concerning our the analysation of our resting-state fmri-data.

We already did the preprocessing via SPM8.

Now we would like to enter the smoothed data into ICA using GIFT. In a paper of Sorg et. al (2007) we read, that before doing this the following step has to be done:

 

„Before they were entered into the ICA, a voxel-wise transformation was applied on the time course data yijk(t), ŷijk(t) = [yijk(t) − <yijk>/σijk (for each voxel: t, time; i, j, k, three directions in space; <yijk>, mean; σijk standard deviation). This procedure removed any systematic, between-group differences with respect to BOLD amplitudes from the four-dimensional data set ŷijk(t). Sensitivity for variance correlation was thereby rendered independently of variance magnitude.“

 

Despite intensive research, we could not find any programme doing this z-transformation. It is included in GIFT or SPM and we simply did not find this function oder do we have to implement anything else?

Kind regards,

Janina

Submitted by ZHANG_RESTadmin on Mon, 12/02/2013 - 22:16

 this is voxel-wise z transformation, which is included in GIFT, however, I don't know if you can borrow GIFT's function because I am not sure if it is an independent function in GIFT.

So I recommand you write a script to do this.

Simply you can use REST's functions:

Here is the psudo-code you may interested with. In order to make them work, you need a little revision.

for subjectID = 1: numSubject
[data] = rest_to4d(DataDir_for_subjectID);
data = reshape(data,[], numTimePoints);
data = (data-mean(data))/std(data);
data = reshape(data, dimX,dimY,dimZ,numTimePoints);
rest_Write4DNIfTI
end 


Submitted by zhoujun on Mon, 12/09/2013 - 16:31

老师您好：
      我看到这个帖子，如果我得出来的数据是txt格式的，我该如何Z变化呢？有程序解决吗？

谢谢
      

Submitted by ZHANG_RESTadmin on Tue, 12/10/2013 - 00:48

 问题不在格式是什么，而是你想要做z变化的数据是什么数据。

如果是相关系数，用fisher z变换。
如果是t值，用spm_t2z
如果是其他值比如量表得分，用减均值除方差方式近似得到z值。